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Old Apr 10, 2011, 01:51 AM
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Thanks Paul...I've been racking my brain about it and I just can't figure it out. I had 8 total flights and each hand toss was quite the adventure. I've second guessed my hand tossing ability, the epoxy I added (varying weight?) after initial damage, the bowling ball-sized holes I used to toss her (two fingers...Is that enough?)...Ultimately I can't figure out the true cause of that drastic right bank at the release point.

For the next airframe (Is it really my 5th?!!?) I am going to purchase this:

http://shop.rc-electric-jets.com/Jet...Jetapult-1.htm

The Jetapult just might be my answer. The angle of trajectory is parallel to the ground where I would prefer a 10 degree or 15 degree AOA but it does look effective. I'm done with the hand tosses for the Blackbird. The long fuse and short aft delta wings just isn't a good combo for that technique.

Rest assured my new airframe will be arriving in a few weeks. Hell, I even have that great afterburner/LED system that awaits. MUST REBUILD!
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Old Apr 10, 2011, 02:05 AM
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I am looking forward to your rebuild, as well as your take on the Jetapult. I should quit being cheap and buy one of those myself! Please let us know how it works out. I don't feel I could hand launch one successfully so I usually have a buddy throw it for me and like I say, it is always pretty scary.. I wish you could see the video. My buddy throws my HL F-86 and luckily we have a retention pond we are throwing over because it gives me an extra 5 feet or so of ground clearance, but it always seems to be close.

Paul
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Old Apr 10, 2011, 03:50 AM
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Certain EDFs are a breeze to hand toss. The Phase 3 F-16 comes to mind. Nice semi-circular fuse to wrap your hand around...The Ubiquitous 70MM F/A-18 Hornet is another easy hand toss as it has a bulky undercarriage that is easy to grip. The SR-71 is a whole other monster altogether. No bottom surface to grip (flat) and the bowling ball holes I employed may not be the answer after all.

Outside of using retracts with a smooth, flat, long runway (which is everything my flying field is not), I just don't know what the best option is for this great black nemesis/muse of mine.
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Old Apr 11, 2011, 02:59 AM
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A catapult may well be your best option, not least because you'll have your right hand on the stick right from the start. You've talked about poor handling when slow and nose-up and I think that's what you're seeing here, plus a fair bit engine torque. If its any consolation, every time I toss my jets* it's a bit of a gamble too. High wing loadings and zero prop wash make for ineffective controls during the opening seconds of the flight. Chances are that your SR71 leaves your right hand at about 10mph max, yet you'll have to wait until she's doing 25-30 before you have real control. Up to that point Mr Newton is in the driving seat. For that reason, a Cat that'll put your jet 6 feet up and doing 25-30 mph in a nice linear fashion should help a lot. You just need a good anchor point for the hook which doesn't cause a nasty pitch-up at launch or damage on landing.

Si

*70mm F18 (Lander fan and 4s 3300 batts) and my tiny F16 (looks like a P3 EF16 but has smaller, scale wings) with a HET 6904/2w-20 and 4s 2200 batts. The F16 has particularly high wing loading and lands "hot". Launching that is all about hoping not to hit the ground before you have gained elevator authority. Luckily she accellerates real fast.
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Old Apr 11, 2011, 02:23 PM
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John,

a launch skeg on the bottom of the fuse would give you something to hold on to. Also, the thrust tubes we discussed would aid in a hand launch.
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Old Apr 21, 2011, 08:39 AM
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And here's a little teaser photo of the prototype kit for the SR-71. There are some issues unique to the SR-71 so a little reworking is required. I refuse to put out a kit that is anything less than prefectly over the top.
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Old Apr 21, 2011, 11:03 AM
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That looks SICK! I can't wait to install those bad boys in my new airframe (which I got yesterday)! Should I wait before I glue the airframe together?
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Old Apr 21, 2011, 11:41 AM
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Aros, i think i might have a idea why she's turning right on launch, I built a GP Evader with 1200 watts and had the same thing happen, as soon as it left the bungee she dove to the right and hit the ground,thinking about it afterword i never checked the lateral balance,which is very important. Simply have a partner help you balance the plane on it's vertical axis by putting the point of your finger on the tip of the nose and have them put a finger on the trailing edge of the wing between the nacelles,if it rolls to the right(which i suspect) counter weight the left wing tip until the model sits level. Got the idea? hope this helps as i keep looking at one of these at work and have a set of custom 60mm edfs that would make it scoot
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Old Apr 21, 2011, 12:00 PM
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Quote:
Originally Posted by Aros View Post
That looks SICK! I can't wait to install those bad boys in my new airframe (which I got yesterday)! Should I wait before I glue the airframe together?
you can glue the airframe (not the bottom cover) , but do not install the fans and motors yet.
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Old Apr 21, 2011, 12:02 PM
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Holy cow Mustang, I think that is IT! I didn't even consider lateral stability! Due to some hard landings I ended up using epoxy on varying points on the underbelly and I will bet you anything the starboard nacelle bottom had more epoxy weight than the port side did. That would perfectly explain it! Thank you for pointing that out. I will make sure this new airframe doesn't have that issue.
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Old Apr 21, 2011, 12:04 PM
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you can glue the airframe (not the bottom cover) , but do not install the fans and motors yet.
Will do...Man I can't wait!
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Old Apr 21, 2011, 12:05 PM
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Your welcome,glad to help,looking forward to trying one of these myself one day
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Old Apr 21, 2011, 02:16 PM
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Will do...Man I can't wait!
The camera doesn't do these things justice. They are so bright that they have a tendency to mess with the camera's light meter. I wish I could get a decent pic. may have to wait until the plane is in the air and far enough away from the camera.
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Old Apr 21, 2011, 03:29 PM
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The camera doesn't do these things justice. They are so bright that they have a tendency to mess with the camera's light meter. I wish I could get a decent pic. may have to wait until the plane is in the air and far enough away from the camera.
Joe know anyone who has a camera with a SPOT meter? that will solve your problem
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Old Apr 23, 2011, 05:04 PM
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Okay, SR-71 #5 is ready for maiden. (Joe, I have the motors and covers easily removable for when your afterburner kit arrives)...I like to take photos before my maidens so I can always have proof that I once owned these planes, lol...

You can see how I have modified the battery compartment and mid section to fit the 4S 4000 mAh 45C battery. Still trying to find the CG sweet spot. Lateral stability is great, everything appears ready to go. A bit windy today so I may delay the recon mission. I'm also going to have a friend help me dial in the motors and ESCs so we are getting peak performance from both. He theorized we were only getting about 80 percent out of the motors the last go around. Holy cow if that is right, this thing may see 120mph!!!
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