OK - gonna try the Cox Viper one more time.... - Page 3 - RC Groups
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Jul 02, 2001, 10:28 AM
AMA 697691 / FAA 13675

Nice article on the Cox Viper conversion. Great job!

I didn't see where you documented the final CG setting. I would also be interested in your results of the aileron version.

[This message has been edited by Greg Covey (edited 07-02-2001).]
Latest blog entry: Greg's Web Hangar
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Jul 02, 2001, 03:39 PM
What Canary?
KeithK's Avatar
I converted the P-40 using a GWS direct drive and 7 x 120NiMH cells. I thought tailerons would be a good way to go as the control horns are on the bottom and most people think it is still free flight. I cut the elevators close to the fuselage and made them full-flying. The first launch was exciting to say the least. Plenty of power, a nice straight climb, and it was going out of sight quick. Problem was when I tried to turn it rolled right into the ground. I still think this is an easy, clean method of control, but I am decreasing the throws WAAAY back for the next flight. Any one else using tailerons? BTW the stock P40 balances right at the leading edge of the spar so that is where mine balances.
Jul 02, 2001, 04:41 PM
Registered User
Steve McBride's Avatar
Yes I use them on my P40 but only use the elevator portion (not full flying). Worked ok, but I needed more roll. Next one will have less dihedral in the wing.

Have fun!

Jul 02, 2001, 07:59 PM
Strange Plane Central
frankenfoamy's Avatar

I didn't see where you documented the final CG setting. I would also be interested in your results of the aileron version.

The CG is on the spar. As you get used to it you can move it back alittle. I posted pictures and video of the aileron version.
The video doing rolls is the aileron version. http://phreak.mine.nu/drblott/RadioControlProjects.htm

Jul 03, 2001, 10:04 AM
AMA 697691 / FAA 13675
Nice video, thanks again.

I'll likely make the aileron version since I want this ship to roll. I'm assuming that you swapped rudder control for ailerons and don't use both.

Your "torque rods" are simply tiny metal rods either taped or glued into the ailerons?

I'm not exactly sure what DEPRON is but it looks like I could also use balsa or corraplast for implementing your camber reduction mod.

Finally, what was the drive system that you liked best on the Viper? The GWS direct drive or the N20 with 4:1 gearbox?
Latest blog entry: Greg's Web Hangar
Jul 03, 2001, 10:28 AM
Strange Plane Central
frankenfoamy's Avatar
The GWS motor direct drive has worked out the best. I have tried mabuchi 130 6v , N20 4.2:1 ratio also. both worked but not as good as the gws. The GWS motor has one weakness that I have found. It does not handle direct impact well. Look in the tips section of the web page for a fix.
I taped the rudder in place and removed the rudder servo for the aileron version.
The torque rods are 1/32" wire. I pressed a groove into the foam and taped over the wire in the groove.
The DEPRON is from a foam take out food tray.
Note that it is bowed a little to give it strength. This also had the effect of removing chamber from the medial 2/3 of the wing. The plane has never tip stalled. This is extraordinary considering its size and wing loading.
Jul 04, 2001, 07:40 AM
AMA 697691 / FAA 13675
In true R/C addict form, after eating out last night the waiter asked my wife if she wanted to take the rest of her meal home. She replied, "no thanks" but I spoke up and asked for several foam containers.

Now I have my supply of unused DEPRON.
Latest blog entry: Greg's Web Hangar
Jul 09, 2001, 03:37 AM
Registered User
Yep, lucked into a Viper at a local Wallmart in New Jersey near Edison.

Instead of a 6 or 7 cell pack I'm thinking of 3 x 800 mAh Tadirans. Has anyone tested with a 1AXC(carbon brush stik motor) with the Viper's prop? I'm looking for amp. pull @ full throttle and weight of the 6 - 7 cell packs you guys have been using. I hope the thrust of the motor/battery combo can provide plenty of power.

What do you think?
Jul 09, 2001, 07:22 PM
Registered User
Found a Viper at my local hobby shop today for $13!!!

I'm going to see if I can get this plane under 100 grams witht the following gear:

LS 2.5 servos
Sky Hooks RX
DC5 2.4 motor (direct drive)
2 Lithium cells

That should add up to about 40 grams with wire. I see the kit out of box weighs 80 grams. Take out the motor and the other stuff and 100 grams should be no problem.
Jul 09, 2001, 07:25 PM
Registered User
I'm surprise at how good the Viper looks! I'm thinking of covering it with aluminized mylar, using 3M 777 spray, or painting with acrylic for a real scale 'stang. Any other covering suggestions?
Jul 09, 2001, 10:10 PM
Strange Plane Central
frankenfoamy's Avatar
Becarefull using the 2.5.4 direct drive. I don't have any experience direct drive with them, but I know they do not like more than an amp draw. I pull 1.7 amps on 6 cells with the GWS motor.
I get .2amps higher draw with 15 grams less thrust with the carbon brushed version. I did not break in the brushes. Maybe that will make a difference.
Jul 09, 2001, 10:16 PM
Registered User
Mikey_Flies's Avatar
It should make a difference, but I'm not sure that it will make up the 15 gms of thrust loss or the amp difference.
Jul 10, 2001, 09:54 AM
AMA 697691 / FAA 13675
I still haven't received mine yet from Tower Hobbies.


I have the following motors available. Which would you choose for the Viper conversion?
  • N20 geared 4:1
  • MTM Hummingbird geared 5:1
  • N20 direct drive with U80 prop
  • G9330 motor with U80 prop

The G9330 motor is a similar, if not same, motor that drives the MTM Hummingbird.

I think the geared N20 4:1 that I got from Kenway has a 6" prop on it.

The 5:1 ratio version of the Hummingbird uses an 8x4 prop.
Latest blog entry: Greg's Web Hangar
Jul 10, 2001, 10:26 AM
Registered User
Question for all you Viper-ites: The left wing of the model has a built-in aileron deflection of about 3/32", presumably to compensate for motor torque. Did you leave this intact or remove it?
Jul 10, 2001, 10:30 AM
Registered User
[QUOTE]Originally posted by frankenfoamy:
[B]Becarefull using the 2.5.4 direct drive.

Decided to go with the GWS. More power.

My ship's almost done. Believe RTF weight will be about 95 grams.