Sunfish Sail Question

Discussion in 'Sunfish Talk' started by jflash, Feb 5, 2010.

  1. jflash

    jflash New Member

    Likes Received:
    0
    Trophy Points:
    0
    Hello there, Sailing community!
    Let me start off by saying that I know nothing about either sailing or the sunfish sailboat. I'm trying to design a wind-powered bicycle that has sails, and I'm looking into different types of sails. Can you guys tell me a bit about how a sunfish is different from a regular sailboat?

    I found this picture of how a sailboat's sails can be directed to catch the wind and propagate the boat in any direction. Can you guys tell me if this is the same as how it works for the sail of a sunfish? If not, can you guys use MS Paint and draw on what the sail of a sunfish would do in the picture?

    [​IMG]


    Also, how is the sail of a sunfish moved? Are ropes used, like the sail of a traditional sailboat?


    Thanks in advance for any info, guys! I really appreciate it!

    ~Jonathan Flash
     
  2. fbjru

    fbjru Member

    Likes Received:
    0
    Trophy Points:
    16
    Jonathan,
    Your questions are not really relevant to "sunfish talk", but I will give you an answer the best I can.
    First, you should probably do a little more reading about the physics behind sailing. If you are going to be doing anything with a sail you need to have an understanding of how it will or will not work.

    "I'm trying to design a wind-powered bicycle that has sails"

    I do not believe this will work. You may be able to go dead downwind, but other than that I believe you would quickly tip over.

    Google bloKarts. If you are trying to make something similar this there are online instructions available. However, you would need at the minimum some experience sailing and understanding of how to sail. I've ridden a bloKart and been at speeds over 25mph. There are no breaks, so you need to know how to control it.

    "I found this picture of how a sailboat's sails can be directed to catch the wind and propagate the boat in any direction. Can you guys tell me if this is the same as how it works for the sail of a sunfish?"

    A sunfish sail fundamentally works exactly the same as any other sail. Yes, the diagram you provided is correct, but I think you misinterperted it. You can not sail (propagate?????) in any direction. You can not sail into the wind or up to 45deg to either side of the wind.


    I would not advise your project.
     
  3. Webfoot

    Webfoot New Member

    Likes Received:
    1
    Trophy Points:
    0
    Do a search for "Land Sailor Plans" on Google, I think this is what you are after. There is even a picture of a Sunfish mounted on wheels posted. Best to get some actual sailing experience first, maybe using a Sunfish. This is much less dangerous than trying to learn to sail with a Land Sailor.
     
  4. Wayne

    Wayne Member Emeritus

    Likes Received:
    6
    Trophy Points:
    0
    The Sunfish is a traditional sailboat, if not more so. By that I mean the "Lateen" style sail a Sunfish uses pre-dates the design of the Bermuda rig sailboats people are most familiar with today.




    Land Sailing in different forms has used both designs in the past...




    Sail Bikes today appear to use just about any style, but lean more toward the hybrid sail found on a Sailboard.




    The Sunfish sail is controled by a rope (line), the "main-sheet", visible in this picture.

    [​IMG]


    Some advancement seems to be enveloping Land Sailing.


    [​IMG] [​IMG]



    Here's a bit more realistic chart of where the wind will and will not work for you.

    [​IMG]
     
  5. Fred P

    Fred P Member

    Likes Received:
    2
    Trophy Points:
    18
    jflash,

    Looks like your project is a "been there, done that" effort.
    You'll have more fun on a sail boat than a bike, no matter how the bike is propelled.

    Fred
     
  6. beldar boathead

    beldar boathead Well-Known Member

    Likes Received:
    111
    Trophy Points:
    63
    Your diagram is right. A Sunfish sail is just like your diagram except it has one sail. But if you are building a sailing bike, a Sunfish sail weighs to much, as do similar sized boat sails, like that from a Laser. You need a carbon fiber mast as used on a windsurfer to get a light enough rig. But if you do not know how to sail, you are going to have a heck of a time making some other non-traditional thing like a bike actually go by wind power. BB
     
  7. jflash

    jflash New Member

    Likes Received:
    0
    Trophy Points:
    0
    Well, my design's different from all those above (most of those aren't even bikes). Thanks for the diagrams about wind direction. I'm still gonna go for it and try it out. Anyone got any tips about constructing the lateen sail?


    btw, beldar boathead - thanks for taking me a bit more seriously; I figure something this complex would take several tries to get right, so before i get serious and try to make it out of carbon fiber, I thought i'd try some thick PVC piping for the mast. Think it'll be light enough?
    ...Actually, speaking of weight, wouldn't i want everything to weight a lot more, since a bike doesn't have anything homologous to a sailboat's keel; I'd want a really heavy bike to prevent it from drifting away, right?
     
  8. Fred P

    Fred P Member

    Likes Received:
    2
    Trophy Points:
    18
    You should know that a sail boat has many forces acting on it as a result of the wind against the sail and water against the keel and rudder. How will you counter the heeling (tipping) force on a bike? It will be impossible without at least three wheels. That's why all the above land sailers are not bicycles!
    The pic of a real bike with a sail shows that it will only work when running down wind when there are no heeling forces.
    Your project is doomed from the start if you don't know the basic forces involved.
    Get a sailing instruction book from the library and check out the forces on a boat.

    Fred
     
  9. jflash

    jflash New Member

    Likes Received:
    0
    Trophy Points:
    0
    I've got the forces pretty figured out. It's not too hard. As the rider, I'll be a counterweight for the angled bicycles. Kindof like how a windsurfer....windsurfs
     
  10. Webfoot

    Webfoot New Member

    Likes Received:
    1
    Trophy Points:
    0
    Seem to remember that when you want to turn Left with a bicycle you first lean to the Right. Did a quick search and found this. . .

    http://www.newton.dep.anl.gov/askasci/phy00/phy00255.htm


    I could be wrong but I think a square rig sail with jib is going to be the only option for a bicycle. If it were me I'd ditch the bicycle idea and mess with putting some inline wheels on a actual windsurfer. Personally I think you better wear a helmet and get ready to smack some pavement.:eek:
     
  11. jflash

    jflash New Member

    Likes Received:
    0
    Trophy Points:
    0
    Thanks webfoot. That was actually really helpful. Still goin for it:D, but I did have to make some revisions to my design after reading over that a couple times to see how it'd affect my bike. It seems this will turn out more like a windsurfing bike than a sailboat bike.

    Thenagain, I haven't even built the first prototype. I'm waiting for it to get warmer out (and the ground to soften; I expect to fall a lot) before I start dissecting my mountain bike, so I guess we'll see!:)
     
  12. Wayne

    Wayne Member Emeritus

    Likes Received:
    6
    Trophy Points:
    0
    I think most of the velocipedes in the land sailing examples aren't actual bi-cycles because designers have learned from one another through a hundred odd years of experimenting. What they've learned is lateral stability is a highly desirable characteristic for directionally controlling wind power.

    You can find a lot of DIY sail making information by Googling “Canoe Sails”.

    http://www.summitcadd.com/sailing_canoe.htm
    [​IMG]


    http://www.boat-links.com/Sails/Tortoise.html
    [​IMG]


    What I think you need rather than a heavy bike is a sail size in balance with the lateral resistance you are providing. For example, the 75 sq ft Sunfish sail will drive a 130# boat with a 170# sailor through a heavy medium (water). Take that on land with a 50# bike and a 150# rider and a little gust of wind will likely be able to toss you sideways 50 feet. Ever try and carry a 4x8 (32 sq ft) sheet of plywood alone on a breezy day? Your sail size probably needs to start out around 8 to 10 sq ft.

    Break out the inline skating pads and the helmet, for sure.

    [​IMG]
    http://www.euskalnet.net/kalib

    ... one last thought ... and people have been saying this all along, so I'm going to reinforce it as well. Learning, hands-on, the fundamentals of how a sail harnesses the wind will assist your designing capability immensely, not to mention probably save your test pilot much bruising.
     
  13. jflash

    jflash New Member

    Likes Received:
    0
    Trophy Points:
    0
    haha very true wayne. I guess I do have a bit of experience, as i used to sail some odd years ago, but it wasn't really anything above beginner's sailing (on the charles river).

    To be honest, I realize it's pretty ridiculous to try to control a sail on land without having much of any experience working a sail in the water. Problem is, I'm in New England right now. All the water's frozen over, and even if it wasn't, it's way too cold to go out and learn to work various sails on various boats. Furthermore, I'm pretty much landlocked right now in Western Massachusetts; learning to sail on water is gonna be harder than going out and getting some bruises trying to sail on land.

    PS~ Thanks for those weblinks
     
  14. Wayne

    Wayne Member Emeritus

    Likes Received:
    6
    Trophy Points:
    0
  15. Zeppo

    Zeppo Member

    Likes Received:
    0
    Trophy Points:
    16
    The sail bike will work if your sailing well off the wind (with the wind aft of the beam) but as soon as you attempt to sail at a higher angle heeling forces will rapidly increase. You will not be able to move your weight far enough to windward to counter these forces. The only chance you'll have to stay up will be to steer into the wind or ease out the sail. Hopefully steering quickly into the wind doesn't put you in the path of a starboard tack semi. As said earlier, the vehicle requires at least three wheels (triangular footprint) to be in contact with the road. It's the same principle as a multi hulled sailboat uses for stability, it uses width to compensate for lack of a ballasted keel.
     
  16. Wavedancer

    Wavedancer Upside down? Staff Member

    Likes Received:
    137
    Trophy Points:
    63
    Today I learned from the America's Cup race report that Alinghi pumps water into the flying hull to 'balance' the cat. Now there's an idea to consider for this project...
    :) :) :)
     
  17. Fred P

    Fred P Member

    Likes Received:
    2
    Trophy Points:
    18
    jflash,
    After all this discussion, I hope you tell/show us your results when you finish this project.

    Fred
     
  18. tag

    tag my2fish

    Likes Received:
    91
    Trophy Points:
    28
    Wayne already posted a picture of one of these, but a friend just sent me this link, and I thought I'd share it with you.

    http://www.blokartusa.com/

    [​IMG]
     

Share This Page