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Old Oct 23, 2008, 11:15 AM
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Temperature limits found....

Well, I think I finially found the temperature limits of hot glue last night. I was having a really nice flight with the F-22. It was around 43 degrees outside and the winds were really kicking up (I love the high speed down wind runs!)

Just performing the usual stuff, rolls, loops, etc, when I was making an upwind run and just started another roll when "kerpow!" was the sound that came from the F-22 in mid roll!

I killed the throttle, it completed the roll and went into a slow spiral as it decended. My first thought was, "okay, the prop came off the prop saver". I was able to level it out, but she was still banking slightly and it landed.

When I walked over to the F-22, I found that the motor was gone! I picked up the plane and found it hanging by the wires, prop still attached! What appears to have happend is the hot glue completely let go of the ply firewall. It was clean, as if it hand never been attached. Only two spots of foam could be seen on it, were I had used CA to "spot tack" it in place then applied the hot glue. The cold air and hot glue here just didn't mix. I think the added torque of the roll opposite motor rotation was the extra it needed to break free.

Only real damage was where the prop impaled one of the duct runners. When I was done flying, I found I was able to CA the ply mount back into place using the "flat hot glue base" for alignment. That, and a little foam repair/paint and the battle damage was repaired. On my next build of this plane I think I will use longer bolts and a couple of jam nuts for embedment into the hot glue buildup.
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Old Oct 23, 2008, 11:22 AM
Pusher jets rule!
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Mesa, AZ
Joined Jan 2006
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I have a small foamy delta that has a 12mm Feigao motor mounted in pusher config just like this. What I did was epoxy the ply to the foam, then used Shoe Goo to secure the motor (and I put a heat sink on the motor as well). Over 2 years and still going strong. Try it, you'll like it!

Pat
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Old Oct 24, 2008, 11:01 AM
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Thanks for the info Pat!

Last night I though the better of just leaving it at CA and instead added 5 minute epoxy to "encase" the ply mount and the hot glue/foam area, so now she should be back in action, weather permitting.
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Old Oct 24, 2008, 01:52 PM
Pusher jets rule!
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Mesa, AZ
Joined Jan 2006
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The thing about CA and 5-minute epoxy is that they become brittle and can shatter under long term vibration loads. Shoe Goo remains somewhat flexible and will hold much longer.

Pat
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Old Oct 25, 2008, 05:48 PM
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Pat,

Thats a really good point about the Shoe Goo, thank you!

Thrust line question:

After I re-secured the motor mount back in place, I realized that I had placed it slightly below where it had previously been. Right now, the "hub" of the prop is basically below the wing, where as before, I thought it was directly in line with it. So my question is, what is the possible impact of the thrust line with the airflow set up this way?
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Old Oct 25, 2008, 10:18 PM
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i dont think it will be noticeable, i have had them both ways and had no problems.
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Old Oct 26, 2008, 12:02 PM
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Thanks, that is what I was hoping. Took it up for a test flight yesterday after the repairs to see how it would handle. To be fair, it was hard to give it a good test, because the winds were around 22 mph, gusting to 30!

The F-22 kept trying to "pitch up" both in and out of the wind, so I'm wondering if the thrust line is impacting this aspect of flight, or if it was just the wind. The small amount of epoxy I added may also be playing a part in affecting the CG, but it was a really small amount which was applied.

Then again, I tried to build this one as light as possible, and for speed, so perhaps its enough to cause this......
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Old Oct 26, 2008, 02:35 PM
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i know the ones that i built that had the motor right in line with the wing had a dendancy to put the nose down under power.. i would try to adjust the CG

How far below the wing is the center of your motor?
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Old Oct 27, 2008, 09:20 PM
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I checked tonight and it is very slight. The center of the hub is about 2 to 3 mm below the bottom surface of the wing.
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Old Oct 27, 2008, 09:51 PM
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yeah, check the angle make sure the motor isnt angled up, other than that, you must have a cg issue or something.. that is to slight to make a differance
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Old Nov 17, 2008, 09:49 PM
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i finished building mine, will maiden this evening. guys, i didn't use the plan here, but tomhe's instead and shrink to 50%, manage to get a 5" prop in, have to cut outward to fit it. i was wondering anyone using Emax 2805 with 2840KV? coz i bought this motor as many of them using, but then last nite i was trying with 5x5 on 3S, it seems not enough thrust. if can't fly, then i m gonna switch another motor KA450H (3200KV) with 6x4 or 4.75x4.75. thanks
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Old Nov 21, 2008, 06:08 AM
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Naples
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Strange phenmena: I am having lots of fun with that little jet, but cannot explain why that thing wants to turn to the right at high AOA / slow speed / power on. Contributing factor migh be the elevator tabs extending forward from the hinge line. I have tailerons and ailerons.
Hans
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Old Nov 21, 2008, 06:28 AM
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Mine have all done this as well, when attempting to hover, with a high AOA like you say, right before a stall, it always seemed to tip right, i was always correcting for right, i think it has to do with the torq of the motor... But did make for some cool hovering right circles
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Old Nov 21, 2008, 06:20 PM
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ha, mine is the same. i finally found a good combo. 3200kv with 4.75x4.75, its fast! previously i tried 5x5, but a lipo started to puff a little right after i landed, so i lowered to 4.75x4.75, its even faster.

like u guys, it tend to tilt to the right, so i have to give alot of left subtrim, but still sometimes want to go right and left, i guess its the wind or something. it still glide super well just like the 100% one. i like it. oh, mine, i have cut a rather big area to contain that 5x5 previously, its vertical stab is also being cut off by about 10mm. haha...
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Old Nov 23, 2008, 01:40 PM
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Naples
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No, it can't be torque: unless you use a pusher prop torque makes the plane roll left..
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