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Old 06-20-2011, 09:57 AM
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smokyray smokyray is offline
 
Join Date: Jan 2005
Location: TX32
Posts: 1,907
Default No weapon too short for a brave man...

Morten,
My rule of thumb on RV4 props (having tested five on my short gear RV4) was 69" maximum length for short gear, 72" for the long gear. A friend had a 72" Hartzell and 180HP on his short gear 4. I flew it primarily flying off my turf strip and several gravel runways. I noticed over time the Hartzell getting "greener" at the tips. This was after extended grass operations and I also noticed small chips in the leading edge from gravel at the annual. I was very careful not to run it up stationary over gravel greater than 1200 RPM and used backcountry techniques for takeoff, landings and run ups. This isn't a show stopper but it is important to note. If you fly primarily off prepared surfaces, you shouldn't have any problems. You do need to be aware of the tip clearance in 2 point attitude as you mentioned.

I'm not by any means condemning the use of the 72" on short gear, just be advised. I wouldn't shorten an existing prop, and Van's agrees with that logic in the RV4 builders manual. I would sell it and buy a new one if you are concerned. Personally the MT 2 blade C/S propeller Steve has on his blog above is hard to beat for weight and smoothness. Martin Albrecht at MT is a good guy and performs excellent engineering on a case by case basis. Send him an email, you might like what he has to say. I have had very positive success with MT FP props myself. The MT your friend has is a decent price for a 3 blade, Van's has the 2 blade MT on their site for $8250 delivered, MT might work something out since Norway is closer...

Smokey

Martin.Albrecht@mt-propeller.com

Last edited by smokyray : 06-20-2011 at 10:09 AM.
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