Pedal Boat Design

Discussion in 'Boat Design' started by BG_Geno, May 28, 2006.

  1. BG_Geno
    Joined: May 2006
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    BG_Geno Senior Member

    Rick--

    I feel for you man.

    Beppe--

    He never said "mono hulls are better then cats in every single way". He states his actual point pretty clearly:

    "A catamaran will require 40% more power to achieve the same speed as a monohull of equal displacement when both are optimized for the same cruising speed at normal level of human power."

    That is simply a fact.

    When you start making statements like "Can you break your hull in two to fit on a car" you invite comments in return like can you go 16km/h? Then suddenly cats are at war with mono hulls rather then just being another design class built for different reasons.

    I think what people resent is that you come into their threads and rather then contributing to w/e the topic is you start pitching your project. Then the argument starts. Not everyone subscribes to the hive mind concept.

    I'll ask that you let this drop and close with an old standard.

    Arguing in forums is a lot like competing in the Special Olympics--even if you win your still retarded.
     
  2. BG_Geno
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    BG_Geno Senior Member

    TTPOOP...I'll bite, what is that?
     
  3. Guest625101138

    Guest625101138 Previous Member

    Taking The Piss Out Of People! Common here.

    Also POETS day is common. That was today.

    Piss Off Early Tomorrow's Saturday (Actually just gone Saturday)

    I am testing a late model engine tomorrow (Jeff) I have to set the boat up for him. He is the current Australian 12 hour distance record holder on land. I think around 500km. He can hold 190W continuously and wants to test out the boat for a 24 hour record on this side of the world after Greg's attempt - could be a while after if Greg does claim it.

    We had an open day on a new freeway here a while back. All the professional upright racers were given the front of the grid and the recumbents gave them about a 5 minute head start and passsed them about 15 minutes in. Jeff was in a fully faired trike that he set the record in. He averaged 55kph for the trip and hit 78kph on the flat. See June story here:
    http://www.trisled.com.au/news.html

    Anyhow off to bed so I can get to the lake in the morning.

    Tomorrow I will hopefully have some video to post on the PPB thread and leave this one to your creations.

    Rick
     
  4. tinhorn
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    tinhorn Senior Member

    So criticisms in this thread of cast iron and oak components MAY have been just a joke? Imagine my relief.
     
  5. BG_Geno
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    BG_Geno Senior Member

    Moving right along.

    I think I am happy with the front down strut now. It's another CF built up structure. The cupped sides are molded in a 2 part compression mold. (Not completely clear in the picture but those are 2 individual sides).

    Those sides are then bonded to a 1/16" thick top and bottom which are formed to shape. The bonded seam leaves a small lip that front and back half rounds (also laid up in a mold) are then bonded to. Thee do add a good bit of strength but are also for aesthetics.

    This structure is then bonded to the saddle on the bottom end and a flange on the top end. the long seams are filled and sanded for clean paint. Also not shown on the assembled shot are fillets on the joints to the saddle and flange. The cross bar is carbon tube with 1" long aluminum inserts bonded inside on the ends which are drilled and tapped for 1/4"-20 that receives bolts on the center through holes on the saddle. I may use two cross bars and mount them on the end through holes.

    Finished weight is 3 to 3.5 pounds. It is a VERY strong and rigid down strut.
     

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  6. BG_Geno
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    BG_Geno Senior Member

    Just a quickie shot to show you where I am headed with the design.

    The down struts will share bolt spacing with the seat brackets so the boat is more configurable. Six inches or so of seat travel for and aft and you can shift the seat forward of the down strut and move the strut aft for very light passengers (like 7 year old grand kids for example). This works in reverse for very large riders where you want to shift the weight aft which is doable because you can swap the seat aft AND move the strut forward. Makes getting accurate loading easy for any size and weight combination for both engines.

    You can move the whole frame fore and aft on the hulls as well. The paddle wheels also have 6" of travel on the Z axis to make sure they are optimum for any weight loading. The rear seat deck section of the frame is raised 6" because my wife is 1 foot shorter then me. "This gives her a bit of stadium seating". It also is just right for the paddle wheels.

    So far I am at about 12 to 12.5 pounds sans nuts and bolts. Thoughts?
     

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  7. BHOFM
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    BHOFM Senior Member

    I did not read this whole thing and this may have been covered
    before.

    Going back to my aviation knowledge, pusher props on aircraft
    are not as efficient because they operate in dirty air off the
    aircraft body, where as tractor props operate in clean air.

    Why does a boat prop have to be in the back? Would your
    flex shaft work if it was pulling the boat?

    I am doodling with a drawing of a 12'x3' sharpie with
    a narrow paddle wheel in the front with the paddles made
    from half sections of 6" PVC, like a spoon. Direct drive push
    rod operated with the ability to raise the wheel for beaching.
    Simple pedals made from pipe extending out the side with
    the boom for the wheel on the same axis.
    Maybe a pull pull with cable rather than a connecting rod?

    Not as a racer, but as a test bed? I have more than enough
    material on hand to build this, and a 70lb test pilot that is
    ready to go!
     
  8. BG_Geno
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    BG_Geno Senior Member

    Being pulled certainly works for dog sleds and wagons =)

    As far as airplanes go, pusher props are more efficient. The arc of a prop is much like a solid disc with the forward aerodynamics of a brick. Because the air is then accelerated back up to speed you then have to pay the piper a second time when your fuse makes the passage. In a pusher configuration the air travels over the much more aerodynamic fuse and you only pay once because the working section of your prop (the outer say 1/3) is all the air "sees".

    The other advantage to a pusher is is the phenomenon called spiraling slipstream which spirals off the prop, around the fuse and strikes the vertical stab/rudder turning the plane slightly. (Gyroscopic progression is another culprit here).

    Anyway, your basically in the same boat (pun intended) here. Parasitic drag (might that be hydrostatic drag with a boat?) over the hull then this travels through your prop. In VERY general terms your only paying once. If you put your prop disc forward you have that blunt surface then the accelerated water plays over the hull.

    Rick would know much better as I am just guessing. I seem to recall an o boy oberto or circus circus hydroplane prototype that tried a pulling prop configuration. Since so little of these boats is in the water at speed (think a few shark fins worth of drag) there is a difference. Obviously it didn't work very well as none of those uber engineered mega fast boats use that configuration today.

    As for scooped paddle wheel blades...I would guess that is exactly what they would do--scoop up lots and lots of watter lol. If I had to bet, I would say flipping them 180 would likely be better. On the other hand, flinging tons of watter into the air would probably tickle your 70 pound test pilot silly =)

    Initially I was pretty skeptical about paddle wheels and favored props. After seeing all the cool patent stuff tinhorn has posted on paddle innovations from the mid 1800's I am hooked. Then I saw that guy in the kayak just smoking fast and I thought...paddles...he is just a pair of paddle wheels sitting there..
     
  9. Village_Idiot
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    Village_Idiot Senior Member

    One reason for having the prop at the stern is that its attitude (angle of attack) is less prone to change, as well as its relationship to the water's surface. As the speed of a boat increases, the bow tends to rise and that could certainly mess with the dynamics of the prop (although this may not be as much of a concern on a PPB).

    I still wonder if there are any efficiencies to be gained by placing shrouds on either side of the paddlewheel so as to not allow water to escape as easily off the sides of the paddles and thereby increase rearward thrust. Perhaps with a given (limited) power, you could have less paddle submerged and get the same thrust, but eliminate the need for feathering. Hey Tinhorn, did anybody play with that type of thing back in the 1880's?
     
  10. beppe
    Joined: Jul 2008
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    beppe Junior Member

    Open Waterbike unintended razzmatazz

    Thank you BG for this answer
    I highly esteem Rick and I rate him as an inventor and fine boat builder. Also, I am amazed in seeing his commitment to help everyone.
    This makes hard to accept his apparent hostility towards the Open Waterbike Project; but I may have mistaken his Australian sense of humor for hostility, as he suggests in his latest post, and I certainly hope so, I enjoy the technical and scientific conversations with him and I believe they can help us all in understanding better the potential of PPBs. By the way, I'm an engineer too, although not a naval engineer.
    Thank you also for your opinion on the Open Waterbike project. Critical points of view are very useful to me. We don't have too much to offer to your project right now, we just started up, but you may be interested in the forward tube connection described here:
    http://www.openwaterbike.com/archit...rbike-drive-unit/the-forward-tube-connection/
    It took a while to adopt this simple kick-up connection, and there is consensus within our small but growing community that this could be a good candidate for the Open Waterbike interface to drive unit. Your opinion about the connection is welcome.
    When I started building my first HP cat, back in the nineties, I would have been glad not to start from scratch, but from some PPB-oriented component; this would have spared me a lot of wasteful work and helped concentrating in implementing my specific ideas, pushing innovation. This is a way of seeing the project.
    Best
    Beppe
     
  11. beppe
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    beppe Junior Member

    Australian humor and Open Waterbikes

    Rick
    well, this could have been just a matter of cultural gap after all. I may have mistook your 'Australian humor' for hostility, and I certainly hope so. I have a number of cousins in Australia, most of them right there in Melbourne; my uncle emigrated to Australia back in the fifties and from him I got a nice collection of Australian boomerangs and I learned how to throw them. Therefore I should have known better, I know that living down under makes some strange effects to your brain ;-)
    You are welcome in challenging my beliefs, I enjoy that and it's very useful; what's important it's that everyone understands the level of communication, the Open Waterbike project is new and fragile right now and could easily be undermined by misundertood opinions of influential people like you.
    I'll be back to 'science' in the next post. I believe intriguing results can emerge comparing your calculated data with our metabolic power recordings.
    I apologize to BG for having misused his thread, I have thought that it was not only for his boat design but more general.
    Have a nice day with your waterbike (oops) Rick, I hope to have an outing tomorrow too and to send a few new photos and videos of the Open Waterbike, prototype 0 - not such an amazing boat right now, but a joy to ride and just the starting point...
    Beppe
     
  12. beppe
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    beppe Junior Member

    Open Waterbike unintended arguing...

    BG
    arguing was unintended, 'breaking the hull in two' was just 'European humor', no offence intended. We really can't transport such a long hull on cars here in Europe and we actually studied the hypothesis of an assembled hull in two pieces.
    I agree with you about arguing in forums, and I happily let this drop and back to more enjoyable technical issues.
    Please, just try to understand that I really believe in the Open Waterbike Project, it's an honest and clear attempt to innovate the world of PPBs (and it needs it! You may not have noticed that, but it's declining) and I have to defend it in this early period, when it is fragile and easy to undermine.
    I apologize for misusing your thread, I thought it was more general, I'll contribute only with more focused issues and hope to give you and all the colleagues my humble contribution.
    Best
    beppe
     
  13. tinhorn
    Joined: Jan 2008
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    tinhorn Senior Member

    I don't recall any shrouded wheels off the top of my head, but there was some experimenting with cupped paddles and various angles and chevron patterns. Some early designers addressed water flow with hull design (including an early tunnel hull combined with almost-NACA inlet).

    Somewhere I got the impression that including small flanges on the outside edges of the paddles would improve their performance. Kind of a shallow, squarish cup. Not sure a round cupped paddle would provide the same effect - they sure weren't very popular among the early designers. Nor were angled paddles.

    I'm prevented from awarding more points, but man, I sure am grateful to the people here who are taking these wheels to the next level.
     

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  14. BG_Geno
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    BG_Geno Senior Member

    No worries Beppe. I will pass along any data I collect though I am not sure how good it will be as my cat doesn't conform at all really to your standards thus far.
     

  15. BG_Geno
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    BG_Geno Senior Member

    Tinhorn.

    I know why they did not go for angled paddles. I have run a bunch of simulations and its always the same. If it helps on the downward portion it hurts on the upward. There may be some shape or profile that would help though

    I am convinced that Rick is right in going with as large a diameter as you can and sticking to that shallow 60 degree range. The down side is all that lateral area in cross winds. The huge weight difference compared to props also hurts.

    One of the reasons they may have preferred the type of paddle and construction is as simple as materials and construction typess available at the time.

    Paddle wheels may not be the most efficient propulsion for larger more powerful boats but I am going to try very hard to see just what they provide for PPB's.
     
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