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]

Originally Posted by 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 !

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]

Originally Posted by 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 ?

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]

Originally Posted by Bug_racer

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]

Originally Posted by gumbyk

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]

Originally Posted by Bug_racer

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]

Originally Posted by FLYBOYJ

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]

Originally Posted by FLYBOYJ

My plane is a jet

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

[Shortround6]

Originally Posted by Bug_racer

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]

Originally Posted by Shortround6

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]

Originally Posted by Bug_racer

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]

Originally Posted by Bug_racer

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]

Originally Posted by Colin1

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.

Originally Posted by Colin1

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.