which resin to use?

I built a center console out of plywood for my boat and i want to glass it i plan on doing one layer inside then one layer outside which should i use polyester or epoxy or do you have another suggestion? other than painting it and calling it a day! I want the fiberglass to give it a little more strength

 

Adding a thin sheathing both inside and out will impart very little additional strength. What it will do is waterproof the surfaces and add considerable abrasion resistance compared to simply painted plywood.

Regular 'glass structures are surprisingly weak for their weight, which is why, hull shells are so thick and stiffening elements are placed everywhere within the structure.

Polyester doesn't stick very well to wood, certainly not nearly as well as epoxy, making epoxy the preferred choice for one off construction.

 

well i may put a couple layers on the inside to give it a little strength but only one on the outside

 

Seems to me like you have it backwards; the additional layers belong on the outside.

Jimbo

 

why does it matter if the layers are outside or inside? I am new to this so any helpful info will help

 

Having the thicker skins on the outside will make the structure far more durable in service. After all, who's going to kick or walk on the inside of your center console?

Jimbo

 

Additional layers of material on the inside will increase its puncture resistance, while a single skin on the outside will increase its abrasion resistance, particularly if this is (outside) polyester fabric or one of the modified acrylics. It simple physics really.

 

if you think your plywood boat is strong enough with no fiberglass at all may help you figure out how much or where to put your glass,one good feature of fiberglass is you can repair easily so you could always put more later if you felt you needed to

 

Put it on the outside - 3 coats of epoxy using say 6 oz cloth or lighter. Apply the second coat when the first becomes just tacky. When cured (say 24 hours) sand off smooth then apply the final coat. Sand smooth again, fill faults and voids with thickened epoxy, then sand smooth. Then paint with a quality paint to protect against UV. Fibreglassing inside something as fiddly as a console may just create moisture traps depending on the construction. If there are sharp angles on the inside, the fibreglass will pull away from the timber while curing. A good primer and paint job on the inside will be fine in most cases.

 

i agree with rwatson, it would be very hard for any one to put a layer of glass on the inside of a boat,and will probably just lead to rot. another thing you could do when glassing the out side is to put additional layers at places like the bottom of the keel,around the edge of the stern,anywhere that may have extra weight on them do to trailering or beaching,or laying against a marina. if you do it though it will make a better looking job if you taper the strips of cloth ex makeing the first layer as much as 8" wide,next 6",4",3", for running down the bottom of the keel.
one more thing to consider is the type of plywood you used,i know polyester dosn't "stick" to spruce plywood well, fir plywood is what most boat shops use around here,but i don't know much about epoxy.

 

Folks read the original post. He's built a center console for his boat, not a center console boat. He wants to reinforce the console a little and of course water proof it. He's not 'glassing around ribs or other structural elements, he's 'glassing the inside and outside of a box.

The highest strength and penetration resistance will be with the heaviest sheathing on the inside. This isn't guess work, it's fact. To insure the console remains solid, it needs to be encapsulated, so an exterior coating and sheathing is also recommended.

Coating and sheathing just the outside will permit the console to soak up condensation and other collected moisture on the inside and the box will sheer its exterior sheathing from moisture gain.

Softening the inside corners is easy, with fillets, wood strips or foam. 'Glassing the inside of a box isn't hard and will keep the box from turning into mush from the inside out. There's no short cuts folks, just lousy ways to do things and better ways. Sheathing one side of wood is a lousy way, pretty much guaranteed to cause issues down the road.

 

Thats right - its only a console, so the chances of it turning to mush with coating on just the outside are probably very small with a decent paint coat on the inside.
Jeremy will have to make a decision as to whether the inside is easy to fibreglass. Its true, you can slap thickened epoxy on areas that have sharp angles, sand off the rough bits, cut out sections of cloth, epoxy them all in. Its only your time and labour.
But like Jeff said, if the plywood is strong enough, it doesnt need the extra strength, and a good coat of paint on the inside will be plenty of 'encapsulation' to prevent rot in a console. Its not like bilges or low areas that will have water laying against it.
Its true there are no short cuts - but there are plenty of ways to make a satisfactory job longer.

 

yea maybe i should pay more attention to the question,i guess i got a little exited thinking there may be something here i could add to,o well good luck jer and i'l be here to answer all your questions you didn't ask