Prop Diameter

[mcguif0a]

I read in eaa magazies about prop diameters but I would like to hear what the KF county is using for size on their projects. I know I need a minimum of 9 inches clearance from prop tip to the deck when the plane sit level but thats the extent of my knowledge.
Tyler

[n85ae]

I have a fairly flat pitched 74" on my Series 5 with my IO-240B I have
had four props on mine. Original a warp drive, then a 72" Sensenich,
this I trimmed to a 70.5, which worked very well. I then changed to
the 74" which gives me a bit better acceleration at takeoff, and a bit
better climb. Cruise and top speed have been virtually the same with
all the props. Which at least to my simple mind tells me that at about
120+ mph drag with the fox starts increasing so much that prop doesn't
make much difference if you have the hp. Drag becomes more the
problem.

My Perf is pretty consistent, and I fly mostly solo, with minor variation
I have had pretty much the following perf with all four props:

Takeoff distance around 150-200 feet
1200-1700 fpm rate of climb (temperature depending)
140 mph top speed in level flight (2800 rpm).
125 mph cruise (2200 rpm)

My Dad has a PhD in Aero Engineering, and owns an aerospace company.
http://www.michiganaerospace.com he simply looks at the plane
and says "forget about drag reduction that plane is hopeless, you need
a new plane". He did tell me the lift struts were worth airfoiling, which I
did. I think that helps but I have never flown without so I have no
benchmark of comparison.

Regards,
Jeff Hays
Series 5, IO-240B

[darinh]

I run a 70" Airmaster (3-blade) prop on my Series 7 / 914 combo. This prop is an electric constant speed not just in-flight adjustable and it works like a charm....a bit on the spendy side but to really take advantage of the 914, you really need a true CS prop in my opinion.

[mcguif0a]

Well I am now looking at a 71" Prince P-Tip prop. Has anyone had experience with them?
I wish I could do a constant speed prop but that is not in the cards right now. Maybe in later years as an upgrade.

[N14ND]

I have a Prince Q-tip Prop for my Kitfox. I have a 0-200. Don't have any performance feedback for it since the aircraft is still under construction. I can say that the company is very good and will bend over backward to make sure your satisfied. Even to the point of making a new prop. I had mine redone when I switched from Lycoming prop flange to the Continental. Just charged me shipping. Also, a very light prop. I'm not at home or I'd give you the specifics off of it. I know that you give them the diameter, horsepower, max rpm and estimated maximum speed and they design the blade profile and pitch for the performance you want. Plus the Q-tip and leading edge reinforcement as options.

[Dave S]

Tyler,

We have a KF 7 trigear with the 70" Warp Drive tapered tip. The prop is set to a cruise pitch.

I think I measured the ground clearance once and determined that I had all I would ever need.

The 912 ULS has a 2.43 gearbox so the 5200 RPM I normally cruise at results in a prop RPM of 2140, if my math is not too screwy. 5400 RPM will give a prop RPM of a bit over 2200 RPM - at any rate, probably not breaking any sound barriers with the prop tips (or with any any other parts)

Sincerely,

Dave S
KF 7 Trigear
912 ULS Warp Drive

[Slyfox]

I have the 912uls, the prop is an IVO medium 70". I love this prop. Did I mention, I love this prop. I set it all the way flat, hit the throttle and it goes up with over 1500fpm until I pull it over the top. Now I can run just off the ground, after take off, until I get to around 70mph and than pull up and she will do around 2000fpm until I pull her over the top. Very fun. In cruise I hit the button until I get 5500rpm. Will cruise there all day at 120+ mph. I love my prop. I have no stops on the prop, right out of the box and on the plane.