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Thread: Unlimited racer concepts

  1. #1

    Default Unlimited racer concepts

    I was bored and sketched these together. They are all ideas I've discussed with people during race preparation for Reno this past year. Finally took some time to sketch them out. No real plans or movement on any of these ideas. They were just fun to draw and helped with waiting for next year.

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    Twin Tandem
    Unlimited racer concept

    Derived from the DO-335 and the constraint of not using 1930-40s era engines. Since this would be designed with composites it would come in underweight and it would have less horsepower than any other racer in the field. These weight and power shortfalls would be made up by adding another engine and bolstering the support structure. Once you decide on using a twin you have more drag unless you look to the Macchi 72, DO-335, or Cessna Skymaster.

    DO-335 seemed the cleanest in terms of aerodynamics. Started by sizing the powerplants with the Falconer V12 from the Thunder Mustangs as a placeholder. The goal would be to hit an empty weight of 4,501lb to hit the minimum weight limit with 1,200 horespower. This would give a power loading ratio of 0.25 and a wing loading of 35 lb/sqft.

    Goal was an average race speed of 400 mph to match the Pond Racer. While racing, the back seat would hold tanks for spray bar/ADI fluids. Otherwise the plane could travel the airshow circuit painted up as a fake DO-335 and sell airplane rides.

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    "TF's Revenge"
    An unlimited racer concept.
    A converted TF-51 with a turbo charged V12 (preferable an Aardema V12 with all the bugs worked out) with the turbos mounted where the front cockpit used to be. A new firewall gets put in front of the rear cockpit. Chin scoop feeds the turbos or gets replaced by an air intake similar to the BF-109/P-38. Extra space in the front cockpit goes toward spray bars/ADI.

    Other wi$hli$t item$ are new prop design and an optimized wing/airfoil

    The turbo charged TF concept would also apply to an airplane like the Yak-11, or any plane where their is a rear cockpit.

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    If the unlimited/warbird class allowed turboprops (I know, I know BLASPHEMY BURN HIM AT THE STAKE!! yadda yadda yadda) the main contenders would be the assortment of modern "warbirds" (trainers and light attack aircraft like the T-6, Super Tucano, PC-21, etc)
    The PC-21 has a max operating speed of 425 mph. While this would be enough to place in the silver, if the turbo props were to ever unseat the reciprocating engines significant modifications would need to be made.
    Easy one is pull the back seat. Between the ejection seat, avionics, and controls would save a lot of weight. This makes room for a new turtle deck which would also help with profile drag. The empty rear cockpit could hold any expendable fluids.
    As a trainer, the fuselage is very long and is probably overly stable for racing. This can be remedied by shortening the fuselage or reducing the tail area. The tail area requires less work. Dorsal and ventral fins removed. Add fillets at the wing roots and at the tail cone (like Race#5 "American Spirit") and improve the wing tips.
    By reducing weight and improving the aerodynamics the PC-21's wing and power loading could be improved making it more competitive as a racer.
    Additional work could be done to move the cockpit to the back while keeping the height down, remove the second ejection seat, unnecessary avionics, etc to improve the competitiveness. It'd be nice to convert it to a tail dragger and lose the weight of the nose wheel, but by then I think this would be a scratch built.

  2. #2
    Join Date
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    Herndon,Virginia
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    Default Re: Unlimited racer concepts

    nice ideas.keep em coming.

  3. #3

    Default Re: Unlimited racer concepts

    Read through this yesterday and that got the gears turning.
    https://www.nasa.gov/offices/ipp/cen...-Min-Drag.html

    There is still the problem with the power plant, so I'm going with the twin push-pull engine configuration. That presents problems with bailing out. You could keep the cockpit in line and simplify things and blow the aft propeller off in the event of a bailout, but that seems complicated as well. So the idea I drew up in VSP (because it looked weider) was to offset the cockpit and a vertical tail. The tail then doubles as a barrier between the pilot and the propeller during a bailout. CG is somewhere between the engines and the cockpit and the wings are asymmetrical to handle the offset. Fuel and other fluids are in line with the CG. Tricycle landing gear is a must with the flying wing.

    Target empty weight would be 4501 lbs. Using the OE600 gets you 1200HP which should be enough to break 400mph, not to mention the reduced drag from the flying wing design.

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    Also there is the Murdo Cameron P-51. This one seems the easiest, but there is a drawback I learned about after I went for a visit. The outer molds and tooling exist, however there are no drawings for the internals. Hinges, landing gear, controls, fuel lines, linkages, etc. Everything outside of the aerodynamics and structure needs to be designed. The owner is open to working with someone they have the time and money to finish it. Sadly I have neither of those things. Once the first kit was produced, that could open a small market for new kits and I think especially for new racers, since you don't have the dilemma of "cutting up history", but someone has to make the first one. This was the plan for the one prototype that was built and flown to oshkosh, but the owner was not happy with the builder (drilling holes in spars for cables and choosing an electric landing gear system that never worked), so the whole thing stalled.
    http://www.cameronaircraft.com/Team5...0Diagrams.html

    Anyways, less than three weeks until the NBC show!

  4. #4
    Join Date
    Jan 2004
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    Default Re: Unlimited racer concepts

    Some interesting ideas there.

    I've had the PC-21 idea, too, but using a Merlin, the aft cockpit and moving the wing forward.

    As for the Do335-like concept, I crunched numbers on that general idea several years and kept getting frustrated trying to reach a reasonable prop efficiency factor for the rear prop. That is, my research came up with a wide range of factors.

    Finally, your last concept - wild! Shouldn't the wing with the cockpit and fin be the larger of the two?

  5. #5

    Default Re: Unlimited racer concepts

    Quote Originally Posted by FlyKidChris View Post
    Some interesting ideas there.

    I've had the PC-21 idea, too, but using a Merlin, the aft cockpit and moving the wing forward.

    As for the Do335-like concept, I crunched numbers on that general idea several years and kept getting frustrated trying to reach a reasonable prop efficiency factor for the rear prop. That is, my research came up with a wide range of factors.

    Finally, your last concept - wild! Shouldn't the wing with the cockpit and fin be the larger of the two?
    The Merlin PC-21 would work too.Shoot at that point might as well put a griffon on there. The other military trainers might work too. Wiki says the T-6 II has a never exceed speed of 364mph but that could be worked around. The Sport gold racers are already way past their VNE.

    The rear prop, drive shaft, takeoff rotation, and the efficiency of the rear prop are all issues to deal with, but I don't see them being worse than the drag that will come with a conventional twin tractor design. When Rutan said working on the Pond Racer was the hardest project he had worked on

    The wing might be on the wrong side. In my head I was thinking bigger wing to offset the weight of the engines, but looking at it, the pilot and tail might cancel that all out. It looked cool though so I went with it while the creative juices were flowing. With a wing I actually think a twin tractor design wouldn't be bad. The engines will be in the thickest portion of the wing so that minimizes the profile drag and then you no longer have issues with bailing out. Still need a vertical tail in case of an engine out, but it would greatly simplify things.

  6. #6
    Join Date
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    Default Re: Unlimited racer concepts

    PC-21 will need a new airfoil to get anywhere near enough speed down low.

  7. #7

    Default Re: Unlimited racer concepts

    Quote Originally Posted by Race5 View Post
    PC-21 will need a new airfoil to get anywhere near enough speed down low.
    what is the PC-21 airfoil?

    Looking at stats on wiki they are similar to a P-51. P-51 has higher service ceiling and higher top speed, but they pretty close.

    I think unmodified the PC-21 and the other military trainers would be good class "fillers". Seeing how happy people were with the Texas Flying Legends planes racing as slow as they went, a stock PC-21 should be fast enough. Once you turn it into a full on gold-racer all bets are off. Fun discussion!

  8. #8
    Join Date
    Jan 2004
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    Default Re: Unlimited racer concepts

    Quote Originally Posted by CubersWrist View Post
    The rear prop, drive shaft, takeoff rotation, and the efficiency of the rear prop are all issues to deal with, but I don't see them being worse than the drag that will come with a conventional twin tractor design. When Rutan said working on the Pond Racer was the hardest project he had worked on

    The wing might be on the wrong side. In my head I was thinking bigger wing to offset the weight of the engines, but looking at it, the pilot and tail might cancel that all out. It looked cool though so I went with it while the creative juices were flowing. With a wing I actually think a twin tractor design wouldn't be bad. The engines will be in the thickest portion of the wing so that minimizes the profile drag and then you no longer have issues with bailing out. Still need a vertical tail in case of an engine out, but it would greatly simplify things.
    Nice reply.

    As for the prop efficiency factor of a aft mounted propellor, my research came up with a large range of factors and very little info at high indicated airspeed. Such an airplane would no doubt fly, but how fast? A twin fuselage configuration (think Twin Mustang F-82) was easier to predict.

    As for your asymetric flying wing concept, the engines are on the centerline, no? So they don't contribute to the asymetric spanwise weight load, but the cockpit and tail do. So as I see it (and I'm NOT an aero engineer), the cockpit side wing would need to be larger in order to generate more lift (than the opposite side) to offset the weight of the cockpit, pilot and fin.

  9. #9

    Default Re: Unlimited racer concepts

    For the tandem it would be helpful to find some reports or more data on the DO-335. It was the fastest plane for a long time, but that was two Daimler Benz V-12s. Twin Mustang concept was considered for the Pond Racer (as was the tandem engine) and they went with the twin booms and cockpit for safety. Now you have more drag which means you need bigger and more expensive engines to compensate. Bigger enginges lead bigger engine mount, bigger airplane, more drag etc. So there's always tradeoffs. The tandem has the benefit of two engines while adding the least amount of drag compared to other twin engine designs. Just got to get around drive shaft, bailout, and efficiency problems.

    Again I did zero math on the wing concept but the engines are actually meant to be off the centerline with the CG being equidistant between the engines and cockpit. I'm liking the idea of scaling the Ho-229 and replacing the jets with props. Should be proven aerodynamically and a decent starting point.

    Also for your enjoyment I have the design reports from the AIAA Reno Racer contest. Some aren't very practical and some don't even say what powerplant they will use, but some fun reading (for me) and gets the creative juices going.
    https://drive.google.com/drive/folde...wZ?usp=sharing

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