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Three Bladed Propeller for BH Stuka - 1/29/2011 3:57 PM   
helipk


 

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From: marlboro, NJ, USA
Status: offline 		I plan to used a three bladed propeller on my Scorpion S4020-12 (542 KV) motor running 6 cell (30C) 4000MAH lipo on BH Stuka (approx. 13 lb). Would appreciate it if anyone could advise what size of propeller (and made if possible) would best suite the application. Thanks.

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RE: Three Bladed Propeller for BH Stuka - 1/30/2011 3:59 AM   
91zulu



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Status: offline 		Maybe a 16x10 Zinger wood or Master airscrew

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RE: Three Bladed Propeller for BH Stuka - 1/30/2011 5:37 AM   
kahloq



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Status: offline 		Your motor has a max wattage of 1850 and max amps of 85. The only way to know whats the best fit since no prop recommendations were given on scorpion's site is to test a few using a wattmeter.
Here's the thing, the bigger the prop and the higher the pitch, the faster your going to deplete the battery.
On 6s lipo, a 16x10 3 blade prop is going to fly your plane at a top speed of 94.6mph on that motor if it doesnt blow up first. 95mph is WAY over kill on a stuka for scale speed and is going to draw probably a lot more then 85 amps at full throttle.

I have a ton of electric planes with various size motors, from little park fliers to planes over 80" wingspan. My best advise is to use a 15x8 3 blade prop from Graupner(has a nice wide paddle for plenty of thrust) and the pitch wont over tax your motor. Or...use a 15x7 3 blade prop from Master Airscrew.
Remember, even if the motor could spin a 16x10 3 blade without konking out, a Stuka is not a fighter plane. Its a dive bomber and they didnt fly super fast.
With only a 4000mah battery, running a smaller prop like the 15x8 graupner or 15x7 MAS will allow you longer flight times.
But no matter what, you need to use a wattmeter to test to see if the prop you choose doesnt cause the motor to pull more amps, watts then its designed for. If it does, then you have to go down in diameter and possibly pitch as well.

Another option is a 14x9 3 blade from master airscrew

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RE: Three Bladed Propeller for BH Stuka - 1/30/2011 8:09 AM   
91zulu



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Status: offline 		I think since it is a low KV motor it should be able to swing a 16 inch prop with no problem. But using a watt meter is crucial to know that you are within amp range. Try to stay 20% below max. It keep things cool and longer flight times. Too small a prop is also bad. A 16x10 or 16x8 should be good. Just so you know lower KV motor = more torque and slow turning need larger diameter prop. Higher Kv = higher RPMs need smaller diameter props.

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RE: Three Bladed Propeller for BH Stuka - 1/30/2011 4:26 PM   
kahloq



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Status: offline 		It may be a low kv motor, but the motor size itself is only a 40. Yes it can swing a 16"diameter prop, but, maybe not so much on 6s, but 5s and definitely 4s. The higher voltage you go on a given motor, the more stress your putting on it with the same prop...so you have to start lowering the prop size to keep from overamping it.
Im well aware of kv's relevance on torque 91zulu.
You are forgetting this isnt a 50 or 60 size motor, so on 6s.....this 4020 will be overtaxed turning a 16x10.

Helipk.....if in doubt at all...email Scorpion and ask them what they think before buying a propellor.

Ill give you one example of a motor really close to this one kv wise. Its a turnigy SK 4060-500kv. With a 16x12 prop, even on 4s, its pulling 70 amps @ 1100 watts. The motor IS rated for 6s, but if i ran it on 6s with that prop, it'd throw a magnet and cook itself.
Same would go for an e-flite or AXI motor.
I've got an Electrifly 480kv motor in a graupner fw-190 d9. I WAS running a 16x8 3 blade prop on 6s and yea it flew quite well for a couple flights, but, the battery came down very hot(another thing you have to consider) and the motor gave out on the 3rd flight. The cause? The prop was too big. I replaced the motor, put a 15x8 prop on it and all is well.

Even if a motor can sustain turning a large prop, that doesnt mean the battery is going to last doing so.

Additonally...looking at a prop chart for Great Planes Electrifly series motors.....using they listed 4060-480.....they list a 15x8E prop on 6s as the recommended prop.

All Im doing here is trying to warn you not to overprop the motor. Doing so can and WILL eventually lead to a dead motor, cooked esc, or puffed and ruined battery.

Like I stated in my first post.....use a wattmeter. There is no subsitute for this no matter what anyone tries to say is a good prop for your motor.
Its quite possible a 16x10 may be ok....but then again.....without using a wattmeter and knowing for sure.....you could end up deadsticking the Stuka.

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RE: Three Bladed Propeller for BH Stuka - 1/30/2011 8:08 PM   
helipk


 

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Status: offline 		Hi Kahloq, 91 Zulu,

Thanks a lot for your kind advices. Really appreciate it.


Kahloq,

How about Scorpion S4025-16 (332 RPM, max 2000 watts) running 8s and using 15x10x3 or 15x8x3 prop? Someone recommended  Turnigy HXT 63-64 (280KV). The reviews gave it a high mark. What do you think. Thanks.


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RE: Three Bladed Propeller for BH Stuka - 1/30/2011 10:47 PM   
91zulu



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Status: offline 		Sorry kahlog, the comment on kv and the rest was not meant for you , it was meant for Helipk. Also you are correct on the other things you stated. Helipk as stated if you don`t have a wattmeter it is important that you get one or else you will be frying a lot of ESC, batteries or motors. Now I`m aware that some motors you get comes with no starting point as to props that is why you need the watt meter to find which is the best set up that you want with out destroying your equipment. I`m not sure on the motor you have but I know Scorpion motors are more for Heli use and we also use the higher kv in jets. I think that is why there is no info on props. I could also see why you are trying to get a starting point on prop choice, better than buying a set of props only to find out none is suited for your set up. You may also need to go down in sell count try 5s or 4s. With the 6s you will be taxing you battery.You should be able to use a 80 amp ESC on 5s or 4s. As kahlog stated more sells = more amps= VERY HOT !

Ps. Do you already have the motor or is it one that you are looking to get since it seem you are into helis ?

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RE: Three Bladed Propeller for BH Stuka - 1/30/2011 11:07 PM   
91zulu



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Status: offline 		Kahlog aloso maybe you can give some better ideas on motor choice. I think a 50 series motor would be much better suited for that Stuka. Himax, Axi, Turnigy, eg.

http://www.rchotdeals.com/Products/rc/brushless_motor/A53309.html
http://www.hobbypartz.com/mo604brmo.html
http://www.hobbypartz.com/mo1102brmo.html

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RE: Three Bladed Propeller for BH Stuka - 1/31/2011 1:25 AM   
helipk


 

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Status: offline 		Hi 91 Zulu,

Thanks again for your advice. This is going to be my first lasrge scale and first plane with three bladed prop, that is why I'm trying to seek advice on how to properly set up the system. Thanks again.


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RE: Three Bladed Propeller for BH Stuka - 1/31/2011 3:19 AM   
kahloq



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Status: offline 		Helipk....I have several planes in the 73" or so size running electric setups. If your wanting to run an 8s setup, the HXT motor you listed is ok, but I'd recommend you get the turnigy SK 5065-270kv motor. It is a better quality motor. I have this exact motor on 8s 5000 in an ESM P-51B and its running a 15.5x12 4 blade APC prop. With the lower kv and on 8s, you could easily run a 16x10 3 blade prop for decent Stuka performance and get good flight time as well.
Another option is the Monster Power 110 from hobbypartz.com or the Turnigy G110 295kv
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14407

Both are the same kv as the e-flite power 110. I have that motor in an ESM ME-109 on 8s 5000 swinging a 20x10 turnigy wood prop. Again...a 16x10 3 blade would work here or you could also go slightly bigger prop size.
here is a pic of the two of my ESM ME-109's. The one closest to the camera has the e-flite 110 on 8s with 20x10 prop. The one in the background has a Graupner 16x10 3 blade. You can see that the prop looks decent scale wise. The Graupner Fw-190 D9 has that electrifly motor with a 15x8x3 on 6s

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RE: Three Bladed Propeller for BH Stuka - 1/31/2011 6:01 AM   
91zulu



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quote:

ORIGINAL: helipk

Hi 91 Zulu,

Thanks again for your advice. This is going to be my first lasrge scale and first plane with three bladed prop, that is why I'm trying to seek advice on how to properly set up the system. Thanks again.




Ok then here goes. the Scorpion that you mentioned is = to a 40 size glo 2 stroke engine, too small for the Stuka. You need more like a 60 -75 size which is the 50 series motors. On most motor specs the first set of numbers tell you what size the motor is. eg, first numbers 40xx is a 40 size, 42xx is closer to a 45/46 2 stroke, 50xx is more a 60 size 2 stroke, 53xx =80-90 2 stroke, 60xx= 120-160. Now also the second set of numbers is the turns or poles it depends on the manufacturer how they do it. eg a 4006 is a 6 turn which mean it is a higher turning 40 size, then there is a 4012 which has more turns = lower RPM meaning use a bigger prop. To put it simple lower the second 2 numbers 40(06) the more rpms = use a smaller prop, higher the second number = slower turning use a bigger prop. Now on the bigger motors you will see specs saying the motor is = 60-90 size 2 stroke. Now you may see a motor that is a 5050 or 5055 or 5060. The 5050 is closer to a 60 the 5060 is closer to a 90 because of the number of turns. Now also remember there is also a cell range eg. 6s- 8s, where the 6s set up gets you to swing the biggest prop the specs says the motor can swing and the 8s the smallest prop. Some where between those two ranges is the sweet spot we look for.
So for your set up a motor with the numbers 5055, 5060, 5063 or there about would be good for the weight of the plane and the prop you want to use.
Now using a bigger motor you have to watch prop clearance and cell count, because too big a motor may push you to use the smallest prop it can swing in order so it don`t strike the ground on take off but that will require using the higher cell count for that motor meaning more weight and heat.

This is just a rough explanation of the motor specs so you have a better understanding. Hope there will be some more input from others.

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