Well I've got the F-22 bug again, taking a break from my midi T-33 design, and I feel like twisting some balsa. I've been working on this design for about 3 years now. I had two Wattage raptors but they really spoiled the looks by getting the nose and canopy wrong, it just killed the looks, so as sometimes goes, the only way to get it right is to do it yourself. I orignally designed this for a single 90mm Wemotec Midifan but then started thinking I could use a slightly lower powered setup from my scratchbuilt A-10, but with 4S lipo instead of 3. So, I redrew some of the bulkheads for a twin. This has been a lot of work, and it's nice to finally see it start to come together. It lets me verify/confirm bulkhead shapes and see how much I need to adjust. I could use a couple more bulkheads in some areas to help shape the 3/32 balsa sheeting but so far it's doing ok. I had to strip plank the front of the intake/forward fuselage section due to the complex curves. 1/16 balsa would be easier to shape but with water/windex mix on the balsa the 3/32 strips soften up ok and I can get the twist I need.

I "plan" on making a laser cut semi kit available someday but who knows, maybe I'll just sell plans. I really should be working on the T-33 now and getting it flyable again but it's not going anywhere!

It will have EJF/Jet Hangar mini retracts. Going with a twin made a scale retraction angle necessary, the wheels/struts will retract outwards and up into the wing and should be covered by a gear door. A single Midifan would allow the gear to retract back and in so the wheels are on either side of the fan. It wouldn't be scale but it would mean gear doors wouldn't be a must since the holes wouldn't be on the side of the fuselage they'd be on the bottom (lots of drag that way though).

The model now is just big enough for a 90mm fan if a few bulkheads are redrawn. It would make the upper fuselage taller/deeper than it should be but I think it could be done in a way that wouldn't ruin the looks like what happens on some singe fanned twin models.

Nice Ed!
Any reason for going with the twin 69mm as opposed to the single 90mm?

Well I thought about semi retiring the A-10, it's getting kinda boring and I though the setup in it would be just about right in the F-22. The MF480s will pull less current on the same 3S setup as the Kyosho fans in the A-10, so I can maybe increase to 4S lipo and not fry the motors. I may pull close to 60 amps though, haven't done any testing just going by what others have said. Also the twin let me drop the fuselage a bit to be more scale so I can have the engine humps. The rear 4 bulkheads would have to be changed for a single midi install, might be able to cut both sets of bulkheads.

Also my midi is going to be in the T-33 so it's spoken for at the moment. For single midi I might upsize it a bit to the same length as the F-18, 51", currently its about 3" short of that.

Hi Ed,

It's truely amazing what you guys do here on the E Zone! I can't wait until I can back home from Kuwait to restart my hobby When and if it becomes available, I would be very interested in a set of the F-22 plans, for a WeMoTec 90mm setup. I still got 17 months of sand to eat but when I leave it's goingbe on Keep up the good work and inspiring masterpieces!

Ken In Kuwait

Well I made a bit of progress on the F-22 over the holiday weekend but not really enough considering the time I had.

The first pic shows a view of the left intake ducting made from donut box cardboard (mmm, dooooonuts). The line on the bulkhead in the foreground is the vertical centerline of the fuselage. The ducting runs between two light ply bulkheads, and is held in place with CA. Forming the section going from a parallelogram inlet with tight corners to a round duct was tough, but I've done this type of ducting now several times and I think I've learned all of the tricks. I don't know if someone who hasn't tried it before could pull it off or not, might have to go with strip planks of balsa or preformed/vacuum formed tubes if a kit was ever released.

The second pic is taken from the left side looking back toward the back of the plane, down the inlet ducting.

The third pic is sort of the same view but back aways to show more of the fuselage.

Boy, what fat hands, I'd never make it as a hand model!

Looking forward to seeing your bird take shape, Ed!

Something in the lowest picture of your last post caught my eye. There appears to be a texture inside the round portion of your ducting. A bunch of little circles layed out in a pattern. Actually, I'm really not certain what I'm seeing in there? Donuts maybe?!

Tom

That's printing on the donut box...but I guess it does sort of make the round shape visible as well! Some may choose Count Chocula cereal or Trix!

Awesome project Ed. I will be following this thread very closely

Excellent subject. Nice to see a real scale version in EDF.

Spar

Good eye, Thomas!

But the experienced doughnut addict will tell you that those are the tell-tale green dots of the famous Krispy Kreme brand!

He he

You know, I WAS wondering if Ed might be experimenting with a dimpled material in his ducting. Along the lines of golf ball design.

I've been thinking about the ideal surface finish for inside our ducts. Who knows, maybe microminiature "donut bumps" will be all the rage by this time next year. I'm inclined to think that a smooth finish, however, is probably not the best.

Not trying to redirect the thread though! Show us more pics, Ed!

Originally Posted by Thomas Nelson

He he

You know, I WAS wondering if Ed might be experimenting with a dimpled material in his ducting. Along the lines of golf ball design.

I've been thinking about the ideal surface finish for inside our ducts. Who knows, maybe microminiature "donut bumps" will be all the rage by this time next year. I'm inclined to think that a smooth finish, however, is probably not the best.

You know I've been wondering about that. I've seen it discussed here over the years, weather laminar flow or turbulent flow is better in inlets, and was thinking about it when building the front part of the inlet ducts from balsa sheet, wondering if I should cover the balsa with Monokote trim sheets to make the smoother. I'm not familiar enough with laminar vs turbulent flow and all that.

I know of the experiments with laminar flow Nasa has pursued over the years, the first with that B-66 that had a wing with small holes drilled into it and they used a small turbine to suck the boundary layer into the wing in an attempt to decrease drag. Keeping the holes unclogged with debris was the problem. They also use the F-16XL prototype a few years ago to fit a laminar flow section.

Turbulartors/vortex generators are used on full size aircraft to "energize" the boundary layer in front of and over control surfaces so that they are more effective at lower speeds...I've seen lots of those retrofit kits on GA airplanes at work and have read a bit about them.

Another thing I've noticed is a large area of small holes in front of the inlets of the F-18, F-15, and even an F-4. I'm told this is for boundary layer control, I guess it sucks away the stagnant boundary layer somehow? There's also the "hush kit" that BVM was selling for the ducted fan airplanes that made you drill lots of small holes in the inlets.

This subject has popped up in the past and smooth vs rough ducting and I've wondered about that. I'd like to know which is better. Maybe someone will build two different versions of the same ducting and mount small turbulators in one to see if there's a difference in performance. The dynamic portion would be hard to test without a wind tunnel I suppose... Making the turbulators would be the hard part. Maybe line our inlets with 80 grit sandpaper? That doesn't seem like it would be better but I just don't know enough about all this to know. My ducting may have turbulators already, there's a bend of more than 5 degrees and an overlap of the cardboard that is difficult toget really smooth. I've line the bend with aluminum tape but it's not pefectly smooth. Surely there's turbulence there but is that good? My understanding has always been that turbulence is to be avoided in inlet ducting, but maybe stirring up the boundary layer is a good thing? I doubt it will have a huge impact on performance in though.

Looks cool Ed. Keep the photos coming.

Daren

That is a very nice F-22 you are building. I just started making molds for an F-22 with twin 90s. I am a bit concerned about the recent thread on Lockheed asking for money to use their copyright planes? I plan on selling a few to pay for the project. Where did you get your documentation? I posted some early pics on rcuniverse because I cannot get my files small enough to put on rcuniverse. Today I put the first layer of filler on the plane and it is starting to look good.

Thanks for the compliment! The sections I got by both eyeballing, measuring photos, and cutting up a plastic model into sections. I used the top and side view from the model kit instructions to derive the side and top views on the plan, with some adjustments. I've got a large side view from another source that has a slightly different shape to the canopy. I guess that's normal in 3 views. If I had to do it over again I'd have cut the model up more and used a side scan of it down the centerline to get my side view.

I started about 3 years ago after getting tired of looking at the lame attempt Wattage made (but they probably didn't get sued), then scaled up my initial drawings to a larger size.

I'm a bit concerned about the copyright discussion going on, but if I did kit it I don't expect to sell thousands of copies. Can they police every jet rally and email? I might seek a licensing deal but it sounds like they jack up the price after the first term and don't come through. Who knows. You'd think that they'd be happy to have a representation of their product out there that actually looks like an F-22...free advertising. I'll leave that discussion for that other thread.

Twin 90 mm eh? How long? Sounds cool. A buddy of mine was thinking of doing a twin 90 mm of something, this was one of the subjects but who knows what he'll pic.

thats looking really cool