Scat 1- stators
ralph_...@my-deja.com
it seems to me, depends on 1. how much turbulance/back pressure exists
in the twisted air behind the fan 2. how well the stators are made.
That is to say, with a low power density duct,adding some crudely
shaped , high drag stators is not a good thing to do. But with a high
power density duct, adding a meticulously done cone and stators is
indeed free thrust. Most small hovercraft I have seen are somewhere in
between. Of the 110 racecraft in England this summer,
all but a few had stators. Even in applications where they add little
thrust, they can have important uses like making a craft comply with
fan guarding/ duct strength rules as well as torque cancelling in small
hi power craft. In other words, if something needs to be right behind
the fan anyway, it definitely should be shaped like a stator.
Sent via Deja.com http://www.deja.com/
Before you buy.
Hoverjunky
>From: ralph_...@my-deja.com
>Date: 10/11/00 9:25 PM !!!First Boot!!!
>Message-id: <8s2ls3$vub$1...@nnrp1.deja.com>
When I spoke to William Flett of Hovercraft Concepts he said that Scat used the
stator and cone assembly primarily for looks, not performance, call him and ask
him, he used to work for scat.
ChrisM1111
What is a Stator?
Free thrust, hhmm, physics has taught me there is no free lunch, still, as this
scat has small engine,,,,,
thanks chris
For free plans and info on solar oven's water and purifiers, that actually
work, see<http://www.accessone.com/~sbcn/index.htm>
===========================================================
Sufficiently advance technology is indistinguishable from magic..
Ken Roberts
>Sorry, newbie question, as I now have a scat in need of lots of tlc, Stator?
>What is a Stator?
a stator is the thing behind the fan, which straightens air out so it all points
backwards instead of swirling around.
>Free thrust, hhmm, physics has taught me there is no free lunch, still, as this
>scat has small engine,,,,,
it's not free. you're being less wasteful of power. think of it like a
turbocharger, even though they're different things: the turbocharger increases
exhaust back-pressure on the engine, but at the same time increases intake
pressure and the performance gain is higher than the performance degradation.
the stator is similar in that respect. it takes power from the moving air, but
the result of a good stator is that more of the air which is moving is moving
backwards, if that makes sense.
the air leaving the fan is moving backwards and sideways and up and down. lots
of energy, moving in a sideways-tornado fashion. that's probably not quite
accurate, but it's the best i'm gonna do here. the idea is to turn the
sideways-traveling air so that it all points in the desired direction.
also, there have been comments recently about the effectiveness of scat stators.
you may be better off without them, or replacing them with something you made.
Ray Toews
wrote:
I can't see the effectivness of stators on a hovercraft, on an earlier
post some weeks ago I commented on stators but I now realise I was in
error, I have never seen a Scat so I was unfamiliar with what you
called stators, I thought they were Inlet Guide Vanes, IGV's of the
type used in jet engines, they are there to realign incoming air flow
to meet the blade/prop at the appropriate angle for best efficiency,
that is why some turbines use variable IGV's for different RPM's.
Jet engines never use air flow straighteners behind the engine, it
would be a waste of energy to straighten out the flow, who cares if it
is swirling, as long as it is flowing rearward at max velocity, if you
tried to straighten it out it would put a rolling moment into the
vanes which would be transfered to the craft.
Ray Toews
Carol Alm
Jet engines actually do use stators to straighten the flow just behind
the fan section. Look at the back of any Pratt & Whitney type engine,
such as the JT9D-XXX used on Boeing 747, Douglas DC-10 or the PWA-2037
engine used on the Boeing 757, and you will see an exit guide vane
section in the fan case. The fan on these engines provide about 75%
or more of the thrust produced by these engines put out.
Thanks,
Dennis Alm
ron fishlock
Ray, I never like saying someone is wrong, but in the case of your
comparison of jet engines and the use of straighteners, you may be just
that!
First my definition of a jet engine is that used either as a pure jet
engine or that coupled to a gear box and driving a propeller, sometimes
known as a turbojet.
Jet engines in principle, as most of us know, create a reactive thrust
by the through put of high volumes of air at high dynamic pressures. To
achieve this, most modern jet engines draw air into the engine and
compress it by the use of a series of compression fan blades. They are
all connected to a common shaft. This pressurized air is then mixed in
a combustion chamber with fuel and ignited. This expanding air then
passes aft though another set of fan blades with reverse pitch, that are
also connected to the common shaft. This creates the engines continuous
cycle.
Before the first set of compression blades, (not talking about high
bypass jet engines used on large jet aircraft) there are a set of fixed
blades that are known as prerotators. These take the straight incoming
air and turn it to face the leading edge of the first set of compression
blades.
Behind the first blades are a another set of fixed stators that take the
swirling air and turn it to face the second set of compression blades.
This continues through a series of blades, while at the same time the
cross sectional area that the air passes through reduces in size,
thereby increasing the air pressure.
After the combusted air passes through the last set of fan blades, it is
straightened by one last set of straighteners.
At many museums or aviation displays, you can sometimes see real or
model jet engines, cut open, with all the fan blades and stators clearly
visible.
Now some people doubt the validity of straighteners because they don't
see them on propeller driven aircraft. Except for a few rear engine
aircraft, most props are at the front. The aerodynamic controls, i.e.,
rudders and elevators on most aircraft are at the tail end and due to
aircraft speeds, do not rely on the prop wash over them for control
forces.
In the case of slow moving hovercraft, rear propeller or fan driven
craft have the rudders immediately behind the thrust unit, in order to
derive sufficient control forces.
Think of a set of rudders directly behind a rear propeller/fan driven
hovercraft. Assume a counter clockwise direction of rotation as viewed
from the stern. Because of the swirl from the propeller/fan, actuating
the rudders for a turn to port will see good flow over the top section
of the rudders. However, the lower half of the rudders will be
presenting a surface, more likely closer to stall. Now although
aerodynamically this might be considered poor, this system works well
enough. This arrangement has been lived with by most hovercraft
designers, mainly because of its simplicity.
Back in the 1970's in Britain, there were several small hovercraft that
had split rudders to improve the flow across the top and bottom.
Although some improvement in turning was realized, it did not seem worth
the added expense of rudder construction.
Now there is a special case for integrated lift/thrust craft like the
Scat. With a lift splitter occupying the lower 1/3 of the fan duct,
the remaining air for thrust has a definite bias in the direction of
port. Without some form of fan flow straighteners, the craft will turn
more readily to port than starboard. Radial flow straighteners, if
designed correctly, are the best way of equalizing the flow, but are not
the only way. (Note, incorrectly designed straighteners can in fact,
reduce efficiency)
A single vertical divider, suitably located, can do a reasonably
effective job. This is what we use on the Canair 300 & 500/2.
Sorry for the long winded explanation, I've been holding off hoping that
someone else would jump in. Hope this provides some insight.
TO ALL hovercraft builders, experiment, to improve the art/engineering
of hovercraft design, before the anti-gravity machines take over !!!
For those building for the first time, and using someone else's
successful plans, stick to them might be wise choice to begin with.
Once your craft is up and running, then have some fun experimenting.
Ron Fishlock
For ACV Designs http://www.canairhover.com
NWCedarDecks
Do you have the 277 rotax in you craft?
If made right the stators might in prove the trust 5% maybe more.
ED
Ray Toews
wrote:
>Re Scat 1 - stators, reply from Ray Toews
>
>Ray, I never like saying someone is wrong, but in the case of your
>comparison of jet engines and the use of straighteners, you may be just
>that!
>
.
>First my definition of a jet engine is that used either as a pure jet
>engine or that coupled to a gear box and driving a propeller, sometimes
>known as a turbojet.
>
>Jet engines in principle, as most of us know, create a reactive thrust
>by the through put of high volumes of air at high dynamic pressures. To
>achieve this, most modern jet engines draw air into the engine and
>compress it by the use of a series of compression fan blades. They are
>all connected to a common shaft. This pressurized air is then mixed in
>a combustion chamber with fuel and ignited. This expanding air then
>passes aft though another set of fan blades with reverse pitch, that are
>also connected to the common shaft. This creates the engines continuous
>cycle.
>
I am aware of the operation of a gas turbine engine, admittedly my
experience is now twenty years old, but interest has kept me
reasonably up to date on engine development and I see no radical
change in the fluid dynamics, mostly in the internal temperatures, the
amounts of bypass new engines use and engine control improvements
>Before the first set of compression blades, (not talking about high
>bypass jet engines used on large jet aircraft) there are a set of fixed
>blades that are known as prerotators. These take the straight incoming
>air and turn it to face the leading edge of the first set of compression
>blades.
>
All sets of stators in a gas turbine engine are there for the benefit
of the following set of rotors, ie, they are in front of the set of
rotors they affect, if they straighten the flow it is for the benefit
of the following blades so the air hits at the appropriate angle to
create the best airflow, that is why some older engines used variable
angle IGV's (eg. J79 used in the F104, Phantom, Kfir etc.) to improve
efficiency at different RPM's. I have not worked on a lot of jet
engines recently but at every airshow I go to I look up the tailpipe
as part of my quest to check the state of development and I have yet
to see a set of straigteners, (stator blades) at the back of the
engine, unless you consider the vanes holding the afterburner
turbulators, straighteners.
I have not had the opportunity to look up the butt of an airliner
engine, to see if there are a set of stators behind the fan, they
never let me onto the ramp to check them out,,,,
On a post some time ago I asked the question if there were stator
blades between the stages of a high bypass fan but did not recieve a
reply. I would appreciate a picture of the straighteners, (stators)
shown from the rear of the engine.
>Behind the first blades are a another set of fixed stators that take the
>swirling air and turn it to face the second set of compression blades.
>This continues through a series of blades, while at the same time the
>cross sectional area that the air passes through reduces in size,
>thereby increasing the air pressure.
>
>After the combusted air passes through the last set of fan blades, it is
>straightened by one last set of straighteners.
>
>At many museums or aviation displays, you can sometimes see real or
>model jet engines, cut open, with all the fan blades and stators clearly
>visible.
>
>Now some people doubt the validity of straighteners because they don't
>see them on propeller driven aircraft. Except for a few rear engine
>aircraft, most props are at the front. The aerodynamic controls, i.e.,
>rudders and elevators on most aircraft are at the tail end and due to
>aircraft speeds, do not rely on the prop wash over them for control
>forces.
>
>In the case of slow moving hovercraft, rear propeller or fan driven
>craft have the rudders immediately behind the thrust unit, in order to
>derive sufficient control forces.
>
Rudders and control surfaces on the rear of aircraft are not used as
straighteners, in fact create quite a lot of extra stress and design
problems to counteract P factor of the swirling air, I assume this is
the reason why a designer like Burt Rutan would move the rudders out
to the wingtips where their efficiency is improved by running in
"clean" air. There is nothing behind the prop of this supper efficient
design, which among other things allows a guy like Klaus Savier to go
over 200mph on 100hp. That is also a good reason to move the elevator
(canard) out to the front of the airplane and make it a lifting
surface instead of forcing the tail to fly downward as in conventional
aircraft.
Okay if this tail first design is so darn efficient why doesn't Boeing
build their airliners that way,,,,, could it be because we wouldn't
fly in them, look at the reaction the Beech Starship has
recieved,,,,,, but I digress.
>Think of a set of rudders directly behind a rear propeller/fan driven
>hovercraft. Assume a counter clockwise direction of rotation as viewed
>from the stern. Because of the swirl from the propeller/fan, actuating
>the rudders for a turn to port will see good flow over the top section
>of the rudders. However, the lower half of the rudders will be
>presenting a surface, more likely closer to stall. Now although
>aerodynamically this might be considered poor, this system works well
>enough. This arrangement has been lived with by most hovercraft
>designers, mainly because of its simplicity.
>Back in the 1970's in Britain, there were several small hovercraft that
>had split rudders to improve the flow across the top and bottom.
>Although some improvement in turning was realized, it did not seem worth
>the added expense of rudder construction.
Are you talking about articulating rudders, presenting more of an
airfoil shape to the slipstream rather than a flat or symetrical plank
as most use?
>
>Now there is a special case for integrated lift/thrust craft like the
>Scat. With a lift splitter occupying the lower 1/3 of the fan duct,
>the remaining air for thrust has a definite bias in the direction of
>port. Without some form of fan flow straighteners, the craft will turn
>more readily to port than starboard. Radial flow straighteners, if
>designed correctly, are the best way of equalizing the flow, but are not
>the only way. (Note, incorrectly designed straighteners can in fact,
>reduce efficiency)
This is what I was talking about in an earlier post, the rudders
working as straighteners were responsible for a turning moment in the
craft which is a design problem, one which Barry choose to compensate
for on the SEV by offsetting the thrust line by one degree, something
I choose not to do, cynic and experimenter that I am, I am now paying
the price by having a machine which turns better one way than the
other (to be corrected this winter). A straightener in the horizontal
plane would have the same effect but in more of a rolling moment and
would have to be compensated by ,,,,,,what?
How do the Wendt's compensate on their WIG for this rolling turning
moment?????
I realize I am arguing with some very qualified people here and it is
a bit intimidating, but with age has come more confidence in knowing
what I know,,,I think.
I argue my point from my perception of everything I have seen and
read, but I was wrong,,,,,,once. Not always rite, but seldom wrong.
Ray Toews
Ken Roberts
>>bypass jet engines used on large jet aircraft) there are a set of fixed
>>blades that are known as prerotators. These take the straight incoming
>>air and turn it to face the leading edge of the first set of compression
>>blades.
>>
>All sets of stators in a gas turbine engine are there for the benefit
>of the following set of rotors, ie, they are in front of the set of
>rotors they affect, if they straighten the flow it is for the benefit
>of the following blades so the air hits at the appropriate angle to
>create the best airflow, that is why some older engines used variable
>angle IGV's (eg. J79 used in the F104, Phantom, Kfir etc.) to improve
>efficiency at different RPM's. I have not worked on a lot of jet
>engines recently but at every airshow I go to I look up the tailpipe
>as part of my quest to check the state of development and I have yet
>to see a set of straigteners, (stator blades) at the back of the
>engine, unless you consider the vanes holding the afterburner
>turbulators, straighteners.
i can't say whether jets use stators or not. i've had absolutely no experience
with the inside of a jet engine. i can supply a few points of possible
differences between jets and hovercrafts though.
my impression of a jet engine is that it has a fairly long duct after the final
turbine. we're talking long in terms of the turbine diameter. a hovercraft's
entire duct length is typically around 1/3 the diameter of the prop. at least,
my uh-12r is this way. i might suggest that a jet may not need any sort of
stator behind the final turbine, simply because the duct is long enough to do
the job.
also, taking a wild guess at some numbers, suppose your hovercraft's thrust air
comes out with a mean deflection of 25 degrees from the axis of rotation.
you'll have a significant power loss since that deflection represents energy
spent making air go sideways. what's worse, there's a place on the other side
of the prop where the same amount of energy is being spent making more air go
the opposite direction, which means you've spent that energy making heat, or
some such nonsense.
Ray Toews
wrote:
>>>Before the first set of compression blades, (not talking about high
You are rite Ken, there is quite a bit of difference between a jet
engine and a hovercraft fan but the similarity is the blades on a jet
engine are airfoils running in a fluid the same as a prop,,,,,,,,,,
and thrust reaction is the same, by definition fast moving air hitting
slow moving air causing reaction,,,, and noise.
The air coming out the back of a jet engine is swirling very
fast,(check out the contrails) just as the air coming off a prop is
swirling,, my contention is, if we are all talking about the same
thing, is that it is a waste of energy and possibly even a design
problem to try to straighten it out.
I agree with your statment that air/thrust is coming out at an angle
to the direction of travel is a waste of energy but I would like to be
convinced that trying to straighten it out is less of a waste.
The length of the duct in a jet probably has an effect on the swirling
action and increases the thrust but is the increase enough to offset
the drag loss inside the tail pipe. Do aircraft designers take the
length of the duct into account when designing the airplane or is it
simply a weight and balance question of where to place the engine?
I don't recall but I don't remember ever seeing the columns holding
the afterburner turbulators in place being any thing more than
straight symetrical airfoils, if it were an advantage to stop by
reversing the direction of swirl I would think the designers would
build in an airfoil to accomplish this.
Most engines with afterburner, reheat to the British, use variable
diameter nozzles to increase thrust and to control Exhaust Gas
Temperature.
keep up the comments, I like to be proven wrong, I learn from that.
Ray Toews
SEVTEC
>From: hyd...@telusplanet.net (Ray Toews)
>Date: 10/29/2000 11:58 AM Pacific Standard Time
>Message-id: <39fc789d....@news.edmonton.telusplanet.net>
At the risk of being accused ot too much "engineereeze" I will comment on flow
straighteners, and how they relate to jet engines and hovercraft fans.
Jet engines frequently use multiple stage axial compressor stages for
increasing pressure to the burners. They operate at a pressure ratio of the
order of 1.15, that is, they pressurize the air by 14.7*1.15 - 14.7, or 2.2
psi, or 317 psf! This is well beyond the largest hovercraft, and the air
compressibility must be considered in the design of these compressor stages.
The total pressure ratio of the compressor may be the order of 1.15^n, where n
is the number of stages, so for a ten stage compressor, pressure ratio could be
4, or 4 * 14.7*144=8467psf. The stators are to recover velocity energy from
the stage, and redirect the flow into the next stage for best efficiency.
(Needless to say, there is a whole lot of development involved in developing
multiple stage compressors.)
The hovercraft fan is a different animal, where compressible flow is just being
approached (in racing craft), and if no stators or exit diffusers are involved
the flow must have some swirl component. This swirl is generated by the torque
of the fan producing angular momentum of the mass flow going through the fan.
Calculation is complicated as variations occur relative to the radial position
of the flow and operation off the design point.
If the exit angle is around 25 degrees, the loss in thrust will ideally be
roughly v cos25 deg or .91v (this is a simplification) so since thrust is
proportional to v only 9% is involved for recovery. However, if the stators
are very efficient, they may lose this order of thrust through friction when
operating at their design point, and will lose even more when operating off
design.
The Scat stators I have seen were single surface fiberglass vanes that were
crude, and likely not to improve performance, and possibly add noise.
Barry Palmer, for <A
HREF="http://members.aol.com/sevtec/sev/skmr.html">Sevtec</A>
Ken Roberts
>engine and a hovercraft fan but the similarity is the blades on a jet
>engine are airfoils running in a fluid the same as a prop,,,,,,,,,,
>and thrust reaction is the same, by definition fast moving air hitting
>slow moving air causing reaction,,,, and noise.
>The air coming out the back of a jet engine is swirling very
>fast,(check out the contrails) just as the air coming off a prop is
>swirling,, my contention is, if we are all talking about the same
>thing, is that it is a waste of energy and possibly even a design
>problem to try to straighten it out.
>
>I agree with your statment that air/thrust is coming out at an angle
>to the direction of travel is a waste of energy but I would like to be
>convinced that trying to straighten it out is less of a waste.
ray,
i have no real data on this myself, since i've never built stators before or had
anything bigger than a hair dryer that used them. (if even that big)
i've talked to one racer from canada, at the troy, oh hover-in, who says his
stators added about 80 lbs of thrust. considering that he was in formula 2,
this would be a considerable benefit. i have to take his word for it, though,
that all that increase can be attributed to just the stators.
also, i think the most direct measurement an amateur could make of the stator's
effectiveness would be a static thrust test. don't you think?
>The length of the duct in a jet probably has an effect on the swirling
>action and increases the thrust but is the increase enough to offset
>the drag loss inside the tail pipe. Do aircraft designers take the
>length of the duct into account when designing the airplane or is it
>simply a weight and balance question of where to place the engine?
>I don't recall but I don't remember ever seeing the columns holding
>the afterburner turbulators in place being any thing more than
>straight symetrical airfoils, if it were an advantage to stop by
>reversing the direction of swirl I would think the designers would
>build in an airfoil to accomplish this.
>Most engines with afterburner, reheat to the British, use variable
>diameter nozzles to increase thrust and to control Exhaust Gas
>Temperature.
from what i've read so far, they find a balance between thrust gains, weight,
and drag when they decide that stuff. there may also be a consideration for any
additional hardware they might want to put back there, like reversing buckets.
i've never noticed these on a commercial jet, but they almost have to be there.
another thing to consider is that something which may not be worthwhile for a
jet engine manufacturer may well be within reason for a recreational
hovercrafter. also, those jets may (maybe you can say) have supersonic air
running through them, which would probably change properties of the engine
somewhat. there are so many variables, even the number of props, which could
alter the usefulness of the final stators. here's where my math and my
understanding of the subject falls seriously short. i just don't know.
i would, however, be fairly game to try it out.
>keep up the comments, I like to be proven wrong, I learn from that.
>
>Ray Toews
it's good to have a discussion like this. gets everyone thinking.
Ken Roberts
i suspected there may be differences in the feasibility of straigteners between
jets and hovercrafts, but don't as yet have either the math or the experience to
know for sure.
also, i came up with the .91 figure, but didn't publish it because i didn't
think i knew what i was talking about. it's good to know my intuition was
correct. again, that would be a huge simplification since the exit angle
wouldn't be the same at every radius, or even at every angle, since there's a
hull in front of there someplace.
my argument isn't that stators should be on every hovercraft. quite the
contrary. i think they're probably a lot of work for not much performance
increase, and a negative effect if the builder isn't paying attention. however,
if you're trying to tweak every last bit out of your hovercraft, they may be
worth the effort.
NWCedarDecks
>i've talked to one racer from canada, at the troy, oh hover-in, who says his
>stators added about 80 lbs of thrust. considering that he was in formula 2,
>this would be a considerable benefit. i have to take his word for it,
>though,
>that all that increase can be attributed to just the stators.
>
about what a 277 rotax in a scat puts out. (28hp)
ED
Ken Roberts
ed, i can't say for sure what the stators gave him in additional thrust.
however, since my hovercraft is not much bigger than a scat and can be expected,
with my engine, to deliver over 500 lbs thrust if everything is ideal, i'd say
that this could be possible.
and, just for clarity, i said '80 pounds of thrust' not '80 horsepower of
thrust.'
my craft is formula 1, which mean 500 cc or more. formula 2 is less than 500
cc, but don't know what the lower limit is.
from the references i've been reading, a good prop and/or duct can deliver
something like 5 or 6 lbs thrust per horsepower, in the real world. a 'perfect'
system could supposedly deliver 12 lbs per horsepower, but i take that to mean,
'if there is no loss of energy in the system.' that is, of course, impossible.
still, i'd say that 6 lbs of thrust, or 50% efficiency, should be possible.
it could be that my numbers are completely fiction, or that i'm understanding
the material incorrectly.
what i'm getting at is, your 277 rotax does not put your scat into the formula
2 class. it's perfectly reasonable that an extremely more powerful hovercraft
could, through an improvement in the thrust efficiency, gain more thrust than a
28 hp engine puts out on a scat. we're not comparing apples with apples here.
for example, take my hovercraft. i've got a uh-12r with a 583 rotax on it.
skidoo lists this engine as delivering 98 hp, for the year that i suspect the
engine is.
my hovercraft has 200 lbs of static thrust. this is ridiculously low. today i
ran the engine with a tachometer on it for the first time, and discovered that
my prop isn't using all the available power: i need a steeper pitch. i just
talked with bob windt of universal, who says that i should be able to double
that just with a prop change.
this means that i can improve my thrust by 100% of current thrust simply with
replacing the prop. this is a 200 lb thrust gain. if everything is right with
the whole craft, i should be able to get something near 500 lbs in real life.
admittedly, there's not much i could use that thrust for on a craft that weighs
less than 500 lbs empty. if i get 400 lbs i'll be more than happy, but may
continue to shoot for more efficiency just to get it.
the guy i was talking to, with his stator, was quite proud of it. i don't know
what thrust he had before or after he added the stator, but i can suspect he was
near 350 or 400 lbs at the end. the numbers i was using for deflection of the
air were purely fabricated, so i don't know what improvements are possible with
a stator.
Ray Toews
wrote:
>On 29 Oct 2000 22:55:21 GMT, NWCedarDecks <nwceda...@aol.com> wrote:
Ken,,with 500 lbs thrust on a 500 lb craft you should be able to
(pardon the pun),,, hover,,,eh? If you can increase thrust a little
bit more you should be able to accelerate vertically. That would be
something to see.
On a Tierra ultralite we experimented with a simple spring scale and
with a 503 of 50 hp we could optimize a 72 inch warp prop to provide
250 lbs thrust at 6200 engine rpm, at 6500 erpm the tips of prop
would go supersonic, thrust went down and noise went WAY up. I believe
the gearbox was a 2.13/1,,,what ever rotax uses on a A box.
Rough science but interesting.
Ray Toews
Ken Roberts
>(pardon the pun),,, hover,,,eh? If you can increase thrust a little
>bit more you should be able to accelerate vertically. That would be
>something to see.
>On a Tierra ultralite we experimented with a simple spring scale and
>with a 503 of 50 hp we could optimize a 72 inch warp prop to provide
>250 lbs thrust at 6200 engine rpm, at 6500 erpm the tips of prop
>would go supersonic, thrust went down and noise went WAY up. I believe
>the gearbox was a 2.13/1,,,what ever rotax uses on a A box.
>Rough science but interesting.
>
>Ray Toews
ray,
that weight is empty--no fuel, and no me. also, no tools. i'm not likely to
leave the car with no tools. there's considerably less than a 1:1
weight-horsepower ratio when i leave the ramp. i'm not exactly a small boy.