Deck - Diviny Lam Sched?

[ElBichoMalo]

With 3/8" divinycell core material, how much glass is enough? I glassed the bottom of the dininycell with 1 layer 1708, and planned to "glue" that down the what's left of the old glass (there will be some gaps with no old glass). I wanted to glass the topside after the core is all down, filled, etc. Was thinking two layers 1808 and maybe some 1-1/2 or something.

I know the sandwhich construction gets its strength from both sides of glass, so I know it won't be solid with one side glassed, but it is flimsy. I don't want to find out later that I needed more glass on bottom.

All the old posts I found in search were plywood. Anyone with experience or thoughts on this?

Thanks,
Evan

[FishStretcher]

The potter decks were 1/2 balsa with an asymmetric layup. More material topside for penetration resistance. Not a lot below. I have a pic and notes on this. Let me see if I can find it. Probably my "Bass relief" thread.

Here it is: post #63 in the Cape Cod Crusader thread: http://www.classicseacraft.com/commu...ad.php?t=25061

You can guess how many layers that is. I haven't dissected it. But you have thicknesses, so that can get you there.

[FishStretcher]

(This was me thinking about a 3/8" versus 1/2" core...)

Bending stiffness varies with the (I always mess this up) square of the thickness, everything else being equal.

So a 0.9" deck (0.5" core, 0.3" top, 0.1" bottom) is about a third stiffer (but no more damage tolerant than) a 0.78" deck with a 0.38" core. With a 16" increase in thickness overall, or a third thicker core.

So a little more laminate than this wouldn't be bad. Like 0.375" core, 0.32"top, maybe 0.12" bottom for about the same stiffness.

The glass is what gives it strength and stiffness, so if you can get a better glass-resin ratio, you don't have to go as thick for the same stiffness. I hear this can be done by putting peel ply over the top and squeegeeing excess resin thru. This saves the hassle of vacuum bagging. And sanding.

[martin]

I did the exact same on my 76 23 restore check it out.. I cut the old core out nd kept the bottom skin.. It was very flimsy.. And well old so i ground the glass Down with36 grit and layed a fresh layer 1.5 oz mat let set up.. Then went back and fit all the core material in place... Pulled it back out and wet out one layer of 1708 csm up then reinstalled the core material.. Then vac bagged it down.. Let it cure.. Then went back and leveled the foam down... My foam was 13mm or 1/2" so i had to sand it down some.... To level with existing deck glass.. Fethered edges and layed 1 layer of csm 1.5 oz.and 2 layers of 1708 csm up.. This deck is harder then a Brick Bat..and since i am going with a 1/2 ,teak sole..i think this would be fine.. Check out my thread... Martin

Originally Posted by ElBichoMalo

With 3/8" divinycell core material, how much glass is enough? I glassed the bottom of the dininycell with 1 layer 1708, and planned to "glue" that down the what's left of the old glass (there will be some gaps with no old glass). I wanted to glass the topside after the core is all down, filled, etc. Was thinking two layers 1808 and maybe some 1-1/2 or something.

I know the sandwhich construction gets its strength from both sides of glass, so I know it won't be solid with one side glassed, but it is flimsy. I don't want to find out later that I needed more glass on bottom.

All the old posts I found in search were plywood. Anyone with experience or thoughts on this?

Thanks,
Evan