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Old Feb 22, 2012, 02:06 PM
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Manu Simon's Avatar
Belgium
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MRGTX

I'm running a turnigy 3025 1500 kv heli motor in mine which is pretty close to yours: With a 7x7 I metered 1010 watt static on 4S and 1686 watt on 5S.

if you want to stay in the 800w range, those prop you listed are too much. You should look for a 7x6 to stay around 800 w.



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Originally Posted by MRGTX View Post
Cool... the stats on the HK page do give some hints. It looks like this motor is capable of some serious horsepower, undoubtedly more than the Dogfighter has battery room to accommodate which might mean that it will be excessively heavy. Hoping not...

I'm planning to run it it reliably at ~800W on 4s so I can run it safely on a 60A esc...so I'll start with an APC 8x8 or APC 9x6...

Honestly, I'll be happy just so long as it's at least as fast as the 1350kv Blizzard power system (which is around 100mph, IIRC) and still handles well.

Regardless, I will share all of my findings.
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Old Feb 22, 2012, 06:43 PM
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United States, LA, Baton Rouge
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I am getting fairly close to "maiden" time with my Dogfighter (should complete build this weekend) and will be using a catapult launcher that I built based on ones I've seen on the internet etc. What I can't seem to find is a good picture or description of is where exactly to install the towhook. I realize that the DF is supposed to be easy to hand launch etc., but since this is my first fixed wing RC aircraft, and I don't often have anyone available to assist, I thought the catapult would be best for me right now and hopefully, it will eliminate at least one likely point of failure for a beginner, the hand launch. So does anyone here use a catapult to launch their dogfighter? And if so, can you post a pic of the hook location? Thanks!
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Old Feb 22, 2012, 09:44 PM
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United States, TX, Garland
Joined May 2005
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Place the hook right in front of wing leading edge on fuse.Secure it well,would glass that spot inside and out and use strong piece of wire.Remember 1 thing,the hook part that comes out of fuse needs to be very short,1/4 inch is as long as it needs to be.
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Old Feb 22, 2012, 10:56 PM
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Champaign, Il
Joined Mar 2008
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Just put the finishing touches on my DF. Are you guys happy with the CG at 68mm? I have wiggle room, I can go more or less but have it spot on at the moment.
Didn't get any power numbers. All my packs are still at storage charge. I thought I had at least one charged up for my spit but must not of charged it back up
Pics in the am.

Matt
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Old Feb 22, 2012, 11:39 PM
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United States, TX, Lubbock
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Originally Posted by fh64_lucky View Post
Place the hook right in front of wing leading edge on fuse.Secure it well,would glass that spot inside and out and use strong piece of wire.Remember 1 thing,the hook part that comes out of fuse needs to be very short,1/4 inch is as long as it needs to be.
Lucky,
have you tried the hook in this location?

I think this will give the plane a severe nose-up angle on launch.

I placed mine right under the air intake on the nose.
At this location the plane launches with a 20 degree climb with no control input needed.

Multiplex Dogfighter Catapult Launch (0 min 35 sec)
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Old Feb 22, 2012, 11:52 PM
Ginger or MaryAnn ??
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United States, TX, Garland
Joined May 2005
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Wow,I never seen a hook installed that far forwards!!!I have bungee launched ALOT of planes/EDFs but thats a first! The hook right in front of wing on fuse is good,it wont balloon up at all,you just never want to be to close to CG with the hook or it will flip up off of ramp.I would think yours would pull nose down too much,but if it works,dont fool with it ehh??
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Old Feb 22, 2012, 11:56 PM
Never fly an A model anything!
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Joined Apr 2008
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Come on Murdo, I know you can hand launch it..... What about your HiPo Strykers?.

Anyway, it's nice that you gave a shortcut in positioning.

For other models that have little or no reference, I use a method described by Stumax. I'll post the link when I can find it. It is effectively hanging the model upside down fully configured for flight with packs etc at the correct CG. The hook is temporarily attached. I use military Velcro, and re-position the hook until the nose rides slightly high... 10-15 degrees. It is also a good way to check lateral balance. J
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Old Feb 23, 2012, 12:11 AM
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Quote:
Originally Posted by jayb1rdz View Post
Come on Murdo, I know you can hand launch it..... What about your HiPo Strykers?.

Anyway, it's nice that you gave a shortcut in positioning.

For other models that have little or no reference, I use a method described by Stumax. I'll post the link when I can find it. It is effectively hanging the model upside down fully configured for flight with packs etc at the correct CG. The hook is temporarily attached. I use military Velcro, and re-position the hook until the nose rides slightly high... 10-15 degrees. It is also a good way to check lateral balance. J
Once my Strykers get over 3lbs, they get the catapult treatment!
8lbs barely gets into the air even WITH the catapult!
Torque roll is nasty, and even if 9 out of 10 launches goes well, it still beats up a plane pretty fast when it goes badly. And the heavier they are, the harder they hit.

I used a similar method as you described to set the hook on the Dogfighter.
Except I hung the plane vertically and looked for that 15 degree angle from vertical.
I got the 15 degrees by comparing the angle my successful catapulted planes hang at.
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Old Feb 23, 2012, 12:23 AM
Never fly an A model anything!
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My safety net and confidence booster for hand launching is that I launch over a field of rye which is around 2- 2-1/2 feet high. It provides a soft landing for a stuffed up throw as long as you can kill the prop in time.
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Old Feb 23, 2012, 01:11 AM
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United States, LA, Baton Rouge
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Great information guys! Seems so simple ....now! haha I just didn't know how to find the right spot but your posts made it so clear and I really do thank you for taking the time to explain it. I'll try to post a couple of pictures soon and you can judge my "high viz" paint job. It's pretty ugly but I should be able to see it a mile away!
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Old Feb 23, 2012, 05:00 AM
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Belgium
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Matt

Did you clip the wing or what ?


Quote:
Originally Posted by Pickle72 View Post
Just put the finishing touches on my DF. Are you guys happy with the CG at 68mm? I have wiggle room, I can go more or less but have it spot on at the moment.
Didn't get any power numbers. All my packs are still at storage charge. I thought I had at least one charged up for my spit but must not of charged it back up
Pics in the am.

Matt
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Old Feb 23, 2012, 08:45 AM
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Champaign, Il
Joined Mar 2008
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Yep, clipped the wings. Can't have a race plane and not clip the wings Clipped them 1/4" from the last panel line on the wingtip and added some wingtip fences. In theory a clipped wing will give you a faster roll rate and may or may not reduce drag(+speed). I read a big debate on that topic Also the wing tip fences will reduce a hard stall, increase roll rate and basically make a short wing work like a long wing without the weight and drag. But seriously I could give two shakes about all that. I just thought it looked cool
I made the fences out of some white styrene card stock I had laying around. I am not sure of the thickness but its not too thick, maybe a little thin. I cut up a large zip tie and glued a piece to the bottom of both fences. This really stiffened things up, so I am not worried about flutter. I cut the bottom off square with the fattest part of the airfoil and the top has a nice angle ending about a 1/2" above the airfoil. All just glued on to the tip with med CA.

I moved the ESC to the nose. I cut out some foam under/behind the motor in the air intake ramp. Plenty of foam to cut out and the ESC sits nicely there. OUt of the way and in the airflow.

I beefed up all control rods with CF and glued the wing on for stiffness. That's what she said

I sanded, washed the airframe. Gave it 2 coats of WBPU/micro balloons to fill in some of the foamy-ness and gave it two coats of Model Masters 1451 buffing aluminum spray paint followed by some MM gloss clear coat followed by some MM red, more clear coat, stickers, and more clear coat. Finish isn't perfect. Still looks like a foamy but its good enough from 10 feet away. Should look nice zipping by at 100mph @ 5 foot off the ground

Power:
Turnigy 3542 1450 KV
Turnigy Trust 55 ESC
3 Corona Digital MG 12.5g servos
1 HXT900 servo(rudder)
3s 2200/ 4s2200
9x7.5 apc/ 8x8 apc
GreatPlanes 2 1/2" Nylon spinner


Matt
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Old Feb 23, 2012, 11:01 AM
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Joined Jul 2008
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Hey Matt!

What a job!!!
How much time did you spent in it? The Dog looks cool
Long may he live!

Here is a video from the maiden flights of my buddy and me.
At the end there was no control signal. So the "Tigerduck" crashed.
But we cannot figure out why it happened.

Multiplex Dogfighter Maiden (4 min 46 sec)
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Old Feb 23, 2012, 12:01 PM
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United States, CT
Joined Aug 2005
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Quote:
Originally Posted by Manu Simon View Post
MRGTX

I'm running a turnigy 3025 1500 kv heli motor in mine which is pretty close to yours: With a 7x7 I metered 1010 watt static on 4S and 1686 watt on 5S.

if you want to stay in the 800w range, those prop you listed are too much. You should look for a 7x6 to stay around 800 w.
Thanks, Manu! Great information.
I will start with a 7x6 as you suggested... I may have to drop a few bucks on that Castle ESC sooner than I had planned.

Matt,
That is one spectacular paint scheme. Well done, sir.
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Old Feb 23, 2012, 12:01 PM
Fly it like U stole it
Pickle72's Avatar
Champaign, Il
Joined Mar 2008
2,428 Posts
Ouch! Whats the damage like?

I didn't spend too much time on it. 2 or 3 hours over the standard build I guess spread out over a couple weeks. I had to wait on the power system to ship from China so I had some time to kill.
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