Richard39

My Feedback: (14)

I have been trying to solve an engine problem on my 60 size Extra 540 with a Saito 91... normal weight and set up , with a 13 X 8 prop and 20/20 power master fuel... Engine appears to lose power in a normal loop...near the top... have tried everything... props, timing, fuel, etc... Nothing helped... so a friend loaned me his Saito 100... guess what ...? The same results... Engine can not pull airplane thru the loop... So this now indicates the problem is not with the engine unless both engines were set up to run lean in flight... I hope not as I set up engines to run a little rich, 200 rpm under peak performance on a stand..

The fuel tank center line is set up 3/4 inch high on the center line of the carburator... The engine is inverted... It has been suggested to me yesterday at the flying field that the tank location could cause a loss of power going up and before going over in the loop.. If the tank is 3/4 inch high during level flight then it could be lower than the carburator during the up side of the loop...loses power, goes lean, etc... What do you think..?

Airplane takes off as if it needs more power but flies a straight line and rolls beautifully.. I am going to lower the tank a little and try to fly a steep climb before doing a loop... say 80 degrees up.... The 91 Saito with the 13 X 8 prop is doing 9400 rpm and the Saito 100 is doing 10,200 with the same prop.... The Saito 91 engine turns high rpms (11,000 plus) with a 14 X 4 Wide and a 13 X 4 on the stand but still does not loop with either prop... everything seems to be pointing to a loss of power as the engine goes up more than 60 degrees and starts a lean run due to fuel starvation... Again... What do you think...?

broke_n_bummin

Try a smaller pitched prop ... 14X6 or a 15X4 would be a better prop than a 13X8 The X8 will go faster but less pull. You're losing power at near vertical and the plane is stalling. I don't think it's the engine or fuel.

Charley

My Feedback: (2)

Mo Bettah, you set the engine up in the airplane instead of on a stand. By all means move the tank so that its centerline is even with the carb. Then set up the engine with 1/2 tank of fuel, fly it and adjust as necessary.

BTW, I fly a Cloud Dancer 60 with a inverted Saito .80, 12x7 Zinger and 10% 2-stroke fuel.

CR

NM2K

My Feedback: (14)

"If the professor on Gilligan's Island could make a radio out of 2 coconuts, why could't he fix a hole in a boat?"


I can think of two very good reasons why I wouldn't want to leave too early. One is named Ginger, the other Maryanne. <G>


Ed Cregger

RCVFR

My Feedback: (7)

The problem is probably with the plane - too heavy? Also, it's probably confused as to whether it's an Extra or an Edge 540.

pilotpete2

Richard,
When you tune your engine on the ground and think the high speed mixture is correct, do you then pick up the plane with the throttle wide open (preferably with a helper) and hold the nose straight up for 10 to 15 sec? if it starts to die, then either you are too lean on the high end or have a problem with your muffler/tank pressure. As far as tank position goes, in this case it's not the tank hight but rather how far back in the fuse the tank is from the engine, closer to the engine is best.
Goos luck,
Pete

NM2K

My Feedback: (14)

Your question has me wondering just how large your loops are, if you know what I mean?

You need to even out your fuel mixture between upright and inverted. The best method is with a Cline or Iron Bay regulator using muffler pressure. Then when the engine is tuned for 200 rpm down from peak, if it doesn't pull it with a 13x7, you have a heavy airplane, or a weak engine. Yes, both could be weak. Not likely, but possible.

Notice that I changed your prop to a 13x7. It might be worth a try. A 13x4 isn't enough prop for these engines. The Extra type models have to fly along at a good clip to have any good knife-edge or linear rolls.


Ed Cregger

pe reivers

I would try a richer setting first and see if it helps the engine sagging condition. If it does, Then rearrange the fuel tank, and/or use a pump. A bit more nitro combined with a richer setting also helps. The extra nitro tends to broaden the mixture range for good power.

onewasp

I have no way of knowing but when did you last check your valve settings?
You'd be surprised how far 'off' performance can go-----your description is a little extreme but you never know.

BTW WTH is an Extra 540?
Extra 260; 300; 330.
Edge 540.
Matt Chapman's CAP 580 -------but an Extra 540???

Richard39

My Feedback: (14)

Sorry... Edge 540

Richard39

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Airplane on Flight Stand

Richard39

My Feedback: (14)

Yes we do ... will move tank .. thanks ..

Richard39

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Thanks to all... valves set .. both engines ..

Richard39

My Feedback: (14)

Sorry for the short replies but my computer is acting up.... I am at the Library now so here goes: First.. thanks to all for the great suggestions and questions... I just moved a new fuel tank up an inch closer to the firewall and dropped the tank to center line to center line with the carburator... I believe that there may be a back pressure problem as the line is the small tubing and the metal line going into the tank seems to be small and with the curve may be resisting the air flow... The line from the stock muffler to the tank is about 8 inches long... Now with all new connections, new lines and the relocating of the fuel tank I will have done all I can to the airplane... Will fly it on Monday....

I have tried several props in static testing and believe that the 13 X 8 should do the job... Remember that I have first used the Saito 91 and now the Saito 100.... If both engines can not pull the airplane (60 size) then I need to go back to my other engines, O.S. and Magnum... both 90"s and both do everything I ask of them with 60 size airplanes..

Both engines have the valves adjusted per Saito instructions... and it would not be likely that they are both running lean or losing power due to an engine adjustment which is well to the rich side of highest rpm lean. But to be safe I will go another 100 rpms to rich.... Again .. Thanks...

broke_n_bummin

I still think a 13X8 is too small ... I can run a 13X8 on my .70 surpass. Check the suggested prop size for the Saito 100. It should be in the 15" - 16" range.

exeter_acres

My Feedback: (2)

Prop is Waaaaaay tooooo small... really... it is...

no fibbing...


and EXACTLY how much does the plane weigh....not a guess.. but weighed on a GOOD scale?

blw

My Feedback: (3)

Saito recommends down to a 11x10 for aerobatics. Max RPM is 11,000.

NM2K

My Feedback: (14)

Yup, prop size is dependent upon the model you are flying as well as the engine powering it.


Ed Cregger

broke_n_bummin

On a .40 size ultrasport, that might be a great prop ... plenty of speed. A .60 size 540 with a Saito 100 would weigh close to , if not over 8 1/2 pounds. You're going to need more static thrust to go vertical from level flight. That plane wasn't made to go fast. It's designed to do things normal planes can't do at near stall speed. That 11X10 @ 1100 RPm is only going to put out about 5.31 pounds of static thrust A 16X4W @ 10000 RPM will give you 19.66 pounds of static thrust. Your 13X8 is only putting out 10.37 pounds if you're turning 11,000 RPM (these figures according to ThrustHP).

piper_chuck

My Feedback: (12)

Setting an engine a bit on the rich side by measuring RPMs is not a reliable method of determining what will happen during vertical maneuvers. Hopefully you didn't miss an earlier post in this thread, but it's worth repeating:
I will go one step further and suggest that in addition to not wanting the engine to sag while you're holding the plane with the nose straight up, you want the engine to pick up a little speed when you first point it up. If it doesn't pick up a bit of speed, it will be too lean for vertical as the tank drains.

Richard39

My Feedback: (14)

Thanks to all for your replies... very good information and suggestions.... The airplane is set up to fly and all testing has been done with the engine installed in the airplane... The airplane has been held up by a friend while going to full throttle to test ... problem there may have been that we only held the airplane for 5 to 10 seconds ... but the airplane/engine performed great in the test... I have not tried to do a vertical flight yet except in the loop... The next flight will be extensive.. both vertical and loops to determine if the changes that I have done have helped..... Fuel Tank lowered about 3/4 inch. Tank moved forwarded about one inch...(The set up on this arf had the fuel tank about an inch back from the firewall) a new fuel tank and all new connections and fuel lines..... I also made a minor adjustment in the incidences as I found the wing to be 1.5 degrees negative... who knows at this point what is wrong and what changes will be the correct set up...

As for props ... the 13 X 8 is a bench mark prop and not intended for the normal sport flying that I will be doing... I have tried many different props and all have been unsatisfactory in LOOPS....Will not pull through a loop... Remember that I have tried many props and two different engines on this airplane... Both a Saito 91 and a Saito 100... Same results will both engines and 4 different props... The 91 will only swing the 13 X 8 prop 9400 rpm's while the 100 will only swing the 13 X 8 at 10,200 rpm's ..It seems that the engine is going lean in the vertical part of the loop and losing power... Rembember that BOTH engines have failed to loop this airplane.. The changes with a new tank and position changes will help determine if that is what caused both engines to lose power.. May even try a pump ... When the airplane flies in a somewhat normal manner.. then we will try bigger props... One prop that I tried before was a 14 X 6 which is a prop that I use on my O.S. and Magnum 90"s with great success...

I also plan to go as rich as possible within reason and makes adjustments after each flight to find the sweet spot for that airplane and engine... All test now will be with the Saito 100... After that if the airplane performs well then I am going to try the 91 for comparison... After all the 100 is only on loan for these test purposes....

Richard39

My Feedback: (14)

Did not fly today as planned.... but did run up the engine using a 14 X 6 prop on the Saito 100 engine... 9900 rpm's..... next chance to fly will be Friday.... I did weigh the airplane dry today with scales, not good or expensive but will have to do for now, total weight was a whooping 9.0 pounds... I would have bet on 8 1/2 pounds... This is an arf from Seagull and with the Saito 100 it did weigh 9.0 pounds... I hope the 14 X 6 prop will OK for that engine and airplane weight as that is the prop that I will use on all future test...

NM2K

My Feedback: (14)

I wish I could be at your field while you are flying the model.

A Saito .91 should be able to pull a nine pound model through a loop with ease. I'm thinking that there may be a plumbing problem/tuning problem/etc., that is causing your problem. Conceivable, even a trim problem with the model.

My Bridi Deception of 1982 weighed 9.5 lbs., yes, it was heavy. It was my first fiberglass and K&B Superpoxy paint job model. Plus it was built from a kit with heavy wood. With that said, the OS .61 FSR with tuned pipe (tuned for the climb) would loop that model at half throttle. While I'm not sure that the Saito .91 was anywhere near as strong as the the piped OS .61 FSR, it sounds close enough that your model should be looping with ease, if everything is okay aerodynamically.

I have seen some set ups (incidence/etc.) that could make looping without a snap roll at the top really rough to accomplish.

I have both the Saito .91 and the 1.00 and love them both. I am a big Saito fan. They are kind of like a bulldog - they grow on you after a while.


Ed Cregger

edited by moderator

1THEPALMER

My Feedback: (1)

Get a bigger prop and quit trying to get high RPM. The engine delivers best power when loaded down with a big prop..
10000 RPM on the ground is too fast. I still think you are way too lean. OPEN THE HIGH SPEED NEEDLE AT LEAST 1/2 TURN!!!!!!!!!

Richard39

My Feedback: (14)

[quote]ORIGINAL: Ed Cregger

I wish I could be at your field while you are flying the model.

A Saito .91 should be able to pull a nine pound model through a loop with ease. I'm thinking that there may be a plumbing problem/tuning problem/etc., that is causing your problem. Conceivable, even a trim problem with the model.

My Bridi Deception of 1982 weighed 9.5 lbs., yes, it was heavy. It was my first fiberglass and K&B Superpoxy paint job model. Plus it was built from a kit with heavy wood. With that said, the OS .61 FSR with tuned pipe (tuned for the climb) would loop that model at half throttle. While I'm not sure that the Saito .91 was anywhere near as strong as the the piped OS .61 FSR, it sounds close enough that your model should be looping with ease, if everything is okay aerodynamically.

I have seen some set ups (incidence/etc.) that could make looping without a snap roll at the top really rough to accomplish.

I have both the Saito .91 and the 1.00 and love them both. I am a big Saito fan. They are kind of like a bulldog - they grow on you after a while.


Ed Cregger





Ed.... what incidence would cause the airplane to not loop and snap roll at the top... ?I found the airplane had 1.5 degrees of negative incidence in the wing but have corrected... The wing and the elevator now are at 0 degree incidence.