Diverig

Hello

I am in the proses of building a SPAD 3DT.

This is going to be an up scale of the original. my question is do I move the CG the same amount as the upscale measurements which is *1.79 or do I have to recalculate the all together?


My other question is what prop would be a good starting point for a new ASP 1.08?

Thanks for the help

Tall Paul

The new c.g. should be in the same place percentage wise as it was on the smaller plane.
Your linear factor should accomodate that.

rccrazedman

My Feedback: (10)

doesn't your motor's instructions tell you what prop should be used ? If not I have a little book here from sig "the basics of radio control" which states for a a 1.08 2 stroke motor is a 16-6. Some alternate props listed are the : 15-8 and 18-5.

For a four stroke motor the .90 are 14-6 with alternate props of : 13-6, 14-8, 15-6, and 16-6

The 1.20 4 stroke is listed at 16-6 with alternate props of 14-8, 15-6, 15-8, 16-8, 17-6, 18-5, and 18-6
Now I don't know if your motor is the 2 or the 4 stroke. If it's the four stroke motor I would say go with the upper end of the .90 to the lower end of the 1.20. I hope this helps

Diverig

Thanks for the help.

rccrazedman

I have had this engine for ten years and the box and instructions aare long gone.

Thanks for the list of prop sizes.

DBCherry

My Feedback: (4)

You can use this diagram to determine the Mean Aerodynamic Chord, and the CG.
Dennis-

rccrazedman

My Feedback: (10)

No problem . Glad to be helpfull