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Old Dec 26, 2011, 07:24 PM
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San Diego
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Ok just to make Phil happy I changed the servo on the elevator

The 645 was pretty old and had to much slop in it for my liking, I am eventually planning on moving this entire setup over to my falcon 120 so I went ahead and invested in a 7985mg so that's 172 oz an inch in torque and digital, way overkill but it was only a bit more expensive so thought might as well do it right since it will go in that huge falcon someday.

One thing that is an issue with this model is thrust tube, fan and elevator linkage alignment. The fan sits so high that the thrust tube will have lots of down thrust but it allows room for the internal flap linkage to clear the fan and the thrust tube will clear the elevator linkage. So moving the fan down helps align the thrust tube but then you are getting close to the flap linkage clearing the fan and then the elevator linkage rubs on the thrust tube. You will find its a big balancing act. I found that a 1/4" lowering of the fan was a good balance but it did creat a rubbing of the elevator horn on the thrust tube so I used a small shaped piece of wood to create some clearence for the elevator and all is good. I do think I have a slight amount of down thrust but it seems pretty minimal.
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Old Dec 26, 2011, 07:58 PM
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Oshkosh, WI
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Hi, bri66! Can see my smile?

That a good choice of servo. I think I'll try pick one up too at the coming swap where there will be vendors selling at a very good price.

Have a great maiden.

Phil
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Old Jan 11, 2012, 10:09 AM
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Well guys unfortunately I have decided to sell my hawk... I lost my favorite P-47 this past weekend from a linkage failure and the manufacture has agreed to replace it for half off but I'm tapped on planes right now and this one is on the bottom of the list.... If anyone local southern CA is interested I am selling it airframe with linkages and ducting for $200. Bummed to not see it fly but I was also pretty concerned about the 14.5 lbs and think my power system is just to heavy for this airframe and can't afford to loose my power system or lipos since they are going in my new falcon.
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Old Jan 11, 2012, 11:52 AM
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Sorry to hear your loss, Bri77. Sometimes mishaps occur when one flies one's models; unless they're kept as hangar queens. Too bad you chose to sell your Hawk. Was looking to hear about its maiden.

My Hawk has gone back one space in my build queue as I try to complete a prior project. Have not had a chance to weigh mine; just hope my hybrid JHH/Haoye 4.5incher fan does not add that much weight. Hear high wing loading is not kind to this model.

Phil
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Old Jan 11, 2012, 07:04 PM
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United States, GA, Alpharetta
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Quote:
Originally Posted by PhilLin View Post
Hi, bri66! Can see my smile?

That a good choice of servo. I think I'll try pick one up too at the coming swap where there will be vendors selling at a very good price.

Have a great maiden.

Phil
FYI, I maidened my AMD Hawk a few weeks ago with a total loss. I had one HS485 servo (I think about 90 in/oz) on the elevator. after take off I made a reduced throttle turn downwind to trim it and on the turn back up wind with increased throttle it didnt want to tighten the turn with increasing elevator. After a wide turn I got it back to the pattern and made another downwind, made the turn to upwind OK, and in a descending shallow dive crossed down the runway (upwind), pulled slight elevator and nothing happened pulled more and nothing happened. when it hit the ground at the end of the runway I was holding full up elevator and it never raised the nose. I think the HS485 was not strong enough for the full flying stab. I have flown other Dynamax powered jets with equivalent servos but they didn't have full flying stabilators. You need strong servos if you have a jet with flying stabs.
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Old Jan 12, 2012, 11:55 AM
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Sorry to hear of your loss, rfodor! & Thanks for sharing your experience. This is the second concrete example of an AMD Hawk stab servo.

I've learned my lesson from my F-4. Now I do a bench test to make sure the whole flying stab assembly can withstand the torque above 160 oz-inz (or 70 oz-ins per side, higher than the servo rating); just to make sure the torque tube is also adequately anchored in the stab panels. Better hav them give on the ground than in the air. You should see how much distortion the panels have at these tests

Phil
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Last edited by PhilLin; Jan 13, 2012 at 10:13 PM. Reason: change ground to bench, clarified torque req.
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Old Jan 12, 2012, 02:06 PM
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Yeah, didn't Marvin lose one due to stab servo failure? Bummer, it's a nice looking model for the money.
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Old Jan 13, 2012, 02:14 AM
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Yeah, didn't Marvin lose one due to stab servo failure? Bummer, it's a nice looking model for the money.
His was a stab failure not servo failure from what I read.
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Old Jan 13, 2012, 02:14 AM
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I think I might keep mine and go with a 100mm fan on 10s to keep the weight down
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Old Jan 13, 2012, 06:01 PM
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I think I might keep mine and go with a 100mm fan on 10s to keep the weight down
After my experience, I believe that it would fly nice at 12-13 lbs. 14.5 to 15.5 (like mine was) is too heavy. It had plenty of thrust and it definitely flew ok. Maybe if the elevator authority was solid it would have been OK. I won't be trying another.
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Old Jan 12, 2014, 06:53 PM
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United States, KY, Louisville
Joined Jul 2008
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Two year bump....

Since Bob hooked me up with one, I decided to re-read most of this thread. I missed a lot from the first time I read it.

I believe I have the Will Hobby version. Canopy isn't as bulbous, and the hatch to the fan is really long, and it doesn't have a foam core wing.
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Old Jan 12, 2014, 07:26 PM
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ohio
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My advice, keep it as light as possible or it will be problematic during landing. Mine flew good but was heavy. My dynemax was a beast in this plane.

Kevin Cox flew his on a jetfan 90 on 10s, and it flew well. I would go that route if I was starting from scratch now...to save weight.
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Old Jan 12, 2014, 07:30 PM
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My advice, keep it as light as possible or it will be problematic during landing. Mine flew good but was heavy. My dynemax was a beast in this plane.

Kevin Cox flew his on a jetfan 90 on 10s, and it flew well. I would go that route if I was starting from scratch now...to save weight.
I'm flying the FlyFly Hawk at 9lbs with a Jetfan 90 on 8s. This is basically the same thing, but in fiberglass w/ built up wings. My FlyFly just isn't fast enough and I really liked the speed and vert that yours had. I'm just not sure a 90mm will do that. Thoughts?
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Old Jan 12, 2014, 07:59 PM
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To this point, this is still the only edf that I have had that had almost instant acceleration and powered straight up in the vertical ... and I have had a bunch in the last 5 years. In the video I am backing out of the power way before the top of those climb outs. It was definitely fun. But having said all of that, there is a lot to be said for a well behaved airframe as well and at the weight I was at it was not much fun to land unless there was a 10mph direct headwind. I also had to be very smooth on the elevator, no yanking or it would snap out.

I think Kevin Cox was right at 4000 watts, which is only just slightly less than I was running, obviously the dynamx flies the plane with more authority but the jetfan was no slouch. maybe jetfan on 12s?

Have you talked with Bob? I know he was surprised with the performance of the jetfan as well. Hopefully Kevin Cox will chime in...
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Old Jan 12, 2014, 10:36 PM
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Joined Jan 1997
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Kevin is correct on all accounts. Mine no longer snaps and it was playing with the CG and the elevator travel the fixed it. I flew mine first with the E-turbax and 2 motors later (2-3 years of flying) then I put in the JetFan 90 V2. I think it does well and it is only about 3000watts. I am using 5 year old...or older lipos, you gotta love those Rhino packs . A 12S set up would be awesome but I'm happy with 10S. BTW...the E-Turbax had good vertical but not like Kevin's!
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