Need advice on installing a fuel tank.

C

clshortt

Member
Joined
Jan 1, 2000
RO Number
2982
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28
I'm in the process of repairing some rot in a 2000 Glastron CarlsonCSX21. Basically the fuel tank was never mounted correctly from the factory. The small strips of foam under the tanks worked their way out and the tank rubbed several holes in the inner fiberglass. This let water into the balsa core of the hull.
I removed the tank and cut the inner fiberglass out, removed the rotten balsa wood, drilled a few vent holes in the rear, under the engine where the balsa was wet, but not rotted. The boat has been out of the water and drying for more than two years now. I have the moisture content to below 15% everywhere I can get my tester into.
I am ready to start putting it back together but I want to formulate a plan to install the tank correctly.
From what I have seen, the fuel tank of other boats seem to fit nicely in an area between the stringers and have bulkheads in front of and behind the tank. Mine has no such thing. There is 12 inches on each side of the tank between the tank and the stringers. Several inches between the tank and the rear bulkhead and many inches between the tank and the bulkhead in front of the tank. The tank was only held in place with two 2x4's "toenailed" into the stringers.
My question is would it be prudent to install and glass in some walls around where the tank sits after installing the new foam coring?
It's hard to describe my situation but I can post pictures if that would help.

thanks in advance for your advice.
 
Yes, pictures. Is your tank aluminum or fiberglass?
 
I doubt glastron would have use fiberglass tanks.

The biggest concern with mass production boats alum tanks is that the moisture under the tank eventually corrodes the aluminum resulting in leaks. Have you inspected the bottom of the tank? I would also try to inspect the inside, watch the fumes, to make sure the tank is even worth re installing. You don’t want to do all that work just to have it pop a leak a few months from now.

If I understand correctly the tank sits on the inside of the hull, correct? I ve never heard of a tank rubbing thru fiberglass, either it wasn’t secured and / or the top layer of the cored hull was paper thin.

If you are going to glass in something around the tank to keep it in place, make sure you have adequate limber holes for any water to drain out. Avoid plywood which can soak water inlet marine plywood soaked with epoxy. Coosa board is probably the best for this.

Solid rubber strips are probably the best material to put between the tank and the hull, I guess they could be epoxied to the hull to prevent them from moving.
 
Thanks for the advice so far.
I will get some pictures uploaded. The tank is plastic, nylon I believe. Looks to be either vacuum formed or molded. Well, the tank was set up from the factory to be sitting on some type of black foam rubber strips about 2 inches wide and maybe 1/2 in thick. The tank is 60 gallons, sort of v shaped with a flat bottom where water could run under the tank. The rubber strips were held to the tank with a sticky backing (which failed). The only way the tank was held down were pieces of wood across the top. The tank was not firmly held in place and the movement of the tank eventually peeled off the rubber strips. As more of them rubbed off, the looser the tank became. It eventually rubbed through about 3/8 in thick fiberglass inside the area where the tank sat, at the corners. Thats how the water got into the core./
 
Surprised the molded tank didn’t fail instead of the fiberglass. Did you inspect the tank where it rubbed on fiberglass?
 
In the photos, the dark, black area at the bottom of the hull is the exact footprint of the tank. You can see the area under the tank that is open to let water flow under it. The strips of rubber worked their way down into this open area and created a dam. That is how the water got up to the hole in the fiberglass.
 
PascalG said:
Surprised the molded tank didn’t fail instead of the fiberglass. Did you inspect the tank where it rubbed on fiberglass?
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Thanks Pascal. I did, and it seems to be fine. There is evidence of contact, but no real damage. The tank does not leak. There was no sign of gasoline in the bilge.
 
those do work, but if you hit the little 'insert image' button on the post - the one on the top row between the paper clip and the smiley, you can embed the pic right within the post.

I was sure you were going to say aluminum; with a non-metal tank, I believe you have options you don't have with aluminum - You can have the tank sitting right on the glass, or right up against stringers, straps, etc. which are holding it in place. With aluminum you have to be most concerned with keeping it dry, and especially keeping anything that is holding it in place from absorbing any water. Your only real concern is keeping it from moving. Foam would not be my first choice. Strapped firmly in place would be my plan.
 
alk said:
those do work, but if you hit the little 'insert image' button on the post - the one on the top row between the paper clip and the smiley, you can embed the pic right within the post.

I was sure you were going to say aluminum; with a non-metal tank, I believe you have options you don't have with aluminum - You can have the tank sitting right on the glass, or right up against stringers, straps, etc. which are holding it in place. With aluminum you have to be most concerned with keeping it dry, and especially keeping anything that is holding it in place from absorbing any water. Your only real concern is keeping it from moving. Foam would not be my first choice. Strapped firmly in place would be my plan.
Click to expand...
Thanks alk. I tried that and it asks for a url for an image. The only image storing I have is through OneDrive. I tried posting the links above in that and I got a message saying it was unable to access that link (or something like that).

My plan was to add a couple of additional "stringers" along the sides of the tank and then a couple of bulkheads in front of and behind the tank. I plan on using some rubber mats under the tank that will be attached to the hull underneath the tank.

I cut out the fiberglass that is dark in the pictures and removed the wet and somewhat rotted balsa core in the area right under and just beyond where the tank sat. I will be replacing that with Divinicel foam board and re-glassing the entire area between the existing stringers. The wood in the hull at the edges of my cut was not wet. I do have some de-lamination of the hull in other areas forward and aft of the tank area, but no rotten wood that I can find.
 
I have no idea what I'm doing or if my plan is correct. I'm just winging it here. This boat is 23 years old but in immaculate condition (other than this area). It also has less that 300 hours on it. It's also one of only a hand full of the Carlson CSX21 that came from the factory with the fuel injected 454 and the Bravo I drive.
 
clshortt said:
Thanks alk. I tried that and it asks for a url for an image. The only image storing I have is through OneDrive. I tried posting the links above in that and I got a message saying it was unable to access that link (or something like that).
Click to expand...

not to hijack your fuel tank thread - but the 'insert link' button should bring up the URL prompt. The 'Insert Image' button should allow you to drag and drop, and click to select a file.



Img3.png
 
You could come up with a better way to mount the tank than the factory did, by building some stringers to hold the tank in place you can use a rot resistant wood like mahogany, I did that when I redid the deck on my old '88 Four Winns, the original design was cheap pine which rotted, the mahogany is still solid after 16 years....did that back in 2007. Old cell phone pic:
tank mounting.jpg
 
clshortt said:
May be my browser? I don't know. Sure would be nice if it did work for me. Here is what I see when I click on that button.
Screen shot of button.
Click to expand...

strange, do you mind trying again (after closing your browser and reopening) ? Might be a forum setting, which I just changed hopefully.
 
LouC said:
You could come up with a better way to mount the tank than the factory did, by building some stringers to hold the tank in place you can use a rot resistant wood like mahogany, I did that when I redid the deck on my old '88 Four Winns, the original design was cheap pine which rotted, the mahogany is still solid after 16 years....did that back in 2007. Old cell phone pic:
View attachment 1309
Click to expand...
Yes, this is something like what I had in mind. Here is a rendering of sort of what I am planning. Wish I could get my picture thing to work!

 
Artboard 1-100.jpg
alk said:
strange, do you mind trying again (after closing your browser and reopening) ? Might be a forum setting, which I just changed hopefully.
Click to expand...
Hey! That seemed to work! Thank you !! Makes things much easier....
 
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