Which airframe

[Njaco]

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

Luft '46 - WWII German aircraft projects

[Shortround6]

Originally Posted by Bug_racer

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]

Originally Posted by FLYBOYJ

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]

Originally Posted by Colin1

- 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.

[Messy1]

FlyboyJ, are the unlimiteds using OE blocks and castings? Or have they moved to using aftermarket block and engine components?

[gumbyk]

Bugracer,
Here is what an attempt at a transonic prop-driven aircraft looks like:
XF-84H Thunderscreech - Wikipedia, the free encyclopedia

Note: one test pilot flew once and refused to fly it ever again, and another had 10 forced landings out of 11 flights. Not exactly the sort of aircraft that you want to be screaming around at 100ft in.

[FLYBOYJ]

Originally Posted by Messy1

FlyboyJ, are the unlimiteds using OE blocks and castings? Or have they moved to using aftermarket block and engine components?

I believe the Mustangs may be using some AM stuff. Rare Bear had to use basically a stock engine this year!

[Bug_racer]

Good posts and lost of good info

The XF-84 project is an interesting one . Im curious why the propellor blades had to revolve so fast on the ground ? I thought you could lower the rpm of the engine to slow them down ?

This looks like a 50's project . we have a lot more better materials available to us now compared to then . Titanium for example , surely that can be used to replace steel in some sections of the aircraft ???

Now I keep hearing these planes being cutting edge . All the technolgy Im talking about has only been out in the last 10 years or so . Stand alone engine management was really only developed in the mid 90s , only in the last 3-4 years has it become as complex as what it is today . Sometimes you can swap computers over but most of the time you need a whole new harness . FSI first was used on a race car in the Audi R8 in 2000 . It was later fitted to VW/Audi cars in 2004 onwards . Oil squirters on pistons AFAIK came on the 1.8T first back in 1995 .

Now can you honestly tell me that any of the reno racers has followed motorsport and seen what they are doing to improve it on their own aircraft OR they are only improving whats on the aircraft and not doing any drastic changes ????

I believe cars are far more advanced than planes these days . In 5 years technology advances so fast in cars that turbo cars from 10 years ago are equal in power to N/A cars today of the same cubic capacity . Diesel technology is now so well established that it wouldnt suprise me if you started seeing people putting diesel engines in planes . If you still think planes are so advanced name 1 thing thats been revolutionary in aircraft engine design in the last 5 years !

[Bug_racer]

The record for the fastest single-engined piston plane is held by a modified Grumman F8F Bearcat, the Rare Bear, with a speed of 850.24 km/h (528.33 mph) on 21 August 1989 at Las Vegas, Nevada, United States of America.[8][9]

The record was set 20 years ago !

[Colin1]

Originally Posted by Bug_racer

1. I believe cars are far more advanced than planes these days.

2. Diesel technology is now so well established that it wouldnt surprise me if you started seeing people putting diesel engines in planes.

3. If you still think planes are so advanced name one thing thats been revolutionary in aircraft engine design in the last five years!

1. Modern-day automotive recips may be more technically advanced than their WWII counterparts but I can't see the comparison with anything else - who but Reno racers use piston engines these days? There is no commercial or market pressure to make them more advanced.

2. They already did that too - the Ju86P

3. ADVENT (Adaptive Versatile Engine Technology)?

The ADVENT of a Better Jet Engine?

[Shortround6]

peaple were putting diesels in airplanes in the early thirties.

You aren't listening to the physics.

IF the airplane engine doesn't vary in rpm by more than a couple of hundred rpm in a lap (if that) why worry about coming on boost? the engine never went off boost.

Changing parts of the F-84 to titianium won't change it's biggest flaw. The noise from it's supersonic propeller made peaple in the area (ground crew) physically sick, as in nauseous.

all the fancy engine management computers in the world aren't going to change the way sound waves work or change airflow behavior at transonic speeds.

Another limiting factor is the propeller, Think of it,in part, as the tires on a car. A cartain size propeller(tire) can only transmit so much force (power) then you need a bigger (wider) prop/tire. Except that the bigger prop/tire weighs more and planes have CG issues that cars don't.

Could you build a modern engine that puts out much more power than an old aircraft engine per cubic in?
Certainly and by a large margin.

But aircraft are not limited to displacement (at least in the unlimited class) And power per pound is more important to an aircraft designer and while by this measure modern engines may be much better the difference might not be quite so marked. If the modern engine is using high rpm to get it's power it is going to need a larger, heavier reduction gear to lower the rpm to speed that the propeller can use.

Modern engine management systems may owe a tip of the hat to the engine anyalisis sytem employed on the P&W R-4350 engines in the B-36.

[FLYBOYJ]

Originally Posted by Bug_racer

Good posts and lost of good info

The XF-84 project is an interesting one . Im curious why the propellor blades had to revolve so fast on the ground ? I thought you could lower the rpm of the engine to slow them down ?

The rpm ran constatnt and the prop pitch was changed as needed, as if it was a giant transmission

Originally Posted by Bug_racer

This looks like a 50's project . we have a lot more better materials available to us now compared to then . Titanium for example , surely that can be used to replace steel in some sections of the aircraft ???

Actually there was magnesium used in that aircraft. The basic F-84 design was a second generation jet, all you're looking at was a turbo prop hung on a swept-wing post WW2 design.

Originally Posted by Bug_racer

Now I keep hearing these planes being cutting edge . All the technolgy Im talking about has only been out in the last 10 years or so . Stand alone engine management was really only developed in the mid 90s , only in the last 3-4 years has it become as complex as what it is today . Sometimes you can swap computers over but most of the time you need a whole new harness . FSI first was used on a race car in the Audi R8 in 2000 . It was later fitted to VW/Audi cars in 2004 onwards . Oil squirters on pistons AFAIK came on the 1.8T first back in 1995 .

You have to be able to apply that technology to aviation products and sometimes that's problematic.

Originally Posted by Bug_racer

Now can you honestly tell me that any of the reno racers has followed motorsport and seen what they are doing to improve it on their own aircraft OR they are only improving whats on the aircraft and not doing any drastic changes ????

I could tell you that some of the team engineers know intimately what’s going on in motorsports (some of the are even participating and employed in the design of some components). Again its a matter of being able to apply that technology to the airframes and engines available and in the end to be able to conform to RARA rules AND be able to gain an Airworthiness Certificate from the FAA. Although the aircraft are in "experimental" category, the Feds still have to approve the aircraft for flight, especially if it’s designed from the ground up.

Originally Posted by Bug_racer

I believe cars are far more advanced than planes these days .

It depends what aspect of aviation you're talking about. In terms of recip engines - yes. In terms of general aviation systems including navigation, GPS, terrain and traffic warning - miles ahead of the automotive industry. Go into corporate, airliners or military aircraft and it's like comparing a sun dial to the atomic clock.

Originally Posted by Bug_racer

In 5 years technology advances so fast in cars that turbo cars from 10 years ago are equal in power to N/A cars today of the same cubic capacity . Diesel technology is now so well established that it wouldnt suprise me if you started seeing people putting diesel engines in planes .

They already have..


Diamond Aircraft :: New engine for General Aviation

Originally Posted by Bug_racer

If you still think planes are so advanced name 1 thing thats been revolutionary in aircraft engine design in the last 5 years !

Easy;

Towards First Flight - Lockheed Propulsion System

The technology for this been around for a few years, it just got recently perfected...

Scramjet - Wikipedia, the free encyclopedia

There's plently more and this is what we know about.

[Messy1]

The problem with comparing car vs. Plane tech and new designs and breakthroughs is that by the time a "new" plane is released, it has been around and developed in secrecy, sometimes 10-15 years before it the public even knows or hears about it. Cars are not too involved or have to worry about national security. For instance, the B-2 program was started on Oct. 20TH, 1981, and was first released for public viewing on Nov. 22nd, 1988.
F-22 started in the the mid 80's, and the aircraft was officially unveiled in 1997.

Cars programs are generally not cloaked in such secrecy.

[Bug_racer]

Originally Posted by Messy1

The problem with comparing car vs. Plane tech and new designs and breakthroughs is that by the time a "new" plane is released, it has been around and developed in secrecy, sometimes 10-15 years before it the public even knows or hears about it. Cars are not too involved or have to worry about national security. For instance, the B-2 program was started on Oct. 20TH, 1981, and was first released for public viewing on Nov. 22nd, 1988.
F-22 started in the the mid 80's, and the aircraft was officially unveiled in 1997.

Cars programs are generally not cloaked in such secrecy.

Car technology is a lot easier to copy , and its usually companies like Bosch etc that have the patents with a certain car brand for X years before it gets released to other car companies . Expect to see every car manufacturer start moving to Direct injection soon !

Ijust got the full schematics of the fw190 . Just by having a quick look through there already is some changes which Id make ! I guess I need to speak to anairframe developer before I go ahead and make any changes to the design


I do have one question. Contra-rotating propellers . What are the advantages/disadvantages with these over Multi-bladed propellors ?