dpomaro

Need some help on this Noob issue...
Which propeller size will better fit for stol features? More pitch and less size / or less pitch and + size?


It is for a DLE 20cc on a stol airplane....


I'm using a xoar 17x7, but I think that changing the prop size will enhance the stol characteristics.

Thanks for any advice...

av8tor1977

My Feedback: (6)

Large diameter-low pitch = the highest static thrust. (Two bladed prop is best.)

Try an 18 x 4 if you can find one, but it will be slow in flight.

AV8TOR

MajorTomski

What ava8tor said is true, but the problem with 'max static thrust' it may not be enough dynamic thrust to allow the airplane to fly well. You'll just have to run a range of props and find the one that gives you the best combination of short take off and nice cruise speed.

av8tor1977

My Feedback: (6)

Yes, I am thinking an 18 x 6 would end up being the best choice in this case, except that is a bit too large for a 20cc engine. You might try an 16 x 6 or 17 x 6. As I mentioned, an 18 x 4 would provide the most static thrust, but the airplane will need to fly at high throttle settings to give adequate flight speed. 8000 rpms with an 18 x 4 would give a theoretical air speed of only 30 mph. Not much margin over the probable stall speed....

AV8TOR

ahicks

My Feedback: (2)

I don't know what kind of weight you're playing with, but I can tell you a 17x6 on something weighing 10 - 10.5 lbs or less is going to have pretty decent, if not unlimited, vertical.

It's one of the 2 most popular 20cc props, with the other being a 16x8. That prop is used on a cleaner airframe, with more airspeed. It's till got pretty decent vertical, but not like the 17x6.

Either prop will get most 20cc planes off the ground in pretty short order.