mounting fuel tanks

I'm trying to think of a slick way to mount either a plastic bottle tank or a metal uniflow tank in my next airplane so it can be removed or adjusted easily. How are most people retaining these tanks so they will not move, yet are easy to remove or shim? In my SV22 the bottle tank is held in with rubber bands on little hooks, It is a major pain in the @#$@!#& to remove it at the field if you have to. I saw Ted Fanchers plans for the Trivial Pursuit in which he bolts the tank in through a sleeve that goes right through the center of the tank. That is a great idea. but a little scary since there is vibration involved, and I would not trust my solder joints at the sleeve location. If that works though it is a very neat way around the problem. Some metal tanks are simply slid into the tank area and shimmed, but how do you hold it in place?
Thanks for any advice!!!!

I have some closed cell black foam rubber that is semi rigid.
I use this to pack around the tank until I am sure of the height I need. Then I use balsa twigs or silicon to give a semi permanent installation.
The bolt through the tank works well when I remember to do it.
Bill <><

If anyone has photos of different tank installations, it may be helpful to a lot of people. I used velcro in my last ship, and it worked great until the fuel got to it!!

I'm like everybody else, it's my way or the highway. But "my way" is a bit weird...

Buy Pylon "Gold-N-Rod" in the 4-40 size. Buy a bunch of those threaded-one-end 12" rods in 4-40. Make sure you've got high-quality silicone fuel line, I prefer Prather's stuff.

At home, rip out the inner tube/rod of the Gold-N-Rod, as that is all you will be using. Experimenting on scraps, what you want to do is come up with a drilled hole which will just barely accept this tube, knowing up front you will have to (lightly) hammer it home.

More specifically, I use 1/2" balsa laminated with 1/64" ply top and botton, a piece of 1/4" plywood, as those are the two materials in which I will be installing short chunks of above mentioned tubing.

Visualize where you would like to have hooks for rubber bands holding the tank in place. I like two locations at front of tank, one in the bulkhead (1/4" ply) at rear of tank compartment. Think this installation through before drilling holes. For example, if the tank will be shimmed from the floor of compartment, better factor that in.

Drill holes.

Holding tubing at an angle, run a sharp knife over it, creating spirals along flutes of tubing. This tubing is not the best material in the world for gluing, so the tight holes and small notches cut in the flutes helps a lot.

Glue tubing into holes. Thin CA is fine, although in the tank compartment I always use epoxy. Trim tubing flush.

Using snipe- or round-nose pliers, practice bending cool loops in the ends of the threaded rods. When you're a pro, cut threaded end to length, cut unthreaded end ditto, form loop.

Screw what now look a bit like cup holders into the Gold-N-Rod tubing which has been installed in structure.

Secure tank in place with rubber bands. Except **don't use** rubber bands. Cut a loop of silicone fuel line, join ends together somehow. Maybe a knot will work, I don't know. I cut a 6-32 screw down to an all-thread length of 1", stick it equally into each end of the fuel line and wrap with (serving) wire. Nylon zip ties are functionally equivalent, just don't look zoot.

Test for fit. It won't (fit, that is), try again. Also note that a chunk of the Gold-N-Rod tubing will work well in place of the whacked-up 6-32 screw. And be lighter, should you care.

I will frequently tie a loop in each end of silicone retainer, sometimes it helps in tying the two lines together--like a pair of suspenders--about mid-point of tank.

In order to ensure tank stays put I will generally CA a fuel-proofed square of balsa to tank, running the silicone loop up and over it.

When done you've got a neat installation where the tank is easily removed for shimming. And that loop of silicone fuel line will out-last a full pound of #64 rubber bands. Plus heat from that tuned pipe laying across the tank won't bother the silicone retainer.

The very same trick, same materials, works great on a profile, by the way. Think about it.

The very same trick, same materials, works great in retaining hatches and removable bits, by the way. Think about it.

Also think about using the 2-56 size of Gold-N-Rod for light-duty use.

LAST EDITED ON Dec-10-03 AT 01:01 PM (CST)
 
>If anyone has photos of different tank installations, it may
>be helpful to a lot of people. I used velcro in my last
>ship, and it worked great until the fuel got to it!!

Velcro would be my first choice for full fuse ships. I normally use only balsa wedges and a fully boxed tank tection though.

LAST EDITED ON Dec-10-03 AT 01:00 PM (CST)
 
Oops!

LAST EDITED ON Dec-09-03 AT 02:45 PM (CST)
 
I don't like rubber bands. I solder a bracket to my metal fuel tank and use screws to attach it to the plywood doubler. Its easy to remove the screws to get the tank off or move it.

I have a friend that drills 2 rows of 1/4" holes 1/2" apart all the way through his fuselage and plywood doubler. He attaches the fuel tank with plastic wire ties. The wire ties go through a hole and back in another hole then around the fuel tank. You can cut the wire ties to remove the tank. Attach it again in one of the other holes to move it to a different place.

I tried the wire tie idea on one of my airplanes. I drilled only 4 fuselage holes for wire ties. I used a Tomato Paste can for a fuel tank. A can of tomato paste is 50 cents, not a bad price for a fuel tank and its very light weight too. The wire ties fit tight in the groves of the can.

Well guys I am not going to say mine is the best but here is what I do for profiles or full body ships. Use “J” bolts and rubber-bands. Yes that is correct, nothing fancy but they last for over 500 flights before they need to be replaced. Every time I use the brass brackets that are soldered to the tank they break loose at the most inopportune time, like at the flying field. A rubber-band can be replaced in no time even at the field. Place a thin pad of foam rubber under the tank to soak up any vibration. Don’t make the rubber-bands too tight but just tight enough to keep the tank from moving around.

Mikey,

There is no functional difference between our two methods. But mine is a *whole bunch* cooler.

I do agree on the soldered brackets and other crap: They can--and will eventually--break. Meantime, the primary purpose of this stuff, adjustability, is not needed once the tank is positioned properly. From that point on, it's just dead weight going along for the ride.

On a profile, there seems little value in trying to isolate tank from the shakes, assuming it is tied down to the point where it won't go flying off. So I prefer to install the tank with double-sided tape, then a loop of silicone, or in your case the inferior rubber bands.

The only caution is that this tape is quite sticky, and so one is advised to use small pieces at each corner of the tank until it is perfect. Then install with a pieces, or pieces, covering entire tank base, jam against fuselage, strap 'er down, good to go. Even if the bands break.

Still with profiles, my method leaves straight chunks of wire protruding from fuselage. When setting final position of tank, first get together a stack of shims which will just fit between tank and wire hooks. Pull out a 1/32" or 1/64" shim. Reinstall tank with shim stack as a gauge.

Has anyone ever considered using "O" rings instead of rubber bands?

I like wire ties, no gummy mess to deal with.

>Has anyone ever considered using "O" rings instead of rubber
>bands?

The good thing about this is that O'rings come in many materials, including our favourite, Silicone.

On profiles I use the brass brackets soldered to the tank. Guess I'm a better solderererer than Mikey. never had one break. I bury hardwood dowels under the plywood doublers to hold the screws. Then as anti-vibration I use sponge from old mouse pads.

Full fuselage tanks get mounted by stuffing into the cavity and held in place with scrap balsa sticks glued with GE Silicone. To remove, just cut it away. Only problem is you cant make an instant field repair using the same technique. But I have stuffed mouse pad foam in the cavity to hold it in place temporarilly.

Several 'round these parts have used the brass brackets from Brodak for profiles, glued with J B Weld....if cleaned they work well. I use Velcro as a "cushion / vibration easer" and a little bit of extra insurance.

For built up models with tin tanks, a "Big Jim" type nose construction seems to work well, and, if built with about 3/16" of latitude, allows spacing to achieve equal runs on 2-strokes.

See Ya

I tried Ted's method in my SV-40. Couple hundred flights and no problems. I did use 1/8 brass gommets top and bottom to provide some soldering surface, with a single piece of 1/8 tubing for the screw.

It is very clean and easy to adjust. And no leaks yet.

FYI