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Old Oct 11, 2004, 01:37 PM
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Joined Jan 2004
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Is my plane nose heavy?

Hi,
I built & designed a plane - it uses an ips-A on six cells.
wingloading is ~6 and weight is ~8 oz
It's a pretty basic, clean design (low drag)
so far I've only used a 9x7 GWS slowfly prop

My problem is, it won's stay up. It only sustains flight below 3 feet off the ground, but once it goes up out of the ground effect, it just goes back down.

It doesn't seem to be stalling, I think i just can't hold it up there.
Does that mean it's probably nose heavy?


I would be really grateful for any suggestions people have...

Thanks in advance,
-matt
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Old Oct 11, 2004, 02:03 PM
Registered User
Minneapolis Dntn, Minnesota, United States
Joined Aug 2003
93 Posts
Matter, What is the wing span? You are probably out of ground effect already at 3ft.

What are you using for a battery? Also you might try a seven cell battery for a little extra power.

Brian
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Old Oct 11, 2004, 02:11 PM
Motors beat engines!
Milwaukee Wisconsin, United States
Joined Feb 2001
4,564 Posts
Its possible that its nose heavy, but what it definately is ins underpowered.

With only 6 cells, your probally drawing well under 2 amps, maybe only 1.5 on 7v for about 12 watts or so for only 24 watts/lb.

It sounds like you have around 175 in/sq, so I punched it into motocalc, and got a stall speed of 12mph, a pitch speed of only 20 mph, ( you should have at least 30mph) and a max possible climb rate of 88 ft/.min at 3 degrees.

Its no wonder you could'nt climb.

Easy solutions?

1) keep your existing battery, but go to a ips s2 with 7x6, still won't be great, but it should fly.

2) Go to a different battery. 3s Lithiums with a 7x6 on your existing motor will get you all the way up to 350 ft/min climb, a very reasonable number for a parkflyer.

Good luck!

Dean in Milwaukee
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Old Oct 11, 2004, 02:46 PM
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Forney, TX
Joined Mar 2002
15,165 Posts
6 cells won't cut it for sure. Go with 7 cells Nicad or 8 cells NiMH; or try li-pos as Dean suggested. Whatever you choose, go light on the battery pack.
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Old Oct 13, 2004, 02:42 PM
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Thanks Everyone!

span is 30" - area is 195 sq in

Brian - I agree, it's probably out at 3 feet.
Thanks a lot for the info Dean.

The problem is I'm too cheap to buy a differrent battery or motor.

Is there any chance a diferrent prop would work a little better?


I might be getting a brushless soon (himax outrunner or typhoon 6) but I'm not sure it will fit this plane.

Thanks again - Matter
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Old Oct 13, 2004, 02:56 PM
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United States, CO, Colorado Springs
Joined Aug 2003
6,560 Posts
Not really. Dropping the pitch speed (with a new prop and/or gearing) will give you a bit more thrust, but when the prop is moving that close to the stall speed it really doesn't want to fly.
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Old Oct 13, 2004, 04:26 PM
Nickel what?
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Prescott, Arizona, United States
Joined Jan 2003
2,365 Posts
you'd have to change gearing to get another prop to work better... Just dont have the revs to get the prop to pull the airframe
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Old Oct 13, 2004, 04:30 PM
Australian in the USA
Paranoia's Avatar
Orange, CA USA
Joined Aug 2002
816 Posts
Tres Wright is correct you need a 7 or 8 cell pack or 2cell Li poly's. The power system can't provide what you need.


The other way is to decrease the wing loading, "make the plane lighter"
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Last edited by Paranoia; Oct 13, 2004 at 04:38 PM.
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