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Fuel tanks - the good bad and ugly


Scruffmeister
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Flying my HK Soar 40 the other day I noticed a lot of air bubbles in the fuel line. Although they didn't stop the motor running I was a bit bothered that something was wrong in the fuel system.

Back home I removed the tank and took the bung out. Half of the silencer vent pipe remained in the tank, the stub remaining in the bung.

There follows a couple of pictures of the pieces, clearly showig the corrosion of the brass pipe.

fuel tube_1.jpg

fuel tube_2.jpg

I haven't ascertained where the air bubbles are coming from, but suspect that the fuel feed pipe is similarly cracked.

Think I'll acquire some 1/8" aluminium pipe! And I'll check my other fuel tanks.

Cheers GDB

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Could some of the cracking be "Season Cracking"?

As we all know the cause is the residual stress from the drawing process and ammonia. I would imagine the source of the ammonia is modellers using executive urinals at the club field.smiley

Also having copper in the alloy such as in bronze is susceptible.

There is a solution which does not involve abandonment of the fields facilities and that is to anneal.surprise

 

Edited By Erfolg on 11/05/2015 19:55:52

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Du Bro get my vote. I've got a lot of Slec tanks, there ok but need checking for leaks on the mould line. I used to have a Flair Harvard and used the circular tank it came with. If you know the Flair kits, the front of the Fuz is built around a square tank bay. Yes you've guessed it, lots of deadsticks...the tank rotated. So in went a Slec tank.

The other thing related to tanks is the tubing. I always use clear thick wall tubing, as its easy to see bubbles and see fuel coming through for filling etc. Being thick wall its more resistent to niks.

We did have an issue a few years ago when at power the engine would'nt play ball. After lots of messing about we found a small defect on the inside of the tubing. When the engine demanded more fuel the increased fuel flow caused a flap on the inside of the tubing to open and virtually stop the fuel flow. Its only happened once in 25 years but just one to be aware of if you're having fuel problems.

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I used to have problems with screwing in the fuel feed adaptor into the tank (SLEC) .

I don't know why but I find it more successful to put the rear of the tank on the bench , drop the clunk end into the tank and then using either a suitable socket or box spanner to hold the metal nipple vertical rotate the tank onto the nipple thereby cutting the thread .

I can't work out why it should be any better but it seems to work for me .

Repairs can also be carried out by using a hot knife to seal a split or hole .

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