Building an F-16XL

[Matthew Sanders]

Hello FT Forum User! Let me start off by saying "XL" doesn't mean I'm making a huge F-16. Instead I'm making this:

^ Not your typical Viper


<sigh> Why am I doing this? Unlike most people on this forum who use fancy computer aided design, I use pencil, foam board, a yardstick, and math. So, instead of designing this from the ground up, I'm borrowing the XF Viper plans provided here on the forum by none other than @Mid7night (Thanks for the cool plane, Ben!)
So, I'm sure not too many of you know the story of this plane. Essentially, the USAF wanted a modern Fighter-Bomber, and two designs were submitted. The F-15E "Strike Eagle" (Winner) and the F-16XL (Didn't quite make it into production). Anyway, I've been wanting to do this for a while now, so this is where I will update you on my progress.

What I'm doing:
I've already cut the plans out of DTFB, so now I'm going to be assembling the XF Viper FUSELAGE ONLY for now, since the normal F-16 and the "XL" have near identical fuselages, with minor differences (Such as the exclusion of the Ventral Fins on the XL)
Later on, I'll probably modify the wings from the existing plans to create the XL's "Cranked Delta" wing. I have no idea if this will actually work, I'm using a 64mm EDF on 4s, so I'm going to try to keep the airframe as light as possible, because I have no idea if it will actually fly, and I'm secretly hoping that I can just make a flat wing like the Viggen and just fly on the thrust of the motor, but I need a light Airplane for that.
Alright, that's it for this post. Feel free to stick around, I'm going to start building now.

 

[Matthew Sanders]

Well, this is as far as I got today. It should be noted that it was as far as I wanted to get today. It should also be noted that I don't have the EDF installed yet, and it's pretty much taped together. The Vertical stabilizer is taped to the fuselage, and the canopy section of the forward fuselage is currently just taped to the intake.

I am now going to be working on the wings.

[EDIT] I don't want to make it seem like I am going to fly it with just tape holding it together. Once I figure out how I am going to do the wings, then I'll glue it together.

 

[The Hangar]

Great progress so far! I’m eager to see how this one turns out. It has some interesting history, thank you for sharing! I have the plans printed for Ben’s f-16 but haven’t built it, maybe I should start on it…. I happen to have gotten a 70mm freewing 6s 12 blade edf recently as well…

 

[Matthew Sanders]

Great progress so far! I’m eager to see how this one turns out. It has some interesting history, thank you for sharing! I have the plans printed for Ben’s f-16 but haven’t built it, maybe I should start on it…. I happen to have gotten a 70mm freewing 6s 12 blade edf recently as well…

Definitely! I must say, a 70mm EDF (4 or 6s) would be better in here, but currently I only have the ability to use my trusty 64mm 4s. So, I'm going to have to put it on a diet😂

 

[FoamyDM]

View attachment 208652
View attachment 208653
Well, this is as far as I got today. It should be noted that it was as far as I wanted to get today. It should also be noted that I don't have the EDF installed yet, and it's pretty much taped together. The Vertical stabilizer is taped to the fuselage, and the canopy section of the forward fuselage is currently just taped to the intake.

I am now going to be working on the wings.

[EDIT] I don't want to make it seem like I am going to fly it with just tape holding it together. Once I figure out how I am going to do the wings, then I'll glue it together.

Look! A Lawn Dart!

Kidding aside, that is look good.

 

[Matthew Sanders]

Look! A Lawn Dart!

Kidding aside, that is look good.

Haha! LOL! Yeah I hope I can make airfoil wings so it doesn't become a lawn dart! I am prepared to make flat wings, though.

 

[Matthew Sanders]

Update Time!
So, I have installed the 64mm EDF. I made the thrust tube with a minimal taper to increase static thrust, yet have just enough taper to allow for flight speeds. I have totally glued the fuselage together, and I must admit that I briefly considered just cutting out the stock wings and making it a legit F-16. But, this is my first experimental aircraft since March, so I will press on with the XL design.

^This looks like something out of Buck Rogers!


I'm still not sure how I'm going to design the wings, as I still haven't found any angles. I also don't know how I'm going to make the cranked delta airfoil. I want it to be an airfoil, but currently I don't know how I'm going to do that. Since the XL has inboard AND outboard control surfaces, what I think I'm going to try to do is have dual elevons and try to incorporate CROW braking. It's just an experiment, I'll set it up like it is on the 80mm FMS Rafale.(Which I don't actually have, but I can watch videos on how to set that up.)

 

[Whit Armstrong]

Unlike most people on this forum who use fancy computer aided design, I use pencil, foam board, a yardstick, and math.

Us youngins with our technology...

 

[Matthew Sanders]

Us youngins with our technology...

Actually, I'm 18! I'm a "youngin" who prefers the ways of the wise. We went to the moon with slide rules, after all!
All kidding aside, I don't really use computers to design because I don't really know how, and my method works well enough for what I do.

 

[Matthew Sanders]

Another update:
Still trying to find accurate wing measurements. I've calculated that the fuselage is approximately 1:13 scale. So, I need to get the wing measurements to scale down to 1:13. I AM closer to getting the wing design, because I have the angle measurements of 70 degrees inboard and 50 degrees outboard. I have contacted the NASA Armstrong Flight Research Center (Formerly Dryden FRC) which flew the aircraft for Laminar Flow experimentation after the Air Force chose the F-15E. I hope to hear back from them soon.

 

[Matthew Sanders]

Update:
No luck with NASA. I just contacted none other than Lockheed Martin who owns the rights to everything F-16 related to see if they would be able to provide measurements. I definitely did not expect it to go like this but, hey, I'm still trying!

 

[FlamingRCAirplanes]

Keep it up! Also, looking good!

 

[leaded50]

Update:
No luck with NASA. I just contacted none other than Lockheed Martin who owns the rights to everything F-16 related to see if they would be able to provide measurements. I definitely did not expect it to go like this but, hey, I'm still trying!

ifyou have 3D view drawings (easy found at Google) you can scale and measure it correctly.

 

[Matthew Sanders]

ifyou have 3D view drawings (easy found at Google) you can scale and measure it correctly.

Hmmm. I had thought of that, but I noticed discrepancies on some of them, so I dismissed them as "unofficial" and, thus, inaccurate. I'll probably end up going this route. Thanks a lot!

 

[leaded50]

Hmmm. I had thought of that, but I noticed discrepancies on some of them, so I dismissed them as "unofficial" and, thus, inaccurate. I'll probably end up going this route. Thanks a lot!

control measure drawings, eg wingspan from top and front... easier to see if can be correct.

 

[Matthew Sanders]

First of all, I must apologize for such a late night post. Second, I must give a HUGE shout out to the person who has quite literally saved this project. That person is @leaded50 You, Sir, have given me the necessary information to make this project a reality! Thank You so much! Thirdly, having measured the 3 view on my iPad and converting the scale using an online scale calculator, I measured the shape out on foam board, and now I am proud to announce that I have my wings cut out (FINALLY!) These are flat foam board, because I don't intend to fly with them. They are merely meant to show the dimensions. I will build a second set of wings with a KFM airfoil tomorrow hopefully. Without further ado (because I know you have all been so patient, and thanks for bearing with me while I stumbled through the fiasco that I called a design process) Here's the pictures:

Ok, so you're probably wondering what those are on the wingtips. Those are AIM-120D AMRAAMs (Advanced Medium Range Air to Air Missile) They came from the Eflite F-16 70mm Thunderbird. I cut the missiles off the rails because the T-birds don't fly with missiles! They work nicely on this project, though. Here's a close up:

That's it for now! More updates probably tomorrow (11/14/21)

Gee, it would really be a shame if this experimental model crashes. I hope it flies.

 

[Matthew Sanders]

Morning update: I colored in the canopy with a black sharpie, and I added the parachute area by the tail.

Now on to the airfoil wings. Does anyone have any suggestions for how to do the 70 degree sweep airfoil? I am thinking of doing something like this:

Let me know if you think this is a good or bad idea.

I just want this to work, but it won't work without a proper airfoil. Oh, and looking at it, I'm not so sure there's enough wing area to keep it airborne. I'll definitely still try it, though.

Also, I'm extremely concerned about the CG. I really dunno where it should be. The online CG calculator doesn't allow me to make measurements for a cranked delta wing. Any thoughts?

 

[dap35]

Morning update: I colored in the canopy with a black sharpie, and I added the parachute area by the tail.
View attachment 211727
Now on to the airfoil wings. Does anyone have any suggestions for how to do the 70 degree sweep airfoil? I am thinking of doing something like this:
View attachment 211730
Let me know if you think this is a good or bad idea.

I just want this to work, but it won't work without a proper airfoil. Oh, and looking at it, I'm not so sure there's enough wing area to keep it airborne. I'll definitely still try it, though.

Also, I'm extremely concerned about the CG. I really dunno where it should be. The online CG calculator doesn't allow me to make measurements for a cranked delta wing. Any thoughts?

You could do a KF2 or KF3 airfoil. No folding, just doublers

 

[Matthew Sanders]

Hmmm, maybe I will do that. I'll look into it. Thank You for the suggestion!

 

[Hoomi]

If I ever built one, I would have to eschew the Lockheed Martin labels. The F-16, including the XL variant, were General Dynamics Convair designs.

Granted, that was before Bill Anders gutted the company and sold off just about every division he could find a buyer for...