Fiberglass laminate thickness

[Tornadosailing]

I'm looking to build a bench seat/storage box for the cockpit on my cat. Fountaine Pajot intended to have two chairs taken from inside the boat to the cockpit. In later models they incorporated a bench seat with storage in this spot, and I'd like to replicate that.

My plan is to build it with 3/8 divinycell cored fiberglass, but I'm unsure how thick the fiberglass layup needs to be. My first thought was 1/8 inch layup on each side of the foam core, but I don't have any idea if this is overkill or not enough.

Thanks!

[SailRedemption]

I would say, since you're using a core, that a mat, two biaxles, and a final mat would be plenty. That layup is for both sides. Overlap your corners some as well. I'm assuming you will already epoxy "mud"/bond the core together and filet before glassing.

[thinwater]

Originally Posted by SailRedemption

I would say, since you're using a core, that a mat, two biaxles, and a final mat would be plenty. That layup is for both sides. Overlap your corners some as well. I'm assuming you will already epoxy "mud"/bond the core together and filet before glassing.

Yeah, pretty much. My last boat (PDQ) was built with 2 layers of 1708 (17-ounce biax with a thin mat attached) over foam, in a mold. Without the mold, I'd put a layer of finish cloth (thin cloth) on the surface.


But you'll need to figure out the spans and bracing. Also, unidirectional is what you want to carry big cantilevered loads (you can sandwich it in).