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Old 12-07-2007, 06:32 PM
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My F3P Design . . . 3rd Prototype finally flown!

Flew my third prototype of my design today. Didnt get to fly it indoors, but will hopefully be able to tomorrow night at the golf dome in Columbus (I think the fly-in is tomorrow night - correct me if I'm wrong).

Was light winds 1-2 mph and everything went well. This one weighs in at 5.75 oz with the battery (a little disappointing, but weight could've been saved more in certain places). This one had its CG further back than the others as well.

Flew super slow and had some small coupling. Rolls are crisp and stop when you want them too. Snaps are snappy (faster than a normal F3P bipe like the Vrolet) which is good for my liking. Counterbalances on the inner part of the ailerons create a good bit of drag, so when deflected they slow the plane down a good bit.

After five flights with my 2 cell 350 packs, I added my drag plates and put 3 more flights on it with me 2 cell 480s. SSSSUUUUUUPPPPPEEEEEERRRRR SSSSLLLLLOOOOOOWWWWW now! Absolutely the slowest flying plane that I've flown! I could do 1 1/2 rolls on a downline at around a gym ceiling height, and have a line on either side of the roll .

4th Prototype will have:

-1" Longer fuse
-Try to fix the coupling problem (either fuse area or rudder changes)
-milled
-pull-pull on rudder/elevator
-smaller carbon bracing in wings (.030" in wings, .020" on tail - IF I CAN FIND SOME - Any place to get this?)
-counter balance on tip of ailerons (more aileron authority when flying slow)

Any tips on fixing the coupling?

Seth
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Old 12-07-2007, 06:58 PM
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pic of version 3? have to see what there is to change in the way to fix the coupling.
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Old 12-07-2007, 08:11 PM
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Yup, what kind of coupling problem... Pitch or Roll, proverse or adverse?
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Old 12-08-2007, 06:11 PM
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jeez dad was logged in . . .
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Old 12-08-2007, 06:14 PM
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Sorry bout that . . .

Pitch to belly, roll same direction as rudder . . . pics should be in my last blog that was posted . . .
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Old 12-08-2007, 08:37 PM
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Pitch sounds like a missalignment in the build or a standard CG issue. The Roll coupling could be a vertical CG issue, but considering its the same direction as the rudder movement, I'm thinking its a rudder/fuse area issue.
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Old 12-09-2007, 09:42 PM
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would more side area on the bottom half of the fuse help the roll coupling or hurt it? If neither what would I need to do to correct it? Checked all alignments before glueing, and all should be perfect . . . everything is mounted below the horizontal fuse minus the rudder servo . . . would that create the pitch coupling?

Thanks!

Seth
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Old 12-09-2007, 09:45 PM
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Oh, and flew it today in an ice rink that was changed over to three B-ball courts. Happy with the slow speed characteristics . . . 1 roll on a downline can be easily done from a gym-height ceiling. Minor roll problem (my stupid fault - I have differential in the ailerons). Then also have the minor coupling problem, but it flies decently. . .

Seth
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Old 12-09-2007, 09:55 PM
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Pitch coupling is primarily (there are exceptions) about incidence alignments with the wing/tail, or CG issues. There are some issues caused by area, but that is definitely not the first place to look....

If it is pitching to the belly, then move the CG forward and re-trim the airplane for appropriate level flight. Then check the pitch coupling again in KE.

Fix that problem first, then worry about the roll coupling.
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