On Tuesday, July 17, 2007, at 04:40 PM, glenn crowder wrote:
> Oooooh - that sounds good!- Hi Fred, have you heard anything back
---From
> Paul Lipps or
> are you just going to wait and see what Vari Prop comes up with?
> -
> ------------------------
-------------------------
--Glenn
Glenn, Jeff,
I'll try to briefly recap my communications w/ Paul Lipps vis a vis a
prop for the Europa. My interest was piqued a while back by Mike
Gregory's post referring to an article on Elippse props at:
www.batterson.net/EAA499/Issue77_8-13.pdf
(If anyone wants to read more of what Paul has to say about props and
can digest the esoteric technical issues of prop design, go to:
www.vansairforce.com/community/printthread.php?t=18593 and scroll down
to "elippse".)
(For background on my correspondence w/ Lipps, see my europa-list post
of May 29, 2007.)
I emailed Paul and he's interested in designing something for us; here
is the last email from him:
> From: "Paul Lipps" <elippse@sbcglobal.net>
> Date: Sat Jun 16, 2007 9:21:36 AM US/Pacific
> To: "Fred Klein" <fklein@orcasonline.com>
> Subject: Re: prop for Europa
>
> Hello, Fred!
> The apologies should be mine for not getting back to you sooner
than
> this. I've been caught up in a flurry of activity designing a couple
of
> props for biplane guys, plus working on the EFI I designed for Klaus
> Savier.
> Now to try to answer your questions. To get a good estimate of the
> plane's
> equivalent parasite drag area, I need to have accurate speed and
> thrust of
> the plane in level flight. Thrust is obtained from the engine power
> and the
> prop efficiency. I have to have a model of the prop to see how it
> converts
> engine power into thrust during the test period, which I don't have
> for the
> Airmaster. But even though the Great American isn't the best, I do
> have a
> good model of it in my equations. As far as Glenn's plane is
> concerned, if I
> can get the engine power and if his cowling and cooling system drag is
> not
> much different from the other Europas, that shouldn't be a problem. As
> far
> as cruise and climb efficiency is concerned, the three-blade prop on
my
> 125HP Lancair shows about 82% efficiency in a climb and about 90% in
> cruise.
> This climb efficiency is probably better that most FP props are in
> cruise.
> BUT, my blade design has low static and low-speed thrust, so that the
> initial run up to 45-55 mph is much slower, than on a 200 mph prop. On
> a
> prop for a slower plane, with lower pitch, that might be to 30-40 mph.
> But
> it will take a longer takeoff run, maybe as much as 50%. But once you
> get
> past this blade stall region, as Tom Aberle puts it, it's like it has
> cut in
> the afterburner. My compensation would be a royalty paid by the prop
> maker
> on subsequent prop sales. Larry Morgan of Vari-Prop has entered into
an
> agreement with me for the design of blades for his CS and GA prop
> hubs. He
> will be showing the three-blade RV prop at Golden West at the end of
> this
> month and at Oshkosh. (Can't get myself to write that strange name
> they've
> come up with for the EAA event at Oshkosh!) I'm sure he would be
> interested
> in the Europa market. lmorgan724@yahoo.com, 503 804 5508. Again,
please
> forgive me for my lack of promptness for this reply. Paul
I haven't moved this forward for several reasons. First, before his
ref. to Vari-Prop above, my focus was on FP props and for reasons
described in my May 29 europa-list post, it turned out to be not so
simple to get a FP prop of Paul's design on a Rotax hub. Second, in my
dreams, I've been wondering if there might be a way to get a Lipps
blade working in conjunction w/ an Airmaster CS hub since so many
Europa flyers have them. Then came the rumors of the
Airmaster/Sensenich combination. So I've sort of been waiting for the
dust tosettle...
personally, I'm still trying to get my CM bonded in, so what business
do I have pushing on optimal propellers?
So to sum up, for Lipps to design something specific to the Europa, we
need to get someone to bolt on Paul's Great American prop (w/ an SAE 1
bolt circle) and generate some flight test data. Alternatively, what
Paul's developing for Vari Prop may be just the ticket. I'm happy to be
the point man between Lipps and our Europas, but the ball's in the air
and anyone can catch it and run with it. My apologies for the long
post, but I've referenced other documents to keep it as short as
possible.
Fred
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