Installing clunk tank

[Russ]

I am building an Irvine Tutor 40, but no where in the instructions does it explain how to fit the tank into the fuselage. I expected the bung to fit tightly into the firewall once I tightened the screw in the bung, but this is not the case. Any suggestions?

[David Ashby - Moderator]

Russ, sometimes they do and sometimes they don't. As long as the tank feels secure then the bung doesn't have to fit in the hole in the firewall although if it does then fine.

[Andy Green]

Hi Russ

You would think the tank would fit through the hole wouldn't you, but in practice it rarely does.

The most important thing is to get the outlet from the tank at the same height as the carb, if you can achieve this and the hole lines up, it will be OK to enlarge the hole, but my guess is it will not.

I usually sit the tank on a shelf just behind F1 (the firewall) or a couple of supports and tack it in place with dabs of silicon (I use Fernox - from B&Q).

If you cant line the hole up, dont have the tank too far forward, in case you kink the fuel pipes.

A

[arthur bishop]

g'day Russ, yeah,this does annoy,but I open hole up a bit to get a snug fit then I feelconfident fuel line doesnt kink.

[John North]

I had the same issue. I used silicon seal to fill the gap ( and stop an fuel leaking into the palne. Also secured with foam foam and a rear 1/8" balsa strip with foam glued in place to prevent it moving back. Has withstood several short arrivals and a couple of mishaps without any issues. Another issue I had was that the engine mount firewall screws were too long as well and the nosewheel bracket screw so there was a concern that they might rub and or puncture the fuel tank. These were all shortened. Oh another point make the fuel lines just long enough to reach - with a filter in the feed line and a longet line to the exhaust - that way you should not confuse the two and try to feed the engine from the top of the tank - it only gives 30-40 second fuel - leran from my mistake. Good luck and enjoy it flies well and is a good plane for training.

[Dave M]

I had the same problem, ended up securing the tank with the foam sheet they supply (but do not mention in the instructions) this gave a snug fit. I then cut some quite thick poly sheet/foam to stop any chance of movement fwd / aft, (chocked it in place). It was given the ok when I got my instrucyor to check it and although I have only run the engine in so far, it seems to be a good fix. Maybe the first flight, which will be real soon weather permiting, will tell me if more secure fitting is required!

[bushwhackerbob]

Excellent plane for learning. Taught my teenage son on it. Especially like the semi symetrical wing.Fit a 46 when you start aerobatics
Ensure the tank is snug and does not move easily. I put a short length of tubing over the connections at the tank end to reduce the likelyhood of pipes coming adrift. I also use different coloured tubing to identify the purpose of each pipe.

Happy flying.

PS Keep a roll of sellotape handy as the covering is somewhat brittle and is easily punctured.

[Peter Eve]

Hi Russ - I'm a few months ahead of you with the same plane and agree with everything folks have said so far.  I've an extra experience to add. 

I was encouraged to fit an Evolution 46 engine and everything worked fine for a bit until I had the first inevitable (?) small prang which involved temporary removal of the engine.  I decided at that point to make the fuel lines easier to route and took the main feed under the engine mount, around the outside of the mount and in over the top.  Frome that point on life got steadily worse until I couldn't keep the engine running on full throttle.  To get to the point, which actually took weeks, this long line was starving the engine of fuel at high demands.  (Why it slowly got worse is still a mystery.)   I discovered this by chatting to an old hand in the local shop but he also said he had learned not to trust the plastic tubes which pass through the bung which are so popular on ARTF kits.

 Shortening my tubing has got me back in the air but I'm not happy with the way the engine runs and am still thinking of a complete tank change.  If I do, it won't fit through the hole but It will have brass tubes.

On a happier note, the plane flies well and I find as a beginner that about 80% throws are good for now and my "teacher" has had it in all sorts of manoeuvres, including inverted flight, with these throws.

 Good luck, hope you avoid the minor prang syndrome!

Pete 

[bushwhackerbob]

Make sure you do not have any air leaks in the pipe lines.  This can be done by blocking off the pipes into the tank and immersing the tank in hot water. Look for air bubbles to discover leaks. Check the height of the carb inlet and compare with the height of the tank. The carb inlet should be at about the height of the feed pipe from the tank or slightly higher. Check for air bubbles in the carb feed line with engine running. Inconsistent runs can also often be caused by air leaks in the carb. make sure the slow running screw is correctly set up. Is the needle clean?

 These are some of the causes you may need to eliminate

Happy flying

Colin

[Peter Eve]

Just pranged the plane - no more engine probs for a bit!  I had done all those checks and there were no bubbles.  I think it's also a setting up issue with the Evo engine having a slow needle and the normal one - and it's supposed to be a beginner's engine!

 Off to the shop!

 Pete

[David Martin 2]

Hi Russ,

Any tanks I've had with necks that could go through the firewall, I've made the hole 2mm larger than the neck all round, then stuck some of the 1/4" wing seat foam tape you can get from model shops round the neck before carefully wiggling it through the hole into postion. This makes a snug, protected fit for the neck. The tank usually gets supported from preshaped firm polystyrene above and below in the tank bay. Seems to work for me.

If you're using a SLEC square tank, be careful when you start doing loops etc that the clunk can't loop back on itself and get trapped in a top corner...!

Good luck.

[John Gallard]

An argument, sorry a debate took place at the flying field today regarding the operation of the clunk tube. Two 'mature members' insisted that the clunk should have sufficient weight to move to all sides of the tank irrespective of its orientation but should NOT be able to turn in its own length i.e face forward. Two other members (who mainly fly helis) disagreed saying it was essential that the clunk tube  could position itself at any position according to the direction of gravity and demonstrated such by viewing through their transparent tank and indeed the clunk fell to every surface of the tank depending on its orientation. Is this the norm for only helis or should fixed wing do the same?? The heli guys emphasised their case by asking if the plane was in a steep dive with a partially full tank how would a fixed wing draw its fuel if the clunk was pointing upwards out of the fuel, they claimed that a pressurised tank would not overcome the problem.  The 'mature' members claimed that in such a dive the fuel would NOT be at the front (bottom) of the tank but forced back to the rear by centrifugal force where the clunk would still be surrounded by fuel. Who is right?

[Tim Mackey]

This is going to be good

When I had IC stuff ( now down to just one model ) I always inserted a small piece of stiff tubing inside the clunk line to stop it "folding over", which has been the cause of many a dead stick and trouble to people over the years.

I would therefore say the two "mature members" were correct... on fixed wing anyway.

[ken anderson.]

as a mature member who fly's fixed wing-i would have to agree with my fellow brother's reguarding the fuel forced back in the tank-if they (were)incorrect-how come we dont see more 'dead stick' calls at the flying/club site's?........... ..

 

 ken anderson(can anybody explain why we call 'dead stick')?......i've taken a few dead stick's home in a bin liner before.....