First-And-A-Half-Portrait Done

[catsittingstill]

I finished the drawings for the Binturong design today.  The last set of drawings I did all the stations on one piece of paper, but in my opinion that ended up rather busy and hard to interpret because some of the lines crossed each other.

This set I did one piece of paper for the middle station and all the stations forward to the bow, and the bow stem shape.  Doing them all on one sheet of paper worked out well, in my opinion, since it makes it easy to see what height each should be.  Boats are often a little deeper in the middle than at the ends, while the gunwales are a little lower in the middle than at the ends.  Which means when I set up the mold, I need to not only have every station the correct shape, but every station the correct height above the strongback.  Drawing them all on the same sheet with a common waterline (especially along with the bow and stern stems, which will be tallest) ensures that it is easy to ensure they all end up the correct height relative to each other on the sheet--then I draw one "top edge" and it goes to all of them, and when they're all flipped upside down and bolted to the level strongback, everything ends up the right height.

I did a second piece of paper for the station behind the middle station and all the stations back to the stern, and the stern stem shape.  The table was big enough I could tape both sheets of paper on side by side, which made it easy to transfer the waterline-to-top-edge measurement from the first sheet to the second.  I have decided to go with my eye-stimate for the stern stem shape--I played with it a little in Bearboat and it didn't seem to affect the CLA much at all, so I think it will be fine.  I need to think about the bulge in the middle station, which, after the tweaking, is not echoed in the stations before and after.  If time and skills permit, and people express an interest, I will try to put up pictures.

I did something clever.  It actually turned out to be more clever than I realized at the time, which is always nice.  I took the sheets down, I taped together enough tracing paper to cover each sheet and traced the station outlines onto it.  This is because I only drew half of each station (they're mirrored down the centerline--the left half of the boat is the mirror image of the right half of the boat, so rather than risk drawing the curve through the offset points slightly differently on the two sides, I elected to draw a centerline and only one half of each station.  When I transfer the station drawings to plywood, I will use carbon paper and a dressmaker's wheel on the drawing, then take its traced copy and flip it over.  It will be easy to see the pencil line through the upside down tracing paper (I may put a sheet of typing paper over the carbon paper for better contrast) and I will use the dressmaker's wheel to trace the other half of the station from the tracing paper.

This does make me wonder if the inaccuracy in tracing is smaller than the inaccuracy in french-curving-through-offsets.  However at least the inaccuracy in tracing can be seen while the inaccuracy in french curving can't.

Another good thing about the tracing paper is this makes it easy to compare the stations for the front of the canoe with the stations for the back of the canoe, so I can evaluate the asymmetry.  I meant it to be asymmetric but it's nice to be able to see how much.

The more-clever-than-I-thought benefit is that I can lay the traced sheets over the station drawings for other canoes and compare them easily.  For instance, I can see that the Bear Mountain Rob Roy design has bunches more rocker (no surprise--I'd noticed that before), and a much rounder shaped bottom, but I can also see that my design carries more of its weight at the ends.  I'm thinking this may mean that the Rob Roy would tend to rise over waves more and the Binturong will cut through them more.  Which may not be a good thing if the waves get too high.

There are a lot of things to think about.  But I think I can get all the stations from one sheet of plywood, which is good because plywood is expensive.
 

Comments

[keris]

Wow. OK, yes, I would like to see pictures because I only have the vaguest idea what you're talking about and can't visualise it (I just about caught the bit about aligning the waterlines, that seemed logical to me).

Spline ...

[(Anonymous)]

The use of a spline curve is usually better than French curves as the spline usually behaves more like the wood.

Using the half-pattern and flipping about the line of symmetry is an excellent idea - it really reduces the errors that you may find when making up the patterns.

Re: Spline ...

[catsittingstill.livejournal.com]

I have heard of splines, and would be happy to try one, but haven't been able to get hold of the ones that can be adjusted to hold their curve when one lets go.

I understand one can use a thin piece of wood as a spline but that would require two people--one to hold it to its curve, and the other to draw.