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-   -   Whirl Wind HRT prop and standard Vans cowl (https://vansairforce.net/community/showthread.php?t=207612)

scsmith 06-29-2022 12:51 AM

Whirl Wind HRT prop and standard Vans cowl
 
I recently changed from the Whirl Wind 200RV prop to the Whirl Wind 72HRT prop. I have a standard Vans cowl.

The HRT blades are a fair bit wider, and the folks at Whirl Wind Aviation supplied a photo with dimensions showing the blade trailing edge location relative to the flywheel (ring gear holder) face, at full coarse pitch. I used their dimensions to make a tool to use as an indicator of where the blade would be.

I found that I needed to modify the cowling a little, on the right side cooling inlets. It looks like the blade would just barely contact the cowl there, and of course you want some clearance for engine mount movement too. I ground off about 1/4" at the worst place, not far from the outer edge of the cooling inlet, and re-contoured the inlet (after adding more glass to the back). I also had to trim the lip back on my induction air inlet. When I was done with the re-contouring, my tool showed that I have about 5/16" clearance to the blade everywhere.

Now, it is all back together and flying. With the prop in fine pitch, there is about 1-1/4" of clearance between the blade trailing edge and the cowl. The closest point is about midway out along the right cooling inlet lip. Of course there is no way to put the prop into full coarse pitch statically to verify the clearance. I am kinda worried that the prop could hit.

Anybody else have an 72HRT prop on an RV-8 with a Vans cowl? How much clearance do you have between the blade trailing edge and the cowl?

BobTurner 06-29-2022 01:32 AM

Quote:

Originally Posted by scsmith (Post 1616780)
Of course there is no way to put the prop into full coarse pitch statically to verify the clearance. ?

Remove the governor, use a rubber-tipped nozzle on your air compressor hose and use air pressure to move the blades to full coarse.

Lkitson 06-29-2022 06:55 AM

I have the same setup. I'll take some measurements when I go to the hangar tonight.

lr172 06-29-2022 07:29 AM

Quote:

Originally Posted by scsmith (Post 1616780)
I Of course there is no way to put the prop into full coarse pitch statically to verify the clearance. I am kinda worried that the prop could hit.
?

Are you sure about that? When I was shapping the spinner backplate block off plates, I used two 1x2 boards clamped on to the blade and pulled them into the coarse position. It is just a spring holding them in the fine position, albeit a pretty strong spring. Was trying to do it by hand without the boards and couldn't so called Hartzel and they laughed and said you need the boards for leverage and was the typical method for achieving what I was doing.

Can't speak to the WW, but expect the same.

Larry

scsmith 06-29-2022 10:57 AM

Quote:

Originally Posted by lr172 (Post 1616798)
Are you sure about that? When I was shapping the spinner backplate block off plates, I used two 1x2 boards clamped on to the blade and pulled them into the coarse position. It is just a spring holding them in the fine position, albeit a pretty strong spring. Was trying to do it by hand without the boards and couldn't so called Hartzel and they laughed and said you need the boards for leverage and was the typical method for achieving what I was doing.

Can't speak to the WW, but expect the same.

Larry

In principle, yes, enough leverage and one should be able to turn the blades. With aluminum blades, I would be comfortable doing that. With the light carbon composite blades, uhmmmm, rather not.

jclark 06-29-2022 11:37 AM

There is hope ...
 
Quote:

Originally Posted by scsmith (Post 1616780)
I recently changed from the Whirl Wind 200RV prop to the Whirl Wind 72HRT prop. I have a standard Vans cowl.

... <SNIP> ...

Of course, there is no way to put the prop into full coarse pitch statically to verify the clearance. I am kinda worried that the prop could hit.

Anybody else have an 72HRT prop on an RV-8 with a Vans cowl? How much clearance do you have between the blade trailing edge and the cowl?

I have been helping my friend Scott (who is traveling on vacation) with his new RV8. He too changed from the 200RV to newer (actually now "legacy") blades.
Standard Van's cowl, (already painted), IO390 EXP upfront.)

With two people, you CAN turn the blades to the mechanical stop.

The issue (as you are probably concerned about) is what happens at the stop in flight when the engine can MOVE. Thus some extra space is in order.

WW supplies some "spacers" that can be used to limit how coarse the blades go. We were concerned about overspeed if the blades were not coarse ENOUGH, especially given that he now has that IO390 up front.

Before the spacers, we were able to turn the prop past a set point of say 2500 RPM. (Never pushed it past 2600 in the tests).

I don't remember what size shim we used but there was a size that worked throughout the speed range and (so far) no hitting of the BEAUTIFULLY painted cowl.

I have done some of the flight testing and I know that it works up to Vne without overspeed.

There is hope ...


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