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Before the next ice age

Posted by Sandy 
Before the next ice age
April 26, 2016 10:20PM
I haven't done much with this project in months. But now that I don't have to build a fire in a dark shop I'm back at it.

How do you design a boat from scratch?
Build a 1/12th scale model and fiddle with it.
Make some side panels. The models helped to estimate how much to dish out the chine edge.

Mount the side panels on adjustable ribs with temporary stem and transom.
Play with widths and side angles until it looks right.

Now, at this stage I'm happy with the shape but it's far too crooked to build. So now I'll measure things up and write down temporary rib angles and dimensions, and replace them with 3/4" sub flooring plywood, with vertical centerlines drawn on the new plywood (but still temporary) ribs.

Then I can straighten it up from front to back. Then drape it with 4mil Visqueen and cover the form or plug with Plascore. Fiberglass it on the outside. Take it off the mold. Straighten up one more time and fiberglass the inside.

Build the deck. Etc.

The following plug will need a few more side-to-side spacers at the transom end--after straightening and before covering with Visqueen and Plascore. It's important to remember the Algonquins made birch bark canoes............that were good boats.

What counts most is getting the right overall shape. The right widths side flare and the right rocker profile. And to remember wider is better. The original Oregon boats were 48" inches wide because plywood was 48" inches. This one will be 64" inches wide at on the bottom at dead middle. Made from 18' foot side panels it will end up about 17' feet long end to end.

The 17x54 boats most people make (for a 17' footer) is the original McKenzie 15x48 boat scaled up proportionately. But wider is better. 48" was form follows material convenience, not form follows function, as so many have claimed.

Re: Before the next ice age
April 29, 2016 08:05PM
Getting there. Here the adjustable shaping ribs have been replaced with sub flooring plywood with vertical centerlines on each rib-like trapezoid. So a long straight 1/6 can be lined up to so the vertical centerlines all line up to one edge of the 1x6

This plug needs a little side to side filling in near the transom yet but it is level and straight. And all on a movable platform with wheels. Then make some 18' foot long 3/4" inch thick Plascore panels with two layers of glass vacuum bagged to one side only. Cut that up into pieces. Put 4mil Visqueen on the plywood form and cover it with Plascore.

Glass that up. Pop it off the form. Straighten up one more time and glass the outside. I'll put the pre-glassed surface to the inside. And vacuum bag the outside-------if I can figure out how to do it. Else I'll just hand lay the outside, as I've always done.

Re: Before the next ice age
April 30, 2016 08:00PM
One more detail. Now it's ready for visqueen and Plascore. Straight down the middle with all ribs parallel to the floor. Transom not tweaked. I've done this too many times to count. I have never once put a frame set together with stem and transom that didn't need straightening. The last step is always the transom, which is always always tweaked out of square. The way to fix it is to use a come along from the long point of the out-of-square transom diagonally across to the other side of the form. Crank on the comealong until it's right. Leave it there until the hull is built.

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