Bully, if there is nothing otherwise wrong with your engine, that will be plenty for flight. I predict you will get an additional 500 RPM on take off roll and even more than that in flight. When I was flying normally aspirated I got only 4600 on take off roll (4200 static) and that was plenty to beat all the cessnas. If you are doing that at 50" you will be making a lot more power than I was.
Just how big is this MONSTER prop?
The formula I have for tip speed (ft/sec) is:
Prop RPM * Diameter * 0.00436
This must be an approximation because it doesn't take into account aircraft speed, which properly should be a factor.
Dave Leonard
On 12/19/05, Bulent Aliev <atlasyts@bellsouth.net> wrote:
Thanks Dave. it makes me feel better now that I know I was wrong. My problem now is: I can spin my "monster prop" (static) up-to 4000RPM and 50" MP I don't think I can get much more in motion and may not get enough rpm for flight. I'll see first how much difference it will make on fast taxi. John Slade also will bring his Performance prop one day, so we can compare them.
BTW the prop tip speed formula given to me was:
Prop D" x 3.1416 x RPM divided by 720
Buly
On Dec 19, 2005, at 6:06 PM, David Leonard wrote:
Oh, BTW Bully. You will also note that at 6000 RPM the prop is doing 2750 which a lot of certified props will turn, even if 74"long.
Also, short prop are not necessarily less efficient, its just that the speed of peak efficiency is shifted to a higher airspeed, and probably that peak is a little more narrow.
Dave Leonard
On 12/19/05, Buly <atlasyts@bellsouth.net
> wrote:
Yesterday somebody gave me the formulas to calculate the prop tip
speed. I did some calculations and looks like us with the
2.17
redrives are kind of painted in the corner. Hope I'm wrong, but if I
want to keep the tips from going supersonic, I have to cut down the
prop to 64" or keep the engine below 5500 RPM. The choice is either
inefficient prop and adequate power, or efficient long prop and not
getting all the power from the engine? Am I wrong?
Buly
atlasyts@bellsouth.net
--
Homepage: http://www.flyrotary.com/
Archive and UnSub:
http://mail.lancaironline.net/lists/flyrotary/
--
Dave Leonard
Turbo Rotary RV-6 N4VY
http://members.aol.com/_ht_a/rotaryroster/index.html
http://members.aol.com/_ht_a/vp4skydoc/index.html
--
Dave Leonard
Turbo Rotary RV-6 N4VY
http://members.aol.com/_ht_a/rotaryroster/index.html
http://members.aol.com/_ht_a/vp4skydoc/index.html
|