How would you win the Sport Racing class/why am I wrong?

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TFF

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If you watch the F1 takeoff, they definitely pay the price for fixed pitch. The Schneider Cup planes were fixed pitch and had long takeoff runs along with early Spits and Hurricanes and the like of that era.

As for sloppy, it’s only sloppy while they learn the ins and outs of the rules. Down the road, all slop will be rung out.
 

Toobuilder

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Agreed, I would also think that a big FP prop with a s**t-load of torque rolling the airplane over on takleoff would be a bigger risk than inadequate acceleration.
I think we may be forgetting that many of the WW-II fighters would do exactly that if mishandled. We are used to being able to cob the throttle at will on the current crop of sport aircraft, but a whole generation of pilots grew up trained otherwise.

Also remember that many of these same overpowered warbirds had their wings clipped, lightened up significantly, flaps deactivated/faired over AND the HP increased A WHOLE BUNCH to turn them into racers! These guys are not torque rolling over on takeoff.
 

delta

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This engine produces 600 newton meters of torque from 2000 rpm and would push this airframe around pretty good without a reduction, but really good with one.
sport1.JPGsport2.JPGsport3.JPGsport4.JPG
 

Magisterol

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I like this tread. And since is only academic (I don’t think I will ever be in a position to design or build something like this for myself), I would like to bring something in this discussion. A small airframe, matched to a huge HP engine, would be a hard if not impossible to fly due to the dynamic stability and prop torque issues. The dynamic stability is in a direct proportion to the square distance btwn CG and AC of the vertical and horizontal tail. Anybody flew as a pax in an A318? If you sit in the last few rows you could get sick from all the yaw oscillations in flight. Same thing with pitch; very easy to get PIO. The other thing is the prop torque. I talked to a guy that used to fly the Ag-Cat D/ST or D/SST that had the uptrim option for the PW engine to 1000hp in emergency. He had to use it once. The airplane got in a continuous turn at a shallow bank, because the controls at full deflection, weren’t enough to keep it straight and level at that power setting. Imagine something even smaller with twice the power.... I don’t think there are many , if any, pilots able to fly something like that. I know I won’t. Remember the problems XF-85 Goblin had?.....
 

lelievre12

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The Electromotive IMSA V6s were super reliable in race use with some 12 and 24 hour endurance race wins on top of almost total domination of GTP for a few years. Nothing wrong with the engines but as applied to the Pond Racer, cooling and oiling systems had issues. The oiling issues apparently leading to propeller control ones as well. The turbos were all wrong IMO. When I saw it run at Reno they were just screaming at idle and that just isn't right- indicating way too tight A/R on the turbine housing.. Who knows how the the turbine and compressor wheels were matched. The engine was VERY tightly cowled and the intercoolers were a tiny fraction of the volume used in the GTP cars.

Engine tech has certainly progressed since the early '90s. Lots of great choices available today, if you can build a reliable PSRU to go along with it- and that is probably a bigger challenge than the engine IMO.

One Sport Class entry has used a FP prop for 3 years now. Works fine and he was planning to use a FP on his LS powered racer too. Could be a disadvantage at the first pylon due to acceleration but that won't matter if you're 100 mph faster than the next guy...
+1

I think they ran the Pond Racer at high RPM on the ground to try and maintain ground cooling until they could get it to the ramp and hooked up to the aux fans. Tight cowls and a lot of heat.

Electramotive used the boosted Nissan VG-30 engines but in their 'standard' 650 HP race car form the aircraft was not beating 400 MPH so Electramotive boosted more. I wouldn't call this 'bleeding edge' as many Nissan street cars then were tuned to 1200HP plus reliably. However, by aircraft standards, the boost levels were pretty extreme.

The tightly cowled design meant that the oil scavenge tanks were smaller and the extra boost created additional blowby gases which blew the oil out of the engine and created aeration problems in the tanks.

Not that the Electramotive VG-30 engines were ever unreliable, they just became so when oil tanks were made smaller and cooling was reduced. Of course the same integration problems would hurt modern engines too which I guess is the main lesson from the Pond Racer. Even a 'modern' engine might fail if the same compromises are made in an aero conversion.
 

Toobuilder

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And it was exactly the extreme compromises in the engine/airframe integration that made the package "bleeding edge". Most people are aware that the core engine package in the IMSA car was bulletproof.

It seems like the new breed of really fast Reno racers (unlimited sport?) should be a little bit more like NASCAR and less like Forrmula One... Brute force the HP and then sneak up on the aero cleanup. The Pond tried to optimize aero at the expense of the powerplant.
 

rv6ejguy

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I like this tread. And since is only academic (I don’t think I will ever be in a position to design or build something like this for myself), I would like to bring something in this discussion. A small airframe, matched to a huge HP engine, would be a hard if not impossible to fly due to the dynamic stability and prop torque issues. .
The current crop of Sport class racers at the front have around 900 hp stuffed into a pretty small airframe, they fly fine. Strega/ Voodoo, 4000hp. Macchi M.C. 72, 151 square foot wing, 2850hp, likewise.
 

Magisterol

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The current crop of Sport class racers at the front have around 900 hp stuffed into a pretty small airframe, they fly fine. Strega/ Voodoo, 4000hp. Macchi M.C. 72, 151 square foot wing, 2850hp, likewise.
My bad. I think I have a different understanding of small. For me a small airplane is Pitts, BD-5, or One Design size. Less than 20ft span. For me an Extra 300 is a large airplane. Anything in between is medium... Sorry. Reading what you wrote, I retract my statement And I think you are right.
 

Toobuilder

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To your point, there are a few Pitts variants with enough power to hover. They are ANYTHING but "impossible" to control.

Sure, there are combinations of engines and powerplants that couldn't work from a controlability standpoint, but it would have to be something really radical to not function at speed on a race course (maybe a Cassutt with a P&W R-4360?)
 

Magisterol

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To your point, there are a few Pitts variants with enough power to hover. They are ANYTHING but "impossible" to control.

Sure, there are combinations of engines and powerplants that couldn't work from a controlability standpoint, but it would have to be something really radical to not function at speed on a race course (maybe a Cassutt with a P&W R-4360?)
I heard about S1-11B with 350+HP but from that, to 2000HP I think is a stretch. Unless I have the dimensions and more info to do basic numbers, I can’t say for sure. When I was in school, I was told to trust numbers. I have an engineering background.
 

Toobuilder

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There are limits to how much power you can stuff into an airplane and go faster. Any propeller driven airplane has a wall it simply can't get through so I don't see anyone trying to put BD-5 wings on a 4360 nacelle and set a record, but I can see a Legacy with 1500 HP not being too much of a problem to fly
 

Magisterol

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There are limits to how much power you can stuff into an airplane and go faster. Any propeller driven airplane has a wall it simply can't get through so I don't see anyone trying to put BD-5 wings on a 4360 nacelle and set a record, but I can see a Legacy with 1500 HP not being too much of a problem to fly
I understand. I guess the confusion came from what I understood about the term “small”
 

mcrae0104

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What “plastic surgery” do you have in mind?
Cut 20" out of the center of a Lancair or Glasair, then glue the two halves back together. I have some gap-filling CA glue somewhere around here, but sadly, I'm fresh out of Glasairs.

Since pylon racers spend slightly more than 50% of the time in banked turning flight.... it adds up.
Bingo! I have always thought that clipping wing span is a terrible way to cut drag for a racing plane, yet it's done all the time. I understand that Sea Furies actually turn the pylons slower with less span, despite the reduced wetted area. Some racers in the past have mated other wings to an existing fuselage (e.g. Miss Ashley or others); for all that effort, building a longer-span wing of the original area (or less) would prove more effective. Racing at higher load factors demands lower span loading (or whatever tricks you have in your bag to reduce induced drag), not simply reduced wing area. Perhaps now that we are past "peak warbird," this idea will occur to some enterprising designer/builder/racer.

Except the wing will be composite to achieve maximum laminar flow, likely will have a greater AR, and have better tips.
The GP-5 used my favorite composite material... :)
 

Tiger Tim

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I have always thought that clipping wing span is a terrible way to cut drag for a racing plane, yet it's done all the time.
I think it was Steve Wittman who it was said used to get out the saw and cut another six inches off each wing panel every time he lost. In a depression-era case it’s by far the easiest, fastest, and cheapest way to reduce wetted area. In the warbird racing world making a higher aspect ratio wing would likely mean thicker airfoil sections (in percent) as you reduce chord because the wheels still need a certain depth of wing to retract into. ‘Best’ is subject to a bunch of factors though I agree that barring all else a higher aspect ratio is the answer to pursue.
 

mm4440

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VB is correct that a centerline twin would be the best configuration for handling and min drag. Safety and pilot comfort sandwiched between a pair of high power racing engines may make wing mounted engines preferable, DO-335 and DH-103 are the models I would use. Boil off cooling, intercooling, ADI and spray water need to be considered. Is it going to be a race only plane that comes to Reno in a semi or will it have ferry capabilities? Lots of decisions. A pair of turbo 400-500 cu in V-8s are the most cost effective path to high power. Figure a million dollars to get started.
 

speedracer

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Cut 20" out of the center of a Lancair or Glasair, then glue the two halves back together. I have some gap-filling CA glue somewhere around here, but sadly, I'm fresh out of Glasairs.



Bingo! I have always thought that clipping wing span is a terrible way to cut drag for a racing plane, yet it's done all the time. I understand that Sea Furies actually turn the pylons slower with less span, despite the reduced wetted area. Some racers in the past have mated other wings to an existing fuselage (e.g. Miss Ashley or others); for all that effort, building a longer-span wing of the original area (or less) would prove more effective. Racing at higher load factors demands lower span loading (or whatever tricks you have in your bag to reduce induced drag), not simply reduced wing area. Perhaps now that we are past "peak warbird," this idea will occur to some enterprising designer/builder/racer.



The GP-5 used my favorite composite material... :)
In 2014 Lee Behel was killed in his Chevy V8 powered GP 5 when a wing came off. The rumor was that they found a crack in the wing spar and fixed it (unsuccessfully).
 
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