|
|
Bill Bradburry wrote:
Joe Hull says:
Snip...
"Thanx Ed. I have a 64"Dia. x 76" pitch prop. It's supposed to be cruise
prop
that is designed for 190HP and 220MPH. But you're right, it's too early
to
be cutting on the prop."
OK, here is where I demonstrate my ignorance...
My rough calculations, with an estimated 20% slip, says this prop with a
76" pitch, is good for 121 MPH with a 2.85 drive and 160 MPH with a 2.17
drive assuming a 6000 RPM cruise???
Where am I going wrong?
Bill Bradburry
--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/
For 2.85:
6000 RPM / 2.85 = 2105.263157894737 RPM (at the prop)
2105.263157894737 R/M * 76 I/R * .8 = 128000 inch per minute
128000 I/M / 12 I/FT / 5280 FT/Mile * 60 M/Hour = 121.21 MPH
For 2.17
6000 RPM / 2.17 = 2764.976958525346 RPM (at the prop)
2764.976958525346 R/M * 76 I/R * .8 = 168110.599078341 inch per minute
168110.599078341 I/M / 12 I/FT / 5280 FT/Mile * 60 M/Hour = 159.2 MPH
Looks like your numbers are on target, but isn't 20% slip rather large?
--
,|"|"|, Ernest Christley |
----===<{{(oQo)}}>===---- Dyke Delta Builder |
o| d |o www.ernest.isa-geek.org |
|
|