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In the beginning -- there was sawdust

Posted by Sandy 
In the beginning -- there was sawdust
October 20, 2015 02:57PM
These are a few blurry cell phone pics.

I made a 4x18 foot panel two months ago and then got diverted by summer. For that side panel stock I used 1/4" inch AA Marine Grade Fir. It's not good enough (not anymore, it used to be) to make the boat with. But it's good enough to make temporary plugs or forms with.

Now it's getting cold and rainy. Snow is on the way. Maybe I'll do a bit more boat building. This will be a 17' decked white water boat. Wider than most. Beyond that everything is up in the air. I'm designing this one on fly. Like I always do. With a full size model.

The plywood will make a plug or a form. Somewhat like a concrete form. The boat itself will be Plascore covered with glass--built on top of the form. I need to make a few test panels. I want to vacuum bag the Plascore (on one side only, probably the inside because it's easier to do good manual, in-place work on the outside) while it's lying flat. And then cut it up. Put it on the form. Glue the edges together. Tape over the seams and then maybe (maybe.....test panels must come first) spray on LIne-X truck bed liner. Thick on the outside bottom. Thinner above. We'll see. Maybe so. Maybe not.

The idea would be to get away with a lot less sanding fairing and painting. Just wop it together and have it sprayed. I like the idea. There could be problems. We'll see how it goes. The more I don't know in advance the more I like it.

I've had a set of "adjustable ribs" for almost as long as i've been boat building. I put side panels on the adjustable ribs and then fiddle with widths and side angles until it looks right. And then make the boat. But the adjustable ribs I've had all these years weren't wide enough for the 17 footer. So I had to make two new ones. I put one fixed trapezoid on a movable cart, which be at the widest part of the boat, at the middle. The two new (and wider) adjustable ribs go two feet either side of the middle. If I need any more 4 feet either side of the middle the old ones will be big enough.

I'm a retired programmer. So I'm not intimidated by complicated software. But I've never been wild about 3D boat design software. It's cumbersome to use and I never feel I know what I'll actually get by staring at a small image on a computer screen. Full size models, on the other hand, are indeed what-you-see-is-what-you-get. Full size models are the only way I'll ever try to design a boat.

This is a big boat. It's going to be a bit tight in my little shop for a while. At least until I can take down the 20' foot long panel construction table (built with 2x4s and chip board on top of saw horses).

I'll update this thread as the winter marches on.

Re: In the beginning -- there was sawdust
October 20, 2015 03:14PM
The chip board trapezoid on the cart above, that corresponds to the dead middle of the boat, has a bit more side flare than I've used in the past. Approx 30 degrees off vertical. That means I'll have to dish out the chine a bit. In order to reduce too much rocker. With a straight line chine more side flare creates more rocker. Too much rocker is just as bad as too little. Dishing out the chine with the ==> Bent Stick Trick <== is the easiest way to deal with a 'too much rocker' problem.

With the bent stick trick you don't need any advanced engineering mathematics. Just a long straight grained stick a little intuition and some trial and (not too much) error.

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