Laminating inner and outer stems - Trap for young players?

[Plane sailing]

Well I actually started my Canoe, had all the strips for the bow and stern stems ready, test bent, clamping sequence etc. Due to a limitation of the number of clamps could only do one end at a time. Probably a good thing....
in the picture it shows the stems on the form, with enough clamps to hold it in place, two people made the job much easier, no breakages in the strips during bending and no steaming needed. looked like I was on a winner....

Glued the first pair up using Titebond 3 (this was probably my downfall?) Temperature was well above the chalking point, left clamped for 48hrs. On removal from the form, both stems sprang away from the form by as much as 3/4" at one end.
Question is this, would epoxy have prevented this happening? - the force to initially hold the laminates in place dry was not huge, I could grab the clamp hole and squeeze them in with hand force only. I even left the strips clamped in place dry for several days prior to removing and then glue up.

I'm not taking chances with the next lot and will use epoxy (after making another set of strips of course).
Its just a bit frustrating as you would imagine.

Roy.

[PAR]

This is called "springback" and it's normal, regardless of the adhesive. Epoxy might have only sprung back a 1/2", instead of the 3/4" (speculation) you experienced, but there still would have been some. The only way to avoid a lot of spring back is to use thin laminations, with a high layer count and each layer with alternating grain. What most folks to is expect some (about 10% more radius) and over radius the pieces on the mold. Simply put, find the tightest radius, along the stem or rib and subtract 10% from this, when you make the mold. It's a bit of guesswork, until you get a feel for how much spring back something might give you. For example, you now know you're getting about 3/4", so the next one you bend, wedge both ends in about 3/8", so when it springs back, it's about what you want.

Spring back is different with every lamination. If you made three ribs from the same mold, each with the same number of layers, each the same thickness and wood species, you'll still have some variance between the three in regard to amount of springback. Yeah, it sucks, but it is fairly predictable one you get a few under your belt. BTW, there's no boat ever built that was precisely dimensioned, as shown on the plans. Get it close and try to keep it symmetrical and you'll be just fine.

[Plane sailing]

I laughed when I read your reply and said "of course!"
Everything makes so much sense, I needed that reminder to step back and think of course it's not going to be 100% precise. Given I know what the spring back is for this type of timber, I'll just glue up the other stems and pack the forms for the duration of the stripping process. In the scope of the final product its not going to make a scrap of difference.

Many thanks!