¼” plywood strong enough??

Would 1/4” plywood be a strong enough core covered by 6oz fiberglass and epoxy inside and out to build a 4.5’ wide by 2.5’ high and 5 foot long half cab “shell”?

 

Describe what you mean by strength. This is a generic term that doesn't describe anything. Strength needs relevance a frame of reference or a specification(s).

 

Strength enough to handle a wave or two over the bow as a protective shell to store things basically. Mounting points will be backed with 1/2" ply, the steering console and inner frame will be made of 1/2" ply and the stern edge of the cab will be reinforced with 1/2" ply.

 

Again you haven't provided any information. If you want specifics, you need to be specific with your questions. I know you know what you want, but we haven't a clue what you're talking about.

What kind of strength, tensile, compressive, elongation? What size wave, 10', 20', 100'? What speed will you encounter these waves? What size boat? It's weight and general dimensions and equipment? Your asking for a specification where no parameters exist. This is like asking a doctor for a prescription, without telling him what's wrong with you.

 

Okay, tensile strength of the structure when the 1600 lb, 16' X 6'6" boat (half cab in question, built in 6'X2' fish box and 60 hp 4 stroke) travelling between 4-7 knots "scoops" a 3-4 foot wave.

 

1/4" five veneer plywood, rated exterior or marine grade will do, if encapsulated in epoxy, then sheathed with a light weight fabric (2 - 10 ounce cloth). Most exterior grades (construction grade) will be 3 plys and this is very weak in comparison to 5 ply marine grade. If you use this type of plywood, then increase the sheathing thickness to at least 16 - 20 ounces (2 layers of 8 ounce or two layers of 10 ounce cloth). The heavier sheathing will add some rigidity, though not as much (per pound) as the better grade of plywood (5 veneer). 1/2" mounting pads is a good idea too. Consider through bolts in the mount, with more backing pads, or really big *** fender washers.