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Help! Minimum Propeller Clearance on Flyer?


After completing my build of a Flyer from the swappable-model kits I had received, I realized that with the larger propeller there's only about a one-inch clearance when the model is in the tail-up, horizontal position (see image). That seems to allow a very small margin of error during takeoffs and landings.

I followed Flite-Test's YouTube build video when creating the landing gear, but I'm wondering if I need to make another version for the large propeller, one that gives the propeller some more clearance.

My idea has been to use the larger propeller to begin with for slower flight while I sharpen my flying skills.

Thanks for your help,



Well-known member
You should probably hand launch anyway until you get the hang of flying it. Then land in the grass with no throttle.

In my experience, the Flyer will never be level on takeoff and landing anyway. It needs a nose up attitude to produce lift as it does not have an airfoil.
It needs a nose up attitude to produce lift as it does not have an airfoil.
I'd prefer to take off rather than hand launch, although I've done both with a different model. Should the trim be set with a little up-elevator to avoid the nose dipping during takeoff and landing?



Well-known member
Mine flies with a little up elevator. With a new plane, I usually just throw it in the air and then trim it while trying to keep it in the air. Not really the best method.

You can trim it for best glide with no power. Toss it with some up elevator and see how it glides. Give it more or less trim until it looks right.

For me, if I try to take off with a new plane, it usually does some weird left turn or nose dive or something. Hand launch on the first flight works better for me. Sometimes, you just have to set it down, give power and hope for the best though.


Slow, low and dirty.
I don't think a larger prop correlates to slower speeds, only to slower motor RPM which may prolong battery life. Keep in mind that as you add prop diameter you also add torque and adverse yaw issues. That's the problem I found with the newer B Power Pack motor. The old one turned a 9" prop faster and would keep my simple cub aloft at 1/2 throttle. The new one is less efficient with the 9" prop because it turns slower per volt, so it will fly on a 9" prop but it has more power and endurance with a 10" prop. Of course then I'm fighting torque and adverse yaw. I generally build my planes with 2-3 degrees of right thrust angle so they fly pretty straight, but the torque is an issue during launch.
I don't think a larger prop correlates to slower speeds... .
Yes, thanks for reminding me of that. I was confusing propeller diameter with pitch. Flite Test sent me two sizes of propellers, 10 inch (the one shown in the image I posted) and 9 inch. Both have a 4.5 pitch.

Would it make sense to use the nine-inch prop instead of the ten-inch one?



Slow, low and dirty.
On a smaller plane I would. I use a 9" on the Cub and it works fine but I'd get more out of a 10". How much power you get from a prop really depends on the motor and battery specs. For a particular kv rating of a motor you will usually see thrust numbers that best match the appropriate prop (based on RPM and available torque). Basically, the higher voltage you run through a motor the faster it spins the better a smaller prop works. So if you have a choice between a 9x4.5 or a 10x4.5 and you're getting the same RPM (or close to), the 10" prop provides more power. On the same motor running a 4s pack with a 10x4.5 would likely burn the motor up while an 8x4.5 would be okay (due to the higher rpm offsetting the lower required torque). You can always use less prop, never more.