On Jun 22, 10:18 pm, "Sonerai" <rpr...@[EMAIL PROTECTED]
> wrote:
> Ken,
>
> Good thought on the governor. I pulled the actual throttle with my
finger
> and got 300 rpm more static. After a small modification to the linkage
I
> went back to the lake and now I gain another 100 on top of that as speed
> builds to final rpm of about 3070. Now I found I was seldom using full
> throttle unless there was good open water ahead. I'll try to find a gps
for
> next trip out and get true speed. This prop probably is close enough to
> shave a little after all. How does 1/4inch sound for a start? Do you
> normaly flatten the backside all the way to the leading edge or blend it
> about half way across?
>
> Randy
Randy,
Baby steps, especially if you are only dealing with a couple hundred
RPM. It's easy to de-pitch the prop, but not nearly as easy to put
the pitch back on. :)
Here's how I do it:
Put the prop on the bench, such that the fan would fly straight up if
you were to apply power.
Put a line 1/8" of the way in from the trailing edge on both blades.
Be careful to get an accurate distance.
Grind the trailing edge of the prop off vertically, so that the
trailing edge is squared off. Go right up to the line.
Flip the prop over, and on the bottom (flat side, now on top) of the
blade sand the surface so that the flat goes up to the top corner
(curved face) of the trailing edge. It's im****tant to sand the flat
surface. Sanding the top surface actually increases the pitch
slightly, where sanding the bottom face depitches.
Bolt the prop on and try a dry run for RPM. It's best to not get the
prop wet during the test, so if you can find a soccer field or
something that's best, or just do a static test.
If necessary, you can repeat the whole process. Remember that as you
keep repeating, the RPM will climb slightly more with each iteration.
Try not to get impatient, and remember that altitude, temperature and
humidity will affect your engine performance. Unless you're racing,
most people I know turn about 3200 max.
Once you've done this, it takes about 10 or 15 minutes for each pass
through this process. Once you're done, don't forget to balance the
prop again and glass it, then balance it a final time. And avoid rain
and sand for about 2 weeks.
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