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Old Jun 17, 2006, 03:14 PM
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Joined May 2006
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Help!
GWS Moth 31.5 inch span.

I have just finished converting my rudder and elevator tiger moth to coupled ailerons by using 6mm depron for the wings but have left the tail end as is. I have also changed the motor to an EPS 350 C gearbox one as per the so called 3D model. I will be using 11.1v lithium polymers but am not sure which would be a good prop size to match. Also does anyone know
where the C of G should be? The model now weighs just under 14 ounces. Any advice appreciated. Thanks.
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Last edited by Tony77; Jun 17, 2006 at 03:23 PM. Reason: incorrect info on motor
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Old Jun 17, 2006, 06:18 PM
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Darwin Australia
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Quote:
Originally Posted by Tony77
Also does anyone know where the C of G should be?
If your wings have exactly the same area, sweepback and span as well as being mounted in the same place as the original wings then the CG will not change.

Ken
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Last edited by kensp; Jun 17, 2006 at 06:24 PM. Reason: correct text
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Old Jun 17, 2006, 07:58 PM
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Thanks Ken. Yes the wings are the same except that they now do not have any dihedral at all or any camber. Any ideas as to the prop size? Regards. Tony.
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Old Jun 17, 2006, 08:16 PM
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350c-c

Quote:
Originally Posted by Tony77
I have also changed the motor to an EPS 350 C gearbox one as per the so called 3D model. I will be using 11.1v lithium polymers but am not sure which would be a good prop size to match. Thanks.
Tony 77;
From the GWS 350C-c chart they do not recommend more than 9.6Volts and less than 10 amps on the 350 motor so an 11.1 lipo is not good.
http://www.gwsus.com/english/product...em/eps350c.htm
Bob
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Last edited by bob2005; Jun 17, 2006 at 08:17 PM. Reason: name
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Old Jun 17, 2006, 08:42 PM
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Thanks Bob. Have taken on board what you say and might now re-think the situation. I'm still trying to get a line as to prop size though. Any views on this? Tony.
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Old Jun 17, 2006, 08:49 PM
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The GWS web site for the 3D Tiger Moth lists an EPS-350D 6.6:1 geabox and a GWS EP1147 Propeller using 8 cells NiMh.

So for a 5.33:1 gearbox one would have to first try a GWS EP1047 and 2 cells LiPoly. MotoCalc predicts that this would be the best GWS propeller. For 3 cells I would go for the APC 9 x 3.8 Slowfly to drop thr currnt draw and pitch speed.

I think that with 3 cells that the thrust will be so greatly in excess of weight that it will be very sensetive to throttle when hovering.

Ken
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Last edited by kensp; Jun 17, 2006 at 09:01 PM.
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Old Jun 17, 2006, 09:20 PM
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Thank you once again Ken for your interest. I shall try the EP1047 and the 9 x 3.8 with two and three cells. As I don't have either of these props in my miserable collection, I shall have to wait until I visit my model shop after the week end. Tony.
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Old Jun 19, 2006, 01:41 AM
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Hi Tony,

It'd be much better to use 9.6V NiMh pack or 2S LiPo pack with EPS350.

Chen
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Old Jun 19, 2006, 08:41 AM
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Hi Chen,

Thank you for your message. I have several 2S LiPo packs but no NiMh so I will be trying the LiPos as soon as the weather permits. Thanks again. Tony.
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