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Old Jun 27, 2008, 03:18 PM
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Pondside Handling

I've built three Scott Hartmann Pondsides. This time I added ailerons. Using a Rimfire outrunnermotor and 2100 MAH LiPoly. Loads of power ! ! Light airplane.

Carl Test flew the airplane over land using hand launch. Good thing that the field sloped down. Immdiate drop upon launch followed by some pitch up. Got it under control and noticed the same characteristic as previous PS. Just as a side note I've balanced it a bit nose heavy.

-Tends to pitch down on hand launch.

-Tends to "balloon" and pitch up on turns, so I keep turns shallow.

-Tends to pitch up on power reduction

Any comments re: center of gravity, motor up- thrust, wing wash in/ out (I'm not sure which is which).

Carl T at Cape Cod
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Last edited by ctrevison; Jun 27, 2008 at 03:23 PM. Reason: Message Not Finished
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Old Jun 27, 2008, 05:38 PM
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Joined Jan 2005
842 Posts
Sounds like you could use a bit more upthrust.
Leverage from the high thrustline can push the nose down with added power. Upthrust both lifts the nose and directs a bit more propblast down onto the elevator. Conversely, once you've trimmed the plane for power (up elevator) when you chop power the downward moment goes away and the plane balloons up.

Try a washer at the time, I suspect you'll need 2. (~4 degrees)

Center of gravity: Trim the plane for level flight at normal cruise throttle. Push the plane over into a shallow dive then release teh elevator.
If it's balanced propely, it just continues the dive.
If it pulls out of the dive, that's a sign of nose heaviness. Extra up trim needed to overcome nose heaviness becomes more effective as speed increaes . Conversely a tail-heavy model will want to tuck and stepen the dive.

Probably with the high-mounted engine it should ideally gain enough speed to cause the prop to windmill and it should pull out gently.


WHen you're flying along at cruise power, you should be able to change the throttle setting without affecting the plane's pitch.
Another test for nose heavy is to roll it inverted and if it's nose heavy it'll take a lot of forward stick to make it fly inverted.
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Last edited by JimCasey; Jun 27, 2008 at 05:45 PM.
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Old Jun 29, 2008, 09:00 AM
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Pondside Handling- Thanks Jim

Thanks Jim. Everything that you say makes sense. I'll try some washers, one at a time and do some conservative tests as you suggest.

Hi thrust lines can certainly complicate trimming out an airplane.


Carl at the Cape
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Old Jul 07, 2008, 10:42 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,761 Posts
Bah-

The problem with the high mounted prop on the airplane is that no matter how you jigger the prop angle, it's still way above the wing and is going to torque the airplane when it's powered up. Best solution? Ditch the high mounted engine and go to a pair of wing mounted motors instead. I flew mine with a pair of Speed 400 7.2Vs and a 10 cell nicad pack- flew fine. Nice water handling on the airplane. By the way, I also tweaked the airfoil on my second Pondside wing (the original was glow powered.)

In terms of turns though- if the power is on consistently, then what you're describing sounds like you've got too much noseweight- when the airplane picks up speed, it wants to climb. If you're worried about a stall- add some washout- the trailing edge of the wingtip should be higher than the root when the wing is on a flat surface.

Sam
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Old Jul 13, 2008, 09:47 AM
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Central Lake, Michigan
Joined Dec 2002
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I've flown my Puddle Master several times and found it does indeed need some upthrust. Incidently it has been flown with several can motors and last time a Magnetic Mayhem with a GP gearbox and 8 cell Nimh. That was several years ago. Now it has an Atlas Am2909/20 outrunner and will use a 3S lipo probably a 3100Mah.
Right now I'm building the "Super Puddle Master" from plans I bought from Kiona Pub. I may just convert it to a twin to alleviate this problem.
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