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Old Jun 21, 2011, 10:13 PM
CV-15 VB-16
giuseppi's Avatar
USA, TX, Friendswood
Joined Jul 2007
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Quote:
Originally Posted by mcross View Post
giuseppi
Make sure your intake is smooth. No radical changes in area from the intake to the fan blades. The fan needs clean air that is not turbulent.
That has to be the problem. Inside the nacelle it swells then tapers back to the front of the fan.

You can see from the side view of the nacelle the inlet has a smaller diameter which increases as it goes back, then tapers as it continues back. The air must be getting stuck in that bulge.

I cut a rectangular slot from each side where the nacelle and the fuselage connect, approximately 6mm (1/4") X 16mm (5/8"). The slots are ahead of the fan but are behind the bulge. I then tested on the stand. The readings were in the low to mid 70g, an increase of 20g thrust w/o the slots.

Also, the battery was down to 7.75v during the test so I expect the thrust to increase more with a full charge.

I was also theorizing a straight tube, like a thrust tube but in front would produce a similar result. I think your diagram bears it out.

Fun, fun, fun!

g
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Old Jun 21, 2011, 10:16 PM
CV-15 VB-16
giuseppi's Avatar
USA, TX, Friendswood
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Those are some real beauties, Bill.

g
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Old Jun 21, 2011, 11:14 PM
It's a spiderweb of knit lines
Souderton Pa. USA
Joined Mar 2002
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Diagram is not mine, someone here posted it years ago.
Try a tube from the intake to the fan. What is the intake area?
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Old Jun 23, 2011, 09:36 PM
CV-15 VB-16
giuseppi's Avatar
USA, TX, Friendswood
Joined Jul 2007
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After doing some reading about intake ducts I've concluded that it isn't possible to both retain the nacelle's shape and accommodate the required 100% ~130% FSA required.

Since reclaiming some of the lost thrust by venting the nacelle I decided to add more venting to see if the rest can be recovered. I didn't want to just cut holes or rectangles etc. so I did them in the shapes of Wehrmacht markings. Swastika each side and Balkan Cross on top.

Haven't tested yet to see if they help.

g
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Old Jun 24, 2011, 11:09 PM
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United States, PA, Grove City
Joined Jan 2011
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Quote:
Originally Posted by mcross View Post
Diagram is not mine, someone here posted it years ago.
Try a tube from the intake to the fan. What is the intake area?
Probably from Klaus Scharnhorst of Winmodles, who posts here under "Winmodels". Good source of info for folks here.
I've used his diagrams for thrust tube design. Most recently used his info on the SaroA1. Seems to work well. We'll see if I ever get around to flying it.

My Salamander flys well, but I have the ugly non-tapered intake. Yours looks better. Giuseppi, I'm not sure if you've done it or not, but you can always open up a cheater hole between the nacelle and the inner fuselage. As long as the fuselage is not 100% sealed, it will help draw in more air to the fan. Nobody will see the hole, so it does not look bad. I did that with a Starmax HE162, and also used the air to cool the ESC in the fuse, which would otherwise have poor cooling with their original design. I opened an airpath from the vented battery door to the cheater hole.
Bill
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Old Jun 25, 2011, 12:12 AM
CV-15 VB-16
giuseppi's Avatar
USA, TX, Friendswood
Joined Jul 2007
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That's a great idea. There's an opening between the nacelle and the fuselage where the ESC/motor wires connect that was left open. I almost closed it up a couple of times, but didn't, and now I know why. Wonderful idea, Bill!

g
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Old Jun 26, 2011, 08:11 PM
Supersonic hover
Esprit440's Avatar
Michigan, United States
Joined Sep 2003
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Hi Giuseppi,

You will see a big improvement in static thrust if you can move the fan all the way to the front of the nacelle - no intake duct at all is best, particularly with these small fans.

Model looks great, good luck with it.

-Matt
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Old Jun 26, 2011, 11:29 PM
CV-15 VB-16
giuseppi's Avatar
USA, TX, Friendswood
Joined Jul 2007
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Hi Matt. Thanks for the information. Tried twice to build one of your 40mm F9F's but came out on the heavy side both times. Think I'll try a 30mm next time.

Is there a simple rule of thumb pertaining to thrust per pound or ounce or gram for an EDF Jet to fly?

I really think my thrust problem exists in that the design of the nacelle, with an inlet of about 85% FSA, needs to be closer to 130%.

I really like Bill's solution which will also flow some fresh air over the electronics. Just haven't gotten around to it yet. I'm also waiting on LiPos I'm gonna build 3S packs out of.

Any of you motor winders feel like answering a couple of questions?

I've got an 1811-2000 outrunner. If I reduce to 6 magnets does the kv double to 4000?

If I rewind to say 9 winds of 30ga wire and go 3 to 1 gearing ( 6 magnets ) approximately what kind of kv can I expect with wye termination? With delta termination?

Thanks in advance,

g
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Old Jun 29, 2011, 05:21 PM
CV-15 VB-16
giuseppi's Avatar
USA, TX, Friendswood
Joined Jul 2007
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No new info on the Heinkel. I received the 240mah batteries I ordered then realized I'm out of 2R Micro Deans connectors.

I do have something interesting to show from GWS. Maybe y'all are wise to it already but it's new to me. I purchased a GWS 40mm EDF Power System with the CN12-RLC motor. I bought it to use with one of the 8 blade fans HK has.

Anyway the interesting part is in the rotor and adapter that came with the assembly. The adapter has a set screw 180 either side of the adapter to hold it to the motor shaft. The adapter itself has two flats on one end that match a recepticle cast in rotor and the end with the set screws OD matches the ID of the rotor skirt. The tip of the adapter is threaded for a machine screw to hold the rotor. It makes it virtually impossible to attach the rotor off center.

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Old Jul 03, 2011, 01:27 PM
CV-15 VB-16
giuseppi's Avatar
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Well. I ripped it apart for the guts and will return for another go some time in the future.

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Old Jul 03, 2011, 07:47 PM
Not enough hours in the day
Slaanesh's Avatar
Melbourne
Joined Feb 2009
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Did you buy that GWS 40mm fan recently from HK?
Also, do you have a photo of the housing that came with it?
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Old Jul 03, 2011, 11:22 PM
CV-15 VB-16
giuseppi's Avatar
USA, TX, Friendswood
Joined Jul 2007
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Quote:
Originally Posted by Slaanesh View Post
Did you buy that GWS 40mm fan recently from HK?
Also, do you have a photo of the housing that came with it?
Yeah. It came from HK. I may be able to tell you what you want to know about the housing. Let me know.

I'll try to post some pics of it tomorrow.

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Old Jul 04, 2011, 12:34 AM
Not enough hours in the day
Slaanesh's Avatar
Melbourne
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Actually, yes, text will probably do.
Is the housing designed for a 12mm motor or 20mm motor?
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Old Jul 04, 2011, 12:56 AM
CV-15 VB-16
giuseppi's Avatar
USA, TX, Friendswood
Joined Jul 2007
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It's actually designed for both. It comes with a 12mm installed but will accept a 20mm. As a matter of fact, I stuck one of the Mini J-Power 50mm stock motors in it and mated one of the 8 blade fans to it. Haven't done any testing on it yet, though.

I'll post some pics later today.

g
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Old Jul 04, 2011, 01:14 AM
Not enough hours in the day
Slaanesh's Avatar
Melbourne
Joined Feb 2009
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Okay that's what I thought. It must be the version 2 housing then. Thanks!
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