Pedal Powered Boats

[Guest625101138]

Originally Posted by alexlebrit

Dare I say it but isn't one of the reasons the Hobie set-up is so successful the fact that they were in the business for quite a while before they ventured into PPBs, they have an extensive dealer network and have plenty of cash to spend on marketing. Add in the fact the drive's small, easy to use and easy to remove and that once removed the boat is still usable and you end up with a versatile, if not hugely efficient, machine.

Purely from a saleability standpoint it looks to me like Hobie have it just right.

PS, Is it just me or does the Mirage drive in motion remind you of a sea-turtle?

Alex
I am not certain they have utilised an existing distribution network. I think they are into another market segment with these boats now. They may leverage on their old sailing name and network but you see their boats in outdoor/camping stores not just boating.

As far as product goes it sets the benchmark. I simply take issue with their marketing on the basis of efficiency when this is in fact poor to ordinary.

If I made a 2m X 0.8m prop with 1:2 gearing I could pull a rowing 8 backwards in a tug-of-war. Tug-of-wars have little bearing on real world performance unless you are making a tug. Any towing demonstration against paddlers is nonsense from a boat performance perspective. Just a good sales pitch for the gullible.

On the negative side Mirage users get disillusioned when they get beside an ordinary kayak or canoe because they have been mislead to believe they have a performance craft, which it is not.

Rick

[I57]

Originally Posted by Rick Willoughby

Ian
With 3.3:1 reduction you will find it expensive to get a universal joint that will stand up.

I cannot recall the circumstances that you tried the curved shaft but I think it is a better option with the big box. You need a couple of small bearings in the strut to carry the shaft without damage but you could test first without bearings.

10mm machinable aluminium rod with carry the torque and should not be too rubbery.

The inline torque rating of the universal you have is more than enough but once it has a bit of angle the rating drops off. I do not know by how much. Obviously not satisfactory. Greg had the same problem with this universal. I used one with 7.5:1 gearing and it was fine. Angle was about 12 degrees.

I hope to launch V11J on the weekend. Has been a real pain trying to get epoxy to cure in the cold weather.

Rick

Rick

I did try the flexible shaft on an earlier setup and it did work well, very smooth. What didn’t work was the hand drill gear I was using which didn’t last long. This was before I had the involute gear box and after this I was trying drive legs. I am waiting on the delivery of a bigger universal joint and am keeping the current setup. I looked at using a flexible shaft but this would involve major work on the boat, the skeg relocated further aft and a new shaft housing in the hull. I’ve modified this boat so many times now I will only try a new layout if the current one gives me too many problems. Also when I had the flexible shaft the seat had to be raised which is why it had the bigger outriggers (see pic) which made turning harder. Let you know when the boats ready maybe this time I’ll get it right.

Ian Cassell

[Guest625101138]

Originally Posted by I57

Rick

I did try the flexible shaft on an earlier setup and it did work well, very smooth. What didn’t work was the hand drill gear I was using which didn’t last long. This was before I had the involute gear box and after this I was trying drive legs. I am waiting on the delivery of a bigger universal joint and am keeping the current setup. I looked at using a flexible shaft but this would involve major work on the boat, the skeg relocated further aft and a new shaft housing in the hull. I’ve modified this boat so many times now I will only try a new layout if the current one gives me too many problems. Also when I had the flexible shaft the seat had to be raised which is why it had the bigger outriggers (see pic) which made turning harder. Let you know when the boats ready maybe this time I’ll get it right.

Ian Cassell

Ian
You are only on V1.6. I up to something like my 15th boat and I do not bother counting the variations on each boat. I still cannot get the boat right on the first outing. Always teething problems.

Greg did try a universal joint that would stand up but it was about 30mm in diameter with coupling balls. It was strong enough but not as smooth as the curved shaft. He now wants to use a curved shaft on his ocean boat because he likes the action so much. He just told me he did 109km today in 10 hours so is getting close to having a crack at the 24 hour distance record.

I am planning on being at the lake Saturday morning with the new boat. It should be sorted by then. If it is good weather I will hang around for a few hours.

Rick

[beppe]

Dear colleagues
I took the holiday opportunity for reading again 'Human Powered Vehicles', by A.V. Abbott and D.G. Wilson (eds), Human Kinetics, 1995
I found this book (in fact, a collection of papers form different authors) a wonderful comprehensive introduction to HPVs and HPBs, so I recommend it to all the members of this forum serously interested in PPBs builidng.
It has a scientific approach, but no academic heaviness, it reads more like the Scientifica American...
Ther is an extensive body of knowledge about PPBs, and we need to share the basics if we want to go somewere...
One of the shortcomings of the book is that it lacks a single article on high performance kayaks and skisurfs (while there is one on rowing shells and another on hydrofoil, plus a genaral one on hpbs).
Has anybody a suggestion about a good serious source about surfski performance and building?
Beppe

[MLampi]

Hi Rick,

I tried to send these directly to you last week, but perhaps it was to an old e-mail address.

Anyway, here is what the Forerunner recorded for the trip around Shaw Island. Note that there was a very helpful flood current on the west side of the island, and some not-so-helpful currents around most of the rest of the island.

I even did a little wake surfing on the north side of the island.

Michael Lampi

[Guest625101138]

Originally Posted by MLampi

Hi Rick,

I tried to send these directly to you last week, but perhaps it was to an old e-mail address.

Anyway, here is what the Forerunner recorded for the trip around Shaw Island. Note that there was a very helpful flood current on the west side of the island, and some not-so-helpful currents around most of the rest of the island.

I even did a little wake surfing on the north side of the island.

Michael Lampi

Mike
I got the one direct but I was having trouble unzipping it. This one at least has a recognisable compression.

I did some reading on the Forerunner and I think they have updated the software. I believe it will be compatible with the hst format I have but will let you know.

Rick

[Guest625101138]

Mike
Here is Shaw1 data.

Top speed was 15.65kph.

I will send the Excel file direct to you with some explanation.

Rick

[beppe]

Hi everybody
I believe this forum gives us the unique opportunity to assess the relevant performances of some outstanding pedal powered boats, according to the goals set by Rick (... to contribute and provide insight on boating matters at the low power, high efficiency end of the scale.


Maybe we can start from the data Rick himself gave recently

Originally Posted by Rick Willoughby

Beppe
The Hobie Adventure drive achieved 5.3mph with input of 180W to give calculated drive efficiency of 38%.
Same power on the V11 boat gives 8mph with overall drive efficiency of 84%.
...
Rick W

I have a question for Rick and a proposal:
question: is Drive Efficiency the same as 'propelling efficiency', that in literature is defined by the following formula?

Drive Efficiency = Drag * Speed / Wtot

Where
Drag is the Hydrodynamic resistance (passive drag), e.g. the external force necessary to drag the boat at constant speed

and

Wtot is the total mechanical input power


If the formula is correct this would give a drag of 49 N at 3.58 m/s for the V11 and of 29 N at 2.37 m/s for the Adventure. The latter seems rather low, maybe a bit too good, to me. Are these figures in agreement with yours, Rick?

Proposal:

I believe we need some more data to assess the performances of a Pedal Powered Boat, namely drag (at different speeds), length, weight (mass), possibly wetted surface.
I'd like to confront my data with those of other high performance boats, in particular the Cadence, since we agreed that she could be the fastest long distance production boat, the Hobie Adventure, since it's so succesfull, Rick's boats.
I believe these data can really give value to this forum and this thread and help us all improve our PPBs.
I'll give all my own data to all the colleagues interested, just ask me, and also in this forum in following posts.

Beppe

[Guest625101138]

Originally Posted by beppe

Hi everybody
I believe this forum gives us the unique opportunity to assess the relevant performances of some outstanding pedal powered boats, according to the goals set by Rick (... to contribute and provide insight on boating matters at the low power, high efficiency end of the scale.


Maybe we can start from the data Rick himself gave recently


I have a question for Rick and a proposal:
question: is Drive Efficiency the same as 'propelling efficiency', that in literature is defined by the following formula?

Drive Efficiency = Drag * Speed / Wtot

Where
Drag is the Hydrodynamic resistance (passive drag), e.g. the external force necessary to drag the boat at constant speed

and

Wtot is the total mechanical input power


If the formula is correct this would give a drag of 49 N at 3.58 m/s for the V11 and of 29 N at 2.37 m/s for the Adventure. The latter seems rather low, maybe a bit too good, to me. Are these figures in agreement with yours, Rick?

Proposal:

I believe we need some more data to assess the performances of a Pedal Powered Boat, namely drag (at different speeds), length, weight (mass), possibly wetted surface.
I'd like to confront my data with those of other high performance boats, in particular the Cadence, since we agreed that she could be the fastest long distance production boat, the Hobie Adventure, since it's so succesfull, Rick's boats.
I believe these data can really give value to this forum and this thread and help us all improve our PPBs.
I'll give all my own data to all the colleagues interested, just ask me, and also in this forum in following posts.

Beppe

Beppe
Your maths is almost correct. You are inferring all mechanical losses as hull drag which is not quite correct. Particularly with V11. I have 97% mechanical efficiency on V11 so there are some small losses not manifested as drag. Actual main hull drag is 39N at 3.6m/s. There are other components of drag for windage, rudder, prop shaft and outriggers that bring total drag to just over 43N.

At 3.6m/s the Adventure hull has a drag of 82N.

At 2.4m/s the main hull drag on V11 is only 17N. So by this comparison the Hobie hull is not very good even at this relatively low speed.

I expect you are comparing these monohull numbers with your catamaran. It has a 40% power penalty with the concept to start with and then your hulls may not be drag minimised for any particular operating condition. Then you have a large wetted syrface for the drive leg and quite a large rudder. There is also substantially more windage with the high seating position and pilot sitting between the two hulls. These are all substantial components of drag and become more significant relative to the hulls if the hulls are well designed for minimum drag. I expect total weight is greater as well because you need the heavy structure to support the pilot over the water.

Look at the underwater of the Hobie. There is no appendage drag with the drive. All exposed surface is propelling. There is only the rudder adding drag. The pilot sits down in the hull so windage is lower.

I am always interested in useful data but I already have a lot of information on boat performance and can make performance predictions within a few percent.

Rick W

[beppe]

Originally Posted by Rick Willoughby

Beppe
Your maths is almost correct. You are inferring all mechanical losses as hull drag which is not quite correct. Particularly with V11. I have 97% mechanical efficiency on V11 so there are some small losses not manifested as drag. Actual main hull drag is 39N at 3.6m/s. There are other components of drag for windage, rudder, prop shaft and outriggers that bring total drag to just over 43N.

At 3.6m/s the Adventure hull has a drag of 82N.

At 2.4m/s the main hull drag on V11 is only 17N. So by this comparison the Hobie hull is not very good even at this relatively low speed.

I expect you are comparing these monohull numbers with your catamaran. It has a 40% power penalty with the concept to start with and then your hulls may not be drag minimised for any particular operating condition. Then you have a large wetted syrface for the drive leg and quite a large rudder. There is also substantially more windage with the high seating position and pilot sitting between the two hulls. These are all substantial components of drag and become more significant relative to the hulls if the hulls are well designed for minimum drag. I expect total weight is greater as well because you need the heavy structure to support the pilot over the water.

Look at the underwater of the Hobie. There is no appendage drag with the drive. All exposed surface is propelling. There is only the rudder adding drag. The pilot sits down in the hull so windage is lower.

I am always interested in useful data but I already have a lot of information on boat performance and can make performance predictions within a few percent.

Rick W

Rick
forgive me, but my math IS correct, while the terms we used are misaligned.
I believe we should use 'propelling efficiency' (Wd/Wtot) including mechanical losses in the efficiency, and using total drag, not only hull drag, so we can compare different watercraft and also swimming and scuba swimmnig, available in literature. Do you agree?

I believe we need a few other data for the comparison, and in particular total weight (or mass), that is important from a theoretical point of view, and length, that is the most important practical parameter. Could you provide them?

I am not very interested in claiming the excellence of my catamaran, it is just one of the starting points of The Open Waterbike Project (be patient, no better name emerged so far...), but according to your data she is faster and more efficient then the Hobie Adventure, over 2.7 m/s at 180 W (Wtot). But it is nice to know that there is a huge margin of improvement, as the amazing data of your V 11demonstrate.

I look forward to your answer and to sharing data with other colleagues, and in particular with Michael Lampi about the Cadence.

Best
Beppe

[Guest625101138]

Originally Posted by beppe

Rick
forgive me, but my math IS correct, while the terms we used are misaligned.
I believe we should use 'propelling efficiency' (Wd/Wtot) including mechanical losses in the efficiency, and using total drag, not only hull drag, so we can compare different watercraft and also swimming and scuba swimmnig, available in literature. Do you agree?

......
Beppe

No need for my forgiveness you are not doing the sums correctly if you do not isolate the various sources of losses. This allows you to determine the relative merits of each component. Ultimately it is the speed you get for the amount of power input that counts but inferring all losses are hull drag is just silly.

It would be possible to have a very efficient hull with a very inefficient propulsion system. It is then a waste of effort trying to improve the hull because the mechanical losses and the propulsion unit need to be addressed first. It is only through isolating the components of loss that you can address them.

You may find the table that is part way down this web page of interest:
http://www.adventuresofgreg.com/HPB/...6_archive.html
It shows the effort put into isolating, and working to reduce, the various loss components. The power measurements are done using an SRM power crank so within 2%. Greg calibrates before each test run. If you go back through Greg blogs you will see all the aspects that have been evaluated. Most of these things are what I have worked through in the past and have my own data on.

Greg's hull is a copy of V11A. I think he has managed to keep total weight under 20kg although I have not seen the latest weights. He is having the outriggers rebuilt to shave a pound or two.

V11J weighs 23kg. It is 7.2m long and 240mm WL beam.

If you can find the IHPVA archives you will find a good deal of my information posted there over the last few years.

I posted some concrete data on Mike Lampi's Cadence (albiet an overweight one) at the very first post on this thread. Also post #127 above has actual engine and boat data for Mike Lampi's Cadence.

If you post an igs or 3D dxf file of your hull, the hull separation, total displacement and some basic measurements for the drive leg and prop on you boat I will calculate the various components of loss and post them here. You can then compare with the measured data you have. If you like I can give you designs for the optimum hulls for your design displacement and chosen power level. This is always instructive as it shows what potential you have to improve. That said a cat will always require considerably more power than a stabilised monohull.

Rick W.

[Guest625101138]

I got some video of the dipping rudders in operation. WARNING - this is not very spectacular unless you have an interest in such things. I complete a 180 degree turn at about half rudder. Turning radius is around 25m. You can see the rudder dip as it starts to splash. At the end of the turn you can see splashing from the port rudder to provide a bit of course correction. Tightest turning radius is around 10m with the current rudder settings. Very hard to look to see what they are doing so I do not know if they are stalling out when fully immersed but turning seems progressive.

I made a small windlass per attached photo that has sufficient friction to keep the dipped rudder down in position so turning and any course holding can be done almost hands free. With the side mounted prop the boat has a tendency to turn slowly to starboard so I can set the port rudder so it just clips the water to give steady correction.

The boat is now reasonably sorted and I can get back into some engine tuning. I am pleased with the boat so far. Shaving 5kg off the weight makes a big difference for ease of handling. The only disadvantage is the tendency for uplift when on the car top travelling over 80kph. Probably a combination of lower weight and the hull/deck flange.

Rick W.

[beppe]

Rick
I am enthusiastic about your dipping rudders concept; I understand that the idea has been around for years but it i believe is new in the realm of pedal powered boats and just perfect for them.
With just one rotational axis you can eliminate the rudder drag and also have a remote controlled kick-up for shallow waters. Just great.
I am concerned about the maneuverability, but I believe it is possible to work on it, maybe increasing the angle after all the dipping rudder is down and the boat has started turning.
Just a couple of little ideas:
1. maybe the dipping rudders can be installed forward, at the bow of the boat, maybe 20 cm right and left, in order not to disturb the incoming flow to the hull. I believe they can be more efficient working in undisturbed water and is is easier to see and control them.
2. maybe an asymmetrical profile could be better for the rudder, since it works only one way
I would like to present the concept in the Open Waterbike webpage, acknowledging your paternity of course, for development by the community.
With congratulations for the great invention (or re-invention maybe, but this is often the case for grat inventions)
Beppe

[Guest625101138]

Beppe
Forward mounted rudders are not the best. They will roll the boat the wrong way - out of the turn rather than leaning in.

My dipping rudders only achieve full efficiency when fully immersed. They are just water deflectors up to that point like any stern hung rudder.

The idea was first discussed with me some years ago. Maybe Larry Smith suggested it to me. I cannot remember now but the information is clearly in the public domain so no problem using it anywhere.

Rick W.

[beppe]

Originally Posted by Rick Willoughby

No need for my forgiveness you are not doing the sums correctly if you do not isolate the various sources of losses. This allows you to determine the relative merits of each component. Ultimately it is the speed you get for the amount of power input that counts but inferring all losses are hull drag is just silly.

It would be possible to have a very efficient hull with a very inefficient propulsion system. It is then a waste of effort trying to improve the hull because the mechanical losses and the propulsion unit need to be addressed first. It is only through isolating the components of loss that you can address them.
...
Rick W.

Rick
computing the propelling efficiency including total drag and total input power is not uncorret nor silly. It's just a different definition. I agree with you that it is necessary to isolate the components of loss for designing purposes, but a more aggregate concept of efficiency can be better if your aim is comparing. This is what propelling efficiency is about, there are data available in literature for conventional boats that we want to use.
Beppe