Oh Boy...This Smell Ain't Good

[TownsendsFJR1300]

Looks great! Filler tab dead nuts on!

How" tight" are the glued in blocks? Pretty sturdy?
(Don't think it's going anywhere)

Did you get the fuel gauge figured out?


BTW, Looks like he did a VERY NICE job on the tank...
Just curious, (if you don't mind), roughly how much for the tank?



.

[Jason2tpa]

Update and Finale:

Time to put this thread to bed. New tank is installed. For those interested here are the tank prepping details:

*5200 fast cure bonded 1/4" thick x 1-1/2" width pvc board strips the length of tank, 3 strips, 2 on outer edge and 1 down middle. Heavy coat of 5200.

(prior to bonding I etched tank with 80 grit where strips would bond. Also sand blasted the bonding side of pvc strips. Cleaned both tank and strips with acetone soaked rag)

*Let cure 24hrs

*Sand blasted strips, acetone clean. Ran a 1/8" bead of 5200 fast cure down the middle of each of the 3 strips. Carefully lowered tank down into coffin. Filled the fuel tank with the 15 gallons I had siphoned out of the old tank (which was brand new fuel). The fuel in tank provides an even downward weight distribution.

*As the above cured I worked on the securing tabs. I cut (4) pieces of 3/4" thick x 3.5" width x 4" length pvc board, (2) pieces of 3/4" thick x 3.5" width x 8" length.

*Opting not to have fabricator weld tabs, the pvc board was 5200 bonded to top of tank and bonded to coffin liner. Areas of bonding to tank and pvc board was etched prior to bonding, same as previously mentioned.

All in all the install went very well, no hiccups to mention. The tank is elevated off the coffin by 1/4" strips of pvc and centered in coffin with 2" space between coffin and tank. No foam, no glassed in locking tabs, or anything on top of tank.

Essentially the tank is hovering inside the coffin, using pvc board to keep it off the bottom and away from the coffin on 5 sides . If/when water gets in the coffin it drains out via 3 thru holes located most aft that drain into bilge. Barring some unforeseen accident, this is the one and only tank I'll need to install in this boat.

[Jason2tpa]

Update and Finale:

Time to put this thread to bed. New tank is installed. For those interested here are the tank prepping details:

*5200 fast cure bonded 1/4" thick x 1-1/2" width pvc board strips the length of tank, 3 strips, 2 on outer edge and 1 down middle. Heavy coat of 5200.

(prior to bonding I etched tank with 80 grit where strips would bond. Also sand blasted the bonding side of pvc strips. Cleaned both tank and strips with acetone soaked rag)

*Let cure 24hrs

*Sand blasted strips, acetone clean. Ran a 1/8" bead of 5200 fast cure down the middle of each of the 3 strips. Carefully lowered tank down into coffin. Filled the fuel tank with the 15 gallons I had siphoned out of the old tank (which was brand new fuel). The fuel in tank provides an even downward weight distribution.

*As the above cured I worked on the securing tabs. I cut (4) pieces of 3/4" thick x 3.5" width x 4" length pvc board, (2) pieces of 3/4" thick x 3.5" width x 8" length.

*Opting not to have fabricator weld tabs, the pvc board was 5200 bonded to top of tank and bonded to coffin liner. Areas of bonding to tank and pvc board was etched prior to bonding, same as previously mentioned.

All in all the install went very well, no hiccups to mention. The tank is elevated off the coffin by 1/4" strips of pvc and centered in coffin with 2" space between coffin and tank. No foam, no glassed in locking tabs, or anything on top of tank.

Essentially the tank is hovering inside the coffin, using pvc board to keep it off the bottom and away from the coffin on 5 sides . If/when water gets in the coffin it drains out via 3 thru holes located most aft that drain into bilge. Barring some unforeseen accident, this is the one and only tank I'll need to install in this boat.

[99yam40]

I think most of us understand, but as usual there will be naysayers in the crowd

[Jason2tpa]

Don't think your getting my drift.. a couple of holes at the bottom of an other wise sealed unit, that will be getting wet, whether it's condensation or back flow thru those mentioned holed doesn't fit the definition of air flow. Air won't flow with openings on 1 end of a sealed cube. Just sayin,but it's your baby. Got me the same setup...always wet in there.

I catch what you're saying. The purpose of the holes are strictly to allow water to flow out.

And I agree, air does not "flow" in and out of the coffin, no matter how many holes and where they are located. Because air does not "flow" under the deck. I believe I didn't explain this and the above principles clearly in my response.

Holes in the liner provide water an escape path into the bilge, thereby preventing standing water at the bottom of the coffin. The tank should not be in contact with anything that traps water between it and the tank. This is the purpose for elevating tank off the bottom using pvc strips bonded to bottom of tank.

[scofflaw]

Fuel coffins should never be completely "sealed", as in being air/fluid tight. If this were so it would promote and enhance crevice corrosion. Impossible to prevent condensation, so it's necessary to allow evacuation of this condensation. The coffin needs to have drain holes to allow water to flow out and air to flow in and around tank.

Don't think your getting my drift.. a couple of holes at the bottom of an other wise sealed unit, that will be getting wet, whether it's condensation or back flow thru those mentioned holed doesn't fit the definition of air flow. Air won't flow with openings on 1 end of a sealed cube. Just sayin,but it's your baby. Got me the same setup...always wet in there.

[Jason2tpa]

When you seal up that coffin there will be no air flow, 100% humidity at best.

Fuel coffins should never be completely "sealed", as in being air/fluid tight. If this were so it would promote and enhance crevice corrosion. Impossible to prevent condensation, so it's necessary to allow evacuation of this condensation. The coffin needs to have drain holes to allow water to flow out and air to flow in and around tank.

[Jason2tpa]

That should work BUT, you may have to epoxy in the blocks AFTER the tank is set in the coffin.

Only because the blocks will/MAY be sticking out more than the tank is wide.

Really, 3/4" to 1" screws are plenty (2 on each corner)..

Thru say the 1/2" block, then just piercing the fiberglass stringers (all pilot holed).. That'd be very solid..

Agreed. I won't be bonding anything until the new tank is in the coffin to confirm measurements.

[TownsendsFJR1300]

There is only 1/2" space on either side btwn tank and liner. I wouldn't think 1/2" of block is enough to give the screw ample security.

However, what I could do is have the fabricator weld the tabs 1/2" from flush with side of tank. Then Id have space for 1" blocks. That sounds good. I'll speak with fabricator to make sure welding tabs setback from flush is ok.
.

That should work BUT, you may have to epoxy in the blocks AFTER the tank is set in the coffin.

Only because the blocks will/MAY be sticking out more than the tank is wide.

Really, 3/4" to 1" screws are plenty (2 on each corner)..

Thru say the 1/2" block, then just piercing the fiberglass stringers (all pilot holed).. That'd be very solid..

[Jason2tpa]

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?

There is only 1/2" space on either side btwn tank and liner. I wouldn't think 1/2" of block is enough to give the screw ample security.

However, what I could do is have the fabricator weld the tabs 1/2" from flush with side of tank. Then Id have space for 1" blocks. That sounds good. I'll speak with fabricator to make sure welding tabs setback from flush is ok.

Originally, when AQ was building the hull, they of course had access to the underside of the liner before they molded it in. Straps were fastened using thru bolts with large fender washers.

[scofflaw]

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.

When you seal up that coffin there will be no air flow, 100% humidity at best.

Poly tank way simple.. Foamed the 4 corners and in the middle as well. The Moeller tank straps are pure junk, the have a plastic coating that falls off after a couple of years and the strap begins to rust.

[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?

[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.

[panasonic]

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

[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.