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Nov 07, 2005, 02:40 AM
Smokin'!
3D-kid330's Avatar
Thread OP

Robbe Folland Gnat


Hi guys,

We have an EDF Gnat (made by Robbe, sure most of you might know of this plane) that we picked up this weekend in great shape. We bought it with a fan and servos installed. I have no idea what fan and motor it is, all I know is that it's a brushed motor and the fan has 5 blades. If you know what fan it is and what speed controller would work(pictures of the Gnat and the fan below), I would appreciate it greatly if you could let me know.

I also have a Hacker E-49, which can be found here:

http://www.horizonhobby.com/Shop/ByC.../Default.aspx?
ProdID=EFLM3005

Do you know if this would fit the fan? (if somebody can identify the fan)

A few Quick questions about the Gnat for those who know about this specific airframe:

Do you know if it has a spar? (don't want to fold up the wings now do we )

How do you attach the bottom hatch that allows access to the fan? (Sorry if I might have overlooked it in the manual, I'll go look again )

Any help will be greatly appreciated!

Brandon Kontorinis

Here are the pics:
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Nov 07, 2005, 02:44 AM
That looks like the Kyosho Fan with probably an AP29L brushed motor, If you plan to use that fan i would recomend taking the spinner off since they tend to crack and explode and replace the motor with a brushless motor like a mega 16-15-3.

As far as the plane goes, I don't have any experiance with it, but i'm sure someone will chime in.

Gene
Nov 07, 2005, 02:49 AM
smug in granny panties
monkamarm2000's Avatar
might be the stock Rojet in it. A good upgrade is a Kyosho fan or just the KY rotor. And thats not a good fan motor. Look for something like a Mega 16/15/3 or Astro 05 motors work well in these. Mine has the Kyosho fan and a Astro 05 and works well on 3s or 10 cells.


Barry
Nov 07, 2005, 03:37 AM
smug in granny panties
monkamarm2000's Avatar
lol gmta Gene!

Oh and no spar in them but around 450 watts or so you should be alright.


Barry
Nov 07, 2005, 06:09 AM
That's definitely not the Rojet (four blades)
Here's the Rojet


Seems to be the Kyosho fan, will work decently as said with a 3000 Kv brushless motor on 10 cells.
Nov 08, 2005, 12:19 AM
Smokin'!
3D-kid330's Avatar
Thread OP
Thanks Guys! Do you think my Hacker E-49 will work in it? I don't have both of them in the same place right now so it's hard to say.

I have been debating whether to just try it on the brushed motor first. But, I have never handled an Electric ducted fan before, so any input on that would be great. (I feel like a newbie again, lol)

How many amps for a speed controller would work? (for the brushed or the brushless like the Mega)

Do you think it will be OK without spars?

Sorry about the load of questions

Thanks,
Brandon
Nov 08, 2005, 10:34 AM
Big gov never Works
St. Martin's Avatar
The KY fan was a drop in fit for the Gnat. The AP29L in this fan is only good with 8 cells, or the mtr does not last. If a lipo was used, a 2s would be too little, and the 3s too much. Not familiar with Hacker mtrs. If you do use the AP29 you will need a 40A ESC for 8 cells.

As far as the plane goes, I had two. The first one the wings folded pulling out of a dive. The secound had dowels in the wing, plus I glassed the area around the wing/fuse joint. The secound had a minifan and a Plett 200-20-6 on 10-1300 cp. The first used the KY and ap-29L on 8-1300cp. It was actually much easier to hand launch the KY version. The minifan required a good head wind to launch, but was faster.

If I had another, I would use the KY fan you have, but use a mega 15/3 and a 3s lipo. It would be lighter than the 8 cell version. The Gnat was a very early EDF design and simplicity/lightness the best for good flyability.

Steve
Nov 08, 2005, 10:44 AM
Big gov never Works
St. Martin's Avatar
BTW.. I used packing tape to hold on the hatch. Run it along the seam. You can put some on the fuse bottom for scuffing resistance. I had one KY spinner blow apart. This on my first T-33. I did not use it after that. But, on 8 cells and the AP29L there is not much worry. Balance the rotor by turning the spinner in icrements. Using only half power till it is nice and smooth. Then mark the spinner and rotor so you can put it back in the correct position, should you change mtrs. I use White-Out correction mask.

Steve
Nov 08, 2005, 10:59 AM
Registered User
Quote:
Originally Posted by 3D-kid330
Thanks Guys! Do you think my Hacker E-49 will work in it? I don't have both of them in the same place right now so it's hard to say.
If I have the right motor in mind this is a small purple finned motor sold by E-flite with the hacker name on it. This is a park flyer motor and not suitable for the Kyosho fan or the Roject for that matter. It's OK up to about 100 or maybe 150 watts, not 300 - 500.
Nov 08, 2005, 06:40 PM
Lithium Member
Herb's Avatar
Quote:
Originally Posted by 3D-kid330

Do you know if it has a spar?

How do you attach the bottom hatch that allows access to the fan?
The Robbe Gnat needs two short ply spar stubs to make sure the wings don't come off, all the ones I have seen had that simple mod done.

The bottom hatch is simply glued with silicone, two-sided tape or just a few pieces of tape. The fan must be glued with silicone securely to the fuse.

The Kyosho fan (or just the Kyosho rotor in the Robbe fan) works very well in the Gnat.

A Mega 16/15/3 or similar speed 400-sized brushless (Himax, Feigao, Kontronic, Hacker etc) with a Kv of around 3500 on 3S LiPo cells will work very well. Ours used to fly on NiCd's (see video ).

Here's more info on the Gnat:

https://www.rcgroups.com/forums/show...ighlight=Gnat+
Nov 08, 2005, 07:20 PM
smug in granny panties
monkamarm2000's Avatar
Herb that Gnat is still alive and well! lol although its due for a freshen up.


Barry
Nov 08, 2005, 08:00 PM
Lithium Member
Herb's Avatar
LOL, it's still a nice flier with the right setup :

Robbe Gnat tears up the sky video.

I stiil miss mine, Phil have you made up your mind yet on your Gnat NIB ...


Here's a picture of HWE's masterpiece:

Nov 10, 2005, 01:15 AM
Smokin'!
3D-kid330's Avatar
Thread OP
Wow, it looks like a nice flyer from those videos! Herb, what motor was used in your video? It seemed like it got up to a good speed pretty quick. In the video with the Astro 05, it sounded great, about as close to a turbine as I have ever heard a DF. What motor do you guys recommed for the best performance? (and sound of course) (The Astro or the Mega, or if there is a better choice, let me know)

Our Gnat is set up with 4 servos; one per aileron and one per elevator half, so I can expirement with mixing if I want to. But no rudder though. I don't know much about this particular Gnat, so I am not sure if it is OK without rudder.

Also, around the servos, there is an opening that goes into the ducts on each side. (Check out the pics) What do you guys think it's for?

One more thing, since I did not build the Gnat, I don't know if there are dowels in the wing. I could just glass it, but do you think that would be enough? (any input on how to do the dowels or whether it is strong enough would be great)

Thanks guys!
Brandon

Here are some more of the pics of our Gnat:
Nov 10, 2005, 02:03 AM
smug in granny panties
monkamarm2000's Avatar
you could always slice it form underneath the wing and insert some 1/8th ply stubs.


Barry
Nov 11, 2005, 01:47 AM
Smokin'!
3D-kid330's Avatar
Thread OP
Yeah, I think that's what I will do. I might give it a light glassing around the wing joint to be safe. I will also clean up the covering a bit and make it look nice.

It also seems like the stabs are just glued on with no stubs/reenforcement. Think it's ok or should I reinforce that too?

As for motor, I like the sound of the Astro 05 in one of Herb's videos. Will that give me good static thrust and overall speed like the Mega? I think I will go for some high discharge 3s lipolys like what FlightPower (Duralite) just came out with. We also have a 40 amp Jeti brushless ESC that I could share between the plane it is in now and the Gnat.

Again, sorry about the large amount of questions.

Thanks,
Brandon


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