Pedal Boat Design

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

  1. clmanges
    Joined: Jul 2008
    Posts: 468
    Likes: 76, Points: 28, Legacy Rep: 32
    Location: Ohio

    clmanges Senior Member

    Rick,
    I also like the V7; nice shape, nice design detail on the hull and the outrigger. I'm curious though . . . I see the gearbox, and the drive shaft seems to enter the water at a very steep angle. Does the prop shaft bend that much? Also, what are those little black sticks poking up from the outrigger and the back of the hull?
     
  2. Guest625101138

    Guest625101138 Previous Member

    The shaft is the extreme variation of my curved spring steel shaft. It is the practical limit for 1/4" spring steel. In this condition it gives about 100km of travel before it fails in fatigue. My aim is to have infinite life so it was a long way short. This was the first time I set up the shaft and I based my curve on peak stress rather than stress range - out by a factor of two. The information I had was not clear on it. The video shows me testing the frame in the garage. The frame has the complete drive set up so is self contained. It can be sat on any hull and away you go. I actually found the prop strut superfluous, which enable use of a longer shaft using same frame.

    The black sticks are tubular vents. They perform two functions. One is to prevent hulls from pressurizing in hot weather. Sitting on a beach, the hull might get over 70C internally. Then there is the risk of dragging in water through a pinhole as the thing cools. Does not really matter with the outrigger because it is not airtight anyhow.

    Rick W
     

    Attached Files:

  3. Guest625101138

    Guest625101138 Previous Member

    Curtis
    To be clear V7 is a slightly modified Pahoa OC1. It was factory built on the Gold Coast. It cost a little over $3000 at the time. It is only glass and weighs 16kg with an glassed-in aluminium mounting plate for the frame to attach to. The boat weighs in at 28kg with current twin outrigger set up so on the heavy side for throwing onto the top of the car. It looks good though but does not excite me like V11J. I look forward to weekends at present so I can build fitness and see what I can do with it. V7 is my tag along boat if I have company.

    Rick W.
     
  4. BG_Geno
    Joined: May 2006
    Posts: 280
    Likes: 2, Points: 0, Legacy Rep: 31
    Location: South Texas

    BG_Geno Senior Member

    The video looks like one of those before shots where the after is an otherwise sensible man is explaining to the ER nurse how he got the gash on his noggin as she stitches it up lol.

    Of course the safety stool is there for emergency egress in the unlikely event of a water landing so all is good.
     
  5. Guest625101138

    Guest625101138 Previous Member

    If nothing else it shows the depth of water required to spin a large prop. I now make them slightly smaller in diameter and gear a little higher.

    Notice I was not wearing cleats. The saw horse was made from leftover timber. It was not my best assembled piece of work.

    Rick
     
  6. BG_Geno
    Joined: May 2006
    Posts: 280
    Likes: 2, Points: 0, Legacy Rep: 31
    Location: South Texas

    BG_Geno Senior Member

    Rick--

    Attached is the modified I beam I am studying, From a construction point of view it is an extremely simple structure to build out in Carbon Fiber. I can lay up the left and right "C" channels to about a 1/16" thickness on a male plug and shove the whole thing into a vac bag and get exceptionally strong, light, and smooth parts with almost no effort. The top and bottom are even easier of course. Bonding the three parts together into the I beam is also very simple because of the flanges.

    The end product also does quite well in down loading (like you would expect of course) and is pretty rigid for axial or torsional loads. Two interesting points. I found that just like sail plane wings, if I bond 1 lb per cu ft white foam in the center channel compression failure strength along the long axis goes up a BUNCH. Like 15%. Lateral load stiffness shows a more modest gain. Torsional or radial loading seems to get a decent boost too.

    The second item is that if I place 1/8" thick webs that span the C's about every 16"-18" radial stiffness shows dramatic gains. This is a lot like the shear webs used between the top and bottom spars on airplane wings--usually the first 3rd of the mains and about the 1st 1/4 on the secondaries. The weird thing is that the ones on the beam run basically opposite of the way they do in a wing.

    For the testing Rick I made up a 3 foot long section of the I beam out of Thornel MAT VMA . I then bonded a carbon steel beam 2" x 3" x 12" to one end and fixed the other end. I then applied pressure to the end of the beam and was able to measure radial deflection. It gives this in degrees but I was able to measure for linear numbers as well.

    With 100 pounds of weight (remember the center of force is 3" up and 12" out the moment arm so it acts as a lever) I got 2 degrees of radial "twist". With the foam in the sandwich and sheer webs about every 12" (2 webs on each side) it took 124 pounds to get the same 2 degrees of rotation. SolidWorks has a way to do actual radial or torsional loading but I can't figure it out.

    That 2 degrees translates out to .38" of down travel 12" out along the moment arm. It is likely a user specific tolerance level but in watching various videos of you and Greg peddling various boats it looks like human mechanics causes about a half inch of side to side sway from just pedaling. Pretty hard not to move SOME in other words. The .38" seems to fall withing that range.

    I don't 100% trust my methodology but even if I double the twist it seems a very rigid structure to me. Particularly as there is no segment of the frame with an unsupported length longer then that 3' range. most segments are supported on both ends as well.

    Seeing the good use you put the flange to on your hulls it also seems having them on the frame would be a boon.

    Sorry for the long winded post guys.
     

    Attached Files:

  7. Guest625101138

    Guest625101138 Previous Member

    BG
    That will be a good section. I had the impression on the original frame drawing that there was a single central web.

    The best way to compare is to look at what works well. The Greenspeed frame is excellent. It is 40mm OD about 1mm wall 4130 chrome/moly steel alloy. The length from seat to crank bottom bracket is about 800mm.

    I would be concerned with 0.38" deflection but I think the loads you are using are high. I need to see a full layout to understand the complete geometry.

    My pedal set up on V11J is marginal. I had to beef up the original design and may redo it after I test the new model engine - much later model and considerably higher power. Greg's is also marginal to get weight down. He does a lot of training on the boat to get used to it. It is quite surprising how small variations gets noticed when you spend time with it.

    Rick W
     
  8. alexlebrit
    Joined: Aug 2006
    Posts: 122
    Likes: 1, Points: 0, Legacy Rep: 16
    Location: France - Bourbriac

    alexlebrit Senior Member

    Here's a thought, why not build a bike trailer and then ride to the lake with your boat behind your bike - could even have a tandem.

    I've seen bikes towing kayaks before, so it's easy done.
     
  9. BG_Geno
    Joined: May 2006
    Posts: 280
    Likes: 2, Points: 0, Legacy Rep: 31
    Location: South Texas

    BG_Geno Senior Member

    Rick--

    The original section DID have the centers in closer so you saw it correctly. A lot of the DIY thing is using construction methods your comfortable with. I am just more at home with composites compared to welded structures, at least for boat building. The loss of temper in Aluminum and other metals from welding makes it necessary (IMHO) to re temper which can be tough on something this big. I think part of it is also a bit like Greg in that if I can't do something perfectly it bugs me, and welding factory perfect joints in aluminum is HARD lol.

    Alex--

    Don't think I haven't considered the bike tow idea. Unfortunately where I live bike riding of any kind is perilous at best. A very large segment of the local population (90% +) is in the group occupying the highest automobile insurance rates.

    Thats the main reason I am building the boat.

    I LOVE my country but the reality is that America is being overrun with immigrants and plain old stupidity. The wife and I discuss moving to Australia at least once a week lol.
     
  10. Guest625101138

    Guest625101138 Previous Member

    BG
    If you like physical activity unencumbered with traffic angst you will love the boat. You may be interested in this link:
    http://web.mac.com/cschaffh/iWeb/HPB/HPB Home.html
    Cory was competent with software. All the timber was CAD/CAM production. He was the first one to point me toward FreeShip. He used it for the hull design.

    He hand fabricated a prop to my spec and wrote it up well. He actually did commute with his boat on occasion. I have not maintained contact but he was a competent builder and extremely detailed. The workmanship is first class.

    I have been contemplating buying a trike as I have a close contact besides Greenspeed who builds them here. They are beautiful machines but they sit so low that you could be meat. I listen to the complaints of car drivers about bikes and especially trikes. We have growing bike use in Australia but the car users really resent them.

    Greg has mastered the art of TIG welding aluminium much better than I have. I have a nice machine but it is an art I am still learning. My hands are not as steady as they used to be. I doubt that reduced strength is a big issue because the stresses are typically low and use is not that frequent.

    I believe shortage of hydrocarbons will have a large impact on recreation in the next decade. To me it was apparent maybe ten years ago and I made a course correction around 5 years ago. My objective was to learn more about hulls for a sailing boat at a decent scale but I have found PPBs very enjoyable and it is an incredibly poorly tapped pursuit. Recreational use of hydrocarbons will be frowned on. F1 will be allowed to use energy recovery system next year so they are beginning to see the light in a far distant tunnel.

    I would be staggered if anyone spending 10 minutes with the V11 type boat did not find it a buzz. There is zero skill required and it is actually easier to cover distance than walking. AND NO TRAFFIC - just a bit of fun burning off the sailing boats. I look forward to Saturday morning so I can get on the water. I am probably hooked on endorphins - sad really.

    Rick W.
     
  11. Village_Idiot
    Joined: Oct 2007
    Posts: 382
    Likes: 14, Points: 18, Legacy Rep: 138
    Location: USA

    Village_Idiot Senior Member

    I had never insinuated that the hull itself had a tracking problem - I apologize if it came across that way. I assumed the hull would track straight before any propulsion was put into application. I simply meant that with one tilted paddlewheel, you might expect some lateral thrust that could lead to slight tracking issues, and that those issues should be nullified by utilizing twin counter-rotating tilted paddlewheels.

    Sorry for the confusion... :confused:
     
  12. clmanges
    Joined: Jul 2008
    Posts: 468
    Likes: 76, Points: 28, Legacy Rep: 32
    Location: Ohio

    clmanges Senior Member

    Okay, well, I would have used a side-wheel setup, and the lateral forces on each side would cancel out, but normally, nothing would be counter-rotating. The wheels on each side would be turning the same direction. The exception to this would be if you wanted to run one forward and one reverse for a hard turn.
     
  13. BG_Geno
    Joined: May 2006
    Posts: 280
    Likes: 2, Points: 0, Legacy Rep: 31
    Location: South Texas

    BG_Geno Senior Member

    Rick--

    That was the first boat I found when I started looking into building a PPB. I was actually searching for stitch and glue information and came across it. Wonder if that's why cats with sexy hulls are stuck n my head?

    That and the 3 years I spent in Barbados as a kid on a Hobbie cat with the tourist girls =)
     
  14. alexlebrit
    Joined: Aug 2006
    Posts: 122
    Likes: 1, Points: 0, Legacy Rep: 16
    Location: France - Bourbriac

    alexlebrit Senior Member

    Just to keep you smiling.

    In one of those slightly random Googlings I stumbled across THIS. It made me smile, so I thought if the maths is getting to heavy take a second to smile too.
     
    1 person likes this.

  15. clmanges
    Joined: Jul 2008
    Posts: 468
    Likes: 76, Points: 28, Legacy Rep: 32
    Location: Ohio

    clmanges Senior Member

    Hey, that's pretty cute!


    . . . the boat's kinda fun, too . . .
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.