Need advice on installing a fuel tank.

This is how the hull looks now. The Divinicell will fill back in where the wood was and then I will sand, clean and reclass the entire area. Up the stringers and up both bulkheads.
 
This picture was taken some time ago. I had heat lamps, blowers and a vacuum pump hooked up that ran continuously for about 2 months. You can see my moisture meter in some of the photos.
 
Divinicell is a great material. Make sure you use epoxy and not polyester resin as epoxy have superior chemical bonding.
 
PascalG said:
Divinicell is a great material. Make sure you use epoxy and not polyester resin as epoxy have superior chemical bonding.
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Well, that was what I thought as well. I spoke with Pat from Fiberglass Supply and he confirmed that my hull is made from polyester resin. He explained that if my hull was epoxy, I would need to use epoxy but he said that it was not necessary to use epoxy. He explained that I need to thicken my first resin with fumed silica when I install the Divinicell. The hull inside where the wood was is rather rough. He told me to trowel it on like I would thinset with tile. This will fill in any low areas and get me close to 100% contact with the hull.
He said to wet the underside of the foam with resin with no fumes silica before installing it on the troweled resin. Then put sand bags, weights, or some sort of method to press the foam down.
He said once that has set, come back and fill in all gaps between the existing wood/fiberglass and the new foam with more thickened resin. He said i can use microbaloons or fumed silica here. He said he would use the microbaloons because it is much easier to sand smooth before I overlay the foam with layers of glass.
Everyone concur that this is a good plan?
 
You are on the right track. My poly tank in my Sea Ray is insulated from the fiberglass with thick polyester sheet with aluminum hold downs with again polyester sheet insulation. Do not forget to properly ground the installation.
 
Yeah polyester on polyester is fine but you still get a better chemical bond with epoxy especially with Divinicell. I d use west system with some of their 404 high strength filler to bond the core to the existing outer layer. Then use non thicken epoxy to laminate new glass cloth on top, obviously extending at least 12” beyond the end of the core

I ve used both poly and epoxy and west system epoxy is much easier to use in addition to yielding better bonding. I built a 26’ sailboat using West and Divinicell…
 
PascalG said:
Yeah polyester on polyester is fine but you still get a better chemical bond with epoxy especially with Divinicell. I d use west system with some of their 404 high strength filler to bond the core to the existing outer layer. Then use non thicken epoxy to laminate new glass cloth on top, obviously extending at least 12” beyond the end of the core

I ve used both poly and epoxy and west system epoxy is much easier to use in addition to yielding better bonding. I built a 26’ sailboat using West and Divinicell…
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Excellent. I will look into getting some epoxy for doing what you suggested. What about adding the additional framing (for lack of a better term) around the tank? Is that a good idea? Is that how it should have been done from the factory?
 
PascalG said:
Yeah polyester on polyester is fine but you still get a better chemical bond with epoxy especially with Divinicell. I d use west system with some of their 404 high strength filler to bond the core to the existing outer layer. Then use non thicken epoxy to laminate new glass cloth on top, obviously extending at least 12” beyond the end of the core

I ve used both poly and epoxy and west system epoxy is much easier to use in addition to yielding better bonding. I built a 26’ sailboat using West and Divinicell…
Click to expand...
The 404, is that an additive filler you mix with the epoxy? Is this stuff similar to fumed silica?
 
Yea you want the tank to be held in place, how was it secured before?

You don’t have to to fully frame the tank. You could just epoxy blocks, about 1 to 2” tall to secure it.

Another good thing about west system epoxy which btw doesn’t smell, is that it’s much easier to measure with the pumps.
 
clshortt said:
The 404, is that an additive filler you mix with the epoxy? Is this stuff similar to fumed silica?
Click to expand...

Yes, west system has a number of fillers. 404 is the high strength filler for bonding. There are also fillers for filleting, gluing as well as fairing.
 
I’ve used West System for a few small projects and it is easy to use as noted above and doesn’t have a strong odor.
However still be careful wear personal protection equipment because you can develop an allergic reaction to epoxy with repeated exposure. Not sure if the same is true with polyester.
 
Here are some images of why I’m finding in the area under the tank. Huge air pockets in the original laminate layup, exposed chop strand everywhere. The wood core was attached at what I would guess is about 50% of the hull. The layup is wavy, like a tin roof. The only places where it was attached were the high spots.
This is crazy! This thing must have been laid up on a Friday before a long weekend!
IMG_7910.jpegIMG_7911.jpegIMG_7912.jpeg
 
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