AA Blackjack Floor Repairs

[Dennis P.]

I would not use coosa board for stringers. I don't believe it's modulus of rupture comes anywhere close to that of wood. I believe wood sealed and glassed properly will be just fine in this situation.

yes, i agree to a point. you can't just compare the physical properties number for number.

the overall strength and stiffness of the wood stringer is its cross section alone.

with a composite member, you have to take into account the relative stiffnesses of the materials. so for example, a stringer made up of a foam core and wrapped in fiberglass cloth and epoxy resin, 99.5% of the strength and stiffness is the FRP shell. The foam just goes along for the ride.
With a wood or coosa type material, it is more like 80/20 or 90/10 type ratio.

concrete and steel reinforcing has a modulus ration of about 10.

The only benefit I see to coosa is the inheret no-rot and dimesional stability of the material.

I am also toying with making my own stringers by using blue/pink foam as a core and laminating it myself, vaccum bagging my making a 'bag' out of polyethelene sheeting.

as always, work gets in the way of play

 

[Eric Patterson]

Dennis

I would pursue making my own just out of fun for the discovery process. I think there are many ways to go and end up with a satisfactory result. I just wouldn't discount wood in favor of Coosa for some perceived superiority because I don't know that one exists and wood is so widely available, cheap, and proven if properly encased in glass and epoxy.