What's under your fuel tanks?

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pat.jack

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C Dory Year
2003
C Dory Model
22 Cruiser
Vessel Name
C-renity
Hi Folks,

I will be taking my 22' Cruiser out of winter storage on Monday, and I was thinking of a few projects I need to work on this year. One question I have is my fuel tanks. My 2003 model boat has (2) 20 Gal plastic tanks that sit on the hull of the boat. I recall a discussion at one time that it might be appropriate to put some sort of pad under the tanks to help prevent wear/abrasion to the tanks. I checked the forums and I could not find a recommendation regarding this. Has anyone made a mod to add some sort of pad to support the bottom of the plastic tanks-and have pictures? I would appreciate it.
Regards,
Jack Howell
 
The tanks should be strapped down, and not move. I am not aware of any of the tank bottoms of the aft tanks abrading thru…but it is possible. At least one plastic tank in both a 25 and a Tom Cat 24 have leaked, but probably not due to abrasions.

The plastic tanks are not susceptible as aluminum tanks to salt water trapped next to the tank.

If you put something under the tank, then you would have to raise the cleat to keep them from shifting. There is a moderate thermal expansion of the tanks, so they cannot be restrained to the point that this thermal expansion were to cause an issue.
 
Ours had two flat rubber 1/2 wide rubber strips adhered to the bottoms running front to back. I couldn't see any issue with them so left them on when I re-installed. If they were not already there, I was planning to add something similar.

Greg
 
I replaced my original, 25-gallon tanks with new, 23-gallon tanks. This was part of an entire fuel-system replacement that started because of the very poor original installation of the positioning cleats and hold down straps. Anyway, I added rubber beneath the tanks. Possibly it just made me feel better, but I didn't like the way the flat-bottomed tanks sat on the curved boat when they are supposed to be fully supported on their bottoms. I got a durometer of rubber that I felt would help minimize any possible "bending" of the bottom of the tanks by "taking up the slack," but I don't really have any way of knowing whether it helped or not. At any rate, I don't believe it hurt. There is more coverage than I would typically describe with "strips," but there are in fact spaces between various sections, to allow drainage.

I tried a mockup with some Dri-Deck tiles I had lying around (I had seen them used by someone else), but they not only put the tanks up higher than necessary (for which I would have needed to use taller cleats), but were slippery (vs. the rubber I used, which is grippy and makes the tanks "want" to slide around less).

Another use of the rubber, for me, was to allow me to place my new cleats, which are made of fiberglass angle, with the bottom "leg" of the angle tucked under the tanks. The rubber holds the tanks up so they don't contact the part of the cleat that is tucked under.

By the way, at the time I did this project (a year/two ago), I got my new tanks through Triton (who were building the C-Dory) and they were using similar rubber strips under the tanks (in fact, I used some stripping I got from them and then supplemented it with some sheeting I bought from McMaster Carr). I tacked the rubber to the hull with dabs of 3M 4000 during the installation.

Another way I used some small pieces of the rubber was for shims to adjust to the tanks' expansion. Moeller specifies a certain percentage gap be left for expansion, and they are not kidding! (None looked to have been left in the original install, which contributed to the problems.) I left the amount they said and shimmed the gaps with sections of the rubber (so the tanks would still be held tightly), and then was able to remove strips as the tanks expanded over time. I would have been sorry had I left any less expansion space.

I don't have any photographs at the moment, and am away from the boat.
 
Thank You all for the very thorough responses. I have some good options. I will pick up my boat on Monday and hopefully get it ready to enjoy for the boating season up here in upstate NY. Our season is short, so hopefully I won't spent a lot of time working on it!
Jack
 
Those tanks are tough. When you pull the tanks and inspect the bottoms I doubt if you will see any significant abrasion.
I took sandpaper to the non skid under the tanks just to make myself feel good.
 
Chester":2wes0xi4 said:
Those tanks are tough. When you pull the tanks and inspect the bottoms I doubt if you will see any significant abrasion.
I took sandpaper to the non skid under the tanks just to make myself feel good.
Click to expand...

Non Skid :?: Steve, do you have non skid on the cockpit sole? Too? I don't have nonskid in the cockpit, so I sure would not expect it just under the tanks.

Harvey
SleepyC :moon
 
The cockpit nonskid looks like they took a coarse push broom to thick gelcoat or some-such.
It's nothing like the patterned nonskid on the fore and side decks.
 
Thanks. It sounds more like what I have. It is just not smooth. On my cockpit sole I have Drydeck so don't really notice the surface under that much.

Harvey
SleepyC :moon
 
I really wouldn't spend time worrying about it. If given long enough, the place those tanks fail is where the mounting screws go into the sending on top from galvanic corrosion or electrolysis. Sometimes a seam can fail too....As noted by others, they are tough - far more so than they appear.
 
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