The foamed fin can would dissipate energy in a fluttering fin somewhat by transmitting some of the energy through the fin into the energy absorbing polyurethane (also popular for sound damping)
However that is a relatively inefficient way of dissipating the fin energy. If you have a fin geometry that is prone to flutter a more effective and easier way to add some damping is to laminate a layer or 2 of Kevlar cloth to the fins.
Yeah, I heard about the "rule of thirds" which in reality is a labor intensive thing to do. It goes like this: Layup a piece of fiberglass or whatever cloth 1/3 up the finspan. Next, lay a piece 2/3rds up the span and lastly a final layer tip to tip. For a four finned rocket that would be 12 pieces to cut! I have an ongoing 4" LOC tubed project I glassed the tubes and then did the above on the 4 fins over the 1/4" plywood fins. Laid a final layer of .6oz cloth to close up the weave to make it look nicer.
The internal and external fillets (applied before laying the cloth of course) were Duralco 4525B. It was a real PITA to do and would likely be way overkill on a glass rocket unless the glass rocket was really being pushed to hyper-speeds
or the fins were surface mount. Mine are TTW by necessity of being glass and plywood. It's appropriate for a 4" cardboard plywood rocket that's going to fly on at least a 54mm L1400.
I made a 38mm MD rocket with 4mm thick 5 ply plywood fins on a LOC cardboard tube. Four fins, 12 pieces of 2oz glass on the fincan as described above. Stupidhead here flew off a dirty rail with a Mayhem Rocketry rail guide. My fault entirely as it bound on the rail and the rocket blew threw the (early version) rail guide like it was nothing. Ran arrow straight, to 8600', 950mph as "told to" by the EggFinder TRS. Both halves of the guide were destroyed and I was totally shocked there were only a few chips out of the paint on the leading edges of two of the fins with no wood damage. Whoa, that build technique is strong. Would probably gone higher if stupidhead used a clean rail!
I'm actually glad I did that stupid mistake as it showed me first hand the integrity of that build technique. Yeah, don't get me wrong. I think that's a way overkill technique with a fiberglass/CF rocket and G10.
I foamed a fincan on a Wildman Punisher Sport (the small one for 29mm motors) with full strength PML stuff for fun. I forgot I just sealed the slots in the centering ring for the Wildman type internal bridle with masking tape and a little foam leaked through. Inside the parachute bay is o.k. but the fincan does seem more solid. I don't care about the weight as I'm running an EggFinder in the nosecone. An H250 is easy if it doesn't CATO on me again like it did in another rocket but if I can
extend a delay by adding a little bit to the long delay to get close to 15-16 seconds, an I200 is possible. Using a Jolly Logic Chute release for pseudo dual deploy. Kurt