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Old Feb 12, 2008, 01:57 AM
X-15 Jockey
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XF5U Flapjack profile Build

I've been on a 6mm profile parkjet binge lately, and decided to do one of my favorite wierd planes, already did a vertijet and a goblin, so I thought I'd give this a shot.

Span accross the full flying tailerons is 37", span is 27" and chord is 27", overall length is 33 inches, area is about 500 sq inches. Depron weight is 5 oz, so RTF AUW should be in the 15-17 oz range, depending on whether I need a 2100 or 1320 pack, for either power or CG reasons. Will have full flying taileron, and differential throttle.

Should be able to sand and glue the airframe tomorrow(this is a dry fit, since I just scaled up the 3-view and drew the plans by hand tonight and cut parts) and be ready for some glide tests before component install.

Enjoy.

Frank
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Old Feb 13, 2008, 01:33 AM
X-15 Jockey
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Finished the fuse tonight, and did some glide tests, started with 25% CG, worked back to 31% seemed to glide fine and not pitch up, will probably settle on something inbetween for first flight. Trimmed the motor shafts, and ran them up, 8200 RPM with an 8x3.8 prop @ 8 amps, shoud run fine with a 1320 pack for two in parallel, differential throttle is set up and working fine.

Paint added around 1.5 ounces, AUW so far is 8 ounces for the plane, and 8 for the electronics, will be a bit heavier than planned, around 19 with battery.

Thrust and wing loading should still be plenty.

Color looks a little more blue than in person, must be the flash.

Also, laid out the parts showing the carbon on the wing.

Frank
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Old Feb 13, 2008, 05:37 AM
X-15 Jockey
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Finished

Here it is ready to fly, AUW is 19 oz with 1320 pack, test showed hover power at a little over 1/2 throttle using a battery that started at 11.4 volts, tail authority in hover seemed pretty good.

Motors are 1100kv outrunners I got at the NW hobby expo, 8x3.8 apc props.

Frank
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Old Feb 13, 2008, 05:40 AM
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Very cool! Will be watching progress on this one. Has been a favorite for a long time. Just no time to build. Great work......... Keep it coming.
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Old Feb 13, 2008, 05:45 AM
X-15 Jockey
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Thanks, should be able to maiden on saturday with video if the weather is ok.

Frank


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Originally Posted by tinkrerpilot
Very cool! Will be watching progress on this one. Has been a favorite for a long time. Just no time to build. Great work......... Keep it coming.
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Old Feb 13, 2008, 03:07 PM
X-15 Jockey
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Maiden

Weather this morning was too good, so I convinced my wife to come video. Maiden went pretty well, tail throws were perfect, unfortunately I couldn't find an 8x3.8 reverse prop, so I had to run them both in the same direction, this leads to quite a bit of right trim, sometime I'll get a reverse prop and be able to take out the trim.

Handlaunch was simple at a little below half throttle. Loops were nice and big with some power on, rolls were surprisingly axial and fast, slow speed flight was good, landings needed a bit of power on to prevent the right trim from rolling me a bit during the glide, just a tad of power and chop in the flare.

I tried 29% of chord CG and that was too far back, In fact, the tail, scale, doesn't give enough lateral stability in a spin. In the video you can see how a differential throttle snap does quite a few gyrations before it comes out to the left, to the right, it went into an inrecoverable flat spin, and fortunately "Pancaked" without really doing anything. I moved the CG forward to 25% and no problems, although if you get really slow and try a full deflection control input, it will eventually stall out and only some altitude, and throttle will get you out. I notice this even in my XXL sukhoi.

Normal straight ahead, I couldn't get it to stall, and it was controllable throughout.

I would not suggest differential throttle, even on the lightest of mix, the motors are too far forward and apart and were just too responsive, I think that's what also contributed to my unrecoverable spin, I automatically gave left rudder and I think that snapped it into a flat spin the other direction.

Subsequent flights with 25% cg and no throttle mixing was a pleasure and flew great with no bad habits. It really has the right look in the air too. You can see a bit of flex in the body when flying on hard rolling manouvers or in hard throttle inputs. All of the flying was at 1/3 to 1/2 throttle, it climbs vertical on 50% throttle.

Here's the video posting:

http://www.rcgroups.com/forums/showp...97&postcount=1

Enjoy

Frank
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Old Feb 13, 2008, 06:22 PM
X-15 Jockey
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One other note, the motors worked great, I picked them up from rchotdeals.com vendor at the nw hobby expo, they run 8200 rpm with an 8x3.8 apc prop at 8 amps, and were $16 including an 18 amp speed control, unfortunately the speed control had a 2 amp bec, so I picked up 2 of the suppo 20 amp controllers for $16 each which have 3 amp bec's, they had the towerpro 9 gm servos for $7 each, and my son and I each got a free hat

They have the normal threaded shaft, but it is 3mm, and I was able to cut it short, use a collet mount with the spinners/props with no problems, they aren't really heavy either at 1.3 ounces.

so, for speed controls, $32, two motors, $32, servos, $14, and reciever(6100E), $39, and a sheet and a half of depron and some carbon, I'm only at around $130 for a twin, less if I would have trusted the 2 amp bec.

Frank
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Old Feb 14, 2008, 11:53 AM
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Outstanding Frank!

I have every XF5U-1 and V-173 thread I could find bookmarked, just added this one. I'll probably build a profile first, as you did - going to be a while before I'm confident enough to try Guiseppe's plans.
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Old Feb 14, 2008, 01:42 PM
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I love it. Looks like you've found a great and affordable combo, believe me I'm taking notes. Only thing yours is missing is 4-blade props. I was thinking about what it would take to be able to use the orange 4-blade GWS props on such a model, for the scale look.

I was also aiming to make one a little smaller, more indoor-like, but have been stymied so far in that I can't find a combo of motors and props and esc and battery that I like/ can afford and that will look more or less scale. I don't want to hang big gearboxes on those front pods, and at the scale I'm looking at, an outrunner may also look weird out there.

Any tips for something about 3/4 the scale of this one? I got a paper models International version of this plane I will probably base the plane on. The real one even had nose art: bugs bunny on a flying carpet!
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Old Feb 14, 2008, 02:02 PM
X-15 Jockey
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Hi, I looked at the multi-bladed props, and it looks like I had a choice between a 3 blade 9x7 or a 4 blade 10x8, which are way too large for my motor choices, unless I maybe wanted to go 2s, then I would need a special spinner, and they are bright orange(could be painted). I decided I'd rather have the look of a good spinner and forego the multi-bladed, but you need to do what makes you most happy I know I've had a couple of thundertigre kits that came with 3 and 4 blade(I think 9x7) props that came with spinners, but I don't think they had reversed pitch, and I think that is more important to run couter-rotating especially with the motors this far apart. Maybe Graupner makes something.

For small motors, I've used a grayson hobby C20 motor, they are around $20, and can run about8-9 amps, they make a 1550kv version, you could probably run this on 2S and a 4 blade prop, they weigh 1 ounce and are about 1" diameter which should be small enough. United hobbies also has a bunch of small outrunners that are pretty inexpensive, just need to watch the weight of them. United and Grayson and BP hobbies all have pretty inexpensive speed controls.
BP has an ele C20 runs 200 grams thrust on 8x4 on 2s, and they are $17.95.
You'd need to watch the weight of it though.

Frank


Quote:
Originally Posted by Aten W Arthog
I love it. Looks like you've found a great and affordable combo, believe me I'm taking notes. Only thing yours is missing is 4-blade props. I was thinking about what it would take to be able to use the orange 4-blade GWS props on such a model, for the scale look.

I was also aiming to make one a little smaller, more indoor-like, but have been stymied so far in that I can't find a combo of motors and props and esc and battery that I like/ can afford and that will look more or less scale. I don't want to hang big gearboxes on those front pods, and at the scale I'm looking at, an outrunner may also look weird out there.

Any tips for something about 3/4 the scale of this one? I got a paper models International version of this plane I will probably base the plane on. The real one even had nose art: bugs bunny on a flying carpet!
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Old Feb 15, 2008, 02:05 PM
X-15 Jockey
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I flew again today, I robbed the counterrotating prop setup from my flat P-38, they are 10x4.5 props. I was able to take out all of the right trim, and now just have a bit of left trim, with the battery on the left side of the fuse profile. Thrust is very good, as is hover power, it will hover pretty well, but without rudder it won't stay there forever. My motors are a little overloaded with these props, and speed was down quite a bit, and I had to switch to a 2100 pack to provide the current needed, now at 19 amps peak. this also put the CG a little more forward, and now I can't get it to snap/stall, it will start to rock the wings as it gets too slow, loops and rolls are still very good and tighter than with the smaller props. I think if I could find 9x4 counterrotating or 8x6 that would be perfect. It's interesting, it flies very much like a rudder/elevator plane with dihedral, very little elevator needed in turns, and if you let go of the sticks, it will rotate level again, with the extra mass of the motors out to the side, once you are in a fast roll, it will roll about a 1/8 of a turn after you let go of the sticks, then level out again.

Glides a bit better with the CG more forward, but still likes a little power on just before flare, I think those big props windmilling are creating some drag.

Frank
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Old Feb 16, 2008, 09:01 PM
X-15 Jockey
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I was able to find some counter-rotating props for gas motors that were 9x6, that made the difference, now I can switch back to the 1320 pack for 6.5 minutes of flight, and speed is now good, hover is still at half throttle and high and low speed handling are perfect, I now don't have any roll trim at all, but do have some up trim, since I moved the CG forward a bit more. I'll post some more video, I re-did the motor mounts with carbon tubes running back over the wing to support the motor, I've also had a few issues of the gas props not bending a bit when landing, they'll catch a tip, and instead of flexing, they are putting all the torque on the motor, and bending the motor shaft slightly, I've had to replace them with hardened shafts, we'll see if that does the trick.

Frank
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Old Feb 17, 2008, 12:29 AM
X-15 Jockey
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New motor mount supports did the trick, still one bent shaft, but that was an original, now have two hardened shafts. The non electric APC props catch the dirt, and don't flex, all of the force is transmitted to the shaft. Inverted flight and outside loops are very nice, slow flight, hovering, very controllable, slow flight is very forgiving.

It was a great morning, no wind sunny, 50 degrees, flew my F-107, Goblin, Mig21, Draken, Vertijet, Super Crusader, Flapjack, and X-15, flew for an hour and a half, had a lot of fun.

Here's some video my daughter took today.

http://www.rcgroups.com/forums/showp...47&postcount=1
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Old Feb 18, 2008, 03:32 PM
X-15 Jockey
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New video with landing gear!

I added gear today to prevent the prop tips from catching grass on landing, it flies great with it, almost vertical takeoff, and landings are a piece of cake, since I reinforced the motor mounts with carbon tubes, I attached the gear to the center of the tubes which takes the majority of the weight load too, this was just what it needed.

Here's the video:

http://www.rcgroups.com/forums/showp...37&postcount=1

Frank
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Old Feb 21, 2008, 09:49 PM
X-15 Jockey
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Plans posted

If you are interested in plans I can try to find the pdf, the original tracings weren't copied that well so i wasn't publishing them till I got them cleaned up.
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