Bad Day Flying

On Apr 7, 1:41 pm, "Ken S. Tucker" wrote:

Unfortunately, the motor manufacturers do not
have the varible pitch props I'd need inspite of
my letters to them to get me one.
It's like shifting gears. I pull out out the hole fast,
plane out, shift the prop bite to 2nd, then wham
out to speed slope, to 100 MPH.

If there was anything to be gained it would have been produced
long ago. Variable-pitch marine props tend to be very draggy, since
there's no way to increase or decrease the blade washout at the same
time. Aircraft constant-speed props have much more slip and will
tolerate that.
Increasing the blade angle loads the outer part of the blade
more than the inner. Nearer the hub, the blade has a higher angle due
to its lower tangential speed, and at the tips the angle is much
lower. If we have a blade angle of, say, ten degrees at the tip and 30
at the hub, and increase blade angle ten degrees, we will double the
tip angle but increase the inboard angle only 33%, to 40 degrees. That
drags the inboard area and slows thing down.
I once built a 13' cracker box inboard. Had a Chev Corvette 283
straight-shaft with the Borg-Warner Velvet-drive transmission. 250 HP,
supposedly, but it sure didn't perform like it. After I ran it for a
few years I took the prop off and started analyzing those angles, and
found that it had been repitched to a higher angle. (Itbwas a used
prop). I repitched it to the original factory spec, and boy, did that
boat scramble after that. Then I sold it.

Dan

On Apr 7, 9:32 pm, wrote:
On Apr 7, 1:41 pm, "Ken S. Tucker" wrote:

Unfortunately, the motor manufacturers do not
have the varible pitch props I'd need inspite of
my letters to them to get me one.
It's like shifting gears. I pull out out the hole fast,
plane out, shift the prop bite to 2nd, then wham
out to speed slope, to 100 MPH.

If there was anything to be gained it would have been produced
long ago. Variable-pitch marine props tend to be very draggy, since
there's no way to increase or decrease the blade washout at the same
time. Aircraft constant-speed props have much more slip and will
tolerate that.

Yeah, my rule of thumb, H20 is 800x more dense
than air.

Increasing the blade angle loads the outer part of the blade
more than the inner. Nearer the hub, the blade has a higher angle due
to its lower tangential speed, and at the tips the angle is much
lower. If we have a blade angle of, say, ten degrees at the tip and 30
at the hub, and increase blade angle ten degrees, we will double the
tip angle but increase the inboard angle only 33%, to 40 degrees. That
drags the inboard area and slows thing down.

Yup.

I once built a 13' cracker box inboard. Had a Chev Corvette 283
straight-shaft with the Borg-Warner Velvet-drive transmission. 250 HP,
supposedly, but it sure didn't perform like it. After I ran it for a
few years I took the prop off and started analyzing those angles, and
found that it had been repitched to a higher angle. (Itbwas a used
prop). I repitched it to the original factory spec, and boy, did that
boat scramble after that. Then I sold it.

A friend of ours used 2 props, one for trolling (slow)
and one for skiing (mid speed), swapping props is
fairly easy.
When you get into a class that you (Dan) describe,
there is a lot of aerodynamics, you may want canards!
Ken

"Ken S. Tucker" wrote in news:51c3498a-206f-
:

On Apr 7, 9:32 pm, wrote:
On Apr 7, 1:41 pm, "Ken S. Tucker" wrote:

Unfortunately, the motor manufacturers do not
have the varible pitch props I'd need inspite of
my letters to them to get me one.
It's like shifting gears. I pull out out the hole fast,
plane out, shift the prop bite to 2nd, then wham
out to speed slope, to 100 MPH.

If there was anything to be gained it would have been
produced
long ago. Variable-pitch marine props tend to be very draggy, since
there's no way to increase or decrease the blade washout at the same
time. Aircraft constant-speed props have much more slip and will
tolerate that.

Yeah, my rule of thumb, H20 is 800x more dense
than air.

Increasing the blade angle loads the outer part of the blade
more than the inner. Nearer the hub, the blade has a higher angle due
to its lower tangential speed, and at the tips the angle is much
lower. If we have a blade angle of, say, ten degrees at the tip and
30
at the hub, and increase blade angle ten degrees, we will double the
tip angle but increase the inboard angle only 33%, to 40 degrees.
That
drags the inboard area and slows thing down.

Yup.

I once built a 13' cracker box inboard. Had a Chev Corvette 283
straight-shaft with the Borg-Warner Velvet-drive transmission. 250
HP,
supposedly, but it sure didn't perform like it. After I ran it for a
few years I took the prop off and started analyzing those angles, and
found that it had been repitched to a higher angle. (Itbwas a used
prop). I repitched it to the original factory spec, and boy, did that
boat scramble after that. Then I sold it.

A friend of ours used 2 props, one for trolling (slow)
and one for skiing (mid speed), swapping props is
fairly easy.
When you get into a class that you (Dan) describe,
there is a lot of aerodynamics, you may want canards!
Ken



God you're an idiot.


Bertie