under floor fuel tank replacement

[Key west Tom]

I need to replace a leaking fuel tank under the floor of my 1996 Key West boat. This floor does not have a removable cover or hatch so I will have to cut the floor to get to the tank.On the floor there is a "cut line" that is molded into the floor, this looks like this is where I need to cut. question is, when I put it back together, how do I get the floor to look right? I don't want to paint or put carpet down to cover the seam. I was thinking about useing epoxy to make a ledge around the opening and setting the cut out floor back down then more epoxy trickled into the cut line to fill the gap. Can I tint the epoxy to match the gelcoat of the floor?
Any other ideas? how do the pros do it?

 

[DeepBlue2010]

What is your floor finish now? Is it carpet, Gelcoat or what? Can you post a pictures of what you are working with?

 

[Key west Tom]

The whole floor is just gelcoat, The boat is a 1996 20' walkaround, no carpet. the floor has a checker board pattern molded in. No picture at work now

 

[Key west Tom]

The floor has the outline of what needs to be cut out molded into it. The floor where it needs to be cut is only about 5/16" thick becouse the floor gets thinner on the bottom and also a little thinner on the top side, then there is a "cut line" that is about 1/4" wide and about 1/16" deep all the way around where it would need to be cut.

 

[Woodonglass]

You want to make absolutely sure that you only cut the depth of the deck. Don't want to hit the tank and cause sparks or...Well you know!!!
You'll use Cleats glued to the underside of the existing deck to support the decking you cut out. See below...

 

[alldodge]

Haven't done the repair as yet, but they make patterns to reapply gelcoat. Here is one of the patterns and there are several. Basically apply a thick coat of gel then lay mold down over it.
http://www.iboats.com/Gibco-Flex-Mo...kNoIiZ99BsvemzMu4yYfuu9rfclx7lzHZkaAjWx8P8HAQ

 

[Key west Tom]

Thanks woodonglass, That is what I was thinking, I was planning on making the "cleats" from layers of fiberglass and epoxy, using epoxy to bond to underside of deck and epoxy to bond the patch back down. but what should I use to "seal the gap" at the cut line? You know, the cut line that yo will see from the top. What is this peanut butter you speak of?
One more thing, the sides of the tank coffin are right under the long "cut lines" but the sides of the tank coffin don't reach the bottom of the deck, so my Cleats will fit on top of the coffin sides but under the deck and will gain support from the sides.
Alldodge, thanks for the info but the check pattern ends about an inch on each of the cut line. But this is good to know.

 

[Woodonglass]

Peanut Butter Recipe....

 

[Key west Tom]

Thanks for the recipe! what are the best places to buy the items? also should I use epoxy resin to make the peanut butter and the "cleats" that you showed in your earlier post?

 

[DeepBlue2010]

The cleats are made out of wood. Most likely you will find them already installed under deck. Those "cut" lines you mentioned earlier are most likely the separation lines between the middle board and the rest of the deck and if this is the case, you will find a cleat already installed. Just make sure you set you saw depth to a hair shy of the total deck board you are cutting.

You can use epoxy to make the PB if you will be working with epoxy but if you go with epoxy for the entire job, you will not be able to use gelcoat to finish the job.

 

[Woodonglass]

PB can be made from either Poly of Epoxy. I'd use Poly. As DB stated cleats are wood stuck on with PB and coated with resin and CSM because like DB stated epoxy and Gelcoat don't Play well. Your boat is made from Polyester resin and Gelcoat is basically poly resin with some additives and coloring.

 

[Key west Tom]

Thanks, once I find a tank that will fit, most likley a plastic tank, how do I install it? I see on the Moeller site they say not to foam it in place. but I have seen other sites that say you can use foam on the cornners only and use the Moeller mounts. what do yo all think?

 

[alldodge]

Opinion: If the tank was foamed in originally then re-foam it back in. The foam is used to supply hull support and keep the flexing down. The foam will stick to aluminum but no so much on plastic. I replaced my tank last year and reinstalled aluminum

 

[ahmincha]

speedytanks.com I had mine made out of aluminum not to expensive
As far as installation put back as it was. Mine was set on neoprene and foamed in

 

[Key west Tom]

everyone now says not to foam in an aluminum tank, will make pin hole leaks.

 

[DeepBlue2010]

And they are correct. Foaming in the tank - untreated - will increase the chances of pitting. Either treat the tank before installing if you insist on foaming it in or provide a mechanical support from the top/sides to keep it in place after installing. I would treat the tank no matter what. If interested in painting the tank just search the forum for painting aluminum or just ask

 

[Woodonglass]

This should be very helpful..http://www.yachtsurvey.com/fueltank.htm
The MFG Foam in the tanks for expediency purposes.
Here's the USCG regs...http://www.custommarinefueltanks.com...ance_guide.htm

It should be noted that Back Yard Boat builders are NOT subject to USCG Regs.when replacing a tank, But... it's NOT a bad Idea to follow them.

 

[alldodge]

everyone now says not to foam in an aluminum tank, will make pin hole leaks.

It is true IF the tank is foamed in and IF water gets between foam and tank, then the water can eat away the aluminum over time. My 1994 tank was getting eaten but had not eaten thru, but replaced the tank anyway. tpenfield reinstalled his same tank because it was not eaten as much as mine. Now if you can keep the water out, nothing will happen, but your still talking more then 25 years.

Now water in the tank can do the same thing. Another good thing to stop it is to epoxy coat the tank on the outside, which we both did prior to reinstall

Its your boat, but I would think real hard about taking a boat which was foamed in and not foam the tank back in.

 

[Woodonglass]

Condensation will occur even if water does NOT get to the tank. Going from hot to cold always creates condensation. Coating the tank with epoxy and or other methods will alleviate the moisture from getting to the aluminum. Not sure I understand your concerns AD???

 

[alldodge]

Don't see condensation being an issue with being encapsulated in foam, for that to form it needs moist air next to something colder. Never see moisture develop on the underside of my tin roof with insulation against it.

Don't know how else to explain the issue with foam around a tank in a confined compartment which may be a structure item WOG. Just my opinion as a dumb ol hillbilly