Walled Lake, MI, USA
Joined Feb 2000
GWS DX Motor Prop Recommendations
The GWS DX motor system has become one of the most popular power options in slowflight, thanks to the popularity of the Lite Stik and similar aircraft that come with this system, reasonable cost and good performance. Each DX system (A through F) has a different gear ratio, with A being numerically the lowest and E the highest. However, there is a lot of confusion about what prop GWS recommends for each of its different DX systems because their original recommendations have been revised, but many internet sites still have the old recommendations posted. Below is a reproduction of the prop recommendation chart reproduced from the back of the package from a retail DX motor with explanations:
DX-A = 5.86:1
DX-B = 7:1
DX-C = 8.6:1
DX-D = 9.66:1
DX-E = 10.7:1
DX-F = 11.8:1
First 2 digits of prop = diameter in inches
Second 2 digits of prop = pitch
3 = Excellent
2 = Good
1 = Fair
0 = Don't Use
PROP A B C D E F
0947 1 0 0 0 0 0
0970 2 0 0 0 0 0
1047 3 1 0 0 0 0
1080 0 2 0 0 0 0
1147 0 3 1 0 0 0
1180 0 0 2 1 0 0
1260 0 0 3 3 1 0
1280 0 0 2 2 2 1
1365 0 0 0 2 3 2
1390 0 0 0 0 2 3
1470 0 0 0 0 0 2
I flew my stik with a 1047 and a 0970 and to be honest I didn't notice much differnce. Both worked fine with 7.2v lithium bat.
1) I'm a beginner 2) It was fairly windy
What difference in performance should I see between these two props?
Joined Oct 2000
Todd Long pointed out to me that going to higher gear ratios (C and over motors) required some pretty unusual designs. Essentially to use a D ratio motor, you need about 350 square inches with a single surface undercambered airfoil and the airplanes all up weight has to be under 10 ounces or so. Pure float in a pretty large airplane. Taking his suggestion- I used a B motor instead on my Super Snooper- a rubber powered duration model of about 200 square inches (with a big lifting stab)all up weight of about 8.5 ounces, and I think its swinging a 10 x 7 prop. Flies wonderfully, but it isn't very fast. In short- for most practical airplanes, only the A and B motor make a lot of sense because the pitch speed of the other motors is too low.
I can share my findings using the 10x4.7 and the 9x7 on my lite stick. For reference, my stick has about 1" dihedral added with a thread running from outer leading edge to outer leading edge. I use a factory GWS-A motor and power with a rayovac 9v (8.4) nimh. I use the GWS pico servos and receiver and did not add any stickers to keep weight down.
The 10x4.7 does give quicker ROG and a little better climb rate. The 9x7 gives better speed which is very handy when flying into wind. Battery run times are just about the same. All in all, my vote goes to the 9x7 for outdoor flying.
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