Nick and Dan,
My 320 had the F8468D prop and I
will have to say that it was a very efficient prop. It always ran very well
along side all my friends with 360 motors. Back in November my nose gear
dipped into a pot hole and I had a prop strike. As a result I ended up
upgrading to a 360 and to a new blade design. The blade I am using now is a
F7694 with a D twist. It was a SR-20 blade that I had twisted for the higher
speeds of the Lancair. The combination added apx 12 kts. It doesn’t feel like
it climbs as well but it sure scoots on the level. While waiting for my motor
I did some research and was able to get the engineers of Hartzell to give me
some calculations on the various props for comparison purposes. Note that they
did not want the F8468D used on a 360. As you can see it was the best blade. The
blade I went with however is not on this list. The blade they favor is the
F7497D. It has very recently been approved by them for use on the Lancair 360.
You will see it on the Lancair website too.
These calculations below were
provided to me from Hartzell.
7497-2, 199 lbs
thrust, 84.6%
7497D-2, 206 lbs thrust,
87.8%
7666-4, 191 lbs thrust, 81.3%
7068-2, 206 lbs thrust 87.8%
8468D-14, 208 lbs, 88.5% 320 motors
only
At 4500 ft 75 degrees 2700 rpm I
am getting 215 kts true with the new 360 motor and prop. The old 320 did about
203 under similar circumstances.
Blue Skies,
Craig Schulze
Lancair N73S
From: Nick Long
[mailto:nick@beaglepup.info]
Sent: Tuesday, June 18, 2013 2:00 PM
To: lml@lancaironline.net
Subject: Re: [LML] Re: Propeller choice for Lancair 320 and Back Plate
failures
That’s all useful
info. At first, one would be tempted to say that 3-4 knots is not significant,
but if it is repeatable....
I remember years
ago some of us wondering why one aircraft was faster than another and swapping
supposedly identical props between supposedly identical aircraft, then flying
in formation and finding one prop was always 3 or 4 knots better.
Sent: Tuesday,
June 18, 2013 6:47 PM
Subject: [LML]
Re: Propeller choice for Lancair 320 and Back Plate failures
Nick,
I’ve got a Lancair 320 with the
IO-320-D1B 160hp engine and the Hartzell 70” prop that Lancair and Hartzell
approved for this airframe and engine. I’m very pleased with the
performance. A friend of mine has the same airframe and engine as I do
but has the MT 3-blade prop. When we fly formation at exactly the same
power settings, I am pulling away from him at about 3-4kts. We haven’t
tried a side-by-side climb comparison but the 2-blade Hartzell is definitely a
bit faster in cruise than the 3-blade Hartzell, just as prop theory would suggest.
When I built the plane I was
concerned about spinner wobble and stresses, so I created a little donut inside
the spinner that fits snugly around the prop hub. You can see a photo of
it here: http://lancair.net/pix/olsen/olsen-construction.
After 720hrs on the airplane I have had no problems with spinner or cracking.
Cheers!
Dan Olsen
Fort Collins, CO
N320DK, 320 MKII, 720hrs
N630DK, IV-P, 20% complete