Notices
O.S. Engines Support Ask Bill Baxter your questions about O.S. Engines.

OS .91 II Surpass- 3-blade prop??

Old 11-20-2006, 01:29 PM
  #1  
Big Daddy-RCU
Senior Member
Thread Starter
My Feedback: (5)
 
Join Date: Nov 2002
Location: berlin, NJ
Posts: 312
Likes: 0
Received 0 Likes on 0 Posts
Default OS .91 II Surpass- 3-blade prop??

*Hi, Whats a very good 3-Blade prop for a Newer OS 91 II Surpass engine??
*The .91 Surpass and 3-prop will be in a 9-pound Warbird.
*What would be the biggest 3-blade prop I can use on this OS .91 II Surpass??
Thanks.
Old 11-20-2006, 03:41 PM
  #2  
Stickbuilder
 
Stickbuilder's Avatar
 
Join Date: Nov 2005
Location: Leesburg, FL
Posts: 8,678
Likes: 0
Received 4 Likes on 4 Posts
Default RE: OS .91 II Surpass- 3-blade prop??

I tried a 12X7 from Master Airscrew in a P-47 with the new 91 Surpass II. The RPM was acceptable, but the model was just plain sluggish. Give it a try, if you wish, but I found that the model was much more responsive with a conventional 14X6 two blade.

Bill, AMA 4720
WACO Brotherhood #1
Old 11-20-2006, 09:09 PM
  #3  
Big Daddy-RCU
Senior Member
Thread Starter
My Feedback: (5)
 
Join Date: Nov 2002
Location: berlin, NJ
Posts: 312
Likes: 0
Received 0 Likes on 0 Posts
Default RE: OS .91 II Surpass- 3-blade prop??

Bax- what do you think??
Old 11-21-2006, 10:16 AM
  #4  
Bax
My Feedback: (11)
 
Join Date: Apr 2002
Location: Monticello, IL
Posts: 19,483
Likes: 0
Received 6 Likes on 5 Posts
Default RE: OS .91 II Surpass- 3-blade prop??

We always recommend a 2-blade propeller because they just work out better. There's no direct relationship between the size of a 2-blade prop and a 3-blade prop. Usually, though, people will go one inch smaller in diameter with the same pitch when going from a 2-blade to a 3-blade. The best thing, though, is to use a 2-blade prop for flying. After all, nobody can see what kind of prop you're using, and there are many, many props available to try out to see which flies the model the best. Not so with a 3-blade prop. Use the multi-bladed propeller for static display, and a 2-blade prop for flying.
Old 11-21-2006, 10:23 AM
  #5  
MinnFlyer
Senior Member
My Feedback: (4)
 
MinnFlyer's Avatar
 
Join Date: Apr 2002
Location: Willmar, MN
Posts: 28,519
Likes: 0
Received 8 Likes on 8 Posts
Default RE: OS .91 II Surpass- 3-blade prop??

I agree with Bax, but last year I flew the GP Seawind (Which needed the prop clearance) with a Graupner 12x7 3-blade, and the performance was outstanding.
Old 11-21-2006, 05:15 PM
  #6  
Big Daddy-RCU
Senior Member
Thread Starter
My Feedback: (5)
 
Join Date: Nov 2002
Location: berlin, NJ
Posts: 312
Likes: 0
Received 0 Likes on 0 Posts
Default RE: OS .91 II Surpass- 3-blade prop??

Thanks Bax.
But what would be a good 2-blade for the .91 Surpass II on a 9-lb. Warbird or what would be the biggest 2-blade I can use on this eng.??
Thanks.
Old 11-24-2006, 02:46 PM
  #7  
Bax
My Feedback: (11)
 
Join Date: Apr 2002
Location: Monticello, IL
Posts: 19,483
Likes: 0
Received 6 Likes on 5 Posts
Default RE: OS .91 II Surpass- 3-blade prop??

For an O.S. .91 Surpass II engine, we'd use an APC 12 x 10 or 13 x 8 to start with. You want to prop the engine to turn in the mid-to-high-9,000's, or even as high as 10,000 RPM when on the ground. Any prop that will turn that RPM when the engine's leaned to just rich of peak RPM and fly your model well is the 'correct' propeller.

You don't go for the "largest" prop, or the "coolest-looking" prop. You want one that gives you the performance you want. In your case, even a 14 x 8 or 7 may do the job, but remember to keep the RPM within the 9,000's and you'll do OK.
Old 11-24-2006, 08:15 PM
  #8  
Big Daddy-RCU
Senior Member
Thread Starter
My Feedback: (5)
 
Join Date: Nov 2002
Location: berlin, NJ
Posts: 312
Likes: 0
Received 0 Likes on 0 Posts
Default RE: OS .91 II Surpass- 3-blade prop??

"Thanks Bax" for your time and help.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.