Kevlar degradation question

Hello all, I recently bought this little boat and, now that I've got new handholds and center thwart in it, I put it on the water in our little pond to see how it handles. The entire gunwale system shakes and twists fairly dramatically when I'm seated on one of the two seats. If I twist my hips or shake my butt, I can see both gunwales twist out of true and wobble along the full length of the hull - clearly the kevlar that makes up the freeboard is thinner or more brittle than I am comfortable with.
I'm not familiar with kevlar boats and don't know if that's normal, but I suspect it's not. As is, I wouldn't feel good taking this boat pond-hopping any distance where I may have a serious failure far from the truck.
Would new woodgunwales tighten the boat up, or am I looking at an issue with UV-degraded kevlar that would make this an our-pond-only boat? If it's a total bust, I'm not out so much money that I would feel the need to invest time and labor to salvage it.

I'm not familiar with that hull but kevlar is not known for being the most rigid material and it's not uncommon for a kevlar hull to flex and twist. Not being there in person it's hard to say what might be normal/abnormal or just how much flex and movement there is but it might just be the nature of the beast due to the design and construction of the hull. I don't think it's something that would overly concern me.

Alan

One thing you could try is adding a couple of thwarts. Lots of tandems would have 2 more than your boat, one just behind the front seat and one about halfway between the yoke and rear seat. Adding thwarts will reduce twisting but it's hard to guess how much it will help without knowing where the flexibility is in your boat. Do your current gunwales have metal under the plastic?

New kevlar hulls are bright yellow. Broad sides, such on C4 canoes tend to flex slightly in and out, even when new. From my usual race bow seat I can see it flex by my legs when crossing through waves. Being poorly stored in the sun turns kevlar increasingly brown. I have seen many old dark brown kevlar canoes that race year after year without apparent issue. Kevlar fabric itself is not the problem, it is the resin that holds fabric sheets together that is susceptible and breaks down due to UV.

A woodstrip boatbuilder I know installs thwarts and seats attached with a stress from one side to the other. When I removed the six seats and thwarts from my 34' voyageur canoe for refinishing, after I reinstalled them it flopped and twisted like a wet noodle. Pat told me to put some tension in when I reinstalled the seats and thwarts. After I removed and reinstalled them with a very slight offset from perfectly square across the gunwales, it was as good as new.

gumpus said:

One thing you could try is adding a couple of thwarts.

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That was my first thought too but when I looked at the pictures I thought it looked like the seats were bolted directly to the gunwales, essentially making them thwarts.

Edit to say: Nevermind, I don't know how I missed the obvious seat dowel in one of those pictures.

Alan

Thanks to all, I will continue to mess with it and see how she handles in increasingly adverse conditions. I have a fondness for little canoes like that.
Yes, there are dowels running from seats to gunwales, so replacing those with a solid wooden bracket would effectively make thwarts out of the seats. That might do wonders for the stiffness.