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Old Sep 06, 2012, 02:55 PM
Has Sloped Off
dav3uk's Avatar
Uk South Wales
Joined Aug 2009
2,323 Posts
Yes there is a large gap between the fan shroud and the start of the efflux? cone, making it as long as possible would probably make it more efficient. my yogurt pot was not an exact fit so I had to cut it and then tape it to the right diameter. The thrust is more, how much dont know but it flys faster. Most modern jet fighters have variable nozzles on the bac and the open or close to increase the available thrust. it is a balancing act between too much constriction and choking the thing and too little and having no effect. I belive it is standard practice on EDFs to get a bit more grunt. Should work on any Ducted fan/turbine as a narrowing of the area increases the speed up to a point(simply put)

Dave
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Old Sep 06, 2012, 03:44 PM
efflux RC's Avatar
United States, CA, Santa Clarita
Joined Aug 2009
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Each one of these 50mm EDFs is different. At the moment, I'm working on the Katana. The exhaust opening in that thing is about 2".
Waaay too big.(if it's speed your looking for) It's more than 100% FSA. Many folks like a 85% FSA thrust tube for best compromise of static thrust and efflux velocity. For top speed I'd go with around 75% FSA. Claus XPF has written plenty on intake and thrust tube design.

I'll be making a tube for my Katana and give you guys some info on how to do it.
We sell the Mylar material for thrust tubes, but you need such a small piece for these jets, you can probably pick up clear acetate "Report Covers" from the stationary store. (about 12 " x 9")

I have to go out for a few hours, but I'll post more info later.

Here's some quick picks on making your own thrust tube. And a link to the free app to make a flat pattern.
The pics are for a 70mm application, but only the numbers are different for the 50 mm jets.
www.pulsrate.com



More later.
Gary
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Last edited by efflux RC; Sep 06, 2012 at 05:14 PM. Reason: spelling
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Old Sep 06, 2012, 05:29 PM
efflux RC's Avatar
United States, CA, Santa Clarita
Joined Aug 2009
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............. For a higher top end, I'd go with around 75% FSA. Claus XPF has written plenty on intake and thrust tube design. Do a search if you'd like to read up on it.
A mylar thrust tube in general will provide a smooth, interupted flow of air from the fan to outlet of the jet. Many foamies have mold bumps, gates. and depressions in the thrust tube area. The tube will elimate all that.
I suppose for some of you, and for some air frames, just a foam or plasitic cup on the end would work as well. It depends on the look your after with your jet as well.
Keep in mind that Claus recommends that the diametrical reduction angle, be not more than 7 degress per side. Or you will induce excess drag within the tube.
Squeezing down the thrust tube will increase the efflux velocity (top end speed) but at the same time, it will reduce your static thrust. (reduced acceleration, and vertical performance.
Reducing the outlet dia (FSA) will also raise the amps a bit. so when making tubes with reduced outlets, be sure to bench test with a watt meter to be sure your amps are not more than you can deal with (IE: Battery capacity and C rating, as well as your ESC's capability.)
If your nuts, and looking for all out speed, some ( cough, ) have reduced them to less then 75% FSA, but it's up to you to decide the final outlet FSA and what your goal is.
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Last edited by efflux RC; Sep 06, 2012 at 05:39 PM.
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Old Sep 06, 2012, 07:52 PM
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After i get used to this f9f in stock setup i will give these tube mods a try..seems pretty simple to do..i am thinking a sheet of lexan would work also..thx
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Old Sep 08, 2012, 02:58 PM View Post
Bajora
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Old Sep 08, 2012, 05:22 PM
Augermeister
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United States, TX, Keller
Joined Jul 2011
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Just placed an order for the Katana with Hobbyb. Can't wait. Did I see a rudder? I'll go stock at first but will look to upgrade with Efflux for the Wemo.
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Old Sep 08, 2012, 06:31 PM
cmd
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Niceville, FL
Joined Oct 2004
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Quote:
Originally Posted by dahawk47 View Post
Just placed an order for the Katana with Hobbyb. Can't wait. Did I see a rudder? I'll go stock at first but will look to upgrade with Efflux for the Wemo.
The Katana 50mm EDF does have a rudder. It is a four servo airplane. It will do knife edges, but pulls to the top (at least mine does) on both sides so l need to push considerable down elevator to get it to fly straight when knife edging. Left rolls on high rate at speed, using the fan torque to help, are too fast to count.

I launch on high rates and then go to low rate on aileron as soon as the aircraft is stable and climbing out. A breeze helps with my rather weak underhand launches.

Mine is stock, including the stock motor and 5 blade fan, excepting a 3S 1300 mAh 40 C battery. Four minutes of flight, with throttle management, yields 11.0 VDC at rest. The heavier battery makes it slightly nose heavy and I could use more elevator on landing.
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Old Sep 08, 2012, 11:45 PM View Post
Bajora
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Old Sep 10, 2012, 09:08 AM
Bajora
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Old Sep 10, 2012, 10:05 AM
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I have zero issue with those pics... I actually really like them!! LOL
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Old Sep 10, 2012, 12:44 PM
chuck
santa barbara, CA
Joined May 2009
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Quote:
Originally Posted by Bajora View Post
EDIT: My previous ”vacation” was self-imposed and not as a consequence if admin actions here.

Hmmmmm... I just got three points for "cross posting images and videos with a watermark of our Web site . 7 more and I have to go on a vacation from the site...again.

I am wondering if I should close the other 50mm thread and just let this one linked to the review thread go solo? Maybe management here can make the call?
seems like having 1 thread makes sense, unless i am missing something. fwiw.
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Old Sep 10, 2012, 06:28 PM
Augermeister
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United States, TX, Keller
Joined Jul 2011
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Jon,

Maybe I'm just naive but what have you've done wrong? If providing great insight and help to the flying community out there , especially regarding the JPowers series is doing something wrong, then I'm really baffled. I truly have benefited from your reviews and advice.

Hawk
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Old Sep 10, 2012, 07:07 PM
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United States, CA, Santa Clarita
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Jon, I thought you did reviews for RCG E-zone, didn't you?
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Old Sep 10, 2012, 07:58 PM
cmd
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Niceville, FL
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Bajora's pictures look just fine to me.
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Old Sep 10, 2012, 08:02 PM
MultiCopterPilot & Film Maker
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United States, CA, San Ramon
Joined Nov 2002
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The pictures looked fine but the branding is what caused it. At one time I had "MultiCopterPilot.com" under my user name and it was flagged and I got a "point" against me too. I think they want you to pay $$$ for the special accounts if you're going to post branded stuff.
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