I have had two clunks come loose after heavy landings. They seem to have simply slipped off the fuel line.
Has anyone got any advise as to ways of avoiding this problem - my fuel tanks are particularly inaccessable.
Also, should the clunk be able to come forwards, the fuel pipe I am using is quite thick and seems to prevent this.
(*I have asked the same question in the Fuels forum).

cut a small piece of the same fuel line you are using
for the clunk and slide it over and above the connection
of the fuel line and the clunk~

You should use the silicon fuel line that comes with the
tank not the thick one that you use between the tank
and carburator!
Regards
Hisham.

Nice idea, I'll give that a go.

Here's something you might try...
http://www.nsrca.org/technical/tip_tricks/clunk.htm

Check this out http://www.rcuniverse.com/showthread...175#post719955]

You can just wrap soft copper wire around the line where it goes over the clunk to hold it on. Several tank MFG's supply it with tanks now.

And the clunk should NOT be able to swing to the front of the tank. I always add a piece of brass tubing to the clunk line to prevent it in case of an abrupt stop.

i use zip ties on every single fuel line join.

-David C.

Minn, how does the engine stay alive during an extended dive or spin if the clunk can't get to the bottom- er, front- you know what I mean

- George

A short piece of a drink straw that just fits over the fuel tubing will also keep the clunk from moving forward in the tank.
Ed M.

Mulligan... I think I can answer this one


The answer is, if the downline is extended long enough, it doesn't
stay alive at all. It will eventually starve for fuel and quit, or at least stumble.
However...
the engine usually dies, long before that happens, along with the rest of the plane.
Props aren't nearly as efficient in dirt, and our poor little engines simply bog down and die.
It's pretty much an instantaneous event

The small nylon wire (zip) ties work great. The wire idea, if one is not careful, can cut through the silicone tubing in time and there goes the clunk.

To expand on C_Watson's answer, most folks cut the throttle back on a dive, so the engine doesn't need all that much fuel. Most dives are only a few seconds, so the fuel in the fuel line is plenty to keep the engine running. But, in theory, you could starve the plane for fuel if you were diving long enough.

The problem with letting the clunk come forward is that on most tank designs, once it gets forward, it won't move back. I don't think there's any particular reason not to design a tank so the clunk can come forward, they just don't.

Hmmm...

Imagine, with half of tank of fuel, being in a large cuban-8, on the down leg, 45 deg., or flying pattern on a long 45 deg. down leg at half-throttle.

Seems you need the clunk to travel "down" the tank to some degree, no???

I don't know what actually happens inside the tank, and I've never done anything to stiffen the in-tank line either. If you use the right hose (not normal fuel line) at the right length with a proper clunk, I don't think there should be an issue, though.

- George

Unless you get reeeeeeaaaaaal sloooooooow on the downleg much of the fuel is going to stay at the back of the tank anyway. One of the things I have found out in this hobby, if the cluck goes to the front of the tank, its not going back to the rear unless you force it after its landed/crashed from going deadstick.
Ed M.

I use zip ties too on every single line. Work great.

They make speciality clamps for tubing/hose that small just like regular hose clamps like on a radiator hose for example.

Sometimes you can find them at specialty electrical supply places.

I've never put one in a tank like that just pointing out another idea.

Also I've seen wire clamps that basically go around a tube and come up on each end to form a "V" you squeeze to put it on. Everyone has seen these tiny ones, but I've seen a few that have a flat spot on the other side to keep them from biting in.