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Old May 03, 2003, 07:15 PM
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Massachusetts
Joined Feb 2003
27 Posts
Newbie needs troubleshooting help

Hello Everyone,


I need some help getting my plane off the ground.

Here is what I have:


small park flyer warbird w/ a 30" wingspan, and 160 sq inches of wing loading.


graupner 6v sp 400 geared w/ a 4:1 planetary gearbox attached

11x8 folder prop

castle creations 20 amp esc

1100 mah HE nimh 8 cell pack


plane stalls after about 10 ft.


any help as to where the problem might be would be greatly
appreciated


thanks in advance for the help


skydog
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Old May 03, 2003, 08:06 PM
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Joined Apr 2003
121 Posts
You are probably not launching fast enough. Try these solutions one at a time.

1.The best solution would be to have someone run like a maniac and give it a gently toss at full throttle to get it in the air. If the model is built + powered right, it should take right off.

2.Also, 11x8 seems kinda HUGE. I use a 7x6 on my Speed 600 direct drive, but I dont know about gearboxes. Try a smaller or lesser pitched prop too. I use an 11x7 on a .46 FX usually(gas motor).

Be VERY careful with that 20A ESC and that big prop. It may take more than 20A draw with that big prop. Try using Motocalc or Pcalc to calculate the draw and ensure that the control will take it.
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Old May 03, 2003, 09:14 PM
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Los Angeles, California
Joined Apr 2002
923 Posts
Do you mean 160 sq.in. of wing area? Wing loading will depend on how heavy your plane is. If you have a high wing load, and depending on your airfoil, you may not have enough airspeed with such a big prop and a 4:1 ratio with a sp400. I don't have a calculator but someone else may be able to tell you the pitch speed on the 11x8 depending on your rpm.
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Old May 03, 2003, 09:23 PM
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Massachusetts
Joined Feb 2003
27 Posts
Yes, 160 sq inches of wing area

Hello,


Yes that would be 160 sq inches of wing area and the AUW is at about 15 oz.


thanks for the help
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Old May 03, 2003, 09:31 PM
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Los Angeles, California
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Does your wing has a lot of lift? Did you use full throttle when you launch?
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Old May 03, 2003, 09:37 PM
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Los Angeles, California
Joined Apr 2002
923 Posts
Oh, I think I missed something.

160 sq.in. is slightly larger than 1 sq.ft. With a 15 oz. plane, you have pretty high wing loading of about 13.5 oz/sq.ft. You will need a lot of lift or you will need a lot of speed.

My suggestion will be a lower gear ratio and smaller prop with the same pitch.
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Old May 04, 2003, 03:14 AM
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N. Staffs, UK
Joined Jan 1997
5,654 Posts
I too would have used a direct drive S400 or a much lower gear ratio on a model like that. However it should fly with your setup though it will need a strong launch. With that high pitch prop it needs to build up speed before the prop "bites" well.

Whatever you do, don't try to put any up elevator in until it is well up to speed. If anything launch with a little down trim and only pull up when it has sunk as close to the ground as you dare.

I assume you are handlaunching. I'm having trouble imagining ROG with 30" wingspan and an 11" prop .

Steve
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Old May 04, 2003, 03:19 AM
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East Anglia, UK
Joined Sep 2002
29,689 Posts
You problem is simple. Throw the gearbox away and fit a Gunther prop for direct drive, and heav it mightily on takeoff.

You simply can't get the sort of power and pitch speed out of that combo without using a 13x12 prop or whatever, and that is so big its gonna roll the model after launch, and in any case it hasn't got the pitch speed to take it safely above stall speed. The sort of model that motor and box would suit is a sailplane that flies and climbs at 20mph or so.

All the speed 400 warbirds of that sort of size - eg QEFI spitfire, Nigel Hawes smaller tucano etc - all use the direct drive system on soemthing like 5.5x4.5 prop - and the Gunther is as good as any.
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