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Old Oct 09, 2014, 11:03 AM
Registered User
United States, WA, Twisp
Joined Sep 2013
429 Posts
Question
Newb questions on spinners...

Sorry if this is really basic, but I'm new to fixed wing, in the process of building my first, a Multiplex Fun Cub. Just to make matters more interesting, I'm planning on using a 3 blade prop. Anyway, here's my questions, in no particular order .

Do spinners serve any purpose other than decorative?
How do you size them?
Other than weight, is over sized a problem? And what about undersized?
How are they mounted? I'm using a fairly large motor with a short shaft and 6mm prop adapter, seems like the few I've seen that actually show them mounted are on collets.
Can/do they create balance issues, and if so, how do you balance them?
Best material, or is it just a matter of cost/personal preference/availability?
Who's best? I'll leave it to you to define "best" .
And last (for now), do spinners have any impact on prop efficiency?

Thanks for the help and patience, guys. Later.

Dave
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Old Oct 09, 2014, 11:33 AM
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ggcrandall1's Avatar
USA, GA, Marietta
Joined Aug 2005
5,700 Posts
Quote:
Originally Posted by daved20319 View Post
Sorry if this is really basic, but I'm new to fixed wing, in the process of building my first, a Multiplex Fun Cub. Just to make matters more interesting, I'm planning on using a 3 blade prop. Anyway, here's my questions, in no particular order .

Do spinners serve any purpose other than decorative?
Yes, they smooth the airflow around the prop hub. By how much....... ?
How do you size them?
That depends on the cowling.
Other than weight, is over sized a problem? And what about undersized?
Over size could be a problem if it restricts airflow to the motor. Undersize probably no problem.
How are they mounted? I'm using a fairly large motor with a short shaft and 6mm prop adapter, seems like the few I've seen that actually show them mounted are on collets.
Depends on motor and airframe.
Can/do they create balance issues, and if so, how do you balance them?
Could cause balance problems (vibration) but it would have to be severe to be a problem. There are probably balancers for them. Try google.
Best material, or is it just a matter of cost/personal preference/availability?
Who's best? I'll leave it to you to define "best" .
And last (for now), do spinners have any impact on prop efficiency?
Probably. The question is how much and is it significant.

Thanks for the help and patience, guys. Later.

Dave
I doubt it will make any difference to your Fun Cub performance.

Glen
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Old Oct 09, 2014, 12:04 PM
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1320fastback's Avatar
USA, CA, Oceanside
Joined Jul 2008
3,332 Posts
I balance my spinners. I mount the spinner to the backplate but before screwing it down put the Dubro prop balancer rod thru it.

Hang it on the balancer with the far end of the rod UNDER the wheels as it will want to fall off otherwise.

For balance I will minorly grind/sand the heavy side of the backplate or put Velcro inside the spinner on the light side and add CA until it balances.

Pic of how to mount it is worth a thousand words, but i don't have a pic...
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Old Oct 09, 2014, 12:39 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,406 Posts
if you go to the main thread --

Multiplex Fun Cub

and use the Search this Thread facility on either, 3 blade , or , spinner, you should find quite a few post on what others have used.
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Old Oct 09, 2014, 02:43 PM
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Letchworth, Great Britain (UK)
Joined Jul 2004
11,715 Posts
Quote:
Originally Posted by daved20319 View Post
Sorry if this is really basic, but I'm new to fixed wing, in the process of building my first, a Multiplex Fun Cub. Just to make matters more interesting, I'm planning on using a 3 blade prop. Anyway, here's my questions, in no particular order . ...
As eflightray has suggested, find out what props other people are using on their Fun Cubs. If you simply put on a 3-blade prop that's the same size as the stock 2-blade one, you could do some serious harm to your motor and speed controller for, all else being equal, a 3-blade prop will draw more amps than a 2-blade

To give the same amps as a 2-blade prop, the 3-blade will have to be slightly smaller in diameter and/or pitch. A wattmeter is your friend, for it will allow you to measure the actual amps at full throttle so you can check if you're over the motor's or ESC's spec.
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Old Oct 09, 2014, 07:31 PM
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United States, WA, Twisp
Joined Sep 2013
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Originally Posted by abenn View Post
As eflightray has suggested, find out what props other people are using on their Fun Cubs. If you simply put on a 3-blade prop that's the same size as the stock 2-blade one, you could do some serious harm to your motor and speed controller for, all else being equal, a 3-blade prop will draw more amps than a 2-blade

To give the same amps as a 2-blade prop, the 3-blade will have to be slightly smaller in diameter and/or pitch. A wattmeter is your friend, for it will allow you to measure the actual amps at full throttle so you can check if you're over the motor's or ESC's spec.
Thanks for the responses, guys. Guess I should have been a bit more specific, I'm new to fixed wing, but I've been flying and building helis and multi-rotors for awhile, now. The only reason I mentioned the 3 blade is that it seems harder to find spinners for them vs. a 2 blade prop. The "stock" blade for the Fun Cub is a 13x4, I'll be using a 10x6 3 blade to start out. If eCalc is close, this should give me a good balance between performance and flight time, while still helping a new pilot stay out of trouble .

And yes, I know about and am working my way through the Fun Cub thread, but that things up to 1500 pages !! I just felt this question was more general, and more beginner oriented, so I asked it here. Later.

Dave
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