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Old Jul 08, 2009, 02:28 PM
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Hi mate. It's the stock RTF from BH. I now have a spare speed controller so that one will be going in my 3D Lil Banshee

The ESCs are 30A, motors are 4300kv brushless in-runners with heat sinks.

The battery is an 11.1V, 3S, 2800mAh li-po.

The transmitter is actually a 6-channel transmitter and not 5 which is another +point and the receiver has 8 ports on it so I imagine its not a 5-channel , happy days. I will be selling this at some point.

BH states the flying weight is 907.19g (34 oz) but haven't weighed mine. Rather then fit gyros from the off, I decided that getting it flying as standard first was the best way to start and then tweak if needs be. To be honest now I have the DX6i, and knowing that the pitching rate of the plane will be much slower than the roll rate due to its long narrow profile, i dialed the ailerons back to around 80%.

One mod I do plan pretty immediately is mounting a servo in between the vertical stabs and cutting them for rudders. I can then just link up to the nose wheel channel for control. Again, the removable panel I have made under the plane will help me to do this ad there is a nice moulded panel line in top to use as reference for cutting the hole for the servo.

Two things that really let this model down are the fragile foam. It's not as fragile as standard packing foam but nowhere near the strength of the parkzone Z-foam. The second problem is the servos are pretty poor, i don't think they will last too long.

One more point is that it would have been nice to have a servo reducer inplace on the retract channel to save the servos.

I guess, at the end of the day - to have an SR71 Blackbird of that size, with as much scale detail as it has, fly as well as it does AND for the money, you can't have everything and it's all the little extras that add up.

Oh, while I remember, I took the opportunity to tack the fan shrouds on with a little CA (4 dots) while the covers where off. I think the fans are 6 blade 64mm units. It definately flies way faster than 35mph!
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Old Jul 09, 2009, 08:00 AM
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Thanks for the description. The propulsion system seems pretty reasonable. Assuming current draw of 25A per motor and battery voltage of 11.5V under load gives 287W per motor X 2 motors=575W. 575W/34oz X 16 oz/LB = 283W/LB or 575W/.908kg=633W/kg if you prefer. Seems quite respectable, it should move out nicely. The climb rate should be good in theory, how do you find it in practice? The published weight is probably correct, mine weighs 34 oz with smaller ESC/Batt./motor but a few extra bits of gear.

It would be interesting to hear what sort of flight time you get next time out with a fresh battery. Figuring ideal values WOT duration would be 2.8AH/50A=.056Hx60 min/H=3.4 minutes. That's par to good for most EDF's I've seen.

I like using outrunner magnets as hatch closers as well, but have just been taping the bottom cover in place while still in the fooling around phase.

On the subject of the servos, if you have the gray plastic linkage clevises, they were found to be brittle by others. I confirmed it by pushing the pin sideways with my thumb, the pin sheared right off. Consider nylon or metal replacements.

I'm using the DX6i as well. LOVE the unique Rx ID feature, but the elevon mixing instructions are wrong as you noted. There's an entire thread devoted to the subject, the title is something like DX6i elevon weirdness. At any rate you worked it all out, good shot.

Like to hear any updates on duration, flight characteristics etc. Sounds like it was worth the wait for this one.
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Old Jul 09, 2009, 03:06 PM
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I havent had time to get to the field yet to fly it again Hehe.

Yeah, I sat on the grass for about an hour and a half. You have to pretty much ignore the built in function and use the MIX 1 & 2 options!

I found that it needed a hell of a long run up on the grass to get break with the rolling friction of it. It's probably a mixture of the grass and weak battery.

I will confirm flight characteristics on the next flight. I have found a module here in the UK which can mount pretty much in anything and then afterwards plugs into the USB of my laptop and will give me data like Speed, altitude etc. So will hopefully be able to use that soon.
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Old Jul 09, 2009, 03:56 PM
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Awesome on the telemetry.

This bird I cobbled together was so underpowered it wouldn't ROG from grass with infinite distance. It did establish the absolute minimum power to fly though, which is about 300W, but I don't suggest replicating my experiment. Luckily its a whiz for hand launch.

I'm just finishing up the retrofit to 4300KV, hope to fly in hour or so. Its looking quite knackered but bugger appearances. Did I get the colloquialisms right? It seems to be a fleet requirement for my planes to be hideous ugly.

I hope whatever is keeping you from the field goes away. Later dude.
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Old Jul 10, 2009, 08:27 AM
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Hey D, I roger on the landing gear, clunk clunk. Wonder if there's a way to slow servos down at least on the DX6i? I bent smaller diameter wire with Z bends all around to link my gear for damping, back when I had gear. I pulled the 3600 Kv motors and put in 4300 Kv's with 6 bladed fans. It now flies satisfactorily and could stand to have the landing gear re-installed, but there's no point since our grass seems to be a foot tall all summer. I'll put em back in the winter.

BTW Whats the trick on the decals, are they peel offs or water slide?

I was surprised at how easily this jet will get back on the ground, it is the easiest of my jets to land in the little space we have. Easy hand launches too. I LIIIKE IT!
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Old Jul 14, 2009, 08:32 AM
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This flew pretty well after retrofit with 4300Kv 6 blade fanmotors, 40A ESC's and still 3S 2200 30C battery.

Too impatient to recharge 30C battery for second flight today, used 3S 2200 20C, figuring it wouldn't be full throttle most of the flight. Turns out it didn't work in theory or practice, flew too long, got too slow, ESC LV cutoff, nose pointed straight up then straight down from maybe 20 meters. Battery puffed, broken nose. Won't be repeating that blunder.

Fly, crash, rebuild. What a hobby. Going to get some bigger 30C batteries, weight does not seem to be an issue so far.
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Old Jul 21, 2009, 04:16 PM
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All back in one piece, got two good flights at last club funfly, no crashes. Taking the gyros out, they're probably not necessary.
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Old Jul 25, 2009, 11:23 AM
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Crashed and burned.

Just reporting in.

This time its the second flight. Here's what happened.

Have a look at the photos.

A couple of photos prior to flights 1 and 2...











Approx. 9 inches of fuselage broken away from both fore and aft sections. Luckily, the first 3 inches of fuselage took the shock and deformed although there is some deformation on the main section.





First few inches took most of the shock. Notice how it is slightly uneven to one side. This was transfered through the mid section which broke off into the main section of fuselage (see second pic of repair)...
....Once I have glued this back on as with the other parts, I will gently use a hair drier to soften and manipulate as much of the distortion out of the foam.






Main section mostly intouched. Note - Most uneven shock was transfered through broken off mid section to point on this picture at bottom left, again see second repair picture.




5 minute epoxy is a god send. Mid section back on. The benefit of these foam models is they tend to break away with extremely positive male/female fracture lines so a good bond is possible. Note the lines of shock running equidistantly from the fracture line on the left. this was due to a slightly un even impact with the ground.





Second repair picture. Picture from the underneath. Most of the shock not absorbed passed through to the left hand side just next to the battery cage. Note the use of pins. This just helps keep the repair in place while the 5 minute resin sets. I find it's not so much protection against leaving it to dry over night per-say, rather to avoid movement due to clumsy knocks within the first 5 minutes.




Once I have glued all parts back on, as I said before, I will use the hair drier to get as much of the distortion out as possible. I will do this after mating the fractured surfaces back together to ensure I don't accidently distort the gluing surfaces in the process. One this is done, I will break out the craft knife, and cut around the areas where there is gaps in the foam and left over distortion, making cuts of 90 degrees. With the aid of some packing polystyrene cut into suitable sized blocks, I can then bond these in and shave them down to size much like the last picture which features the same procedure on my Corsair's Vertical Stabilizer and rudder. With the Corsair, after I glued and shaved the block, I then gently carved the profile and panel lines and cut out the weak points for the rudder hinge. The process will be a lot simpler with the SR71 being that it's all fuselage and no control surfaces




As it's sitting here right now, it will fly but I will wait until it's sorted. It needs a new servo for the landing gear retract as it's been stripped. Last thing will be glueing back in the battrey cage, The battery has taken a little of the impact to one corner but has not expanded or ballooned so we'll watch it closely on the next charge and flight.

After a lot of thought my diagnosis is the following with regards to reason for the crash:

Aileron Rates - Since the Maiden flight, which went exceedingly well on both circuit and landing, I sat there for some time at home and dialled up the aileron rates. What I should have done at least was set them to dual rates LOW/HIGH so on low they had lets say a 4 degrees deflection rather than 30!!! This would have given me time to circuit and figure out a benchmark and what percent I felt safe to increase it by before switching up to a high rate allowing for a landing if I felt the high rate was way over board. Ultimately Setting up the ailerons to work exponentially will be the way forward as well but this is new ground to me which I have been lazy in.

Angle to the Wind - 90 degrees to the wind when our crashes happened. I can only think that this, however not the main factor in the crash but a considerable one considering the narrow profile coupled with the ridiculous roll rate didn't help.

Thumb-stick, screw on grips Loose - This sodding problem was the main problem and the straw. I new it was ridiculously sensitive on the first circuit but as you saw, the first time I saved it was when it undid, the second time, that was it. This was the deciding factor in the crash coupled with the ridiculous roll rate. The slip on the loose thumb-stick grip coupled with the ridiculous roll rate resulted in flipping straight over and playing radio controlled lawn darts.

I am pretty sure, once it's fixed and trimmed in properly with nice rates it will be a dream to fly. I can't forget how fantastic it looked in the air before the accident!

I'm now going to take the pins out and pop the broken nose piece on!
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Old Jul 25, 2009, 09:59 PM
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Thanks for the pics. Wow, looks pretty much identical to one of my crash/rebuild cycles. After the the epoxy and hairdryer treatment I use a paper mache product to fill in gaps and refinish the body work. Its called FastMache by Activa Products, its shredded paper fiber mixed with powdered glue (of course). Mix in water to a pasty consistency, spread with an epoxy mixing stick, dries overnight, sand. It really sticks to the foam and is stronger but not much heavier. Easy to paint as well. You can achieve any degree of perfection with more coats, depends on how much time you want to invest. Works well to fill in large gaps or depressions.

I've removed the gyros and agree that it reacts slowly on elevator and fast on aileron. I agree that a generous expo setting is helpful for lateral control. I've had about 8 good flights in a row now.

Mine looks like the bad place, so it fits right in with the rest of the squadron. I've given mine a landinggearectomy. Evesham Township has found that neglecting the mowing pays just as well as neglecting the potholes.

The big lesson learned so far - Do not allow it to run out of battery, any such behavior will be severely punished. Land early and often, it needs a good flying speed.

It is rewarding when everything is finally in harmony, though. Thing of beauty.

I wager your next flight will be better.
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Old Jul 26, 2009, 02:58 PM
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Quote:
Originally Posted by dLdV
Thanks for the pics. Wow, looks pretty much identical to one of my crash/rebuild cycles. After the the epoxy and hairdryer treatment I use a paper mache product to fill in gaps and refinish the body work. Its called FastMache by Activa Products, its shredded paper fiber mixed with powdered glue (of course). If you can't find it and want to try it, I'll send you some if you want. Mix in water to a pasty consistency, spread with an epoxy mixing stick, dries overnight, sand. It really sticks to the foam and is stronger but not much heavier. Easy to paint as well. You can achieve any degree of perfection with more coats, depends on how much time you want to invest. Works well to fill in large gaps or depressions.

I've removed the gyros and agree that it reacts slowly on elevator and fast on aileron. I agree that a generous expo setting is helpful for lateral control. I've had about 8 good flights in a row now.

Mine looks like the bad place, so it fits right in with the rest of the squadron. I've given mine a landinggearectomy. Evesham Township has found that neglecting the mowing pays just as well as neglecting the potholes.

The big lesson learned so far - Do not allow it to run out of battery, any such behavior will be severely punished. Land early and often, it needs a good flying speed.

It is rewarding when everything is finally in harmony, though. Thing of beauty.

I wager your next flight will be better.
Thanks for the useful comments and advice on the paper mache stuff. I have now setup dual rates as well as dialed in expo and downed the rates hugely on one. What sort of angle of aileron and elevator deflection are you seeing on yours?

I got lucky over here the other day as well, I went to my local model shop to grab a new ariel for my TX and some how managed to walk out with the monster banana hobby 70mm edf F16 Fighting Falcon with everything bar the TX/RX. The price... 100!!!!

The chances of that are 0 over here! I even now have the 14.8V, 4 cell in it too! I'm waiting for my new charger to arrive before I can fly that.

Oh, lovely pictures by the way! You need to make or buy some intake spikes! I'm sure you could mould some pretty easily.
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Old Jul 26, 2009, 08:45 PM
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SR-71 Battered and Bruised But Still Flying

Good score on the F-16. I paid $40 more for the Kyosho 55mm Falcon, 60cm/24in. span, receiver ready . The plane flies nicely though, very stable, smooth and predictable. Foolishly low passes, not a real barn burner but not slow either. The tailerons barely move on that one. Not bad for such a small plane. First EDF for me, though I had some pusher jet experience. Blackbird is EDF #2.

Took some measurements of control surface deflections. Thanks for the suggestion, I need a starting reference too, still tinkering with setup. The measurements are distance rather than angle due to too lazy to devise an appropriate method of measuring. Could measure elevon width and Pythagoros it, but too lazy for that too. Sticking to single rate due to don't know any better.

The static reference point is the top surface of the rearmost and outermost part of the wing. The dynamic reference is the center of the rearmost point of the elevons.

+5mm up with controls neutral, both surfaces

+15mm up / 0mm down full right stick or full left stick. Most of the movement is when the stick is well over to the side, I'm using positive expo, which should dampen the response near neutral stick if I'm understanding the ing DX6i manual.

+27mm full up stick

-20mm full down stick

I still find it twitchy on roll axis in crosswind, considering dialing in more expo. It seems to need a lot of up in turns at times, I think its because our field is only W=150 meters X L<=300 meters, dimensions courtesy of Google Maps. Subtract from the width parking, the flight line, and keeping the plane a few meters in front of you - the plane has to turn about in 120 meters or so. It likes to drop the nose a good deal in certain conditions. Its not hard to deal with, it just wants a buttload of up.

The inlet cones are in storage til winter. The grass keeps snatching em out. The grass was mowed 2 days before this pic, before that it had been a month. So til autumn, its very little with wheels, nothing with odd protrusions.

Hope to hear more flight reports. Its interesting to compare notes, e.g. after much tinkering and figgering, this settled out to pretty much the same power system as your stock version.

Finally, (sigh of relief from the audience) after reading way too many posts about this airplane, roll axis seems to be a factor in a lot of crashes.

"Never Mind The "
S. Vicious
Influential English Philosopher, circa 1980
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Old Jul 27, 2009, 02:15 AM
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Quote:
Originally Posted by dLdV
Good score on the F-16. I paid $40 more for the Kyosho 55mm Falcon, receiver ready . The plane flies nicely though, very stable, smooth and predictable. Foolishly low passes, not a real barn burner but not slow either. The tailerons barely move on that one. Not bad for such a small plane. First EDF for me, though I had some pusher jet experience. Blackbird is EDF #2.

Took some measurements of control surface deflections. Thanks for the suggestion, I need a starting reference too, still tinkering with setup. The measurements are distance rather than angle due to too lazy to devise an appropriate method of measuring. Could measure elevon width and Pythagoros it, but too lazy for that too. Sticking to single rate due to don't know any better.

The static reference point is the top surface of the rearmost and outermost part of the wing. The dynamic reference is the center of the rearmost point of the elevons.

+5mm up with controls neutral, both surfaces

+15mm up / 0mm down full right stick or full left stick. Most of the movement is when the stick is well over to the side, I'm using positive expo, which should dampen the response near neutral stick if I'm understanding the ing DX6i manual.

+27mm full up stick

-20mm full down stick

I still find it twitchy on roll axis in crosswind, considering dialing in more expo. It seems to need a lot of up in turns at times, I think its because our field is only W=150 meters X L<=300 meters, dimensions courtesy of Google Maps. Subtract from the width parking, the flight line, and keeping the plane a few meters in front of you - the plane has to turn about in 120 meters or so. It likes to drop the nose a good deal in certain conditions. Its not hard to deal with, it just wants a buttload of up.

The inlet cones are in storage til winter. The grass keeps snatching em out. The grass was mowed 2 days before this pic, before that it had been a month. So til autumn, its very little with wheels, nothing with odd protrusions.

Hope to hear more flight reports. Its interesting to compare notes, e.g. after much tinkering and figgering, this settled out to pretty much the same power system as your stock version.

Finally, (sigh of relief from the audience) after reading way too many posts about this airplane, roll axis seems to be a factor in a lot of crashes.

"Never Mind The "
S. Vicious
Influential English Philosopher, circa 1980
I think we both new the roll was going to be the major issue - But rectifiable. Thats why I chose to ditch the 72MHz transmitter and receiver and go straight to the DX6i.

Here's a thought... Why not mix in a little up elevator slaved to the ailerons? That'll help out with the dipping you are experiencing in turns. I have also considered plopping a rudder servo in the middle and that mixed in with the ailerons could help. I too noticed this dip on the few circuits I have managed with the plane. I guess because the main lift is generated to the rear, in the turn the centrifugal force is sucking up some of the energy and pulling the plane down.

I still can't get over how awesome it looks in the air though. I like the pic of the hand launch - Do you need much oompf behind it or does it do pretty well?

I'll be dialing those control surface specs in, thanks for those. I have read that the F16 also has a large gap between high and low rates so this is all a good lesson learned I feel.
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Old Jul 27, 2009, 07:48 PM
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Blackbird Debug/Handlaunch

Yeah, getting the roll settled out is key. Probably would not have gotten this plane had I not finally put my '92 Futaba Conquest into semi-retirement this year and gotten a computer radio. As you say, lateral instability was anticipated.

Planning to try your idea of coupling roll to up/down. The mix method I used on the DX6i (found here post#35 http://www.rcgroups.com/forums/showt...=940867&page=3) for elevon used the dual aileron tail mode and I used only Mix 1, I think it mixes ailerons to flaps or something. Might take some tinkering and I may have to abandon that method and try your Mix 1 + Mix 2 method. Taking a day off this week, so should be able to try it out this weekend.

Regarding hand launch, I'd say throw with authority but not all your might by any means. Its a surprisingly easy launch. I grasp it at the front of the wheel well, (the equipment hatch was never installed, thumb goes there), throttle up til it pushes the nose below horizontal, maybe an extra click or two, and give it a slightly harder than normal chuck, 10 or so degrees up. Then max throttle and off it goes. It hasn't done anything weird on me yet. One launch I couldn't find the right stick, usually a fatal error with most of mine. This one was still patiently flying along, starting to roll to one side but taking its time about it. Plenty of time to gain control of the radio. Caution: The front of the wheel well broke on its first launch, mended with duct tape for that day, later reinforced with balsa on the front and inside.

The instructions that came with the plane are somewhere in outer darkness. How do those throws compare with the current settings? Man, hope you don't crash, I'll have to exile myself from RCG.

Got a second hand report about a local pilot who SURPRISE!! crashed one on maiden. Once again, salvageable aftermash. Wouldn't ROGrass, throttling down, plane leapt skyward, flew for a while, something weird happened, kersplunk.

Sticking with single rate for now, one change at a time and all. At any rate, will post results of up/down/turn coupling flights. Best of luck.
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Old Jul 29, 2009, 07:44 AM
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SR-71 Pitch and Roll Debugged?

Too stupid to couple up to turn in Dual Aileron mode on DX6i. Tried but couldn't quite find the trick of it. Anyway, found a work-around.

I've had two consecutive flights with nice smooth control on roll and perfect level turns, very little back stick required. This should apply to your mix method as well. I was surprised to discover that even though mine mixed elevator to flaps, the D/R EXPO setting for AILE controls roll and ELEV controls pitch. WTH?

1) Reset the elevator rods so the 5mm up for reflex at neutral setting is achieved with trims centered. Full elevator travel should be roughly the same as previously posted.

2) Go to D/R & EXPO. Select SW position 0 for AILE, set movement to 50%, EXPO to +80. Select ELEV, SW position 0, set movement 90%, leave EXPO on INH. (Using DX6i with this mix method post#35 - http://www.rcgroups.com/forums/showt...=940867&page=3)

At this point you should have lots of elevator travel, much less aileron. This single rate setting was sufficient for all speeds.

Odd thing is I haven't been able to test in wind, which its been windier than normal here all year. When you want wind you get calm, & vicy versy. Would you prefer a poke in the eye or a kick in the pants, Sir?

Blue Skies, Brothers.
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Old Jul 31, 2009, 09:49 AM
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I think the simplest solution us going the be popping a servo in the middle at the back and modifying the vertical stabs to include rudder control surfaces. Should gave a little time free this weekend so maybe will reach a point with the repairs where I can do this.
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