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General control line discussion => Open Forum => Topic started by: Andrew Borgogna on December 03, 2009, 09:12:24 PM

Title: Three blade prop question
Post by: Andrew Borgogna on December 03, 2009, 09:12:24 PM

I know this subject has been talked out before, but does anybody have a conversion table for replacing a two blade prop with a three blade prop.   This all relates to getting the right prop for my LA .65 on my Score.  Currently I am using a 12x5 Zinger and getting 4.5 second lap times on 60' lines.  I was considering moving to a 14x4 but that's a bit big in diameter so I would like to use an equivalent three blade if I could.
Andy

Title: Re: Three blade prop question
Post by: Rudy Taube on December 04, 2009, 12:48:35 AM

Hi Andy,

Here is the quote from the package my Master Airscrew 3 blade came in:

2-Blade to 3-Blade Conversion: decrease diameter by 1" and increase pitch by 1" if possible. Adjust to 2" for larger diameters (14" and up).

Some E flyers are replacing their APC 12 x 6 E prop with a Master Airscrew 11 x 7   3 Blade prop. It seems to work very well and gives a little extra ground clearance. I just received mine, and will be giving it a try soon.

I hope this helps.

Regards,  H^^

Title: Re: Three blade prop question
Post by: jfv on December 04, 2009, 07:57:10 AM

I found a study done on model airplane propellers that gave the following rules:

For three blades:  Diameter  ≈  0.904 times the diameter of an equivalent two blade prop.

For four blades:  Diameter  ≈  0.84 times the diameter of an equivalent two blade prop.

Can't find the original reference right now.  I will post the link when I get it.

Title: Re: Three blade prop question
Post by: Randy Powell on December 04, 2009, 08:45:19 AM

It's probably just me, but I'd try a 12.5 x 4.5. APC, Zinger (make your won prop kit), or similar as a 2 blade or a 12 x 4.5 three blade.

Title: Re: Three blade prop question
Post by: Andrew Borgogna on December 04, 2009, 10:11:30 AM

Thanks a bunch guys, I will use and save your valuable information.
Andy

Title: Re: Three blade prop question
Post by: Mark Scarborough on December 04, 2009, 11:28:32 PM

You mayu also take a look at XOAR props they make a 13X4, and a 13X5 that may fill the bill for you.

Title: Re: Three blade prop question
Post by: Mike Scholtes on December 05, 2009, 10:17:04 AM

Hi Andrew:

You didn't ask this, but I think you are flying the Score on way too short lines. I have a Score with an Enya 61CXS Pro that I fly on 65' lines, with about 5.2 sec laps. A model that big and heavy needs more room to roam, I think. You will give yourself more airspace to develop the maneuvers on longer lines as all the maneuvers will be larger.

I use a Mejzlik carbon 3-blade 12.5 x 5.2 on the Enya, a non-piped engine. This prop is specifically for non-piped 60s. Beautifully made, reasonably priced. I believe Randy Smith sells them, along with the Enya motors. I can also give a great recommendation for the Enya 61. This is a new design, not the Enya clone of the old ST60.