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Old Dec 14, 2009, 07:19 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,716 Posts
Discussion
K + A F86- a microfan airplane at long last...

I've been rather enamored of microfans if the number I have lying around is any indication, but I'm sad to say, I've never flown an airplane that had one in it. Until today that is.

The short version- the airplane is much faster and climbs better than the Vasa or 505 version I built a few years back- at least if my recollection has any degree of accuracy. It's also lighter- not surprising. I was a bit nervous on this first flight since I'd had some issues launching the first airplane- but after one false start, we had a good launch. (I had a buddy launching.) We discovered that the airplane does not need much of an "up" preset- and likes a level launch with some time to get up to speed. Once it's on step in about 100 feet it has a very nice climb rate. I kept the speed up and the climb was effortless- a bit different than the first version! It's quite fast- I suspect a good chunk faster than the Alfa version which I've seen fly a year ago. I brought it in a little hotter than I should have- need to see what the stall is like, but I suspect it'll be fine.

The longer version-

A year ago, I asked Ken of K + A to lay up a lighter weight fuse for me and he obliged quite willingly. Coupled with a somewhat lighter weight glass sheet for the intake duct, I managed to come out with a 24 oz airplane ready to rock. I "borrowed" an idea from Paco (aka Rover Tomcat) and mounted the fan in a bulkhead rather than having it suspended between the intake and the exhaust. I also went to 1/32" sheet on the wings applied with Gorilla Glue- light and stiff. Don't sweat putting Doculam on the wing, the core doesn't melt- the wood is a pretty good insulator. I'm just a slow builder, so it took until today to try the airplane out. The fan was spun by an Astro 015 which may be THE motor for a microfan in the 250-300 watt range- a bit more watt handling capability than the 010 and lighter than the 020. Power was provided by a pair of 2s 1250 packs in a saddle arrangement and in series. A 4s 1550 didn't quite fit under the canopy without impinging on the duct, but maybe I'll try it in a bit. When installed in the airplane, I saw 260 watts at 15.0V- which I think was a slight drop from the amp draw without a duct- although it could just be a smaller pack. (Pretty sure I saw 300 watts with a fat pack before installation.) Using a Phoenix 25 with a BEC, so there's a fair amount of spaghetti in the installation.

Launching was much less eventful than before due to several reasons-
1) Lighter weight (about 4 oz or so- but overall watts are pretty close IIRC)
2) The bulkhead gives a hard point to grip on.
3) Don't need to give it a vigorous chuck- just a normal launch. Today was about as bad as you could get- basically windstill or 1-2 mph at best.
4) I'm pretty sure that the Microfan is in a sweet spot at 250-300 watts- whereas the Vasa 65 and certainly the Wemo 505 want more watts to be happy.

For the incurably power mad- may I suggest the Hoffman Mini Mite? The motor will put out 550-600 watts and I'll bet the airframe will take that fine. Launching may become a bit more challenging with the added battery weight and I don't know if the ducting can take that load. But you will have an airplane that will go very, very fast....Make sure you use an HS-81 on the stab (I did.)

So for those folks who've been looking wistfully at the microfans in their drawer, wondering what to do with them- the K + A F-86 and the Mig are just the ticket.

Sam
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Old Dec 15, 2009, 07:23 AM
Effumall
kelberts's Avatar
Joined Nov 2005
3,619 Posts
How about some pix??
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Old Dec 15, 2009, 08:22 AM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,716 Posts
My girlfriend cleaned up my computer, but unfortunately, my camera cable seems to be missing. Besides, the airplane looks pretty much like the first one I built.


Sam
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Old Dec 16, 2009, 02:03 AM
Zoom-Zoom
RoverTomcat's Avatar
Switzerland, ZH, Dietikon
Joined Jun 2004
815 Posts
Hiya Sam!

Quote:
"borrowed" an idea from Paco (aka Rover Tomcat) and mounted the fan in a bulkhead rather than having it suspended between the intake and the exhaust.
Wow, I feel quite honored!

I might want to follow your idea someday - light and less power hungry setups seem to be the ticket for good flying planes.

Best regards - Paco
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Old Dec 16, 2009, 08:36 AM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,716 Posts
Hi Paco

See- immortal fame and fortune are yours when you post your ideas on RC Groups for everyone to look at (aka steal)! Good to hear from ya...

There seems to be some divergence in trends these days. Going with smaller and lighter fans although really, I didn't drop down in watts from the 505 fan powered airplane, does make sense when it allows you to get to a more efficient range of the fan. Clearly a lot of early setups were optimized for thrust with what was available, and we've now got higher power densities.

The second trend is to use a lot more watts than was thought possible in some of the standard fans. Who'd have thought that you could put ~ 1500 watts into a Minifan? I'm assuming that there's some weight gain over the 700 watt setups a few years ago- I haven't done one yet.

Cheers,

Sam
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Old Dec 16, 2009, 09:59 AM
Team White Llama!
gundamnitpete's Avatar
Joined Jan 2008
8,144 Posts
Quote:
Originally Posted by Megowcoupe View Post
Hi Paco

See- immortal fame and fortune are yours when you post your ideas on RC Groups for everyone to look at (aka steal)! Good to hear from ya...

There seems to be some divergence in trends these days. Going with smaller and lighter fans although really, I didn't drop down in watts from the 505 fan powered airplane, does make sense when it allows you to get to a more efficient range of the fan. Clearly a lot of early setups were optimized for thrust with what was available, and we've now got higher power densities.

The second trend is to use a lot more watts than was thought possible in some of the standard fans. Who'd have thought that you could put ~ 1500 watts into a Minifan? I'm assuming that there's some weight gain over the 700 watt setups a few years ago- I haven't done one yet.

Cheers,

Sam


you can put up to about 2100-2200 watts into a minifan before you cook the goose
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Old Dec 16, 2009, 10:09 PM
Cant fly enough
Greg Beshouri's Avatar
USA, CA, Berkeley
Joined Dec 2003
1,816 Posts
Hi Sam and Paco,

Pretty cool idea. Start with a light weight set-up. That let's you use a light motor and batteries. 4s only helps. Ken has certainly exploited this approach on his FW-190 (which I am slowly building http://www.rcgroups.com/forums/showthread.php?t=672985) and P-51.

But let me explore my ignorance. We are discussing a Wemotec Mircofan? Isn't that just 50mm? How do you set up int inlet and discharge ducting?

Cheers

Greg

PS: Paco, I still need to install that VASA 65 in my repaired Mig-15. Too many planes, not enough time! So how is the weather?
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Old Dec 17, 2009, 02:25 AM
Zoom-Zoom
RoverTomcat's Avatar
Switzerland, ZH, Dietikon
Joined Jun 2004
815 Posts
Hiya Guys,

in my opinion, one of the "other" benefits of using smaller fans (but - like Sam mentioned with the same amout of watts) is that the planes can have more scale air inlets. For that, I do like the DH Vampire by Vasa Models very much. It's a big plane (39.5" WS) that uses a 65mm Fan. Hey, presto, scale inlet geometry.

One of the best flying EDF's I had was the foamy (spit!) F16 by Phase3. It had an Alfa 60mm fan, Hacker B20-12-L motor and 4s 1800MAh battery. The drivetrain was just collecting dust in the basement, so I thought I'll put it into a cheap airframe.

I was amazed by how well that thing went, scale performance and all... Then I got myself one of those HET F16's, FG fuse, glassed wings, etc. Boy, that thing was a big dissapointment, never flew "right" 'cause it tipped the scale at over 1.3kg. I still have a spare fuse from HET, so I might put in a small-ish fan in that, glue on some F16 XL shaped depron wings and give it a try.

Oh, and Greg - I can relate to that (too many projects...)! I still need to fix a couple of planes myself...

The weather? B*ll*ck freezing cold! Icy winds... No me gusta!

Best regards - Paco
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Old Dec 17, 2009, 02:44 AM
My project: FAIREY DELTA 1
Erik v. Schaik's Avatar
Uden Volkel, Netherlands
Joined Dec 2003
4,976 Posts
I've been using smaller fans for years now and they have a lot of scale potential in larger frames!

The original Lubach F16 was a full fibre Het-rc F16 which was only 400gr empty. ROG my version was in the 900gr range. I'm sorry you send the cash to the wrong place on the HET. Unfortunately this Lunach isn't available anymore, but a newer version has been scaled up for 90mm which has been made out of 35 moulds . Top notch qty and it flys superb on only 6s.
Lubach F16 90mm fan (5 min 26 sec)


@sam,
I'd love to see some footage of your F86!
There is a small Het-rc micro F18 kit available at Wemotec which I'd like to build someday for my 600W microfan I have laying around from my late Viperjet.

good luck!


Erik
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Old Dec 17, 2009, 09:30 AM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,716 Posts
Hi All

Erik- I haven't managed to get video on any of my airplanes, so please don't hold your breath. I may get my camera connection to my computer to work in a week or so (heading off to visit the girlfriend.) You're another one who inspired me to try this approach with this airplane. I've got the F-18 kit- not sure it's going to handle 600 watts but YMMV. I'd put more money on either of the K+ A kits handling that kind of power- the wings are continuous and the dihedral joint is wrapped with glass. The F-18 wing attachment might need some beefing- and that's also a smaller airplane IIRC- might be a real needle in the air. The K + A kit will accommodate a pair of 2s 2500 packs- I just checked- hits 800 grams which is still a smidge lighter than my first one so it's chuckable if you're skilled.

Paco- thanks for the heads up on the HET F-16. I had my eyes peeled for the Lubach kit, but your confirming that the HET version isn't worth chasing after.

Greg

Yup- it's the 50 mm Wemotec microfan. Changing the ducting to match is not hard. I did ask Ken for a longer piece of the glass sheet he's been enclosing, think it's now a bit lighter too. Needed the extra length because I wanted to get the fan a bit further back for efficiency- also my first one was nose heavy. This one needs the batteries all the way forward, so I wouldn't go any further back with the fan. The bulkhead is about 40 mm in back of the TE. I just used a constant radius cylinder for the intake duct- when I got to the nose piece, I added an extra wrap or two so it fleshed out to the plastic piece. Little filler and some dremeling and voila! Back end is just a piece of overhead plastic (probably a little thicker and heavier than Ken's sheet- should have used that instead.) taped to the fan. It's not a tough installation. The smaller fan gives you more room inside the airplane- don't have to grind out the top of the wing.

HTH

Sam
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Old Dec 17, 2009, 11:43 AM
Cant fly enough
Greg Beshouri's Avatar
USA, CA, Berkeley
Joined Dec 2003
1,816 Posts
Thanks Sam,

I really like this idea.

What exist diameter are you using to get the correct Efflux? If you scale form the 65mm fan it is about 44 mm?

Cheers

Greg
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Old Dec 17, 2009, 12:08 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,716 Posts
Hi Greg

Umm, mine is bit oval (well, it sure ain't perfectly round!) and its about 40mm x 50 mm, so it's probably pretty close to a 44 mm outlet.

Sam
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Old Dec 18, 2009, 06:52 AM
Speed Demon
GregG's Avatar
Antioch,CA,USA
Joined Dec 1999
12,307 Posts
Nice Sam!

I've always liked the looks of this one. Now that my time is so tight I hardly ever get a chance to make it out to the flying field.

I live across the street from a school that is too small for a large heavy plane to land. Any chance this one could be slowed down (on landing) enough to fly at an actual park or school ground?
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Old Dec 21, 2009, 04:11 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,716 Posts
Hi Greg

This airplane has pretty similar room requirements of any other small, fast airplane. Anything that can be handchucked should be able to be brought into a relatively small space, but the airplane doesn't lose speed easily. IIRC if you like a CSD Twister- I suspect that the room requirements are similar.

I'm not sure that all the weight saving stuff I did was all that necessary, but it did make me feel better. Ken's preprimed glass fuse was definitely nice, and if I actually buckled down to it, I could probably bat one of these out in 20 hrs or so.

HTH

Sam
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