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        Discussion What makes a slow fly prop, a slow fly prop?

#1 WBFAir Nov 07, 2010 03:36 AM

What makes a slow fly prop, a slow fly prop?
 
Hello all

Novice question I know, but physically what makes a slow fly prop, a slow fly prop?

Does it have like a wider cord and is meant for more torque then speed?

#2 leccyflyer Nov 07, 2010 03:45 AM

That's correct. The blade profile tends to be broader, they are also much lighter and therefore nowhere near as strong as a normal propeller, and so should not be used for high revving powerful motors.

#3 Pinecone Nov 07, 2010 04:24 AM

Some also have an undercambered airfoil to generate more thrust at a lower RPM.

#4 WBFAir Nov 07, 2010 04:49 AM

Thanks for the quick 5:30am Sunday morning replys guys.

So on the new plane I built, the stock motor was about a 1400KV on a 1800 3S 20C pack fed via a 18A ESC

Sorry don't know the motors rated Watt specs.

In looking at the prop, it looks like it could be as you described, not to much pitch but kinda wide and light.

I replaced this motor with a Tower Pro, 1600KV 200W 25A and installed a MasterScrew, G/F 3 series, 8x5 prop and am using a 2200 3S 25C pack fed via a Castle Creation, 45amp Phoenix ESC (I know its big but I had it for three years and never used it.)

This "size" prop is what is recommended by the motor manufacturer although if it is that size but a slow prop, I don't know. It just says a APC, 8x4 or 8x5.

Btw the plane is a Hobbico/Flyzone Cessna 182 which is a 37.0 oz/1,050g plane (w/the 1800 pack), 47.5in wing with a 339in wing area.

Also btw that stock prop was 8.5in but I don't know the pitch but in comparing it to the 8x5 MasterScrew, it is easy to see that it is not a 5.

So any comments on any of this and thanks again for the reply's

#5 Beachcomber Dec 22, 2010 08:46 AM

I'm new at this (just adding planes to my heli hanger), but will offer this observation/suggestion:

Both the 1400 KV and the 1600 KV motors seems too fast (rpm) for a direct drive (prop mounted directly on motor shaft), using 3S Li-Po. It might be more suitable for 2S Li-Po (since the rpm is controlled by voltage). The larger your prop diameter, the lower max rpm it has; for many reasons but mainly because of tip speed. Double check to make sure 8" prop diameter is not too big for that KV/rpm.

#6 Art Schmitz Dec 22, 2010 11:22 AM

You really need to invest in a 'Watts Up' or similar device.

#7 cyclops2 Dec 22, 2010 04:56 PM

2 Attachment(s)
A motor / prop calculator will tell you what prop # of cells mahr capacity to get flying time. Plus WOT torque thrust...And top speed.
Try the free www.adamone.rchomepage.com Before you buy anything else. Watch the EFFiciency curve & percent.

Here is my favorite motor / prop combo. It tells all.


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