Which airframe

[Bug_racer]

Ive spent the last 10 minutes trying to work out where to put this thread ..

If you were to build an Axis Reno Racer what airframe would you choose and why .

Currently Id be going with a FW190d-9 or Ta152 design . Simply cause they were designed to go fast !

 

[FLYBOYJ]

Ive spent the last 10 minutes trying to work out where to put this thread ..

If you were to build an Axis Reno Racer what airframe would you choose and why .

Currently Id be going with a FW190d-9 or Ta152 design . Simply cause they were designed to go fast !

Neither.

Both were designed with 1940's technology and had many flaws in their stock state as they were designed to be a combat plane, not a racer. The Ta 152 would not have the low altitude performance necessary to run the course as with the Dora-9. They were fast but their best performance was at high altitude - Reno unlimiteds race 200' - 500' AGL. To use the basic airframe, either one would have to be radically altered (as current unlimited are) to be competitive. I'd start from scratch.

 

[Bug_racer]

hmmm

Im starting from scratch , just need a basic guideline plane to build it off . Main 2 would be either me109 or fw190 . Unless you can suggest a better plane used by the luftwaffe to redo ??? The Speed of the planes has more to do with the engine than the airframe . Airframe can be altered during the build to allow for low altitude high speed use . Engine will be built specifically for low altitude . So what would your suggestions be ?

 

[Crimea_River]

Do-335 if the pylons were further apart. Not sure the turning radius would work.

 

[FLYBOYJ]

hmmm

Im starting from scratch , just need a basic guideline plane to build it off . Main 2 would be either me109 or fw190 . Unless you can suggest a better plane used by the luftwaffe to redo ??? The Speed of the planes has more to do with the engine than the airframe . Airframe can be altered during the build to allow for low altitude high speed use . Engine will be built specifically for low altitude . So what would your suggestions be ?

I wouldn't start with any resemblance of a WW2 airframe - speed will be determined by aerodynamic efficiency, weight, and harmonizing the airframe to a good engine/ propeller combination. Although it would be "neat" to see a racer resembling a 190 or 109, in the end things like wing cross sections, spans and the placement of the cockpit would probably have to be altered. I'd design the airframe around the chosen engine and let aerodynamic engineers determine shapes and cockpit placement. Additionally I'd go with a composite structure. If it came out resembling a WW2 aircraft, great. The fastest recips to ever fly at Reno was Rare Bear and Strega, and both barely resemble their original design.

 

[gumbyk]

hmmm
The Speed of the planes has more to do with the engine than the airframe .

The limiting factor in these racers is not the power provided by the engine. At the speeds that they are operating at, the limitations are airframe dependant, i.e. compressibility drag, turning radius; and propeller limitations (a significant amount of the porpeller blade exceeding the local speed of sound).

IMO, the current speeds are about the best we will see from a piston powered, prop driven aircraft.

If it were me designing a racer, I'd do as flyboyj stated, and start from scratch. Its likely that anything you start off with will have so many modifications done to it that you will barely recognise it anyway.

 

[Bug_racer]

The limiting factor in these racers is not the power provided by the engine. At the speeds that they are operating at, the limitations are airframe dependant, i.e. compressibility drag, turning radius; and propeller limitations (a significant amount of the porpeller blade exceeding the local speed of sound).

IMO, the current speeds are about the best we will see from a piston powered, prop driven aircraft.

If it were me designing a racer, I'd do as flyboyj stated, and start from scratch. Its likely that anything you start off with will have so many modifications done to it that you will barely recognise it anyway.

The development of ww2 fighters was pretty intense . I didnt really hear about wings falling off in dives and high G loads . To develop an aircraft from scratch would be way too costly and would have limitations . I think Pond racer proved this !

I'll bet $100 they will keep getting faster . Someone else made a similar comment about drag cars years ago . Technology is always evolving and engines are becoming smaller and more powerful while using less fuel . Eventually speeds might only increase 1-2 mph per year as they come closer to the critical mach number but I really do see them increasing

 

[FLYBOYJ]

I'll bet $100 they will keep getting faster . Someone else made a similar comment about drag cars years ago . Technology is always evolving and engines are becoming smaller and more powerful while using less fuel . Eventually speeds might only increase 1-2 mph per year as they come closer to the critical mach number but I really do see them increasing

Drag racers aren't approaching the speed of sound, Reno Unlimiteds and Jets are just about there as we speak, you seem to not understand this. Any faster these aircraft are going to start hitting compressibility - airframe and at the prop tips which could potentially tear them apart. My plane is a jet and we run about 20 mph faster than the unlimiteds and we're starting to see signs of this problem. Additionally, RARA - the people who govern the races will limit speeds because of safety concerns and dealing with the FAA.

 

[Bug_racer]

Drag racers aren't approaching the speed of sound, Reno Unlimiteds and Jets are just about there as we speak, you seem to not understand this. Any faster these aircraft are going to start hitting compressibility - airframe and at the prop tips which could potentially tear them apart. My plane is a jet and we run about 20 mph faster than the unlimiteds and we're starting to see signs of this problem. Additionally, RARA - the people who govern the races will limit speeds because of safety concerns and dealing with the FAA.

Drag racers had their own limitations with chassis design in the 60's . The top fuelers went from front to rear dragsters and they continued on the progress . While there is only a handful of front engine dragsters running 5's , the rear engine dragsters are in the 4's with the record in the low 4's .
The demands of changes to the chassis will need to be made and someone will eventually come up with a solution to compressibilty . if it means making stronger heavier components then your gonna need more hp to propel the craft along . At the end of the day we have already broken the sound barrier so we can design an airframe to do it .

If they limit the speed thats good for me , cause a turbo engine when its on boost will accelerate quicker than one with a charger on it !

 

[Bug_racer]

My plane is a jet

You gonna race next year ?
Im seriously thinking of coming up from Aus to check it out

 

[Shortround6]

If they limit the speed thats good for me , cause a turbo engine when its on boost will accelerate quicker than one with a charger on it !

All depends on how much the plane actually slows down in the "corners"

two things to consider.

one, the engine might not change speed much at all, as speed bleeds off due to drag while "cornering" the prop may just change pitch to adjust rather than the engine rpm actually changing much.

two, with 400-600lbs of propeller acting as a fly wheel I am not sure the difference in rotating weight between a gear driven supercharger and a turbo is really going to be noticable.

 

[Bug_racer]

All depends on how much the plane actually slows down in the "corners"

two things to consider.

one, the engine might not change speed much at all, as speed bleeds off due to drag while "cornering" the prop may just change pitch to adjust rather than the engine rpm actually changing much.

two, with 400-600lbs of propeller acting as a fly wheel I am not sure the difference in rotating weight between a gear driven supercharger and a turbo is really going to be noticable.

A turbo will bleed off more boost and come on boost easier . A charger takes a little more time to come on boost . Turbos also generally can run much more boost . The advantage the supercharger has its always working , from idle to redline while a turbo has less of an efficiency range before it starts blowing hot air . If you keep within the efficiency range and just bleed off boost it will come on harder , quicker

 

[Colin1]

The demands of changes to the chassis will need to be made and someone will eventually come up with a solution to compressibilty.

if it means making stronger heavier components then you're gonna need more hp to propel the craft along. At the end of the day we have already broken the sound barrier so we can design an airframe to do it

They already did, didn't they? The swept wing? The problem with the swept wing is its low-speed characteristics and I imagine that what it gained on the straights, it's going to lose in the corners.

Stronger, heavier components won't help overcome wave drag, as for needing more hp well, yes but not to help carry these components, more to overcome the increasing effects of wave drag vs speed and you'll need considerable amounts of it; you'd have to wonder why none of the existing race teams haven't already thought of this - needing it and actually wringing it out of a recip already wrung out are two different things.

 

[FLYBOYJ]

You gonna race next year ?
Im seriously thinking of coming up from Aus to check it out

Oh yes - 2 years in a row we took 2nd so we're more than ready to move up.

 

[FLYBOYJ]

They already did, didn't they? The swept wing? The problem with the swept wing is its low-speed characteristics and I imagine that what it gained on the straights, it's going to lose in the corners.

Can't have swept wings in any of the classes from what I understand.

Stronger, heavier components won't help overcome wave drag, as for needing more hp well, yes but not to help carry these components, more to overcome the increasing effects of wave drag vs speed and you'll need considerable amounts of it; you'd have to wonder why none of the existing race teams haven't already thought of this - needing it and actually wringing it out of a recip already wrung out are two different things.

Mainly because of the use of stock WW2 aircraft airframes, again a justification to go with an airframe designed from the ground up for the unlimiteds.

At the speeds and altitudes the unlimited are running (if you consider the speed limitataion set by RARA) you're never going to be free of wave drag, they just have to find ways to mitigate it.

 

[Njaco]

Might this site help with some ideas.....

Luft '46 - WWII German aircraft projects

 

[Shortround6]

A turbo will bleed off more boost and come on boost easier . A charger takes a little more time to come on boost . Turbos also generally can run much more boost . The advantage the supercharger has its always working , from idle to redline while a turbo has less of an efficiency range before it starts blowing hot air . If you keep within the efficiency range and just bleed off boost it will come on harder , quicker

Except with an airplane (as opposed to a car) the engine is NOT coming off boost. The constant speed propeller adjusts it's pitch to the airspeed of the aircraft allowing the engine to maintain a constant RPM and a constant boost with a gear driven supercharger.

Most aircraft also used a suck through carburator, "Bleeding OFF" extra boost (fuel/air mixture) is not a good idea. THe evaporation of the fuel in the supercharger also acted as a intake charge cooling and was good for about a 25 degree C reduction in intake charge temperature. Something to consider when going to direct fuel injection.

Maybe FlyboyJ can correct me but I don't believe planes "brake" for turns/corners. The aerodynamic drag of turning slows the plane down so there is no off and on throttle or at least not much compared to a car.

The supercharges used on many of these planes seem to provide all the boost needed. infact I beleve some of the planes remove the 1st stage supercharger as unnessasary weight and power loss for low altitude flying.

 

[Colin1]

Can't have swept wings in any of the classes from what I understand.
Mainly because of the use of stock WW2 aircraft airframes, again a justification to go with an airframe designed from the ground up for the unlimiteds.

At the speeds and altitudes the unlimited are running (if you consider the speed limitataion set by RARA) you're never going to be free of wave drag, they just have to find ways to mitigate it.

All good points Joe
but my line (though admittedly not that clear) was that if any of it was feasible, the race teams would have adopted it years ago ie

- even if swept wings were allowed, surely you'd lose in the corners everything you'd made in the straights. Then you've got the weight of a swept wing over a straight wing.

- the engines are (from what I can gather) all wrung out for more power, if there was anything left to squeeze out of them, the race teams would have found it.

- that was more or less bang on the money for the point I was (trying to) make about wave drag

 

[Messy1]

Great info guys. Look forward to more posts. I'd love to go to Reno some year!

 

[FLYBOYJ]

- the engines are (from what I can gather) all wrung out for more power, if there was anything left to squeeze out of them, the race teams would have found it.

You nailed it - nothing aganist our young friend but the crews of the more "progressive" teams (Rare Bear, Strega, Dago Red, Voodoo, Czechmate, all I could think of right now) have done everything that could possibly be done to an aircraft engine to squeeze every bit of HP out of it, especailly inthe past 20 or so years where we have really seen the speeds of the unlimited take off. Some of these guys do have deep pockets so if it hasn't been done its probably becuase of rules or risk.

The guys working these engines aren't rookies - many of them are engineers with 40 or more years' experience in the industry. They come from an industry a lot more complicated than the automotive industry in terms of complexity, desigin limitatations and mandated regulations.

These guys are coming up on a brick wall where they will not be able to go much faster. Strega won Reno this year at 491 mph. The course has been flown at 507.105 mph by Skip Holm in 2003 and Rare Bear has flown 528.3 mph on a course to set a worlds speed record so there's some room for expansion. The jets will probably start seeing compressibility at 540 mph and I don't see the recips progressing beyong 530 mph. Also remember that race speeds are a bit less than qualifiying speeds due to less aircraft on the course. After this it will be pilot skill that will determine winners.