Incorporating Kevlar into a plywood hull?

[MarkNY]

hi, id like to use kevlar in the construction of a stitch and glue plywood boat. what is the process for working with kevlar and what is the best way to determine which weight kevlar is best for my application? just trying to understand the use of kevlar in wooden boat construction. thanks alot, mark

[Phil Locker]

Kevlar's good in tension, not so good in compression. On plywood boats (Fireball sailing dinghies) I've seen it used on the inside surfaces of the ply to deal with oil canning and other localized distortions. Because its tensile strength is so great its also useful at shroud and forestay attachment points, for instance. Think long and hard before using it to sheath the outside of the hull. Yes, its great for impact resistance, but if you ever have to repair it (or sand into it) it fuzzes and you'll have a very difficult time getting a smooth repair.

In terms of working with kevlar, its very difficult to cut. Buy a very sharp pair of shears and set them aside ONLY for cutting kevlar - don't dull them by cutting fiberglass. Due to its low specific gravity it would far rather float on top of your epoxy than bond to the wood - vacuum bagging is very useful here.

Weight.... 4oz is probably plenty for sheathing, but 6oz is easier to find.

Phil

[B. Hamm]

Also worth mentioning that Kevlar is difficult to tell when it's wet, it's not like glass that turns transparent when it's wet, Kevlar looks the same wet as dry.

Bill H.