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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Kevin Morin
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Notes on Metal Boat Building Methods

Post by Kevin Morin » Wed Dec 02, 2015 4:05 pm

Since the topic of building in welded aluminum has seen a few recent posts, a little awakening from this category's sleepy past, I thought I'd write a series of articles on some of the aspects of metal boat building that seem to be challenging to new builders. I'm not sure these topics 'scare' everyone but more than a few emails to me indicate that potential builders consider their lack of knowledge too big an obstacle to overcome.

As a result of this seemingly widespread lack of understanding about metal boat building techniques I've decided to post a series of illustrated articles that lead to a wider (maybe better?) awareness of "how to" build a welded aluminum boat. I will NOT be (fully) addressing welding in this initial series as I consider that another issue and one you may be able to find instruction for at your local community college or tech training center? I will concentrate on, some fixtures, tools and ideas for "fitting", a few basic methods of working with sheet material, and especially on 'taking off' developed sheet outlines from a frame - model size or full size.

This series will not fully the NC cut packages where the frames, (some) longs and hull panels' outlines are already laid out by computer and cut - ready for assembly into a boat. This thread will concentrate on the 'old school' method of doing all the layout and fairing, all the cutting and all the tack up (but not discussing welds in detail) by hand with hand tools (powered hand tools!).

My goal is to add to the Glen-L 'knowledge base' of reference articles in the library here. The reason to post here is the community of owner/builders who may build one or two boats and use them for themselves and their families- a boat building community that I wholly support and admire. If I can help someone to learn a few steps in the building process that will make their boatbuilding easier or results in less efforts while contributing to a higher quality final boat? Then I've accomplished my goal and the effort to post was worthwhile.

I'll start with some remarks about building and the age related limitations and considerations I've learned as I've gone from the bullet-proof 20 year old welder to the senior citizen (65) builder who needs to pay more attention to "gravity".

Please feel free to join in, this is not intended as the last word, just a series of explanations of the questions and problems I've received in emails for years. I believe most if not all the general ideas here will be seen by the wood working boat builders as same or very similar methods?

Let's start with some basic ideas; terminology.

Cheers,
Kevin Morin
Kenai, AK
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Bill Edmundson
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Re: Notes on Metal Boat Building Methods

Post by Bill Edmundson » Wed Dec 02, 2015 4:18 pm

Kevin

Thanks.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
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Kevin Morin
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Re: Notes on Metal Boat Building Methods

Post by Kevin Morin » Thu Dec 03, 2015 4:55 pm

In order to make a series of posts that have any hope of giving the readers some ideas that may help in a welded metal boat project, experience shows that giving some terminology or definitions should be the first step. If I use a term, and you read it for a definition I don't intend; I'll have written a statement you won't understand as I've intended- so I'll have sown confusion. Confusion is what I'm trying to reduce!

So here are some terms and remarks about the ideas that will be presented on this thread. Definitions and background information that I think need to be the 'given facts' we all use when reading this series of posts. IF you know I'm wrong, of even think my ideas should be edited- NOW is the time to add your post and correction! If I'm telling the Forum something and you've seen that is incorrect PLEASE take the time to call it out, so we can all move toward better knowledge of welded aluminum boat building. Thanks, KM.

Welded aluminum boats are boats made of Marine Alloys (of Aluminum), usually 50XX and 60XX series alloys and are not formed of the other series alloys like: Gregors, Lunds, Starcrafts, and other stretch or roll formed and riveted production boats. The manufactured boat is made of aluminum but is not realistic for home building due to the huge investment in forming equipment, fixtures and engineering costs that are required. Welded aluminum boats can be made one-off with wood working shop tools and a DC MIG welding power supply, using adapted wood working techniques and welding.

Link to a vendor's site: http://www.alascop.com/al.php

Welded aluminum boats are those boats made of Marine Alloys and cut by hand or machine where the individual structural elements are cut out from various metal stock, joined by welding, MIG or TIG and not by riveting of the main hull seams; chines, sheer, keel and transverse elements. http://jobsite-us.com/custommetalfabric ... g-welding/

Metal terminology; uniform thickness plates or sheets of marine aluminum are available in different overall sizes but the term sheet begins at 0.125” or 1/8” material thickness and is commonly used for relatively thinner material. Plate is the term used for material thicker than sheet, so; 0.160” or 5/32” material, 0.187” or3/16; 0.250” or ¼”; 0.375” or 3/8” and thicker- are generally referred to as plate.

Aluminum can be forced through a shaped “die” to result in a continuous length of that shape’s outline; this process is called extruding and means that aluminum, unlike most other metals, can be purchased in an almost endless number of cross sections. This group of aluminum stock is generally referred to as extrusions and named by the cross section, for example; extruded angle, extruded channel or extruded T bar. Shortly after working in these alloy shaped length the word 'extrusion' is dropped and they are simply, angle, channel and Tbar. Most boats can be designed and built of a fairly limited number of different extrusions combined with plate or sheet material. Because extrusions are sold in many shapes and many different sizes of those shapes, the variety of extrusions commonly available is very high.

Vendor link: http://www.alascop.com/al_rbs.php

Weld aluminum boats are most often made from two series of aluminum alloys the 5000 series and 6000 series which have good welding characteristics and good corrosion resistance to salt water. Once welded, both alloy series do lose some strength in the weld zones (HAZ Heat Affected Zone) but overall; retain enough strength to allow high speed, lightweight and reliable welded structures.

Design and Layout Terms:
Curves are lines that are not straight and in boat terms we call pleasing curves ‘fair’ and unpleasing curves hogged. If a curve has no angle points, or kinks, (hoggs) or is not curved in a manner UNpleasing to the eye in different locations along the curve, the curve is fair.

For welded boat hull (like most hulls of all materials) to remain fair, the shapes of the hull must all be described by either straight lines or fair curves. In boats, we strive to design and build in fair curves more often that straight lines. Many boat curves are in 3D space not flat lines found on a drawing- these lines curve in more than one flat plane in space.

Battens are drawing tools used to draw curves, and especially to draw fair curves. Battens can be any semi-rigid material that bends uniformly without permanently distorting and therefore relaxes back to a more or less straight line form when released from clamping forces. If you hold a 6’ shop ruler, on edged, into a curved shape, it will remain fair until you exceed the curvature of that ruler’s elasticity; then it will deform/bend permanently and not spring back. Boat building battens should always spring back or they have deformed. IF you select a metal batten and it deforms in the curve drawing purpose; that batten should have less cross section and the work should be redone.

Image

This image shows a (purple) angle extrusion being used as a batten, held in place by three clamps (more are commonly used) to layout a line that is an expanded circle; camber pattern that would be common for deck beams. The angle is uniform in cross section, stiff enough to bend but not deform and rigid enough to make the arc an even and fair curve; therefore this extrusion qualifies as a batten for this layout job. Typically all lines in any boat can be drawn with off the shelf extrusions resulting in measuring, marking and cutting then fairing the edges of parts of a boat to within 1/64th Inch- by hand with no special tools. However this method does require time to perform the layout, marking and hand cutting and clean up; all of which can be hired out by purchasing a Cut Files package and having this work done by an NC cutting service.

IF a wooden batten exceeds its elastic bending capacity it will snap but metal battens will simply bend and deform into the bent shape.
(our discussion will not focus on hard shaped drafting tools like French Curves, Ships' Curves or other rigid outline drawing tools)

(Welded Alum.) Metal boats hulls are of GENERAL two types; one much more commonly used than the other. The first type in our discussion is a series of hull shapes that are the combination of three exclusive geometric shapes: flat planes, conic surfaces, or cylindrical surfaces where all the boat’s shapes in the entire hull are drawn from these three basic shapes. These hulls are called developable shapes where all the surfaces can be cut as outlines of flat material and the pulled, cold formed, distorted without Plastic Deformation into the hulls' forms. All that is required is to cut the outline and hold the material to the frames OR to hold the material’s outlined edges to an adjacent sheet surface outline piece.

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This page copy shows the marine software output of all the hull panels of a little skiff as flat outlines- these are the 'developed' shapes as they would be cut by an NC service.

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This image (above) shows the 14' skiff from various angles of orientation and scale. Some of the hull panels may look like compound curves but they are not. Some hulls' perspective drawings or models may give the illusion of compound curvature even when the hull is fully "developable".

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(Above) the same 14' skiff outlines of all hull sheets cut and tacked edge to edge showing the relative accuracy of computer generated cuts. This hull was laid out and cut by hand using the outline's dimensions- the method in this series will result in this level of accuracy if applied carefully.

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(Above) The 14'er finished and painted with the hatch cover/seats. This is an example of a developable hull, all flat shapes, cut to outlines and then fit and tacked edge-to-edge using methods that will be show in following posts.

{NOTE: I am not selling plans, do not offer any plans or cut file packages, and do not offer to consult or help build any of my designs. The illustrations here are my own, the pictures generally of my work, unless noted, and are exclusively here for education and explanation of the processes I went through to build the boats shown.}


The second, and less common, welded aluminum boat designs have compound curves, where the sheet materials have been deformed in thickness to stretch to form geometric surfaces not limited to the three of the previous limited surface type hulls. These hulls need some are of the hull's plates or surfaces deformed by Plastic Deformation using English Wheels, or other types of stretch forming equipment.

Flam is the term used for the “lean out” topsides of a conventional hull and Flair is the term used to describe the less common hull’s topsides shape. Flam is a combination of a cone and cylinder which can be formed of developable surfaces without any roll forming or stretch forming. Flair is a shape that requires forming and in most cases would also require planking or piecing the surface together from multiple formed pieces of plate or sheet.

Image

The image above shows the two terms we'll see in the future... Flam and Flair. Lots of owners say that flam is flair, but what then is flair? I show the difference in this illustration and suggest that most all designs for the home builder only involved Flam? Flair requires the metal to be shaped in two different directions. So take piece of paper and hold it into a curved boat side and then peel the upper edge outward! the paper will tear and you'll see what Flair requires.

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(Above) the same idea just with more views to make the geometry easier to see in a typical all gray online illustration. The Flam shape, even with some bulge (convexity/bulge from chine to sheer, outward curvature in the topsides) can be formed from developed plate shapes in welded aluminum but.... the Flair will require forming equipment, may require multiple planks instead of one large 5'x25' long sheet of aluminum.


Additional books that are helpful to the new metal boat builder:
http://www.amazon.com/Devlins-Boatbuild ... 0071579907 Mr Devlin has a section on taking off the hull panels from a plate model that is similar but not exactly what will be shown in this thread. However, the method is worth reading, and in my opinion worth reading his book to see clearly his method of plate modeling.

http://www.amazon.com/Boat-Building-Ste ... 0877420297
This is kind of the older standard reference to metal boat building but it does show good ideas and solutions to some of the larger scale projects that could be considered. I've had many copies over the years, and consider this a very foundational work on the subject. Surely worth the few dollars it will cost when considered against the cost of a single sheet of aluminum !

Please feel free to post up with any questions clarifications of terms or typing(!) and any other additions to the terms and background facts for the series of technique posts that follow.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Post by Kevin Morin » Fri Dec 04, 2015 7:50 pm

As part of building a welded boat, and probably most other materials too, I want to note that welding, that key element to these boats, is easier if the weld position is horizontal, flat and not in made with an Olympic body position. If all the welds in a metal boat were done on the bench top, with good visual access, stable body stance and balance; then all the welds would be better quality than those made even by professional welders on most boats.

For example if the deck frames are installed and some remaining welds have to be completed below the deck its very common to kneel on small ply deck pieces and weld beneath your knees! That may have been realistic a few decades past... but its not happening now! I you had to crawl into a tight space, pull your torch, hood and all the other welding equipment in with you and then contort into an uncomfortably contorted position to reach some weld buried in that compartment (?) well lets just say it's a good thing most of those welds aren't seen.

All this means that any builder, regardless of their experience can improve their boats' quality of build by making a positioning fixture to enhance access to not only weld but to fit, fair, joint prep and clean up the boat as the build progresses. I realize this adds expense, and somewhat delays the built but I show you what I finally did after many years of crawling around on the floor tacking up skiffs that were keel down, sheer up.

The first image is a conceptual sketch from the original conversation I had with Jack Davis (Oregon fabricator), online, while we discussed the idea of making a rotisserie type fixture that was really useful in building welded aluminum boats.

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The sketch (above) shows some elements that ended up being in the final Davis Jig(s) that I've built. First, the base roller frames are triangular on the casters, they have two uprights with slit pipe pivot bushings that will clamp onto the pivot pin pipe. That is all shown in orange or tan, except the pivot pins are yellow pipes ending in 5"x5" square stock.

I intended to power this rotisserie (Davis Jig) by the large gears and chain reduced hydraulic motors but found another way that is a little more functional. (several images next post)

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This photo of a 20' length inside Davis Jig shows the details of the two end frames' vertical supports nearest the boat frame supporting main beam. The vertical pipe in the foreground had a piece of channel tacked to it that was not used, but note that pipe is telescoping into the 2nd vertical pipe that is saddled to the triangular base frame. The entire pivot pin (horizontal pipe) can be raised or lowered (lowest setting shown) and the two pipes can be pinned to one another .

The pivot or clamp bushing is 3" sched. 40pipe slit with flanges welded along the edges of the slit, this allows the (4) bolts to be tightened so the flanges grip the horizontal pivot pin of 2-1/2" pipe and either stop the boat's rotation OR make it moveable by hand. The boat is balanced at all times by raising or lowering the vertical square stock in the cut down 5" box welded to the end of the pivot pin.

In this photo the main beam, running out of frame to the left (4"x 6") is lifted to the highest position. A boat's bottom panels and keel, once mounted on frames attached to the main beam, or a bottom fixture on that main beam would have a center of mass very close to the pivot pin so it will roll without much effort.

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Above, is a perspective photo taken down the length of a 20' main beam Davis Jig with the main beam lowered several holes in the two uprights. The uprights were 4" x 4" in this Jig. The entire fixture, even with a skiff mounted, could be rolled around the shop by one person with little effort.

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Looking down on one end to gain more scope of view we can see the base with its two concentric masts or vertical pivot bushing supports and the pivot pin's square sleeve to allow the two verticals to slide up and down adjusting the main wt of the beam and skiff as close to the center of the pivot pins as possible.

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This beam clamp allows the builder to locate supports of many types, or even parts of the frames of a welded skiff along the main beam. The bolts are only 3/8" x 8" but were more than adequate to hold even fairly large skiffs. The top of the clamp is two pieces of 2" x 2" T bar extrusion welded to a 4" x 4" angle extrusion section. The vertical leg of the angle is where a former/frame/female former section or any other support attaches to the main beam.

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This metal dory was one of the first boats I built using a rotisserie (Davis Jig) and I ended up using the inner deck (hollow bottom boat) as the frames' linkage to the Jig's main beam. However, this photo shows the main beam over the dory and being held up by overhead chain lifts, giving great access to fitting or welding inside without kneeling down, scrunching up, or making contortions that would reduce weld quality; even for a full time welder.

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This photo of a 30' long Davis Jig (main beam has 2 pieces flanged @ 10' & 20' ) and the vertical socket on the inboard end of the pivot pin pipes is 14" long so two holes 6" apart could be in one piece of vertical allowing a little more vertical adjustment to centering the mass of the skiff in relation to the pivots.

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(Above) the longer jig with a boat bottom under construction. The 30' beam version was too flexible (I used too small box) and has a set of two tension rods (trussing rods ) below the main beam to make the beam rigid when the frames, boat bottom and longs were installed. Here the boat is rolled to the inverted so that welding can proceed inside and outside in balance to avoid distortion.

Each of the female bottom formers is welded to the vertical angle of the 4" angle extrusion at the top of the beam clamps made to fit this beam's cross section. The skiff bottom is temporarily tacked to these formers to hold the V and the chine-to-chine camber in this particular design.

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This photo of the skiff above shows the bottom rolled so the deck is vertical and illustrates how useful this fixture can be. All the interior welds are horizontal! I did them standing on the floor, the reach was very shallow and the weld was as good as my skill could bring without being compromised by contortion.

Deck beams meet the longs in easily accessible welds that are pure pain in the stern when you're kneeling down! It can't be stressed enough how much quality you can add to your project if you take the time and expense to build a Davis Jig, or your own design of one.

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[This skiff was built as a hollow surfboard with the deck completed and air tested then the topsides were added. This step allowed the interior work to be faster, and less work. Once combined with the Davis Jig's access and the easy welded outside hull seams there was a decent time savings for an old boat builder. I'm not saying not advocating, not expecting any plans package to provide this sequence of construction, it can be done, works fine as shown here but is not common in other plans.]

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With the topsides in place a 25' x 9' offshore skiff can become more than you could roll depending on the shop walls' height! But even then, I rolled this skiff back and forth and made the welding and fitting much higher quality than would have resulted if it were built either keel up or keel down.

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Even tasks that seem like they'd have to be done inside the boat, on the deck, can be done standing flat footed on the shop floor. Here a foredeck anchor locker is fitted and welded by rolling the boat side to side (sheer to the floor) so the work area was fully accessible, the work place comfortable, and the results are nice tight seams with decent welds in proportion to the material and no distortion. While some work was done on a kneeling matt on the deck- lots of the welds were only comfortable while standing next to the hull and reaching over.

OK, lets look at this from another point of view besides me squandering your money and time. If you were about to spend thousands on metal, more thousands on at least one if not two welding power supplies in order to own a welded alluminum boat? THEN what's a few hundred more to find some scrap steel and buy a beam or two to make a Davis Jig so you can optimize both the metal you buy and the welds you're going to have to put down?

If I'd known how much faster I could build (alone or with a helper) by having a rotisserie fixture I'd have built one years ago. Instead I trashed my back, burned spots over large parts of my carcass, and otherwise abused what could have been a longer lived body. My welds were OK but they weren't near as good as they could have been in all positions and I was welding hours a day.. What will your welds be like if you aren't welding full time and have to perform out of position (not horizontal and flat) - well the answer is not as good as if they were horizontal and flat.

My idea in this post is to suggest you consider a Davis Jig fixture that allows you to build a boat of any material, but surely makes welding higher quality for a lower hour welder. What if you practiced for 20 -50 hours before welding your boat? Then you need to weld in a "hard spot". I'd practiced 2,000 hours or more before I built a boat and my welds could have been a whole lot better if I'd had the sense to do some positioning.

Next is more hardware to consider.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Post by Kevin Morin » Fri Dec 04, 2015 8:27 pm

Several years ago I built a 25' outboard skiff and while I had access to a crew for rent, and for part of the build I'd have a very skilled helper; I would still be moving more than I was able. I was moving from one rental shop to another, and needed to be able to do the work of sheet handling, building the cabin separately and to roll the Davis Jig when the time came (3 shops later!) to build the hull.

One of the three shops had an overhead gantry crane but the first two were bare rooms. So I built a pair of bolt together A-frames or gantry frames on scaffold wheels to make it possible for one man to handle sheets, roll the skiff on the Davis Jig and otherwise manage lifting.

The pictures are in a small shop with the cabin but they still show the ideas I used and could help you design your own version to facilitate your build. If you're building in a shop that is so low you can't roll the skiff, you could still benefit by having a pair of gantries to lift the entire build, wheel it outside and roll it there. Again, my idea is that the money to build these simple frames is worth the time and cost because of the multiple rolls they can play in building a boat from 5' wide and 25' long sheets of metal.

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This photo (above) shows the three main pieces of the bolt together gantry's I made. The beam has a set of welded butt plates that are drilled to a matching plate that is welded to the three pipe trusses which stand on box beam stock. My Local Metal Supplier (LMS) sells short beams (these are 6long or so) as scrap when the length is shorter than 8 or so feet? That reduces cost a bit. The box or rectangular beam on the base is similar- all scrap/surplus- not cut from new stock length pieces. The pipe is 1-1/2" Sched. 40 A-53 ERW - nothing fancy or heavy.

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(Photo Above) AT the top of the three pipes (one bent) is a horizontal plate welded @ 90 to the matching drilled butt plate on the beam and the two plates on the pipe side of the bolt joint (4 bolts 1/2" in corners) are two full thickness gussets on the sides of the two 90 deg plates. This transfers the beam load to the top of the pipe truss.

Each set of three pipes are trussed three times in their 12' length using 1/8" wall x 1" square steel tube. The webbing is fitted to the pipe wall and welded all sides. These truss webs also allow the gantry to be climbed- like a ladder - even by old geezers.

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Close up of the lowest set of 1" square truss webbing about 3' above the rectangular box beam base.

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On each I beam I use a beam trolley with a chain fall, all Chicom/import and not expensive.

One gantry on each end of the Davis Jig will roll the boat during a build in fact I roll all of my Davis Jigs from one end most of the time and it works great. The primary reason for two gantries is when you're raising or lowering the centers of the main beam in relation to the pivot pins. This is to attain a better balance when more hull or wt. is added. Even when the 25' skiff in the previous post was complete (except cabin) I could roll the skiff side to side by hand and simply walk side to side to weld, grind or fit, no over head rigging was needed. BUT... the ends did have to be lifted up or lowered down depending on the work done and its position on the hull- so that is the reason to consider two gantries.

The Davis Jig, as shown in the previous post, does have enough flex to allow one gantry to lift or lower one end, move to the other end and move that... and so on. But that is too time consuming and having a lift at each end was worth the time to build the other gantry in my opinion.

Next, we'll need to discuss some tools and tool uses for aluminum boat building.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

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Re: Notes on Metal Boat Building Methods

Post by Kevin Morin » Mon Dec 07, 2015 3:53 pm

Cutting aluminum is sometimes not as well understood as other materials; probably because we cut it less than other materials so its not familiar. This post will attempt to discuss some of the basics of cutting aluminum using some images that I hope do most of the talking for me.

If you cut any hard material the principle of the cut is the same; put a very small area of harder material against a softer material and apply enough force to sheer or cut the softer material. The key elements are the small area of the 'cutting edge' (called sharpness) and the amount of force behind that small edge area- force can be increased by using a stronger arm, a faster moving cutting tool, or a combination of the two.

NOTE: IN the following images I've tried to conserve space by making the larger image of the various blades cutting a piece of aluminum; I've tried to make the cut and initial 'start' of any given cut for the purpose of keeping the comparison to the chisel in wood. I made a smaller blow up, zoomed in window to the left of these images that I hope make the larger cutting tool's images easier to compare?

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This sketch of a chisel cutting a block of aluminum introduces the principles of cutting. The small chisel edge is applied to the side of the aluminum and in the second position has curled up a shaving of aluminum the width of the blade's cutting edge. I have no idea how much force would be require but more than I could push - that's for certain.

The idea remains the same for the remainder of this series of illustrations, even though this would probably be realistic in softer materials like some wood species, aluminum is harder than most wood so this illustration of the idea- is impractical in practice.

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The circular saw blade in this sketch (above) is the all steel type with a very sharp edge (and a narrow edge too) but there is little support for the edge as it impacts the aluminum so these blades will cut aluminum for a short while- the hardness of the aluminum coupled with the lack of a strong supporting steel structure behind the tooth means the blades will dull and bend sooner than other blades.

I didn't draw the heated tips of a cutting tooth on the circular saw blades. However, its very important to notice that the impact of steel cutting edge to the aluminum at the radial speed of the tip of the blade's teeth heats up the corners and edges of saw blades, and that causes aluminum to melt onto the blade teeth and in a few revolutions can coat the cutting edge so much that there is no 'cutting action' left.

Another few facts to notice is the fewer teeth on a given blade circumference, spaced farther apart; allow each tooth to cut #1 deeper #2 farther along #3 therefore be into the metal contact longer in any given speed of blade rotation. It will be easier to see if we look at different blades more closely.

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This blade has carbide inserts that remain sharp longer, in harder material than steel cutting will and they are heavier in mass and support structure on the blade blank, so they usually last longer than pure hardened tipped steel blades. IN this sketch the teethe are closer together, and the tooth immediately in front (of the one cutting in this sketch) would actually be keeping the depth of cut of the "next cutting tooth" shallower than if there were fewer teeth.

The teeth will ride on the metal below the cut plane or chip plane in the kerf (gouge of the blade's cut in the material) and this means the impact of any given tooth is reduced when compared to a blade with fewer teeth and to blades with deeper cutting actions.

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This carbide tipped saw blade is larger diameter that the others; it has many more teeth; they are limited in depth of cut by the blade blank having a back tooth area; that area would ride not cut; the back tooth is a large support for the carbide insert to reduce shock on the silver solder and this all contributes to longer life in this type of blade.

This type of blade would take a finer shaving, have less impact per tooth, have less force required by smaller shaving per tooth and is limited by the design so that the blade's design and construction would allow it to last longer in aluminum cutting service.

The point here was to argue for blades designed for metal cutting, and of those carbide tipped blades seem the most reliable and long lasting even if the most expensive. Also stressed is the tooth loading idea of "less loading is longer lasting" and I hope to have shown why that is the case?

In my experience Freud's "Diablo" brand non-ferrous cutting saw blades are the best buy- for the cost and if well lubricated I find them to last the longest without sharpening of any circular saw blade I've used in cutting aluminum. There may be other circular saw blades that are superior?? but I'm happy with the Diablo brand and continue to use them personally.

I use a generic frying pan, food-release, kitchen service spray (Pam or the generic equivalent) to lubricate all cuts, all sanding and of all tools in aluminum. This grease is non-petroleum (vegetable oil base) and vaporizes at lower temperatures than petroleum or most wax products, as a result: while I make all effort to wipe clean all lubricated cuts with acetone, if some lube is left on the metal the effect when welding is less detrimental to the welds than other products in my experience.


Next, more tools because they're critical to doing good welded aluminum boat building.

Cheers,
Kevin Morin
Kenai, AK
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Re: Notes on Metal Boat Building Methods

Post by gap998 » Mon Dec 07, 2015 5:28 pm

Really interesting Kevin. What CAD system are you using?

It would be something of an over-kill but I wonder if you could use that turnover jig as a base for the form on a wooden boat build.
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!"

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Post by Kevin Morin » Mon Dec 07, 2015 5:54 pm

Gary, all these illustrations have been done in SketchUP (Pro) and most often exported to *.jpg images in various ways provided in that application, then edited, cropped or sized in Photoshop CS5.1/64 to make the output sized to display (800 pix max dim.) and sometimes refine edges that are vague (sharpen image).

I store images at Photobucket and use the [img]0000[/img] text string switches in the post to display; so the site doesn't have to carry an attachment, hoping to keep bandwidth free.

The marine software I'm using is mainly Delftship Pro (I do use Rhino but not often in simple shapes) and I often output to Ske'UP Pro in the "DXF-Out export" feature. I do use AutoCAD, Rhino, SketchUP Pro, and Delftship Pro but for the types of images here almost all tools needed are in the last two applications.

The Davis Jig, like all rotisseries will hold whatever you attach. At least one of the images shows a hypothetical steel frame holding a particle board Station Template or former. The nice part of the Davis Jig is my older carcass can continue to do work that would otherwise be impossible or at least lower quality and I think dangerous.

I also have used this type of fixture to handle wood slabs of about 2,500 lb and could move them with no effort by hand, rotating and cutting as needed. So I'd say any boat builder could benefit from the idea. I showed details to make sure the version I built is clear- there are some features that make this version extremely successful.

The pivot pin being spread between two vertical supports means that neither end will collapse if there were an over capacity move... they'd just shift and roll to balance. The loose fits means that exact alignments are not critical the entire jig flexes while leaving the main beam rigid.

If your back is as old as mine, a Davis Jig is not overkill, it DOES allow the enjoyment of what I like to do without added pain at end of the day!

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
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Re: Notes on Metal Boat Building Methods

Post by Kevin Morin » Mon Dec 07, 2015 7:17 pm

There's a lot of cutting to discuss in welded aluminum boat building, so if this happens to be old hat, just skip it and hopefully in the posts that follow we'll find something more interesting to you?

I may be getting to esoteric for non metal builders, but for anyone that is seriously considering a first build.... believe me when I say that you will be happy for this information to help you avoid the very large number of mistakes that I made collecting this information. If there is a boat building mistake to make, I'll wager its one I've made, and I hope by providing these posts on tools details you can work safer, cleaner, and provide a better prepared weld, with finer lines than if you'd started with less information and figured this out as you went along! (that's not the fastest way to learn - believe me!)

We looked above at the idea of cutting with as skill saw where we got down to the individual chips. I agree that this may seem a bit overkill in detail but if you've had the experience of buying 200.00$ US in saw blades to cut a out a single skiff (and I have) then you may find a savings if you apply these principles to your work.

Can you cut a long sweet curve accurately with a skill saw? YES. There are some keys to the job- done well, some do's and don'ts and I'd like to look at the saw and discuss technique in this post.

First ergometric (human force and control engineering) considerations of circular saws should be reviewed. IF; you're right handed the saw blade should be on your side of the saw motor body or the 'left side' of the housing. So this saw is not very handy for cutting aluminum with the right hand, http://woodworking.about.com/od/handhel ... e-Saws.htm the blade is opposite of the head if you hold the saw in your right hand.

http://www.homedepot.com/p/Makita-15-Am ... /100594812 THIS is more like it! the blade is fully visible when operated by the right hand so the blade to marked line is more visible- that is my work preference but I'm not saying there is not another way to cut metal. I've not seen full time, hand cutting builders use the direct drive saw very much... but they can be used- I just like to see all of what's going one with the blade.

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this sketch shows what's wrong with a hypoid or worm gear drive saw for accurate (+ 1/32" cut lines) cuts in sheet or plate aluminum. Balance of the handles is wrong (IMO) for the highest level of controlling cuts.

If you have both hands on one side of the blade, its much harder to control the exact cut edge than if one hand is on each side of the blade- but that is not the original design of the saw's handles.

I show the correct balanced handle set up, the right hand on top of the saw at the handle with trigger (On/Off switch) and the left hand (this is a right handed discussion) on the OTHER side of the blade's forces resisting the cut. The handle shown is screwed into a nut TIG welded to the rib fence that slides into slots in the table- the fence is turned over and clears the material, and the handle allows good grip, full control and keeps the left hand out of the blade's cutting area.

[SAFETY NOTE: Glen-L does not advocate you modify your worm gear or hypoid saw in this manner, Glen-L advises you to follow all manufacturer's recommended safety cautions, in the tools owner's manual and other literature provided by your tools' vendor. This information is sole sourced from Kevin Morin, who provides it for an educational example of how he modify his tools for the improvement of the physical control of his saws.]

I can either stand and walk along a cut looking down to see the blade edge, or if needed, kneel on the sheet and crawl along and follow the cut line using a saw modified in this manner and obtain a cut accurate to within 1/32" variation of the scribed line. That is the level of hand cutting I consider realistically required to layout, cut, fit, tack and weld a small in aluminum alloys.

What if; the curve to be cut is too tight to cut with a circular saw? I recommend a jig saw. I have used exclusively Bosch jig saws for about 40 years but I'm sure other brands would work. Since I've owned dozens of these Bosch brand saws in many models and they work for me... I've not explored other brands or models. If your saw works to cut 1/2" aluminum that's fine, mine does so I continue with that tool.

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This photo of the curves being cut in two stacked pieces of 1/4" plate have been completed with the Bosch Jig Saw shown using an alumimum cutting blade (NOT steel cutting) and the smeared pan spray grease of the base of the saw is visible along the edges of the cut. The circular saw plunge cut remnant is visible to the right of the photo along the edge of the upper cut.

The power to cut 1/2" aluminum at a decent pace is not common in all jig saws so I've stayed with Bosch but you may find fine service from another brand you already own? Just reporting my practice and experiences, if you don't have the boat building tools for your welded aluminum build, buy Bosch its not significantly more expensive than other brands and is proven.

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Curves are fair, cuts are clean, skill saw and jig saw cuts show the work can be done with normal skills, correct tool choices, (and good blade lube!) coupled with correct layout and marking techniques. This photo (above) shows two thicknesses of 1/4" 5086 H-116 plate being cut for a 25' offshore skiff's hull, cabin in the background.

All cut edges are dressed by hand with a Vixen file. This tool is like a joiner plane, the long bed allows the tiniest irregularity of the cut to be cleaned down to edge that is 1/64th inch true. That is more than clean and accurate enough to build the shapeliest skiff of welded aluminum and build her fair.

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No wrinkles here, all hand laid out, all hand cut, full project using techniques shown in this series.

http://www.yardstore.com/browse.cfm/4,4503.html This file's teeth are always used, in case they're new to your tool box?- pulled toward the user, they are not pushed like a rasp, plane or Surform files. The edge can be held to along its full length to the cut edge, this will fair the cut by only cutting the high points like a long bed joiner plane. However it a specific area of the cut edge needs more removal? then angle the body of the file and it will become a short bodied 'block plane' more aggressive since it cuts in a shorter length of the overall panel's edge.

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One of my past building partners had vision issues, even with magnifiers in his hood, bright lights on the work area he still finds his cuts wander a bit so he made his own 'Vixen Block Plane' by breaking one of his older flat Vixen files in half. (Drop one to see how brittle these files are!). This little block of wood allowed him to screw the end of the broken file to his 'palm grip' and he wears this in his shop clothes to dress cuts- band saw cuts, skill saw cuts, jig saw cuts, plasma cuts, any cut he makes that has an edge he uses this handy 'block plane' to clean the edges. I have copied his tool handle but don't use this model as much as he does, I like the two handed version, but this model is worth noting.

Summary: we've talked some about what tools and what blades (not jig saw blades) will cut a boat's curves and then reviewed in part the idea of using a 'pulled file' to clean up the cuts' edges. Jig saw cuts leave a rough edge that is poor for welding, but just a few strokes of a Vixen file pulled over that power saws reciprocating saw kerf edges will clean up to bright new metal edge as smooth as the top milled surface of the sheet.

IF you're' considering your own build? and you think you're serious, gather some of the tools, cut some metal and Vixen the edges and see if you can believe that this method will get you to clean edges ready to weld?

More cutting to come, there are lots of cuts building aluminum boats.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

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Re: Notes on Metal Boat Building Methods

Post by Kevin Morin » Mon Dec 07, 2015 8:08 pm

Cutting tools do more than just outline shapes or hull panels, cutting tools are crucial for forming welding joint edges' preparations too. Not all metal is welded at right angles and in a boat we could even extend that to almost no metal is really 90deg as regards hull and structural fits and welds. Some times the fit of two pieces that will be welded are not dressed for the weld allowance before being tacked into the hull.

So specialty tools are useful (necessary in many cases) to create weld joint preparations. This post just shows some of the principles of these tools, using a few examples so the future builder can see how easily they could adapt their own power tools to different jobs.

I had designed a retro fit to a skiff's bottom where I'd add two new bottom plates to create a deeper V well below the existing nearly flat bottom plate. I laid out and cut the new 'keel bar' and then fit the two plated so they touched the keel bar's to side edges thinking that I could join all three edges in one weld. However when I lit up, overhead with the TIG torch both of the two side plates were too close together to allow the bead to 'soak into' the backing vertical keel bar.

(NOTE: if you are beginning then on overhead double keyhole TIG weld is not something you would plan for any work. I did this knowing I had a fall back method of dressing the weld and a programmable TIG power supply that would allow me to do this overhead weld using a cold wire feed TIG gun.. the weld is not what we're discussing- just the tooling solution.)

I mounted a trim router into a welded fixture to hold the carbide cutting bit in the correct position to cut the weld prep for this overhead weld.

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This photograph (above) shows the general idea of mounting an off the shelf router into a fixture to hold the cutter in a controlled location in relationship to the weld joint. The V of the boat bottom is the same as the two plates. The pipe with the side slit and flex holes allowed the band clamps to hold the router' s case to firmly.

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This photo of the angle of the fixture shows the position of the bit, when the tape was considered too.
http://www.amazon.com/s?ie=UTF8&page=1& ... hmw%20tape UHMW tape will stick to fixtures or tool bases (I use it on my skill saw and jig saws if the plastic base is gone) and allow them to move smoothly over aluminum even with some chips embedded into the plastic film.

I recommend this product of all sorts of tool use around aluminum since it allows smoother feeding than metal tables, or tables on tools that are loaded up with chips and shavings from the cutting being done by that tool.

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Looking under the router fixture in this photograph (above) we can see the simple parts needed. A couple of pieces of plate, close diameter section of pipe some slippery tape film and a router bit.

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Last in this tool's photos (above) is the explanation of what I needed to do? I needed to cup the three pieces of metal; a vertical keel and two bottom V'd plates, they were all 1/8" thick but came together in such a way as the welding arc overhead would not fuse to the keel's lower edge at the same time it heated up and melted the two side hull pieces.

[Incidentally, if you followed the previous post in regard cuts and edge prep?? the last photo above shows some edges cut with either a jig saw or band saw, then if you look closely you'll see some Vixen file faring and cleaning on that edge too.]

This router fixture held the trim router so it would gouge a rounded bottom groove to the weld joint if the V of the fixture was held against the bottom of the two new bottom panels and slid along. The side cut the two V's bottom panels would also be a rounded lower (deepest) edge and allow a uniform overhead TIG weld to tie all three together in a single pass with double side keyholes to insure penetration.

[I didn't want to do all the work to take off the console, tanks, and rigging to invert the skiff, with a TIG gun it was easier to do the weld overhead-not a regularly performed weld and not for the new builder. The article is about joint prep- not welding.]

Chines, the seam of topsides to bottom are often welded outside first, then welded inside but since those welds may have penetration bulge of the weld bead, sometimes back gouging or trimming the original (outside) weld's back bead is needed before welding. Another weld prep tool can be made for this joint prep in the same way as the outside V router trim tool.

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This sketch of an air router version of the inside corner back gouge tool is like the outside V gouging too. The pipe band clamp is the depth setting adjustment. Once the UHMW tape is installed this tool can be adjusted to the cut depth by running the tool over the weld area that needs to be trimmed.

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Here's another view of the sketch just above, showing the tool's construction of a pipe slit to compress on the tool's body, an angle extrusion (any applicable length) with its apex rounded to avoid dragging on the weld penetrations' bulge and the cut out to allow the bit through the angle extrusion. The UHMW tape would line both outer edges of the angle to stay out of the depth control of the joint prep. The pipe doesn't have to be at 90 to the angle, and I have found these little jigs work better if the pipe is at 10 or more degrees as long as the bit can reach the depth of cut needed.

Let's continue to look at various cutting tools so we can cover some more common cutting requirements for welded aluminum boats.

Cheers,
Kevin Morin
Kenai, AK
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Re: Notes on Metal Boat Building Methods

Post by Kevin Morin » Tue Dec 08, 2015 2:58 pm

There many instances where parts of metal boat are cut to length or shape and then the edges are beveled or chamfered if you prefer that term, and there are other instances where good welding calls for gouging a previous welds' beginning and ends. Tack welding is a very short time duration weld that leaves a spot of weld, not a continuous weld and these are best cut down before being welded over with the permanent longer welds that join the seams of a metal boat.

All the details of the exact ways to cut aluminum, and all the previous examination of the best ways and tools to perform these tasks was spent because of the importance to the finished boat of exact weld seam preparation. If a weld seam is not uniform, if the fit is not tight but has a gap or waves along an edge, that weld, when complete, will usually show those irregularities in the two surfaces next to the weld. This means that poorly fit and faired seams will distort more than well fit seams with fair sides and even weld allowances.

Unfortunately aluminum welds happen at very fast speeds of travel compared to most other boat building materials' methods of joining. While this allows construction to be rapid in some cases- it can also mean that in a few seconds you could wrinkle your boat - forever. The first and most important- excluding welding skills- steps in avoiding those problems and the foundation to good welding is good joint fit, joint preparation and that means the right tools used correctly.

Power (cutting) tools will do all the cutting work of the edge preparation and joint clean up or weld dressing; but there are serious tool control and therefore safety issues to be explored. Holding onto a chain saw, for example, (not a metal boat building tool but worth a comparison) means that you're aware of where that moving chain is every second you have the tool in your hands and its running. Like an open chain cutting tool; many metal working tools need our complete attention and are just as dangerous if handled improperly.

There are several ways to create a uniform bevel on a sheet of metal, a common edge preparation required in building a metal boat. The one that produces the best edge is a router with a beveled carbide cutting bit. However this tool usually need the most set up to use- so too few builders rely on routers.

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The photo above shows a typical roller bearing carbide insert, beveled cut router bit sticking above the table of a plunge router. The number of bits, angles of cut, and other variables available is high so with some shopping the boat builder can find a bit for nearly every cut. This bit cuts about 37deg and was used because the joint prep was bottom sheets already held to a V, so the addition side bevel was minimal - but still required for good weld penetration in the Keel Seam.

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This photo of both the sheered edge of 1/4" bottom plate and the bevel cut with the router bit above, show the small amount of metal taken off and the original crystallized metal from the sheer process. The router, like a very high speed Vixen file, actually cuts to clean, clear metal and takes off the 'junk' that reduces weld quality from a sheered edge.

The biggest draw back to using a router is the guides, fixtures, set up required since the roller in this carbide bit was below the edge of the sheet, and angle extrusion had to be clamped along the edge, under the sheet for the bit to guide properly, that is why I mentioned above this tool is great for cutting aluminum but does require some set up, hand held is not always a good choice with a router.

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The sketch of the section of a skiff's topside gunwale (above) shows some different methods used by various builders to strengthen the sides of a small welded aluminum boat. The topsides are blue the sheer clamp horizontal and greenish blue the inner flat bar and 1/2 pipe to fair lines over the sides are tan and the strut or leg is orange.

The left of the picture shows a half pipe extrusion that will be welded to the sides at the sheer. Looking at the top of the 1/2 pipe extrusion the weld joint is formed as U with the topsides' as the bottom and the sheer clamp or guard deck and the inside of the U joint.

A single MIG weld will fuse all three pieces together but if the joint is not widened at the top, just slightly into more of V than a U, the arc will tend to stay on the sides, and the bottom of the joint will not have good fusion. This implies we need to open this joint to obtain a good weld. A router is great tool for this work but it would need a spacer on the base to keep the router table off the gunwale to miss any tacks sticking up (ot they could be dressed first?) and the guide would also need some sort of leg to fit outside (the left profile in the sketch) to space the bit inside the groove to be cut.

Some welders will cut this with a hard grinding wheel on edge, and with sufficient skill that's acceptable but if you slip the tool will mar and cut the gunwale. Some fitters would cut this with another tool that is called a meat axe, widow maker, and some other names all implying this tool is dangerous. The tool is a 4" grinder, sometimes 7" grinder motor, with a saw blade mounted to the spindle.

This tool is not for the casual tool user, but if configured as I show below if very safe to use. IF you skip the multiple blades shown below, this tool is not safe, and is very dangerous and not recommended for the new power tool user and more than using a 48" felling chain saw is recommended for weekend fire wood collectors!

NOTE: Glen-L does not recommend this tool modification. This tool may violate the safety precautions recommended for general use of the tool by its manufacturer. This tool is solely provided here as educational reference to a aluminum cutting tool that will prepare welds and dress weld tacks and is provided by Kevin Morin, not Glen-L's Forum.


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(Above) The Makita model GA4030 has a small size threaded drive spindle and a steel wheel guard case that allow the tool to be modified in this manner. There are three saw blades mounted to the spindle stacked to stagger the carbide teeth and make the cutting action minimal and the steel guard has steel extensions welded to the case.

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In this view of the tool the stack of (3 each; 4" dia.) Diablo blades is more visible and the two case extensions are also shown enough to see that both are steel pieces TIG welded to the original steel guard.

The lower extension has a piece of UHMW tape attached so this 'foot' (the tool is upside down in this photo) can be dragged along near the weld to be dressed and the tool will continue to cut. The teeth pull the tool away from the user so if the tool get's loose it will move away from the user, and the upper guard extension is a small cross section steel angle welded to the case and curved to add a greater range of guard to the blades.

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The photo above shows the alignment of the three stacked blades' teeth as staggered and not aligned with one another. This creates a cutting action with is very smooth, very shallow, and very slow cutting where multiple passes would be required to take down an edge of plate or remove a weld, or to remove a back weld penetration bulge in preparation for a chine (inside the hull) weld.

IF you refer to the posts above about the ideas of a single chip of metal being taken off in a single tooth's' stroke through the metal; I think you'll see that this tool is not going to A) gouge the metal B) be hard to control C) remove metal at high speeds in a single pass & D) require a vise-like grip to hold and control the tool when in operation? Some metal workers use this tool with one blade and does not follow the A,B,C &D points above- others use it with two blades and those tools are between the 'widow maker' and the very controllable tool version I show here -for educational purposes.

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Above is a photo of the welds along the sheer of a 14' skiff where the outside rub rail, 1/2 pipe profile, a narrow sheer clamp/guard deck and the topsides upper edge formed a weld U as in the sketch in this post. It is hard to tell due all the shades of gray, but the U has been widened into V between some of the tacks and a weld has been put into one of those dressed seam lengths.

This weld is a gorilla weld; big strong and ugly. The weld was 'too hot'; too slow; and to big for these reasons: first the to hot meant the amperage (total weld wattage) was more than needed so the molten metal would fuse to the bottom of the weld groove and not cold lap there. This ties the topsides to the other two pieces and insures that seam is full welded. Second the weld's travel speed was intentionally slow to allow more build up of material BUT.. mainly to allow an increased time for the gas bubbles to rise to the top of the weld and be blown off by the hot argon cover gas. Last the weld is too large in cross section because it will be ground off, sanded off, dressed off the top and provide a smooth transition from guard deck to rounded rub rail.

This weld was removed in the first few passes with an electric power plane, just like the kind used for wood. http://www.amazon.com/Makita-KP0800K-3- ... aner+1900b until the main crown was gone, but the planer was not used on the guard deck surface or the 1/2 pipe profile's shape either. All that was cut was the upper 80% of the weld's crown. Pan spray was used on the blades before they were started up, and the tool was held out from the work to fling off the excess grease before being let down on the rough weld top to cut.

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The gunwale seam between the 1/2 pipe rub rail and the guard deck (or sheer clamp) ended up clean off to a smooth surface. The weld crown was cut down after having been left intentionally to allow the weld to 'gas off' and have a clean root fusing the three sides and allow the weld to be sanded smooth on top. Generally MIG welds are not sanded smooth in this way as they tend to crack and split if the weld prep is not similar to that shown, and the weld put in with a seriously effort to add the heavy crown.

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The reason of this photograph of the 14'er tacked up and beginning to be welded is to show tacks. These small spots of welds hold the metal in position to be welded like tie wires in Stich-n-Glue plywood boat building. But they will leave several flaws in a weld if they're not prepared for welding by cutting the top out, cupping the body of the tack and generally thinning the tack weld so that it will be fully fused or completely melted into the final weld.

The first flaw left by tacks is the fusion of the weld just before and just behind the tack. The tack is thicker than the two parent metal parts being joined. So the effect of changing thickness is like turning down the amperage momentarily- lack of fusion or cold lapped weld.

The next flaw from tacks is the lack of cleaning under the tacks' edges where dust, water vapor, or other gas bubble causing contaminants are not removed- but if the tack is dressed down the edges will be cleaned and not cover the pollutants that contribute to gas bubbles in the roots of MIG welds. The last flaw is appearance; since the wire feeder is streaming wire into the arc cone and therefore into the puddle at a steady rate; if the puddle suddenly has a huge added volume the weld will be irregular at the tacks.

To dress tack there are several tool choices some already shown with at least one below. A router jig/base/fixture designed for the most common joints will allow tack dressing using router bits and the meat axe or grinder rigged with saw blades will do that job as well. Standard rigid grinder wheels for aluminum on a small grinder will also work to dress tacks but is often larger than needed and therefore results in sloppy cuts and tracks on all over the parent metal.

The last tool to include in this section is the die grinder both air and electric powered versions of the versatile tool exist but the air version is less often the choice of a small shop builder. Free air capacity required to run and air or pneumatic die grinder requires a fairly large compressor and receiver, and air drier and lots of hose. Most small shops don't have the capacity to effectively use carbide cutting tools in air powered tool because the free air capacity needed to keep these tools running at the correct RPM is too high for the air compressors installed in most small shops.

I'll concentrate on the electric version and bits that work well with aluminum. http://www.amazon.com/Makita-GD0601-4-I ... ie+grinder These tools will make very clean and controllable cuts in aluminum for gouging welds, dressing tacks and beveling short lengths in weld preparation.

http://www.amazon.com/SAIT-45073-Tungst ... inder+bits This link to a close up of an aluminum die grinding bit shows the main point to be sure in purchasing any die grinder bits. These teeth are just like the flat teeth on the Vixen file, widely spaced, sharp edged, and in this case spiral wound around the cutting bit body shape- this will help clear chips.

http://www.amazon.com/TUNGSTEN-CARBIDE- ... inder+bits The link to a Steel Cutting Bit shows the cross-cut teeth and what to AVOID as this bit will instantly melt the aluminum and coat itself with a layer of melted aluminum and not cut or cleanly cut aluminum alloys. Comparison given so you know what NOT to use, on aluminum work!

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This photograph of two weld ends, one a beginning and one and end of weld show the results of a carbide burr, like those linked above cupping the ends of the welds out. If you look closely, its possible you'll spot some tiny holes in the weld? Those are cut through sections of gas bubbles and are very common in MIG welding of aluminum; however the more there are the weaker the weld, and the better preparation, like cutting out starts and stops reduces the amount of porosity in the final welds.

Summary:
This post focused on cutting tools for edge preparations, weld prep both in joint shaping and dressing tacks or starts and stops. There are other ways to accomplish this work but these are long proven methods used by many builders and will work reliably if the techniques applied to correct tool choice are practiced on scrap while practicing your MIG and TIG welding before your build.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

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gap998
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Re: Notes on Metal Boat Building Methods

Post by gap998 » Wed Dec 09, 2015 6:11 am

Loving this thread!

Just to be clarify Kevin, I meant the jig might be overkill for wood boats that really only need turning once, (although the ability to turn at will would certainly be useful), rather than metal boats where it facilitates access & correct welding position.
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!"

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Re: Notes on Metal Boat Building Methods

Post by Kevin Morin » Wed Dec 09, 2015 9:07 am

gap998,
I'm glad the thread is interesting to you, sometimes when the Forum doesn't reply much (at all) you get the impression you're "preaching to empty pews"? I appreciate hearing from you.

I understood about the wood boat idea of only rolling once but with a Davis Jig a different method and idea of the traditional wood boat build can come into play. What if all the planks were put on the frames down hand? If the boat were rolled so each plank/sheet/surface was down, there is little or no side room needed to swing a plank, all the work can be at "shirt pocket height" and all the glue/paint/glass resin can be level not on the vertical, access or fastening and fitting can be improved like it is for the welding aspect of metal boats.

I agree, wood boats' construction isn't as super critical as a few seconds of welding that is worth positioning the entire boat to achieve, on the other hand; being able to roll the boat for all sorts of 'out of position' jobs is a huge gain regardless of material.

Cheers,
Kevin Morin
Kenai, AK
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Re: Notes on Metal Boat Building Methods

Post by psychobilly » Wed Dec 09, 2015 2:51 pm

Heck of a thread man! Beautiful hull too you have there. I bet she handles well.

I have a lil Miller and I have tried aluminum welding too. Not too good but I can say I have picked up some tips from this thread. Can't wait to try some more welding now. :D

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Re: Notes on Metal Boat Building Methods

Post by Soloboat » Wed Dec 09, 2015 3:25 pm

Just so you know I think you have a full house I am following with keen interest I may try a skiff in the future however I have welded steel and I remember you commenting some time ago that It was easier to teach a new a guy how to do aluminum than it is to retrain a steel guy. Keep going you have an audience and, if not specifically for aluminum then one may extrapolate and use this info in various applications.
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