onrecess

My Feedback: (2)

I am running an OS 61 SF Max on a TT Fun Tiger Extra. I am currently running a 11x7.5 prop. I am having trouble tuning it, and some have suggested this isn't enough prop. Is it? Suggestions on a good size power prop?
Thanks, Tom

bob_nj

My Feedback: (62)

What kind of tuning problems are you having? Whether or not the prop is right for your application depends on a few factors. What kind of flying are you doing with the plane?

onrecess

My Feedback: (2)

I am just foolin around with slow flight, high alpha, attempts to hover, spins, tumbles, ... you know, fun fly plane playing around. I cannot seem to get a smoke trail, even when it seems too rich. I have had lots of dead sticks. If I drop to idle too long it wants to die. It was too lean and dying, so I richened it, but never got a smoke trail even when I went too rich. I am (obviously) not very good with these engines, but a guy who can REALLY fly a giant fun fly tried helping. He said maybe the pitts muffler was too restrictive or the prop may not be enough.
Thanks, (again)
Tom

da king

My Feedback: (5)

Well first your way off on the prop. Try a 13x4. The 2nd number on the prop is....basiclly.....how many inches the prop travels in one revolushtion. Thats a high speed prop. You want low pitch props. 4 or 5. the 61 has a lot of tork. It can swing a prop any where between 12 and 14 dia. Fun flys fly slow and need lots of vert. big dia and small pitch. start with the 13x4 and go from there. good luck

onrecess

My Feedback: (2)

Great, I'll try a 13/4 next flight.
Thanks
Tom

Kevins_RC

My Feedback: (1)

I agree that you are running the wrong prop for this aircraft, though it sounds like you have an engine set-up issue. It sounds like you "bottom end" is too lean. Remember that this "bottom end" adjustment is really positioning of the asperator bar, which effects the fuel / air distribution into the casing, then to the cylinder. Try this - at an idle, pinch the fuel line to the carb. If the engine dies, then back out (CCW) the low end adjustment (small screw located inside the throttle arm). This adjustment is sensitive, so only make 1/8 turns at a time. If the idle rises when you pinch the line, then turn it in 1/8th of a turn (I doubt that this will be the case). What you are looking for is, at an idle, pinch the line, the idle rpm should be constant for about 5-7 sec. then of course drop off. Then adjust your high end adjustment so that at full throttle you get approx. 300 - 500 RPMs on a pinch. You'll get your smoke trail with this set-up and the engine shouldn't die. By the way, for what you want to do with this plane, you've got the wrong engine altogether. Go to a good BB 40 to 50. The OS 61 SF is a great engine, just too heavy for a 40-size Fun-Fly (IMO).
Kevin

Hercmate

I think that kevin4hsrcm is spot on. I had an OS 61 SF in a 58" CAP swinging a 12x7 prop and it was perfect for the job. But for your plane I'd say an OS46FX, TT46 Pro, or Webra 50 on a 13x4 would be a great place to start. Lower pitch props make hovering easier too!!

rcman-RCU

My Feedback: (31)

Good advice on setting the carb from Kevin. You might try a 12x6 prop to slow down the plane speed a little. That is what I use. The slim line pitts type muffler kills the performance of this engine. I've heard that the slim line for the os 91 2 stroke will fit this engine. It is larger and much less restrictive, allowing the engine to run much faster.

onrecess

My Feedback: (2)

Thanks for all the help. I'll try the prop and Kevin's adjustments next time out. (I know the 61 is overkill, I have an Extra Special with a GMS40. But... seriously overpowered is fun, too!) I'll let y'all know how it works out.
Thanks again!
Tom

Kevins_RC

My Feedback: (1)

There is a point of diminisioning return when it comes to overpowering a Fun-Fly. Weight is more the issue when it comes to aircraft performance (more specifcally wing loading). When you put and oversized motor, as you have, exspecially on a typically heavy plane (ARF), then you have to add tail weight to get it to the desired balance point, which further increases the wing loading. NOT A GOOD THING when we are talking about a Fun-Fly. This is why you see so much conversation on Fun-Fly forums on "What is the best engine?" "How do you make a moose can muffler?" "Where can I get a performance pipe for XXX engine", "How can I cut weight on aircraft XYZ?" Fun Fliers look for ways to get the aircraft weight down, and the HP up without adding weight (reducing weight if possible). If you put a good BB 40 - 50 on that Fun-Fly with a header and moose can, you'll find that it will out perform your present set-up easily!
TRY IT! - YOU'LL LOVE IT!
You'll also realize that it will be easier to practice and learn those manuvers that you mentioned earlier that you were trying to get out of this aircraft. (IMO)
Kevin

P.S. Stick with a 3 to 5 (max) pitch prop for a Fun-Fly. The lower the better. Go with a APC in composite props, and a B Y&O or Rev-Up (if you can fins one) in wood. Zinger will work, though doesn't have the pulling power of the other two wood props (ck out thread entitle "Props" in this forum). Once again - IMO

George E.

My Feedback: (16)

I have a 12.25x3.75 on my .61FX in a 5.6 lb Global Freestyle. Climbs like a rocket

onrecess

My Feedback: (2)

Hey thanks, guys. I put on the new 13x5 and set the mix like you said Kevin. Flew great. I had a couple of great flights and no problem. It was breezy so I could stop dead still until I couldn't hold the nose into the wind with the rudder. I even got it to hover for a few moments as it blew downwind. Much better, and I fly with such a low throttle setting both times I landed I had over a third of a tank left. No dead sticks from mixture (Or anything). Unfortunately, a county mounty asked me to leave the impromptu field by the bus barn. He said the owners are getting on them. (People apparently leave their trash.) At least he was real nice about it. I didn't have time to drive 30 miles to the park before dusk. I was happy to find a little place to test fly close to home, too. Two whole flights... just like fishing, I'm always there just a day late!
It was great, thanks!

Kevins_RC

My Feedback: (1)

Glad to hear that things worked out for you. It is always nice to hear back from someone with a sucess story after you gave them some advice. That is what these bulletin boards are really all about - Helping each other out!
Kevin