Help: Paddlewheel vs propeller
Sam
earlier discussion on this topic.
My problem is:
I'm planning to build a small boat, for one or two persons, that uses Pedal
power. Even though there are usually Paddle-type pedal boats in boat parks I
suspect it might not be an efficient way of power use. Hence I'm considering
a propeller type.
My questions are:
1. Is a paddle boat more efficient than a propeller boat?
2. If not why aren't there many propeller Pedal boats?
3. Is there a minimum propeller rotation speed for satisfactory
thrust/power output?
4. Are there any prop. rotation speed vs. prop. diameter ratios that give
the best performance in thrust/power?
As you can see, I'm still keen on the propeller idea, but I need to know
what limitations, if any, that I may have with pedal power in this regard.
Your contributions will be highly appreciated.
Sam
Stephen Baker
Not necessarily, but probably, depending on the propeller selection
>2. If not why aren't there many propeller Pedal boats?
Because you need a hole in the hull for the shaft to go through, plus you need
a gearbox of some sort to convert a transversely rotating shaft to power a
longitudinally rotating shaft.
>3. Is there a minimum propeller rotation speed for satisfactory
>thrust/power output?
Again, it depends on the propeller and the pedaller.
>4. Are there any prop. rotation speed vs. prop. diameter ratios that give
>the best performance in thrust/power?
>
See "3" above.
Stephen C. Baker - Yacht Designer
http://members.aol.com/SailDesign/private/scbweb/home.htm
Al
> earlier discussion on this topic.
you can access the archives at www.google.com
If you run into problems, I'll have a go for you. It really is worth
reading that whole thread from end to end, there were some hydrofoil
links that I personally found really interesting.
Al
Barry Palmer
>From: saild...@aol.comnospam (Stephen Baker)
>Date: 3/26/02 10:31 AM Pacific Standard Time
>Message-id: <20020326133143...@mb-ch.aol.com>
There are certainly ways of approaching paddles vs propellers in a theoretical
way.
The most important part is the projected area of the propulsion device, can it
be made large so the propulsive efficiency can be maximal, as less energy is
expended the more mass flow is affected.
This is of particular importance as I use air drive, with very large projected
thropughflow area, where the density of water is 800 times as dense as air.
For the propulsive efficiencies to be the same, the air propeller would have
to be (800) ^1/2 or 28 times the water propeller diameter, for the same
propulsive efficiency. However, there are equalizers in the form of
cavitation, ventilation, centerbody blockage, etc, that do not occur with an
air propeller, (but if you have the water under the hull all the time, water is
best).
Comparing a paddle wheel with a water screw has the nature of comparing the
projected area, and the size and weight of the machinery to get that area.
Also the mechanical impedance of the devices will also have to be compared, as
paddle wheels are much higher impedance than props, better for piston steam
than for high rpm I C engines.
I would have to do the calculations, but I suspect the water propeller on a man
powered (pedalled) device might have the appearance of an air propeller, rather
than a marine propeller due to the low power and high propulsive efficiency
demand. Man is definitely a high impedance animal, so the paddle wheel does
look interesting, here, but other factors enter in, such as the fact that the
man powered machine will cruise at perhaps 1/20 of maximum power capability,
therefore leaving lots of power for planeout, (and also suggesting hydrofoils,
which has been done).
Arguments against the propeller in the way of draft and throughhull penetration
are not valid, as there are propeller driven (SouthEast Asian, usually,
Louisiana "mud" boats) craft that do have shallow draft and no hull
penetrations.
Barry Palmer, for <A
HREF="http://members.aol.com/sevtec/sev/skmr.html">Sevtec</A>
Dan Bollinger
> 1. Is a paddle boat more efficient than a propeller boat?
> 2. If not why aren't there many propeller Pedal boats?
> 3. Is there a minimum propeller rotation speed for satisfactory
> thrust/power output?
No, since a prop works by generating lift. However, faster rpms adds
frictional drag so keep your rpms as low as you can.
> 4. Are there any prop. rotation speed vs. prop. diameter ratios that
give
> the best performance in thrust/power?
Yes. Low rpms. Use prop with a large diameter, high pitch and low disc
area.
>
> As you can see, I'm still keen on the propeller idea, but I need to know
> what limitations, if any, that I may have with pedal power in this regard.
Look for props used by small steam launches. Also, I've head that the large
plastic propellers used by remote control airplanes work well. Dan
neal
Bruce Fountain
> you can access the archives at www.google.com
You should be able to access the thread from here:
http://groups.google.com/groups?q=g:thl704759340d&hl=en&selm=diMg8.76870%24vP.296483%40rwcrnsc51.ops.asp.att.net
Bruce Fountain
William R. Watt
with a big slow prop I think you'd have a lot of sideways force.
a paddle wheel directs all the force straight back.
--
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William R. Watt
alternator or an electic motor backwards to generaate sufficient
electricity to run a trolling motor?
"neal" (nealp...@yahoo.com) writes:
> Re: Have you considered modifing a electric trolling motor for your drive?
>
>
Mark Eckerberg
efficient. You could get a generator around 90% effiecient. I don't
know what the efficiency of a trolling motor is. Probably between 50
and 90% . To get your total efficiency of the energy conversion
multiply the two efficiencies. The small, fast spinning prop, I
believe, would be less efficient than a paddle wheel. This is complex
and expensive in comparison, and most likely slower.
Connecting a paddlewheel to pedals is so simple, and hard to beat for
efficiency.
Conventional paddle boats are very slow, but this is mainly due to the
short stubby hulls. I've heard of smartly designed paddleboats making
6 or 7 knots without getting high tech. Phil Bolger designed a swift
pedal boat to be built in plywood. I forget which book it was in.
On 27 Mar 2002 01:57:31 GMT, ag...@FreeNet.Carleton.CA (William R.
Don Dando
with pedal power even considering a gearing arrangement. The paddle wheel
is direct driven usually which should lessen mechanical losses.
So there you go... an opinion! Let us know how your pedal/prop works out!
Don Dando
"Sam" <dok...@hotmail.com> wrote in message news:3ca0b...@209.128.1.3...
cwg
All high-performance human powered boats use props, not paddlewheels.
Stephen Baker
At the risk of being repetitive, I don't think many are arguing that point.
However, for a first-time builder, the over-the-side paddlewheel set-up with no
holes below the waterline has a certain feel-good aspect to it.
It also explains why most "pond boats" for hire use this system (insurance,
anyone?)
Steve
Dan Bollinger
cost. Or just tradition. Also, as the speed increases props become more
efficient than paddlewheels.
"cwg" <c...@nomailplease.com> wrote in message
news:a7smsr$7e8$1...@laurel.tc.umn.edu...
Jerry
maximum speed for minimum effort and that's several times the efficiency we
can obtain by any other means.
"Ulrich G. Kliegis" <Ulrich....@kiel.netsurf.de> wrote in message
news:j676aukb94m7jdgvh...@4ax.com...
> On Thu, 28 Mar 2002 12:40:07 GMT, "Dan Bollinger"
> <danbol...@insightbb.com> wrote in rec.boats.building:
>
> >There may be other reasons they are used. Weight for one. Manufacturing
> >cost. Or just tradition. Also, as the speed increases props become more
> >efficient than paddlewheels.
> >
>
> Simple question: Why don't fish have propellers? Seriously.
>
> Regards,
>
> U.
>
>
Brent Benson
as does a prop. Paddlewheel use the drag [force parallel to the flow] of a
stalled surface, not at all like fish.
Brent
"Ulrich G. Kliegis" wrote:
> On Thu, 28 Mar 2002 12:40:07 GMT, "Dan Bollinger"
> <danbol...@insightbb.com> wrote in rec.boats.building:
>
> >There may be other reasons they are used. Weight for one. Manufacturing
> >cost. Or just tradition. Also, as the speed increases props become more
> >efficient than paddlewheels.
> >
>
murphy
"Ulrich G. Kliegis" <Ulrich....@kiel.netsurf.de> wrote in
message news:j676aukb94m7jdgvh...@4ax.com...
> <danbol...@insightbb.com> wrote in rec.boats.building:
>
Manufacturing
> >cost. Or just tradition. Also, as the speed increases
props become more
> >efficient than paddlewheels.
> >
>
>
> Regards,
>
> U.
>
But they do. Seriously.
regards
murphy
P.C.
"Ulrich G. Kliegis" <Ulrich....@kiel.netsurf.de> skrev i en meddelelse
news:j676aukb94m7jdgvh...@4ax.com...
> Simple question: Why don't fish have propellers? Seriously.
Proberly difficulties placing the gearbox or and to protect the fishermen .
Anyway here are another paddlewheeler ;
http://d1o111.dk.telia.net/~u139600113/div-2/hjulrob%e5d.jpg
Bet that work as good as a screw fish.
P.C.
Barry Palmer
you imagine blood seals, and nerve commutators?
>Subject: Re: Paddlewheel vs propeller
>From: Ulrich G. Kliegis Ulrich....@kiel.netsurf.de
>Date: 3/28/02 5:39 AM Pacific Standard Time
>Message-id: <j676aukb94m7jdgvh...@4ax.com>
>
>On Thu, 28 Mar 2002 12:40:07 GMT, "Dan Bollinger"
><danbol...@insightbb.com> wrote in rec.boats.building:
>
>>There may be other reasons they are used. Weight for one. Manufacturing
>>cost. Or just tradition. Also, as the speed increases props become more
>>efficient than paddlewheels.
>>
>
>Simple question: Why don't fish have propellers? Seriously.
>
>Regards,
>
>U.
Isaac Kuo
>Man is definitely a high impedance animal, so the paddle wheel does
>look interesting, here, but other factors enter in, such as the fact that the
>man powered machine will cruise at perhaps 1/20 of maximum power capability,
>therefore leaving lots of power for planeout, (and also suggesting hydrofoils,
>which has been done).
How does waterjet propulsion compare? I imagine some sort of bellows
would work better than an impeller due to high impedance/low rpm.
Is that right?
For that matter, how would human powered waterjet propulsion scale
up to something the size of a Greek Trireme?
Isaac Kuo
cwg
"Stephen Baker" <saild...@aol.comnospam> wrote in message
news:20020327110420...@mb-fo.aol.com...
Simple design -- which is why they've been built that way for a long time,
and tradition are the main reasons. Actually, here in Minneapolis, you can
rent HydroBikes (http://www.hydrobikes.com/hydrobike.html) on some of the
city lakes. And resort rental is the company's largest market.
cwg
"Ulrich G. Kliegis" <Ulrich....@kiel.netsurf.de> wrote in message
news:j676aukb94m7jdgvh...@4ax.com...
> On Thu, 28 Mar 2002 12:40:07 GMT, "Dan Bollinger"
> <danbol...@insightbb.com> wrote in rec.boats.building:
>
> >There may be other reasons they are used. Weight for one. Manufacturing
> >cost. Or just tradition. Also, as the speed increases props become more
> >efficient than paddlewheels.
> >
>
frank abbing
cwg wrote:
> "Stephen Baker" <saild...@aol.comnospam> wrote in message
> news:20020327110420...@mb-fo.aol.com...
>>> All high-performance human powered boats use props, not
>>> paddlewheels.
>>
> Simple design -- which is why they've been built that way for a long
> time, and tradition are the main reasons. Actually, here in
> Minneapolis, you can rent HydroBikes
> (http://www.hydrobikes.com/hydrobike.html) on some of the city lakes.
> And resort rental is the company's largest market.
As far as I can see this hydrobike uses a prop.
Frank Abbing
Stephen Baker
>
>Frank Abbing
Sho'nuff, it does, but (and its a big BUT) the shaft does not have to go
through the hull, and therefore is not capable of sinking the boat if the gland
leaks.
Steve
Barry Palmer
>Date: 3/28/02 1:05 PM Pacific Standard Time
>Message-id: <acc26c07.02032...@posting.google.com>
Jet type drives suffer from large internal wetted passage area, and high
velocity, small diameter propulsors, both items resulting in low drive
efficiency. Just look at equivalent (outboard) boats with jet drives as
compared to propellers and you will see the penalties involved, trading
efficiency in the hope that foreign object damage potential is reduced.
Isaac Kuo
>>From: mec...@yahoo.com (Isaac Kuo)
>>How does waterjet propulsion compare? I imagine some sort of bellows
>>would work better than an impeller due to high impedance/low rpm.
>>Is that right?
>Jet type drives suffer from large internal wetted passage area, and high
>velocity, small diameter propulsors, both items resulting in low drive
>efficiency. Just look at equivalent (outboard) boats with jet drives as
>compared to propellers and you will see the penalties involved, trading
>efficiency in the hope that foreign object damage potential is reduced.
I see.
I still wonder what the performance level is like, even if it's not
as good as paddlewheels or propellers.
I imagine something like a pair of bellows, though (one for each
foot, and some simple mechanism to allow pressing down
one bellow to lift the other). There is no small diameter propulsor
involved, but there is still a large internal wetted area.
But how significant is this wetted area? The water only moves fast
near the nozzle. Elsewhere, the water moves slowly so there's less
drag.
Intuitively, I'm thinking that a relatively low nozzle velocity is
desired, implying very large bellows connected to a relatively large
nozzle.
Isaac Kuo
Geodyne
I think, who made lovely traditional construction cedar lapstrake double
paddle canoes. Onto one model he grafted a flexible Plexiglas "fin." The
drive system was quite simple, using foot pedals linked by cable or line to
outriggers on the fin. It apparently moved through the water at speeds
comparable to paddling. I don't remember how it was steered.
"cwg" <c...@nomailplease.com> wrote in message
news:a801ue$5ll$1...@laurel.tc.umn.edu...
Mark Eckerberg
>
out of balance. I think the closest thing to a fish would be a paddle
over the transom like a skulling oar. We used to pump the tiller back
and forth in small sailing dingies when there was no wind and it
seemed to move a little. If the rudder blade was flexible I'm sure it
would move better and that would imitate a fish very closely.
Mark Eckerberg
pedals used to drive it. Just pump with one leg shorter than the
other to turn.
On Fri, 29 Mar 2002 00:25:20 -0500, "Geodyne" <geo...@hotmail.com>
wrote:
Terry K
inefficiency. A properly flopped fin which is a single semi
rotating, variable pitch propellor blade, is the most efficient
type possible. There is only one moving part, and it's
resilience and elasticity contribute toward efficiency by acting
as a spring like storage for energy input. Always a perfect,
self adjusting gear ratio.
Birds use the same system, with refinements, to fly. Our machines
are still not yet so efficient, so cheap, so self maintaining and
self replicating, nor so environmentally benign. Nor will they be
for some time. That design is copyrighted already, and we are
just starting to read the patent.
Terry K
--
Terry K - My email address is MY PROPERTY, and is protected by
copyright legislation. Permission to reproduce it is
specifically denied for mass mailing and unrequested
solicitations. Reproduction or conveyance for any unauthorised
purpose is THEFT and PLAGIARISM. Abuse is Invasion of privacy
and harassment. Abusers will be prosecuted.
cwg
"frank abbing" <fr...@planet.nl> wrote in message
news:whMo8.763827$hy4.27424110@Flipper...
It does. Sorry I wasn't more clear. The question was why rental boats seem
to be paddle, and I was pointing out that not all of them are. Some of the
new ones are prop driven. Rental is now the largest market for new
human-powered prop boats.
Dan Bollinger
where. When the flex of the 'fin' was exactly right, it was suppossed to be
quite efficient. A good, single sculling oar (over the transom) is also
very efficient. Unlike a transverse oar, a sculling oar uses lift to
generate thrust. Dan
"Geodyne" <geo...@hotmail.com> wrote in message
news:tTSo8.8002$je5....@nnrp1.uunet.ca...
John Kohnen
online index, though I think his fin-propelled boat has only been mentioned
in passing:
On Fri, 29 Mar 2002 00:25:20 -0500 "Geodyne" <geo...@hotmail.com> wrote:
> I recall an article in MOIB some years ago about a fellow in New Brunswick,
> I think, who made lovely traditional construction cedar lapstrake double
> paddle canoes. Onto one model he grafted a flexible Plexiglas "fin." The
> drive system was quite simple, using foot pedals linked by cable or line to
> outriggers on the fin. It apparently moved through the water at speeds
> comparable to paddling. I don't remember how it was steered.
> ...
--
John <jko...@boat-links.com>
http://www.boat-links.com/
Distrust any enterprise that requires new clothes.
<Henry David Thoreau>
Geodyne
system. Unfortunately, the MAIB online index is not searchable. I'll have to
do it the old fashioned way -- issue by issue.
"John Kohnen" <jko...@boat-links.com> wrote in message
news:eeVp8wAr...@boat-links.com...
Terry K
drive system. Maybe it was my use of unusual muscles, but I got
to thinking I could do a lot better sculling, or with oars than
with the silly little ventilated paddlewheel. The tiller and
rudder was a huge pain, too.
A good sculling oar or oolau (sp?) is very efficient, as it
approaches that most efficient design, a fish tail, which is like
a modified, articulated, bi-directional auto pich propellor
blade.
A dolphin style vertical flipping tail design sounds very
interesting to me too, given that it could use a long tail
driving bar hinged at the top of the transom.
It would not work in reverse. You would want a small paddle on
board anyway, which you could use to push off a muddy shore or in
case of mechanical failure. It could work with tiller bar style
drive, or pedals, either linear or reciprocating, or railroad
handcar style push bar, or oarlock style drive train. It could as
easily work in the horizontal plane too, now that I think about
it, with the bonus that you could steer with it. The operators
could sit facing each other.
Look into the oolau idea, it is a sculling device using a rope
tied from the oolau handle to a point foreward in the boat. The
operator pulls and pushes sideways on the rope, causing the
sculling oar to change its angle of attack, like a variable pitch
reciprocating propeller blade. It does not coast well, unless
you turn it sideways to use like a rudder for steering, or allow
it to rise above the water while coasting, when it can be
manipulated for steering. A flexible rope hinge retaining the
oolau in a saddle seems the simplest.
You could experiment with a paddle and a scuba flipper glommed
together, tied to the top of the transom just for fun. I would
think about a 30 -40 degree movement 'limp wrist' joint just in
front of the paddle blade, or flipper. Come to think of it, a
flexible fin rudder with a resilient wrist hinge part way back on
the rudder fin blade might do even better.
It would be a first!
Terry K
Sam wrote:
>
> I'm sorry if I'm repeating this thread as I have missed the beginning of an
> earlier discussion on this topic.
>
> My problem is:
> I'm planning to build a small boat, for one or two persons, that uses Pedal
> power. Even though there are usually Paddle-type pedal boats in boat parks I
> suspect it might not be an efficient way of power use. Hence I'm considering
> a propeller type.
>
> My questions are:
> 1. Is a paddle boat more efficient than a propeller boat?
> 2. If not why aren't there many propeller Pedal boats?
> 3. Is there a minimum propeller rotation speed for satisfactory
> thrust/power output?
> 4. Are there any prop. rotation speed vs. prop. diameter ratios that give
> the best performance in thrust/power?
>
> As you can see, I'm still keen on the propeller idea, but I need to know
> what limitations, if any, that I may have with pedal power in this regard.
>
> Your contributions will be highly appreciated.
>
> Sam
--
Dan Bollinger
'fin' and came up with the article:
Fin Powered Launch 12' x 30" / Harry Bryan Feb 15 1995
Does anyone have this article? Dan
"Geodyne" <geo...@hotmail.com> wrote in message
news:GPpp8.8827$je5....@nnrp1.uunet.ca...
Dan Bollinger
meaure of paddlewheel efficiency.
Park boats have terrible hulls, gear ratios, too small a wheel diamater, too
small a wheel width and poor rudders.
"Terry K" <tksp...@nbnet.nb.ca> wrote in message
news:3CA719A1...@nbnet.nb.ca...
Al
> generate thrust.
erm, transverse oars generate lift too. It's quite an important part of
how the blade works. High tech oars for competition rowing can get
quite obsessive about it... the lift properties are also important as
they create a "gap" in the water through which you can retrieve the
blade while minimising drag.
Al
Mark Eckerberg
>Some 15 years ago, they sold such a thing like that here in germany -
>a rubber fin that you could somehow attach to the rudder blade on
>sailing dinghies to get back to harbour when the wind failed. They
>were pretty effective - until the bearings of the rudder shaft tore
>out and broke off in many boats - they were not made for these lateral
>loads.
>
Probably not so much the load as it is the cycles.
Mark Eckerberg
>are still not yet so efficient, so cheap, so self maintaining and
>self replicating, nor so environmentally benign. Nor will they be
>for some time. That design is copyrighted already, and we are
>just starting to read the patent.
>
>Terry K
I saw a show on a science channel about the study of birds for
airplane design. The engineers were saying that they would love to be
able to articulate airfoil shape the way a bird can. Although we can
beat birds on straight line speed, we can't even approach their
manuverabilty, and the way they can retract their wings would be a big
help on a carrier deck or for the planes tethered to the ground in a
storm. The root of their wing is the main airfoil for lift and the
wing tips are the propellers, fanning out into multiple vanes which
are used like sculling oars.
I've heard that the old square riggers were patterned after a duck.
They kind of look like ducks. The boats of the indian ocean were
patterned more like fish. Duck feet are probably not very efficient
water propulsion but this animal has to have design compromises for
its many modes in land, air and sea. I've always been amazed by the
versatility of the comerant (sp?). This animal can go anywhere. It
swims underwater like a seal, floats, flys, walks. Very impressive.
Mark