Inside loop cuts engine off
 

Greetings,
I'm new to this sport. After flying 1/2A's, I built a Galaxy and Twister, then attended the Brodak Fly-inn 2003. The Twister flew great but it's in repair, I didn't check the fuel filter and the engine cut out on a wing-over. I'm flying the Galaxy with a newer Fox 35, about a quart through it now. My problem is when I do an inside loop the engine cut out on the bottom of the loop and I'm forced to land. I've sheared 4 needle valves. They is a 3 oz. uniflow stunt tank on it, the engine does not have the muffler on it. When I start the engine an hold plane and go through an outside loop the engine keeps going and when I simulate an insde loop the engine cuts out. Iv'e riched the needle valve out but it still cuts out, I've leaned it out too. Nothing seems to help. I did have the muffle on it before I stared to do loop but I took it off because the weight of the muffle and lead really shortened the glide. Is the tank bad or the engine still too new? The tank has three vents, one overflow straight down, one straight forward just over and behind the top of the engine cylinder and the fuel line comes out on an angle. The fuel just cuts off when the plane heads down.


Thanks

RE: Inside loop cuts engine off
 

Only a quart through the motor? You're not broken in yet. But if the plane is light enough, you can fly it in by putting a smaller prop on the plane and running it rich. Try a 9x6 prop on your motor. When your motor is fully broken in, you should be able to set it to a 2 stroke and let it run there without it slowing down from overheating. More than likely you're flying load is just a wee bit on the warm side and pointing the nose up just pushes it over that edge.

Try a smaller prop and let us know.

RE: Inside loop cuts engine off
 

I get the idea you are possibly reversed on your loop terminology. If you are flying along level and take the airplane up and around in a loop that is an inside loop. Sounds like you are loosing the engine on outside loops, if the needle is on the top.

I do think your engine needs a bit more running time, and that may well solve your problem. Another possibility is tank position vertically. A lot of people have much better results with the tank set about 1/4 - 3/8 inch high. I've never found this necessary, but many others get good results out of high-mounted tanks.

Be sure you cap off the overflow vent before you start the engine. (I use a BB in a short piece fo fuel line. Don/t use a bolt, as it will leak air.) Otherwise the the tank is not a working uniflow and you can expect a poor run.

Hope this helps.
Jim

RE: Inside loop cuts engine off
 

galaxyob1,
Newer Foxes don't need as much break-in as the older ones did, but they DO need some break-in. You can check whether it is broken in by running it at flying RPM. This is best done on a bench but can be done in the plane. Start it and lean it out but not to peak. If it runs a whole tank without slowing down it is broken-in. If it starts to slow down shut it down by pinching the fuel line or pointing the plane straight down. Let it cool completely and start it again. Run it for a series of two minute runs followed by a complete (5-minutes) cool down. Do about 10 of these. When the engine will run a whole tank without slowing down, it is broken-in enough for the air.
This way you can be reasonably sure the problem is not the engine and start concentrating on tank and tank mounting problems.

George

RE: Inside loop cuts engine off
 

OK thanks to all and yes Jim it is an outside loop. I had my terminology turned around. I'll work on the engine some more before I work with the tank.

Paul

RE: Inside loop cuts engine off
 

Greetings,

For those who read about my problem with the Fox 35 on the Galaxy here is an update. After several attempts to get the OS loop and engine to work I ended up rotating the Fox 35 vertical last summer. This was done after a few needle valves and fuselage repair. The plane and engine work pretty good now and its fun.

Since then I have also worked with the LA 25 on a ARF flite streak and I built a Brodak Tomhawk. The LA25 work good, but I put a smaller venture on it to slow it down, it works for me. Here's a question on trimming the Tomahawk, the fuselage moved on me when it was glued and I caught it too late. The fuselage is about 5° to the left, to compensate I made sure the elevator flaps were parallel to the wings, so a few things are square. The Tomahawk flies with the o/s wing listing up, I see more than the profile. Can and should this be straitened out? I've seen an OTS stunt Eldiablo at Columbus with some added o/s wing flap. It this what needs to be done?

RE: Inside loop cuts engine off
 

A classic problem with a sideways mounted Fox 35 (like on a profile) is the cut-out when going inverted. Turns out, the tank really needs to be higher than the thrust line, by about 5/16". This means that inverted, the tank will be slightly lower and the famous Fox "burp" should disappear. Or, you could try a clunk tank - it is far less critical.

Sounds like you got the engine straight up and down, which will solve the whole problem.

For an outside wing listing up, you need to check a few things. Is the wing up when inverted, too? If so, then it's too little tip weight - add some. If the wing is down in inverted flight, then there's either a warp, or the flaps are not straight. Warps are easy if it's monokote - just flex the wing in the opposite direction, and iron out the wrinkles. A fabric covered wing will sometimes respond to steaming over a pot of boiling water. Flaps can be fixed by bending the flap horn, but try to clamp something on the flaps to spread the load if you try to twist them - otherwise, you can break the flaps off. If all that fails, you can still try a trim tab. Epoxy a short strip of sheet aluminum on the outside trailing edge. You can bend it and it will retain its shape.

Good luck.

RE: Inside loop cuts engine off
 

I have been having the exact some problem with one of my Galaxys in OS loops - what is strange is that I have two identical models both with Fox 35s and one cuts everytime and the other is fine. I have landed inverted many times and quickly discovered that to prevent snapping the N/V I swopped it around so that the needle adjustment is now pointing down when the model is upright and protected by the silencer. A bit fiddly to adjust but I have found that in most instances it doesn't need touching anyway. On the one that keeps cutting I have moved the tank up 5/16th inch as suggested above - but have not had a chance to see if this will cure the problem. Both 35s have had many years use (10 plus) so its not a breakin issue in this instance.

Cheers

Kevin

RE: Inside loop cuts engine off
 

I have had the same problem using a wedge tank, and a chicken hopper. I tried moving the tanks up and down, with not much luck for a suitable flight. Finally,, I put one of the UGLY cluck tanks on, and walaaa, all my problems went away with the next flight. Some of my planes work with the wedge, some don't.
Lee TGD

RE: Inside loop cuts engine off
 

Thanks for your input. The Fox engine is a challenge to master. I have a clunker on my banshee and the fox has not failed me yet, neither has the vertical mounted fox.


As for the Tomahawk, the wing does not look warped and the flaps look straight to me and the wing does lists down when inverted. I'll have to look closer and try something.

Thanks again,

Paul