Planehutch888

My Feedback: (2)

So Ive kinda learned how to fly CL, I can go round and round, upside down, inside and outside loops and figure 8s. They are not precision but ok. Ive been flying about a year on CL ,30 years in RC. I have a 500 Sq In homeade plane with an OS 40 FP on 60 foot lines. The problem is Im flying upside down and the motor dies on the upwind part of the circle, the lines go slack I try to backup while pulling out to land but can't fast enough so the plane crashes. Im getting tired of rebuilding. What is the fix? I only have this problem when Im high and there is an 8 to 10 mph wind, Im in Kansas so it seems there is always at least a 8 to 10mph wind. Maybe electric, as you will get some warning the battery is going bye bye, but I like the 2 stroke noise and old timey part of control line. As much as I enjoy CL this crashing for no apparent reason other than bad luck is getting old.

Jim Thomerson

Been there, done that. At your stage of flying, I don't think you should be high on the upwind side of the circle. Maybe work on being able to fly inverted at shoulder height. If your engine quits because out of fuel, you shuldn't be upside down. I'd suggest timing your engine run and spending the last 30 seconds or so flying around level and right side up anticipating landing.

jayseas

Don't want to steal your thread but I'm having somewhat of the same problem,My fox 35 wants to die alot of the time when getting to the top of the loop or inverted.Need some possibles?I have been trying to richen it up and have played around with to different tanks and i can't seem to cure this, i hate crashing when its something like this.This is on a scratch built 400 sq in wing, home made uniflow tank.

gcb

Jayseas, yours sounds like a completely different problem. Ttell us more about the plane and how the engine is mounted.

George

jayseas

George, here is a couple of pictures.The pickup tube inside the tank is centered in the aft outbd corner.The uniflow tube ends about a 1/4" away from the pickup tube.

Planehutch888

My Feedback: (2)

I have also faced Jayseas problem. First the Fox engine is a vibrator usually, so insulate that tank againnst vibration by mounting it in foam, not solidly on the model. Also the Fox is very sensitive to fuel tank position. The tank I see is not exactly centered on the carb center. Actually lowering the tank I see by 3/8 of an inch or so might help solve your problem because you would get more even flow upright and inverted.Id say just play around with different tanks, mountings, pickup positions until you get something which works. Also profile models are more prone to vibration problems, the thin fuselage is not as rigid as a box fuse.

jayseas

Hopeing to be able to fly in the morning, so i can experiment with more tank positions.and will answer back if i find the spot or not.
thanks guy's.
jim

JohnBuckner

My Feedback: (1)

If I read you correctly are you saying you have engine run problems when inverted also? While I do agree with Jim in his suggestions I am going to offer an alternative to running problems that is a bit out of the ordinary at least for controlline and flys somewhat in the face of conventional wisdom concerning fuel systems, tanks, uniflow and so forth.

Since you are using a 40 FP I am assuming you are using a muffler with pressure avaliable I think you will find by the simple expediant of useing a bubbless tank from either Jett or Tetra all your uneccessary inverted landings will vanish.

Unlike the somewhat difficult setup to obtain for uniflow and certainly none of the shop time neccessary a bubbless tank on muffler pressure can offer superior fuel delivery characteristics. Even though the tank looks conventional it has no clunk the fuel feeds from the middle of the tank. The tank can deliver from as far aft as the CG if you want. There is no critical height problem and no orientation issues the tank can even be mounted vertically if you wanted And there is no vibration issues at all. It is sop to hard mount them (no foam).

I have an old 40 FP on my Magician that works magnificently with a Tetra four ounce.

I do suggest you fuel them from a large syringe however and not a fuel pump to gain the most benefit however as this assures there is no air in the internal bladder.

John

gcb

Additional thought: The tank appears to be actually touching the engine. If heat is transferring to the tank, along with vibration, might the fuel be thinning out before it gets to the engine, causing a lean run...which coupled with the engine going lean as it gets near the top, causes cut-out?

Also, check where the spraybar hole (s) is/are. If it's the two hole type, make sure the holes are pointing down (can't see either one). If it's the one hole type, hole to the rear, just out of sight.

Good luck.

George

gcb

Did Jim fix your problem? Is it a running problem or just what to do when the fuel runs out?

George

jayseas

George,
Yes i have several problems and i can't beleive i did that. putting the tank against the engine.And the hole in the spray bar is pointing directly down the throat of the venturi, which i see is a no no.Will correct these problems before another attempt.I totally destroyed my Akromaster, doing a figure eight got to the top of the inside loop engine quit, 'my darn fault new i was getting low on fuel and just had to push it' it blew in and up total loss of control and it nose in hard three pieces.The wing is the only part i can reuse.My dumb fault.

Lou Crane

Jayseas,

Don't let that discourage you...

The Fox 35 has been around a lo-o-o-ng time. It isn't perfect (understatement?) but it can still do a good job.

A uniflow tank, running properly, can be dead solid down to the bubbles at the end of the flight. Slightly off, and particularly with a Fox 35, it can cause a very noticeable difference in the run between upright and inverted, insides and outsides...

General rule that works pretty well: the end of the uniflo tube inside the tank should be about 1/4" above the center of the intake. It may take a bit of tweaking on a particular model, and with a particular example of the Fox. (Some of them differ.) I notice, I think, that the tank is/was bolted to the fuselage in a way that you couldn't adjust its height up or down. Suggest that next time you build in a way to let you do that...

HOW you run a Fox 35 can make a difference, too. It is famous for the '4-cycle/2-cycle break' type of run. That can be done. If the engine was too lean, going gangbusters in 2-cycle all the way, it may have leaned out high on the flight circle, or reacted too much to a slight misalignment of the tank height. The Fox also has a nasty habit if it is run too rich... Nice grunbling 4-cycle, but when you loop it, it can break too much into 2-cycle and cut out.

An ideal launch needle setting, if everything about tank height is close or right on, is warbling between 2-cycle and 4-cycle, mostly in 2-cycle with fairly frequent 4-cycle burps. When everything is right, the model settles to a strong 4-cycle within the first level lap, and breaks into 2-cycle when you maneuver. (It should also break back to 4-cycle after a maneuver is finished.)

If you have fuel with at least 25% castor, and from 5% to 10% nitro, a good hot plug and a prop that is neither too much or too little load (say a TF Power Point 10-5 or 10-6), you should be able to dial-in tank height so it will fly well and consistently.

Edit to add: That 1/4" starting point is for profiles. For upright or inverted engine, full-body models, a 1 inch high tank sitting on the mounts (uniflow vent end inside at 1/2" above the mounts) works very well.

Besta luk towards that!

jayseas

Thanks Lou, for your imput.I have built another tank to get it away from the engine and also so i can adjust it, it is mounted with velcro so i can move it up or down to find the spot it likes.I will try your needle setting, and see how she does.You mention a 10-5 or 10-6, isn't that way to big a prop for the Fox .35?
here's a picture.

build light

Here is a handy dandy prop chart to help choose props for different engine sizes. Thanks to the folks at Top Flite:
http://www.top-flite.com/accys/topq5000a.html

Personally I have never run a two blade prop on a .35 less than 10" dia.

Robert

Jim Thomerson

I'm presently flying a Fox 35 with a Taipan 11 x 5. The APC 10.5 x 4.5 is said to be the prop, but I like my Taipan better.

build light

That's great Jim. This goes to show just how difficult it is to reccommend the "right" size prop for people to use. What works best for your plane/engine/fuel/altitude/humidity etc. There are so many variables including brands and the material the prop is made from.

The best way for anyone to learn what they like best for them is to try a bunch of props and fly them to see which they like best. Even then, when they find what they like best, when they change fuel, move to a different place or install the engine in another plane you basically have to start over again.

Robert