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1. 07:28 PM - Prince P-tip propeller (Benjamin Q)
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| Subject: | Prince P-tip propeller |
I am going to put a Jabiru 2200 on my 701. I have been looking into using a Prince
P-tip propeller. Supposedly the p-tip allows a blade of smaller diameter
to be as effective as a larger propeller because the tips "delays the tip vorticies
which cause drag and turbulence within the propeller arc." They also claim
that "a 72" diameter propeller without a P-TIP will give a volume of air
from the propeller of approximately 68" in diameter; a P-TIP propeller will provide
72" of air volume."
Additionally the propellers are said to include automatic pitch changing.
"The propeller has a fixed pitch that relies on the forward pull of the propeller
to automatically provide pitch change proportional to the amount of force
being applied to the propeller disk."
I have looked for information on some of the forums and the few that have the
propeller seem to think that they give modest increases in performance and efficiency.
The reason I am so interested in these propellers is because it seems like they
might be something of a silver bullet for some of the weaknesses you find
in the Jabiru. The Jabiru has to use a smaller prop because they spin up to 3300
rpms. You are limited to a 68" prop instead of the 72" prop you would usually
find on a Rotax. Conveniently, 68" to 72" is the difference Prince claims
for their props. Additionally the automatic pitch changing could help with
the slightly weaker climb and takeoff performance of the Jabiru as compared to
the Rotax. It's not that I think that the Jabiru will out perform the Rotax
with the P-tip Prop, but I think it will get closer then if I put on the wood
or ground adjustable composite sensenich that is packaged with Jabiru's Firewall
Forward kit.
I called Jabiru USA and talked to someone there and they didn't recommend the
Prince P-tip. Their reasons were cost and consistency. They said that they
got a few P-tip propellers one time and when they were put on the same engine,
there was a slight difference in the max rpms in each propeller. I think they
said about a 20 rpm difference, but I might be remembering that wrong.
Anyway as far as cost, I'm not sure thats and issue either. The cost of the
p-tip is actually less then the composite ground adjustable sensenich. I'm not
entirely sure the consistency argument is that strong either. The propellers
are individually made in order to be application specific, so you can expect
there to be at least a slight difference in each propeller.
I also called Prince Aircraft Company and talked to Lonnie Prince, the owner
of the company. He told me that if I got the propeller and it wasn't performing
like I thought it should, he would take it back and tweak it at the factory
for free. The research I have done on the company seems good. They have been
around for a while and have a pretty diverse business. Lonnie was a super
nice guy, but as an engineer, I really wish that he had some hard core dynamic
flow analysis, or experimental data I could take a look at. Realistically, I
don't think Zenith has done hardcore dynamic flow analysis either. More of
a wish on my part, not a criticism.
I have heard that a few 601s have Prince P-tips with good results, but that's a little different in application. Has anyone tried a P-tip on a slower STOL Airplane? Has anyone else looked into this? Even with the non-recommendation from Jabiru, I am still leaning toward the P-tip. Professionally, I appreciate the way the design takes advantage of innovative engineering to turn out a unique solution. If anyone wants to take a look at the website its http://www.princeaircraft.com/TheProp.aspx
I would appreciate any comments you guys have. Even though I have only had my
kit for a month, I am already done with my rudder, horizontal stabilizer, elevator,
slats and flaperons. I have two weeks of leave coming up and I hope to
be through the wings and into the fuselage. Its amazing how much you can get
done in a 12 hour day. The propellers have a 13 week lead time, so if this
is the direction I am going, I need to do it soon, otherwise I'll be have a finished
airplane in my garage waiting for a propeller.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=243102#243102
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