Author Topic: Nice crunch thanks to a clunk tank (Read 1347 times)

John Crocker · « **on:** August 18, 2007, 05:43:59 PM »

Well, flew with a buddy yesterday, trying out the new twin boom (only pic I have. Wings were red cote, booms, elevator and mount were black:

got a grand total of 2 flights

Holy cow that sucker was fast. The .061 wasp turned 3 sec laps on 35 foot lines, bout 50 mph (6X2 APC props ROCK!). Well, I only 1/4 filled the tank and forgot and the engine cut out in a loop, kinda came down hard, but everything looked okay, so I filled her up a full 1 oz, cranked her up and let her rip on a light 2 stroke break.

Turned 2 laps to build up venturi speed, did a slow climb, into a dive for a tight loop (love 'em). Soon as I gave it up a stiff up elevator, it stood on its tail, engine cut off and it nosed over, CRUNCH, ripped the motor mount off, splintered the main interior fuse, turned 5 ribs to toothpicks and tore off several square inches of mono.

I was like what the H? Never had one do that to me before. I mean no sputter, no slow down, just screaming banshee to silence at the twitch of my wrist. So I tore down the engine, could'nt find anything wrong there, then checked the fuel lines, all good. Well the plane was toast so why not rip out the clunk tank?

Soon as I did, I saw it. Clunk line had come off the brass tube inside the tank. This caused the tube to be able to pick up fuel in level flight or light climbs , but as soon as I stood it on its tail, it was sucking air

.
I've now fixed all my tanks with the clear nylon hoses on the gas line instead of the brass tube. They allow you to put the tube further into the take up hose to prevent slips.

That was a killer plane too. I could probably fix it, but in the time it would take to strip it down, cut all the parts out again, rebuild, recover and repaint, I could do a whole nother plane. Going to try a larger built up wing version of this:

Thinking about 30" span round 200 square, round a 12" fuse and a hidden wing tank.

Looks like the wall of shame has another trophy.

ray copeland · « **Reply #1 on:** August 18, 2007, 08:02:10 PM »

Hey John , thanks for the info on the clunk tank hook ups.! Right now i am working on finding holders for 9 oz. balloons, they hold 3/4 oz. of fuel nicely, been using empty film cannisters but they are a little crowded. Am messing with some other holders ,maybe prescription bottles. Is that a 6x3 prop on that norvel? That is a beautiful flat winged plane in the pic, what is it? We fly mostly flat wingers in the backyard and are always looking for new designs to try. Thanks, Ray

John Crocker · « **Reply #2 on:** August 18, 2007, 11:37:17 PM »

Thanks Ray. Prescrip bottles work well for balloons, got a few stashed away for old Cox engines I have laying around. My Norvel and AP Wasp prefer pressure so I use the clunks on them. That prop is a Master Airscrew 6X3, but I've found APC props to run on those engines better. Maybe they are lighter, not sure.

As for the plane, that was the Phoenix, a design of my own that is pretty indestructable unless you hit hard ground The wreckage pic was after it had been repaired about 10 times from training my 7 year old to fly. I was flying it in the culdesac in front of my house and lost tension on the lines because of too much wind. As you can see, the plane was busted into a bunch of pieces, but could have been repaired easily if my son had wanted me to. He decided it was time to move into built wings so, we hung it on the wall in the barn for giggles.

Started building that design 20 years ago when all I had were Cox Bee engines. Found that it was lighter than the models I could buy other than built wings and could be built from scrap I had laying around. Its not real pretty, but is servicable and flys surprisingly well.

That one had a 24" wingspan and 10" body, bout as big as I felt comfortable with at the time. The heavy motor mount will allow you to pretty much tent peg a plane and keep on flying. Its a great tainer plane for learning tricks cause you only have about $10 in it including the paint and glue and your not afraid to crash it.

Body is half inch basswood square (I use 2 1/4" pieces and glue them together). Wings are 1/8" balsa.

Tom Perry · « **Reply #3 on:** August 19, 2007, 01:15:29 AM »

Quote from: John Crocker on August 18, 2007, 05:43:59 PM

Well, flew with a buddy yesterday, trying out the new twin boom (only pic I have. Wings were red cote, booms, elevator and mount were black:

got a grand total of 2 flights

Holy cow that sucker was fast. The .061 wasp turned 3 sec laps on 35 foot lines, bout 50 mph (6X2 APC props ROCK!). Well, I only 1/4 filled the tank and forgot and the engine cut out in a loop, kinda came down hard, but everything looked okay, so I filled her up a full 1 oz, cranked her up and let her rip on a light 2 stroke break.

Turned 2 laps to build up venturi speed, did a slow climb, into a dive for a tight loop (love 'em). Soon as I gave it up a stiff up elevator, it stood on its tail, engine cut off and it nosed over, CRUNCH, ripped the motor mount off, splintered the main interior fuse, turned 5 ribs to toothpicks and tore off several square inches of mono.

I was like what the H? Never had one do that to me before. I mean no sputter, no slow down, just screaming banshee to silence at the twitch of my wrist. So I tore down the engine, could'nt find anything wrong there, then checked the fuel lines, all good. Well the plane was toast so why not rip out the clunk tank?

Soon as I did, I saw it. Clunk line had come off the brass tube inside the tank. This caused the tube to be able to pick up fuel in level flight or light climbs , but as soon as I stood it on its tail, it was sucking air .
I've now fixed all my tanks with the clear nylon hoses on the gas line instead of the brass tube. They allow you to put the tube further into the take up hose to prevent slips.

That was a killer plane too. I could probably fix it, but in the time it would take to strip it down, cut all the parts out again, rebuild, recover and repaint, I could do a whole nother plane. Going to try a larger built up wing version of this:

Thinking about 30" span round 200 square, round a 12" fuse and a hidden wing tank.

Looks like the wall of shame has another trophy.

Tried to brighten up the dark picture for you.

Ralph Wenzel (d) · « **Reply #4 on:** August 19, 2007, 01:42:55 AM »

Too late to do that plane much good, but there is a fix. Before closing up the tank, wrap one turn of 20-gage copper wire around the clumk line and solder it. File the ends smooth. The tubing will not come off.

John Crocker · « **Reply #5 on:** August 19, 2007, 06:24:13 AM »

Quote

Too late to do that plane much good, but there is a fix. Before closing up the tank, wrap one turn of 20-gage copper wire around the clumk line and solder it. File the ends smooth. The tubing will not come off.

Believe it or not, there was a wire around the hose, must not have been tight enough.

minnesotamodeler · « **Reply #6 on:** August 20, 2007, 05:02:35 AM »

Quote from: John Crocker on August 19, 2007, 06:24:13 AM

Believe it or not, there was a wire around the hose, must not have been tight enough.

I think what Ralph has in mind is a wire soldered around the bare brass tube to form a ridge or "barb" over which the fuel line slides. Although copper wire wrapped and twisted over the fuel line probably isn't a bad idea either.

Clunk tanks don't lend themselves well to permanent installations. You need to be able to take them out and inspect the tubing, etc., once in awhile. Most any fuel line material will soften after enough time immersed in fuel.

--Ray

Author Topic: Nice crunch thanks to a clunk tank (Read 1347 times)

John Crocker

Nice crunch thanks to a clunk tank

ray copeland

Re: Nice crunch thanks to a clunk tank

John Crocker

Re: Nice crunch thanks to a clunk tank

Tom Perry

Re: Nice crunch thanks to a clunk tank

Ralph Wenzel (d)

Re: Nice crunch thanks to a clunk tank

John Crocker

Re: Nice crunch thanks to a clunk tank

minnesotamodeler

Re: Nice crunch thanks to a clunk tank