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Discussion in 'Warbirds / Warbird Replicas' started by J Galt, Nov 30, 2019.
The Hornet was it's little sister.
Very cool cockpits, looks like a lot of work.
When you see the Texas Spitfire in videos it looks a little small around the pilot at roughly 75-80% (it's not a true scale of any particular size) but seeing the Titan P-51 at Oshkosh last year that thing seemed pretty big even at 75%. It was a high back version that I was checking out so that probably adds to the overall appearance of larger size.
So far looks like no single option has the most votes but 90% is ahead of 100%, maybe people are thinking practicality?
150% Fokker D-7, Just kidding
I would like to see a 70% scale done of the Grumman F2F done in wood and composite powered by a 5 or 7 cylinder radial. I believe price of build would be within a average mans ability and with both wings for lift at 70% size it would be a fair performing AC and able to carry a good size pilot or two.
Vega was pressure/bladder molded (opposite of vacuum bagged) into concrete forms.
Seems like an accessible "technology" for a range of more or less cigar shaped wooden fuselages.
Assuming access to a suitable bandsaw & widebelt sander to make the veneers.
Alternately, I've had flitches commercially sliced to a specific thickness for structural use. For airplanes, there might need to be a spec for the grain configuration and run-out.
I was thinking Alum bulkheads and longarons for main fuselage with wooden stringers and wood wings and tail group
British-built Mosquitos were made on wooden molds.
After they grew frustrated with wooden molds warping, deHavilland of Canada switched to concrete molds.
A few years back, a group of frenchmen built a wooden, half-scale replica of a Mosquito. They only had to "cheat" a bit on the cockpit canopy and exhaust covers. They had to enlarge the canopy to fit two frenchmen side-by side. The main spar prevents tandem seating. To hide cylinder heads (Lycoming) they installed enlarged copies of the exhaust flash hiders common on Mosquito night-fighters.
Half-scale is a bout the minimum practical size for WW2 replicas, but you still need to cheat a bit with canopies and control sizes. Most comfortable replicas are 70 or 80 percent scale.
I would never built a 100 percent replica because many of the originals had "squirelly" handling and exhausted 19-year-old pilots. Modern weekend pilots need more docile handling.
Since the Mosquito replica has already been done, I am switching my sketching to an asymmetrical Blohm & Voss 141 recce plane. Half scale leaves barely enough room between the main spar and propeller. That small scale would press the pilot's shoulders against the main spar if he/she does not want to risk losing toes to broken propeller blades. Though I might have to go to a slightly larger scale to put the pilot's eyeballs forward of the leading edge. That would produce a wing span about 25 feet and 100 horsepower should be enough, so I will try to "borrow" an engine cowling from a WAR FW-190 to wrap around a Continental O-200.
Ideally my BV 141 replica would be made of sheet aluminum hydraulically-formed around CNC cut blocks and held together with pop rivets. Given the light weight (1000 to 1500 pounds) construction techniques would resemble Thatcher, Hummel Bird, BK, RV, etc.
Alternately, it would be CNC cut from foam blocks with fibreglass and epoxy vacuum-bagged around the blocks.
The guy who taught me how to do PFP molds ; him
and his daughter, rented a Dino Ferrari, and molded
the entire car, (in sections) in under 3 days !!
PFP = Plastic faced plaster ; usually done in Hydrocal
or Ultracal-30 , mixed with hemp for strength. Both
plasters have a low expansion rate, when hydrogenated
and they make epoxy surface agents that sticks to it,
A Cessna 182, has a wingspan of 36' ; so a 70% scale
XP-38, (52' full scale span) , would be Perfect , and have
plenty of room inside for the pilot, and still look scale on
I Like the XP-38 Lightning Best , because the engine
pods look more streamline than the next ones out, with
those giant air-intakes ; they were needed for cooling.
Electric or water cooling , could remedy the cooling part
and the air intakes could be some what hidden in the lines
of the original.
Personally, I like stand-off scale replicas that are easy to build and fly as light aircraft first and decent replicas second since I don't have the money or the motivation for something close to full size or power. The Sidlinger Hurricane is a good example.
My ideas for replicas start with running the numbers for an equivalent light plane of the same aspect/taper ratio as the original; generous allowances for pilot weight, fuel, etc.; conservative empty weight estimates; and a chosen powerplant. I also prefer all wood and fabric or wood and fabric wings with welded steel tube fuselage (tails can go either way) but that's not relevant to the scale question.
I have always liked the Miles M.20 prototype "emergency fighter" and the fixed gear simplifies the replica. The 100 hp Aeromomentum AM13 (1.3l Suzuki 4-cylinder auto conversion, 170 lbs dry weight including redrive) seems like a good fit. I didn't start with the scale, I ran the numbers and that gave me the scale, in this case about 75%. Here are some quick numbers and a couple of pics, PDF attachment is the same performance estimate but with a few more details.
PRELIMINARY PERFORMANCE ESTIMATE FOR PROPELLER DRIVEN AIRCRAFT
A/C Type: 75% Miles M.20
Notes: Aeromomentum AM13
Crew weight 250 lbs
Fuel + baggage weight 100 lbs
A/C empty weight 450 lbs
Total weight 800 lbs
Stall speed (flaps up) Vs1 45 mph
Climb airspeed 58.5 mph
Climb airspeed 85.8 ft/sec
CLmax 1.5 (flaps up)
Aspect ratio 5.11
Induced drag factor K 1.1
Wing span 22.9 feet
Mean wing chord 4.49 feet
Selected rated shaft power 100.0 BHP
Take off run 259 feet
Rate of climb at 1.3 Vs 2636 feet per minute
Max level speed 162 mph
Cruise speed at 75% power 147 mph
Flaps up stall speed 45 mph
Glide descent rate at 1.3 Vs 458 feet per minute
P-38's are very cool, they had one visit for the Warhawk Museum airshow here a couple years ago. It was very quiet.
I had never heard of the Miles but that is really neat.
The Miles M.20 prototype was ordered in July 1940 at the height of the Battle of Britain and first flew a little over two months later, thanks largely to the fact that it used as many Miles M.9 Master trainer parts as possible. Despite the wooden construction and fixed gear it was a little faster than a Hurricane (though slower than a Spitfire) with the same Merlin engine and the extra space in the wings left room for substantially more fuel and ammunition than the other fighters. By that point, fears that the RAF was going to run out of fighters before the Luftwaffe ran out of steam had subsided. A second, slightly more refined prototype was built in 1941 for possible Fleet Air Arm use as catapult-armed merchant (CAM) ship aircraft but they ended up using tired early Hurricanes instead. So only the two prototypes were ever built and the M.20 never entered production.
Forgot a detail, at full size.
That FFVS would be great, it's like a radial 109. Could probably do a 90-100% scale clone using an R-985 as long as the payload is strictly pilot and a bag or two
Any thoughts/opinions on the WAR airplanes? They’re roughly 60%.
Having seen a bunch in various museums (usually in the kids’ section), they don’t seem like they’re quite enough airplane to be something that you would want to fly regularly. Had they been 3/4 scale with 150-ish horsepower and a jump seat I bet there would be more at fly ins and fewer in mausoleums... I mean museums.
Someone smarter then me can comment on what the small size does with regards to handling in the air and on the ground but check out the first post in this thread for thoughts on the more diminutive replicas out there:
this replica mosquito was 3/4 scale (2 seater), a 50% single seater as an ultralight (300kg MTOW) is on my bucket list. The wing area will then be about 10.5m2 and get me under the 30kg/m2 wing loading requirement.
A scaled T-34 (about RV-8 size) could make a very nice airplane, but there was one offered as a kit that was not, AFAIK, successful.
If all goes well, I hope to start flying one of those next year. If all goes really well there will be an Isaacs Fury alongside it.
Since the Grumman F2F's silhouette roughly matches that of a Pitts Special, it should fly pretty good. Just compare control surface areas and balance - with a Pitts - before cutting metal.
I would probably start with a welded steel tubing fuselage concealed by composite panels.
That deep fuselage could hide a tall and fat pilot!
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