Fuel Tank Shape?
 

I guess I am going to go ahead and replace my fuel tanks. Not sure the 96 gallon tank will fit when moved forward. Trying now to decide what to go with. I am going to put two tanks back in somewhere around 130-140 gallons and jam them both all the way to the front bulk head. I see most guys going with rectangular tanks, has anyone put the v-shaped belly tanks up front? If you have, how did you do your tank step for the tank to sit on?

Most people hang them off of the stringers with L brackets. Have them welded to the tanks when you get them made. Then glass blocks to the sides of the stringers then screw the brackets to them that way air will circulate around the tank.


I might be interested in the old tank if it is in fair shape. Let me know if what you plan to do with it.

I agree with Frizzle on the mechanical fastening and air circulation. If it were me, I'd sit the tank(s) on a platform with an oil resistant ribbed mat under. Front tanks take a beating- more support is better. aluma prep and coal tar epoxy wouldn't hurt either. Don't forget to properly bond fill/ tank/ vessel negative. A-2 fill hose with double hose clamps, no dips; at least B hose for the vent- no dips; A is better. I've checked out the new A1-15 fuel pick up hose- looks like good stuff- basically polyethylene fuel tubing with A1 hose around it- should be a once and done deal: I'm using it on my project. I'd follow all of the mandatory and voluntary standards as required in United States 46 CFR 182.455 and ABYC H-24- available on the web.
If it were mine, I'd try to keep the tank out of/ away from bilge water. As a last attempt to prolong tank life (prevent corrosion) on my 50 year boat, I am installing a flush system (tied into vessel fresh water wash down system) to flush my tanks with fresh water- I installed my tanks in separate bulkheaded tank compartments with one 1" drain hole aft on tank support platform. When tested with regular city water pressure, tank compartments flooded up 5-6". This should wash off any salt off tank tops, and lower areas/ bottoms of tanks.

I went with 50 front/ 70 gallons rear of console step down (all the gas I could fit) to have a built in reserve/ ability to keep/ get weight out of the stern when I want to.

As a good friend of mine reminds me: it's a sickness.

If you have custom tanks made...you can have the shape made any way you want, that way you can get the most gallons for the space.

On my rebuild I had the guy weld on tabs (see pic) then those where bolted to the bulkheads. The tanks had a starboard type runners expoxied on the bottom to allow air circulation and water to flow under the tank.

Attachment 6602

Hope this makes sense. You can go thru my rebuild page and see more.

I had Sunshine provide a 118 gal rectangle for my 23'. I kept my forward deck box. I hung it as mentioned above while also sitting on a glassed in, full length shelf. No foam and no rubber under the tank. The carbon in rubber is supposed to have an adverse affect on aluminum. You want it on something, not rubber. Pascoe outlines this in his installation procedure.

Ba I did my tanks like old school did .with the keel stringer in place ther really wasn't much to be gained with a v type tank. I was able to put two tanks totaling 130 gal. without any problems in my 23cc

Thanks everyone. I think I'm gonna go with two tanks approximately 130 gallons total (85&45). I am planning on putting the large tank all the way forward and the smaller one behind it and only fill it when needed.

Neoprene rubber has no carbon in it.Thats what my fuel tank fabracator gave me for my tank install. 2" x 1/4" thick strips glued on the bottom with plenty of 3m 5200 so there are no gaps or air pockets between the rubber and tank where water could collect.Tank is 8 years old now and still looks new.

I'm pretty sure most synthetic rubber compounds, including neoprene, are derived from hydrocarbons. Their chemical formulas contain a lot of "C"s and "H"s.

I can't say either way if neoprene reacts with aluminum. The corrosion that takes place where rubber is in contact with an aluminum tank may just be crevice corrosion. If it were galvanic, I would think the whole tank would act as an anode.

Someone posted this a while back. http://www.yachtsurvey.com/fueltank.htm
I can tell you that definitely the neoprene or whatever rubber type strips used under the original fuel tanks caused corrosion. I still have mine and their is corrosion under the strips; I'll post pictures later. With out question the more air circulation the better.

We use Buna-N rubber under aluminum tanks.
No carbon, nitrile rubber, and it's white, not good for UV exposure, but under a tank who cares.

http://www.mcmaster.com/#86795k67

I used some 3/8" x 1" strips of azek running the length of the tank. When the coal tar epoxy was still wet I set them in it and now they are really stuck with no voids.

Someone posted this a while back. http://www.yachtsurvey.com/fueltank.htm
I can tell you that definitely the neoprene or whatever rubber type strips used under the original fuel tanks caused corrosion. I still have mine and their is corrosion under the strips; I'll post pictures later. With out question the more air circulation the better.

My fuel tank was foamed in on the sides and placed on a solid panel. The tank was only coated (black looks like tar)on the top panel, not the bottom nor the sides were corrosion treated.The bottom of the fuel tank sat on three foam strips. The corrosion on the bottom took place between the foam strips and the tank. There was virtually no corrosion anyplace else. Only where there was foam on the sides or foam strips did the corrosion take place. As others have stated keep moisture from being trapped between your tank and materials that trap moisture and your aluminum tank will last longer. This is the original tank so after 40 years she'll get a new one.