Fast Cozy

[Joe Patterson]

Wow, it couldn't get any better. It is like being at a free-for-all boxing match, but the boxers use words and math.

 

rah rah rah................ding

 

 

You guys are brilliant. This is really great reading. Thanks for the passion.

 

Joseph Spirit

[dust]

I strongly disagree,

 

TURBO

TURBO

OXEGEN

OXEGEN

 

HE HE HE

 

also lets see what farings do on the gear, too many assumptions being made here

 

And, of course I am right and can only see the truth

 

enjoy the build

 

Mike

[No4]

I absolutely, utterly, completely, agree Dust. I'm now to the point where I wonder why so few have tried turbocharging.

As for the Oxygen mask, it is not such a simple leap of faith, going hypoxic is very dangerous indeed. A few business jets have experienced un detected de-pressurisations, and simply fly on until they run out of fuel. Who was that golfer? Was it Payne Stewart?

Plus I hear you can get the bends, and severely damage your eyesight up at those pressure levels.

The air might be -40'C, but being very thin cooling can be marginal, but I think the higher TAS may compensate with proper ducting.

 

However the reduction in drag is a major bonus, you sit high above all the terrain and cr@ppy weather and icing, and with a 100 knot tail wind you might see the GPS reading 400 mph.

 

I think if my calculations are correct, 300 mph True requires 200hp continuos at 25,000 feet with an Indicated airspeed of 200 mph in a Cozy MkIV, at standard weight.

 

[dust]

shhhhhhhhhhhhhh, i wasn't telling anyone thoooose numbers, let's wait.

 

oximeter - i will have one on the plane to insure proper ox levels

 

enjoy the build, keep this between us, lets make it a surprise

 

mike

[No4]

I was doing some calculations on my "Deep Blue" pocket calculator, with a little bit of assistance from my Pooleys CRP-1 nav computer.

 

I am interested in the 300 mph "barrier" for my Cozy.

 

Taking the CAFE figures, and with a bit of rounding, I tried to work out the drag of a Cozy similar to Mark Beduhn's.

 

The basic premise revolves around a 180 Lycoming, running at 75% power, achieves 200 knots. I know this is a bit high, but it is easier in the workings.

SO

Full power 180 hp = 135 kilowatts

75% power 135 hp = 100 kw

minus prop efficiency 75% = 75 thrust kw

 

75,000 watts divided by 100 metres per second (200 knots) gives us a drag figure of 750 Newtons, or roughly 165 lbs.

 

SO! To take a "standard" Cozy to 300 knots, at 25,000 (where 200 CAS = 300 TAS) it should require 750 * 150 = 112.5 Thrust Kw, which is 150 Brake kilowatts, which is 200 hp continous.

 

I think we agreed that retractable gear was worth 20 knots.

SO! 75,000 watts divided by 110 m/s (220 knots) gives us a new drag figure of 680 Newtons.

 

To now travel at 300 knots only requires 100 thrust kw, which is 135 brake kilowatts, or 180 hp continous, or a saving of around 4.5 litres per hour.

 

Or alternatively comparing it to a "standard" Cozy pumping 200 hp continous, 112.5 Thrust kilowatts now gives you a speed of 330 knots.

 

So by climbing to 25,000 feet, retractable gear is now worth 30 knots.

Any Good? phasers on stun, all hands to attack positions...

[N65TX]

Pardon the dumb question. How can you get all of that HP out of a turbo'd engine with a fixed prop? It seems if you set it for say 2400 rpm on deck, won't you overspeed up high? Or were you considering an MT or something like that.

 

Another thought, you could use high compression pistons, I know of at least a few Mooneys. Run rich and limit MP down low. Up high, a few extra inches.

 

Bob

[No4]

You are quite right Bob,

A fixed pitch prop wouldn't cut the mustard at 100 mph and 300 mph on a Lycoming.

For that matter a Turbo O-360 wouldn't be able maintain 200 hp either, not for long anyway.

The solution is a constant speed prop, or an engine that produces sufficient power low down, and can then rev to allow 300 mph.

The engine I plan to use, the VW V10 TDI, is rated at 230 hp at 2000 rpm, and 400 hp at 3750 rpm.

With the reduction drive it will produce 200 hp at 150 mph, and then the same, or more all the way to 320 mph. I don't plan to utilise more than 250 hp.

[marbleturtle]

... what does that V10 TDI weigh?

[No4]

She's way (weigh?) too heavy to make the Cozy a 4 seater, at least not without raising the gross weight by a several hundred pounds, and stretching the fuselage, which would certainly be possible, but beyond my capabilities this time around.

I can't find any figures yet, but the Thielert V8 4.0 weighs 283.5 kg prepared for service, so I'm planning on 300 kg.

( I can hear the groans from here!) But my whole project is to build a plane around an engine, rather than find the right engine for a plane.

I'm only making mine a two seater, with long range tanks, the cooling system, the ox bottles, and some luggage space to go where the rear seats were.

[rhofacker]

I absolutely, utterly, completely, agree Dust. I'm now to the point where I wonder why so few have tried turbocharging.

As for the Oxygen mask, it is not such a simple leap of faith, going hypoxic is very dangerous indeed. A few business jets have experienced un detected de-pressurisations, and simply fly on until they run out of fuel. Who was that golfer? Was it Payne Stewart?

Plus I hear you can get the bends, and severely damage your eyesight up at those pressure levels.

The air might be -40'C, but being very thin cooling can be marginal, but I think the higher TAS may compensate with proper ducting.

 

However the reduction in drag is a major bonus, you sit high above all the terrain and cr@ppy weather and icing, and with a 100 knot tail wind you might see the GPS reading 400 mph.

 

I think if my calculations are correct, 300 mph True requires 200hp continuos at 25,000 feet with an Indicated airspeed of 200 mph in a Cozy MkIV, at standard weight.

 

 

How about turbo charging, retracts, and O2?

[Nathan Gifford]

...

The only advantage I see the lancair has is Retractable Gear (RG) and a Constant Speed Prop (CS)....

Well the Lancair is a 2 seater, the Cozy is a 4. The Cozy has to have the aerodynamics to support 4 passengars. It would be interesting to see how much faster a Cozy would be with Infinity retracts.