mercula

My Feedback: (1)

Im just trying to find out what different prop styles do for a certain plane or motor ,
What is the difference between ,Power point , APC /sport .vs.pylon .vs .pattern ,
master airscrew's, scimtar's, Zingers ect..... Does it all relate to rpm and different
pitches ? Is there any cross-refference between different prop manufactures ?
Like a master 10-6 = 10-4 APC ? Does a pylon APC have thinner blades than
a sport APC ? Does it come down to looks and safety ? In this sea of propellers
Is there any "guideline" ? Thanks for all of your answers .
[sm=confused.gif]

FHHuber

You could come up with BOOKS and BOOKS of info here...

Lets just compare an APC grey 9X6 to a Master Airscrew black nylon (standard version, squared tips...) 9X6.

The APC prop weighs a little less. That givess a lower torque effeect on the model. (not much...)

The APC has a 'Cleaner" aerodynamic shape.
1) The airfoil is a better design, THe SHARP trailing edge gives the prop a bit less drag... (DON'T sand that off!)
2) The APC has about the same total blade area... but less of the area is near the tips.
3) The tip shape produces a smaller tip vortex... and the tip vortex is a huge part of a propellors drag. (which is what uses up the engine's horsepower)

The APC is more fragile.. you chip it and you HAVE to replace it. The Master airscrew is flexible and can stand up after its been chipped a little.

You will get higher RPM from the APC. And you will get more thrust in the air (when the airplane is well above stall speed). The "static thrust" may be IDENTICAL... because static thrust maxes out based on propellor diameter and blade area.

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That's just being brief about the differences in the 2 designs... The APC is a newer design than the Master Airscrew. (I use both brands about equally... so I'm not saying that APC is BETTER... its different.)

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Almost all brands will ffer the same pitch and diameter combinations. The exception is Bolly.

Bolly "Clubman" propellors are offered in sizes such as 10.5X5. They all have an extra half inch diameter and Bolly SAYS ignore that half inch when comparing prop size to what you have been using... and you supposedly get the same RPM... (not really true... especially comparing to an APC...)

Bolly's Clubman props are shaped a lot like the APC... and made of a brown plastic that is about as flexible (and heavy) as the Master Airscrew black props.

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Guidelines? You'll get some "standard recommendations" from a lot of people... I would probably disagree with some of them. (because experience has taught me different)

I will refer you to:

http://www.rcuniverse.com/forum/m_15...tm.htm#1513587

Geistware

My Feedback: (16)

Hey, you want to write a complete article on propellers? I will post it on my site.

Richard L.

My Feedback: (24)

You ignore the extra half inch because the small tips of these props do no work and exert no load on the engine. The same applies to APC props. At least Bolly is being honest about it. This is why you generally get higher RPM on an APC since it has a smaller effective diameter than a same size prop with wide tips.

jaka

Hi!
Don't agree with you ..being a pylonracing guy I know from experience that extra diameter counts!
As for propellers in smaller sizes 5"-16", APC is much better than Master airscrew.....but there are other props that are good too like the British RAM plastic props and the German Graupner plastic "Cam props". Australian Bolly is also good . But as APC is widely available world vide why not use them.


Regards!
Jan K
Sweden

Richard L.

My Feedback: (24)

I really like Graupner props. They are very well designed and engineered. I get the best speed and thrust out of them.

Strat2003

My Feedback: (1)

Nobody mentioned that a Master Airscrew will cut you, but an APC will cut you REAL BAD!

Hasn't stopped me from using them, though

kdheath

The bottom line is that you have try some different props in the appropriate size range until you get the performance you want at a price you're willing to pay. I will add (my prejudice) that Master Airscrew props make pretty good paint stirring sticks. APC, Graupner, TaiPan, Bolly-all good products. There isn't any single best combination.

FHHuber

I am by no means a propellor expert...

I have a TON of empirically derived knowledge of what to expect... and a little bit of "education" gleaned mostly from... 1936 to 1943 model aircraft magasine articles on how t design propellers. Unfortunately... I don't have much experience with the correct way to explain what I have learned.

Feel free to grab the "soapbox" info I have posted and edit it into a useful article for your site.

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BTW... the old articles n propellor design.. say:

1) determine desired flying speed.
2) determine rpm of the engine fr maximum power (not maximum rpm, they are NOT the same)
3) multiply desired speed by (expected slippage factor plus 1) {expected slip is 50% to 100%... NEVER higher}
4) divide result of 3) by 2). You now know the pitch you want.

NOW go to the table of load factors... ad find the prop diameter at that pitch which gives the BHP rating or your engine at the rated RPM.

Now you know your desired prop size.

Geistware

My Feedback: (16)

Naw.... I prefer a spread sheet with the calculations on it