2 BLADE to 3 BLADE conversion...

[TomcatFLYER]

Hi, is there a way to calculate which propeller to use when converting from a two bladed propeller to a 3 blader?

the motor i am using is an E-MAX blue sky 2215/25

here are the propeller data (2 bladed) stated on their site:

Voltage Propeller RPM CURRENT DRAW THRUST
12.0V 10X5(Thin) 8180 14A 850g

12.0V 11X7(Thin) 6280 18A 905g

12.0V 1047GWS 7200 16.5A 930g

12.0V 10X4.7(SLOW) 7250 16.5A 950g

12.0V 1060GWS 7800 15A 850g

12.0V 9X4.7(SLOW) 8750 12A 810g


The non, gws propellers are based on e-max produced propellers which i assume are pretty much similar to the normal GWS orange propellers.

After some evaluation, i determined that the set-up i require is similar to that of either the 10X5(Thin) ,9X4.7(SLOW) or 1047GWS

how ever, my choices of 3 bladed propellers are limited to

GWS:
HD8040 / EP1060 /HD9050

I determined that 8040 may produce insufficient thrust for my build, also, the motor's suitability specs do not include 8' propellers...

what;s left is with the 10" and the 90"

however, if i use a 3 bladed 10" by 60 propeller, it is likely that my current may exceed my limit of 18A (based on the table)------ any takes on this statement?

so my pictured best choice would be the HD9050...

i assumed that increasing a blade will decrease the rpm and increase the current flow.

i also assumed that increasing pitch will increase current flow and decrease rpm and increase thrust

increasing propeller diameter will do similar

and vise versa.

any takes on my analysis? i don't really know how to convert, what i have done is based on wild guessing.

[Jack_Chen]

I heard you either reduce 1 off the blade length or 1 off the pitch for a 2 to 3 blade conversion.

Can check out the Master Airscrew props online if you want 3 blade ones.

I got a bigger problem on my hands, I need to find a pair of 3 blade contra-rotating props. Which is possibly a prop with a pusher.

[TomcatFLYER]

aircrew has... i just saw a normal and a pusher version of a 3 blader in NTC hobbies, with some tweaking, you maybe able to make a contra-rotating motor... if you need counter-rotating motors, just mount them.

[Raven]

If your talking about the P-38, your answer is here.

http://www.daddyhobby.com/forum/showthread.php?t=29827&highlight=P-38

Remember to fly the bird a little tail heavy. You will have nose gear problem if you come in too hot as the mounting is very weak.

[Jack_Chen]

Thanks guys, nope, it's not a P-38. P-38 are unique.

Just the average twin engine planes like a Twinstar. Actually, I am thinking, just a 2 blade prop-pusher can already.

In future (which I hope is very long), I am thinking of a B-25J Mitchell. The 3 blade props will look good on those. Master Airscrew 9x7.

[simonwoo]

Hi bro I'm also using the same motor as you. That motor is recommended to be paired with a 25A ESC, right?

Sorry not sure if I missed out the info, what plane are you flying, at what weight now and with what prop do you typically use?

[TomcatFLYER]

I'm on the p-38. but can;t seem to decide which propeller suits the motor i have

[simonwoo]

I believe the motor is 980KV right? With this motor, I am using a 10x4.7 on my 3D foamie. I have just fitted a 10x5E on it the intend to try it out this weekend. However I am using a 25A ESC so I'm not too worried about it. Will monitor to see if the motor gets too hot though.

If you intend to keep yout 18A ESC then to play safe, just don't put an 11" prop in. I believe the 10" should still be fine. 1080 maybe pushing it a bit to the edge, but it's hard to tell unless we really run it through a wattmeter. Anyway you can just take it up for a short flight and monitor the battery, ESC and motor heat level.

[flyg]

There is a simple conversion table here.

http://simply-rc.blogspot.com/2008/03/how-to-convert-2-blade-to-3-or-4-blade.html

[Raven]

I'm on the p-38. but can;t seem to decide which propeller suits the motor i have

3 bladed 9x5 counter prop... any bigger the blades will hit the ground or chop off your cockpit...

[TomcatFLYER]

I believe the motor is 980KV right? With this motor, I am using a 10x4.7 on my 3D foamie. I have just fitted a 10x5E on it the intend to try it out this weekend. However I am using a 25A ESC so I'm not too worried about it. Will monitor to see if the motor gets too hot though.

If you intend to keep yout 18A ESC then to play safe, just don't put an 11" prop in. I believe the 10" should still be fine. 1080 maybe pushing it a bit to the edge, but it's hard to tell unless we really run it through a wattmeter. Anyway you can just take it up for a short flight and monitor the battery, ESC and motor heat level.

Yo simon... yeah same motor... hmmm if yours is paired to the 25a one... yours is the stronger version 2215/20... mine is 2215/25 which is paired to the dual-sky 18a esc.

I'm on the p-38. but can;t seem to decide which propeller suits the motor i have

3 bladed 9x5 counter prop... any bigger the blades will hit the ground or chop off your cockpit...

YEAH... THAT'S SHORT AND SHARP... hahha thanks... yeah, i'm waiting to purchase a pair of those... currently out of cash... any ideas how to ream it to 6mm without a prop reamer?

[Raven]

Yo simon... yeah same motor... hmmm if yours is paired to the 25a one... yours is the stronger version 2215/20... mine is 2215/25 which is paired to the dual-sky 18a esc.



YEAH... THAT'S SHORT AND SHARP... hahha thanks... yeah, i'm waiting to purchase a pair of those... currently out of cash... any ideas how to ream it to 6mm without a prop reamer?

Dont worry about the holes... they are nice and big. Came with adapter rings to size down the hole.

[simonwoo]

Ah yes sorry bro, just to correct myself a bit. I use the 2215/20 (1200KV) with my warbirds, and the 2215/25 (950KV) with my 3D foamie. I pair both with 25A ESC since I have it, and also to play safe bit

Both motors I don't think are suitable for anything more than 10" personally. But like raven said, I guess the most basic sizing would also be whether there is enough clearance for the props :P

I don't use prop reamers - I use my electric drill instead But you can only use that with the thicker and stronger props. The GWS ones might just bend when you try to drill the hole

[TomcatFLYER]

hahah, yeah, i wanted the 2215/20... but it will overpower my p-38... i intend for it to be a "scale" flyer... hence i settled for the 25. but on the general... the performance of these e-max motors are really satisfying knowing the cost of it.

just the 2-bladed prop performance is good... i can't wait to strap it up for a three prop.. hhahaa

[simonwoo]

Agree bro, they are value for money alright. Unfortunately this model is still unable to power my Flash 3D foamie, so I had to get a new motor. I am using quite a few pieces of the 2215/20 for my other planes though, and it's great

Let us know how it feels when you change to 3-blade. I have some too and have been intending to fit them on my warbirds for more scale flying