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Old Mar 12, 2008, 11:43 AM
X-15 Jockey
burkefj's Avatar
Joined Oct 2006
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Profile F-104 Starfighter

Well, I just couldn't bring myself to put the "round" GAD starfighter that I got for xmas together, since I wanted something a bit bigger, so some more drawing and cutting....

Boy is that wing small, still should be around 1.6 sq feet, 55 inches long, and the wing is pretty far back. I'm hoping that I can get by with a 1320 pack for CG, and keep the weight around 15-16 oz. We'll see. I did add 1" to each wing, but I don't think it's noticable.

Taped together frame is 7.2 oz so far, and dry CG is coming out a little forward of estimated CG, which is good.

I'm using a carbon tube down the middle, a spliced center fuse/tail section, two spliced body doublers for the fuse outline, and two intake doublers to simulate the intake, will run a full flying T-tail. Same old Grayson parkjet for power that works so well.

Frank
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Old Mar 12, 2008, 12:27 PM
Kiss the Sky
electriceye's Avatar
Dorking, Surrey, UK
Joined Jul 2006
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Interesting build-You have these profile jets down to tee!! It will be interesting to see how you get on.
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Old Mar 12, 2008, 05:41 PM
agriebel's Avatar
Madison WI
Joined Aug 2003
1,805 Posts
looks good! I'll be watching this one..
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Old Mar 12, 2008, 05:43 PM
X-15 Jockey
burkefj's Avatar
Joined Oct 2006
2,438 Posts
I picked up some blue trim sheets, I think if I'm careful I can do the Nasa white with blue trim/yellow stripe on the tail, and won't have to paint it white and save a little weight. If this one flies well enough, then I might do a painted version, or rip off the trim and paint this one.

Frank


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Originally Posted by agriebel
looks good! I'll be watching this one..
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Old Mar 13, 2008, 01:55 AM
X-15 Jockey
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Joined Oct 2006
2,438 Posts
more progress

Here is where she is at, I've got one side finished, the tail attached, just need to do some rounding on the right side, and do the decals, then glue in the wing, and put on the electronics, another couple of hours or so. CG is now right about where I want with the tail and everything placed but the motor/battery/esc, should be no problem getting CG, Fuse with decals, and tail and stick mount is now just under 9 oz, still have hope that the finished plane will be 15-16 oz with a 1320 pack.

I found that since I used a hollow carbon tube for fuse reinforcing, and it ran all the way to the nose, now all I have to do is insert a 1/8" carbon rod into the hole for the pitot tube, I can just pull it out for display, or push it in flush for flying


Frank
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Old Mar 13, 2008, 06:03 AM
Now in TN!
J Morgan's Avatar
Chapel Hill, TN USA
Joined Apr 2001
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Looks great Frank.

J
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Old Mar 13, 2008, 12:21 PM
Kiss the Sky
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Dorking, Surrey, UK
Joined Jul 2006
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Yes, very nice!!
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Old Mar 13, 2008, 12:59 PM
X-15 Jockey
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Joined Oct 2006
2,438 Posts
Thanks, yes, I'm really getting fond of this one, should finish up the right side, and electronics tonight and do the maiden on saturday if the weather holds. CG from the calculator looks like it is just aft of where the leading edge at the tip would intersect the fuse, the calculator should be close since I don't have any fuselage lift which would move the CG more forward.

Hopefully, longitudinal stability will be ok, as the CG is near the center of the side view...

Frank


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Originally Posted by electriceye
Yes, very nice!!
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Old Mar 13, 2008, 01:16 PM
DELTAS RULE
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tehachapi, CA
Joined Jan 2006
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frank, looks cool! most 104 models have the CG about where the root of the wing meets the fuse. this is how it was with stackers 104, and J's pusher verion, maybe just barely after of the intersect, but again, this was with a full fuse, so not sure how the profile will effect that.
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Old Mar 13, 2008, 03:16 PM
X-15 Jockey
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Joined Oct 2006
2,438 Posts
Yes, my X-15 that had an X-form fuse and CG also was at the root/fuse intersection, but that was because you had the fuse lift, without that, it should be just a normal wing CG calculation taking into account the tail size and distance, so I expect it to be further back, where the wingtip would intersect the fuse if you extended a perpendicular line, so I think for the 104, it actually will be easier to get the CG with this plane because it is further back. At least in theory

Frank



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Originally Posted by corsair nut
frank, looks cool! most 104 models have the CG about where the root of the wing meets the fuse. this is how it was with stackers 104, and J's pusher verion, maybe just barely after of the intersect, but again, this was with a full fuse, so not sure how the profile will effect that.
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Old Mar 14, 2008, 11:29 AM
X-15 Jockey
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Joined Oct 2006
2,438 Posts
Maiden!

Finished it up last night, final RTF weight was right around 16.5 oz.
Motor runup showed hover power at around 65% throttle. It did feel like it wanted to pitch up when held vertical, so I put in some down elevator trim.
I also programmed 40% flap to try out during the flight.

It was a bit drizzly and windy this morning, but that's never stopped me:

First up was my V-1 Buzz Bomb, I replaced the grayson parkjet and 2100 TP pack with a grayson megajet, and TP 2200 25C pack, they compensated for each other and the CG stayed where I had it.

Hand launch still pitched down somewhat, but it definitely had more power and was a lot more fun.

Starfighter:

I throttled up to 70% throttle since I didn't want torque issues, and gave it a nose up toss, as I was afraid, it pitched up, but quick full down got the nose down and it continued to climb. It was very pitch sensitive so I brought it down and landed, moved the battery forward an inch, and reduced elevator throw. Second hand launch still pitched up a bit, but it just kept on flying up and up.

Roll rate was very fast, it looked like it wasn't perfectly axial, but I think that is because the T-tail makes it look that way. Loops were much tighter than I expected and you can get it to mush around the loop if you add power and a lot of elevator. Split Esses and cuban eights were great. Low speed flight was much slower than I expected, it didn't have any bad stall habits, it truly is a park flyer. I tried the flaps, but since slow speed was already so good, it didn't seem to make a big difference, I didn't notice any pitch changes with flap applied.

Vertical had plenty of power, it did want to go past vertical in a zoom, most likely needs just a bit of thrust offset, but nothing a little down elevator didn't handle. I didn't notice pitch changes in level flight with throttle changes, other than just a bit of climb on full throttle.

Inverted was a little hard to hold, it didn't need a lot of elevator but the roll rate is so quick, and with the motor above the axis when inverted, I had to fight it a bit. Landings were very nice, being still a bit pitch sensitive, I over flared twice but still managed to eek in a nice touchdown. High speed flight wasn't blazing in the headwind, but it looked really good.

Turns will lose altitude if you don't keep a lot of elevator on, if you do that you slow down, so you need to keep a bit of power on and keep the pitch control coming, or you just live with a little drop as she comes around.

I did notice a bit of side to side wobble, when the wind gusted, most likely the long forward nose momement, but it didn't cause any issue.

All in all, i was pretty happy, it looks great, and i've always wanted a starfighter. My wife, Sophie, was kind enough to model the finished plane so you have something better to look at than me

Frank
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Old Mar 14, 2008, 12:06 PM
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vittorio veneto (tv)
Joined May 2006
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Any possibility you give us some drawings?
Thankyou
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Old Mar 14, 2008, 12:58 PM
X-15 Jockey
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Joined Oct 2006
2,438 Posts
You know, I figured there were a bunch of starfighters out there, so this is the one plane I didn't make tracings for However, it isn't too hard to replicate it if you don't mind waiting for a week or so, maybe less.

Frank



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Originally Posted by robonave
Any possibility you give us some drawings?
Thankyou
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Old Mar 14, 2008, 12:59 PM
Flying Fatboy
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Tampa, FL
Joined Apr 2003
1,295 Posts
This project is looking good! BTW, The F104 is my favorite aircraft.

Regards, Bill
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Old Mar 14, 2008, 01:01 PM
X-15 Jockey
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Joined Oct 2006
2,438 Posts
Another flight

So, I decided to put a battery on the charger while I showered for work, the sky got suddenly blue so what the heck.

Wind was even more gusty, but with my battery moved another inch forward, it was perfect, now I don't notice the pitch up on launch, just a slight amount, roll rate is great and loops are nice. I tried now 75% flap, still no pitch change, but it actually seemed to fly a bit nicer, less elevator in hard turns, and I was able to get it to stop mid air in the head wind and hover, landed with the flaps on and it was nice and predictable with a mild flare and it slid about a foot and stopped, really really nice, handled high wind very very well, I'm getting about 9 minutes on the 1320 pack.

Frank
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