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P-38 conversion: Need 14*10 or 14*11 3-Blade prop

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P-38 conversion: Need 14*10 or 14*11 3-Blade prop

Old 11-02-2006, 09:45 AM
  #1  
Der Goetz
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Default P-38 conversion: Need 14*10 or 14*11 3-Blade prop

I will be outfitting my KMP P-38 with two AXI 4130's on 6s. I am running one of these in my H9 Corsair and love the performance and draw (53 Amps on 15*10E).

Now I am facing several tasks and question marks.
I am "stuck" with 3-Blade spinners since I got two VERY reasonably priced True-Turn Spinners with the kit and they were pre-cut to 3-Blade.

Here we go:

- Who makes a 14*10 3-Blade, and even better, can pair it with a Pusher version as well so that I can counter-rotate?

- So far I have only found Master Airscrew with their 14*9, but it doesnt have a 3blade twin. BUT they have paired 16*10's. Any way I can get two of those and cut them to 14 and balance them? I mean, I bet I can, but any tips and tricks on cutting 3-Blade props? I guess I will tape off what I need to take off, sand it down, and then start balancing. Or any tried and true ways of doing this?

- And how smart is it to go Gas 3-Blade in general? I know about the slight increase in thrust and slight loss in top speed, but what about the fact that I am now using a Gas prop? I am afraid I am getting hit twice, once by less top speed, secondly by less efficiency due to the Gas prop itself. Any advice/ideas/comments on this?

- I can still return the spinners and go 2 Blade...a better idea per se?

Thank you for your time and advice,

Götz
Old 11-03-2006, 08:01 PM
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Matt Kirsch
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Default RE: P-38 conversion: Need 14*10 or 14*11 3-Blade prop

It's generally not recommended that end users cut down their props. If you do it, be VERY careful, measure ten times, cut once. Don't let anyone in front of or off to the side of the spinning props for the first few runs. Check your blade tracking, properly shielded of course.

The Master Airscrew props, while not the most efficient, will do just fine, and they'll look quite scale.

One thing you may want to consider is that the KMP P-38 is designed for two engines turning in the same direction, so the side thrust angles of the two engines are probably optimized for that. A slight adjustment to the thrust angle on one or both motors may be in order to get the plane flying straight.
Old 11-03-2006, 08:41 PM
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Der Goetz
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Default RE: P-38 conversion: Need 14*10 or 14*11 3-Blade prop

Matt....thank you SOOOO much! That was some awesome advice, indeed! I would have never thought of the fact that both props SHOULD spin in the same direction!
I will definitely go ahead and leave the setup the same. I dont really want to play around with thrust angle too much.

Thank you so much, once again your advice made the difference!

best regards and thank you,


Götz
Old 11-18-2006, 12:20 AM
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bcn0209
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Default RE: P-38 conversion: Need 14*10 or 14*11 3-Blade prop

Hi, just saw your post. I am building a scale P38 too although mine is 40" span Guillows with twin Hacker motors, Robart retracts. I too wanted scale counter-rotating props and after an exhaustive search, I found the answer...

http://www.ramoser.de/home_e/variopr...rioprop_e.html

Varioprop makes a 13.9" scale prop and 3-blade hub that provides completely variable pitch. Pitch is set ground-adjustable-only but never-the-less, you can make any pitch that you want and optimize your performance, current etc. And they look so real: Your application would require the following part numbers!

Size: 12C
Item-No.: 353-12
right handed, electric prop only
RPM max (Blade): 8.000 RPM

Size: 12C
Item-No.: 353-12-L
right handed, electric prop only
RPM max (Blade): 8.000 RPM
left handed (looks like No. 353-12, just mirror-operated)

three blade hubs depends on your motor shaft diameter..Your AXI has a 6mm shaft so you probably need:

Size: 12C
Shaft-Diameter (Hub) or
Prop-Diameter (Blade): 8.0 Millimeter
Weight: 20.0 gramm
Item-No.: 38012

since your doing counter rotating you will need two 6mm steel-collet chucks one left hand and one right hand.

Size: 12C
Shaft-Diameter (Hub) or
Prop-Diameter (Blade): 6.0 Millimeter
Weight: 14.3 gramm
Item-No.: 1216

AND

Size: 12C
Shaft-Diameter (Hub) or
Prop-Diameter (Blade): 6.0 Millimeter
Weight: 14.3 gramm
Item-No.: 1216
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