Stainless steel (feul)tank

[Danielsan]

Hi,

I can't find a tank (fuel and water) that will fit to the place where I would like to have them.

I have a triangular shape formed by the hull at the bottem of the hull formed by a 22 deg transom. and the chine flats. making an area of 6000cm2*140cm in length, giving me +/-0.84m3 of possible tank volume, so I could easely fit in two or tree 316stainless steel(sheet metal) welded tanks one for the water, one for the fuel, and perhaps one for waste water.

Would the material be a problem?

Greetz,

Daniel Peeters

[DGreenwood]

Your first consideration will be: is it CE legal to use the material. Others here can help you decide if that is necessary.
Outside that I can tell it will work if properly built.
It is imortant to design them with the proper baffles. You should always use a folded corner and put them at the top of the tank when possible. Use bends on the bottom as much as possible. Weld with 317L or other low carbon rods. A skilled welder can make a big difference in how the tank holds up against corrossion. As you probably know the Stainless steel is fine except where the welding has caused some seperation of the alloy. Don't forget to plan your cleanouts, sender holes, pickups and returns well before you start. Adding them later is a major pain.

Good Luck

[Danielsan]

the corrosive resistance after welding is one concern. Could I do this in an other material? For sender-pickup etc. I could foresee one big hole with all the necc connect?

Greetz,

Daniel

[yipster]

stainless is fine but did you have a look at the www.vetus.nl sales program? thought they also do custom size plastic tanks.

[DGreenwood]

I almost always put the pickup returns and senders in a cleanout type lid. This helps in a number of ways if you have to work on the pick-ups or senders...allows rethreading or replacement without contamination.
I also (if I have the room) weld into my fuel tanks a short piece of 2 or 3 inch pipe just below the pick up which act as a resevoir for the guck (technical term) that collects in the bottom of tanks. If you have access to it you can put a petcock on the bottom of the cup to allow occasional maintainance tapping off of water etc. All expensive stuff but it makes mechanics smile.

[stevel]

Not that I would trust MY memory...

...but I seem to remember that the Coast Gaurd and/or ABYC prohibit the petcock idea for a fuel tank because all openings have to be at the top of the tank. If you are building your own tank, however, you could run a line inside the tank from the "gunk" sump so that you could pump it out from the top. For water, the simpler petcock would be okay.

[Danielsan]

Yep Ypster I had alook at them but I didn't find custom made tanks. I did find the complete inlet, outlet, return line system.
They have a sort of triangular shaped tank that could work, but i would need to get some more free space I now have 1400mm I would need 1700 for that one.

I will search a bit further.

Ther was a Polish company who could make them custom for a certain price per liter.
But I also have a fine machining company that also do welding etc. I am waiting for their offer.

Thx,

Daniel

Ps will you be visiting the boot show this WE?

[Ssor]

The work boats in Maryland USA often use aluminum beer barrels for fuel tanks. I should think that they would work for waste or water. When I rebuilt my boat I made tank shaped thin aluminum forms and covered them with fiber glass and resin. After they were complete I cut holes in them for fittings.

[preacherman]

There is a common belief in my community that stainless tanks produce more condensation than other metal tanks, ie. alu or black iron, excluding those made of pp or other synhetical materials as accepted by the CE authorities. I had (presumably) also similar experiences in the past.
Yipster you could know it, is there something true with the sweating of the st.tanks or was it my sole imagination ?

[Ssor]

Condensation only occurs in partially full tanks. Any time the tank and its contents are below the dew point temperature, the potenial for condensation exists. I placed an air drier( silca gel)in my fuel tank vent line to help minimize this problem, in seven years of service I have had no problems with water in my fuel tank.

[yipster]

your rite Ssor, thats why tanks should be filled up.
stainless tanks condense more... mmm, could be, dont know, got ss for fuel (and water seperators and a siphon) and plastic for water.

[Danielsan]

As I am building the boat by myself, I suppose I could let go the stainless steel tanks en make some myself in GRP?
just need to use the right resin?

[D'ARTOIS]

Danielsan, you are definately looking for problems where they do not exist. First of all, condensation in fueltanks is a problem that exists as long as the combustion engine. Unimportant of what material the tanks are made. SST is just fine, if you can weld it together and know how to make a proper design. Just plain steel will do as well, if sufficiently coated on the inside to prevent rusting. FRP will do as well - in agriculture are 1000's of FRP containers and tanks, also used to store dieselfuel and/or regular fuel. Then there are the collapsible tanks that will shape itself to a specific form.

You get water in your tanks due to the fact that many gas stations storage tanks are often contaminated with water if they are not drained from time to time. That is the main cause - drain your tanks regularly and you won't have this problem. So provide your tanks with a drainlock.

It's not all that difficult.

[Ssor]

If you decide to make your own tanks, you should takeoff the shape of the space where they will be located and make patterns. After you have done that, you will be able to assemble a tank shape to test the fit. When you are satisfied with the fit, then you can make the tanks in the material of your choice.
As much as water is a problem in fuel and because my fuel tank is only 40 L. I purchase my fuel dispensed into protable containers. This allows the water to go to the bottom of the container and I don't empty the last 100cc.

[webbwash]

You can fold the metal tank once you have the patterns set up -- I show a left and right of the same tank minimising weld time -

With a cover plate on top you can have all lines leading into the tank -- the one shown is about 6 inches diam -- for grey water you want the fill just below the vent and the suction at the lowest level -- make it fit up to the marina-side waste discharge suction hoses.
For fresh water you want a large fill pipe extending just into the tank with vent just above that - The deep suction on a hand pump to get the grunge out and the regular suction just above that for normal use.
Tank Level Readers/Sensors can be installed in the same screw on cover plates and don't forget disconnect fittings so that you don't have to tear the boat apart just trying to get the cover off. Second cover at other end of tank is most useful in keeping things clean. And baffles as required, can be welded to bottom shown so that shape is maintained and minimise welding.