Model IV prop size and ground clearance.

[rwaltman]

I exchanged a few emails with Powerfin, on the possibility of using a two-blade propeller on my KF. (After the current problems are ironed out)
They recommend at least a 67" prop sacrificing some climb performance, 70" for a good climb/cruise balance.
I doubt I can accommodate a 70" prop without installing larger tires and/or reversing the HKS reduction unit from bottom to top layouts. (And I’d rather do neither.)
Until I get to the airport and take some measurements - What is the maximum prop size for a vanilla Model IV that still gives a good/safe ground clearance?
I will be operating from both paved and grass runways, but not from unprepared fields.

Thanks,

Roberto.

[rwaltman]

Forgot to mention. In the current setup, the hub axis is just above the classical round cowlings joint line. ( http://www.teamkitfox.com/Forums/alb...pictureid=1476 )

Roberto.

[Slyfox]

what engine

[rwaltman]

HKS-700E
60HP at 6200 Max RPM (take-off, 3 minutes max)
56HP continuous at 5800 RPM
2.58:1 reduction unit.

[Geowitz]

I've got a model IV with the grove gear and 6x600 tires as you have probably already noticed. My thrust line is the same as the 912 with the smooth cowling. Round cowling is the same as well(about 16.5 inches above the bottom of the fuse). I've got a 72 inch IVO on there now which, if I remember correctly, gives me about 9 inches of clearance in level attitude. Certified requirements are 9 inches for taildraggers - See FAR Sec. 25.925

[rwaltman]

Checked - 11" clearance with the 64" prop, in flying attitude.
Could go to a 68" keeping 9" clearance.
Will think about it after the current crop of problems is solved.

Roberto.

[cainbird]

My 2 cents, large prop diameter is everything on these planes. I am running a 72 in IVO on my 912.

Cain B