Attaching Fuel Tanks to a Profile Fuselage

I'm mainly a rubber band guy, preferring the long J-bolts which have nuts inboard/outboard of the fuse but my supply of these is dwindling and I've not had much luck in finding them stocked at the LHS. The threaded section would have to be 1".

I also have the Brodak tabs which you solder onto the tanks. Some fuselages don't have enough room for top/bottom or front/rear tabs. All the short nosed profiles (Ringmasters, FliteStreaks) present this problem.

For smaller models I've used the music wire with ends bent into hooks for the rubber bands or brass straps. I've found wood screws don't last too long in the fuel soaked area.

Leonard Neumann

Leonard;

All this is clear except for the two fasteners used to hold the mount to the fuse. The way I picture it, the tank is actually being pushed against the heads of the two fasteners and not the plywood. Is this right? If so, and problems with that?

Also, what size MW are you using for the tank retainer - 1/32"?

Works OK on combat type models but not so well on tall (Ringmaster type) fuselages. I'm using them on my Ukey 15.

The foam rubber helps reduce any vibration effects on the fuel tank, while keeping the bolt heads from digging through the back side of the tank!
>
>Also, what size MW are you using for the tank retainer
>- 1/32"?
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I use scrap left over from other stuff; there are always odd lengths of wire in the junk metal collection boxes!

K.

This makes sense. I could only think of one other way - and that was a combination countersink and putting a scrap balsa sheet with the screw holes drilled out between the ply plate and the tank.

I've never used this method, although I have used everything from soldered on tabs to a crate packing strap (don't laugh - it worked great). But, its always fun to file away just one more way to skin the proverbial cat... .

Regards - Bob Kruger

>>
>>Also, what size MW are you using for the tank retainer
>>- 1/32"?
>>
>I use scrap left over from
>other stuff; there are always
>odd lengths of wire in
>the junk metal collection boxes!
>
>
>
>K.
>
>*

Leonard Neumann

All the above approaches obviously work, and work well. I like the Brodak tabs that Scott Recommends, more because I would rather solder than glue. They will fit the short-nose planes if you solder them to the top and bottom of the tank, and perhaps add a small slab of plywood to the fuse to get the full range of vertical adjustment built into the tabs. Full vertical adjustment, and a finger twist can get the back part of the tank higher / lower than the front half. Easy adjustment. And when you land inverted, a few twists usually brings you back to your original setup with not much fiddling.

See Ya

Lately I've built my own tanks, and I leave a small tab top and bottom to drill a hole through and I screw it into the engine bearers (as they go back to the wing L/E) Works great, but the tabs just broke of on mine after the Xth crash

My next idea is similar to Leonard's. I don't trust J bolts to stay screwed into balsa so I'll try what I used for the pushrod anti-deflector thingy (which worked great for me).

Make a U shape out of music wire, and push it through the balsa from the inside, so that you have a vertical bit of wire against the inside of fuse. Then bend the free outside ends into a J and voila! (I hope) This is the same as Len's but I leave the wire visable rather than hidden beneath a ply mount, so it's not as neat, but I don't worry about that sort of thing yet!

It worked in the 50's and you know what...it still works today.

I try to get the J bolts which go all the way through so you can secure with a nut on either side of the fuse. If you don't like excess hardware (or have an inboard balsa tripler) you can use the 4-40 threaded brass inserts which won't pull out.

I don't bother with the J bolt nuts on the IB side. Just drill the J bolt holes a little undersized, and screw them in.
Remember: they're being screwed into ply, not balsa. I've never had one pull out.

And if one did pull out, that means that the tension on the rubber band(s) holding the tank in place is way too much.

I generally mount mine with one J bolt top center and two lower fore and aft. The rubber band forms an inverted V. If the top one pulls out I lose the tank. I had a rubber band let go once (they do deteriorate over time). The tank was still connected to the engine via the fuel tubing. It swung forward into the prop - doing damage to both.

As my pad, I've used those neoprene backing pads from those adjustable yellow ADC sanding blocks cut into lengths which correspond to the length of the tank. One usually lasts a season.

Steve: I do mine with two hooks up, two hooks down. Then I usually cross the two bands. If one gives up the ghost, I'm still in business. If I'm feeling really conservative, I'll throw a third band on there, straight up and down, maybe between the back two.

Want a surefire method to make your bands break on schedule? Hang the profile with rubber banded tank from the ceiling, directly above your one model in the entourage that has a paint job that you really admire. Oh, and make certain that the tank is directly over the wing, preferably half way between any two ribs (IB or OB, doesn't matter). Please don't put any solid balsa parts directly beneath, like the fuse or the tailfeathers.

Oh yeah. It will fall. Dead of night, probably. Tear right through the silkspan. Like a trampoline that has gone horribly wrong.

True story. And the offending tank was a dinky one ouncer off (literally) a Jr. Ringmaster.

And the offended plane underneath was a Magician with a creamy, admittedly bilious green. But it was smooth. I patched it in a contrasting green, bordered by black pinstipes. Funky.

Ahh... that's where you're wrong. Maybe I should use ply doublers, but my last model held up pretty well with just a 1/2" balsa fuse and 1/2" maple engine bearers epoxied in all the way back to the L/E.

Should I be using ply doublers? (he says, flinching against the onslaught)

Unlike Rusty, I've never owned as many fuel tanks as I've had planes and in spite of using the wire tie attachment system, was losing as many or more smashed-up Slow Combat tanks as airframes that were unrepairable. The wire ties don't "protect" hard tanks from hard knocks any better than the rubber band system, but definitely raise the dependability of a lousy fuel system out of the sub-basement (the hard tanks required by the Slow Combat rules are among the worst aspects of those rules).

For my sport planes, I still use the rubber band mounts because I swap tanks from one to another. I've seldom left a profile plane's tank attached to that model any great length of time. As part of cleaning them up after a flying session, I typically pull the tanks off, and toss the dirty rubber bands in a sandwich bag with corn starch to absorb the castor.

( Incidentally, the profile Slow Combat models never had those tank pockets that some of my sport planes have, so if the latter type do undergo a sudden stop, the tanks don't have to wind up with neatly punched holes in the forward sides from the backplate bolt heads. )

I often don't re-mount the rubber-banded tanks until the day before the next flying session. With wire ties, they are not "really" that much more expensive than good rubber bands, and not difficult to cut away, but there's this residual sense of "WASTE" about it that makes doing so feel "wrong." It doesn't bother my son Jeff, but I do remember an occasional night of attempted sleep that wouldn't come because I hadn't eaten supper - there'd been none. That's probably why I can't comfortably snip off the ties in the same casual way that I can pull off rubber bands and discard them if they still seem too gummy after trying to clean them up some.

K.

After the glue has dried completely, sand flush with the doubler surface, and then drill a starter hole in the center of each dowel. Screw in a stainless steel L-screw, available from any hardware or Home store, and mount your tank, using the "quickie method" of rubber bands, or soft wire. These L-hooks will be there long after you have bagged up the plane, and the tank will have no room to shift. If you switch to a narrower tank, just use pieces of balsa (soaked with Instant CA) as spacers to take up any available space. Works for me.
Chuck Potts, in Mobile, AL

Not sure I've seen an "L" screw (and I've spent lots of time browsing the fastener bins at the local hardware store) but I have glanced at those cup hooks which we should all be familiar with. They come in different sizes. I suspect the smallest would suffice.