gmane.culture.transportation.humanpowered.boats

Peter Howard | 2 Aug 19:48

oar+some pedal paddled cataraman

Hi All,

Oar+Some is a boat concept and design project. In essence it is a human
powered (you pedal it), catamaran designed for speed. Think of it as a top
notch, high performance touring bicycle for water.

Computer models, virtual video and discussion here:
http://peterhoward42.blogspot.com/2008/03/oarsome-virtual-photo-album.html

Regards

Pete Howard

Rick Willoughby | 3 Aug 01:04

re: oar+some pedal paddled cataraman

Pete
It is always good to see people trying new things and you have done  
some nice work on the drawings.

Before you get too far into this there are some things you might like  
to follow up on.

Your understanding of the physics that underpins this idea is  
flawed.  You have to consider swept area perpendicular to direction  
of thrust when you compare a paddle with a propeller.  The prop on a  
pedal powered boat is anywhere from 300 to 600mm in diameter, meaning  
large swept area.  Typical velocity ratios are 1.03 to 1.05.  Prop  
efficiencies approach 90% when slip is so low.  Also a good chain/ 
gear drive has an overall mechanical efficiency around 98%.

You may also be interested to know that a minimum drag catamaran  
requires 39% more power than a minimum drag monohull for the same  
displacement.  A countryman of yours put a lot of effort into  
producing a nice product; I believe  without having this fundamental  
understanding:
http://www.rocat.co.uk/
Some owners of the few boats that have been sold have been  
disappointed when they have got alongside more efficient monohulls or  
outriggers.  They have to be much superior rowers to keep up.  The  
business has not built the required volume although it is an  
excellent product.

The most commercially successful, in terms of quantity, pedal powered  
craft is the Hobie Mirage:
http://www.hobiecat.com.au/support/kayaks/miragedrive.html

(Continue reading)

Bob Stuart | 3 Aug 01:29

Re: re: oar+some pedal paddled cataraman

On 2-Aug-08, at 5:05 PM, Rick Willoughby wrote:
<snip>
> So your idea has novelty and probably curiosity value.  I  
> personally feel it will be a difficult action to master.  It will  
> require a lot of muscle retraining as the action does not look  
> natural.  If you sat lower than the paddle pivot it might be more  
> natural.  For certain it will be far less efficient than current  
> methods of propulsion.

Something to be aware of is conservation of momentum.  If the foot  
moves at full speed to the end of the stroke, and then must be  
reversed by muscle power twice and then re-accelerated before  
engaging the drive for each stroke, you waste a lot compared to  
rotary pedals, where the momentum of the leg goes into propulsion.

Best,
Bob Stuart

The more I try to get all my mail answered, the more shows up.

Roger Linke | 3 Aug 02:33

catamarans 40% less efficient than monohulls

[I've never posted before; been reading and enjoying for a few months.]

We often hear that prop (or oar)-driven cats are roughly 40% less efficient than equivalent monohulls, yet
I believe that small sailing cats, like Hobies, are significantly faster than most monohulls of the same
length and with sailplans that look pretty similar to my eye. I appreciate that some speed advantage will
come from flying a hull but they're awfully fast with both hulls in the water too.

Could it be that we just haven't gotten the hulls right yet? Or the power delivery for that matter? 

Roger Linke

--- On Sat, 8/2/08, Rick Willoughby <rickwill@...> wrote:

> From: Rick Willoughby <rickwill@...>
> Subject: [hpv-boats] re: oar+some pedal paddled cataraman
> To: "HPV Boat" <hpv-boats@...>
> Date: Saturday, August 2, 2008, 7:05 PM
> Pete
> It is always good to see people trying new things and you
> have done  
> some nice work on the drawings.
> 
> Before you get too far into this there are some things you
> might like  
> to follow up on.
> 
> Your understanding of the physics that underpins this idea
> is  
> flawed.  You have to consider swept area perpendicular to
> direction

(Continue reading)

Bob Stuart | 3 Aug 02:40

Re: catamarans 40% less efficient than monohulls


On 2-Aug-08, at 6:33 PM, Roger Linke wrote:

> [I've never posted before; been reading and enjoying for a few  
> months.]
>
> We often hear that prop (or oar)-driven cats are roughly 40% less  
> efficient than equivalent monohulls, yet I believe that small  
> sailing cats, like Hobies, are significantly faster than most  
> monohulls of the same length and with sailplans that look pretty  
> similar to my eye. I appreciate that some speed advantage will come  
> from flying a hull but they're awfully fast with both hulls in the  
> water too.
>
> Could it be that we just haven't gotten the hulls right yet? Or the  
> power delivery for that matter?

No, it is a simple area-volume relationship for pure displacement  
hulls.  Sailboats are primarily concerned with providing side force  
and stability.

Best,
Bob Stuart

The more I try to get all my mail answered, the more shows up.

Rick Willoughby | 3 Aug 06:58

re: catamarans 40% less efficient than monohulls

Roger

You have qualified what I stated by applying a length constraint.  I  
stated minimum drag hulls; there was no mention of equal length.  If  
you apply a length constraint then there is a certain speed, above  
which the catamaran will have lower drag than the monohull.  So my  
comparison is based solely on the minimum drag displacement monohull  
versus the minimum drag displacement catamaran without any  
constraints on length.  I am also dealing with power levels possible  
with pedal powered boats; only human power.

Sailing boats are a whole other ball game because, as Bob points out,  
it is the ability to carry sail that counts.

Rick Willoughby

Scott Perkins | 3 Aug 12:19

Re: re: catamarans 40% less efficient than monohulls

This has all been interesting to me as I own a Hydrobike which is
a very well designed upright bicycle powered hpb mounted
on two ten foot pontoons.  It is easy to observe hitting
the "hull speed" at higher levels of exertion and I've
often thought about replacing the existing pontoons
with longer pontoons such as mounting on
ocean kayaks or perhaps two surfboards.

I also bought two perfect airfoil shaped gyrocopter blades of
12 ft length each for potential underwater wing hydrofoil
experiments. (real cheap of course)

Scott

Rick Willoughby wrote:
> Roger
> You have qualified what I stated by applying a length constraint.  I
> stated minimum drag hulls; there was no mention of equal length.  If
> you apply a length constraint then there is a certain speed, above
> which the catamaran will have lower drag than the monohull.  So my
> comparison is based solely on the minimum drag displacement monohull
> versus the minimum drag displacement catamaran without any
> constraints on length.  I am also dealing with power levels possible
> with pedal powered boats; only human power.
> 
> Sailing boats are a whole other ball game because, as Bob points out,
> it is the ability to carry sail that counts.
> 
> Rick Willoughby
>

(Continue reading)

Giuseppe Carignani | 3 Aug 12:36

Re: re: catamarans 40% less efficient than monohulls

Hi everybody
is seems to me that the monohull-multihull dilemma is more complex and
cannot be solved just with a figure, it depends essentially on what is
your goal.
It is also the first question we should address in setting up a open
architecture for a pedal powered human boat, that is what I am up to.
I tried to set up the question here, including some relevant opinions,
starting with Rick's one:

http://www.openwaterbike.com/architecture/the-open-waterbike-architecture/architectural-discussion

I'll try to gather other  relevant opinions there, so they will not be
scattered around the web, preventing everybody to grasp the problem as
a whole, and eventually I hope  to reach some kind of conclusion, at
least for  the Open Pedal Powered Boat
Giuseppe 'Beppe' Carignani

On 8/3/08, Scott Perkins <2scott@...> wrote:
> This has all been interesting to me as I own a Hydrobike which is
> a very well designed upright bicycle powered hpb mounted
> on two ten foot pontoons.  It is easy to observe hitting
> the "hull speed" at higher levels of exertion and I've
> often thought about replacing the existing pontoons
> with longer pontoons such as mounting on
> ocean kayaks or perhaps two surfboards.
>
> I also bought two perfect airfoil shaped gyrocopter blades of
> 12 ft length each for potential underwater wing hydrofoil
> experiments. (real cheap of course)
>

(Continue reading)

Rick Willoughby | 3 Aug 13:39

Re: catamarans 40% less efficient than monohulls

Scott re:

This has all been interesting to me as I own a Hydrobike which is
a very well designed upright bicycle powered hpb mounted
on two ten foot pontoons.  It is easy to observe hitting
the "hull speed" at higher levels of exertion and I've
often thought about replacing the existing pontoons
with longer pontoons such as mounting on
ocean kayaks or perhaps two surfboards.

I also bought two perfect airfoil shaped gyrocopter blades of
12 ft length each for potential underwater wing hydrofoil
experiments. (real cheap of course)

Scott
 >
The choice of hydrofoil or catamaran will depend on the power level  
you want to operate at.  At displacement speed adding foils will just  
add more drag.  If you can generate the sort of power necessary to  
get foil borne then you could do reasonable distance at high speed.   
Say 1000m at 15 to 20kph.

The problem with foils on short cat hulls is that you need to produce  
a lot of power to get the foils up to a useful speed but there is a  
waterbike with short hulls that has done this.  I posted a link  
earlier on to the Halifoil that shows a slow speed hydrofoil using a  
large foil.  I have not actually measured copter blades but if you  
have one 8 to 10 feet wide I expect it would fly you at maybe 3 to 4  
m/s.  You may need to be  pumping out at 500W + to get onto the foils  
but once the hulls lift you could settle back to say 250 to 300W.

(Continue reading)

Alex RIchards | 3 Aug 17:40

Back & Forth vs Rotary motion - of your feet.

A comment in the current conversation about leg motion reminded me of a
question I'd had whilst I was offline in Finland (lovely country, full of
lakes, needs more HPBs though). Someone, was it Rick - it usually is - had a
push-push powered drive system  with cable going from over-mounted
swing-arms to twin clutches on the prop shaft.

Anyway what I wanted was a bit more detail about the length of swing arm
stroke relative to the speed of prop, and the method of fixing the cable
onto the swing-arm. Is it a satisfactory system, or are there compromises?

Alex

Rick Willoughby | 3 Aug 23:58

re: Back & Forth vs Rotary motion - of your feet.


Alex re:<
A comment in the current conversation about leg motion reminded me of a
question I'd had whilst I was offline in Finland (lovely country,  
full of
lakes, needs more HPBs though). Someone, was it Rick - it usually is  
- had a
push-push powered drive system  with cable going from over-mounted
swing-arms to twin clutches on the prop shaft.

Anyway what I wanted was a bit more detail about the length of swing arm
stroke relative to the speed of prop, and the method of fixing the cable
onto the swing-arm. Is it a satisfactory system, or are there  
compromises?

Alex
 >

I was using 3" diameter drums on the clutches.  Warren had his  
underwater so was using 1.5" drums to keep diameter down.

You can work out the rest.  I used about 400mm long swing arms with  
foot pushing pivot at 300mm.  This meant the force in the wire was  
less than the wire.  My foot stroke was about 340mm.  Typically I  
design for prop doing 200 to 300rpm and a cadence ranging from 60 to 80.

I used stainless wire and just wrapped on a nice stainless eye and  
then tied off with stiff wire.

Important things are that you need to keep tension on both wires all

(Continue reading)

Rick Willoughby | 4 Aug 01:45

re: Back & Forth vs Rotary motion - of your feet.

Alex
I have posted some pictures here of Warren's system at #75:
http://boatdesign.net/forums/showthread.php?p=219124#post219124
  Mine is a little simpler but almost identical geometry.  I do not  
have photos at hand.  We did a lot of analysis on the best set up.   
You need to be able to adjust the rest position of the pedals to get  
the best result.  It is a very flexible drive system.  It has an  
extremely natural feel.  You only need to stroke as much as you feel  
comfortable with.  I found I would stroke further when I was going fast.

Rick Willoughby

Alex RIchards | 4 Aug 18:42

Re: re: Back & Forth vs Rotary motion - of your feet.

Rick thanks for that, after a few scetches it all made sense.

I'd wondered about fixing the "drive cables" to the hull aft of the swing
arm and not the swing arm as in your design, and then looping them forward
over pulleys fitted to the swing arms and then back to the drive.

This would mean for every swing-stroke you'd pull twice as much "drive
cable". Yes, the effort needed would be greater, but I wondered if the
potential increase in prop speed, possible decrease in prop size and/or
possible reduction in swing arm length would more than make up for this.

Also can I find roller clutches anywhere in deepest darkest Brittany? Nope
(mind you I don't know what one is in French) so I'm considering using
single speed bike freewheels in their place and running bike chain over
them. In my mind I could see that a single piece of chain could be looped
round one, then over a jockey-wheel and then looped over the second. Yes
there'd be slight twist in the chain, but not a great deal and I think it'd
handle it. Then this would be attached to the "drive cable" using cable eyes
to attach to the chain link pin as in the existing system. And of course it
means no slip and no reeving - hoorah.

Now, I await the potential problems.

Alex

Larry Smith | 3 Aug 19:53

Re: catamarans 40% less efficient than monohulls

[[Oar+Some is a boat concept and design project. In essence it is a human
powered (you pedal it), catamaran designed for speed.]]

[[You may also be interested to know that a minimum drag catamaran 
requires 39% more power than a minimum drag monohull for the same 
displacement.  A countryman of yours put a lot of effort into 
producing a nice product; I believe  without having this fundamental 
understanding: http://www.rocat.co.uk/ ]]

I would have supposed that people capable of the nice job done in 
designing/building the Rocat might indeed have the fundamental 
understanding of the trade-offs, and may have deliberately decided to 
go with the not-insignificant cat-advantage of stability, which can 
be quite important to those whose criteria for pleasurable 
recreational use emphasize something other than high-exertion top-end 
speed.

[[The most commercially successful, in terms of quantity, pedal 
powered craft is the Hobie Mirage:
http://www.hobiecat.com.au/support/kayaks/miragedrive.html
The propulsion is not as efficient as a prop but it is packaged well 
and marketed extremely well.  From an engineering perspective it is 
an elegant design.  Very simple and reasonably well engineered.  It 
shows you do not need high efficiency to market a product but they 
have worked to their strengths and have a lot of happy customers.]]

I would like to attempt to broaden the understanding and use of 
"efficiency", to include elements other than the usual measure of 
speed. Seems to me that the Hobie success indicates that "high 
efficiency" has indeed played a role(s) - high-efficiency of their

(Continue reading)

Larry Smith | 4 Aug 19:08

Re: catamarans 40% less efficient than monohulls

>[[[I've never posted before; been reading and enjoying for a few months.]
>
>
>  I believe that small sailing cats, like Hobies, are significantly 
>faster than most monohulls of the same length and with sailplans 
>that look pretty similar to my eye. I appreciate that some speed 
>advantage will come from flying a hull but they're awfully fast with 
>both hulls in the water too.
>
>Could it be that we just haven't gotten the hulls right yet? Or the 
>power delivery for that matter?
>
>Roger Linke]]

Hi Roger, and welcome! 

A few thoughts : First, let's assume your eye is good, and the 
sail-plans are equal(as well as skipper-skill, etc.). You don't 
mention displacement,...only "same length".

We have to remember that a mono of the same length able to carry the 
same sail-plan IN THE SAME WINDS, will be heavier (greater 
displacement) than the cat,...no question. Additionally, mono-hulls 
are often loaded with more gear/people than "Hobie"-type(trampoline) 
cats (as opposed to "cruising" or cabin cats).

The cat has what is called "form" stability, ...advantageous because 
the form can be, and usually is, very light and thus more easily 
propelled.

(Continue reading)

Peter Howard | 4 Aug 00:35

RE: oar+some pedal paddled cataraman

First of all thanks to everyone for the high quality, well informed and
gracious comments on my (newbie) posting.

I just wish I had appreciated the potential of collaborations such as this
mailing list earlier on! In particular the level of expertise and experience
in the domain of screw/paddle/hull efficiency.

The design goals and constraints for Oar+Some, were (are):

<To aspire to the straight-line efficiency in the water of a racing kayak or
rowing shell. To exploit human leg power, comfort and endurance. To provide
a facing forward sitting position. To be sufficiently stable for non-experts
to use. To have very low power transmission losses.>

I tried to evoke this more naturally as:

<Think of it as a top notch, high performance touring bicycle for water.>

In the cold light of the scrutiny you guys have provided, maybe I should be
more circumspect...

What you have told me about the 40% cataraman efficiency hit, makes it clear
that the emphasis is very much on 'aspire' rather than 'approach' the
performance of a racing shell. The point I was trying to make in my blurb -
to people who had never thought about HPBs, was that Oar+Some was aiming
higher in performance terms than the novelty pedalos you can hire at the
beach. I used the metaphor of a decent touring bicycle, rather than a racing
bicycle delibarately. My mental model involves taking a picnic and admiring
the view - and doesn't involve much puffing and panting

(Continue reading)

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