Plywood Fuel Tanks

[DogCavalry]

This used to be an excellent way to make a tank: a strong plywood box, glassed and coated liberally and carefully with the resin of your choice. Then the corrupt and incompetent b-tards in Washington mandated corn ethanol in gasoline, simultaneously wrecking boats, damaging the environment, and robbing honest working fellows of more tax dollars.

However, there are now a number of resins formulated to be impervious to ethanol. Thanks @BlueBell , this never occurred to me.

And my fuel tank guy takes about a year to complete a new project. It turns out that people who are really good at things are quite busy. On the other hand, you can hire a useless knob immediately. No waiting. I'm not waiting a year for tanks.

So I mean to make my own tanks. On the even less typical side, I read that lexan is fine with gasoline. How about a lexan lid? Talk about your inspection port. No need for a sender either.

 

[fallguy]

This used to be an excellent way to make a tank: a strong plywood box, glassed and coated liberally and carefully with the resin of your choice. Then the corrupt and incompetent b-tards in Washington mandated corn ethanol in gasoline, simultaneously wrecking boats, damaging the environment, and robbing honest working fellows of more tax dollars.

However, there are now a number of resins formulated to be impervious to ethanol. Thanks @BlueBell , this never occurred to me.

And my fuel tank guy takes about a year to complete a new project. It turns out that people who are really good at things are quite busy. On the other hand, you can hire a useless knob immediately. No waiting. I'm not waiting a year for tanks.

So I mean to make my own tanks. On the even less typical side, I read that lexan is fine with gasoline. How about a lexan lid? Talk about your inspection port. No need for a sender either.

Make sure the Canadian coasties don't/can't ever hang you on that idea first.

It'd suck to make a tank that you can pressure test to 3psi and get boarded and be told you have a problem. I'm still worried about the stupid charcoal canisters.

 

[DogCavalry]

Thankfully we don't have that yet.

 

[Rumars]

You can always try your hand at HDPE welding.

 

[DogCavalry]

You can always try your hand at HDPE welding.

Is that something I might realistically do? I know I can do a proper job of ply boxes, then glass them. But I know nothing of HDPE welding.

 

[fallguy]

What epoxy?

 

[DogCavalry]

What epoxy?

There are some products formulated these days, specifically for organic solvent resistance. Gasohol included.

EP41S-1 Product Information | MasterBond.com https://www.masterbond.com/tds/ep41s-1

For example.

 

[Barry]

Construction Standards for Small Vessels (2010) - TP 1332 E https://tc.canada.ca/en/marine-transportation/marine-safety/construction-standards-small-vessels-2010-tp-1332-e#wb113

This is Canada's Construction Requirements for Small Vessels. The pertinent fuel tank construction section is 7.3. The section says that the construction methods etc must meet ABYC H24? I would doubt that an insurance surveyor would pass a wood fuel tank. Not sure if it would pass the non combustible requirement.

Also note that inspection plates are not allowed on gasoline fuel tanks.

 

[Rumars]

Is that something I might realistically do? I know I can do a proper job of ply boxes, then glass them. But I know nothing of HDPE welding.

It's doable if you dedicate some time for practice and some money for the welder. Of course you could just as well ask around to see who does plastic welding and have them do it, maybe you don't have to wait a year. Are good metal welders so thin on the ground over there? Since you are contemplating making it out of glassed ply you don't need crazy shaping techniques, cut and bend the metal yourself and find someone to weld it.
If I wanted a metal tank without welding I would have absolutely no problems using angle iron, screws, rivets, gaskets, solder, JB Weld, etc. For example glavanized steel with flat locked seams soldered over, Al sheet riveted on angle profile sealed either with a gasket (solid or from a tube) or with epoxy paste (plenty made for the exact purpose of sealing a gas tank).

 

[fallguy]

Construction Standards for Small Vessels (2010) - TP 1332 E https://tc.canada.ca/en/marine-transportation/marine-safety/construction-standards-small-vessels-2010-tp-1332-e#wb113

This is Canada's Construction Requirements for Small Vessels. The pertinent fuel tank construction section is 7.3. The section says that the construction methods etc must meet ABYC H24? I would doubt that an insurance surveyor would pass a wood fuel tank. Not sure if it would pass the non combustible requirement.

Also note that inspection plates are not allowed on gasoline fuel tanks.

what does the last sentence mean? Can you expound?

 

[Barry]

7.3.1.5 A GASOLINE fuel tank shall have no openings in the bottom, sides, or ends.

7.3.1.6 Clean-out plates shall not be installed in GASOLINE fuel tanks; clean-out plates may be installed in the top or sides of DIESEL fuel tanks.

 

[DogCavalry]

Gotcha. No cleanouts.

I find in the literature, requirements for cores in frp tanks above 20 gallons. They give, as examples, balsa and pvc. I don't think plywood has inferior fire resistance to balsa.

But if a welded HDPE tank can be as good as a spun cast tank, that's promising.

 

[DogCavalry]

@Rumars , it's the combination of the hand skills, technical knowledge of regulation, and time to do the work that's thin on the ground. If I design every last detail I can get it fabricated by a competent shop.

 

[Rumars]

A gas tank is just an airtight box. Unless you need compound curves (wich involve an english wheel) all a fabricator does is cut and fold some metal. Any halfway competent metal roof installer or auto body mechanic can make you one, and if they can't weld themselves to the required standard they usually have a buddy who can. Fittings are all available online. You just make a pattern out of cardboard and ducktape and give it to them.

If correctly done a welded HDPE tank is as good as any, entire speedboats are made this way. Quickest way to find someone is to ask the local plastics distributors, they know what their customers do.

Google "riveted gas tank" you will find plenty of examples and tutorials from the homemade aircraft crowd (they also make fiberglass tanks, usually with vinylester). Materials of choice are under 1mm Al sheets (can be bent by hand), solid and blind sealed rivets and a polysulfide goo. The same techniques can be used with stainless steel, monel and bronze sheet if you don't like Al.

 

[DogCavalry]

Thanks @Rumars . Every conversation with you is educational.