Hi,
Yesturday when I was landing my extra, and strong undercarrage
just collapsed! It wasn't even a hard landing,
when I got home, I realised all the insides was fuel soaked,
all the ply + balsa was fuel soaked.

But I cannot understand where the fuel is coming from,
so I have attached some pictures, and comments would be
appreciated

As you can see, the whole
powermodule is fuel soaked

Insides of the plane

The piece of wood that was there...

..fell off and lead to...

my geuss is the fuel tank. Take it out and test it for leaks using a water bath. If that isn't the problem i dont know what is.

..the UC failure

Volkan: If this is that VMAR plane you've been flying, then I understand. The undercarriage is very weak. I had a VMAR stik and had to replace the undercarriage two times with no leaks inside. I gave the plane to my dad and he re-sheeted the entire plane because it was built so weak. Now it's a strong little bird and still flies good.

The pictures help a little.

1. You can check your fuel tank in water bath. Plug all the openings but one and apply pressure to that one opening. If you see bubbles, you have found the leak.

2. If the tank checks out, replace ALL the fuel lines and make sure they have fuel line clamps on them. Looking at the photos, I don't think the leak is in the tank though.

3. According to the photos you have 2 pressure taps coming off the muffler. The area in back of the muffler appears heavily soaked. Check that the muffler is seated properly to the engine (gasket between the muffler and engine is not leaking) and that the lines from the pressure taps have fuel line clamps on them also.

4. To try and get rid of the soaked in fuel you can try the following:

If you have a product over there called "K2R" spot remover, apply that, let dry and brush off.

If you do not have K2R, use talcum powder or corn starch and sprinkle the soaked areas with that, rub it in and let dry. Then brush off.

Either product will take several applications to get the oil out. You will not be able to get all of the oil out, but you should be able to get out about 95% (or more) of it.

Once you have gotten as much oil out of the wood as possible, seal the wood with epoxy thinned about 10% by volume with acetone. This will take a couple of days to dry, but will prevent any more fuel from getting into the wood.

When reassembling/repairing the rest of the plane, I suggest using epoxy to repair it. Epoxy is heavier than CA, but it will adhere better to the cleaned wood than CA. You will need to rebalance the plane after the repairs.

For future reference, I suggest brushing on a thined epoxy mix to the firewall and fuel tank area when assembling the model. It will prevent these areas from getting fuel soaked if a leak should occur.

fuel looks like it is dripping down the fire wall. make sure when the lines go through the firewall that there is no brass tubing going near or through fuel lines as it passes through the firewall, vibrations of the engine running can cause the tubing to cut the lines. Also check that the stopper is in tight. details around the firewall are hard to make out since everything is so close. seal fuel compartment and engine compartment with fuel proofing so that if fuel does leak it does no damage. thin epoxy with alcohol and paint it over the interior after removing oil from wood using methods stated previously

Volkan,
Had the same leak on mine, could not find the leak untill for a couple of weeks. The tank had split at the bung. Just replaced the tank when I seen the leak. Found the leak on a test stand when running in another motor. Just ARF quality tanks.

Cheers.

I have very limited experience in the sport, but I did have a recently with a tank.
Could not find the leak, until I over pressured it. It had plit on the seem right on the bung, and was invisable to the naked eye. Even blocking the tubes on blowing into the tank did not reveal the sourse of the leak, I rigged up a bycicle pump and a bucket of water. The leak was tiny, but still a leak nevertheless.