VAF Forums

VAF Forums (https://vansairforce.net/community/index.php)
-   Propellers (https://vansairforce.net/community/forumdisplay.php?f=19)
-   -   Hartzell Composite Blade Clearance - help! (https://vansairforce.net/community/showthread.php?t=103993)

BillL 09-05-2013 05:55 PM

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.

BobTurner 09-05-2013 06:53 PM

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.

Walt 09-05-2013 07:11 PM

I recall seeing something about Hartzell limiting the low pitch stop to prevent this. I would check with them first.

Bruce 09-05-2013 07:21 PM

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

BillL 09-05-2013 07:56 PM

Quote:

Originally Posted by BobTurner (Post 804882)
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 (Post 804892)
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 (Post 804897)
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.

DanH 09-05-2013 08:45 PM

If you elect to mod the cowl, it will be easy to move the cowl rearward and extend the section behind the spinner.

hydroguy2 09-05-2013 08:52 PM

Quote:

Originally Posted by DanH (Post 804921)
If you elect to mod the cowl, it will be easy to move the cowl rearward and extend the section behind the spinner.

gets my vote. get the correct clearance at the inlets, then moving the spinner flange forward will be the easiest fix.

Andy Hill 09-06-2013 01:36 AM

  1. Ensure the Prop has been setup for "RVs" by Hartzell / Prop Shop i.e. limiting the Coarse Pitch Stop
  2. Certainly with us, Hartzell made sure we had the "standard (Vans) cowl"
  3. The "problem" area is RHS mainly, at the furthest outboard point of the cowl. Is the SJ cowl "wider" at the OB point (as well as further forward?)

tadsargent 09-06-2013 05:45 AM

Bill, you have made the best choice for a propeller. At this stage in the process you have many options to get the spacing needed.

1. Shimm the spinner back place the maximum amount aft prior to cutting your cowl.
2. Trim for clearence on the right edge of the cowl if needed.
3. Have a friend help you twist the blade when mounted on the engine,
You neede a minimum of 3/8 twisted with 1/2 " to be optimum.
4. Some one suggested a lower pitch stop, I would not recommend this, you actuall want more pitch here.

Our team just partnered with Hartzell installed these props on all of our planes, they are fantastic

RV8Squaz 09-06-2013 10:40 AM

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


All times are GMT -6. The time now is 02:58 PM.