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Old Aug 19, 2013, 08:31 PM
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Oshkosh, WI
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Build Log
My 70" twin 90 F-23A

Been hesitating on posting this thread, as I'm such a slow builder, so might put you all to sleep. Please bear with me.

I was hoping to get some advice/suggestion along the build, so that's may main incentive.

I was following the YF-23 thread Unclecrash (u/c) had been updating; but it has been dormant of late. I understand life & other interest may have got in its way.
Hope he resumes his effort.

Phil Lin
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Old Aug 19, 2013, 08:45 PM
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Oshkosh, WI
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Why F-23A

The F-23A was to have been the production version of the YF-23, had Northrop/McDonnell-Douglas been awarded a contract in ATF entry against the F-22 Raptor. As in such a hotly contested project, there's still some controversy as to the merit of the F-22 win; but we'll put that aside for the moment.

The hot=wired foam segment of model building had me interested, as I don't have the skill nor talent to carve from foam blocks as falcon5, CN & others have demonstrated.

I wanted to improve my meager 3D CAD skill; and the timing was such as Wisconsin winter had forced me to stop my other project, so this project jumped my queue & now would not let go.

The hot-wired foam segment method of building, as u/c, D_fast & others have shown, seem to promise a fast building & lighter weight model.

I purchased the F-23A 4-view downloaded from www.up-ship.com, & thought I can have a rarely built model project
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Old Aug 19, 2013, 08:51 PM
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F-23A vs YF-23 Differences

For those who have not had the chance to pore over their drawings, there are noticeable differences between the prototype YF-23 & the F-23A intended for serial production, as was the case with the F-22, . There may be others, but to me, these mainly are in 2 areas:-
1) The rounded air intakes of the F version vs. the trapezoidal intake of the YF. This also carries true for the fuselage contour lines; e.g. engine pods.
2) Less pronounced chines on the Fs compared to the more SR-71 (F-12) look on the YF.
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Last edited by PhilLin; Aug 19, 2013 at 11:54 PM. Reason: corrected plane referenced
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Old Aug 19, 2013, 09:02 PM
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Oshkosh, WI
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Okay, I might be boring you all. So I thought I'd attach a printout from my 2.5 mos of CAD work, from which I put together the template laser cut file. There were a few trials & tribulation but finally persevered enuf

Hope its the correct file

Phil Lin
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Old Aug 19, 2013, 09:20 PM
EDF Jet Jam 2015, May 28-31st
eatond's Avatar
United States, MO, St Charles
Joined Nov 2002
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Hi Phil,
interesting project, definetly not boring. Have you made a decision yet on which 90mm fans you'll be using?



Dan Eaton
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Old Aug 19, 2013, 10:37 PM
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Thx, Dan! Glad you're interested.

Yes, I had decided on 2 x JetFan 90's. Don't know if they're v1 or v2? They were my X'mas presents (from me ). I have one located in the plane! Will attach a pix of it later.

Phil
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Old Aug 19, 2013, 10:52 PM
Do it Right, the first time!
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United States, MN, Hermantown
Joined Dec 2008
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OK, now that you have our attention how about some numbers?
WS-L-, what Kv on the motors , 6s or bigger?
Inquiring minds need to know.
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Old Aug 19, 2013, 11:03 PM
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Glad you asked, Cooler.

I'm building to the scale of 1 inch = 1 foot (or 1/12 scale). So the WS is about 45", fuselage length about 70.5".

I'm hoping AUW wud come to about 15-lbs; but its a long way to go yet....
So I can only finalize the kv depending on the final AUW. I'm expecting maybe 10s packs (12s if req'd), & wud avoid pushing the motor too much. The already cut main fuse foam segments are so light, its encouraging

But this thing has over 930 sq-in wing area (per classic calc.)

Phil
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Old Aug 19, 2013, 11:22 PM
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cont'd.

Some of you CAD whiz can see from attached in post #4 that my CAD software has limited capability.

Some of the problems I ran into at the start, e.g. a tendency for necking in between known x-sections, or starved cow look. Luckily, we have D_Fast on the forum. He is very knowledgeable with CADs; & he suggested using the old lofting technique. It was a way out for my s/w pkg.

The downloaded 4-views already gave more sections than most dwgs (16 known sections). But for use with the foam segment build method, I needed about 34 sections for the 70" fuse (not counting the nose & exhaust cones.

Early on, I decided to use as many of the original fuselage x-sections from the downloaded dwg in order to preserve scale fidelity. I was able to use 14 of the 16, but this also meant I could not always maintain constant 2-inch spacing, the thickness of the stock foam sheet.

Phil
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Old Aug 19, 2013, 11:33 PM
Do it Right, the first time!
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United States, MN, Hermantown
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That's big boy! Your build will make addition to this forum--and I'll be following along.

By the time I get my Scorpion done, no paint--it will be way too cold up here for that, I'll start back on my 1/7th scale Sabre. Wing area is about the same as yours. Mine is WS=65.5" ( the 6-3 wing) L = 63" approx 14-15lb. In fact I just got the retract units (mains) today. Got to buy the stuff when I can!
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Old Aug 19, 2013, 11:48 PM
deltas are cool
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Tehachapi ,CA.
Joined Apr 2006
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my understanding of the F-23a was that the valley between the motor pods was going to be filled in . i have a friend that was a eng. on it i'll see what he knows.
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Old Aug 20, 2013, 01:22 PM
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Oshkosh, WI
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I'm taking a break from working on the main gear retract mounting. I had a version worked out, but did not account for the electric actuator. So am on a 2nd version Things can go a bit quicker if I did not have to repeat some parts.

@Cooler, you seem to have a very full plate. Keep on building. I have been following your progress.

A/S, that is interesting to know; as the downloaded drawings shows the original design. And I only have a few pixies from the rear of the YF to show that part. Read from an F-23 blog that they completed a mock up for radar cross section testing. Its really quite amazing how much tooling changes they would have needed, from those used for the YF, in order to produce the F-23A version.

Phil
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Old Aug 20, 2013, 01:42 PM
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ps: Just wanted to say that the 4-views downloaded from Scott Lowther site is of very high quality, & very inexpensive. I paid for it so there is no doubt about whose intellectual properties I can use.

Phil
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Old Aug 20, 2013, 01:43 PM
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I'm having a lot of e-mail drop off with my service at this time. Perhaps I should come back in the evening when it is not so busy?

Phil
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Old Aug 20, 2013, 06:46 PM
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My Templates

So you can see from attachment in post#4 where I extracted the required intermediate x-sections from. The outside outlines for the templates were extracted off the 3D CAD drawing. After that, there were quite a bit of decisions to make before the insides of the templates can be done; e.g. position of the gears, fans & possible area & range of movement the packs will have to allow C of G adjustment.

The attached shows the first 20+ templates I compiled & sent out for laser cutting, as Im avoiding hand cutting these templates. But still I needed to hand cut 5 cardboard templates; mostly due to changing my mind to flange mount the fans, instead of beam mounting, as some of the templates in the pix wud indicate.

Phil
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