Can someone give me some tips on building fuel tanks?

I'm using foam shaped to my needs and then I plan on glassing the foam, then removing the foam afterwards from the inside.

What weight of cloth should I be using and how many layers?
Anything else I need to know?

Ronnie, contact JR on this, he's done it. The lost foam method is ok, you will need it to be around 8 to 12 ounces thick, a layer of 2 ounce and two layers of four is good.

Then seam tape it up after you cut it in half and get all the foam out.

On mine, I dremeled a hole, put the stopper in and tightened down on it and then aeropoxied the crap out of it, no leaks.

It's not a bad project,

Sean

Ok that sounds easy enough.

Yeah I was gonna talk to JR but I think he went the entire plug and mold route and thats more than I want to put into it time wise

I read Rich Fong's RCJI article on this topic. It seems fairly straight forward, but I still have one question; how do you form the spout for a removeable stopper assembly? Hope you don't mind me tagging my question onto your thread, Ronnie.

Tom

.......search funtion is one of the greatest on RCU..........try yourself!

http://www.rcuniverse.com/forum/m_57.../tm.htm#575805

http://www.rcuniverse.com/forum/m_13.../tm.htm#132470

http://www.rcuniverse.com/forum/m_18...tm.htm#1830104

Best regards,
Gerald

I didn't make my stopper removeable without some serious work.

yeah I never thought about making the spout, just an opening for the stopper.

I remember someone posting on making a tank using foam then econocoating before fiberglassing.

He then used 1" copper tube for the stopper neck I think or was it 3/4" im not sure. Basicly cut the copper off and glued it into the whole cut into the fiberglass tank.

It's the middle thread refrenced by Gerald a few posts back. Kevin W posted it.

Sorry Seanreit, missed something out of a previous thread.....

Originally posted by Seanreit:
This was done at my local hobby store where they are able to vacuum canopies and r/c car bodies. This vacuum mould is strong enough to mould several tanks out and very easy to make. Sure you have can find such vacuum machine at a local hobby store??

Shock, I use a simple conventional gasoline rubber stopper (I think from Dubro...?) and glued a mating aluminium ring in the fuel cell with epoxy/microballoons, (Also used for the seam) look at the first thread I mentioned. Most people said the micro balloons wouldn´t work, will start leaking, but with two models in action for 5 years now all tanks are still leak proof with no signs of brown colorisation in the flanges..

Best regards,
Gerald

Use the brass/aluminum stopper assembly that BVM sells. You just drill a hole in the finished tank (before joining the 2 halves), bond in the brass recepticle into the tank from the inside.

Bond the two tanks halves together, then screw in the threaded "stopper" with the clunk installed from the outside, into the brass recepticle. Easy

Ronnie,

Making fuel tanks with the lost foam method is pretty easy still. If you have a bandsaw and a dremel with the wand extension it will be a lot easier. Start will glassing the foam plug. I'd go ahead with Kevlar and use 1.7oz satin weave followed with a 4.8oz satin weave. After that cures, take your tank and run it through a bandsaw and then use a dremel sanding drum to remove the foam from each half. Then you can use some sort of liquid that will eat the rest of the foam out. There should not be much foam left so the mess should be minimal. Then clamp the two halves together and run a beed of epoxy and cabosil around the seam. Smooth it out and let is tack up. Then come back with a band of 4.8oz satin weave, wet it out with epoxy and place that around the seam. Once it cures you should be good to go.

As far as the tank fittings. You can use just about anything you want depending on whether or not you want to make the tank serviceable. I believe you will need a 3/4" size hole for the stopper type fittings or you can install some panel mount Festos prior to gluing the tank together which is what I did.

JR Gautreaux

I agree with the lost foam / one off method fro making fuel cells. This is an alternative way - quite quick:

1)Build your fuel cell from 2 mm balsa sheet using cyano glue. You can make really nice looking symmetrical cells or cells with two different cross sections this way. This way you avoid the sanding and shaping of the foam (messy). And it is quick!

2) Cover the entire outside of the cell with brown packing tape. This tape is common i Europe. Nothing sticks to it. To be sure make a test with epoxi on your tape before you carry on. Also quick !

3) Laminate the entire cell with two layers of 150g/m² glass fibre. This is the time consuming part.

4) Cut it in half (when cured) and remove the internal bits in large fragments as the tape peals of easilly from the epoxy. Use compressed air if you need help. You will find the inside is nice and smooth!

5) Drill holes for Ø5mm brass tubes and fix them with epoxy mixed with micro baloons on both sides (or Hysol).

6) Fit the tygon hose and clunk

7) Join the two halvs with a 20 mm strip of g/f.

8) There you go !

Good luck !

I tried it using the method described in RCJI.....it is very similar to the method JR describes above. I found it very difficult to get the Kevlar to shape around the edges and lay flat. I was just trying to make rectangular/brick shaped tanks. When I did get them apart and got the foam out (bits of foam everywhere), I could not get them water (fuel) tight. I'm not sure what I did wrong but they sure didn't work for me.....plus I was out $100 worth of materials.

I might try it again in the future....but only if I had to make a very specific shape and I had lots of time.

Hi Bob, what thickness of cloth did you use? In my tanks I used 5 layers of 90 g/m² kevlar sandwiched between 2 layers of 180 g/m² normal glass cloth. Both where very good foldable and followed the conformal shappes of my diy F-15 fuel tanks, no problem.

Regards,
Gerald

I did the lost foam. To get the foam out I simply mechanically dug it out with a screw driver then melted out the last little bit that remained after the screw driver with lacquer thinner. It was easy and worked very well. As I've never had to take apart a main tank, I simply epoxied in the appropriate brass tubing for fittings. Worked very well.

Bob,

Did you cut the Kevlar on a bias? (45* cuts to the weave) Cutting it on a bias makes it easier to wrap around corners and contours. Vacuum bagging would also help matters too.

JR Gautreaux

i never made one, but use a lot of fiberglass and kevlar!!

I have one Kevlar tank in my harpoon, and last time when dismanteling the model after the flight, i noticed jet-a1 coming out from the weels cut..

checking everything i found out the tank was leaking! [X(]

i putted the tank in water, some air pressure and i had 5 leaking point!!!![:@]
and all in point where there is no contact with the airframe at all!![:'(]
The tank was made in germany...

the tank as no more than a layer of kevlar...so if i will buy or made one alone...3-5 layer of kevlar and fiberglass!!