I'm with you Tim. We need the 13 x 4.5 3B Pushers. 
Dennis - how about it? Could you talk to ACP?

Norm

12 x 6p and  12 x 4.5p  would be the sizes I'd look for.......but then again  - the 2 blade works so well, there is no point changing (except clearance of course)

Dennis I would like to explore the full 13 x4.5 P.
If we go to a semi scale stunter such as a Al Rabe 51 I think a 3 blade 13 x 4.5 would be the ticket.  I had the privlege of flying John John Callentine's Rabe P51.  I flew faboulos with a PA 61 just think what it could do with an Electric turning a 3B 13 x 4.5 Pusher.
Of course you could always trim the 13" to less.
Norm

Works for me, I have cut down a bunch of the 13 4.5 size to what I want.

I'm also thinking that because of the new thick hub design we should go for 5.5 not 4.5 pitch.

What say ye all?

Posilutely, Absitively YES.  

The original 13 x 4.5 thin blade is pretty hard to beat (so far it's impossible) and the thicker ones just don't perform as well.
The 12 x 5.5 might be the perfect compromise.  Put me down for 12 if you decide to go that way.

I agree. 13" dia would also cover 12".  I'm also thinking that because of the new thick hub design we should go for 5.5 not 4.5 pitch.

What say ye all?

Hi Dennis,
Yes, we want to go up on pitch. 5.5" sounds right to me.
This will absorb the power needed for big ships on long lines and turn at the right RPM (high 9's / very low 10's)  for a good compromise of both noise and braking.
The guys on 60' lines will not find it useful without repitching, but a 3-bladed 13" diameter will be for absorbing near 500Watts!

Regards, Compadre,
  Dean P.

I agree a 12x5.5 EP would be just what the Dr. ordered. put me down for 12.  We might have the numbers that make a min. order!

Bad News & Good:

* APC is not willing to make an electric 3-blade.  This unchanged from what they told me in the past, only they were a little more adamant about it this time!

* APC suggested what could be a very good alternative.  They apparently developed a special prop for R/C Pattern Flyer Chip Hyde.  Chip was interested in good static thrust and good braking.  In his case they DID try 3-blades but they did not work well.  What did work was a new wide blade wide blade design.  Chip's using a 24" diameter, however APC proposed to applying the same design philosophy scaled to a 13" dia prop.

* This sounded like a viable alternative and I gave them the go-ahead for prototypes of a new 13x5.5E Pusher Wide Blade.  The new prop will be based on the 13x4.5 EP, with the blade profile widened - it is not a linear scale-up.  The pitch will be increased to 5.5".  That should make it a low 9000's RPM prop.

While this is not the 3-blade people were asking for it should have design elements that work in our favor:
* The 2-blade design will be more efficient than 3 blades.

* The wider blade fills up the disk area - mimicking what we achieve with a 3-blade design.

* 2-blade will be lighter than the 3-blade would have been.

* The new design taps into APC's design experience on the wide blade design for pattern props.  From checking their web site, APC makes a wide blade electric prop in 17" - 22"; the 24" prop they mentioned to me must be a new one.  I am hoping our RC Pattern & IMAC voices can check in on this point and affirm (or counter) whether the wide blade props have been a success for those folks.

* Finally, from a purely pragmatic point of view, APC is willing to make the 2-blade; they are not willing to make the 3-blade!

* The lead time on the prop will likely be in the fall, the prove-out samples later than that.  NOT what we wanted to hear but we are waiting in line behind several other APC projects.


Back in the IC engine days (!!!) lots of empirical data - and opinions - were generated on wide blade versus narrow blade props.  I suspect a lot of those rules will apply EXCEPT with a governed electric the braking effect for wide blades should be even more powerful.