Oh Boy...This Smell Ain't Good

[TownsendsFJR1300]

EDIT: I tried to just respond with just the smilie face thingy, but the forum said I had to use at least 10 characters. So I edited by adding these two statements... which is now much longer than 10 characters...

Just type in a bunch of periods. That works as well..

Back to the thread.

[Jason2tpa]

I dropped the tank i'm replacing back into the fuel coffin to gauge the amount of space. I'm still undecided as to how i'll anchor the tank on the sides...foam, glassed blocks/precision board as a wedge, glass in 4 mounting blocks above level of tank secured to welded tank tabs using screws. As you can see from the pictures, space is limited. 2" at top and bottom, 1/2" on sides.

[panasonic]

For those of you interested in the properties of precision board in marine applications.

HDU Marine Board - Coastal Enterprises - Precision Board Plus HDU

According to the manufacturer it does not absorb or hold water. Most solvents wont damage it and it can glased over with epoxy or polyester resin. Check out the spec sheet.

For Jason's fuel tank, blocks of it bonded on to the tank sides with 5200 for spacers to keep the tank from shifting around would work good. Aluminum tabs around the top perimeter secured to the boats framework to keep the tank down tight to the bottom.

Jason if you decide to try and use it get the highest density possible.It comes in
probably 10 different densities,the higher the number the denser it is.

[TownsendsFJR1300]

Does the tank sit on anything in particular?

Or just sitting on the fiberglass "floor"?

Rubber pads?

Also, that 2" space is plenty. As you saw on my pic's, that angle aluminum mounts are about 1" tall and my space might be 3"..

[Jason2tpa]

Does the tank sit on anything in particular?

Or just sitting on the fiberglass "floor"?

Rubber pads?

Also, that 2" space is plenty. As you saw on my pic's, that angle aluminum mounts are about 1" tall and my space might be 3"..

Tank was resting on a rubber mat...which is worse than if the tank was resting directly on the coffin floor bc rubber absorbs water.

I'll elevate the new tank off the coffin bed by bonding 3 pvc/frp strips to the bottom of tank, each running the length of tank. Strips are 2" wide and 1/4" thick. A 1/4" elevates tank enough to allow air flow around tank.

[scofflaw]

I think no matter how much you try to make the coffin water tight, water will still get in there. Old boat , old deck, condensation, deck plates, I'd say it is inevitable. One reason I went with poly tank and glad I did.

Do you have a drain in the coffin ? Personally I would coal tar the tank and get it higher than a 1/4". Poly tank is a much simpler install as well.

[SJCJACKST]

So, not the new tank the Previous Owner said??

[Jason2tpa]

Update:

My fabricator started work on the new tank yesterday. Should be finished early next week. Here's what I'm still battling...how to secure the tank. Below is a cross-section sketch of the fuel coffin liner and the adjacent stringers.

I had my mind made up to weld tabs on tank and fixate these to a pvc mounting block, the block either glassed in or bonded. I planned on overdrilling the stringer, fill with epoxy, then drill the tab screws into the hardened epoxy. But the problem I forsee is the liner does not rest against the stringers. The stringers and the liner have completely different angles from their base, as you can see from my sketch. The only contact point the stringer and liner make runs the length of the liner, bottom corner.

Unless I were to cut out large sections of the liner to allow me access to stringers, which I'm not going to do, there is no way for me to have access to the stringers to fill the overdrilled holes with epoxy.

I took a 3/32 drill bit and drilled through the liner, in a location where tabs would line up. Once I drilled through the thin liner I used the drill bit to measure the amount of space between liner and stringer. About an 1" to 1-1/4".






Another option would be to use Moeller's hold down strap, pictured below. I like this method. Actually, it coincides with how Aquasport originally secured tanks, 2 aluminum straps. But if I were to use these straps I'm left with the same problem as described above...no solid structure for the anchor screws to bury in.





I'm open to using foam now that I've read more about methods to keep the foam from creating air pockets. But filling the space between liner and tank with foam will only prevent the tank from moving laterally. I would still be left with figuring out how prevent the tank from elevating. I also don't have the option to glass in a 2x4, the width of tank coffin, because there is only 1/2" between the top of the fuel inlet hose and underside of fuel tank access panel.

Thoughts, suggestions welcomed.

[Jason2tpa]

Update:

My fabricator started work on the new tank yesterday. Should be finished early next week. Here's what I'm still battling...how to secure the tank. Below is a cross-section sketch of the fuel coffin liner and the adjacent stringers.

I had my mind made up to weld tabs on tank and fixate these to a pvc mounting block, the block either glassed in or bonded. I planned on overdrilling the stringer, fill with epoxy, then drill the tab screws into the hardened epoxy. But the problem I forsee is the liner does not rest against the stringers. The stringers and the liner have completely different angles from their base, as you can see from my sketch. The only contact point the stringer and liner make runs the length of the liner, bottom corner.

Unless I were to cut out large sections of the liner to allow me access to stringers, which I'm not going to do, there is no way for me to have access to the stringers to fill the overdrilled holes with epoxy.

I took a 3/32 drill bit and drilled through the liner, in a location where tabs would line up. Once I drilled through the thin liner I used the drill bit to measure the amount of space between liner and stringer. About an 1" to 1-1/4".






Another option would be to use Moeller's hold down strap, pictured below. I like this method. Actually, it coincides with how Aquasport originally secured tanks, 2 aluminum straps. But if I were to use these straps I'm left with the same problem as described above...no solid structure for the anchor screws to bury in.





I'm open to using foam now that I've read more about methods to keep the foam from creating air pockets. But filling the space between liner and tank with foam will only prevent the tank from moving laterally. I would still be left with figuring out how prevent the tank from elevating. I also don't have the option to glass in a 2x4, the width of tank coffin, because there is only 1/2" between the top of the fuel inlet hose and underside of fuel tank access panel.

Thoughts, suggestions welcomed.

[Jason2tpa]

So, not the new tank the Previous Owner said??

No, but now that I've thought about it since having access to tank I think he was speaking of hoses. He probably said he replaced the fuel inlet, pickup, and vent hoses. Because these hoses are in very good shape, compared to the tank.

[Jason2tpa]

I think no matter how much you try to make the coffin water tight, water will still get in there. Old boat , old deck, condensation, deck plates, I'd say it is inevitable. One reason I went with poly tank and glad I did.

Do you have a drain in the coffin ? Personally I would coal tar the tank and get it higher than a 1/4". Poly tank is a much simpler install as well.

There is no issue with an aluminum tank getting wet, because as you noted, water will still get in. In order to prevent moisture from laying against the tank there must be allowable air flow around the entire tank.

Yes there are 3 drain holes in the coffin aft.

Re: "Poly tank is a much simpler install as well"....

Not in my case. Securing the tank, poly or aluminum, would pose the same issues I'm battling.

[Jason2tpa]

I think no matter how much you try to make the coffin water tight, water will still get in there. Old boat , old deck, condensation, deck plates, I'd say it is inevitable. One reason I went with poly tank and glad I did.

Do you have a drain in the coffin ? Personally I would coal tar the tank and get it higher than a 1/4". Poly tank is a much simpler install as well.

There is no issue with an aluminum tank getting wet, because as you noted, water will still get in. In order to prevent moisture from laying against the tank there must be allowable air flow around the entire tank.

Yes there are 3 drain holes in the coffin aft.

Re: "Poly tank is a much simpler install as well"....

Not in my case. Securing the tank, poly or aluminum, would pose the same issues I'm battling.

[panasonic]

what is the fuel coffin made of and how is it attached to the boats main structure?

[Jason2tpa]

what is the fuel coffin made of and how is it attached to the boats main structure?

Thin poly, few millimeters thick. There is a flange around the liner. Originally it drops into the compartment and a few strips of glass laid over its edges, bonding it to stringer. Then deck laid overtop.

[TownsendsFJR1300]

I'm probably mis-reading but I still don't see why you can't epoxy 4 blocks (filler blocks) that fit in-between the stringers and tank tabs. Then screw to the blocks.

Set the tank where you want it, trim blocks to fit each corner and epoxy overnight.. You, right now, have plenty of room right now to clamp the "blocks" to the stringers...

I'd (if the epoxy would take to to it) use that plastic composite (used around the boat in either black or white colors).

Also, you may consider a smaller amount of foam (I know they make different types) at the four sides towards the ends. It'll easily last 10 years and work fine. *You had ONLY foam before and the tank didn't go anywhere. Shouldn't be an issue using the correct foam...

Re the straps, if Aquasport used them originally, were the straps attached to the deck (under the tank). Why not simply attach there?

Does the fabricator have any specific ideas that he recommends?