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Old Mar 30, 2012, 03:15 PM
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Hi Dave,

Real nice video!

What do you mean bad weather in Michigan! One of our business partners told me a couple weeks ago it was 80!
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Old Apr 02, 2012, 01:00 PM
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Quote:
Originally Posted by Dave Grife View Post
Hi Herb, ... I've been playing with some Jetfan 90 applications and I'm pleased with the sound, perhaps a Stumax sounds better but I have some time to find out. ...
Hi Dave,

When it comes to fan choice imo the two (somewhat exclusive) basic options are :

a) better efficiency and more power per watt. Which means either DS-51 or WeMoTec Midi or HET, or similar. When it comes to efficiency the lower blade count fans are clearly ahead, according to almost all figures I have seen. This has been known for while, and is the main reason for very low blade count (eg DS-51 4-blade and DS-30 3-blade) high performance fans being offered for years.

Also, the way the fan is mounted seems to account for about 80% or so of the overall noise output. I would not want my fans in the Me-262 to be any quieter.

b) cooler sound is obtained with a higher blade count and a larger rotor-stator gap, as the Jetfan 90 shows. So this is the way to go if you put more emphasis on overall "sound aesthetics".

.
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Old Apr 02, 2012, 01:06 PM
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Another very important issue to keep in mind for the Me-262 twin (which I emphasized in my previous posts in this thread regarding motor tests) is to make absolutely sure the two motors have the same kv !!

Apparently quite a few HET 700 motors were recently completely mis-labelled when it came to the KV. It is stated here that HET will replace those motors for free:

http://translate.google.com/translat........%2Fpage65

Original post (in German) :

http://www.rc-network.de/forum/showt...=1#post2743280

The efficiency estimates are not necessarily affected by those errors, only the power output is (lower kv = less power = less thrust as well).

Most people of course don't notice initially the wrong kv, as they are not powering a twin !

In the Me-262 two unbalanced motors (differrent kv) would be deadly - and indeed it was if you read the thread above where it appears to mention a serious mishap with a "2m" Me-262 ...
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Old Apr 02, 2012, 01:18 PM
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I was thinking that perhaps there's a third aspect to keep in mind : strong, and readily available replacement rotors.

The Me-262 has two nacelles which are quite close to the ground, and are therefore prime candidates for FOD ingestion on takeoff.

This is epecially true for higher powered setups where anything (stones, grass, twigs) within half a foot or so of the intake can be sucked in. Resulting in a shredded fan at least, if not a bent shaft.

Earlier this year my 90mm Hawk sucked in a small stone fragment (!!) on takeoff, it shredded the HET 700 fan rotor, and bent the HET 700 shaft destroying the motor as well.

2500W in a 90mm has a LOT of sucking power, I think that little (5mm) or so stone fragment must have been kicked up by the nosewheel on takeoff.
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Old Apr 02, 2012, 05:44 PM
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Coldwater, Mi. USA
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Hi Herb,

Excellent points about fans, sound, replacement parts.

And thanks for the tip about the HET kv problems.

I'm getting more excited about FINALLY getting this kit.

Your blog is still the absolute best build thread that I've come across (I read a few of them too !!)

I liked your Me-163 video also...

thanks,

-DG

P.S. As of 4/4/12, I am now a proud owner of an Airworld Me-262 !!
Gotta keep it light w/ lotsa Watts
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Old Apr 04, 2012, 09:37 PM
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Excellent !!
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Old Apr 04, 2012, 11:03 PM
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Wow, Where does one buy a ARF or BAF kit like this?
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Old Apr 05, 2012, 06:48 PM
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ductedfans.com is one place
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Old Apr 10, 2012, 02:58 PM
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US distributor is Vogelsang Aeroscale in Chapel Hill NC :

http://www.teamaeroscale.com/

People did at some point got it shipped directly from Airworld Germany :

http://www.airworld.de/

I got mine from a guy (JC) who bought it himself from Airworld USA (now gone).
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Old Apr 15, 2012, 01:23 PM
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Re: Batteries

Herb,

I am currently running 90mm HET fans on 2x 5000 5S lipos, but although I have plenty of power I am tempted to install 6S packs with the multi-blade Changesun fans just for the sound! Seems that I ended up nose heavy, as I added about 80g of lead in the tail (admittedly I still have to add scale detail, and will probably add a coat of clear varnish afterwards). The electric retracts seem to be a good idea, but the Robarts that I have installed are still working fine. At this stage I am negotiating to buy a second one, but it is the Turbine version which I consider to be bad idea considering how well the electric version flies! What do you think of the idea of replacing the HET fans with the Changesun ones?

As for the other question posted, placing the batteries from the top is quite easy as the ME has a large hatch. Also attached a pic of my plane at our "local" field, which is a disused field near Pretoria (called ODI) which is in an excellent condition ;-)

Regards,

Andre
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Old Apr 15, 2012, 02:26 PM
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Quote:
Originally Posted by Dave Grife View Post
Hi Herb,
Anyways, I hate to clutter up your blog with posts like this I was at the Toledo show this weekend,
I picked up my robostruts, carbon cloth/tow/sheeting , aero-epoxy gun, G-10 fiberglass, servos, etc etc. <snip>
Dave Grife
Hi Dave, not at all ... I enjoy your posts .

As far as electric retracts are concerned, I am sure they will work fine. But I'm a bit old fashioned and with such a large project I prefer to go with proven technology. I found that the Robarts air up/down work like a charm (so far) and I would not consider anything else (at this point). I don't plan to have gear doors on mine either, to keep it simple and 110% reliable.

Sorry I don't have any nosegear mount templates left, but it should be easy to make your own out of manila folder paper. If the wood parts are reasonably large and fit well, there's no need to even use heavy wood, some lightweight ply is easier to work with.

Re the batteries, no I feed them in from the front and that works fine! The thing that takes me the longest is to get that strap secured around the batteries. I have to either get on my knees, or put that monster up on a stand (on top of a table).

If there were a second hatch of some sort, it would be undoubtedly a bit easier to secure the strap(s) around the batteries. Maybe I need to work a bit more on getting all that (air and electrical) wiring out of the way as well.

.
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Old Apr 15, 2012, 02:36 PM
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Quote:
Originally Posted by electricfly2002 View Post
Herb,
I am currently running 90mm HET fans on 2x 5000 5S lipos, but although I have plenty of power I am tempted to install 6S packs with the multi-blade Changesun fans just for the sound! <snip> Andre
Hi Andre, your Me-262 look fanstastic ... and that field !!

Well whether to switch from Het to CS is a personal choice, the Het works very well but I had one which was unbalanced ... the WeMoTec rotor is exquisitely balanced and as a result very quiet. The overall rigid mounting in the nacelles, and of the nacelles themselves to the wing, plays a big role in the sound.

My experience with the CS fan can be found here,

http://www.rcgroups.com/forums/showt...1521751&pp=100

I still have one that I did not install into anything yet, waiting for large foamie to test it maybe. There were serious structural and balance issues with the design. The JetFan seems a much better engineered design, but I don't have one.
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Old Apr 16, 2012, 10:17 AM
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Can some please take some pics of how the fans are mounted and secured in their nacelles??
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Old Apr 17, 2012, 01:50 PM
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As I said before, I fabricated a ply former and then inserted that fan into the front nacelle opening.

The WeMoTec Midifan fits perfectly into the front nacelle ring, no modifications are necessary, and the fan is now supported at the back as well by the sturdy ply former, glued with hysol to the nacelle.

Due to the tolerances the fans are a nice tight fit, and have been secured with a bit of silicone.

I have tens of other edf's where I use exactly the same method and they have lasted years.

More details & pictures have been posted above:

http://www.rcgroups.com/forums/showp...2&postcount=91

http://www.rcgroups.com/forums/showp...5&postcount=99

http://www.rcgroups.com/forums/showp...8&postcount=88
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Old Apr 18, 2012, 03:36 PM
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Re: Transport

Herb,

From a practical perspective, how do you transport the wing without getting hangar rash? I have found the 2m one piece wing a challenge, and the bottom of the nacelles are very flimsy and it is not a good idea to rest the wing on them whilst transporting.

Regards,

andre
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