What foam to use to build a fiberglass cooler?

[dannieboiz]

I want to build a custom livewell/cooler to fit in the cockpit of a 21ft parker. Picture of what i imagine the shape would be like. I see mix info one what foam works and doesn't and there's one video that say to paint the foam with 5 coats of latex paint before glassing.

Does anyone know the definite answer to which type of foam would work? Someone did it with Polyiso insulation foam and it seems to look great.

Would I want to use stranded fibeglass or weave matt fo such project?

 

[tpenfield]

Urethane foam if you are using polyester resin with your fiberglass

Urethane foam or Styrene foam if you are using epoxy resin with your fiberglass.

Polyester resin and Styrene foam just don't seem to get along, even if you have latex paint as a referee.

 

[dannieboiz]

Urethane foam if you are using polyester resin with your fiberglass

Urethane foam or Styrene foam if you are using epoxy resin with your fiberglass.

Polyester resin and Styrene foam just don't seem to get along, even if you have latex paint as a referee.

Which of the two combination is recommended for stregnth and cost effective would you recommend?

btw: this is the type of foam board that's available at my local supply store. would it work? 1" for the walls and 1.5' for the bottom and lid?

https://www.lowes.com/pd/Common-1-5-in-x-4-ft-x-8-ft-Actual-1-4375-in-x-3-875-ft-x-7-875-ft-R-Expanded-Polystyrene-Foam-Board-Insulation/3362408

 

[tpenfield]

It's a cooler . . . how strong does it need to be? Not sure you will notice a difference. If I were me, I'd go with urethane foam and poly resin.

Urethane foam sheets will be more expensive, but poly resin will be less expensive (than epoxy). Biaxial fiberglass cloth (like 1708) will be good for strength.

 

[dannieboiz]

it'll be holding about 35-40 gallons of water and I would like the lid to be strong enough to sit on. Will urethane work?

Here's anothe foam type available locally

R-Tech 1 1/2 in x 48 in. x 8 ft. R-5.78 EPS Rigid Foam Board Insulation 320817 - The Home Depot

Henry R-Tech is a cost-effective way to increase your project's energy efficiency. R-Tech is an engineered rigid insulation consisting of a superior closed-cell, lightweight and resilient expanded polystyrene

www.homedepot.com

 

[tpenfield]

Your cooler/live well is going to hold about 280 lbs. of water if full. You might want to plan a rib around the inside of the 'tub' at about half of the height for added strength.

The building supply store insulation may not be the best thing to use, because they often have a moisture barrier layer to them which will be an adhesion problem. You'll end up having to re-work the foam, which may be a mess.

Marine/aircraft type of urethane foam may be a bit more expensive, but will give you better results IMO.

In my travels, I found that the website aircraftspruce.com had pretty good pricing on urethane foam. I bought a bunch a couple of years ago for a fiberglass project.

 

[KJM]

I fooled around with polyiso foam this summer when i was debating using it for structures in my boat, like floor and bulkheads. Decided against it because of strength issues but for a cooler or live well it would probably work fine. The sheet i had had a thin cardboard backing on both sides and poly resin and fiberglass adhered just fine. When I bounced my weight on it after glassing a piece pn both sides, the glass didn't break but the piece buckled because the foam sheered apart lengthwise along the piece.

 

[dannieboiz]

Your cooler/live well is going to hold about 280 lbs. of water if full. You might want to plan a rib around the inside of the 'tub' at about half of the height for added strength.

The building supply store insulation may not be the best thing to use, because they often have a moisture barrier layer to them which will be an adhesion problem. You'll end up having to re-work the foam, which may be a mess.

Marine/aircraft type of urethane foam may be a bit more expensive, but will give you better results IMO.

In my travels, I found that the website aircraftspruce.com had pretty good pricing on urethane foam. I bought a bunch a couple of years ago for a fiberglass project.

Polyurethane Foam | Aircraft Spruce

Polyurethane Foam This foam is easily contoured using a large knife, and then sands well to final form. Excellent for producing the fuselage, wing tips, and other curved parts. It is fuel resistant and can be use...

www.aircraftspruce.com

those right? price seems reasonable. From the look of it, it is probably not rigid right?

Do you think a brace like this is sufficient?

 

[tpenfield]

Polyurethane Foam | Aircraft Spruce

Polyurethane Foam This foam is easily contoured using a large knife, and then sands well to final form. Excellent for producing the fuselage, wing tips, and other curved parts. It is fuel resistant and can be use...

www.aircraftspruce.com

those right? price seems reasonable. From the look of it, it is probably not rigid right?

Do you think a brace like this is sufficient?

Aircraftspruce also has a product called 'last-a-foam' which is resin compatible and is lower in price. (at least it was 2 years ago)

Not sure you want to use a cross member as it may be too obstructive vs. having ribs. The lip to support the cover if made large enough could also be a rib to prevent the top from distorting under load (full tub).

 

[dannieboiz]

Aircraftspruce also has a product called 'last-a-foam' which is resin compatible and is lower in price. (at least it was 2 years ago)

Not sure you want to use a cross member as it may be too obstructive vs. having ribs. The lip to support the cover if made large enough could also be a rib to prevent the top from distorting under load (full tub).

when you say rib, do you mean like padding the inside (or out) with a strip of another layer of foam? Basically a line across?

 

[Scott Danforth]

I built 2 55 quart coolers into the deck of my boat using 3/4" urethane foam, 1708 and CSM. I did use 1/4" plywood to line the bottom so when I dump beers and ice into them, it wouldn't crack

 

[dannieboiz]

I built 2 55 quart coolers into the deck of my boat using 3/4" urethane foam, 1708 and CSM. I did use 1/4" plywood to line the bottom so when I dump beers and ice into them, it wouldn't crack

Love the idea on the plywood. How much did you cost you in materials? I'm doing some rough calculation and the price? Trying to figure out how much it would cost for this build. I did some rough estimate and it seems to be upward 400-500 withj most of the cost in the resins.

 

[tpenfield]

BTW - are you using Sketchup software for your design?

 

[Scott Danforth]

Love the idea on the plywood. How much did you cost you in materials? I'm doing some rough calculation and the price? Trying to figure out how much it would cost for this build. I did some rough estimate and it seems to be upward 400-500 withj most of the cost in the resins.

if you worry about cost on a project, get a different hobby.

it was part of the transom/bulkhead/stringer repair. that whole project was about $2500 back in 2011

buy your resins from a dedicated fiberglass supply shop

case in point. 1 gallon of boat yard resin is $20. .87 gallon of bondo brand crap resin from the local box store is $50. why pay 2.5 times as much for product that is only 1/4 as good?

much cheaper to buy the good stuff from the right source.

 

[dannieboiz]

@tpenfield - yes Sketchup is the only thing I know how to use.

@Scott Danforth - Where are you finding resin for $20 I'm seeing 50-100 dollars online.

​

 

[Scott Danforth]

@tpenfield - yes Sketchup is the only thing I know how to use.

@Scott Danforth - Where are you finding resin for $20 I'm seeing 50-100 dollars online.

​

I walk into fiberglass coatings and use my discount

Polyester: gallon: Resins, Polyester & Vinylester & Epoxy - Page 1 of 2

Resins, Polyester & Vinylester & Epoxy

www.fgci.com

 

[dannieboiz]

I walk into fiberglass coatings and use my discount

Polyester: gallon: Resins, Polyester & Vinylester & Epoxy - Page 1 of 2

Resins, Polyester & Vinylester & Epoxy

www.fgci.com

Down side of me being in CA, not many fiberglass shops around and everything is stupid expensive.

 

[tpenfield]

My 'local' guy (90 minutes away) is up to $78/gallon for VE. Lists Poly at $38, and EEEEPoxy at $100 . . .

2-3 years ago, I was getting VE for $50-60/gallon from him. Ordering online also adds shipping and sometimes 'hazmat' costs.

 

[dannieboiz]

Do you guys know how to best calculate how many gallons of resins I would need for this project?

 

[tpenfield]

Do you guys know how to best calculate how many gallons of resins I would need for this project?

More like guesstimate . . . but I generally go by how much cloth is going to be used and the thickness of it to get an approximate volume figure. Then factor resin at about 50% of that volume. Then convert cu. in. (cu. ft) to gallons.