tkg

My Feedback: (1)

It got above freezing today so broke out the Laser 200 with the G20 in it to get it ready for spring.
Its only turning 8900 on a 16x8 APC and 9100 on a 17x6 APC.
Must be the altitude 5400 ft[]

Magna

whats wrong with you.????? Not happy with those nos? 8900 16x8 and 9100 17x6... Heck that is a lot more than those touted 26cc from china. You prolly can spin 17x8 at low/mid 8000.

karolh

Those sound like great numbers to me, as my well broken in EI G23 turns 9000 on a APC 16x8 and 9200 on a 17x6.

Karol

captinjohn

TKG: I bet you cannot wait to do some warm weather flying. Sounds like good RPM on that engine. Capt,n

tkg

My Feedback: (1)

I ran it with a smaller prop 15x8 APC, was hoping for 10K but only got 9650

pettit

My Feedback: (23)

Just because your prop is turning at a high RPM, it doesn't mean it's really doing anything productive.

I just plugged in your RPM numbers into ThrustHP and got the following:

15-8 @ 9650 14.14 lbs of thrust 73 MPH
16-8 @ 8900 15.57 lbs of thrust 67 MPH
16-6 @ 9100 20.75 lbs of thrust 51 MPH

Higher speed, lower thrust, takes longer to get to speed.

I'd say your numbers looked right on the money.

karolh

I think you figures are a bit of wishful thinking. Using Pe thrust chart which has been proven to give fairly accurate figures, and inputting TKG's altitude of 5400 ft. and your prop / rpm data based on a APC props, IMHO provides a more realistic set of numbers.

15x8 @ 9600 11.58 lbs. of thrust 63.5 mph
16x8 @ 8900 12.26 lbs. of thrust 58.6 mph
16x6 @ 9100 10.78 lbs. of thrust 44.9 mph.

Karol

pettit

My Feedback: (23)

I was just showing him that the numbers he got were pretty good for that engine.

To do a more accurate test, you have to try a lot of props and do a lot of flying.

Thrust and speed simulators, no matter who wrote them, are pretty good for showing differences between props, RPM, etc.

But that's about all....

tkg

My Feedback: (1)

I fly the plane on the 17x6 @9100... The other props are the left overs from the find the right prop for the plane game...
I don't quite know the reason for the large diff between the 16x8 and the 17x6 should be closer in RPM, but I rechecked and the 17 is about 300 rpm faster.
And WAASSUp is dis

datafry

What prop did you end up using? I currently have the same setup but have a 15X8 on there now, but was thinking about 17x6 myself

tkg

My Feedback: (1)

I ended up with the 17x6. It gave a more constant speed upline vs down line.
If it was in the 80's and everybody was flying "rocket ship" pattern then the 16x8 and pipe would have been the ticket

datafry

Thx, I'll try out a 17x6 next time out (hopefully tomorrow)

Cheers
KR