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pirogue building form

jdupre'

Well-Known Member
Sep 9, 2007
2,301
40
South Louisiana
Someone commented about the form I use to build my pirogues. I use this form on all my 3 panel boats. I got the design from my neighbor over 45 years ago when I built my first pirogue. It's pretty simple......one board with the proper side flair angle and bottom width and two clamping uprights glued and screwed on. I cut out the bottom corners for clearance of the chines. Bottom width can be adjusted an inch or so by raising the clamp up the sides. I like a single form because it allows the wood sides to bend into a fair curve with no fussing around with several forms. If I want fuller front and rear sections, I just spring in a temporary spreader bar where needed. Is it as accurate as a strongback with several stations? Probably not, but with a little careful measuring and centering, it's plenty good enough for my use.

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oldbuffpilot

Well-Known Member
May 13, 2014
553
22
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Central Kansas and Central Texas
Joey,
First thanks for this post, I asked about the form when I saw it in one of your pictures and thought what a great idea. This morning a more complete explanation really solved some problems I’ve been having when building without plans. I had never considered that using only one form would let the boat fair itself, but thinking back, the last build thats what I did when the front form didn’t look right. I've built a lot of small boats from plans or by slightly modifying plans, but building by hand and eye toward a boat I’ve envisioned has been a whole new game and a lot of fun. I used to say I’d rather fish than build, the years are changing that! I still love to fish isolated by myself but it’s getting harder to do and this building without plans helps keep me busy. Nice day in Texas, I think I’ll go fishing!
 

beekeeper

Well-Known Member
Mar 4, 2009
1,824
50
Using the form to shape the boat by hand and eye is probably the best way for your method of building. Some builders use two forms to fair the sides if they are building asymmetrical. Your "spreader bar" sorta fills that roll. I would keep an eye out for the bar changing the sheer line and maybe not the chine line. They may not follow the same curvature. I'm not saying the two have to be the same just that it could happen.
A strongback works best for set dimensions and is not easily adjusted on the fly. I use mine as a support platform and to set the rocker with my backward/different way of building.
Question; If you leave the form at the same point on the sides and move the clamps to adjust the floor width, the width can only be reduced? If you moved the form to widen the bottom then the form would protrude below the floor, yes/no?
 

jdupre'

Well-Known Member
Sep 9, 2007
2,301
40
South Louisiana
Yes, if you move the form to widen the bottom, then the form will protrude below the floor. Easy fix on the fly, though. You could just cut a plywood shim for each side and lightly tack them onto the bearing surfaces of the form. Same thing if you want to change the flair. Tack on a tapered shim on each side. Really, it's almost as easy to make another form. Might take all of 10 minutes.

By the way, I'm trying something a bit different on this boat. Flair is reduced to about 22 degrees with a 24" bottom. That should make the boat sit a little lower in the water, giving me a little lower center of gravity and a narrower waterline width. Just a less severe version of a lead keel on a sailboat.
 

beekeeper

Well-Known Member
Mar 4, 2009
1,824
50
Would reducing the flare of the sides reduce secondary stability? If so, will you have to lower your seat to compensate for the increase in the tipsy feeling? I'm sure it will work for you. That is pretty standard dimensions for pirogues.
 

jdupre'

Well-Known Member
Sep 9, 2007
2,301
40
South Louisiana
Bee, that's one of those "it depends" situations. Reducing side flair slightly increases the draft, so it slightly lowers the center of gravity. A lower center of gravity, on paper, increases stability. I'll have to work out the seat height for my individual taste. The only boat that I had problems with stability was the one Piper gave me. That one only had 16" between the chines and a MAX beam of 19". Mighty twitchy! I've never run into stability problems in any boats in the 22" - 26" bottom range. Getting in and out is a little trickier.

I don't stand to fish, but if I did, a 28" to 30" bottom width would be my choice. That would dampen speed and handling, but there's no free lunch in small boats. In the end, I'll give up some stability and speed for a boat that is light and handy enough that I'll actually USE it. The "perfect" boat that stays in the shed because it's too cumbersome does me no good.
 
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