Fuel tank going back in...

[bbtiller]

What material is best to use to "rebed" the fuel tank?

[Navatech]

What material is best to use to "rebed" the fuel tank?

What material is your tank made off?!...

[bbtiller]

It's the original Bertram tank...fiberglass

[Pete Fallon]

bbtiller,
Before you put the tank back in get some 1/4" or 3/8" flat rubber stock for cushioning material, if you can't find the rubber use some high density PVC foam core board cut almost to the lengthy of the tank, about 1" wide, put a strip 12" off the keel and another about 12 " further out, fasten it with some 4200. Then get the 2 part high density pour foam to fill in around all sides of the tank, make sure it's the high density foam not the cheaper softer foam that absorbs water. Before you put the tank back make sure that your bulkheads are all in good condition and the deck supports are not rotted, you can't get to the bottom of the upright nuts and bolts after the tank goes back in because of the lip on the top of the tank.
Also make sure that you have a drain tube under the tank that is big enough around so if you drop a tool or nuts and bolts down inside you can get them out with a fish wire or a section of 1/2" garden hose. There is nothing more aggravating than to drop under the tank and not be able to get it out until you see the rust stains coming from the back side of the drains at the transom.
For those that need to remove your old fiberglass tank, I found that a length of #19 fishing wire with handles on either end works great for cutting thru the old foam, use a hand saw to start the cuts along the sides then with a guy on each end of the wire use a sawing motion start at the front of the tank and work back to the transom, cuts thru the old foam like butter, you will find that there is a bunch of old wet foam under the tank, it's like snow cone material and has to be removed so the fiberglass can dry out before the tank goes back in. You might have to rent or if you know anyone that has a porta power hydraulic ram to break the seal between the old foam and the bottom of the boat, make sure you use a large wood pad under the porta power ram jaws at the bottom of the boat and also under the tank. those things can put a lot of pressure on the fiberglass surfaces you don't want any holes either pieces.
Good luck with you project.

[Navatech]

It's the original Bertram tank...fiberglass

I assume you're going diesel... I've heard horrible stuff about old fiberglass tanks and modern gasoline (which should really be called E10 as it contains up to 10 Ethanol)...

[bbtiller]

Pete, Thanks for the reply. I have replaced all deck supports since removing the tank and have glassed in a coosa board "deck" to support the tank (replacing the plywood that was rotted and falling apart). There is plenty of space underneath the coosa for drainage to the aft and to fish out what falls down there. I assume when you say fill all sides around the tank you mean the underside and each outboard side up to the height of where the tank will be re-tabbed to the stringer.

Navatech, The tank has been diesel for 20 +/- years.

[Pete Fallon]

bbtiller,
The tanks in the 31's were not tabbed to the stringers, they were just foamed in place. The pour foam goes around the ends and sides between the stringers. Don't forget to re-bond all the fuel fittings when you install new fuel hoses.
Pete Fallon

[Craig Mac]

Actually, my 1977 tank was tabbed to the stringers-no foam.

My new aluminum tank was also put in without foam.

[Marlin]

When I set my new tank I ask the captan about this very issue, his comment was to brace the tank from the top to keep it from popping up due to the foam expansion, laid a couplev2x4,s accross the tank, cut 4short pieces to prop between the gunnel and the 2x4,s, it worked, I was surprised how much pressure developed, had to cut the short pieces with a saws all to remove,

[bbtiller]

Thanks for the tips, I'll follow through with the foam recommendation; my tank was tabbed to the stringer and bedded on the bottom with some sort of material that looked like 5200 but was hard. I assume that was done at the factory because the vertical deck supports had never been removed. For that to have been done at the very least the tabs to the tank would need to be cut and probably the tank removed in order to remove the bolts on those supports.

Thanks again y'all.