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Discussion in 'Warbirds / Warbird Replicas' started by Saville, Oct 5, 2019.
Why not? Worked great on the Raptor. Oh, wait...
After all the discussion about making a reduced scale ME-262 I got carried away and built another mock-up. Some years ago I built a 70% P-39 and this time I chose 55% as the scale. Starting with a giant scale RC model model plan I made templates of all the cockpit area and using a large shop made planimeter blew them up to 55% of full scale. The construction is a combination of double wall corrugated from Uline Office Supply and some 1/4" plywood. Lots of Gorilla and Titebond glue. The skin is construction cardboard available at Home depot in big rolls.
As it turned out 55% is not really big enough unless you are a smaller person. I just finished the project and actually haven't sat in it yet. I have to get it off the rotisserie supports and on to the cradles before we can do a trial fitting. It will be tight. I think 65% would be a better design point.
I built the Nightfighter version with the two place canopy, but at 55% only a 12 year old could sit in the rear seat.
Here are some photos of the project and I'll post more in the next couple days with some people in it.
Cool..it wasn't big enough even with reclined seating ?
That's really impressive! Nice work.
Very nice, 65% might work for a single seater, between 70 to 75% will be great. Following this thread with great interest.
I like that mock up.
That mockup is awesome. A little larger and you at least got a nice cockpit for DCS world
And I have decided that the BD4 will DEFINITELY be my last built......sigh.....
Erik in Oz.
The trial fitting happened today and it's definitely small. The biggest problem is the width of the canopy sills which are about 2" under sized. If you notice in the photos I am sitting farther down in the seat leaving some head room unused, That;s to get my shoulders under the sills. The length is OK. I had to cut some off the bottom of the panel to get my legs under it.
Fun project, I'll hang it on the hangar ceiling next to the P-39.
The 262B would work as a two place homebuilt at 65% with an additional 2 inches added to the cockpit width and an inch to the height. No one would ever notice the slight scale departure and that would allow more comfortable seats and elbow room. The seats in the 55% one recline at 35 degrees much like a high performance glider. I measured the seats in a Longeasy and they are 45 degrees.
If a single place would suffice a 60% version would work wellwith the additional stretches mentioned above.
The next project to ponder is a large ducted fan, something in the 15-17 inch diameter range. There are some large EDFs, up to 250 mm diameter, on the market from Vasy and Schubler that produce up to 125 lbs of thrust. A 15 inch fan could produce up to twice that thrust. The difficulty, once you have an EDF, is how to power it.
Dude you read my mind.
Still working on this project having moved on to the ducted fans . I built a rolling engine/prop test stand some time ago and have adapted it for ducted fan testing. The advantage of the test stand is that it has a CVT drive so I don't have to guess at the pulley ratios to match the DF power to the engine. The CVT automatically adjusts the drive ratio. There's an 11 inch diameter DF on it now that uses Rolls Royce Avon compressor blades. They are currently set at the wrong pitch and I am working on a solution for that problem. As is the DF only develops about 20 lbs of thrust on 9 HP. I think we should get twice that with the right blade angles. Also have a 17 inch diameter version and some Russian jet engine compressor blades that's next in the test que. I have a 2si 35 hp engine to drive that DF.
Indeed at 14/17 in you will get plenty of thrust for real performance with short wing or bad airfoil. But ofor the siz and proper air flow after the blade.. you will not go with an electric motor?
I have not yet installed anti-swirl vanes or the after body streamlined pod. Swirl losses can be very high. Today I redid some of the instrumentation and finished the new ducted fan hub, one with ground adjustable pitch for all vanes. The final drive was a v-belt and was slipping so I have replaced it with a toothed timing belt and pulleys. Will take some more data on the fixed pitch fan tomorrow. At this time the efficiency of the fan is too low to consider converting to electric.
The ultimate plan is to add an electric motor to make the unit a hybrid with simultaneous IC and electric drive.
Vince, the nearly prone seating position shown in your photos is going to prevent you from getting any enjoyment out of the aircraft. It would be like the "Bally Bomber" B-17 replica that flew, but not well enough to enjoy and keep.
That would be a crying shame for your 262, same as it is for the Bally Bomber.
I very very strongly suggest that you measure the pilot seat angles and dimensions in a single seat racing sailplane (Ventus, AS-W20, LS-6, etc.) and scale up your 262 replica to allow that seating position to fit. The racing gliders are a very good balance between smallest usable size (to achieve minimum drag) and pilot comfort/ergonomics (cross country glider flights last up to 8 hours).
VasyFan makes a ducted electric fan that can produce up to 120#thrust with latest model. building a 55% single seat ME262 with infused structural carbon fiber skins for minimal might result in a flyable replica.
Vasy are near 110 lbs for like 10 sec at max. Don't confuse max power vs usable power... And same as you can't drive at 90% over a min.
I agree about the prone seating. The mock-up is built at 55% and as stated earlier I would consider no less than 65% with a little extra width added to the cockpit area. If I was serious I would build another, larger scale mock-up as it only takes a few days to put one together. Uline Office supply sells 4 X 8 sheets of single, double and triple wall corrugated that are quite inexpensive and very easy to work with. I tack things together with hot glue and final glue with Gorilla glue and Titebond Type III. If you the paint the structure with house paint, I use paint bought from the "OPPS" selection at my local hardware store, the structure is permanent. If you sort through the 1 x 2s at Home Depot or Lowes you can get decent stringer material.
We have another project going with 120 mm German electric ducted fans mounted on a real airplane. This project has also shown us that the published thrust and max power numbers for off the shelf EDFs from the RC model world are overly optimistic and we have several smoked units to prove it.
I'd be interested in knowing such seat angles. Some quick tests for seating options for me seemed to produce more upright seating than I have seen in diagrams of gliders.
Send a PM to BoKu/BobK, he will likely have all of that info. The earlier HP-18 glider (and the European BS-1 and Diamant gliders as well) was not very comfortable at all. I'm sure that Bob's HP-24 glider program was designed to be much better ergonomically. I'd bet he has comparison data on a whole bunch of glider cockpits.
The point I was trying to make about the glider cockpits was that a plump 200 pound guy can sit in the airplane for several hours and be able to fly safely. I know because the fat boy doing that once upon a time was me
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