poormansairforce
Well-Known Member
Sorry, I didn't realize you're talking about slow airplanes.
How to make a propeller driven aircraft go really fast ?
- Thread starter Speedboat100
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WonderousMountain
Well-Known Member
Quickness factor = Velocity /[√(Span^2+Length^2]
Red Baron used a Rolls-Royce Griffon engine. Later model Griffons came stock from the factory with counter-rotating propellers. CR props were installed for two reasons.
First, 6-bladed CR props could absorb more power than 5-bladed single-rotation propellers. Avro Shackelton maritime patrol airplanes may have had four Griffons and two rudders, but they retained CR props. Since South African Air Force Shakletons were the last in service, they provided Griffon engines and CR props to a few racers.
Secondly, Cr props minimized asymmetric thrust during take-off. Part of that asymmetric thrust is attributed by P-factor. P-factor is most noticeable at high angles of attack (wing relative to wind) when the downward prop blade takes a deeper "bite" of air, creating more thrust. This asymmetric thrust tries to turn the airplane, hence all the extra dorsal fins (P-51 D and later models), ventral fins (float planes) and taller fins (Cavalier Mustang conversions) to straighten take-offs.
macra 014,
That is a propeller of Paul Lipps design, he sent me photo's of much earlier designs he was trying to emulate and improve upon, basically he suggested that back pressure was exaggerated in modern designs and he was following elliptical lift distribution, whereby the tip had little influence and the bulk of the lifting was done closer to the root beyond back pressure.
I believe Jan Carlsson's latest software program followed this approach from talking to him, but he only used that for consultative work and he did mention he had read Jack Norris Book on propellers, which was of a similar vein.
I'm still trying to sort this all out myself and both men have passed on. I believe I'm slowly getting my hear around it, time will tell.
Hope that helps.
George
That is a propeller of Paul Lipps design, he sent me photo's of much earlier designs he was trying to emulate and improve upon, basically he suggested that back pressure was exaggerated in modern designs and he was following elliptical lift distribution, whereby the tip had little influence and the bulk of the lifting was done closer to the root beyond back pressure.
I believe Jan Carlsson's latest software program followed this approach from talking to him, but he only used that for consultative work and he did mention he had read Jack Norris Book on propellers, which was of a similar vein.
I'm still trying to sort this all out myself and both men have passed on. I believe I'm slowly getting my hear around it, time will tell.
Hope that helps.
George
Speedboat100
Well-Known Member
I am trying to figure out also how we fly after we run outa oil....fast is relative.
If you have a catapult and a rocket assisted take off climb you can fly electric aircraft nearly as fast the jets today...at very high altitude, but it is not practical.
I wonder if 300-400 km/h would do...as that is the speed we can reach easily with batteries and solar power..but the airliners cannot carry as many passengers as now with similar size..or can but cannot fly very far.
Andy_RR
Well-Known Member
You can fly at 80-100kts in a glider for very little oil.
poormansairforce
Well-Known Member
Hang out on a cloud and thumb a ride from the rest of us that realize we're not running out of oil anytime soon.
Speedboat100
Well-Known Member
Ok......is Continetal 0-200 out of manufacture ?
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Edit: I guess not: Continental 200 Series AvGas Engine
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FYI - Despite the hype of electric aircraft and the idea that they are our last best hope to continue flying they are not, though I thought the rocket /catapult idea quite clever.
If our collective political dumb asses could admit how little they know they could stop subsidizing corn production and tax breaks for the insanely wealthy and instead subsidize technologies for a (more) circular enegy economy. With comparatively little investment CDP (Catalyzed Depolymerization) could convert 80% of all solid waste (all of the long chain carbon chemistry created either from oil or plant based feed stocks) back into storable, high grade (low sulfer) diesel or Jet A. We could literally farm existing landfills for decades. (Note before anyone comments - the collection of methane from landfills accounts for about 8% of the total energy buried... Good to use but not to be too proud of overall..).
The other investment should be for truly efficient, e.g.high "specific" power,, diesel aircraft engines. (See Liquid Piston engine, Opposed Piston Diesel, etc..)
Finally, the best commercial application for electric aircraft is the hybrid electric/turbine designs. An incredibly efficient multi-hundred horsepower electric motor provides the additional peak horsepower for takeoff and landing. Energy is stored in (relatively) small batteries and super capacitors. Then the turbine can be designed for optimum cruise output. The overall efficiency gains are quite high as the off-peak burn rate of turbine engines is upwards of 30% greater than at peak output
Also, keep in mind that these are aircraft. Every pound added to the airframe is a pound that cannot be cargo. Liquid fuels carry 6-10 fold the specific energy (energy per lb.) of our best batteries. Pure Electric planes make little senses other than for specialty apps.
So let's all get real together and lobby for intelligent use of our resources.. Or buy catapults..
I have every confidence that we will never run out of gasoline, or a reasonable substitute. Technology provides as it has always provided, and will continue to do so in the future.
It may be that other energy storage systems (for that is all that gasoline is) may be developed that are just as good, and therefore it may happen that people may choose to not use gas. But that's different than "running out".
If gas is the preferred energy storage system, the market and tech will provide.
It may be that other energy storage systems (for that is all that gasoline is) may be developed that are just as good, and therefore it may happen that people may choose to not use gas. But that's different than "running out".
If gas is the preferred energy storage system, the market and tech will provide.
Dan Thomas
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The market might easily be overrun by political forces that will, without incontrovertible scientific proof for their actions, wreck it all.
Speedboat100
Well-Known Member
Yes we can fly electric ACs...if don't need to go anywhere..as their energy lasts only an hour max. Catapult + rocket assisted take off is then an other matter.
Dan Thomas
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Catapult takeoff is worse than useless. You MUST land back at the catapult, or else dismantle the airplane and truck it back. Little different than a glider winch. Is that what sport flying should be reduced to just so electric propulstion can be employed?
Speedboat100
Well-Known Member
No ....it is the last resort.
Speedboat100
Well-Known Member
I made a really lite model for the electric AC idea I have. I managed to get exactly the same weight ( scale bound relative ) as the intented original..it glides really fast with a good glideratio ( at least 15 ) maybe 20.
Sweep is 12 degs.
Next a radiocontrolled model of it with some mods.
henryk
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