More progress...

Well I was hoping to show the jet done but my efforts have been frustrated with the mounting of the V-stabs.  My original design placed the spindle location to far forward:

The problem was that it required too much torque for the servo to move.  I cut out another V-stab to test out a better location for the spindle point.

I was also having problems for mounting brackets for the stabs. I was trying to go for quick and dirty and use depron and balsa without reinforcing it with brass tubing.  So now I had to rip out the brackets and move them back on the fuselage:

 I haven't had the chance to reinstall them but on the plus side I was able to install the ailerons and fan mount:

I was originally going to mount the ailerons with hinges but decided to speed things up and just use tape.  The fan mount was made out of depron and glued to the fuse with gorilla glue. I will trim it down a touch before the first flight.

All for now!

Starting to look like a jet!

Getting pretty close slapping on some electronics and go flying!  Added on the vertical shapes, shaped the airfoils and cutout the ailerons. I made a engine motor mount and painted a canopy to round out my progress thus far.  Next up is installing the V-stabs and ailerons.  Here's a pic:

That's it for a few days.  Have a good weekend!

Getting there!

Got a fair amount done today. Glued in the spar, cleaned up the verticals and glued the bottom pieces on:

I finally tried sanding and was pleasantly surprised how well depron can be shaped. Not quite as nice as balsa but it's pretty easy to correct mistakes.  I also built a inexpensive hot wire cutter! I gave it a go on another trial bulkhead.  I like it, better than cutting for curves in my opinion although cutting is better for straight edges; especially if they're long.  Below is the two trial bulkheads glued together:

Both sides had the outer edges finished by sanding.  The one on the left was cut with the hot wire cutter, the right with a xacto.  I rushed cutting out the hole but otherwise both look nearly identical.  One point that should be made is that my knife work was quite above my usual standard and the hot wire was faster for less mistakes so I foresee many a pieces cut with the hotwire for the larger model.

Verticals done

A quick update, got the vertical shapes done.  I have to admit that I'm still a little frustrated with how depron cuts. I still haven't try sanding but I'm struggling getting a nice clean cut. I'm strongly considering using a hot wire cutter. Anyway, here's a quick pic of the vertical pieces:

I'm hoping to run down to the hobby store and grab a couple carbon rods for the wing spar. After I install that in the wing, I can start installing the vertical pieces. 

Stay tuned!

It's Alive!

Made a little progress today.  I was able to cut out the horizontal spine today.  As I mentioned in my previous entry I didn't order big enough depron sheets so I had to glue the outer wings and the nose cone.  Not my favorite option but Ill most likely have to do that with the bigger model.  I have to say that depron is a bit tougher to work with than I was expecting but so far I have only been using xacto knife and have yet to try sanding or other "finesse" techniques.  Here's a shot of  PAV-1 with the stabs propped up:

I also too a crack at cutting out a bulkhead.  Below is a shot of a former at 1:13.8 which is very close to the 1:13.5 scale I want to build.  I inserted a 64mm fan for a fit check:

Coming along nicely and hopefully I'll have most of PAV-1 done by the end of the week!

First Foam Cut!

It's a small step forward but I finally started production of PAV-1! I'd like things to move much quicker but life can get in the way and occasionally errors can too.  I was able to get the plans printed out to a close enough scale, 1:23.5, so that I was able to cut some foam.  When I finally opened up my box of depron I discovered that I screwed up my order and didn't get sheets the size I wanted so they are a bit small.  This may not be too bad as it'll be good practice for building the big model.  I didn't have time to do much but I was able to cut out the V stabs:

In the center is the 50mm fan that I'm going to use to power it.  The stabs look oversized but they're correctly to scale, it's just there'd laid flat.  Heres another showing the jet next my F-35' just slightly bigger in scale:

The F-23's stabs, despite being smaller in scale are almost bigger than the F-35's wings! 

Hopefully more progress pics next week, stay tuned!

First F-23 Complete!

Ok not really...  My original intention was to start building my "PAV-1" 1:22nd profile jet today but I ran into a couple complications. Number one is that we adopted this little girl Tuesday:

She's a albino Great Dane that we adopted from the Mississippi Great Dane rescue and we had to drive out to Oxford MS Monday then drive back Tuesday which is 600 mi each way. 9hrs each way is rough! So we spent most of today getting her settled into our new family thus while I was able to get to the hobby shop to get some stuff I needed for PAV-1, I ran out of time and got to the print shop too late.  

So I tried to print out my plans in 1:22nd using a poster print option on my printer.  In case you're unfamiliar, the poster option basically takes the image and breaks it up into sections that fits on a standard 11 x 8.5" paper, this effectively enlargening it.  I had a helluva time trying to get the scale correct and all of my graphic programs kept freezing up when I tried to scale the image up above about 12,000 pixels.  I wrestled with this for a couple hours and this is the best I could come up with:

The top image shows my Sky Angel F-35 which is roughly 1:22nd scale that I'm shooting for.  As you can see it prints out to only 1:35 which is too small for even a 50mm fan.  Hopefully I'll be able to get the print shop tomorrow otherwise it'll be next week before I can even do that. I am lucky enough to fly for a living but the job requires you to be gone for a few days at a time and I'll be on a trip over the weekend. So hopefully I'll have some foam cut real soon!

Stay tuned!

Fox

Step 1, design considerations

The first step in any buld is basic design considerations.  Things like size and weight aren't just a consideration for such mundane considerations like transportation, but also compatability with radio and powerplant components are also a critical consideration.  When I first envisioned building a F-23A, I was thinking about about making it the same size as my Freewing F-15 which is ~ 1:17.7th scale.  The F-15 sizes out to about 44 inches long and a wingspan of about 29 inches.  A F-23 built to the same scale is 48 inches loninches has a wing span of 29.5 inches.  This is a perfect size since it'll fit easily in the back of my SUV and will leave me enough space to bring a couple more airplanes.

To make sure that this was a good plan I printed out some engine mount bulkheads to various scales.  To my surprise, the engine bays in the F-23 are quite streamlined, with minimal structure around them, not doubt for aerodynamic and signature reasons.  So at roughly 1:17th scale I could clearly see that even a 64mm fan would be a very tight fit and I'm not certain that a 70mm fan would work at all.  Another consideration is that the nozzles aren't placed right along the centerline at the end of the fuselage like previous generation of fighter designs but are run through troughs.  The only way the bigger fans will work is by placing their thrust lines considerably lower in the fuselage and this would require exhaust ducting that bends upwards then straightens out which would undoubtedly incurr a performance penalty and would require larger nacelles.  The latter is highly undesirable because I really want to capture the gracile lines of the production jet.

As you can see in the above photo, there's very little room to work with and a key consideration is running of electronics and associated wirring as well as I'm planning on belly landing and I'd feel much more comfortable with a smaller hole in the bulkhead.  Printing out some more sizes I saw that while I could go up to say 1:15th scale and run 64mm fans, I'm not convinced that the jet would be much lighter than going a bit bigger and choosing a high performance 70mm setup.  So more printing I came up with this:

The above photo is 1:12.6 scale and as you can see the 64mm fan is now the same size as the actual duct opening.  A 70mm fan should fit fine!  The good news is that the inlet, minus the diverter cone, is about 117% of the FSA of the changesun 10 blade fan Im looking at.  While a bit bigger than I was planning its still manageable for transportation and stowage with a total length of  70.5" and a wingspan of 43.5".

Finally my last concern is my approach to construction.  I've seen various methods and one in particular was appealing since it seems to be fairly easy and straight forward.  This approach is to cut out the plan-view shape, wings and fuselage, in one lage piece of thick depron then attaching bulkheads as required to form the basic shape.  The jet would then be skinned with thin depron.  As I've seen on build threads on the various RC forums, this approach looks to be too heavy.  So I'm leaning towards a more traditional bullet up approach by using bulkheads strung up along a jig with longitudinal stringers for the basic structure, certain areas will have extra support such as the radio and battery compartment along with the ducting as well as the engine mounts.  Most of the bulkheads will use 6mm or maybe 9mm depron with some reinforced with light plywood.  While I'm failry convinced that's the way to go, I was not sure if I had enough bulkheads on the scale plans I have.  So to make sure I printed out the two side views that shows bulkhead placement side by side and it appears to me that I should have enough:

I apologize for the poor lighting but you can see I have about 28 locations although some are too close to each other to be usefull.  

All I have for the next few days, stay tuned as I'll be starting up the profile "PAV" here real soon.

Welcome to my F-23A blog!  This blog mainly about my odyssey of building a scale flying replica of the F-23A; i.e. the jet Nothrop/MDC would have built had they won the ATF competition in 1991.  This blog is also about the F-23 in general and may branch out to include military aviation in general from time to time. 

The most obvious question I'm sure you have is what differentiates the F-23A from the YF-23? Well there are many changes to the basic design much like what LM did as the F-22 design progressed during the EMD phase after they won the contract.  As you can see below, the main changes were to lengthen the forward fuselage so that a small weapons bay for AIM-9s can be added ahead of the main weapons bay, cleaning up the aft deck of the fuselage, slimming down the engine bays (the thrust reverser requirement was dropped), bringing the engines closer to the center line, different inlet geometry and a larger radome.

A comparison to the YF-23 can be found here.  The YF-23.net site is a great F-23 resource. Another great source of interesting discussion is the secret projects forum and finally Scott Lowther's work in the form of his Aerospace Projects Review periodical is a fantastic source of information including plans and drawings. 

My plans for building a flying model are two fold. First step is to build a 1:22nd scale profile version out of 6mm depron with a 50mm EDF. This will allow me to get my feet wet in designing and building a model out of depron and getting a feel for the control set up and the CG.  I've been told that a RC model's CG is well forward so getting this accurate is essential before I put a lot of effort into a larger more detailed model.

After I complete and test the profile jet, I plan on building a 1:12th scale twin 70mm EDF jet out of depron. This one will be scale with a built up structure with bulkheads and skin out of depron with some key areas out of light plywood and carbon fiber spars.  I plan on light fiberglass application to give the skin rigidity and damage resistance.  Since the it will be a "belly flopper", i.e. no landing gear, certain areas on the bottom will have heavier glass reinforcement.  I'm hoping for a AUW in the 6-8lb area and shooting for twin changesun 70mm ten blade units that should give me 8-10lbs of static thrust.  If I can keep it light it should be a real rocket, just the like the real thing!

All for now, stay tuned for (hopefully) regular updates!

Fox