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Author Topic: DH 106 Comet 30mm EDF  (Read 998 times)
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Bill G
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« on: August 25, 2016, 12:01:09 AM »

Finally flew this 19" span EDF Comet, after having a 3A brick ESC failure 10 seconds into the first flight.  The ESC was replaced with a 6A unit, with a diode drop on the BEC which supplies the brick.  The throttle is mixed with the gear channel.  AUW approximately 83.5gms, with a small 2s-180 Hyperion lipo.

Not the greatest video, but it flies:
https://www.youtube.com/watch?v=Ly55BD4rsfw
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DH 106 Comet 30mm EDF
DH 106 Comet 30mm EDF
DH 106 Comet 30mm EDF
DH 106 Comet 30mm EDF
DH 106 Comet 30mm EDF
DH 106 Comet 30mm EDF
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Konrad
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« Reply #1 on: August 26, 2016, 08:43:47 AM »

WOW!

Any details on the ducting? I don't see any splitters between the left and right sides (inlet or exhaust).
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Bill G
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« Reply #2 on: August 27, 2016, 01:37:35 AM »

Thanks Konrad.
If you look under the clear ducting cover, there's a blue foam splitter in the center of the wing behind the fan.  Being the 3rd Comet build, I've learned from previous examples.  What I've found is that the fan should be mounted as far forward as possible, since the thicker front wing portion is easier to cheat a bit, and have ample intake.  If anything, it's better to starve the intake a bit, as the exhaust is never quite ideal, due to the triangular duct feeds in the wings. Obviously only the thicker, front portion of the exhaust feeds is doing most of the work.  I'd like to try flying my next larger size which should have ample thrust, but I wish I could take the ducting job over again.
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Re: DH 106 Comet 30mm EDF
Re: DH 106 Comet 30mm EDF
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Konrad
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« Reply #3 on: August 28, 2016, 04:09:15 PM »

Bill,
I see it now.
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Bill G
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« Reply #4 on: October 26, 2016, 03:25:52 PM »

I got the larger 33" Comet flying recently, after tearing out the heavy, oversized fan and replacing it with a 12mm Hyperion powered EDF40 fan.  The fan entry was moved forward about 10mm for a less angled exhaust path, the exhaust was reworked with a better ducting hood/splitter, as well as reducing the outer exits, which is more efficient anyway as the airflow path to the outer exhausts is more restrictive.  The AUW is down to a hair over 11oz with an old TP 3s-730 and 5gms of ballast taped to it, which it was flown with.  The ballast proved useful to set the original CG, which it seems to fly well at.  I purchased a newer TP 3s-750, which is equal in weight to the old battery+ballast.

Flight video: https://www.youtube.com/watch?v=rApFCTXHRUY
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Re: DH 106 Comet 30mm EDF
Re: DH 106 Comet 30mm EDF
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Konrad
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« Reply #5 on: October 26, 2016, 09:11:30 PM »

Always impressive to see these fly.
EDF40 is this a GWS product? Are you happier with the repowered set? I ask, as I often improve things to the point that they don't work. Shocked
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Bill G
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« Reply #6 on: October 27, 2016, 12:58:31 AM »

Always impressive to see these fly.
EDF40 is this a GWS product? Are you happier with the repowered set? I ask, as I often improve things to the point that they don't work. Shocked
Thanks.  The model would not quite stay airborne with the heavier 55mm fan setup.  The Hyperion 12mm inrunner is a direct fit in the GWS EDF40.  I wish these fans were still on the market.  For smaller EDFs, the heavier, power hungry 2s outrunner fans seem to be all that are currently available, other than the Eflite 180 fan.  With the EDF40/12mm inrunner, I can use something like a light TBird9 ESC and 3s-480TP lipo, and have light weight and good flight times.  I've found the more powerful EDF setups to be a case of diminishing returns, unless that is what someone wants.  The 24", 8oz Yak 23 I recently built and flew is a perfect example of where these fans are practical.  Given the good performance with the same fan setup in that model, I could not see the benefits in a heavier, more powerful setup.  If it were ARFed, it would probably be 12oz.  We've both seen how the market has dictated heavier and more powerful gear, in a number of cases.  Often times people won't build light enough to make the lower powered systems work either, so they keep throwing more power at it until it flies.  I was one of those people, and have really enjoyed the benefits of light weight.
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Konrad
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« Reply #7 on: October 27, 2016, 09:13:18 AM »

The fall of GWS still dumbfounds me. I thought they were place at the sweet spot, functional, low cost, entry level products. It looks like family issue has destroyed the firm.

Back to the EDF stuff I've had problems with the GWS fans (these may be the bigger ones) when upgrading them to brushless motors. The rotors tend to stretch horribly with the resultant rub throwing them way out of balance. Are/were there improved rotors? And if so how can one identify them?
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Bill G
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« Reply #8 on: October 27, 2016, 08:36:49 PM »

The fall of GWS still dumbfounds me. I thought they were place at the sweet spot, functional, low cost, entry level products. It looks like family issue has destroyed the firm.

Back to the EDF stuff I've had problems with the GWS fans (these may be the bigger ones) when upgrading them to brushless motors. The rotors tend to stretch horribly with the resultant rub throwing them way out of balance. Are/were there improved rotors? And if so how can one identify them?

The EDF75 rotor was not robust enough for it's size.  I used one in a ducted FW190 TL (German prototype) that works well with a lower powered Align Heli outrunner, but I wouldn't put more power to it.  Their 55 and 64 mm fans work well when balanced properly, and are reasonably light.  I believe people have used other rotors in the 55 and 64mm fans, although the GWS rotors were popular, partly being known to be some of the most efficient in the size class.  The later ones with a removable, front grub screw on the aluminum center hub were the best of the bunch.

I agree about the fall of GWS.  They had small fans before anyone else.  Their mo was that they would only sell a powered product, if they could provide dirt cheap motors with it, mostly brushed, and make all the profits.  They could have made micro EDFs from the onset of decent lipos in 2005, for at least 5 years with minimal competition.  Their small 30mm fan is in several of my micros, remotored with 12mm inrunners, and with direct fit 10mm inrunners. For whatever reason, they refused to sell a small EDF aircraft as they didn't want to sell the motors along with it.  They lost on both ends by making no small EDF aircraft without BL motors included, and also refusing to bump the price up to adjust for adding a decent, small BL motor.

One of these days I'll have to video my 40mm ME262 built around '07.  Much easier to fly than the larger GWS 262, with it's light 12mm Feigao inrunners and GWS EDF40 fans.  To date, small 262s haven't been produced.  Part of the reason is that the heavier outrunner fans start to become impractical on a small twin.  They could have made small twins like it also.  If they had, people would have realized the benefits of smaller EDFs with light/efficient/3s inrunners, lighter ESCs, and batteries.  This 262 below flies with a single TBird18 ESC and TP 3s-1320 lipo.  Built more recently with modern lipos, the tail would be lighter and it would use a smaller lipo.  All of my small inrunner twin EDFs use a single Castle ESC, reducing weight even further.  Even with 2 ESCs, light weight TBird9 ESCs would be fine.
Attached files Thumbnail(s):
Re: DH 106 Comet 30mm EDF
Re: DH 106 Comet 30mm EDF
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