flyrotary@lancaironline.net Mailing List Archive

Hi james

Yes I would have to agree, 0% slip I would guess is no attainable I think from memory around the 3% is the norm but hopefully someone else with more experience on prop design might have a better ideah! the testing I did was at 8000 da so I would assume the higher you go the less dense air the more slippage, but I could be wrong , I must admit ia don't have a good grasp on prop efficiencys as yet, mor trial and error!

Cheers

Christian

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On 24 Jul 2014, at 11:14 am, "Patrick Panzera" <flyrotary@lancaironline.net> wrote:

I wonder how much slip a helicopter has? ;)

On Wed, Jul 23, 2014 at 5:45 PM, James Osborn <flyrotary@lancaironline.net> wrote:

I don't know jack about slippage, but I think it is the percentage difference between actual distance traveled and theoretical distance traveled if your propeller corkscrewed through the air with no thrust. I found a prop slip calculator online and for 86 inch pitch, 2.85 gear ratio, 7000 rpm, 180 mph, I get 10% slip. Granted the calculator was for boat propellers, but I don't think it matters as long as the units are correct. There has to be some slip because there would be no thrust otherwise. So what is considered a reasonable or good amount of slip? Using Bill's numbers 86 inch pitch, 2.85 gear ratio, 7000 rpm, 200 mph, I get 0% slip. That can't be right!

On Fri, Jul 4, 2014 at 7:19 AM, Bill Bradburry <flyrotary@lancaironline.net> wrote:

Christian,

It seems that you have a lot of prop slippage at cruise. I think that at
that prop rpm you should be getting 200mph if you had no slippage.

Bill

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Thursday, July 03, 2014 4:01 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Rv7 renises p port

Well hi all
Just thought I'd throw out there the mods I,ve done to the renises in an
rv7'.
Well the p ported engine is now back in the plane and running well, over the
standard short manifold that was originally in the plane I have gained
around 400 static rpm, same prop and gearbox combo, 2.85 ratio, this equates
to allot more hp at takeoff, just shy of 2300 prop rpm, I'm running a prince
p tip prop at 68" x 86" pitch,
At 8000 ft it is turning 7000 at 180 mph tas which is an improvement of 25
mph on previous tests, . So next plan is bigger prop and less pitch to let
it rev to 7500 in strait and level.

Cheers
Christian
Rv7 renises Aus

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