Torpedos with Wings - race plane

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Starman

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Inspired by the twin fuselage race plane thread ...

When you think about it the entire effort to build a new aircraft -if designed solely for the purpose of winning at Reno, is expended on something that only lasts eight minutes and has no other use . (and the speed record is slower than your grandmother going on holiday ....) As I keep saying -we need a NEW challenge that has some ongoing purpose and will bring out the best in designers --we need a challenge that has NOT YET been satisfactorily met --an 'undone' thing, just as the air races of the 1930s were pushing the boundaries that led eventually to the airliners of today that are faster than they ever were. I think we know what particular KIND of race-plane I refer to...

In any case the Dornier Do P247 and Do 252/3 are described and pictured on the web -google "images for.." for lots of pictures and links or for two short addresses -
http://www.luft46.com/dornier/dop247.html and Dornier Do P.252 ("Luft 46' includes spurious 'might have been' aircraft as well as actual designs that were just flown by the war's end or were close as these two were . They give a top speed of the Do P 252/3 as 930 kph or 577 mph --still much faster than the 'current' piston driven record.)
Starman -you have just about reinvented my 1974 HP 18 config but with more wing area than needed and a much longer nose gear etc (with flaps down the effective AoA is quite large already - HP's land nose DOWN as a bit of googling will show ) Now go figure the top speed and rate of climb with 1000 HP on board (!!!!) -you are into the WW2 fighter region and beyond --wouldn't that be a blast! I thought about what sort of 'application' such a thing could have and came up with the 'thrill ride' as the only real 'justification' (trying to "make' one of course ) the Virgin Galactic $200,000 'space thrill ride 'is in the same class. A two seater could give the average pilot (or aircar driver of the future) a real taste of what it might have been like to have a Spitfire or Mustang at your command . And then turn him loose in the single seater to go carve up some sky! --if you have seen the BD5J in action you will "get" it -- it looks much faster than it is and does those three thousand foot diameter loops and just accelerates vertically like nothing else . That and that alone is reason enough to build something like this -bugger the Reno races (but you could 'gatecrash' and just blow their speed measuring equipment...... (see "one good run" -the story of garage living New Zealander Bert Munro who broke a heap of Bonneville race speeds on a homemade 'junk' bike... Anyway,back to earth -the degree of difficulty in getting all the nitty gritty engineering details and engine/driveline.prop etc worked out will not be as simple as it might look or scale down with the aircraft size --see the history of the Pond racer as an example. I still haven't gotten out to see the local firm offering flights in a Folland Gnat (1/2 hour = $3000 +....) but THIS is the sort of market there could be . (the passengers donate to your retirement fund but get a free flight in your experimental sort of thing


A contra rotating prop allows for a shorter gear and some other advantages --two engines driving two concentric contra rotating props is also the logical best for a two seat "trainer' . Either Autoreply's "front end of a two seat glider (tandem) or other arrangements give an idea of sizes and the rest . Anybody have comments?

That plane look like what I was thinking about. Now, rearrange the packing of fuel, engine and transmission and get a healthy “residual thrust” from the turbo set up, build, test and go racing.
So it looks like what we need is a two seater torpedo with wings
 

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Starman

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Starman, if you are having the reduction box at the tail end it will be a bit crowded at that end with the tail structure, prop controls and tail wheel loads all in the one place --I presume you want to keep the shaft light by being high speed (?) --the distribution of weights is a bit of a concern then and I would group them closer together to reduce the polar moments and skin area . If you are 'unanimous' it could be because there was only one vote
.... How can a longer drive shaft be 'better' ?
The main reason I like the long shaft is because I will use it to great advantage using advanced torsion bar technology. The fact that it transmits much less torque and can be lighter is a part of it too, of course. If we want a prop rpm of around 2500 and the engine is running around 7500 rpm then that's a three to one reduction (for racers, cruisers would want more like 2 to one (5000rpm))

Torque tubes were mentioned in the twin fuselage thread as being already in use but those are not acceptable for what we need. Those torque tubes are the smallest lightest weakest they could possibly be, barely adequate, which is what the engineers are required to create, so it's all good, but barely adequate is also borderline inadequate.

Anyway, here in the real world, described best by Taoism, difficult problems are only really solved with softness. So the torsion bar works like this:

The bar should 'wind up' at least 90 degrees at full torque, and it needs to have the ring gear of a planetary gear set attached to act as a flywheel at the end away from the engine. This will ensure that the resonant frequencies of the drive system are very low and that the gearbox will see absolutely no power pulses. In order for the bar to twist 90 - 180 degrees at the diameter required for the high torque output of a supercharged Hemi it needs to be at least four feet long, and five or six is better.

Not sure what kind of tail you show either -is it cruciform or inverted V ? I find your main gear more than a little improbable structurally also --in any case the basic layout (ie Do P 247) is close to the best for low drag but the embodiment still leaves room for detail improvements (one day you might get all the serious contenders converging on this basic layout and varying in the details just like today's unlimited are all essentialy the same 'species' .

A two seater is the next step to allow conversion to this sort of very fast airplane and to give the 'highly overpowered' and clean aircraft experience to pilots of more normal aircraft or people after a thrill ride (and you better plan for airbrakes and very high flutter speeds just in case.
What I had intended on that drawing was a cruciform tail.

Here's a question for autoreply, does a two seat side by side sailplane have substantially more drag than a single seat.
 
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Starman

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I wonder if a supercharger is better than a turbo? With a supercharger you can point the exhaust stacks straight back and get a lot of thrust, and this is the kind of thrust that increases in effectiveness with higher speeds, isn't it?
 

Starman

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or like the LH-10, a two seater, it goes 230mph on 100hp, so it would go 460mph with 800hp, with fixed gear! With retracts and around 1500hp it should zip along fairly well.

maxresdefault.jpg
 

bl_dg

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Put those counter-rotating props on the front, a little forward sweep to the wing and you've got a Bugatti Model 100 racer. To make it a challenge for the masses, keep it to something a little more affordable, like the Formula V size racers.

Engine limited to 2.0L (could be VW or other auto conversion)
Take-off weight limited. (less than 500 lbs?, 600 lbs?)
Set a max stall speed.
Objective is max speed. ( score by [max speed]^2 / [stall speed] )

Let's go racing!
 

autoreply

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Here's a question for autoreply, does a two seat side by side sailplane have substantially more drag than a single seat.
Yes. Offset-seating helps a great deal. See the Binder EB29D how to cram two people in a minimal fuselage.

The LH10 never came even near it's promised performance.
 

Starman

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I refined the sketches a little bit and added component locations. span is 20 ft, wing area 24 ft, and assuming 3000lb then wing loading is 125 lb/ft. Turbo exhaust providing thrust, and triangular wing root cooling air intakes. Green is fuel and blue is cooling.
 

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Starman

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Engine limited to 2.0L (could be VW or other auto conversion)
Take-off weight limited. (less than 500 lbs?, 600 lbs?)
Set a max stall speed.
Objective is max speed. ( score by [max speed]^2 / [stall speed] )
Maybe you didn't read the first post, but this is about an 'unlimited' race plane that isn't limited to the 'unlimited' race plane terribly limiting rules.

Were talking monster 8 liter V8s here, so please take your Volkswagen elsewhere.
 

Starman

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I was thinking about what kind of rules would be helpful for this new supersport class of racer, and have some of the following suggestions.

Capacity for 2 - 6'3", 200lb - (2m, 90 kilo) - people carried comfortably.
1000 cu. in. (16 liter) max. piston power.
Internal fuel capacity for 1000 mile range at 400mph, but only carry enough for a race.
200 mile race on a large closed course that is designed for top speed rather than for who gets to the first pylon first.
Rollover protection

and then these:

A maximum landing roll out distance? (for passenger jet sized long runways)
Props only, no fans?
 
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Aircar

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The V max probe was actually quite dumpy in the fuselage and had it's maximum thickness quite far forward also --plus fixed gear and four tail intersections vs only two for an inverted V . The inverted V as landing gear also allows for a single monowheel and very simple retraction as well as a 'gravel catcher' . Maybe you could overlay the HP 18 pod and the V max to the same scale to see the difference , it was a miracle that the SCALED team could shoehorn the 1000hp Nissan engine and all accessories into the same diameter as the HP18 but they did it --that is the basis for massively upgrading the original "super BD5" concept from 1974 (the peak of the BD5 fad )

The very first tail pusher with a straight shaft was called "Aerotorpille" (maybe a bit wrong in the spelling ) literally 'air torpedo' --and none of that type has ever been successful since because of the drawbacks that centre around the CG height and gear length etc --the original Cirrus tail pusher (VK30) was abandoned and they returned to the traditional "Bleriot formula" nose engine and prop and aft tail . But for a one purpose design those drawbacks can be minimized as described and the rest can be lived with. Not having a main gear failure to extend is crucial --obviously , and being able to jettison the prop is also probably desirable ( I say 'probably' because the XB42 had a cordite charge to severe the prop and associated gearboxes but when it was used the aircraft pitched up violently so that bail out would probably have been impossible anyway just from the G (and you better hope you are wings level at the time...)

The real question is -would you be able to (permitted) sell rides in such a thing ? (how do ex warbird joyflights work if there is no certification? ) it is obviously far far less logistically compared to taking a fling to the edge of space and plummeting back with Mr Branson --and very very much cheaper .

I have looked at both side by side and tandem and 'other' configurations .... the side by side (or staggered) can be made as low a drag as in tandem and gives a much easier grouping of masses and the integration of two engines into one or two rear props (but that is not a push over either -the Learfan foundered on the two into one gearbox trick. ) The Douglas Cloudster (small civilian follow up to the XB42 had such a configuration and worked but the collapse of the civil small aircraft market killed it off -and the Lockheed Big Dipper by Thorp ,another tail pusher . The Planet Satellite ,BD7 Grinvals Orion and too many others have come and gone without revolutionizing anything so it is a minefield to enter this area despite how attractive it appears . But a faint heart never won a fair maiden...
 

Aircar

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I would not go for such a high aspect ratio for the racing mission and the flutter risk -- stiffness is a function of L cubed so there is a lot lost by spreading the area over too much span and you could save a lot more area in your fuselage and tail . Now for a two seater three view.......

Here are two links to the original flying torpedo http://www.freewebs.com/aeroscale/aerotorpille.htm

and http://flyingmachines.ru/Site2/Crafts/Craft28593.htm --there were contemporary German and Russian tail prop pushers also.
 

BoKu

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Anybody who wants to try this, I still have two HP-18 fuselage pods left. If you pick them up FOB Murphys CA, I'll let them go for $200 ea.
 

Aircar

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Oh the shame of it ! is $200 all that a year of a man's life is worth ?:gig: If only I was 7000 miles closer..... Now that you are on line Bob how about describing your "18 based go fast dreamship design? BTW do you have canopies for those pods ? (not sure if Dick went to mecaplex for production canopies either -do you know ? The HP24 forward fuse is another candidate and 'in production' --I am not sure if I would not want a couple of inches more headroom than the 18 in any case --just hitting turbulence at some ungodly speed could make contact with the canopy a risk . Thinking back on it -we used to have a Siai Marchetti SF 260 based at my old airport (Essendon) and in the next door hangar (I finished up repainting it and retrimming the interior when it was sold but never got to fly it -****.)

It returned once with about one foot of the fin sliced off after hitting a cable slung between the sides of a river valley and on another occasion with a big hole punched in the canopy --the passenger had hit the inside hard enough to knock him out and smash out a big chunk of plexiglas after they hit a wave rotor on fast descent .

Another time at the same field a Hughes 300 did an autorotate and hit hard enough to cut off the tailboom ,detach the fuel tanks and, again, punch two head holes in the canopy --( I had previously encased the tanks in Kevlar as a precautionary AD and they did not split) -- loss of control in flight from contacting the canopy might be a real consideration and need some provision for restraint (or a little pad like Helmut Treiber made when flutter testing the SB9)

The ban on light unlimited racers because of hitting wake turbulence from the biggies is probably well based --even leg restraints are a good idea --kicking off a canopy at 500 MPH or so would not be a good thing (the same issue occurs with recumbent tricycles where you can 'run over your own legs' if you hit a bump and they contact the ground after coming off the pedals -- I built 'stirrups' into my recumbent Bicycle (no crossbar to trap the feet but still dangerous) after a near enactment of this. I had my feet come off the pedals when inverted in a Steen Skybolt and had bruised shins for weeks afterwards from hitting the fuel tank (when a passenger) --- the G regime of a racer is probably way beyond what average pilots are accustomed to . Bob probably recalls Dick Schreder inadvertently pulling the canopy release on a borrowed ASW 17 when flying in the US nationals --that has happened lots of times but highlights the need for extra provisions to lock (and jettison when needed) a canopy --and for bird strike at higher speeds very thick plexi or lexan would be a good idea .
 
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autoreply

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I refined the sketches a little bit and added component locations. span is 20 ft, wing area 24 ft, and assuming 3000lb then wing loading is 125 lb/ft. Turbo exhaust providing thrust, and triangular wing root cooling air intakes. Green is fuel and blue is cooling.
Get span and area back to reasonable values. Even with a 100 sqft wing, it will only contribute to maybe 20% of your drag at zero G. It allows you to put a lot of systems in the wings (boil-off cooling). Single main gear is essential, since gear packaging becomes a biggie.

I'd have a good look at the Koenigsegg V8. Almost 1500 hp on stock bio-ethanol and a total running weight of around 400 lbs....

I don't see Aircar's issue with flutter. Even many sailplanes (AR<30) have flutter speeds of 400+ kts. I'd aim for the highest AR feasible, but something around 15 should be close to optimum. HM carbon fiber is pure magic...
 
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