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Tuning with your snoot up in the air

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Tuning with your snoot up in the air

Old 05-05-2013, 08:06 PM
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tesol1
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Default Tuning with your snoot up in the air

The other day I was adjusting the high speed idle on my OS .75. The motor has a 114x4w prop on it so it's difficult for me to hear the change in pitch when I lean it out. I decided that I would try pointing the propeller of the plane straight up in the air and see if I could hear the pitch of the motor increase a little better than when it's sitting on the ground. It worked great. Does anyone else stick the snoot of their plane in their when tuning? Is it a better method for tuning? One thought I have concerns safety. I am not crazy about tuning the motor while holding it like that.
TESOL1
Old 05-05-2013, 08:47 PM
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jester_s1
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Default RE: Tuning with your snoot up in the air

That's pretty dangerous actually. The wings are like a big parachute in the wind, and you're only holding the plane with one hand. Pointing the nose up is something we do when tuning to make sure that we are set rich enough when level to not get too lean on a vertical climb. But that's after tweaking the needle valve. A much better method is to pinch the fuel line and listen to what the RPM does. The pinch makes the engine go lean, so what you're looking for is a quick rise in RPM when you pinch. It's pretty easy to hear that quick change, so it's good enough for most people. Buying a basic tach is a more precise method to go about it and will teach you a lot about getting good repeatable results. It's also handy for diagnosing problem engines as you can detect small changes in RPM that your ear wouldn't have noticed.
Old 05-05-2013, 09:22 PM
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JohnBuckner
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Default RE: Tuning with your snoot up in the air


ORIGINAL: jester_s1

That's pretty dangerous actually. The wings are like a big parachute in the wind, and you're only holding the plane with one hand. Pointing the nose up is something we do when tuning to make sure that we are set rich enough when level to not get too lean on a vertical climb. But that's after tweaking the needle valve. A much better method is to pinch the fuel line and listen to what the RPM does. The pinch makes the engine go lean, so what you're looking for is a quick rise in RPM when you pinch. It's pretty easy to hear that quick change, so it's good enough for most people. Buying a basic tach is a more precise method to go about it and will teach you a lot about getting good repeatable results. It's also handy for diagnosing problem engines as you can detect small changes in RPM that your ear wouldn't have noticed.

Bingo!

learning to tune a two stroke glow engine to a pinch is with just a little practice in my estimation a better technique than even a tach. Maybe not so much for a four stroke but definately a two stroke. Read Jesters post carefully as it contains great information.

I cringe every time I see folks holding their airplanes up and not even really listening or constantly gunning their throttles while doing so and carelessly blowing crap all over the flightline.

John
Old 05-05-2013, 10:02 PM
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Bozarth
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Default RE: Tuning with your snoot up in the air

Why not fly it a tad rich and see how it does in flight? If it leaves a descent exhaust trail and plenty of oil on the airframe, just leave it. Tweak it a bit between flights if you think you need it but blow off fiddling with it on the ground unless you are in the finals of a world championship pylon race.

Kurt
Old 05-05-2013, 10:07 PM
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Redback
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Default RE: Tuning with your snoot up in the air

You might try a smaller prop too. 114 is a bit big even for a 75

Terry
Old 05-06-2013, 06:52 AM
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LesUyeda
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Default RE: Tuning with your snoot up in the air

"Is it a better method for tuning? "

Tachometer.

Les
Old 05-06-2013, 07:04 AM
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flyinwalenda
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Default RE: Tuning with your snoot up in the air


ORIGINAL: tesol1

The other day I was adjusting the high speed idle on my OS .75. The motor has a 114x4w prop on it so it's difficult for me to hear the change in pitch when I lean it out. I decided that I would try pointing the propeller of the plane straight up in the air and see if I could hear the pitch of the motor increase a little better than when it's sitting on the ground. It worked great. Does anyone else stick the snoot of their plane in their when tuning? Is it a better method for tuning? One thought I have concerns safety. I am not crazy about tuning the motor while holding it like that.
TESOL1
That's the way I was taught and most folks I know perform that test when tweaking the high speed needle. You don't want to take-off , have it lean out half-way up ,and not have enough runway left to land or airspeed to turn around.

Old 05-06-2013, 08:35 AM
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Default RE: Tuning with your snoot up in the air

I can usually get my engines tuned fine on the ground, but there are times when I hold my plane up and make adjustments. Here is a picture of me doing it in my gallery, and if you notice, the prop is above my head. If there are people around me, it is actually safer for those around me if I hold the plane up in the air like this. If a prop breaks or comes off, it will go up instead of foward. However, it is not safer for me, because I have to hold the plane with one hand, and manipulate the tx and the needle with the other hand. Obviously, this would not even be an option with my 1/4 scale cub that is behind me in the pic. No way I could hold it up and adjust it by myself.

www.rcuniverse.com/gallery/galleryItem.cfm

Old 05-06-2013, 10:23 AM
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Bozarth
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Default RE: Tuning with your snoot up in the air

You guys sure do like to operate on the ragged edge.

Kurt
Old 05-06-2013, 10:54 AM
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flyinwalenda
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Default RE: Tuning with your snoot up in the air

Well it's as safe as can be especially when a spotter/helper holds the plane for you. I've never witnessed or heard of someone getting hurt tuning a plane while it's being held up in the air or one getting away  On the other hand I have witnessed accidents when pilots put their hands through a spinning prop trying to tune it while on the bench/ground. Common sense and safety should always be foremost.
Old 05-06-2013, 11:47 AM
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Default RE: Tuning with your snoot up in the air

Why in the world would you try to hold an 8lb object with one hand over your head withan11,000rpm blender on the end of it trying to pull it out of your handand find it safer than having it secured on a safety bench? Tune it so it runs and fly it, really they are just sport planes, and how fast do you need to go? What is 2-300 more rpm gonna matter. If you stand behind the plane and tune then you should not be sticking your hand in the prop or be hit by a blade coming off. NOONEshould be in front of the airplane at all except for the intial start. I see guys tuning from the front all the time, reaching over the prop to remove glow igniters etc. Just asking for trouble
ORIGINAL: flyinwalenda

Well it's as safe as can be especially when a spotter/helper holds the plane for you. I've never witnessed or heard of someone getting hurt tuning a plane while it's being held up in the air or one getting away On the other hand I have witnessed accidents when pilots put their hands through a spinning prop trying to tune it while on the bench/ground. Common sense and safety should always be foremost.
Old 05-06-2013, 02:56 PM
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Bozarth
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Default RE: Tuning with your snoot up in the air


ORIGINAL: raptureboy

[img][/img][img][/img][img][/img] Why in the world would you try to hold an 8lb object with one hand over your head with an 11,000rpm blender on the end of it trying to pull it out of your hand and find it safer than having it secured on a safety bench? Tune it so it runs and fly it, really they are just sport planes, and how fast do you need to go? What is 2-300 more rpm gonna matter. If you stand behind the plane and tune then you should not be sticking your hand in the prop or be hit by a blade coming off. NO ONE should be in front of the airplane at all except for the intial start. I see guys tuning from the front all the time, reaching over the prop to remove glow igniters etc. Just asking for trouble
100% agree with every word you wrote.

Kurt
Old 05-06-2013, 04:04 PM
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flycatch
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Default RE: Tuning with your snoot up in the air

Your not inventing anything new. That method of tuning was a standard practice that seems to have gone away. You don't do it alone though it takes two people. One to hold the plane by the fuselage and wing panel and the other to make engine adjustments.
Old 05-06-2013, 04:29 PM
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hugger-4641
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Default RE: Tuning with your snoot up in the air

You are correct, no one should be in front of the plane, but you can't always control what other people do while your back is turned and you are focused on keeping your hands out of the prop. I have seen props fly off from the starting stand and hurl down the pits, but a prop that flies off while overhead is only going to fly up, then fall back down, and usually not far away.

I don't do it often, and I'm not recommending it as a common practice, but it's one more tool in the box if you can do it safely. And contrary to your assumptions, it's not a matter of a few extra rpm's for me. It's a matter of certain engines that are finicke. Experimenting with certain fuels can make tuning any engine finicke. I have one Super Tiger .45 and a .40 Thunder Tiger that are super sensitive to HS needle adjustment, one click too rich and it stumbles in mid range, one click too lean and it will dead stick, and it doesn't matter much what fuel they are running on, they are just more sensitive than all my other engines, especially if it's hot and humid out. It may not be the case in the rest of the country, but here in West TN the temperature and humidity can go to extremes in a matter of hours. When it's 50 degrees and 30% humidity one day, and 85 degrees and 90% humidity the next, even the most reliable O.S. engine that flew perfect yesterday will often need adjustment.

As I've already mentioned, 90% of the time, tuning on the bench works fine for me, but every once in a while, pulling the nose up on plane will tell a different story and expose problems that don't show up otherwise.
Old 05-06-2013, 05:25 PM
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hairy46
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Default RE: Tuning with your snoot up in the air

Don't think thats very safe, pinch test works great!
Old 05-06-2013, 05:33 PM
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gsoav8r
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Default RE: Tuning with your snoot up in the air

Tacks are nice but not everyone gets or keeps one on hand. Least not around here. Thou I keep one in my field box and test with it as well, theres been many times Ive been at the field flying electric (plane, radio and batts only) and didnt bring the box with tach and needed to help a fellow modeler tune an engine.

Pointing a model to the starz to test the tune is a great way to find probs. Just dont tune while holding the model up. That is dangerous.
We tune on the ground or on the bench. Then run the throttle up and point her to the sky. If adjustments are needed we put the model back down.
While holding the model up its also a good idea to have a helper transition the throttle slowly from idle, to mid, to full and then back again. If the engine can handle that a couple times its normally good to go.
Been doing it this way for well over a decade when the ole' pinch test just wont get it. Like on models with nicely cowled installs.

Like Hugger said, another good option to have on tap.

Cheers.
Old 05-06-2013, 06:33 PM
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lopflyers
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Default RE: Tuning with your snoot up in the air

OMG, for crying out loud a tach is not that expensive
Old 05-07-2013, 05:15 AM
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Default RE: Tuning with your snoot up in the air

Lopflyer, tach's are great, I have two that I use regularly, but read my post closely. A tach is just another tool, it can't simulate the nose up attitude of the plane which can identify other problems.

Harry46, the pinch test is great, I use it all the time, that's what I was doing with that Avistar I'm holding up in the air. It was being unusually contrary that day due to heat and humidity and the fuel I was using. Read my post closely. 
You can't reach the fuel lines on many of my cowled planes like my Venus and P-51, so the pinch test is not possible on these.
Old 05-07-2013, 06:13 AM
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Default RE: Tuning with your snoot up in the air

Thats the way i was taught back in the 70's when i started flying pattern. I
never had an issue and have always looked at safety as #1.

G Sheetz
Old 05-07-2013, 07:55 AM
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tesol1
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Default RE: Tuning with your snoot up in the air

Thanks everyone for the good advice. I didn't like the idea of adjusting the high speed needle while it was in the air very much, so I will definitely get a tach. I have had a few deadsticks that resulted in the death of one my planes and so I am a bit overzealous about getting the high speed setting right. I go through the whole thing with putting the nose up in the air and the pinch test before every flight, but the deadstick problem is still on my mind. Anway, carefully checking the motor has prevented any deadstick landings in the last month, but I think that I will add a tach to my toolbox. Thanks again!!
Old 05-07-2013, 06:14 PM
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Default RE: Tuning with your snoot up in the air

I was more than a bit surprised with my .75AX the other day. Usually tuned with a tach every few sessions ~250rpm below peak and flew out most of the tank then tached it after landing with nearly empty tank, nose level, nose up and there was no change in rpm (within ~50rpm).

OK, it's only a 10oz tettra bubbless tank with a YS foam pickup, installed in the plane backwards to get it right up against the firewall, but the RPM stability nose level to nose up was surprising. 5% nitro 22% oil (11% castor 11% coolpower blue) and the rest methanol...

I haven't used the nose up method for years since I bought my first pumped engine for F3A work, but with the non-pumped .75 it's a bit a reasurance every now and then to just pop the nose up at full power after landing with a nearly empty tank just to double check it's still rich enough not to sag and see that there's no air getting into the lines. I wouldn't touch the needles while I'm doing it though, in fact I always adjust the high end needle about 2 clicks at idle, then throttle back up and measure the new rpm.
Old 05-15-2013, 01:06 PM
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Default RE: Tuning with your snoot up in the air

The whole purpose for the 'nose up' test is to make sure the engine is not too lean. The proper way to do it is to adjust the needle with the plane level and THEN stick the nose up with it running at full throttle. If it loses rpms then it's too lean. Richen it up a little and try again.

You'll never catch me adjusting my engine anywhere but behind the prop. Some of us needed to learn that the hard way!

Bill
Old 05-15-2013, 02:08 PM
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vicman
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Default RE: Tuning with your snoot up in the air

Tweaking???
Why not set? If you are tweaking so close on the high end that it leans out nose up you are way too lean. Like Kurt said earlier, give it several clicks rich and fly the thing. Again quoting Kurt, unless you are in the finals of a pylon race there is no gain from running that close. Run rich by 2-500 rpm and fly for a long time with a healthy motor.

Honestly I go to lean and back off nearly a half turn most of the time, and that's on a pylon racer.[X(]
Old 05-15-2013, 02:44 PM
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Bozarth
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Default RE: Tuning with your snoot up in the air

vicman,

You made me nervous when you started quoting me!

I learned years ago from "Mr. RC Pylon Motor Expert Mike Del Ponte" that the best way to needle a two-stroke motor was to see how rich you could set it and still fly fast, not how lean you could set it.

Kurt
Old 05-15-2013, 03:21 PM
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speedracerntrixie
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Default RE: Tuning with your snoot up in the air

I'm amazed at how many of you guys think you are going to get a good tune while on the ground. Sure get it running well but do your fine tuning based on what you see and hear while in flight. The conditions between a static run and in flight are so different that you will never get it 100% right on the ground. I tend to laugh when I see someone run 1/2 a tank of fuel on the ground trying to tune while the engine just gets hotter and hotter.

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