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  #1  
Old 09-05-2013, 05:55 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 6,657
Default Hartzell Composite Blade Clearance - help!

The wide cord on the Hartzell composite blade results in an issue. It appears that in the low pitch mode (10deg) that the back side of the blade is 7/8" from the front of the SJ cowl. The high pitch is 27.5deg and the cord at this point is 8 inches. By calculation, going to high pitch will move the back side of that blade 1.15". Soooo, I need to create some clearance, and it may get worse with the inlet rings installed.

Options:
1. cut the cowl just behind the spinner and move everything back .6 inches.
(my favorite)

2. somehow move the cooling inlets back .6 inches.

3. extend the spinner .6 and move the entire cowl back, yes 0.6 inches.

4. Other??

What have others done to address this issue?
BTW- I have the 2.5 in extension to reduce cowl interference possibilities.
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  #2  
Old 09-05-2013, 06:53 PM
BobTurner BobTurner is offline
 
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Location: Livermore, CA
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Default

Use some air pressure to move the blades to coarse pitch and physically check. Doing the numbers in my head I get about the same answer (a little over an inch) but this movement will be in an arc, partly aft and partly down.
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  #3  
Old 09-05-2013, 07:11 PM
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I recall seeing something about Hartzell limiting the low pitch stop to prevent this. I would check with them first.
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  #4  
Old 09-05-2013, 07:21 PM
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Default

Bill.
Is the cowl top fit????

Do that first.
The rings won't go farther than the cowl fiberglass .

You can adjust the clearance between the spinner and cowl.

What I see in the pick the cowl needs to go down .25 to .50 for engine sag.
That will move it back a little.

Hope it helps.

Boomer
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  #5  
Old 09-05-2013, 07:56 PM
BillL BillL is offline
 
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Location: Central IL
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Quote:
Originally Posted by BobTurner View Post
Use some air pressure to move the blades to coarse pitch and physically check. Doing the numbers in my head I get about the same answer (a little over an inch) but this movement will be in an arc, partly aft and partly down.
Bob, I was going to make a handle and twist them, but I like the air pressure idea, do I just pressurize where the oil line goes to the front of the crankcase?

Quote:
Originally Posted by Walt View Post
I recall seeing something about Hartzell limiting the low pitch stop to prevent this. I would check with them first.
Yes, Walt, I will contact them, but heard that this was not a recommended permanent fix. I don't know why.
ref: http://www.vansairforce.com/communit...t=51841&page=2

Quote:
Originally Posted by Bruce View Post
Bill.
Is the cowl top fit????

Do that first.
The rings won't go farther than the cowl fiberglass .

You can adjust the clearance between the spinner and cowl.

What I see in the pick the cowl needs to go down .25 to .50 for engine sag.
That will move it back a little.

Hope it helps.

Boomer
Boomer, No, the cowl is just sitting there about with a 1/4" gap from the spinner. Glad to hear the rings won't protrude more. The 1.15" is the horizontal component of travel, so with 1/4" clearance at full pitch, then I still need .6, maybe I can squeak some here and there to reduce it. I could add a 1/4" to the flat behind the spinner, too. Maybe the axis of rotation is not in the center of the cord.

The cowl fitting is next as i want to rivet the Skybolt tabs down the side of the fuse with the engine off. With many of these just supplied by Hartzell to the aerobatic team, I hoped to get some information on their solutions too. Per postings, they did limit the travel on some.
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Last edited by BillL : 09-05-2013 at 08:05 PM. Reason: added reference link
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  #6  
Old 09-05-2013, 08:45 PM
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DanH DanH is offline
 
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If you elect to mod the cowl, it will be easy to move the cowl rearward and extend the section behind the spinner.
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  #7  
Old 09-06-2013, 10:40 AM
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RV8Squaz RV8Squaz is offline
 
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Location: Senoia, Georgia
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Move the cowl back and leave the spinner alone. I see so many people struggle getting the cowl off and on during maintenance because they only have 1/8" or 1/4" space between the spinner and the cowl. Give yourself about 1/2" and it will make life a lot easier in the long run. The T-6 Texan II I used to fly had more than an inch!

Jerry
RV-8 N84JE
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