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Old Mar 06, 2012, 06:25 PM
Canadian Bacon
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Kingston, Canada
Joined Jun 2004
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I remember the Zagis we had quite a few yrs ago, with the pusher prop close to the T.E. of the wing were relatively noisy.

Gord.
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Old Mar 06, 2012, 09:39 PM
Joined Aug 2011
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Quote:
Originally Posted by Flyboy Steve View Post
Otto, just ran across this thread. Looks GREAT!

I have not had a chance to play the video yet (at work), but wanted to ask:

Instead of the "bow tie" or the "foot ball" or your slot shape, if you JUST MADE THE SLOT WIDER would it have the same effect?

Is there an advantage to the shaped back of the slot as in your picture, or would you get the same impact from a square slot that was as wide as the widest portion of your slot?

Thanks!
My experiments indicated that a square slot that was as wide as the widest portion of my slot would work fine. It would be a big whole.
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Old Mar 07, 2012, 08:06 AM
Electric, lightweight so
Joined Oct 2004
166 Posts
That's very interesting - I wave a wing I was complaining about the noise just yesterday - I'll do the mods straight away! The engine's not the quietest - but this looks like it'll go some way to helping. Thanks very much!
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Old Mar 07, 2012, 08:41 AM
Joined Aug 2011
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Originally Posted by Windy Miller View Post
That's very interesting - I wave a wing I was complaining about the noise just yesterday - I'll do the mods straight away! The engine's not the quietest - but this looks like it'll go some way to helping. Thanks very much!
Give us some feedback.
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Old Mar 07, 2012, 09:30 AM
gpw
“There’s no place like Foam”
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United States, LA, New Orleans
Joined Jul 2002
24,200 Posts
Otto, Thanks !!! I’ll be sure to try that on my new foamie 117 ... !!!
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Old Mar 07, 2012, 10:05 AM
Augermeister
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United States, TX, Keller
Joined Jul 2011
2,810 Posts
I'm interersted in incorporating a slot retro for my pusher park jets. Did not see the football shape. Mine are all about 1" wide and 6.1" long to accomodate a 6 x 4. all have the wedge cut for the spinner.

Our field is adjacent to a pavillion on the lake where they host weddings. During weddings we have a no-fly rule for gas and electric pusher jets.

Thanks,

Hawk
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Old Mar 07, 2012, 02:16 PM
Fly to live. Live to fly.
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California
Joined Mar 2006
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This is really cool. I really appreciate learning about these fine points about model building. Thanks!
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Old Mar 07, 2012, 04:11 PM
Trash Hauler emeritus
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Maryland, USA
Joined Oct 2006
1,709 Posts
Dave Powers did a video about his experiments on this same subject some months ago, and came to some of the same conclusions...i.e.: that a bigger hole is better for both noise reduction and power, and that it's especially advantageous to expand the hole in front of the prop. Video here:

RC Jets: Pusher Props (3 min 1 sec)
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Old Mar 07, 2012, 04:52 PM
Registered User
how much's Avatar
United Kingdom, England, Wigan
Joined Jul 2011
776 Posts
otto

great work.. i am reluctant to fly my excellent standard sized sea-dart because of the howling prop noise.... its nearly as noisy as an i.c. model

pass me the scalpel and a couple of strips of carbon...

hello "quiet dart"

d
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Old Mar 07, 2012, 05:04 PM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
United States, CA, Santa Cruz
Joined May 2005
1,333 Posts
very nice work on this. Im glad some one with a good deal of experience attacked this with a scientific approche. we seriously need to make some kind of easy to search database with all these little tricks people have found. maybe a good wiki site. have a good section on the different Kf wing set ups and uses, motor mounting sets up, etc.

Awesome work Otto.
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Old Mar 07, 2012, 05:18 PM
MuscleCBT
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SF
Joined Apr 2006
43 Posts
I wonder...

I wonder if this is going to make my Zephir less of a noise bomb? The Zephir has the motor hanging off the back of a flying wing and it's just obnoxiously loud...well, mine is. Any different shape to put there to be as quiet as possible?
http://www.ritewingrc.com/buy-cores/wing-cores/
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Old Mar 07, 2012, 05:20 PM
Canadian Bacon
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Kingston, Canada
Joined Jun 2004
13,181 Posts
Just for laughs, this is a plane, well almost a plane, that I built quite a few yrs ago to test a reverseable pitch. The prop exploded but the plane flew on as a fun plane for about another 5 yrs. Very aerobatic fun plane. The flywheel below was also very noisy till I opened up the slot. You can tell I enjoy my hobby
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Old Mar 07, 2012, 06:48 PM
Joined Aug 2011
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Quote:
Originally Posted by MuscleCBT View Post
I wonder if this is going to make my Zephir less of a noise bomb? The Zephir has the motor hanging off the back of a flying wing and it's just obnoxiously loud...well, mine is. Any different shape to put there to be as quiet as possible?
http://www.ritewingrc.com/buy-cores/wing-cores/
Both my mini Zephrs became resonable with the reshaping of the wing in front of the prop. A significant change.
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Old Mar 07, 2012, 06:49 PM
Joined Aug 2011
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Quote:
Originally Posted by flypaper 2 View Post
Just for laughs, this is a plane, well almost a plane, that I built quite a few yrs ago to test a reverseable pitch. The prop exploded but the plane flew on as a fun plane for about another 5 yrs. Very aerobatic fun plane. The flywheel below was also very noisy till I opened up the slot. You can tell I enjoy my hobby
Cool stuff. Like Tweety.
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Old Mar 07, 2012, 06:56 PM
Joined Aug 2011
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[QUOTE=herk1;20967571]Dave Powers did a video about his experiments on this same subject some months ago, and came to some of the same conclusions...i.e.: that a bigger hole is better for both noise reduction and power, and that it's especially advantageous to expand the hole in front of the prop. Video here:

You're right on. I didn't find his stuff in my search for an answer and he just opened the hole. I really wanted to get the noise down but not create a big hole, thus my interest in shape. Good stuff.
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