> I'm wondering about the merits of strongback designs: Gilpatrick shows a
> strongback that is shaped like a ladder (built of 2x6 lumber sides with
> 2x4 "rungs") laid across sawhorses. The other books describe a
> box beam construction from plywood, and you build legs to support it.

> Your thoughts/experiences about which is better? Other designs? Drawbacks?
> Things to look out for? I'm not looking to build the "ultimate
> strongback" . . . ease of construction . . . versatility (if I build more boats, I
> only want to build one stongback), and functionality are the key.

> Thanks --

> Julie

Julie,

For your first canoe go with whatever strongback style the designer of your plans suggests. This will save you from some needless headaches trying to get the forms to fit on a strongback that they were not meant ot fit on.

If you look in the back of Gilpatrick's book and examine the drawings of the forms you will see that they consist of two design elements. One is the shape of the hull at that point, and the other is a shape for mounting it to the strongback. If redraw the plans to lifesize and cut them accurately you will find they line up on a ladderback strongback very quickly. If you use some other type of strongback you may have to recalculate the shape of each of these forms. Or, you can trim and then shim to get these things to line up.

The cost of the strongback is modest, so time spent cogitating on optimizing this part is probably wasted time.

As I recall, Gilpatrick's canoe plans include some for a boat that is over 20 feet long and 45 inches wide. Anyone who wants to build a boat that wide on a strongback that is basically a single 2x4 or 2x6 -- no matter how well it is supported against sagging -- is welcome to the chalenge. Personally I think I'd be fighting to keep the thing upright with even the more usual 30 to 36 inch wide canoes. Since the boat is so wide, a ladder-shaped strongback, set under the forms, makes the most sense.

On the other hand, with a kayak there is a lot to be said for using a strongback that runs right through the middle of the forms. This permits you to flip the boat over to work on the deck. the strong back is buried inside the boat components for a while, serving more as a spine than a strongback, but it is removed before the deck and hull are permanently attached to each other. Some designers string the forms along a single 2x4 or 2x6, and use supports along the length to prevent sagging. Others go with a beam that has a larger cross-section.

As for reusing the strongback: A ladder-style strongback made with 2 -- 16 foot long 2x6's for the sides, and some "steps" of 2x2 or 2x4 pieces, can be knocked apart in a matter of minutes, giving you back those long 2x6's for use as long, single beams. The only waste is on those short "steps", but with 2x4's selling for around $2 each, you'll only be losing about $4. Or, if you build a boxbeam for your first strongback, you can just build another one like it, and connect the two with 'steps' to make a ladder-style one later on.

But for the first boat, go with whatever style your plans call for. If you like the boat you may later build another boat by the same designer. The odds are good that this second design will be drawn to fit on the same strongback you used for the first boat. I guess designers like to go with what they are used to.

The most important thing about a strongback is having a sew straight lines down it for alignment. Some carpenters ( and some older plans) call for snapping a chalkline. not can bsomeone has already described a better method. Stretch a string and lightly mist over it with some bright spray paint. Removing the string leaves behind its bright 'shadow', surrounded by that bright paint. Since the string is not moving ( as a chalkline would) it preserves a sharp, straight durable image.

Hope this helps.

Paul G. Jacobson

p.s. I built Gilpatrick's "Puddleduck" and it is a nice boat, but on a week-long trip through the Boundary Waters in Minnesota it was a bit small for two large adults and their gear (total of about 550 pounds being carried). On the other hand, it was the lightest of the canoes we took, and anyone who paddled with me GREATLY appreciated that at the numerous portages. I originally built it for daytrips with a parent and teenage child, or two teens, and it is just great for that.

If you get David Hazen's book on strip build canoes and kayaks you'll see an alternate method for stripping the hull which calls for much less work in fitting the strips. Hazen includes fullsize plans for several canoes and 2 or 3 kayaks with the book, and has his own ideas on strongbacks, too !