Designing effective puff ports
yvan...@my-deja.com
Does anyone know how to calculate thrust given air presure and flow?
Here's my idea (Yet another one!):
Regular puff ports which take air presure from the skirt or cushion on a
craft aren't much use from what people tell me. I guess just the
slightest breeze overpowers them.
Lets say you build a retractable air scoop inside the lift fan duct of
your craft and channel this air to an appropriate nozzle further along
on the hull of your craft when needed.
How would the thrust be calculated, given a fan flow and pressure, and
then the outlet nozzle area? For now, maybe we could exclude energy
losses in the puff port pipe.
Thanks for any help, Yvan (a guy who can't calculate worth a puff.)
P.S. Has this phrase been truncated? If so, who you gona'
Sent via Deja.com http://www.deja.com/
Share what you know. Learn what you don't.
CedarDecks
work better.
or you could do a Gimbal Fan
see it here
http://www.aeromobile.com/gimbalfan1.htm
Cedar Decks
John Carter
yvan...@my-deja.com wrote:
> Designing effective puff ports
>
> Does anyone know how to calculate thrust given air presure and flow?
>
> Here's my idea (Yet another one!):
>
> Regular puff ports which take air presure from the skirt or cushion
on a
> craft aren't much use from what people tell me. I guess just the
> slightest breeze overpowers them.
>
> Lets say you build a retractable air scoop inside the lift fan duct of
> your craft and channel this air to an appropriate nozzle further along
> on the hull of your craft when needed.
>
> How would the thrust be calculated, given a fan flow and pressure, and
> then the outlet nozzle area? For now, maybe we could exclude energy
> losses in the puff port pipe.
>
> Thanks for any help, Yvan (a guy who can't calculate worth a puff.)
The formula boils down to F=P/A, where F=force in lbs, P=pressure in
lbs/ft^2, and A=area in ft. You can plainly see that a 1ft^2 puff port
on your standard consumer-sized hovercraft is going to give you 10-12
lbs. of force under IDEAL conditions. The reason puff ports work (sort-
of) on larger hovercrafts are because they have a supply of air coming
directly off a 1000 or more H.P. turbine engine. Remember, turbines
are rated in several hundreds to thousands of cubic feet per SECOND!
Puff ports....forget them. You'll be sending less money to the Tylenol
company!
My $0.02
John Carter
--
Hoverclub of America #2430
http://www.losalamos.com/hovernut
yvan...@my-deja.com
these craft will fare out in the real world over the next few years.
John, humm, yes, small puff ports are not very effective. I can easily
see a small breeze putting more presure on the craft than the puff port
can handle.
I'm looking at the idea due to a comment about a 32ft long Sevtec
Mariner being hard to dock. Just as a free thinking exercise, if we take
the case of a Mariner, with 2x 2.2liter engines, each giving 100HP+(?)
to a lift and thurst fan pair.
Lets say you can uncouple the thrust props (or feather them ?), and are
only spinning the twin lift fans. That means the craft can be kept on
cushion with 40% of power, and the 60% extra could be diverted to some
fore and aft puff ports. That would give you theoreticaly well over
100hp just for your puff ports. Maybe that could finaly push them from
gizmos to real usable manouvering thrusters.
The problem is, I don't know what kind of presure a typical Multiwing
type lift fan develops in a static condition like that. I'm sure it's
over 10 or 12lbs.
BTW, if you put a constricting nozzle on your puff port, wouldn't you
trade a bit of volume for higher velocity and gain effectiveness?
Y
SEVTEC
>From: John Carter <jchov...@losalamos.com>
>Date: Tue, 06 July 1999 06:00 AM EDT
>Message-id: <7lsk3s$agd$1...@nnrp1.deja.com>
Puff ports are only effective if there are massive amounts of power available.
For instance, a Vanguard gets about 16hp total from its 18hp engine.Of that
power, 8.5hp are going to the thruster, 7.5hp to the lift system. While the
propeller gives about 75# static thrust, the lift system, if ducted to gain
its entire volume for thrust, would net about 18lb.
Since 345# empty weight Vanguards may operate at gross weights of the order of
500# to over 900# (over water), 18lb would be hardly noticeable.
Puff port performance can be improved a small amount by tapping the fan
directly for thrust flow, but this would require a bulky system, and there is
not much to be gained, especially considering the increase in skirt drag caused
by starvation of the cushion is usually greater than any force that can be
exerted with a puff port.
As an example of the unworkability of puff ports, I watched an SRN-6 hovercraft
get stuck on the transition from its 1 in 10 (guess) ramp to the level hard
standing. Numerous attempts at various propeller pitches did not dislodge the
craft. The operator then discharged his passengers, and tried again without
success. The ramp manager then walked out, but his back to the bow of the
craft, and pushed it around.
Puff ports will work at low speeds on water, however, but there are better
solutions, such as dual variable pitch propellers, that can net advantages
beyond low speed control.
While Explorer has proved itself capable of being maneuvered in and out of
marinas in spite of having no reverse thrust, there is no doubt that a couple
extra hands will be needed for a full length Mariner in tight quarters.
Barry Palmer, for <A
HREF="http://members.aol.com/sevtec/sev/skmr.html">Sevtec</A>
CedarDecks
But it won't help on land
Cedar Decks
Kevin J. Kauffman
Especially the part about the arms -- I really need the exercise! :^)
Kevin
--
ke...@kauffman.net
You will never be lost if you have no destination.
You will never be late if you have no deadline.
manicm...@my-deja.com wrote in message <7luan5$url$1...@nnrp1.deja.com>...
>In article <19990706172741...@ng-cn1.aol.com>,
>How about a trolling scooter for land, what if the trolling motor was an
>electric, direct drive, rubber pattle wheel, that would offer manuvering on
>lan. ( al-be-it sounding like a manic duck chasing a proziac )
>
>As a reverse bucket. Pitcure twin stick control. On both sides of the
thrust
>fan is a rigid fertical fin (1) at a neutrial angle so to be as " not there
"
>as possinle during normal operation (ie straight ahead).
>
>Each Stick operates a side of a split rudder ( or rudders ) . Now you steer
>like a bull dozer, right hand forward - left hand back - turn left. The
other
>way, the other way.
>
>During normal operation the rudders halves stay together like two playing
>cards. When you pull both sticks back the rudders seperate like a
butterfly's
>wings until they make contact with the vertical fins, see (1). This creates
a
>shield to direct air flow forward. Voila, buckettes that dissapear when not
>in use. Also by allowing some air to escape from the left or right side
>rudder half at a time some directional effect may be realized.
>
>An added bonus would be the Arnold Swatzerniger like arms you will get by
>pulling the rudders closed across several hundred pounds of thrust !
>
>Manic
Kevin J. Kauffman
think. I had the same idea for burying a big lift fan inside the craft and
using a large puff port with vanes (rudders?) for thrust. I got both
encouraging and discouraging words. I guess the numbers don't lie, but I'm
not convinced it won't work.
I have a spreadsheet for calculating HP, CFM, thrust, etc. for any
combination of craft size, fan, engine, and with any arbitrary efficiencies
you wish to put in. Since the inefficiency of slamming the lift air into
the water and then turning it (at LARGE volume flow rates!) 90 degrees and
out a port seemed to be the biggest problem that anyone pointed out, I
plugged in 25% for everything. This yielded a theoretical thrust of almost
100 lbs. with a hover gap of 1/2 in. using about a 45 HP engine.
This seems pretty good for a craft with an estimated all-up weight under
800 lbs. Of course, if I really trusted my calculations, I'd be building
this thing already! Instead, I just keep researching and calculating.
One encouraging finding was the Hovershuttle made in New Zealand. It
works on this principal. It's kinda big and uses a big engine. I think it
should work if scaled down, too. Who knows? I may end up wasting a whole
bunch of money, but at least then I'll know for sure!
Kevin
--
ke...@kauffman.net
You will never be lost if you have no destination.
You will never be late if you have no deadline.
yvan...@my-deja.com wrote in message <7lru4c$3b9$1...@nnrp1.deja.com>...
>Designing effective puff ports
>
>Does anyone know how to calculate thrust given air presure and flow?
>
>Here's my idea (Yet another one!):
>
>Regular puff ports which take air presure from the skirt or cushion on a
>craft aren't much use from what people tell me. I guess just the
>slightest breeze overpowers them.
>
>Lets say you build a retractable air scoop inside the lift fan duct of
>your craft and channel this air to an appropriate nozzle further along
>on the hull of your craft when needed.
>
>How would the thrust be calculated, given a fan flow and pressure, and
>then the outlet nozzle area? For now, maybe we could exclude energy
>losses in the puff port pipe.
>
>Thanks for any help, Yvan (a guy who can't calculate worth a puff.)
>
>P.S. Has this phrase been truncated? If so, who you gona'
>
>
Ken Roberts
> craft aren't much use from what people tell me. I guess just the
> slightest breeze overpowers them.
i can't see how a puff port would be practical for a recreational hovercraft, since it all boils
down to a high pressure inside the lift chamber. this implies that to get an effective puff port
you'd need to increase pressure, which means increase weight-per-area, which means you suffer in
other ways.
one thing that does come to mind, though, is a control somewhat like a helicopter uses:
take a fan, flat blades (meaning no twist) maybe 18" diameter. keep it spinning fairly quickly, and
when you want to have thrust in some direction, you alter the pitch in the appropriate direction.
the fan is arranged so that the air goes either left or right. replacement puff port, right?
manicm...@my-deja.com
cedar...@aol.com (CedarDecks) wrote:
> I also like the elc. trolling motor Idea.
> But it won't help on land
> Cedar Decks
How about a trolling scooter for land, what if the trolling motor was an
electric, direct drive, rubber pattle wheel, that would offer manuvering on
lan. ( al-be-it sounding like a manic duck chasing a proziac )
As a reverse bucket. Pitcure twin stick control. On both sides of the thrust
fan is a rigid fertical fin (1) at a neutrial angle so to be as " not there "
as possinle during normal operation (ie straight ahead).
Each Stick operates a side of a split rudder ( or rudders ) . Now you steer
like a bull dozer, right hand forward - left hand back - turn left. The other
way, the other way.
During normal operation the rudders halves stay together like two playing
cards. When you pull both sticks back the rudders seperate like a butterfly's
wings until they make contact with the vertical fins, see (1). This creates a
shield to direct air flow forward. Voila, buckettes that dissapear when not
in use. Also by allowing some air to escape from the left or right side
rudder half at a time some directional effect may be realized.
An added bonus would be the Arnold Swatzerniger like arms you will get by
pulling the rudders closed across several hundred pounds of thrust !
Manic
yvan...@my-deja.com
manicm...@my-deja.com wrote:
> In article <19990706172741...@ng-cn1.aol.com>,
> cedar...@aol.com (CedarDecks) wrote:
> > I also like the elc. trolling motor Idea.
> > But it won't help on land
> > Cedar Decks
>
> How about a trolling scooter for land, what if the trolling motor was
an
> electric, direct drive, rubber pattle wheel, that would offer
manuvering on
> lan. ( al-be-it sounding like a manic duck chasing a proziac )
>
That's it! We've got it all wrong! Forget about this whole impractical
hover/air cushion thing, just three electric trolling scooters driving
rubber paddle wheels on each corner of a trinagular frame/hull!
Man, why didn't we think of that sooner. I'm going off to by stocks in
the electric trolling scooter direct drive rubber paddle wheel industry,
RIGHT NOW! This is gona be big man, real big.... MANIC, I LUV YA BABY!
On the other hand, if that doesn't work out, here's my other somewhat
less creative idea:
From my fooling around with my el cheapo cardboard wind tunnel, I have
noticed that if you try to redirect air, like in a reverse thrust
situation, you have to provide lots of panels to convince the air to
truly reverse direction a full 180 degrees.
If you have two panels that split apart, each at a 45 degree angle, you
would think that the air would leave the second panel at about 135 (90+
45) degrees from the original direction of flow, which would give you
about half the original thrust as reverse thrust. But in reality, the
air leaving the second panel has been deflected only about 110 degrees
at the most, which gives about 22% of the original thrust converted to
reverse pressure, which isn't much. Not yet reversing buckets, more like
reversing spoonfulls, but still, there is hope...
So I think you have to add a third panel which fits against the edge of
the second 45 degree panel. This third panel would be fixed, and always
aligned in the normal air flow of the craft, so it wouldn't be to much
of a drag. If it is wide enough, it should be able to get the air to
reverse to 160-170 degrees or so, which gives about 66 to 77% of flow
converted into reverse thrust. That's not too bad, but to get those
numbers, you also need a top plate, to avoid air just blasting out the
top of the reversing vanes. But the top plat isn't that bad, cause you
need something on top to support the reversing vanes anyways.
In the end you have a Big Boxy Reversa-Thrusta Thingy behind your prop,
spending most of its time not realy doing much except slowing you down
when you're just trying to go regular-plain-old-forward. So kiss maybe
25%-30% of your top end speed goodbye. For a real life example of this
design implementation, look at the Canair craft. They ain't fast, but
they look cool, and can go backward while maintaining steering control.
Or give up and buy a Sevtec!
Funny thing is, when ever I try to solve this reverse thrust/puff port
conumdrum, I end at reversible thrust props instead.
Maybe that's the real solution, build a Mariner or Explorer, then take a
few thousand bucks and try to find/have someone machine a pair of nice
reversable thrust prop hubs.
But that still doesn't solve the problem for craft with only one thrust
prop. Maybe a realy sleek low drag version of the Big Boxy Reversa-
Thrust Thingy would work? Humm, full radial vane design?
And for scrawny nerds like me (heck, Arnold's arms probably weigh more
than I do!) instead of having to force the reversing vanes shut with
brut strength, how about just sliding their pivot point forward to
induce them to snap shut?
Yvan
Is this post long enough? Would anyone like me to make it
CedarDecks
>
>take a fan, flat blades (meaning no twist) maybe 18" diameter. keep it
>spinning fairly quickly, and
>when you want to have thrust in some direction, you alter the pitch in the
>appropriate direction.
>the fan is arranged so that the air goes either left or right. replacement
>puff port, right?
I thought of that too. But how to drive it?
and then you have more weight to deal with.At least 30 pounds.
Cedar Decks
John Carter
> The formula boils down to F=P/A, where F=force in lbs, P=pressure in
> lbs/ft^2, and A=area in ft. You can plainly see that a 1ft^2 puff
port
> on your standard consumer-sized hovercraft is going to give you 10-12
> lbs. of force under IDEAL conditions.
OOPS!!
The formula is F=PxA, not F=P/A. That's what I get for digging Pacal's
laws out of my brain after a 18:00-06:00 shift! Thanks, googleplex!
John
--
Hoverclub of America #2430
http://www.losalamos.com/hovernut
manicm...@my-deja.com
> hover/air cushion thing, just three electric trolling scooters driving
> rubber paddle wheels on each corner of a trinagular frame/hull!
>
> Man, why didn't we think of that sooner. I'm going off to by stocks in
> the electric trolling scooter direct drive rubber paddle wheel industry,
> RIGHT NOW! This is gona be big man, real big.... MANIC, I LUV YA BABY!
Hail the reigning Picaso of sarcasm. For your information no one is currently
making rubber paddle wheels to fit trolling motors, it is a virgin territory
for some enterprising entrepreneur with vision and won't be ready for stock
market wannabees for days.
> On the other hand, if that doesn't work out, here's my other somewhat
> less creative idea:
>
> From my fooling around with my el cheapo cardboard wind tunnel, I have
> noticed that if you try to redirect air, like in a reverse thrust
> situation, you have to provide lots of panels to convince the air to
> truly reverse direction a full 180 degrees.
>
> If you have two panels that split apart, each at a 45 degree angle, you
I was thinking 90 degrees, I was !
> would think that the air would leave the second panel at about 135 (90+
> 45) degrees from the original direction of flow, which would give you
> about half the original thrust as reverse thrust. But in reality, the
> air leaving the second panel has been deflected only about 110 degrees
> at the most, which gives about 22% of the original thrust converted to
> reverse pressure, which isn't much. Not yet reversing buckets, more like
> reversing spoonfulls, but still, there is hope...
>
> So I think you have to add a third panel which fits against the edge of
> the second 45 degree panel. This third panel would be fixed, and always
> aligned in the normal air flow of the craft, so it wouldn't be to much
> of a drag. If it is wide enough, it should be able to get the air to
> reverse to 160-170 degrees or so, which gives about 66 to 77% of flow
> converted into reverse thrust. That's not too bad, but to get those
> numbers,
I did nention the fixed verticals, ( re item marked #1 )
> you also need a top plate, to avoid air just blasting out the
> top of the reversing vanes. But the top plat isn't that bad, cause you
> need something on top to support the reversing vanes anyways.
I thought of that but figured it could be a modification if the back and
sides were not enough.
> In the end you have a Big Boxy Reversa-Thrusta Thingy behind your >prop,
Thats my kind-a name though .
> spending most of its time not realy doing much except slowing you down
Have you been talking to my wife?
> when you're just trying to go regular-plain-old-forward. So kiss maybe
> 25%-30% of your top end speed goodbye. For a real life example of this
Would it really be that drastic for smooth vertical pannels ? ( I'm not the
voice of experience remember I have never even seen or heard a hover run
before)
> design implementation, look at the Canair craft. They ain't fast, but
> they look cool, and can go backward while maintaining steering control.
>
> Or give up and buy a Sevtec!
I have Vanguard plans and plan to build to spec., but since that hasn't
started yet there's nothing to talk about.
> Funny thing is, when ever I try to solve this reverse thrust/puff port
> conumdrum, I end at reversible thrust props instead.
>
> Maybe that's the real solution, build a Mariner or Explorer, then take a
> few thousand bucks and try to find/have someone machine a pair of nice
> reversable thrust prop hubs.
>
> But that still doesn't solve the problem for craft with only one thrust
> prop. Maybe a realy sleek low drag version of the Big Boxy Reversa-
> Thrust Thingy would work? Humm, full radial vane design?
Glad to see you haven't forgotten me !!!!
> And for scrawny nerds like me (heck, Arnold's arms probably weigh more
> than I do!) instead of having to force the reversing vanes shut with
> brut strength, how about just sliding their pivot point forward to
> induce them to snap shut?
I wasn't considering it any way, but good analytical thinking !
> Yvan
>
> Is this post long enough? Would anyone like me to make it l
Again God flexes his finger on the delete button of heavens master forum
control board .
Manic Mechanic
Ken Roberts
> and then you have more weight to deal with.At least 30 pounds.
> Cedar Decks
i was thinking a belt, or something. it wouldn't need more than a couple horses, i think. this is
a steering mechanism, not a major thrust source.
what about round belts? they're really not that great except you don't have to worry about twisting
it for turns around corners.
yvan...@my-deja.com
Yup, you did mention the extra vertical fin. Obviously, I read to
little, and write to much!
I think my estimate of top end speed lose is in the general area to be
expected. The reason is the Vanguard has a big prop, and to reverse it
would need a large Reversa-Thingy.
Because it takes four times the HP to double a given speed, due to the
increasing effects of aero drag, speed is hard to gain, and very easy to
loose.
Maybe the solution is just a really sleek design. Not straight vanes,
all surfaces would be funky curves that don't mess with the air flow and
nest into each other like the afterburner control vanes on those sexy
fighter jet engines. (Oh baby, now your talkin'!) : )
The thing I've notice from my windtunnel is that air leaves a prop or
fan in a rather groovy swirling spiral pattern. Any straight surface in
the prop flow is actualy at an angle to this flow pattern. The air flow
from the prop can be at up to 30 dergees off from the axis of the fan,
so most of the surface area of the "straight" rudder or vane is actualy
wedged in at pretty bad angle air flow wise. You can even see flow
separation and air moving backword in this whole mess. Not efficient at
all. The solution is just curved rudders, but they are a pain to build
and design so they hinge right.
As for:
> > Maybe that's the real solution, build a Mariner or Explorer, then
take a
> > few thousand bucks and try to find/have someone machine a pair of
nice
> > reversable thrust prop hubs.
As if I have a few grand! Ha.
Yvan.
PS. Yes, I also have a hard time with hamster language.
Let's see if devine intervention gets
yvan...@my-deja.com
"Kevin J. Kauffman" <ke...@kauffman.net> wrote:
> I posted in here a while ago on a thread about reducing craft
noise, I
> think. I had the same idea for burying a big lift fan inside the
craft and
> using a large puff port with vanes (rudders?) for thrust. I got both
> encouraging and discouraging words. I guess the numbers don't lie,
but I'm
> not convinced it won't work.
> should work if scaled down, too. Who knows? I may end up wasting a
whole
> bunch of money, but at least then I'll know for sure!
>
> Kevin
Kevin, ten years ago, I was developing this neat idea for a WIG craft. I
chickened out of building the full size version, for a variety of half
valid reasons.
Now there's someone building almost exactly what I was working on. Just
go look at the Weber Starcruiser site under WIG.
So if you don't want to end up old and bitter with nothing better to do
than post half coherent messages on alt.rec.hovercraft that end up
getting the ends chopped of by god, don't do like me. Build what you
have in mind. That's what the Wright brothers did. They politely
listened to criticisim, ignorned it all, carefully tested their ideas
out, and invented the airplane.
Yvan. Look, I bet even this message will g
manicm...@my-deja.com
yvan...@my-deja.com wrote:
> Oops, sorry Manic. (as in a Homer style "Doh!" slap-to-the-forehead.)
>
> Yup, you did mention the extra vertical fin. Obviously, I read to
> little, and write to much!
>
> I think my estimate of top end speed lose is in the general area to be
> expected. The reason is the Vanguard has a big prop, and to reverse it
> would need a large Reversa-Thingy.
>
> Because it takes four times the HP to double a given speed, due to the
> increasing effects of aero drag, speed is hard to gain, and very easy to
> loose.
>
> Maybe the solution is just a really sleek design. Not straight vanes,
> all surfaces would be funky curves that don't mess with the air flow and
> nest into each other like the afterburner control vanes on those sexy
> fighter jet engines. (Oh baby, now your talkin'!) : )
>
> The thing I've notice from my windtunnel is that air leaves a prop or
> fan in a rather groovy swirling spiral pattern. Any straight surface in
> the prop flow is actualy at an angle to this flow pattern. The air flow
> from the prop can be at up to 30 dergees off from the axis of the fan,
> so most of the surface area of the "straight" rudder or vane is actualy
> wedged in at pretty bad angle air flow wise. You can even see flow
> separation and air moving backword in this whole mess. Not efficient at
> all. The solution is just curved rudders, but they are a pain to build
> and design so they hinge right.
My wife just caught me noding my head and softly murmering yes to the
computer, what a look I got, but thats ok I just experienced an apifiny or
what ever you call one of those thingeys when you just realize something you
havn't that you never thaught of. Ever.
> As for:
> > > Maybe that's the real solution, build a Mariner or Explorer, then
> take a
> > > few thousand bucks and try to find/have someone machine a pair of
> nice
> > > reversable thrust prop hubs.
> As if I have a few grand! Ha.
I here that, my Internet connection is in jerpody due to domestic budjet cut
backs.
> Yvan.
> PS. Yes, I also have a hard time with hamster language.
> Let's see if devine intervention gets
Funny I never had a problem with that one. Try studying old telegraph code,
then chewing out the rythem on a piece of conduit.
Manic
Kevin J. Kauffman
>Share what you know. Learn what you don't.
Thanks for the words of encouragement, Yvan. The Wright brothers, eh?
Hmmmm.... Maybe I need to get my brother involved to make this thing work!
I haven't given up, I'm just reluctant about wasting the $$$. I'll probably
have to wait till I'm independently wealthy to do any full-scale
experimenting.
BTW, your message did g
Ken Roberts
> think. I had the same idea for burying a big lift fan inside the craft and
> using a large puff port with vanes (rudders?) for thrust. I got both
> encouraging and discouraging words. I guess the numbers don't lie, but I'm
> not convinced it won't work.
just had an idea: i suggested a sideways-oriented fan, to provide sideways thrust. what about a
poor-man's imitation, just put a leaf blower on a swivel? may give you an idea if that's enough
thrust.
rwpo...@pacbell.net
> think. I had the same idea for burying a big lift fan inside the >craft and using a large puff port with vanes (rudders?) for thrust. I >got both encouraging and discouraging words. I guess the numbers don't >lie, but I'm not convinced it won't work.
What about having two lift engines, one fore and one aft, with
vanes in the discharge. The vanes are controlled by a central
control stick and would allow the lift air to be directed in any
direction, allowing the craft to move in any direction. The idea
would be like the Aeromobile, but without the complexity. If
this setup allowed enough horizontal thrust, there would be no
need for a thrust engine.
--
Ron P.
SoCal Especial
34 23.346/118 35.264
ICQ 22154112
Kevin J. Kauffman
earlier crafts. Actually, I believe it all stems from that Popular Science hover from oh so many years ago -- the metal one with
the two ports in the aft for thrust/steering.
--
ke...@kauffman.net
You will never be lost if you have no destination.
You will never be late if you have no deadline.
rwpo...@pacbell.net wrote in message <37861DD0...@pacbell.net>...
CedarDecks
you will need so much HP and You will move a lot a of air that it will most
likely be louder than a big SEV. Now in your cabin it could be even louder.
But thats just my opion.
Cedar Decks
yvan...@my-deja.com
> Thanks for the words of encouragement, Yvan. The Wright brothers, eh?
> Hmmmm.... Maybe I need to get my brother involved to make this thing
work!
> I haven't given up, I'm just reluctant about wasting the $$$. I'll
probably
> have to wait till I'm independently wealthy to do any full-scale
> experimenting.
>
> BTW, your message did g
>
> --
> ke...@kauffman.net
Have you looked into BIG models for testing your scheme? Most hovercraft
models are 30 inches long or so, not much use for extracting good data
for full size craft.
But if someone didn't have the time/cash/motivation/space/tools/
experiance to build a full size machine, a big model, about 4 by 8 feet
in hull length, powered by a 5 or 6HP retired mower engine would give
very good info/experiance for a craft twice as big, say 16 by 8 ft.
A model craft that size costs very little. It is not big enough to use
up much material. The whole thing could be done in luan and pine or
spruce 2x1s or blue/pink foam. Around here a 4x8ft luan sheet is $6
Canadian...
The interesting thing is anything that works on a 4x8 craft will work
better on a 8x16 craft, due to the efficiency gained with increased
size. (eg. four times the cushion area, but only twice the cushion
perimeter air gap = gain in efficiency)
Also, it is -very- easy to use the 4x8 model to help build the 8x16
version. You just take a mesurment and double it. I've used this trick a
few times, and it is astonishing how fast you can build the full size
project with that method.
Anyways, just an idea. : )
Yvan
P.S. Also, it's easier to hide the project if it don't work! (g
Kevin J. Kauffman
ballpark of 7 ft. wide by 12-14 ft. long (that's all the space I have in my one free garage bay with a couple of feet to walk around
on each side), so maybe I'll try building a 3.5 x 6 -7 footer first. The only problem I see is scaling down the actual engine
size/weight. Maybe an electric motor would be better on such a model if I could find an old one to fit the bill.
I just might try it. I'd really like to have something that hovers with at least a minimum of useable thrust slapped together in
time for next year's Hoverrally, and this might be the best way for me to get away from the books and calculator and just get
started. And if I don't finish the full-sizer in time (I am King of the procrastinators), you may just see me cruisin' in on my
little half-scale model! (Actually, I'd probably need one under each foot to get me off the ground, so I better build two!)
Kevin
--
ke...@kauffman.net
You will never be lost if you have no destination.
You will never be late if you have no deadline.
yvan...@my-deja.com wrote in message <7m6l7h$ubm$1...@nnrp1.deja.com>...
Chris Edmiston
it off of 1 fan only???
CedarDecks <cedar...@aol.com> wrote in message
news:19990706030454...@ng-fu1.aol.com...
Chris Edmiston
with an abnormally large lift fan engine and the fan have rudders to blow
air against the ground (or water) to move the craft...
I am going to build a craft (hopefully very soon) and I might try your
ideas, I wouldn't use it & go into production, but just as a pleasure
craft... Please calculate the results on a 5 x 10 craft for 1 with fully
loaded weight of 600 lb. on a 15 hp. engine. and post your results. And
give me your recommendations... (good idea, bad idea)
Thanks, Chris Edmiston
Kevin J. Kauffman <ke...@kauffman.net> wrote in message
news:93162044...@news.remarQ.com...
manicm...@my-deja.com
"Chris Edmiston" <webm...@customwebsitedesign.com> wrote:
> It says that the gimball fans require 2 per craft, is it possible to operate
> it off of 1 fan only???
Wouldn't a single gimble fan handle somewhat like an office chair with four
casters? You coast it in any direction you boost in but you can't point it.
Like driving a tank with a loose turet swinging willy nilly.
Manic
CedarDecks
>loaded weight of 600 lb. on a 15 hp. engine. and post your results. And
>give me your recommendations... (good idea, bad idea)
The only Hover your are going to get to work with that size and horse power
might be a Sev.
My Scat 1 takes 26 HP (2 stroke at that)
you can get about 350 lb into it. You have to work it to get on bubble with
that much weight.And I have done lots of stuff to improve.
Cedar Decks
yvan...@my-deja.com
calculator. It seems to work fine, but I'm no theory expert. I put in
some numbers for a 20x40ft craft just for fun, and though you might want
to take a look there also to see how much HP a 3.5x7 craft would take,
depending on variables. Here's the url: http://members.xoom.com/_XOOM/
HoverHome/
If you make two, you will have invented hoverskates. Or hoverboots?
I also have an idea for the shape of a air channeling duct/lift as
thrust combo for a craft like you talk about. I could model it in my 3D
software to make an illustration if you are interested in seeing what I
have in mind. (but I would need somewhere to post it)
BTW, there is nothing like putting down the books and calc for a little
bit of mind opening hands on stuff. I suffer from the same problem! <G>
Constant planing, no action!
CedarDecks) wrote:
> My Scat 1 takes 26 HP (2 stroke at that)
> you can get about 350 lb into it. You have to work it to get on bubble
with
> that much weight.And I have done lots of stuff to improve.
> Cedar Decks
Thanks for the interesting urls you posted, I allways look em up.
BTW, your scat is the one always chewing up its drive belt, no? Is the
fan noisy? I'm wondering what the fan diameter, and rpm
manicm...@my-deja.com
> The only Hover your are going to get to work with that size and horse power
> might be a Sev.
> My Scat 1 takes 26 HP (2 stroke at that)
> you can get about 350 lb into it. You have to work it to get on bubble with
> that much weight.And I have done lots of stuff to improve.
> Cedar Decks
Cedar:
How fast will your scat go flat out, calm water ?
Manic
Kevin J. Kauffman
A puff port is just an adjustable orifice in a craft's hull which bleeds a small amount of air out of the cushion to effect a
tiny amount of thrust, usually in a sideways direction, and usually only useful for maneuvering at low speeds. My idea is to use
one large puff port on the rear of the craft with vanes internal to the mouth of the duct. The lift system would have to be
considerably oversized so that, as the port is opened for more thrust, the engine could be revved to supply an ever-increasing CFM
of air while maintaining a constant cushion pressure. Basically the same as a conventional single-engine craft except there's no
splitter. The split is achieved by varying the thrust port opening AND adjusting engine output accordingly.
For the craft you described to me, here's what my spreadsheet spewed forth: To obtain the required minimum thrust of 60 lbs. (I
arbitrarily used 10% of your all-up weight), you would need to use a thrust port at least 5 sq. ft. in area with a minimum of a 44
HP engine. You'll have to select a fan that can absorb about 38 HP while supplying at least 385 cubic feet per second (23100 CFM)
of airflow at a static pressure of about 0.09 psi (2.5 in. water). Unfortunately, the 15 HP engine you wanted to use could only
supply a 1 sq. ft. thrust port and provide you with only about 18 lbs. of thrust. This would be next to useless.
One thing you must remember is that I'm figuring in terrible efficiencies (on the order of 25%) into most of these equations. If
you do some research/experimentation and can come up with a way to increase these, then your required HP will decrease. My
recommendation: Go for it! Remember the Wright Brothers! (see Yvan's post on 7/8!) Just be sure to do your homework first. I
just became seriously interested in hovercrafting about a year ago, and I thought for sure I'd have a craft built by now. But then
I began doing research, and realized how much there is to learn before you can design one of these things. Now I don't even know if
I'll have one ready for Hoverally 2000, but I sure hope to!
Best of luck,
Kevin
--
ke...@kauffman.net
You will never be lost if you have no destination.
You will never be late if you have no deadline.
Chris Edmiston wrote in message <7m8m69$l...@journal.concentric.net>...
>Kevin, let me get this straight, you are thinking of creating a hovercraft
>with an abnormally large lift fan engine and the fan have rudders to blow
>air against the ground (or water) to move the craft...
>
>I am going to build a craft (hopefully very soon) and I might try your
>ideas, I wouldn't use it & go into production, but just as a pleasure
>craft... Please calculate the results on a 5 x 10 craft for 1 with fully
>loaded weight of 600 lb. on a 15 hp. engine. and post your results. And
>give me your recommendations... (good idea, bad idea)
>
Kevin J. Kauffman
thinking, hoverboots.... I like the idea! (next project?)
As far as a 3D model of the duct you have in mind, if you'd like to work something up I'd be happy to see it -- so far my design
doesn't really use anything more than a standard lift duct. But isn't 3D modelling alot of work? I've been fooling around with
DesignCAD Pro 2000 and it takes me forever to model the simplest solid. Of course, I don't get to play with it that much. So, like
I said, if you'd like, go for it. Can't you just post it to the newsgroup? If not, you could email it to me.
Kevin
--
ke...@kauffman.net
You will never be lost if you have no destination.
You will never be late if you have no deadline.
yvan...@my-deja.com wrote in message <7mag70$f8$1...@nnrp1.deja.com>...
> Kevin, I took a look at the url Ceder posted for the lift engine
>calculator. It seems to work fine, but I'm no theory expert. I put in
>some numbers for a 20x40ft craft just for fun, and though you might want
>to take a look there also to see how much HP a 3.5x7 craft would take,
>depending on variables. Here's the url: http://members.xoom.com/_XOOM/
>HoverHome/
>
>If you make two, you will have invented hoverskates. Or hoverboots?
>
>I also have an idea for the shape of a air channeling duct/lift as
>thrust combo for a craft like you talk about. I could model it in my 3D
>software to make an illustration if you are interested in seeing what I
>have in mind. (but I would need somewhere to post it)
>
>BTW, there is nothing like putting down the books and calc for a little
>bit of mind opening hands on stuff. I suffer from the same problem! <G>
>Constant planing, no action!
>
>
> CedarDecks) wrote:
>> My Scat 1 takes 26 HP (2 stroke at that)
>> you can get about 350 lb into it. You have to work it to get on bubble
>with
>> that much weight.And I have done lots of stuff to improve.
>> Cedar Decks
>
>Thanks for the interesting urls you posted, I allways look em up.
>
>BTW, your scat is the one always chewing up its drive belt, no? Is the
>fan noisy? I'm wondering what the fan diameter, and rpm
>
>
CedarDecks
>How fast will your scat go flat out, calm water ?
>
>Manic
>
About 30 mph and from what I understand
the SCOUT SEV can keep up with me
with 12 hp!!!
Cedar Decks
Earl
CedarDecks wrote:
Hmmm, you think this says something about the efficiency of the scout?
:-)
--
efo...@att.net
In theory, theory and practice are the same. In practice..........
manicm...@my-deja.com
cedar...@aol.com (CedarDecks) wrote:
> >
> >How fast will your scat go flat out, calm water ?
> >
> >Manic
> >
>
> About 30 mph and from what I understand
> the SCOUT SEV can keep up with me
> with 12 hp!!!
> Cedar Decks
Cedar Decks:
With such a humble response, I fear that if you ever disagree with me I would
think I was lying.
Am I correct in thinking that the Scat would have the edge at acceleration
and tight course manovering? Over the Scout ?
Manic
yvan...@my-deja.com
the rather complex software, modeling is pretty fast unless you are
doing a very detailed item.
This idea I have has all these vane/rudders around the edge, and I would
like to put it somewhere where anyone who is interested in the type of
craft you talk about can see it so as to get creative feedback. I don't
know how to post a message to the newsgroup from where I read it which
is Deja.com. Also, some people realy dislike getting fat jpegs in their
mail.
Most times people put the jpeg up on a web site, but I don't got one!
Anyways, I'll start the duct model tonight, and then I'll see what we
can do with it.
Yvan
.
CedarDecks
>Am I correct in thinking that the Scat would have the edge at acceleration
>and tight course manovering? Over the Scout ?
>
If you put a veribale pitch prop on it it might keep up in a hole shot. But yes
I think I can leave a Scout at the starting line.
But if I lose my bubble I sure the Scout would Pass me.
Cedar Decks
SEVTEC
>Subject: Re: Designing effective puff ports
>From: cedar...@aol.com (CedarDecks)
>Date: Mon, 12 July 1999 02:46 AM EDT
>Message-id: <19990712024610...@ng-fb1.aol.com>
I am afraid horsepower wins, here. I have looked at a Scat 277, taken
measurements, and it has about the same top speed as a Scout on smooth water,
32mph.
While Scout planes out no more than 270#, the 277 Scat should get around 320 #
up. (You can play games and get much more up with either craft, I am talking
straight deep water planeout.)
While Scout gives 52# static, the 277Scat gets 90#.
However, no attempt has ever been made to "dial in" the prototype Scout, which
gets only a miserable 9 hp at 2810rpm, with its 12hp Tecumseh, while the Scat
is probably getting more like 23 at 6100 from its Rotax.
2.5/1 power advantage is an awfully lot of an advantage to overcome,
especially when the bigger engine weighs little more than the Scout engine, 59#
and the craft payloads are about the same.
Empirical values can be determined, such as skirt wipe friction coupled with
overall aerodynamic drag, which determines top water speed by analysing the
Scout raw test data and applying the results to the Scat. The data indicate
that the top speed of the 277 Scat should be around 44mph! And this is for a
32 inch open propeller on Scat. The problem is the duct, as far as I can see,
as the Scat has little more frontal area and skirt wipe drag of the two craft
should be about the same.
Curiously enough, the 277 Scat would likely hang on the hump before the Scout,
if there were headwind problems.
Now if I got to pick the course, where long distances and obstacles were to be
encountered Scout could win, but since it has nowhere the acceleration
potential of the 277 Scat, which is absolutely demanded for typical hovercraft
golf course and lilly pond racing environments, I am sure the Scat would have
the edge.
Maybe I could do a little dialling, or just drop a 16hp Vanguard (14hp) onto
Scout, and it would be no contest.
Barry Palmer, for <A
HREF="http://members.aol.com/sevtec/sev/skmr.html">Sevtec</A>
yvan...@my-deja.com
http://members.xoom.com/y_roy/epbimages/Yduct1a.JPG
That should display the diagram I made for the duct.
Just an idea, so all comments are welcome.
Yvan
.
.
.
.
Kevin J. Kauffman
thinking of. It looks like it'd be pretty tough to build and incorporate into a craft, though. At least a full 360 degree version.
Maybe half of one would work on the rear of a craft. Come to think of it, that's basically my idea -- half of one of your round
duct thingies but with the outlet duct all on one plane, not arced. That way all the vanes can be linked together and move in
tandem. It'd be quite a bit more work to sequentially open and close vanes around the perimeter of an arc. BUT I like the way it
looks -- maybe it'd be worth persuing. I'll have to think on that one.
Kevin
P.S. Thanks again for the great sketch. BTW, what software did you draw that in?
--
ke...@kauffman.net
You will never be lost if you have no destination.
You will never be late if you have no deadline.
yvan...@my-deja.com wrote in message <7mcie9$kcd$1...@nnrp1.deja.com>...
manicm...@my-deja.com
onto
> Scout, and it would be no contest.
> Barry Palmer, for <A
> HREF="http://members.aol.com/sevtec/sev/skmr.html">Sevtec</A>
>
Barry:
Since were on the subject I have a couple of questions.
1) If you did put the 16 hp on the Scout would you use the same thyust
prop? Would you not get comparable performance with a 12.5 ft Vanguard and a
16 hp?
2) On the vanguard video, where you dive off of the Vanguard and climb back
in again. Is that a 12.5 or a 14 foot Vanguard? Is it the 16 hp motor.
Manic
CedarDecks
>Maybe I could do a little dialling, or just drop a 16hp Vanguard (14hp) onto
>Scout, and it would be no contest.
>
>
>
Now your talking!!!
Well thats why my next hover will be a Sev
Vanguard.
But I'm not sorry for buying the Scat. I just pound on it and it keeps taking
it. Of course it's been fix alot, I spend to much time working on it.
Yesterday I was raceing up and down this long boat ramp ( no one uses this
ramp)
like a 100 feet up 40+% climb then the wind blew me off the side of it!!! Hang
on this is going to be rough!!EEKKKK!!
well I made it all the way to the water. And after replaceing 10 or 12 zipties
I was flying again! it was about 2 hours latter when I ran out of gas.
Cedar Decks
SEVTEC
>Date: Mon, 12 July 1999 08:27 PM EDT
>Message-id: <7me15v$3lp$1...@nnrp1.deja.com>
>
> > Maybe I could do a little dialling, or just drop a 16hp Vanguard (14hp)
>onto
>
>> Scout, and it would be no contest.
>
>Since were on the subject I have a couple of questions.
>
>1) If you did put the 16 hp on the Scout would you use the same thyust
>prop? Would you not get comparable performance with a 12.5 ft Vanguard and a
>16 hp?
>
>2) On the vanguard video, where you dive off of the Vanguard and climb back
>in again. Is that a 12.5 or a 14 foot Vanguard? Is it the 16 hp motor.
>
>Manic
>
The Vanguard in the video is a very light 285# 12 1/2 foot with manual start
Vanguard engine.
I have also dived off the Scout, and climbed back in deep water just to verify
the safety of Scout.
Not only could the same Scout thrust and lift rotors be used for 16hp, but the
drive could be the same. That means the weight bill for raising power is
almost totally paid in the present version of Scout. I would opt for the full
diameter rotors as on Vanguard, however.
Actually, even though it does not appear that the Scout is much different from
a 7X 12 1/2 foot Vanguard, there would be a major difference in performance,
with the Vanguard 16hp topping at 32mph smooth water, and the 5.5x10 foot Scout
getting to 38mph, a bit fast for sustained operation. It should also be noted
that with this conversion the Vanguard was able to haul 500 lb payload over big
waters whereas Scout would be only a wobbly two place, 330# payload.
If the builder does want a smaller craft, the Vanguard is a better bet, trading
maximum speed for more payload. That is why I advise people build it instead
of the Scout, unless one just has to have the smallest machine.
One application where a real small Scout-like craft would be a real boon, is as
an ice fall through rescue device for distributed small ponds and lakes where
it would be unreasonable to base a craft. It could be quickly deployed via
the back of a pickup, with two lifting it off and launching it onto the ice.
Scout then would haul a line out to the rescue site, the victim(s) would be
brought aboard, and the Scout would be hauled back on cushion via the line.
Other than that application, I prefer people build the Vanguard, even the 12
1/2 foot version, especially now that the Surveyor, which is 7 X 14ft, is
coming on.
It should be noted that it makes no sense to talk top speed comparisons of
surface skimmers, without noting the payloads the craft handle. It is easy to
get top speeds up by undersizing the hull so carrying ability is compromised.
yvan...@my-deja.com
BTW, I use Strata Studio Pro 2.5.3. on my macs, but it also runs on PCs.
Not a lot of people know about strata, but I like it. Lots of
features.(aka: slow to learn...)
Yeah, I think it would be quite a pain to build the system as pictured.
So that version is just for fun. A squared off version would be much
more practical like you mentioned. Maybe it could have two other ports
at the front, on each side of the cockpit for reversing.
Yvan
.
.
manicm...@my-deja.com
> with the Vanguard 16hp topping at 32mph smooth water, and the 5.5x10 foot Scout
> getting to 38mph, a bit fast for sustained operation. It should also be noted
> that with this conversion the Vanguard was able to haul 500 lb payload over big
> waters whereas Scout would be only a wobbly two place, 330# payload.
>
> If the builder does want a smaller craft, the Vanguard is a better bet, trading
> maximum speed for more payload. That is why I advise people build it instead
> of the Scout, unless one just has to have the smallest machine.
Barry:
If the 12.5 Vanguard were built with 18 hp would the performance be closer to
the 16 hp Scout.
I expect that the 12.5 ft Vanguard would loose some payload with the extra
weight of the 18 hp ( comming with electric start ) . How mutch does the
Vanguard's handeling suffer when you approach maximum payload.
Manic
SEVTEC
>Message-id: <7mgk07$2kp$1...@nnrp1.deja.com>
the ratio of power, so 32mph would go to 33mph, provided the same rpm were
maintained However, with the same drive, engine rpm would increase and maybe
32mph would go to 34mph, using the 12 1/2 foot hull.
In smooth water, as long as the surface skimmer has plenty of cushion air, the
payload is determined by what can be planed out. At speed, wake drag, which is
caused by the weight of the surface skimmer, is minimal, so extra weight will
not slow the craft significantly. If the craft has a marginal cushion air
supply, skirt wipe friction will increase significantly and top speed will be
reduced considerably.