Notes on Metal Boat Building Methods

Steel and aluminum boatbuilding. See: "Boatbuilding Methods", in left-hand column of the Home page, for information about alloys.

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SunFun
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Re: Notes on Metal Boat Building Methods

Postby SunFun » Wed Dec 09, 2015 5:48 pm

Kevin,
As the others have stated, your post are VERY interesting and will be of great value to anyone building a metal boat. I am hoping someday to make a wood boat, and will most likely never build an Aluminum boat, but will continue to follow this thread and any posts you make.
As an engineer who has worked in fab shops in the past, I've always admired the work of the craftsmen in the shop and knew that although my brain knew how to do there job, my hands would never be able to match their skills.
Keep it up and thanks for sharing your knowledge.

Scott

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Postby Kevin Morin » Wed Dec 09, 2015 8:54 pm

Gentlemen, thank you all for the kind words and taking time to read the thread, I hope to make the information clear and to have something that could add to the skills or improve the techniques of welded aluminum boat builders; and especially if there is a Glen-L Forum reader that is considering buying the plans and doing the layout and cutting instead of buying the NC packages from Specmar where a great deal of time is saved by having the layout, cutting and fairing done- ready to assemble.

Truthfully, buying the NC cut packages, (then) using a Davis Jig to conserve build time and improve welds could be the basis for a small boat business in some areas of the country, the designs are proven, the fits are "done" a little edge clean up and you'd be tacked ready to weld in a day or two!

However, for those who'd like to do it all themselves, I'll continue with this thread. Next I'll keep moving on some tool posts and begin to make some generalizations about groups or types of weld joints and how they can be easily prepared resulting in close fits, and uniform welds.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Postby Kevin Morin » Fri Dec 11, 2015 12:24 am

Many joints in a WAB (welded aluminum boat) are made between pieces of Al that is too thick to weld in a single pass weld. So to improve the weld joint smaller welds are put on both sides. This usually begins to be common practice at 1/4"(0.250") thick but is not rare on 3/16"(0.187") thickness either. There are instances where even 1/8" (0.125") sheet is double side welded and all these joints can occur in flat bars, or in sheets.

The techniques used here, can be adapted to the thickness of material that is being welded, but test welds are needed to determine what angle of chamfer or bevel is needed for your welding skills, welding adjustments, wire size, and weld type.

I'd like this post to be seen as a Rule of Thumb for a the introduction of a technique and not mis-understood as the only way to accomplish this weld joint preparation. Because so many joints require bevels, and because those bevels are NOT always the same depth or angle: it's important to note that you'll need to test weld your own sample joints to make sure they're adequate for your use. That means the angles shown here are for illustration not for all weld joints.

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If you have a uniform mark, made with a permanent ink marker on clean aluminum you can see how much of the edge to remove when you make a bevel on the edge of that bar or plate. Here a cut off pasted in hand is holding a marker with the tip of the marker against the middle finger that is also held against the metal's edge.

By holding the pen firmly but not hard to the metal, and dragging; a very even, uniform, and clearly visilble 'cut line' can be made on both the top and the end/edge of the plate/bar.

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another perspective view of how to hold the pen/marker to draw a 'take off' line. "Take the Black" is the term used. I made the marker green because the picture is more or less black and white. The Green Area is the top of the what is removed. I find I hold the pen with more index finger than I show here- but this was a cut and paste hand so I could make the sketch easier.

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What is it that we want to remove? We need to bevel the edge to make #1 a larger root face for the weld; #2 less metal at the edge of the plate to melt in fusion by the weld; #3 Mechanical penetration by removing parent metal (green or yellow edges) so the weld can reach deeper into the plate/sheet with less amperage.

This sketch (above) shows the two marked areas (by four strokes with the marker held as shown) and the left side shows the edge with the bevel cut.

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Above, the two bars in this case, are both beveled for a butt joint double sided weld. (The edges are shown yellow on one side and green on the other to reduce the countless shades of gray of the aluminum bars.)

Typically this type of joint would have clamping, stiffeners, and or other support to help keep the two pieces flat to one another while the two welds were added.

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The sketch above shows the weld (beginning or ending) in cross section as one side first. This image includes a very key but small detail seen in the next image below.

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Here the weld is zoomed in closer so we can see the main features that you'd need to be sure occurred in your own welds. First the weld in this case on a 1/4" bar is only about 1/8 (plus very low crown/top/bulge above) so each side is a single pass weld. The second item is that the first weld has a bulge or penetration into the unwelded side's V beveled cut out.

This small penetration is key to your understanding of the bevel you cut compared to the amperage and wire speed of the weld (MIG Al weld). If the weld is not penetrating in this rounded bulge line? #1 the weld is too cold or #2 the bevel is to narrow and needs to be 'widened' or the angle of the bevel has to become greater so the beveled 'tip' of the bar is sharper. A sharper cut, greated bevel angle takes less amperage to melt/fuse that thinner piece of metal.

What does this indicate? That bevels cannot all be exactly assigned until the welder's settings, wire size, amperage and travel are tested on that particular bevel. Once a builder has performed several dozen tests, he will be able to find his correct version of the bevel angle, the bevel 'cut back' (shown above with a marker in green) and that will correlate with the welding settings (keep a notebook or go nutz!) that were used to make successful double sided butt joints.

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Above are two 1/4" x 4" flat bars like we might see at a chine ( the miter joint is NOT always used!!!!) Let's call the lower right bar section the " bottom frame bar"that lays on the bottom of the hull from the chine to the keel. That makes the tip of the two bars the chine and the left hand bar is the topsides (side frame) element of our hypothetical transverse frame.

The first job is to put the template (if you have one) onto some plywood, or some aluminum and mark the locations of outline of the frame. Now these two bars are called for as the two port side frame pieces, the keel would be to the right out of sight in our sketch. The sheer up the topsides is out of frame to the upper left and we've just cut the two bars so the joint between them allows both bars to lay on the work template so each frame piece fits the outline of that frame.

But the weld is not ready to put in- because we don't usually do surface welds with WAB welds.

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recalling the first few sketches above, we can see how to mark the metal that needs to be removed from the miter cut ends of these bars- the areas here in green and yellow. We'd use the marker technique above but.. a combo square and marker will work as well, it just takes longer and the marker's ink can 'run' under the blade of the combination square and have to acetone wiped off and remarked.

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Above are three views of the joint with a cut bevel and two extra bars. These bars are 'run on' and 'run off' bars so the MIG weld can begin and end off the final joint's weld zone.

A the weld tacks are not shown, but one tack would be at each end of the weld bevel, the tacks would be dressed down to the minimum remaining metal to hold the two bars for final welding. The rotary carbide burr or the meat axe are tools that could be used to 'dress the tacks' and reduce them to avoid cold spots or excessive contamination in the final weld's root near the tacks (not shown.)

At the green circle (start) the weld is initiated OFF the main bars and then welded to the Red (stop) OFF the main bars. Both the start and stop are performed off the main part to welded. The Run Off Run On bars are simple snapped off the part when the weld's cool, the welds are done both sides one after the other as soon as the part can be turned, while it is hot from the first weld.

The best way to 'finish' the broken weld bead on the two edges if with a TIG torch but it is not needed, the welds will remain full strength without TIG floating but it looks nicer to TIG float.

The outside corner of our hypothetical frame's will eventually be cut to a 'mouse hole' or a small radius cut out so the frame's bars do not block the chine weld when the two panels are joined in the hull welding sequence.

Summary, this post was about beveling before welding material that will have double sided welds. The marking and set up was discussed but not the various methods of cutting those bevels. Next we'll take a look at various ways to cut bevels, make edge preparations of these types of joints.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Postby Kevin Morin » Mon Dec 14, 2015 2:41 pm

Hand held, power driven, metal working tool use is critical because of several conditions in the WAB building process; we're focused on the preparation of weld joints and will continue here with more information about using tools for that purpose.

Weld joints' shape, uniform edges, angles and depth of preparation all contribute to weld shape, size and uniformity and that all contributes to distortion or smooth surfaces, attractive welds or "homely welds", and could lead to poor structural performance. Broken welds sometimes happen from weld preparation being inadequate - and weld prep done poorly can be the result of poor tool use.

This post is an attempt to give the basics about a couple of power tools that seem misunderstood by some aluminum workers and is my version of how to use the tools "correctly" (IMO). Of course, if you've used these tools for years you may want to skip this post as the ideas may be lots of discussion for something you already know! ??

Cutting tools or blade tools, especially carbide blade power tools are fairly easy to see as ‘cutting’ compared to a sanding disk or hard wheel that grinds aluminum. But the sanding, grinding and buffing of aluminum is based on cutting action too. The cutting action of this group of tools is done by small sharp particles of one or another ‘abrasive’ that are moved at high speed over the aluminum surface to remove a single tiny chip or spec of aluminum at a time. By combining these abrasive particles into a spinning disk the cumulative action of countless small gouges of aluminum from these numerous tiny sharp edges acts to cut the aluminum.

http://www.thefabricator.com/article/fi ... d-aluminum article in the Fabricator summarizing aluminum grinding Reference link from the Fabricator Magazine that helps to compare processes.

We call these cutting actions grinding or sanding because they’re performed using those types of tools (grinders and sanders) and because the removal is usually at a much slower rate than carbide blade power tools’ cutting actions.

Probably the most often misused tool in the aluminum shop is the, motorized, hand held, portable grinder or circular sander. I think the reason this tool is often misused is the lack of technical training or explanation the tool is provided in our common discussion forums? I’ve worked with people who were so good with this tool is was a precision instrument in their hands and with others, equally experienced metal workers, who had no clue about best use of this tool. I hope to make some Rules of Thumb here, to explain where the hand held grinder motor is best used in WAB’s construction.

The tool gets called different names depending on what is mounted on the drive stud? If the wheel mounted on the drive stud is rigid the tool is usually referred to as a grinder but when that disk is changed for one that is softer or flexible it will most often be called a sander; same motor and power tool just different terms due the mounted cutting disk. When this tool has a 3M Scotchbrite ™ flexible, finer grit, fabric based sanding or buffing pad mounted, then the tool is called a ‘buffer’ and like-wise when a SS wire wheel is mounted is called a “power wire wheel” or just a “wire wheel”. To further confuse naming this tool; when wire wheels are used this is very commonly called ‘buffing’ the weld zone!

There above, are the four general categories of attachments for this rotary acting, hand held power tool; hard wheels for fastest removal of stock, sanding disks ranging from as coarse as hard wheels to as fine a polishing disks; buffing for the finer grits of sanding usually including the plastic fiber Scotchbrite ™ and including various types of cotton polishing disks; and SS wire wheels that should be confined to one or two types.

http://www.pferdusa.com/products/206a/206a03/index.html Link to Hard Wheel for aluminum use, there are many brands and types. What is key to selecting an aluminum hard wheel in is the next link: You don't want to use any product- no matter how it is labeled if this condition happens!!!

http://web.mit.edu/machineshop/Grinder/aluminum.html This link shows a pedestal mounted grinder motor with a (steel) hard wheel; it has been coated with melted aluminum because the grit is not rated (too hard not soft enough) to be used effectively on aluminum. IF ANY product, regardless of rating, purpose or use- loads up with aluminum as shown in this link- that tool has some problem- either it is not lubed or it is not rated or is simply inappropriate for aluminum.

http://www.amazon.com/Neiko-7-Inch-Alum ... ding+wheel Flap sanding disc, as a real product that works great for aluminum - I coat these disks with Pan Spray to allow them to last longer and to release any build up of aluminum coating the abrasive grit.

Lets look at some tool techniques that should be practiced by aluminum boat builders.

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The first sketch (above) shows the same grinder motor with a large size (7") wheel mounted. That wheel could be either a hard wheel, or a sander type. We expect most sander disks to be more flexible than a rigid hard wheel but that flexibility is relative, these sanding disks are made of different thicknesses and hardness so their flexibility differs.

In this image the three tools are positioned to bevel the edge and all three have a "Pink Zone" shown on the back as a reference to our discussion.

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Zooming in on the first or left most grinder's pad from the top of the motor, the Pink Zone is shown laying against the sheet edge and cutting a bevel. Its important to decide if the tool should be used as a plane or a chisel, in this first case we're using the tool as plane to take off an even angle, even lined, and even amount of the edge- to prepare an even bevel.

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This sketch from the front looking back to the operator, who is not shown, confirms the key technique to master with this tool as a plane. The disk, has to be kept flat to the edge or the bevel will "wave"- if the bevel is not uniform then any weld will have to vary in width, and contraction, and appearance... well- you can see the dominoes falling of a poor tool technique- misuse this tool on a weld bevel and the mess begins. On the other hand, if used correctly, this method of joint prep is reasonably fast and accurate- it all depends on this technique being used.

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However, above is a technique that needs to be discussed right along the use of the power disk as a plane; that is the use of the same tool as a chisel, or maybe a block plane. IN this image (above) the disk's edge is being used to cut the bevel , marked in green from previous posts, and the primary technique here is the need to pull all cutting strokes!

If you push and pull back and forth along a plate edge, that will almost always make the edge less even, more wavy or irregular. This technique of pulling the chisel mode for a bevel works because the tool is not going to dig in if pulled but it will try to dig in when pushed. Try it, work on technique, especially good to work with grinder edge techniques while practicing bench welding prior to the build -developing your tool skills and weld skill along side one another is great time savings in the full calendar of the project.

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The sketch above shows the last of the three 'modes' of use of the hard wheel or sanding tool mounted to a grinder motor. This is the pushed chisel mode where the tool's outer edge is used exclusively to gouge, trim or dig out for weld preparation OR for tack dressing instead of the carbide tools shown in previous posts.

The tip edge use will come in handy as long as you're aware of the need to see this as a third method and not to confuse it with the two previous methods shown? This takes practice too, otherwise too wide cuts and gouges end up leaving a poorly prepared joint- and as I'm harping in all these posts: poor prep will lead to poor welds, and that leads to all sorts of quality reductions in your boat.

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In this sketch above we're looking at two power planes, one inverted to see the groove in the base plate that the upright (left side tool image) have fitted to the square edge of aluminum plate/sheet. The groove is present in different sizes and numbers on different brands of tools; but all of them can be used to cut nice quick bevels on aluminum.

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Above, the power plane's base groove is moved all the way along the plate to be beveled and the edge of the rotary cutter is lined up with the corner of metal to be beveled off the parent metal.

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This sketch, of the zoomed-in cutting area, shows a detail of the bevel that will be taken off this aluminum plate, bar or sheet. The depth of cut is set by the same controls as the full width cuts, but they have to be adjusted (perhaps to the minimum depth?) for different tools being used on different thickness sheets. Testing cuts is the only way to be sure what will result, and using pan spray on the rotary cutter in the plane helps the chips to release from the edge and prolong the life of the cutter and end up with a cleaner cut. I recommend using the shop vac on these tools whenever possible- they almost all have vacuum hose attachment- and there's a good reason for those connections!.

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Earlier in this post we discussed power wire wheels mounted to a "grinder motor". Below I will show a link to a recommended TYPE of SS wire brush but here I'm trying to make the two primary uses clear. The correct type of brush cost is high, and they can be destroyed in a few seconds by improper use, so I'm providing a Rule of Thumb for preserving the life of an expensive power tool 'bit' and to reduce the work area hazards inherent in this type of tool.

The two wheels shown are symbols, drawing a fully pictorial model of the brushes in the link below was too much time when we can all look at a picture- so my wire wheels here may give a misunderstanding. The wire wheels in these images are place holders, not realistic images. The wires shown all radiate uniformly from the hub but the recommended type are twisted in bundles.

However the image above does show the wheels' direction of rotation is #1 to consider. The wheel used along an edge should stay on the edge fully and rotate so the tool is pulled away from the operator, the motor is not shown in either wheel above. Next, and most important for longer life of this sort of fragile wire wheel is to rotate OFF any metal edges when you're cleaning at 90 degrees to that edge.

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This sketch is the same as immediately above but zoomed to show the edge of the plate material and the cleaned areas wheels. In this close up, the wheel is running so the wires land on the surface and then bend and scrape OFF the plate. If they were run 180 deg's the edge of the sheet or bar or plate would act like a knife edge and cut the wires, and then entire wheel could be stripped of the flexible wires in seconds.

http://www.weilercorp.com/standard-twis ... wire-13113 the photo in this link shows much heavier wires than the listing below in the spec.s! the size is 0.014" wires and this shows the heavier wire- probably due to the cost to make each photo of every product? However this is the wheel type that does a good job of cleaning mill scale and oxide from aluminum WITHout gouging, cutting and smearing the surfaces while you work. But the wheel is somewhat fragile compared to the longer life of the thicker wires- but those wheels will make a mess of your weld prep.

Summary: this post was a review of why grinder motors might be called different names, what could be mounted on them and why, as well as some introduction to techniques for the grinder/sander in use on aluminum. Also we reviewed the hand held electric plane's very nice beveling feature and closed with notes on use a SS wire wheel on your grinder motor to remove mill scale or oxides just before welding.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

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gap998
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Re: Notes on Metal Boat Building Methods

Postby gap998 » Mon Dec 14, 2015 4:36 pm

You could pay hundreds of £s for a college course and get less education than this - well done that man!
Gary

Planning a whole fleet, but starting with a Zip...I think.

"Just when you think you've made something idiot-proof, someone builds a better idiot!"

crowsridge
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Re: Notes on Metal Boat Building Methods

Postby crowsridge » Wed Dec 16, 2015 9:29 pm

As others have said Kevin. The lack of response doesn't reflect the amount of value you are providing here. I have always been a wood worker and was shy about metal and scared of aluminum. After using your tips here and other posts, I can say "I LOVE ALUMINUM!" Unless its a Glen L full on mahogany boat, I probably wont build another wood boat.

I have always had to deal with "measure twice and cut once". I just dealt with it. And then there is always a joint to get just perfect. And if you mess up, you start over. If I mess up with aluminum? I just add new metal to it like it never happened. Magic! I'm making a pilot house for my sled. Some of the frames are (appear) bent. I planned the angle of lean for the windshield tubing posts, cut a vee at the right angle out of three sides using the fourth side as a hinge. Bevel the three cuts and weld it up and grind and sand it smooth. They look awesome! Like a factory extrusion. I set them up and tried to get them to break without success. After using your tips, I cut my welds open to check penetration. Awesome!

Anyway, Thanks for all the information. Its truly invaluable and makes the difference between getting a good end product or having a huge pile of scrap and an unfinished dream.

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Postby Kevin Morin » Wed Dec 16, 2015 10:28 pm

gap998, crowsridge, others who comment, thanks for the appreciative words, I'm always encouraged to keep posting when I see others find a use for the info.

I'm (fairly) sure the Forum readers know that Mr. Glen L Witt, our founder, is kind of the 'father of home built boats' as he provided a great design book, dozens of "How To" articles and books, and recently that has been joined by Mr. Ken Hankinson's catalog, (I think they were partners somewhere along their cruises in the past?) so the Glen L Forum is really THE place to be able to contribute to people more fully understanding what it will take to build these great designs.

I've built quite a few welded aluminum boats from 30" to 40' and along the way I've had to draw on my neighbors and friends to work in those builds. I found that the methods I'd figured out needed to be explained and trained to get results (finished boats) which would compete in our local fisheries- compete with Seattle built boats.

To do that, compete with newly trained guys, I learned to explain 'how to' with sketches, that usually converted a carpenter to a metal boat builder- task by task. Thankfully, 3D software came along and I can post images that are bit more refined than my magic marker sketches on sheet aluminum which were immediately wiped off with acetone while the work went ahead!

Thanks again for the comments, and the always kind welcome of Glen-L's Forum, moderators and administrator.

Some of my topics may seem trivial?? but I'll try to show why I consider these detailed technique discussions so important as we go along. Thanks for bearing with..

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Postby Kevin Morin » Thu Dec 17, 2015 5:46 pm

This post concentrates on marking aluminum for exact cuts and next we'll look at the actual cutting techniques I’ve found helpful too. The premise is: If the marking system is poor, the visibility to guide that cut will be less than a more exact system of marking with higher contrast to enhance visibility. More exact marking comes from a few basics of tool use including what to avoid when marking cut lines.

Contrasting colors provide our eyes better definition of a line than low contrast colors and that is the basic idea behind this work method. If you can provide a highly contrasting color scheme for your cut lines, and good line of site to the tools’ cutting edges, regardless of type, then the more accurate lines, can be followed by more consistently guided cutting tools; the result will be lines and curves cut to a smaller level or error. With fewer irregularities in straight cuts, and less fairing along curved cuts in aluminum work, overall labor to prepare to weld is reduced. Weld quality will be enhanced since the edges or materials placed edge to edge will have less varied gap, bevel, fillets to fill so more uniform welds will result.

The sketches in this section are very frustrated by the lack of photographic quality of the images. ( know I could stage some images in the shop, but... I'm trying to get to some fine details , well beyond my photographic skill set!) Generally, I’m drawing to express an idea, pictures being worth thousands of words(?) and in this case that applies with the one objection of not being able to show ‘shiny’ or chrome-like light reflection. I’ll mention this several times in the text, but still encourage you to try this method of work to prove to yourself how effective it can be. The images won't do quite the justice to the topic I'd like.

When we get to cutting entire 3,000$ sheets of metal, these techniques are needed to retain your investment but they apply to most cut lines so there will be lots of ways to practice, for example while you're practicing your welding making coupons.

Image
This first image (above) has a piece of aluminum being marked with a carpenter's square to a straight line and one pencil is shown in several positions along the line. The first few positions the pencil was kept evenly vertical, but as the line was drawn the pencil wavered back and forth in reference to the original position.

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Moving our point of view down, more inline with the square's edge on the aluminum; the pencil's top ends are more clearly leaning instead of staying in a line.

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I hope this very close in zoom of the pencils' tips on the aluminum (above) is clear to the reader? ONe good reason we didn't try this with a camera! The side of the cone of the tip of the pencil rides on the square in this image and that creates a lever that can result in marking error! It may seem a tiny error but as we'll see this small lack of technique can become a welding headache or lead to extra work fairing the cut edge.

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Above, the zoom level increases to show the waving line drawn by the pencil tip when the top of the pencil is leaned toward and then away from the square, this results in a line that is not square so the guide for your cut is not straight. There's plenty of variation in a normal saw cut in metal - we sure don't need to add to that error by marking a wavy line.

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Next image (above) introduces the need to have high visibility and that relies partially on contrast. A pencil line, a fine marker line, or ball point pen line (the ball point won't always draw on aluminum) are all narrow and not high color contrast to the metal's surface color regardless of the surface treatment. So, I recommend a wide, black marker line.

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The pair or 'Sharpie' markers here recall the potential problem with using any marking device with a straight edge, or batten when marking the refercence lines for the next step. Be careful to hold ink marker so the line drawn is next to the straight edge not waving like the previous images illustrate.

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Above is a close up of the wider marker tip that has been sliced with a razor to sharpen the edges so the background reference line in this marking system produces a fine edged ink strip. New markers may not need to be trimmed, but older ones tend to get softer, rounded and fuzzy and a little trimming with a razor will return them to service for a while longer.

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Almost done! Here is the key to high quality marking of aluminum for power tool cutting; using a black reference line to the side of a scribe cut line in the metal's surface. The cut line, or scribed line will reflect a high intensity work light back to your eyes while the cut proceeds. The scribe is a very fine line but the background reference line allows high contrast for the eye to track the main line of the cut while still focussing to this tiny line to guide the saw's blade edge (kerf edge). Note the scribe's angle to the straight edge is leaned back enough so the tip is at the junction of square/straight edge and the metal to be marked? That stops the scribe from cutting a wandering line.

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Last image in this series, zooms in to show the tools positions for the best results, and underneath the square on the edge of aluminum to be cut is the outline of the saw blades' kerf or material removed in the cut.

Summary:
If a line, curved or straight is not marked uniformly with a uniform tool position- most marking tools will draw a wavy line because of the lever formed by the tip and the layout tools' edge. Decent lines, fundamental to good metal boat work, can be drawn easily by paying close attention to how the marking tools are held and moved along the marking area.

The most visible line is one with a black ink background and a scribed or 'cut line' next to the ink's edge. The cut line, reflected in the work light offers the best guide for hand held power tool cutting aluminum as the shiny reflected cut's sides will illuminate the line best of any marking method.

By practicing these techniques as you prepare for a build they will become clear (if they're not now??) and by aiming very narrowly at the target; your errors will be smaller too. A cut line leaving the scribed line on the metal allows the Vixen file or subsequent sanding work to be guided to a very small measurement- that leads to better built boats.

Plenty more in this vein to explore,

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Postby Kevin Morin » Sat Dec 26, 2015 4:45 pm

IF you can’t see the cut line mark; if you can’t see the element of the cutting tool that is making a cut- the blade of whatever form; you can’t cut well enough to control the quality of the build.

If you can’t see the line and the blade while it progresses along the cut to make corrections, you’d best figure out how to have the parts cut by computer (numerically controlled “NC” cuts) because you’ll have corrupted the basic builders block: the fair line edges of all parts to your welded boat. IF the parts’ edges are not fair, sweet, accurately matched to the next part, then welding contraction, distortion from gapped fits will leave you with an extremely expensive pile of "used metal”!!

I show a 'worm gear skill saw' (term not brand) in these images and I show a red blade but wood cutting teeth... the previous links to suggested brands and models are not changed by providing these simplified images.

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The purpose of this image (above) is to discuss the two-hands-on-the-factory-handles problems with worm gear saws used in metal. The view is where neither the blade edge/teeth or the table guide is really helping make a 1/32" accurate cut. The blade's teeth are hidden by the blade cover and the table thickness and crude blade guide marker are not accurate from this point of view.

Note: on some saws I've removed some or all of the orange shaded areas to get better visibility- that is an extreme step but... if I was cutting several thousand dollars of metal- I wanted to see well enough to have the value or more when I was done!

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Not that you can easily see this view (above from the front of the tool down low to the metal being cut) of the saw when holding the handles for a cut (!) this image above shows what information a good saw requires of the sawyer. Clear vision of the blade and maybe a clear reference to the guide on the table's lead edge.

Image
Moving our point of view down toward the plate being saw but moving back behind the blade's leading edge... we can see the blade teeth as their lead inside edge comes up through the metal. This is a "Leave the Black" cut not a "Take the Black" cut; where the scribed line (not well illustrated above) is along the right side of the black reference mark, and the blade teeth exactly cut the right edge of the scribed line.

Image
Above is the common sense test for cut quality, when the saw is removed; is the scribed line at the edge of the cut? Is there a 'clean' line? Is there some part of the scribed line removed and some left? Is there some part of the black reference line removed and some left?

I recommend ignoring the table's saw blade guide mark- rely ONLY on the view of the teeth as they come through the metal and control the saw's movements between your hands with the left side "table handle" shown in previous posts.

But like any work technique, just make some cuts, and give your work the test shown in the last image above. If the lines are good, then your technique is working, if not... well that calls for some practice and consideration of another technique to improve your cuts.

I’m not using Glen-L’s Forum to advocate for these products- by brand or model. The links (below) are simply handy ‘look up’ examples of “Types” of products that are useful and will be mentioned in the text of these posts. Good quality welded aluminum boat building can be done best by builders who are shielded, insulated, covered and immune to hot chips, dust and flying particles, and other commonly occurring shop conditions when cutting and fitting aluminum prior to tacking and welding that metal into a boat. Nobody expects a builder to suffer injury just to build their boat- even though some builders ignore safety precautions and suffer avoidable injuries.

I rant about PPE because of the number of injuries I’ve experienced and seen alongside me building WAB’s for several decades. Please use caution, wisdom and forethought to protect yourself and those around you when working in aluminum; that way your enjoyment of your results are greater – for a longer time.

http://www.amazon.com/Mayhew-45050-Ligh ... ty+glasses

If you move your face down close to a skill saw cutting aluminum, or a jig saw or even a carbide burr, you will get sprayed with hot, sharp chips from the blade. I use safety glasses and need a magnifier built into them to see well enough to follow a scribed line along the black ink reference mark.

http://www.amazon.com/Safety-Works-6418 ... ace+shield
I use a face shield as well- the glasses are worn under this; one protects the eyes the other your handsome smile! Remember- you're smiling right into thousands of hot chips flying directly at your face!

http://www.amazon.com/Designers-Edge-L1 ... work+light
In order to see the scribed line shining on the metal background, I use a set of lights like these to stand in front of the work and shine back and down into the saw's cutting area, I use the light ahead of me shining back so I don't shadow the cut line. If you have a helper(?) then dragging these lights along with you as the cut progresses is a fine way to be of critical help as the cut progresses.
http://www.amazon.com/NOVUS-7100-Plasti ... vus+polish
I keep this set of polishes around to 'clean up' or 'defog' the scratches on #1 my welding hood lens covers. #2 my safety glasses, #3 the face shield clear covers #4 my magnifiers inside the welding hood, #5 anything plastic I need to 'buff up'.

This polish series will not allow all scratches to be ignored but will prolong the life of all these disposable plastic eye protection devices - it allows you to spend a few minutes reducing the scratching 'glare' or fog and stretching their life a bit. I think its worth having, you may not? PPE is only good if you can protect yourself while doing a quality job wearing it. IF vision is impaired from chips and dust being wiped off plastic- then the PPE might not be worn, or you'll have to buy all the time- expensive and perhaps wasteful?

http://www.amazon.com/Protection-Profes ... r+shooting
I use custom poured ear plugs and over them I wear a pair of phones like these. I have ringing in my ears from the years of saws I've run with inadequate protection.... I used 28 db foam plugs almost always.... but still damaged my hearing- won't you please consider much higher protection for your own ears? Let me make this mistake for all of us? All you have to do it take my word for it! Saving your hearing, wear protection!

I've concentrated on cutting aluminum sheet or plate with a skill saw as an introduction to cutting. There are other considerations to make, and next we'll see if we can explore why to choose which tool for these cuts?

As always, if the post provides errors, or they're not clear? please point out the location of the confusion and I'll be happy to take a shot at improving my explanations. And a short reminder; this is not the ONLY way to build quality welded aluminum boats.. BUT.... if you apply these techniques to your own work(?) at least until your skills become more practiced and experience based - your boat building metal work will be of higher quality than if you began searching for these techniques on your own. So we're exploring a foundation for your work, I'm not asserting these posts represetn the last word in metal working techniques.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

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Re: Notes on Metal Boat Building Methods

Postby slug » Sun Dec 27, 2015 6:10 am

Kevin; Just as some personal background, In the 90s my wife and I along with some help with a very good friend on the heavy stuff (hull, decks etc.) built a Brewer designed Kaiulani 34 steel sailboat. I built a plate roller out of some scrap parts and we rolled all the plating and frames. Anyway, the resulting finished vessel was never recognized as a "homemade steel boat" and still isn't 18 years later. We sold her after sailing to the Bahamas and back, and she has been cruising extensively in Europe for 11 seasons now.

Having said all that, the point I'd like to make here,, is after my experience with Ted Brewer (very quick to blow his own horn at the time) was never trust a designer who doesn't or hasn't actually built a boat. They have no idea about the processes involved! Any feedback I sent to him was discarded as if I had no idea what I was talking about. A serious mistake(1 1/4" ) in the offsets picked up during lofting was still there when I talked to another builder nearly 9 years later!

That's why I'm so pleased to see you spending all this time to explain in such detail your hard earned experience to others.

Thank You.

Doug Harrison

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Postby Kevin Morin » Sun Dec 27, 2015 8:39 pm

Doug, thanks for the kind words.

Many years later, I still recall my frustration of not "knowing how" to do quality metal work required in my first welded aluminum boats. It was very ( I could offer some choice- sailor-like phrases but will refrain) frustrating; that circumstance left an impression so now that time allows, I've set about trying to inform others, hopefully to reduce their frustration in learning to work the Miracle Metal?

We've got a lot of these posts to go! hopefully some Glen-L builders will be well served by my "long list of mistakes" ?

cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Postby Kevin Morin » Tue Dec 29, 2015 8:56 pm

Anyone’s understanding of a mechanical problem or set of circumstances may be held within their imaginations differently than another person’s understanding of that same set of conditions. For example, how I view the best way to cut aluminum with a certain type of saw may not be the same as another equally experienced metal worker. So my posts have to be taken with that important grain of salt (or bag of salt): I’m trying to provide my point of view of a method that will produce good quality results.

Ultimately, anyone applying these ideas would have to ‘make them their own’ in their practice of metal working. This upcoming topic is a bit harder to illustrate, perhaps its more abstract and I’m not seeing an effective way to express the ideas that I’d like to convey. I’d sure appreciate hearing from any Glen-L Forum readers if these posts are too confusing, so I could improve the information presented; either improving the text or the illustrations, all suggestions welcome!

Cutting with power tools involved marking the cut, seeing the tool’s cutting edges and guiding it along the clearly defined mark and using the tool most suited to your comfort, skills (and in this post) the type of line to be cut. We’ve seen weld edge bevels, edge shaping after a outline shape was cut but here, I’ll try to suggest ways to select tools/blades and setting for a group of three basic cuts. The first group of cuts are the straight edge, or lines, the other two are curved cuts; long radius or short radius.

I'm going to focus on the worm gear skill saw cut of longer lines. These would be the keel, chines, sheer, guard deck/sheerclamp or any other long slow sweeping curve of the boat- usually cut into the hull's skin panels or plating, but also cut into bulkheads, sub decks and other curves. The reason for this post, which may seem a little too detailed (?) is the amount of error that comes from not planning your tool use for these long cuts.

Image
First image above of a red blade passing through three sheets of plastic illustrates that the length of the cut is related to the depth of the blade setting on the saw's table.

Image
IN this sketch of the three sheets of plastic used to show the kerf length, the longest is at the top- which was farthest up on the blade- so the deeper the setting the longer the cut length.

Image
Above the set of blades in a straight cut. Here, the deeper cut setting is very beneficial- the longer kerf helps to keep the saw tracking in a line. But that is not the case with all curves and here is where attention is worth paying to this tool adjustment and technique.

Image
Just above is another view of the previous sketch and here for a reason - we need to take a minute to discuss skill saw blades cutting aluminum from another view point (no pun intended). The blocks of wood represent 'cutting boards' just 2x6's laid along the material under the cut area to #1 support the cuts edges while cutting, (OFTEN on large sheets you're crawling on your knees behind the saw depending on the panel shape/size and the original material size) #2 to clean the tips of the skill saw teeth while returning upward to cut metal, #3 to reduce vibration of the blade due to uneven loading while cutting aluminum on one edge and turning free on the other, #4 this also improves blade life by the #2 & #3 reasons, and it keeps the kerf narrow compared to a vibrating blade.

Notice that the blade depth at full reach (left hand blade) would probably cut through the 'cutting boards' so planning how to lay them out is part of using them over and over.

Image
This image above shows a set of three different lengths of red rectangles, like sections of the saw blade. One set on the left are on a straight line cut the others to the right on a curved line cut. Just about any amount of depth setting for straight line cuts will work fairly well, if lubricated regularly with pan spray and the sawyer's eye is kept focused behind good PPE on the exact point where the carbide teeth come up through the metal along the scribed line- highlighted by the reference line of black ink.

Image
This image above, shows the effect of different lengths of the saw blade's dept setting on various curved cuts. If the saw is set too deeply it can create an interference with the previous cut edge (cut by the leading edge guided by your eyes) by 'dragging' the blade's back teeth into the already cut edge- destroying or at least messing up the cut line.

It is very important to notice that this saw is cutting the INSIDE curve not the outside of the curve. To make these terms clear- in this image the curve is hollow to the right side, so the 'inside' is the right most edge as this drawing is shown. That is not always the case! If you marked the curve in this case, from the other 'side' or with the reference and scribe to the right of the kerf shown- and used the saw from the other end, you'd be cutting on the 'outside' of that same curve.

In the case of an outside curve the back of the blade usually takes material off the waste/drop/off-cut material since the teeth reach 'across' the kerf versus curve; instead of the instance shown where the teeth could reach inside the cut line to damage that cut.

Image
This image above of two saw blades starts to summarize the points made in this post. At the left side is a blade with a shallow depth of cut- making a kerf rectangle with a short length that fits inside the cut out material and does not re-cut the trailing edge of the saw blade. Buttttt.. that's not true of all curves for the deeper cut of the right hand blade shown.

Image
Our last image above, shows the detail of the potential error of and INSIDE cut curved line with the blade set TOO DEEP. While that setting can be helpful in straight line cuts, it may be a hindrance to the inside curve cut if the depth of the cut allows the trailing edge of the teeth to re-cut the scribed edge.

I put a little green triangle to show the blades' back teeth area of cut. Now this is probably not going to happen on 80% of a long cut if the curve of a chine, sheer or even a keel is considered. BUT where those three groups of curves get "shorter radius" or become tighter curves, at the bow of almost all planing hull shapes; that is where this can become a critical error in using a skill saw to make curved cuts in aluminum.

Image
Above is a photograph of two pieces of 1/4" plate being cut into the bottom and chine shapes for a 25' skiff. 85-90% of the curves were cut with a skill saw, and the last few feet were cut with a jig saw. The radius of the curves combined with the depth setting of the skill saw allowed very fast and fair cuts, however when the curves tightened up- toward the bow the radius of the curves typically shorten- there the blade on the skill saw was raised to make the kerf a shorter rectangle and to avoid damaging the previous cut edge with the back blade teeth- and when the curves tightened even further (?) another saw with an even narrower kerf was used to finish these curved cuts.

Summarizing: Skill saw are currently the most effective hand held power tool for long cuts of aluminum sheet done by a builder's own hands. Using good care and forethought, this tool can cut almost perfectly smooth curves of an incredibly wide variation in radius if care is given to the setting of the depth and the teeth on both ends of the blade as they approach the metal being cut. When a curve become too short radius to be cut with a skill saw the jig saw is powerful and consistent enough to provide the final cuts without any sacrifice of time or quality of cut.

I can (and have) cut entire skiffs with jig saws, some builders depending on their strength and skills may find the jig saw a preferred tool. Those cuts will be slower than skill saw cuts in most cases, by using a Vixen file, all cut edges can be dressed to clean, sweet curves ready to tack into a fair hull.

Having introduced curves it seems a good time to begin to discuss some of the layout tasks that establish a series of Rules of Thumb when dealing with curves in WAB's.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Postby Kevin Morin » Thu Dec 31, 2015 4:04 pm

It seems to me that a discussion of curves for the metal worker is in order? I'll take it as given that wooden boat builders have their own versions and fundamentals in this area of work, and I'll assume those techniques are based on similar facts and methods?

What I will report, and use as my justification for this level of building methods review is that I've encountered many (lots and lots) of metal workers who are almost lost when working in curves! Curves are just a group of lines and work well using similar marking and cutting techniques but for lack of practice or step wise explanations seem to elude many metal workers. I'd like to offer a series of posts that address curves from the basic terms to common practices and even provide suggested work techniques that could be adopted by the first time builder in welded aluminum resulting in a clean, fair and smooth build.

AT this point its important to explore some of the aspects of working curves in metal; layout (from different sources of information including plans), next is marking (we've covered some of the basics there!) and then cutting and we've also addressed some techniques, already, that should help produce high quality edges along fair, sweet curves.

But let's take a look at the value in the market place of using all these techniques so far? If you purchase the boat plans and a CUT FILE Package- you don't need 95% of the information we've covered so far. This next section on curves of several types and work with those line types are also not really needed if you're buying the plans and the cut file outlines/profiles of the parts and have a service cut them for you. The layout and planning, the cutting and fairing are all done (except perhaps some dross removal) and the boat metal arrives ready to assemble.

So if you take the cost of the cut files (Cost #1; computer files) , and the cost of the service of cutting (sometimes this cutting service costs more in handling and cartage@@@ than just the cut service) (Cost #2; cutting of computer files alone) and add the cartage if there is local handling cost adders for cartage compared to shipping(?) (Cost #3; "handling";cartage;crating;shrink wrapping a pallet) you'd have a figure for the value of this work we're discussing. Taking your own learning, labor, hand work in all the steps being done up to beginning to assemble the boat; you'd have a way to compare the value of the first 3 costs compared to your work doing these tasks yourself.

Most commercial builders use NC because they pay wages and wages mean all sorts of "adders". Wage plus insurance of several types, wage plus employer contributions, wage plus having to pay to heat and supply the shop for those days or weeks it takes to do these steps we're discussing, and finally wage plus all the other unlisted costs. As a past employer of crews of workers I'll say that the wage is often tripled or even more - to get a market figure that is profitable.

When that scale of factors over the base wage- an NC cut cost (summary of the three items roughed out above) is compared to a much higher unit cost per hour than a home builder who is not paying for all the wage Plus factors I've listed. So, I find that in my area, due to base costs of all the services, I can make a decent wage for my old tired carcass doing this work myself. That is, since I'm not paying wages; I choose to layout and cut by hand methods given my local costs for NC services arrived in Kenai AK.

However, what we're discussing here are the skills, concepts and techniques that you'd need to approximate/adopt/acquire/apply in order to have any alternative to buying the metal cut to shape. On the other hand, if you're paying rent for your shop, paying for some work in certain parts of the project (welding? help hanging sides? or other work) or have no interest in learning these skills and applying these techniques, at least you'd have some basic means of comparing the "value to you" *** of a cut package versus buying stock plans from Glen-L and doing all the build steps for yourself?

If you know what the cut package costs, and can get quotes for the metal and shipping (w/cartage if involved) then you'd have an idea about what these steps values are in cash. So you could ask yourself if... you want learn and practice all I'm discussing? or Just hire it done?


@@@ Cartage is the term used for truck services inside a city not from city to city - like freight or haulage. Cartage is taking a sheet from the metal supplier to the cutting service and back to the supplier for bundling and shipping to the metal supplier's client. Some cities have unionized and regulated cartage that can make a trip across some towns as costly as it is to ship nearly across the county. Cartage costs must be figured/anticipated/quoted firm as part of any metal supply package. (word to the wise) My tale of woe in learning this was having a single sheet moved from one location to another to have the second location's machinery do some forming not available else where- only to be charged almost as much to move that one sheet as it did to haul the entire boat to Alaska!!! Unions and tariffs can have unseen costs!

*** note: this is not the cost alone, this is stated in terms requiring self-evaluation of the cash to buy metal ready to fit and assemble, compared to what your time is worth? Perhaps there are, like me, health issues? physical limits? calendar limits? or other considerations that make this comparison an important part of your welded aluminum boat planning?

we'll start on a metal working with curves discussion shortly.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Postby Kevin Morin » Fri Jan 01, 2016 3:41 pm

After a brief exploration out a limb on the tree of our topic, here is a discussion of curves that will be important unless your boat will be a box.

Curves are lines that are not all straight or that portion of a line that changes in XY, and many times in boats; XYZ space, along its length. That's the easy part, what we really need to discuss is fair curves. I'd encourage everyone to search the 'net and read the articles on this subject of "fair curves" and come back to our discussion here. When you come back, you may realize there is no absolute mathematical definition of a fair curve- so we have to conclude that fair curves are like where beauty is "in the eye of the beholder."

We need some basic terms for our discussion and those will be my terms, or the terms I prefer to use since this is my opinion and the ultimate definition is "up in the air."

The chine of most planing boats, that line between a bottom and topsides in hard chine boats, when viewed from the Profile View (a few topics down from here is an introduction to the Lines of a Boat with terms and views) usually has a straight line, aft and a curve upward in the forward 1/2 of the Profile View of the boat.

That (chine) line has three parts; (#1) the straight after line that I will call the 'baseline' (a reference line), (#2) the tangent point (shown below in this sketch of the lines' parts) where the curve begins and (#3) the curved line forward. We can ignore the baseline to the right of the tangent point- it has served its purpose left of the tangent point.

Image
As noted in the previous paragraph, this sketch, above, shows two sheets of paper with a simplified chine line (taken from a typical Profile View- Bow to the right of the image) and labels the three elements I'm establishing as (some of the) terms for our discussion.

Let's make this chine line, from a Profile View, as the basis to introduce curves' errors- that is; characteristics which are generally not desirable in metal boat building. (well I'm thinking all boat building but I'm sure about metal ones)

Image
Above is an image of several lines on a page, one view (the lower) is taken to show the need to always 'sight' the lines or curves, from their end's. This is called foreshortening, where the line or curves seem to get shorter and the faults or flaws can be seen more easily. The upper view is almost flat (Plan View of the page which is a series of lines in the Profile View of a Plans package- please re-read if that sentence is not clear? thanks.) to the viewer so the shapes are not foreshortened as in the lower page shown rotated and inclined to our view.

There are four sets of lines in groups from the top. The software I used was not set to the highest resolution for this set of images and the reproduction of some of these lines may suffer somewhat on our storage and screen displays as well- SO.... I'm going to point out some features for your consideration that may not be obvious due the factors I've listed?

First, the top set of lines shows a base or reference line, like the others do. That set lines shows the curved line to the right sweeping off the baseline from a tangent point (that is hard to see in the upper image but somewhat easier in the lower) and then curving upward and to the right. HOWever, the arrow points to a 'flat spot' in the curve. The point is this curve is not 'fair' due the flat segment at the tip of the arrow in the upper set of lines. The line is hogged" at both ends of the flat segment, the curve has 'angle points' at the beginning and end of the 'flat spot' not even curving changes in shape as the line progresses. I hope this flaw shows up in the poor resolution I've provided?

The second set of lines down, shows the tangent point as an angle point- the transition is not only visible, its stark and again this set of lines is not fair due to the angle point at the tangent point. The tangent is not supposed to be visible in the sense of distracting your eye.

Third set of lines shows the a curve beginning at a point but in this instance the curve drops below the reference line/baseline instead of rising away from it cleanly. This wouldn't be a very attractive or functional chine line (Profile View) for any boat.

The lowest set of lines shows what we'd call a fair line. A curve rises cleanly and without hoggs from a baseline, departing at a tangent point and continuing to the right of the page (bow end in our case).

Summary: Fair curves are not necessarily exactly defined by math, but are primarily an opinion of the boat builder. Some of the flaws of curves are angle points, flat spots (or waves- multiple flats and curves inside one curve) and 'unrelated' curves that appear to wave the curved line. Clean curves can be drawn with reference to a baseline and the baseline and the curve seen together do not show the tangent point as a hogg or angle point.

Hope these ideas introducing curves can inspire any potential metal boat builder to explore this topics a bit on their own- online? This set of concepts will be expanded but if the fundamentals shown are not rock hard in your imagination then: you cannot successfully build your own boat from scratch and should consider focusing on a pre-cut package plans set.

Cheers,
Kevin Morin
Kenai, AK
Last edited by Kevin Morin on Sat Jan 02, 2016 2:35 pm, edited 1 time in total.
Kevin Morin

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Re: Notes on Metal Boat Building Methods

Postby Kevin Morin » Fri Jan 01, 2016 5:13 pm

Since we're talking about curves, and introducing the concepts of a fair versus hogged curve(?) we need to bring up curve drawing tools. Curves (meaning fair curves) are not easily drawn by free hand, that is an incredible discussion left to the art world, so the curves here will be shown drawn using tools.

There are two general groups of curve drawing tools; fixed curves and flexible or variable curve drawing tools. I'll show a reference to the fixed tools and mention that the art of using these tools is VERY much an acquired skill- not for the faint of heart! (and I mean the !!!! )

http://www.draftingsteals.com/21270.html this link to a vendor of drafting supplies shows various different examples of the two general groups of curve drawing tools. The first group is are rigid plastic outlines of various curves and I will suggest these tools take years of practice to use well and are almost completely reserved to drawing designs- not building metal boats.

Designs (drawing boat plans) used to be done to scale on paper, so the rigid curved drawing tools shown (ship's curves) could be used on paper to draw fair curves, but would hardly be of any help on a 20's sheet of metal, or even a 4'x12' sheet for that matter. I want to stress again; learning to draw entire boats with these rigid curve forms is not easy- the skill comes from being able to combine their countless sets of curves into clean single lines of a hull! (not for the impatient!)

Down the page a bit is another product http://www.draftingsteals.com/catalog-d ... urves.html the flexible or adjustable curve "batten". This product allows just as many different curves as the rigid templates but this tool can be used with less skill and practice. (thank Heavens!)

So let's review a batten- a batten is a uniformly flexible, uniform edge drawing tool that will bend to a curve and not deform or break. These plastic interlocking extrusions slide in tracks inside the adjacent extrusion and therefore will bend to different curves BUTTTTTT they will not kink, hogg, or allow angle points in a curve because that would require cracking or kinking the flexible material.

Image
In the sketch above, we're looking at some incredibly fundamental factors involved in using a batten to draw on plans, models, and to layout, mark, and finally cut full sized metal boats. The principles are based on plans drafting images but will convert to the real sized work. The importance of these principles cannot be stressed enough.

What's in this image above? The paper shows a baseline or reference which has been copied out to the left to make sure we recall that the left side (aft, in our case) is covered by the batten where the batten is common to the baseline.

Rule of Thumb #1; Battens should extend before and after the curve to be drawn

The batten is springy, all 'correct' (to be discussed in detail) battens are somewhat springy and try to return to their shape- so we use restraints. Here drafting ducks (also called 'whales' because of their shape) have enough wt to force the batten to say 'in place' where its set by the designer's eye or by numbers.

Rule of Thumb #2: Battens may have to pushed OR pulled AND held in place.

In this image the flexible or adjustable battens (cyan colored here) from the link above is shown, laying flat to the paper being used to draw the Chine in Profile from our previous images in this discussion of basic curve principles.

Rule of Thumb #3: Different cross sections of battens will 'allow' or tolerate (without bending permanently in deformation) different 'families' of curves.

Thicker and wider cross section battens will not bend as tight as thinner and smaller cross section battens; all battens should return to their fully original lengthwise shape- or they are too large in cross section for the curves formed.

Image
Zooming in on the batten and ducks sketch (2nd above), to look at left most two drafting wt.s holding the batten along the reference line- this is the reason the term reference line is used. This particular curve 'originates' from the baseline/reference line- departing at the tangent point and rising to the right out of frame. These two wt.s hold the batten (more may be needed?) to the reference line- the batten is held Straight up to the tangent point.

Notice that the nearest drafting/duck/whale wt. or clamp holding the batten to the baseline.... is just toward the reference end from the tangent?

Rule of Thumb #4: The batten should be clamped 'some distance back' on the reference line.

The distance (referred to above) will change with different battens and curves of various radius and this clamp or drafting wt is often moved as the batten if 'faired' long the curve sought. More on this point in future posts. Very important to note this concept as we move forward and apply these concepts.

We'll get much more into these details in future posts but the following few ideas are very valuable to realize. If you have to read this post 100 times for this information to become part of your thinking (?) then it will be worth the time. The follow few ideas express why building welded metal boats by hand could be one of the easiest building methods once these principles are applied.

Image
In this sketch, above, a fact of metal products and how they could be applied to one off building of WAB's is shown. The upper sketch of a scaled 20' long aluminum sheet shows a grid set of vertical lines and the typical outline of a planing hull's topsides panels. The top of the outline would be the sheer cut, the lower line the chine- left end is the bow stem and the right end of the outline the topsides to transom line.

What is so important is the lower model where a regular aluminum extrusion is being used as a simplified batten for an arc shape. The significance is; all boats' curves can be battened by one or another OR a combination of off-the-shelf extrusions used as 25-30' long battens! These tools, purchased as part of a regular skiff build can produce layout and lofting lines of 1/64th accuracy and repeatability- that is as accurate as any NC cut file offered!

Anyone who's lofted a set of offsets, or lofted from a lines drawing realizes that the scale of the drawing and the line width of on paper (in scale) induces errors that could be quite large- using full sized aluminum battens can reduce those inherent errors to less than 1/64th inch! The method used here will rely totally on this fundamental aspect of the use of aluminum extrusions as battens for may jobs in building welded aluminum boats.

Image
Just above, a photo of a 1" x 1/4" flat bar, on edge, being used to batten (fair out) a set of points laid down on a grid on a sheet. Some of the vise grip clamps are pulling the batten, some pushing and some just holding it down tight to the sheet. Aluminum extrusions used to fair curve offsets, layout points, modeled outlines can reduce the natural drafting errors and create complete fair shapes.

Image
Clean layout, batten faired corrections of design (paper) errors in measurement does result in clean shapes, cut with accurate marks and good tools use means anyone can build a fair hull.

IF these ideas are not coming across clearly, please let me know(?) so I can try to upgrade the posts or review and add illustrations to try and clear up what I may have left vague?

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin


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