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Nelson performance - 7/25/2006 7:06:29 AM   
smitty9969


 

Posts: 85
Joined: 8/10/2004
From: APO, AE, USA
Status: offline 		Fella's
Got a question about RPM's.
Nelson turning 21.4.. 95 degress outside w/ 85% humidity. Sea level (matter of fact, the gulf is about 400 yds away). Prop CF 7.4 x 8 (standard APC Q-40 prop). Plug burning a nice color brown after run.
Is this the performance I should expect under these conditions?

Smitty
       Post #: 1

RE: Nelson performance - 7/25/2006 11:33:25 AM   
luv to race


 

Posts: 465
Joined: 12/10/2002
From: Liquored, FL,
Status: offline 		Not good. You wrote the 7.4 x 8 ?? If that prop is truely the 8, and not the 8.0..? then that 8 should turn close or over 24K...easily. If your "8", is actually an 8.0... then it would depend on what version 8.0 you have. I know that sounds confusing, but APC hasn't made the prop stamped with 7.4 x 8 in many years. They all read 7.4 x 8.0 ....

If a Q40 engine only turns 21.4, you shouldn't fly it. It will just burn itself up. Don't fly unless that tach reads 23K, on the pinch up.

RB

(in reply to smitty9969)
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RE: Nelson performance - 7/25/2006 2:24:57 PM   
daven



Posts: 6909
Joined: 12/7/2001
From: Andover, MN, USA
Status: offline 		No that is not good.

The APC Carbon props are confusing as Randy pointed out.

Not only are their different versions:

Version 1 labeled 7.4x8
Version 2 labeled 7.4x8.0
Version 3 also labeled 7.4x8.0 but has slight witness marks around outside edge of prop
Version 4 also labeled 7.4x8.0 but made out of a slightly different material.

But the pitch tends to vary slightly from prop to prop. I like to put my CF props on a pitch gauge and check them at station 7, its also a good idea to check both blades because they can vary slightly from side to side.

Back to your original question, you need to turn more rpms. If that prop isn't doing it, trim 1/8" off each tip, balance, and retune. You should be getting 22.5 - 23k on the pinch, you need a smaller prop.

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RE: Nelson performance - 7/25/2006 5:43:00 PM   
garys


 

Posts: 756
Joined: 1/31/2002
From: San Diego, CA, USA
Status: offline 		Version 4?? I must be out of it...when/where did that come from?

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GS

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RE: Nelson performance - 7/25/2006 5:44:38 PM   
diggs_74



Posts: 1281
Joined: 1/20/2004
From: Emerald, WI, USA
Status: offline 		I was wondering the same thing Gary.. It's as bad as trying to keep up with Microsoft


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Lee LaValley
NMPRA# 33w

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RE: Nelson performance - 7/25/2006 6:31:52 PM   
daven



Posts: 6909
Joined: 12/7/2001
From: Andover, MN, USA
Status: offline 		Yep, there is a new version out. You can see the difference between a Version 3 and 4 by looking at the hole in the front of the prop. On a version 3 you have about a 1/8" step before the diameter of the inner hole changes. On the version 4, the step is only about a 1/16". I believe the material was also changed.

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RE: Nelson performance - 7/25/2006 6:38:34 PM   
garys


 

Posts: 756
Joined: 1/31/2002
From: San Diego, CA, USA
Status: offline 		Interesting...when did it come out? Are the others available? I guess I haven't paid much attention since I've been running the 7.4x7.8 since Phoenix.

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GS

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RE: Nelson performance - 7/25/2006 7:10:49 PM   
diggs_74



Posts: 1281
Joined: 1/20/2004
From: Emerald, WI, USA
Status: offline 		I haven't had a chance to try one of those 7.8... How are they working for you?? I have a couple, just haven't put one on yet.


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Lee LaValley
NMPRA# 33w

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RE: Nelson performance - 7/25/2006 7:43:36 PM   
garys


 

Posts: 756
Joined: 1/31/2002
From: San Diego, CA, USA
Status: offline 		The 7.8's have been working great for me. At Phoenix, Jim Allen and Dave Shadel had both tried them and said they felt they were faster than the 8.0, so I bolted one on Friday morning, flew one test flight, it seemed fast, so I went to the NHRA drag races. Other than a few heats at a Basin race where I played with a couple wood props, I've only been running the 7.8.

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GS

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RE: Nelson performance - 7/25/2006 7:48:35 PM   
daven



Posts: 6909
Joined: 12/7/2001
From: Andover, MN, USA
Status: offline 		I heard about them in Muncie from Darrol. I think he had some of each.

7.8 works good, better than the 8 in my opinion.

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RE: Nelson performance - 7/25/2006 8:05:02 PM   
diggs_74



Posts: 1281
Joined: 1/20/2004
From: Emerald, WI, USA
Status: offline 		Well, I guess I'll have to throw one on for the race this weekend.. Hopefully the old Dago can handle the extra speed


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Lee LaValley
NMPRA# 33w

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RE: Nelson performance - 7/25/2006 9:44:17 PM   
smitty9969


 

Posts: 85
Joined: 8/10/2004
From: APO, AE, USA
Status: offline 		Thanks Fella's. I didnt do the pinch test. Just tached it before take off. I'll trim the props down to that 1/8.. I also have some 7.8. I'll run those and check the differences.
Again, thanks for the help..

Smitty

(in reply to diggs_74)
       Post #: 12

RE: Nelson performance - 7/25/2006 10:28:11 PM   
daven



Posts: 6909
Joined: 12/7/2001
From: Andover, MN, USA
Status: offline 		Are you sure the engine was fully up on the pipe? There are a couple stages, its tough to know for sure unless you pinch the line slightly.

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RE: Nelson performance - 7/26/2006 5:39:08 AM   
smitty9969


 

Posts: 85
Joined: 8/10/2004
From: APO, AE, USA
Status: offline 		Positive,
Plane flew great. Good speed. Engine unloaded nicely in the air. Especially coming off of pylon 1. Love that sound. Reason why I'm asking because the engine was brought used. And the air is so heavy here with the humidity.
Next question, I thought you couldn't modify a prop if your at a race. Could I enter a sanctioned event with a prop clipped?
Just a thought, maybe I'm not gettin the rpm's on the ground because I didn't pinch, so it's not coming up fully on the pipe until it's airborne and unloads.

Smitty

(in reply to daven)
       Post #: 14

RE: Nelson performance - 7/26/2006 1:04:36 PM   
daven



Posts: 6909
Joined: 12/7/2001
From: Andover, MN, USA
Status: offline 		No you could not enter a contest with a clipped prop. No modifications are allowed to the black props, that is why I check the pitch of them and mark them accordingly.

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Dave Norman

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RE: Nelson performance - 7/27/2006 5:23:09 AM   
smitty9969