Page 4 of 6

Re: Notes on Metal Boat Building Methods

Posted: Tue Jan 19, 2016 6:05 pm
by steveh41
Kevin,

Haven't had to deal with lofting in quite a while, but I'm really enjoying following along with this thread. Have an old copy of Allan Vaitses' Lofting text which I used to take as the most concise reference on the subject until now. Many thanks for a very clear (and well illustrated) explanation of the process...

Regards,

Steve

Re: Notes on Metal Boat Building Methods

Posted: Tue Jan 19, 2016 7:08 pm
by Kevin Morin
Thanks Steve,

(at least) I'm making sense to someone! Thankfully. (well, someone who already knew how take these steps!!) I appreciate your remarks, hopefully well get "farther along" in this thread and explore some work methods that may not have been included in the Lofting Text?

You are very welcome for 'my version' of this basic info, thanks again for the kind words.

cheers,
Kevin Morin
Kenai,AK

Re: Notes on Metal Boat Building Methods

Posted: Tue Feb 02, 2016 6:36 pm
by Kevin Morin
Test post, just lost a rather lengthy post not showing up here; so this post is just a test to see if there are technical issues with my PC?

Cheers,
Kevin Morin
Kenai, AK

Re: Notes on Metal Boat Building Methods

Posted: Wed Feb 03, 2016 8:20 am
by gap998
I have lost posts in the past - sometimes the authorisation times out. If i'm doing a long post, I usually do it on Word first.

Re: Notes on Metal Boat Building Methods

Posted: Wed Feb 03, 2016 11:45 am
by Kevin Morin
gap998, I've used that method before; composing in the word processor and posting after the piece is ready. In this case, I usually 'preview' the posts regularly when composing online so I can confirm the images' locations, text and links.... that 'preview' process has renewed the link and renewed the time out re-log-in feature, but this time I guess I just blew it and left the post in preview and didn't up load?

Well, old welders' concentration is vague! I'll give another try.

Cheers,
Kevin Morin
Kenai, AK

Re: Notes on Metal Boat Building Methods

Posted: Wed Feb 03, 2016 1:40 pm
by Kevin Morin
Working toward building and using a plate model to give the shapes of the outlines of hull panels for our real sized welded aluminum boat; we've explored some drafting table methods of work, we've reviewed the idea of scale, curves and the descriptions of lines plans. On an adjacent post I've concentrated on Lines and provided some images there to help understand 'hull intersections' from the point of view of 'stacked sheets of glass' with lines that intersect the hull's surfaces.

Just above we began to look into the techniques using a dividers and drafting tools of making the Body Plan or Station Cards needed for a builder's plate model and in this post we'll continue that subject. The images may be a bit more dense in this post? The reason is, I'm trying to get all these different points on any given Station Section (placed onto a Station Card or a Body Plan) into one image so they're related to one another.

Image
This first sketch, above, shows three sets of dividers in each of Views. To the lower left, taking distances of Offset or Half Breadths from the keel plane outward are shown positioned over the Station Grid line intersections with the Hull Lines Curves drawn in Plan View.

The right of these dividers is an identical set of dividers, colored separately for clarity, shown taking off the Elevations from the Profile View. These dividers are shown with one leg on the new baseline, drawn for this purpose, and the other leg on the Profile View Curves' intersection with the same Station Grid line as those taken from the Plan view below.

All these six colored dividers are then shown MOVED onto the Station Card, the left hand images are showing the dividers 'taking off' the values as each is set for the distances shown, then on the right each one is 'laying down' that distance. All the Plan View values are horizontal offsets (half breadths) from the vertical keel line on the card, and all the Profile View values are elevations up the keel line above the baseline and keel line intersection points.

Image
Zooming in a bit, on the previous sketch, here above are the Plan View lines offsets from the keel plane outward, to the intersections of the hull curves with the Station Grid lines (we're working on Station #3, recalling these grid lines' numbers begin with 0).

From the right in this image; the larger pink divider is set to the elevation of the sheer, at Station #3 above the new baseline, gold medium size divider is set to the distance elevation of the chine(s as they' are both at one elevation) at Station #3, and the smallest orange-legged divider is set to the distance of the keel (meeting of the V of the bottom panels) above the new baseline. The baseline was added just to give a reference for the taking off of Body Plan intersections as elevations , it could be above the models lines and the distances measured downward, it could be lower with greater distances to lines in Profile, it was set arbitrarily for convenience only. There is no fixed location for this reference line in Profile View.

Moving left, the tallest dividers is blue-gray and is set to the offset of half breadth of the sheer in Plan View, the purple legged divider takes off the distance from the keel of the inner chine at Station #3 and the top of the blue legged dividers makes the tip hidden but is set to the outer chine offset from the keel. All these values will be laid down onto the Station Card as horizontal distances along the new baseline, away from the keel plane.

Image
This sketch, above, of the dividers all placed on the Station Card is intended to correlate their two groups (coloring and position) one from the Profile View on the left of the image arranged vertically up the keel line (since the keel plane is a line in this Body/Section View) from the baseline intersection AND all the Plan View dividers are arranged along the horizontal baseline so the will mark offsets from the vertical keel line in the middle of the Station Card.

Image
I hope this sketch will clear up and remaining confusion from the more complex images previously shown? The Station Card is shown with labels on the points of intersections of offsets and elevations drawn parallel to either the Keel Vertical or the Baseline Horizontal lines. All the dividers will have one 'zero' point at the intersection of these two lines on the Station Card, and all the elevation distances will be up the keel plane, where a horizontal line is drawn at each elevation; keel above baseline; chines above baseline and sheer above baseline.

The Plan view values or offsets from the keel plane will all have vertical lines, parallel to the keel line corresponding to each horizontal line off the keel. There will be a vertical distance of;keel to keel = 0; keel offset to inner chine; keel offset to outer chine; and keel offset to sheer.

When all these sets of lines are intersected (circled leader lines) they will show the Body Plan View, or Body Sections at each Station. By connecting the intersecting points on the Station Card, the cross section of the boat at the location along the Baseline (Station Grid) will be drawn to scale.

At this point in the discussion we will not explore or consider any camber to these Sheer to Chine (Topsides in Section) or Chine to Chine (Chine Flat in Section) or Inner Chine to Keel (Bottom in Section) lines. The hull cross section lines are drawn as straight lines, not cambered, to illustrate the Station Card construction and layout.

Now a few notes about this post. First, I'm working to explain a body plan and builder's plate model but this method of work will also allow you to take a set of paper lines plans and create a full sized working template for formers" (I'm not referring to permanent frames just temporary fixture composed of station cross sections that will allow you to build full size) so you could then take off the hull panel outlines, cut and tack up; and then fit the framing inside - in other words this method of 'take off' allows you to make a form off which to build accurately with the skin-first building method.

On the other hand, as I will show, this can be done more simply by doing all this work in small scale and only scaling up- to the full sheet sizes in the last step on the actual hull parent metal sheets. This will become clear in the next few posts as we move to the model.

What is the goal of a Body Plan?
Image
When you're finished you'd end up with a drawing like this one. Sometimes to make the drawing less dense, with fewer lines, the forward half of the Body Plan will be drawn on one side of the keel line (vertical in this view) and the after half of the Stations' Cross Sections will be drawn on the other side of the Body Plan View. I show both sides here because this View allows the overall shape of the boat to be seen from the bow.

In the Body Plan image just above, the Buttock Lines are shown from their forward ends as vertical lines parallel, but offset from, the keel plane centerline vertical. And above the baseline are a series of horizontal lines that are the end view of the waterlines or water planes, again they are parallel to the baseline so they are shown as lines in this view, they would become a set of 'stacked' curves in Plan View. The buttock lines (butt lines) will become a series of curves in the Profile View.

However, instead of stacking all the cross sections on one page or View; in the plate model we'd make one Station Card for each grid line in the Plan and Profile Views.

Any time, in any post, that you find errors, omissions, confusion(s) please post up, if you'd then note the quote or image that I've left vague I'll try to work with you to make clear my points. gap998, since you're familiar with lofting, please let me know if these posts are sequential enough to introduce this subject, its easy to skip steps, infer steps or 'assume' steps that leave out key information, and therefore fail to convey the work methods-thanks.

Now let's turn things upside down?

Cheers,
Kevin Morin
Kenai AK

Re: Notes on Metal Boat Building Methods

Posted: Wed Feb 03, 2016 2:19 pm
by gap998
You can sometimes get it back by clicking the back button after re-logging in; the post comes back but you stay logged in, so you can just press Submit.

Re: Notes on Metal Boat Building Methods

Posted: Wed Feb 03, 2016 2:50 pm
by Kevin Morin
Short post, just wanted to introduce this image of a 2nd new baseline. As if we don't have enough references in these sketches already, I'm adding another one so you can reread the previous two (illustrated) posts and look at the Elevations being taken downward from a baseline ABOVE the Profile View lines.

Image
The 1st of several images in this post, above, shows the 2nd, and newly added, baseline positioned above the Profile View lines plan. As we've seen in all the other methods of work regarding a Body Plan or a Station Card information.... the Elevation distances were above a baseline BELOW the Profile View but here; this baseline is above the Profile View.

The methods of work are the same but the Station Cards are drawn upside down. Elevations are still up on the Station Card but (now) the keel is upward as well. For our builder's plate model the boat model will upside down so all the work can happen "down hand" or with our hands on top of the work, not holding up the tools and sheets underneath a set of frames, and this is common in welded boats too.

For those who want to skip ahead here are images of a builder's plate model like we'll be building.

Image
The paper plans have been razor knife cut out of the paper plans, glued to plywood or particle board cutouts, one for each view. The Profile View is inverted with the new baseline above the lines.

Topsides panels will be in the Green areas; chine flats are tan and the bottom is pink- contrasting colors for clarity not suggested paint scheme!

Image
Once the two views (Plan and Profile) are assembled into a 3D Station Grid by joining the two pieces of wood;

Image
All the Station Cards are cut from their thick paper stock, and glued into the grid on their own Station Grid lines.

Image
When the Station Cards are all in place... the builders plate model is ready for use by the builder to 'take off' the hull panel shapes.

I'll go back and add the step wise increments so this process is clear but many readers will find this 'old hat' so I figured I'd confirm their suspicions in this post? To the sharp eyed reader... yes the blue lines plan shows the lines views differently oriented than the plate models' views cut and glued to the wood cutouts.

Cheers,
Kevin Morin
Kenai, AK

Re: Notes on Metal Boat Building Methods

Posted: Fri Feb 05, 2016 10:35 pm
by Kevin Morin
We've been working toward a builder's plate model to learn to created accurate hull panel outline for welded aluminum boats and we're now down to the actual working steps to create this model. Just above, the model's final form was shown but here I'll show the steps in case you're not seeing what that post implies?

We've taken the paper plans (or in the case of the plans being in a book; just a table of offsets) and scaled them up, we've faired the lines and intersections and have a larger scale drawing. Using the methods here above, you could loft on a piece of aluminum or plywood to a very large scale and further reduce line-width-scale-errors, that were discussed previously. Further as the lines set (drawing size) becomes larger battens have to scale up too.. large cross section battens - like 1" x 1" x 1/8" 6061-T6 aluminum extrusions are much more fair a drawing tool than smaller cross sections of plastic.

the following sketches are images of the paper drawing being cut with a razor knife, straight edges and battens so the actual large scale drawing is cut out of the drawing paper and used in the modeling process. If you choose to make a metal plate model (works fine but is somewhat more work) then the scribe and cut, then sand and fairing of each half of the drawing shown below will be from a set of lines laid down on aluminum sheet. I rarely take this amount of time as the paper and wood which follows will produce more than adequately accurate dimensions and shapes.

Image
I hope the first sketch, here above, is familiar? This is our old example set of lines (no Body Plan) on blue paper.

Image
In order that the examples and the model images match, I've added this step above. The bow is reversed, we could say the drawing is turned over left to right? IN this image I've trimmed all the Grid Lines, Waterlines, Baselines and various other drawing references to show just what will be cut out?

IN the Profile View (above the Plan) the baseline is trimmed even, then at both the bow and stern a vertical line is trimmed to the Sheer (forward-left) and to the Sheer aft (top of transom right). Then the bow stem, then following the forefoot of and along the keel to the transom up to the sheer, that is one closed shape with all the Grid Lines remaining inside this outline.

In the Plan view, the sheer outline and transom outlines are joined by the straight keel line (top edge of the plane of the keel is a line) so the outline is defined by the widest lines from the keel and the keel along the centerline.

Image
Stripping the labels, and reducing the image to black and white (most drawing paper isn't colored blue) this is what your paper cutouts will look like in a builder's plate model.

The scale of the model will probably depend on your materials but a 3" = 1'-0" or 1/4 scale is large enough to produce very accurate results up to 40's boats. I did a 40'er with that scale a plate model and the final hull, no framing just skin first building was 40-1/4" from the tip of the bow (inside plates' edge to edge fit at tack up) to the inside of the cambered transom plate. The 1/4" was adjusted by pulling put the bow plates. That boat was modeled 40'-0" inside of plate and was built to that figure (plus or minus 1/16th inch).

Smaller scales will work fine, what is important is to have clean cuts on the paper at this point. Scissors work great, razor knifes and for long straight lines paper shears will do a nice job as well.

Image
This last purely paper image, above, shows the two cut out pieces of the scale drawing in the orientation we'll need the plate model. But paper will not be stiff enough to hold the Station Cards with enough rigidity to take off the information all this work is pursuing. We need wood backers, metal will work too. I have done entire plate models of thin aluminum and they were very accurate but also took much more work than paper and wood.

Before we look at more model foundations let's review these steps.
The lines are drawn to scale in the Plan and Profile, hopefully to a fairly large scale to 'fair' and pencil width issues from smaller scale plans. Once drawn, the two views are cut out to the finest lines we can hold with the cutting tools used. These two pieces of paper will now be mounted to wooded stiffeners to hold the stiff while the rest of the model is assembled.

Image
In this sketch, above, a piece of particle board has been cut longer and wider than the Plan view paper cutout- which is now colored by hull panel region. The colors are there to help make all these 3D images a little more easily viewed. The thickness is 1/2 or more so there's no cupping, curving or flex in the base piece for the plate model. The edge that is most critical is the Keel plane (right side in this sketch) so that should be sanded on a belt, planed or joiner skived to a very clean edge. (A) thin film of wood glue, contact cement or light coat of paint will all bond the paper to the wood, which should be done in an entire area, not in spots.

Image
The next step in the model build is shown above. Notice the backing board for the Profile (which you will recall is inverted from a baseline above the original drawing, now put parallel to the lower edge of the backing board; ONE THICKNESS [base board's thickness] above that edge!) Once the paper cutout is glued to the blank backer; then cut the outline on the band saw, outline is the vertical at the bow, bow stem, forefoot curve then the keel, angling up the transom and finally vertically to the baseline again.

This should be cut with some spare, sanding back to the drawn line in the glued on paper drawing will give the most accurate edge for the centerline plane support. (this is the keel plane in the model)

Image
Before joining the Keel Plane to the Baseline Plane drawings using their wooden backer boards to form a rigid 90 deg model base; bevel the Profile View/Keel Plan board. We will be marking along the paper edge and the board will be in the way- so you need to put this backer board on the belt sander, router table, tip the band saw table... bevel this back as shown in this sketch. Note the tip of the sheer's vertical is beveled too to get the best access for marking tools on the model.

When the two boards with their paper drawing cutouts are ready, join them along the keel line and baseline intersection lines as shown. Biscuits, screws, nails, glue and clamps.. whatever method you use, the joint needs to stand up to some handling but no real structural loading.

What we ended up building is a 90deg corner of wood holding the two scale drawing cutouts with the lines of the Profile View inverted.

Image
Not sure you'll color your lines drawing pink and green (?) but this is what your model should closely resemble.

Next we're ready to make and install the Station Cards.

Cheers,
Kevin Morin
Kenai, AK

Re: Notes on Metal Boat Building Methods

Posted: Sat Feb 06, 2016 12:23 am
by Kevin Morin
The plate model is coming along but its only partly 3D -and only a 3D model of the boat will allow us to define a hull panels' outline and that is what we need to learn.

The Station Cards have to be added into the model frame for it to become 3D and allow the plates to be 'developed'.

Image
The first sketch in this post, above, shows a Station Card fit to the Station #3 (there's one on Station #1 as well. for the super observant, you're right this set of lines is different than the 'blue sheet' examples soo.... Station 0 is too far forward.. but please ignore that! (All the principles will hold true for any set of hard chine lines.)

In this image the Elevations 'above' (the inverted) Baseline are shown. And each distance is the source of a horizontal line heading outboard, at the Sheer, which is elevated so we can work on that point, the Chines which are flat (no deflection of that hull panel in this design) and the Keel which is the edge of the outline of the frame of the plate model.

Image
The next image is identical for object and model content but the annotations show the Offsets (half breadths), and hopefully you'd recall from a few previous posts that the offsets would be verticals from the Plan view? Here I show the lines from the two views coming together at intersection points of : sheer, nearest the model base; the vertical line intersects with the sheer offset and that point is an angle corner of the Station Card cutout. As the boat is inverted, next, inboard along this Station Card are two verticals leading up to the two chine points as they intersect with their Elevation above the baseline. Finally the tallest point is on this Station Card is at the keel plane or the right side of the model's frame.

This method of creating each Station Card can be done from the paper drawings shown before they're cut into outlines for the plate model, OR using the dividers along each edge of the Station Card that has been cut and sanded to an exact 90; the distances can be 'ticked' along each edge and a tri or machinists' square could be used to create the two sets of right angle 'extension' lines ending in their intersections.

AS with the previous Body Station Plan post, connecting each set of points on all the Cards will give a cross section intersection of the boat's hull surfaces with a plane passed through the entire boat at even divisions along the keel plane.

Image
This image, above, shows the Card all installed. I use hot glue gun like welding to install these cards. Mounting board, presentation matting, 1/16th stiff paper will work to act as Station Cards. Glued on the Base (Plan View) and Keel Planes (Profile View) axis will keep this stiff paper strong enough to do the next few steps with little error due to the flexibility of any given station bending fore or aft.

So what is it that we need from this plate model?

Image
This last sketch in the post, above, shows the information we're trying to locate and lay down flat. This is the topsides panel of the model - to make things less dense, the image is of the Station Cards topsides intersections (only) and the outer chine connected long the upper line with the sheer at the top. (recall the boat is inverted?)

So we need to define this surface, unwrap it, lay it down and mark that shape in a sheet of real size aluminum.

gap998, if you're still following this thread? I like to know you see the steps are clear enough for the new builder? Anyone who'd like to remark or ask questions is welcome, I hope this thing is plugged in? tap, tap , tap.

Cheers
Kevin Morin
Kenai, AK

Re: Notes on Metal Boat Building Methods

Posted: Sat Feb 06, 2016 12:27 pm
by Kevin Morin
All the model images, so far, have been in the orientation of the working techniques, with the keel up, and the sheer down, but the sheer is elevated by the (2nd new) Baseline being elevated above the sheer line Profile View. To see what the plate model looks like in a little more conventional manner, let's look at the model at this stage, hung from the base- or Keel down.

Image
This short post's sketch shows the model at this stage, but turned over to show the 'boat' in the model. Notice that some parts are identified including a drafting error in my illustrations. Drawing these models in 3D curves is not all that agile in the SketchUP environment and I'd gone so far along that switching to Rhino, that has the tools, wasn't appealing so the chines are hogged at the station where they should be smoothly tangent curves to the rest of the after chine lines- that is labeled in the Sketch.

Won't hurt the methods of our work, and would have been avoided in your own work by fairing the lines of the Profile and Plan and then accurately taking off the Body Plan (Station Cards) to reflect the two other views' fair lines.

Does the model look like a boat? Well, half of a boat? I hope so.

The next few ideas we'll need to explore move away from the model for a some images that express ideas related to the modeling steps next in order. One idea that may work well enough in words is the concept of the difference between the modeled boat and frames or inverted real sized transverse frames of a metal boat.

If your frames are already made, spaced, plumbed and ready for sheeting its common that a tests for fairness happens before the sheeting begins. The question of the builder at this stage of the build is: are any of the frames' edges NOT on the surface of the hull. Are the frames' edges higher or lower than the hull surfaces as defined by the rest of the frames' edges? Suppose one or another of the frames' edges were protruding out of the surface, or were recessed below the surface of when compared to adjacent frame edges?

In other words both in the plate model and in the real set of frames, small variations of the frames' edges may hold the final sheet off of adjacent frames, if one frame were outside ('proud' of the surface) the designed surface and likewise, a frame's edge may be inside ("shy" of the surface) of he plate laid fair to the model or the real frames.

This is a common building exercise in wood frames, and by laying battens on the hull in different aspects to the surface being faired- high and low (proud and shy) areas of the frames' outer edges can be discovered and corrected. In the case of wood, a bit of sanding on proud spots and perhaps a laminated strip along a low area that was then sanded fair to the surface would cure most of these problems.

However in metal only the proud areas can be addressed easily. Shy or low areas in the frames' edges (not true of the model) in metal require other techniques to address since welding on the edge of a frame to 'build' up the metal's profile or depth - isn't as straight forward. Welding on the edge of a plate or sheer to build up the 'shy' areas of a frame will more than likely warp the frame, leave a Weld HAZ, and otherwise 'make work.

If the frame area is low in metal framing; the methods to correct are usually to sister as strip of metal to the frame, where the added strip/bar/extra frame edge piece has the correct shape bringing the shy are up to the surface and TACKING only this piece to the frame. Welding would come later in the build.

Another method of 'bringing up' an area of a frame that is shy is peening. BY holding a large 4-5lb hammer head behind a flat bar along the edge to be raised and then using a ball peen hammer to put dimples along the edge, some expansion of that edge will occur and that will bow the bar in the direction of the hammered edge. This method will work on 2-4" wide frame bars but after that loses effectiveness and is only useful for shallow shape changes on the order of 1/8". The stretched edge is forced up (the direction of the correction) in a bow by the 'green metal' edge or the undisturbed edge remaining original size. The peened edge is thinned slightly and expanded end to end and therefore it will bow to toward the hammered side of the bar.

The last method is to push the longitudinals (bars, angles, T's) outward at the low/shy/inside frames or areas of frames and simply do not attach that section of the transverse framing to the hull sheeting.

The plate model's frames should all be fair to the next two frames adjacent if there are any high/proud frames, or low/shy frames' edges they can be trimmed by a fine sanding paper on a small block to remove proud areas and build up by replacing the Station Card or by 'sistering' or adding more card with a better outside profile as shown by the adjacent frames, or if the amount any card edge is shy is low, ignored in the modeling stage- but should be addressed if you were reading this as a reference to the full sized frames of your own metal boat.

Let's look at how to make a model or framing check and see how that step can be done, but we'll need to look at the relationship between bars and wider plates first so the follow modeling steps relate to these fairing steps as well.

Cheers,
Kevin Morin
Kenai, AK

Re: Notes on Metal Boat Building Methods

Posted: Sat Feb 06, 2016 3:06 pm
by Kevin Morin
Any strip cut out of a sheet of metal can represent the entire sheet/plate in developable sheet modeling processes. A strip of metal cut off the edge of sheet can act like the whole sheet in modeling and fairing. Any strip of metal cut out of the interior of a sheet can act like the entire sheet too.

So can a strip cut at an angle diagonally across the sheet, as long as the strip's relationship to the original sheet is recorded- you can recreate the original sheet with great accuracy. This set of facts is what will give us a low labor high yield patterning method from the plate model.

Let's go through some introductory images to get a sense of using a strip to represent or pattern a sheet of metal. The steps are to put the pattern piece on to the sheet and mark (take off) the grid lines, then record distances onto the pattern (all this is taking off). To reverse the process, (laying down) put the pattern, or take-off strip, onto new material and reverse the process. First, draw the grid lines or recreate them (lay down the grid) then mark the taken off points (offset from the pattern's edges) and mark (lay down) those distances long the grid lines; connect the points now located on the new sheet material and you have recreated the original shape. Its that simple, but before we don that on the plate model with its Station Card edges, lets do some exercises flat on the bench or drawing table?

Image
This is a sketch (above) of a 4'x20' sheet of aluminum and a take off strip of 8" x 25' (any longer length will work, length becomes important farther in these examples) which will be used to take the pattern off the rectangle.

There are grid lines breaking up the 4x20 at 1/3 & 2/3's the length but there could be grid lines every few inches; the results will be the same if the method is followed closely.

Image
In this second sketch, the take off or pattern strip is now over laid on the 4x20 sheet, the bottom edges are common and clamped. Then the grid lines are transposed from the 4x20 to the pattern, in this case that is just four lines; the two ends and the two middle grind lines. Next, each outline point is noted on the take off pattern piece.

First the two end corners on the Base or Reference line are along the actual pattern piece's lower edge. Next the lower to points in the center grid lines are also along the pattern piece's common edge. So four of the points are already located on the pattern by the transfer of the grid lines.

The upper four points are 4' along the grid line FrOm the bottom edge! Not from the top edge, that would only be 48" - 8" strip or 40" from the top edge. The distance can be taken from either edge of the pattern, as long as the measuring methods are repeated in taking off and laying down, things will work out well.

Image
Previous sketches showed the process of taking off the information of the 4x20 plate we're trying to 'recreate'.
This image shows the process of recreating that shape using the take off strip or pattern piece. In the upper part of this sketch the pattern piece has all the information that will be needed to recreate the entire shape. There are grid lines that will be recreated on new material and distances along those grid lines to lay down the points that will be connected to form the recreated shape's outline.

Lower half of the sketch shows the pattern strip common to the new sheet material (not shown in outline) and then the grid lines recreated using the pattern to line up the new and longer lines; then measuring along each grid line, up from the bottom of the pattern strip/take-off bar a 4'-0" dimension is marked on the grid line.

So the pattern was put on the original, grids taken up and distances along the grid were taken up too. Then the process was reversed, since the pattern had a common edge with the original material, one side of the newly drawn plate will be drawn along the take-off strip's lower edge. Finally distances along each grid line were put down on the new material.

Image
Last image in this post shows the recreated sheet outline based solely on the pattern's taken off information laid down on the new material. By making notes on the patter strip while taking off the shape of the patterned original the corners could be noted, and intermediate points noted. Finally by connecting the corners with straight lines and even checking diagonal dimensions an accurate copy of the original can be drawn on the new material.

If the original had been 4" x 20" or 1"= 1-0" in scale... this method would still work. The information could have been taken off a scaled down sheet and used to accurately redraw in full size.

We need to expand on this method and move the take-off or pattern piece a few times before we have a method that will work on the plate model.

Cheers,
Kevin Morin
Kenai, AK

Re: Notes on Metal Boat Building Methods

Posted: Sat Feb 06, 2016 4:10 pm
by Kevin Morin
Just above we began to look at patterning methods of sheets, or models where the pattern could be scaled up in one step to real size.

Here, we'll continue exploring work techniques to expand the methods available for your modeling or full size boat frame patterning of the hull panel outlines.

Image
This first sketch of the same 4x20 sheet (in scale or real size) is to recreate an accurate rectangle using a strip of the same material as the 'take-off strip' or pattern piece where a bar of 8" width is used to create an accurate pattern of a 20' piece of metal.

The upper image shows the pattern now located at some random location on the original. It would be clamped on, grind lines drawn over the surface fo the pattern and dimensions taken (written on the take of strip or in a table of offsets) and then the pattern would be removed.

Notice below the pattern is now put on a larger sheet, NOW SHOWN, and the grid recreated onto the new stock with the dimensions along each grid line. But the difference is there are to and bottom grid lines, and therefore two distances, one set above and one set below the pattern piece/take-off strip's edges.

Image
Just as shown in the previous post- here above- once the pattern piece/take-off strip is clamped to the new material then grid lines are projected above and below the strip's edges. This was not needed before (previous post) because the strip and the original had one edge in common. Now the take-off strip was taking up information from the middle of the original sheet. So... the grids and distances have to reproduced exactly as they were taken off.

Then corners were noted on the pattern/take-off so the end grids are known, the fact that the distances along any grid line are not even makes no difference to the final outline if the distances along ANY given grid line are reproduced.

Here the ends are drawn in, and the top and bottom lines of the sheet connecting to the distances along each end grid; give us the rectangle of the original shape, reproduced even when the take-off strip is not along one side.

Next, we'll angle the take-off strip and redo the same exercise.

Cheers,
Kevin Morin
Kenai, AK

Re: Notes on Metal Boat Building Methods

Posted: Sat Feb 06, 2016 5:28 pm
by Kevin Morin
Any bar is like an entire sheet if the bar or strip of metal is in the same plane or surface as the full sheet, in that the bar represents a true shape taken from the middle of that sheet. However, a strip of metal is not the shape of the outline of the bottom, sides, chines or transom. So we still need to refine some techniques to get the hull panel surfaces off the model accurately and we're not concerned with as single strip out of the middle of a hull panel- we want the outline in curves.

Before we starting taking outline shapes off the plate model we need one or two more exercises, this one is like the two previous but the pattern strip or take-off strip is at a diagonal to the original shape.

Image
The sketch above shows the pattern or take-off strip now at a diagonal and not even touching the two ends or the rectagular 4x20 sheet. Not a problem all that is needed is the same exact methods used before.

We draw the grid lines onto the take-off strip. In the case of the two ends, some straight edge tool will be needed- AND most important will be the use of the tool and marker to make sure the line of the end of the sheet is not one marker pen track off to one side or the other!

Also notice that two edges of the main sheet's top and bottom edge are there for reference too? Draw those onto the take-off strip's top surface.

As the two previous examples of taking off using a strip or pattern piece; measure the distances along each grid line to the outline of the original object shape, and note them as above or below the near edge of the strip used to take-off this shape.

Image
This image has some extra info show. The blue strip is all that matters at this point but I wanted to add the grid lines, and some notes to show what the pattern strip will look like, but also to correlate those grid line and sheet edges from the pattern's to surface to the next step.

Image
This last image in this post, above, again draws the same 4x20 rectangle sheet of aluminum using a entirely new set of information taken-off by the diagonally oriented blue pattern piece.

Again, following along each grid line for the correct distance above or below each reference edge of the take-off strip... points along the perimeter of the original object are now put down on the new material, once connected as corners of lines, and points along lines, and in this case even a very helpful line segment that was drawn on top of the pattern all allow us to reconstruct very accurately the shape that was taken-off or patterned.

Summarizing this set of three exercises; if a strip or bar of metal is laid on an area of sheet metal and a grid from the original metal is transferred or taken-off the original, along with distances along each grid line, then these points can be replicated using the pattern on new material.

It does not matter what path or angle or diagonal the pattern piece is to the orginal or the final piece of material... if the grid and dimensions are accurately recorded, they can be accurately replicated on the flat of the new sheet material.

That of course, is the key to the builder's plate model work method. But before we look at that, lets do one more exercise coverting the newly introduced method into 3D from the flat examples used so far.

Cheers,
Kevin Morin
Kenai, AK

Re: Notes on Metal Boat Building Methods

Posted: Fri Feb 12, 2016 3:32 pm
by Kevin Morin
I've made some Rule of Thumb statements about bars representing entire sheets of material and tried to prove that with illustrations of a 'take off strip' or bar being used to pattern a rectangle. In the examples of the previous post the same bar could be used in different references to the sheet being patterned and if the take off (taking up) method was observed and reversed as faithfully; putting down the reference points and connecting with lines (our original in those examples were all rectangular shapes composed of straight lines) - the result was a fair version of the original shape.

This method will work for any shape that sheet of aluminum can be cold formed to assume. For example, the developed surfaces of a boat's bottom or sides. We have skipped the determination of developed surfaces and are relying on the designer to have drawn a set of Hull Lines, in three views Body Plan & Profile that described a hull which can be formed of cold wrapped or un-stretched sheets of aluminum.

The un-stretched sheet of paper, plywood, steel or aluminum can form any of three geometric shapes; #1 flats, the native plane of the milled sheet material. #2 a cylinder or section of a cylinder- where the entire sheet or some portion is aligned to a line that is the center axis of the cylinder; and #3 a cone or conic section like the bow of planing boats both above and below the chines most often derives from some conic section.

Therefore: a strip of the same material can represent the shape of the entire sheet of the hull panel's outline if that strip is held to the frames (Body Section Plan; Station Cards of a plate model) and marked to take off the Station's Lines of intersection the distances.

To illustrate this idea, by why of introduction before we do the steps with the plate model, here are a series of images to bridge what has been shown with those methods of work applied to the plate model or Station Card model.

Image
This image of a rectangular sheet of material shows the take-off strip aligned across the middle and reminds that the grid would be shown on top of the strip as well as distances above and below, ends noted and any other details that were needed to help recreated the original shape.

Image
This sketch,above, shows the same panel and take off strip as the previous image but viewed from the right end where the cylindrical shape can be more easily confirmed.

Note: the arc distance along the sheet face would be longer than the chord or flat distance from the strip to the edges of the cylindrical section BUTT they'd be recorded or 'taken-off' from a distance along the grid line- so the final shape would measure enough wider (offset over the chord's length PLUS the arc's added fraction) so a 'true length' along the frame or grid's intersection with the final sheet will be taken off by the pattern strip.

Image
Taking the next logical step, above, this sketch shows an irregular and curved outline to a cylindrically cupped sheet. This instance, with the original item to copied or taken-off (take up) has curved edges and therefore when the points are laid down, they will require a batten to connect the points in fair curves.

However the same method of work will apply, step by step, the exact techniques shown for the first example in the previous post, or any example leading to this one, will apply here too. Record the grid, the distances along those grid lines to an intersection point and reverse the all those steps on the new material; however in this case instead of using straight edges to connect the various points battening curves will be used.

Image
This last of four images that bridge to the plate model images (following) moves the view point to the end of the previous image's panel and confirms the shape in cross section of the panel. Again, by taking off distances along the face of the grid lines, the trued outline of the final shape will be recreated by the modeling or pattern taking technique in these sketches.

drum roll...

Image
Here is a review of the builder's plate model so far, also called a Station Card model which is like the framed up boat (shown keel down)

Image
Another review sketch- this set of topsides intersections with the Card's edges (Station Cards not shown for clarity) is the shape we want to outline.

Image
This image of a take off strip on the model shows how the method of work applies to the builder's plate model. By laying the strip flat to all the frames' edges, marking the stations as a grid on the strip then measuring along each StationCard's edge to the chine or sheer the entire sheet's outer edge curves can easily be taken off; to be accurately laid down on a blank sheet out of which the full hull panel will be battened fair and cut.

Image
Above, the builder's plate model inverted, again, so the strip's orientation can be see from another point of view.

The gridlines drawn on the pattern or take off strip are the frames/stations/sections' edges as they touch the strip and the distances are above and below the strip's edges to the chine or sheer.

Image
What will the points look like when they're put down? Above is the strip (left) and to the right is the use of the strip's pattern information. Notice the grid lines of the points on the outline of the hull panel are not all vertical to the sheet, but the are lined up with the strip's orientation to the original Station Card model .... and we know from the first post on this method that the orientation doesn't matter as long as we keel the grid (Station Cards') edges marked for redrawing on the final material. We also know that the distances, even if curved on a cylinder or cone can be relied upon since the bar/pattern distances were taken along the egdes of the grid lines -an in our case shown above, the grid lines are the edges of the Station Cards of the model.

Shown here all the points are battened to connect in curves, but the bow stem and the transom lines are just projections of set of intersections of them model onto the strip. These two lines may be curved, cambered, bowed but the line on the strip will record that section of the pattern, other techniques may have to be used to determine how to recreate a curve if one is shown on the plans?

Image
how do you 'record' the curves of the outline pattern so they can be reused? How do you work to repeat the panel in the future or keep the same curves for reference? Here is an simple method of laying a grid that is 90deg to a blank sheet onto the curves of the topsides hull panel. Notice the original pattern lines or Station Cards /Formers/Body Sections grid lines are shown to confirm the modeling process will not return a 90 deg grid to the new sheet. However the patterning process will take off an accurate shape of the sheet required to meet edge to edge with a hull design of the model.

The builder's plate model in a 3"=1'-0" scale can be used to sheet hulls at least to 40'-0" LOA, as I have personally used a model of paper and wood, shown above, to take off the hull panels of that size boat. I ended up accurate to one sheet thickness in length and less than a 1/16" in beam and the boat was build skin first followed by main bulkheads, fit to the shape not lofted. I have made skiff this way for a long time, to avoid the labor of framing first, but even if you use a frame first building method(?) this method can be applied to both a plate model or the full sized frames to find the shape of the outline of the main hull panes.

If you have a set of frames already for sheet, this method of 'taking off' the full sized hull panel outline will work very accurately if the steps are accurately repeated and the strip is well and firmly clamped to your frames.

This method can be used (as noted in a previous post several above) to fair the frames as well. Notice that a hull thickness flat bar laid as shown in these images will represent the hull sheeting? This will reveal several aspects of your hull frames' outer edges- higher than neighboring frames and lower than neighboring frames.

Last, relating to this aspect of a plate model; is a review of the discussion of chines or longitudinal hull seams. Mr Hankinson has an article on the site about aluminum boat building and he reviews some of the various chine joints possible. I recommend you find and read that article to explore some of the implications for the chines' fit in respect to chine flats' outer edges OR in the case of a single chine the topsides to bottom seam's design in section. Some of these joints would require an overhang at the chine, others may require other allowances.

In some of Mr Hankinson's designs, he shows a large diameter round bar to weld both the topsides lower edges, and the bottom's outside hull panels' edges. This chine bar is only needed if your work is not refined enough to fit the two sheets to other joint designs. The round bar has an upside- wide target, huge weld sink for low skilled builders, but... the down side is the large heat sink makes good welding harder and putting the bar on 'fair' is a big job because once in tension along the chine point of frames; heat distortion from tacking is hard to avoid. (Catch22 of chine bar; to get weld hot enough to hold huge bar- heat is enough to allow bar to bend unfair but... an if the welds are cool enough to keep bar fair, it may not be held to the frames adequately to stay put while patterning hull panels.

LAst about chine bars, I think they were shown to reduce error by inexperienced or low skill builders, now you have clearly shown, adequately illustrated methods to allow fitting to at least 1/4 of any sheet thickness (this thread) the better joints would be those explored in Mr. Hankinson's article about welded aluminum boat building. The most simple of which is an inside edge to inside edge seam I've shown here and on the adjacent threads about working and planning in welded aluminum.

I'm pretty confident that if Mr Hankinson knew his plans buyers and future builders would all read these posts, practice the work methods shown, and apply the trade craft reviewed here; he's say you could skip the chine bars and go with sheet edge to edge joints without any hull compromises?

As usual, I welcome questions, please note where and what text I've goofed up? What image makes the information here confusing and I'll try to help make sense of what I confused!

This method, shown above is not very agile for chine flats and so we'll start to explore a method that lends itself to that surface. The same method will be a basis for outlining and cutting forward hull longs that may be so tight in curvature they have to be rolled, formed or cutouts?

Cheers,
Kevin Morin