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Old Nov 18, 2010, 11:21 PM
speedin n da weeds :)
sikky's Avatar
USA, AZ, Glendale
Joined Feb 2008
595 Posts
That fan may be more weight than the less thrustof the changesun fan. Thank about the amp and battery.
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Old Nov 19, 2010, 12:02 AM
Gilbert, AZ
chalmrast's Avatar
Gilbert, AZ
Joined May 2007
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Quote:
Originally Posted by Steph280 View Post
Rolf that is a beautiful plane, an inspiration for me to work on the CMP kit.

I'd love to see your video if you could open it up. Better yet, put it on vemeo to avoid all those silly music censorship.

Got a HET 700-2085kv motor coming which will run on 6S. Problem is, it doesn't fit in the wemotec fan I have. So I need to source one of those new HET 90mm fan.
EJF Has your fan.

http://www.ejf.com/index.php?main_pa...Path=82_80_187
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Old Nov 19, 2010, 12:16 AM
Gilbert, AZ
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Gilbert, AZ
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Originally Posted by jonnyspeed View Post
I am thinking of using an RCLander 90mm aluminum fan on 6s. It looks like it puts out up to 3Kg thrust which is .5Kg more than the Changesun. It is more expensive though. Thoughts and recommendations? I fly from grass so I am looking for light weight with high thrust. I don't have a 90mm fan so I am open to suggestions.
As stated above... you can't get somethin' for nothin' so the power to make that extra thrust has to come from somewhere. Keep in mind the thrust data for the ChangeSun fan is based on a 1900kV outrunner. The fan is capable of alot more... given different motors and cell counts. If you went with a higher kV motor I'm sure you'd get that extra thrust but your amps will go way up....

It's all about finding that sweet spot between thrust, amps, and Efflux.

Here are some economical 6S combos I know work well:

- ChangeSun Fan with a 1900kV outrunner (Scorpion or Hyperion 3026-1900, or generic motor included in combo).
- Haoye 6 Bladed Fan with a 1900kV outrunner.
- HET 9305 with a 1900kV outrunner.

These will pull 70-80A and put out about 1700-1800watts. I predict based on experience with similar-sized models of similar construction you should see a top speed of 100 to 110mph.

The exhaust nozzle should be choked down to at least 76mm but no smaller than 72mm.

All of this info comes from my own models and other buddies' that I fly with...

KEEP IT LIGHT!!!

My buddy is coming over on Sunday and bringing an extra ChangeSun fan/motor combo he has laying around. We're going to test fit it in and he may let me buy it off him so I can get going!
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Old Nov 19, 2010, 11:39 AM
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North Royalton, Ohio
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Thanks chalmrast. I notice that all 3 of your recommendations are outrunners. Do you prefer those over say a 36mm inrunner in the ChangeSun fan? I read somewhere that using an outrunner with the CS fan is problematic because of the oval shape of the mounting holes which could allow the motor to shift and rub the fan. An inrunner seems like it could be shimmed inside the housing and seems like it would be more secure. Just curious.
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Old Nov 19, 2010, 11:52 AM
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Irvine, Calif USA
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Originally Posted by Steph280 View Post
... Will we see maiden flight before end of the year?
I sure hope so ... I can't see any major issues with this jet as far as building and flying it.

The only concern I have is beefing up the main gear mounts. If they break then that would punch an ugly hole theough the top covering ... The nosegear mount on the other hand cannot really do much damage if it cracks a bit, just glue it back.
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Old Nov 19, 2010, 11:57 AM
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Irvine, Calif USA
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Originally Posted by RO1 View Post
... Since about 2 years I got the " T 45 - fever " ... This CMP Hawk is also very tempting and exciting to watch this thread . I look forward to your maiden !

I agree with you using 6 S giving you plenty of power and speed . ...

Neu Motors , ARC , Mega and also the new HET motors cope quite well with this performance .

Herb, do you think that the nice little aluminum struts you might be using can stand up to the weight of this Hawk ...
Rolf, very nice pictures of your T-45, thanks for sharing !

I agree lighter is better with this airframe. The comparison with the Schuebeler Hawk (same size & weight range) is very relevant.

Yes those little aluminum HK struts look a bit flimsy for a 7lbs plane ... I think will start out with nice Springair steel struts with a good sized coil
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Old Nov 19, 2010, 12:09 PM
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Irvine, Calif USA
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Originally Posted by Steph280 View Post
... Got a HET 700-2085kv motor coming which will run on 6S. Problem is, it doesn't fit in the wemotec fan I have. So I need to source one of those new HET 90mm fan.
Yes I was looking at the HET 700 motors and liked them so much I got one

One of the problems I was facing is that most of my 90mm fans don't take the larger 36+mm motors.

The only options I was looking at the other day was Arc 36-75 (nice motors but limited choice of winds & weights) or Neu 1415 (only JHH stocks the open-endbell EDF version at a whopping $30 surcharge), and I am not in a Neu mood these days after the 1515-1.5 shorted out in my MiG-21 on 9S.

So I went with the HET 700-68 (kv=1500, 330g, can diam 39mm) from EJF which looks like a pretty efficient motor , at least on paper based on the claimed motor constants. The latter should work well on 7S or 8S cells.

I also go the HET 9305 v2 fan to go with it...

.
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Old Nov 19, 2010, 12:21 PM
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Irvine, Calif USA
Joined Feb 1999
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HET 700-68 kv=1500 in Midifan (where it does NOT fit). The 90mm HET fan is a bit softer.

http://www.highendrc.com/index_ecat.php?cPath=4_30

http://www.highendrc.com/index_ecat.php?cPath=31

http://www.s4a.ch/eflight/fancalc_e.htm

.
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Old Nov 19, 2010, 01:23 PM
Gilbert, AZ
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Gilbert, AZ
Joined May 2007
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I am hoping that rvincent is over at the AZ Jet rally now with his T-45. I will be out there tomorrow with cameras in hand for pics & vids if he is flying it.

I am not partial to outrunners, there are the only one's I have experience with. I just started getting into EDF's this year. I do know that the Scorpions will run hotter and in some cases will melt the housing at the front of the motor! Others have put some insulating material between the motor to stop this. Old PCB seems to work.

I am leaning towards trying these retracts.

http://www.rcgroups.com/forums/showp...5&postcount=46

http://rc-castle.com/shop/product_in...oducts_id=1695

Either that or the E-Flite .15-.25's....


Also, I just realized last night that I never received the servo covers for the elevators. I did get some weird vacuum-formed piece of plastic that may have just been some scrap piece that accidently got packed instead of the correct items...

I'll see if Nitroplanes can send me some... I'm sure they've parted one out by now. If not, I'll figure something else out...perhaps some balsa & covering or something
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Old Nov 19, 2010, 03:02 PM
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Portugal, Lisboa, Sintra
Joined Feb 2010
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Im using a ARC 3665-1, 2080KV,wemotec midifan,on 6s 4000mha 30c, producing 102Amps, 2300Watts, and 3,6kg of trusth.
the motor weight is 300g. Is a god choice for 6s.
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Old Nov 19, 2010, 03:44 PM
1.21 Gigawatts!
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Irvine, CA, USA
Joined Oct 2000
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That sounds comparable to the HET 700-60-2085 I'll be receiving. Hopefully my batteries will survive those repetitive 100 amp runs!
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Old Nov 19, 2010, 04:06 PM
RO1
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Rolf, very nice pictures of your T-45, thanks for sharing !

You are welcome

A very light fan set up on 6 S would be a Midi fan and the Scorpion HK 3026 1900 rpm ( 193 g - 6,9 ounces ) you would have to grind out the inner tube a bit and epoxy a 1 mm thick carbon mounting plate with eg. V-Poxy onto the existing plastic mounts . I have been using already two of those set-ups for over 2 years now in two 3 kg ( 6,6 lbs ) Mirages and still performing flawlessly . Installed I get around 2700 g or 96,4 ounces of static thrust on 79 amps . However keep in mind I am at a hight above sea level of around 450 m !

Unfortunately , the fans where those bigger motors fit are usually the more expensive ones such as Aeronaut TF 2000 , DS51 , Vasa 90 and I think Tam`s one as well .
Why not making a hybrid out of the shroud of the ChangeSun and using whatever rotor that suits best the purpose - I do that all the time

By the way , the pics I posted earlier showing two different T 45s - number 215 is Schübeler and number 262 is JTM which I hopefully can maiden tomorrow .



To give you a working idea for a fool-proof slow landing approach on maiden - tip stall is dramatically reduced


Rolf
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Old Nov 19, 2010, 04:14 PM
RO1
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Just found two pics of the Midi / Scorpion set-up .
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Old Nov 19, 2010, 07:53 PM
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North Royalton, Ohio
Joined Jan 2002
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Quote:
Originally Posted by Infante View Post
Im using a ARC 3665-1, 2080KV,wemotec midifan,on 6s 4000mha 30c, producing 102Amps, 2300Watts, and 3,6kg of trusth.
the motor weight is 300g. Is a god choice for 6s.
Wow.. that's a lot of AMPs. I am wondering if 6s or 8s is the way to go. I wan to keep the amps down. I would rather have more flight time than max speed. I can't stand flying for less than 6 minutes. A lot of setups I see are around 4 minutes of mixed flight, but that just gets on my nerves. I don't want to go up and buzz the field a couple of time and then have to land. 6 min is my minumum. So I'm looking for a combo that will get me off of a shor grass field and keep me up for 6+ min. 100mph is enough for this plane for me. Now to find the winning combo
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Old Nov 19, 2010, 07:55 PM
Gilbert, AZ
chalmrast's Avatar
Gilbert, AZ
Joined May 2007
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Quote:
Originally Posted by jonnyspeed View Post
Wow.. that's a lot of AMPs. I am wondering if 6s or 8s is the way to go. I wan to keep the amps down. I would rather have more flight time than max speed. I can't stand flying for less than 6 minutes. A lot of setups I see are around 4 minutes of mixed flight, but that just gets on my nerves. I don't want to go up and buzz the field a couple of time and then have to land. 6 min is my minumum. So I'm looking for a combo that will get me off of a shor grass field and keep me up for 6+ min. 100mph is enough for this plane for me. Now to find the winning combo
I think a 6S, 70-75A WOT setup will get you there with 5000's....
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