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Old 06-29-2022, 12:51 AM
scsmith scsmith is offline
Join Date: Jan 2008
Location: Ashland, OR
Posts: 3,262
Default 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?
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet" Flying since Sept. 2009
Hobbs 725
1/4 share in 1959 C-182B (tow plane)
LS6-15/18W sailplane SOLD
bought my old LS6-A back!!
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