Polytarp lugsail 3D shaping

Discussion in 'Sailboats' started by laukejas, Jan 15, 2015.

  1. The Q
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    The Q Senior Member

    Quote ..Well, you make it sound like I should just make a quick and dirty sail for testing and improving my skills, so that I can soon switch to a "real" sail. But you see, the problem is that I'm unlikely to ever get a real sailcloth. I searched and searched, and it is simply not available. Either I ship from US and pay twice for shipping, or start my own sailcloth manufacture... Quote

    Since you are in Lithuania and therefore the EU, I would suggest you could get sailcloth from the UK, Germany, Denmark OR France with only delivery charges no import duties ( Try Ebay.co.uk etc), you could also look at buying a second hand sail from one of those countries and modifying to fit.

    I myself am planning to make a temporary sail from Monotex Tarpaulin while I get the general position of mast, keel and rudder right for my home design 16ft keelboat.
     
  2. SukiSolo
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    SukiSolo Senior Member

    Nice one ch3oh! That looks very sweet, hope it works well for you. Thanks for posting that.
     
  3. Pericles
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    Pericles Senior Member

  4. laukejas
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    laukejas Senior Member

    I haven't, but I heard nylon is often used as a material for downwind sails because it is stronger than polyester, also stretchier (not too important for downwind sails, sometimes even desired).

    If it is used for raincoats, it should be somewhat water proof. Hence, although probably not air-tight, it should be impervious enough to work as a sail. Press a piece of it against your lips - can you breathe through it? If not, or with difficulty, it should make a fine sail.

    I don't have experience with it, so don't take my word for granted, but it sounds like a perfect material for a spinnaker.


    Okay, I'll try. But as far as I remember, everything costs a lot more in UK.
     
  5. Pericles
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    Pericles Senior Member

  6. laukejas
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    laukejas Senior Member

    I have made a sail from Tarpaulin last summer. Good material. Stretchy, but survived a storm.

    Well, Eurozone hasn't exactly evened the prices between countries. Average salary in UK is around 4 times that of ours, and so are everyday expenses. Not good news if you're ordering from UK. Apart from that, things got a little better, but I couldn't say our government knows how to make the best of the resources and funds EU gives us.
     
  7. Petros
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    Petros Senior Member

    You are incorrect; the latex is not there to add strength, the strength comes from the fabric. the idea is to seal the fabric and give it smoother finish to improve performance. all sail cloth have similar coatings for this purpose and why it costs more than similar plain polyester fabric. The melamine coating on performance sail cloth is there to seal the fabric, give it a smooth finish, and stabilize the fibers to help it retain its shape. Latex should do the same thing at less cost.

    Thinning the latex should not add much weight to the fabric, the only disadvantage the latex has it is not as abrasion resistant as the sail cloth coatings, but than it is not too difficult to touch up the paint coating when necessary.
     
  8. Pericles
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    Pericles Senior Member

    Hey Petros,

    Where you been? It's sorted. No latex, no stretch, clear, fully waterproof, UV stability & weighs only 9.6 kilograms for 4 metres x 12 metres.

    http://www.icopal.co.uk/Products/Pro...Tarpaulin.aspx

    laukejas,

    I don't think your tarpaulin was the same as the Incopal clear tarpaulin.

    As for governments & politicians, ours are far worse in the UK., On 7th May we have our general election & nearly half the voters want to leave the EU, but our politicians, representing 6 political parties have no intention of permitting a BREXIT. They'll try anything including taking http://www.eureferendum.com/ off line.

    At least Iceland had the sense to keep their currency & independence.

    http://en.wikipedia.org/wiki/Accession_of_Iceland_to_the_European_Union
     
  9. Skyak
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    Skyak Senior Member

    This stuff looks great! I love that it is transparent because I like to seal off against the deck and need visibility. 160gsm is not too bad and I read that the strength is 700N/50mm or ~75lb/inch. If I am reading right the reinforcement is PET polyester so the stretch characteristics would be proportional to the strength -maybe a little stiffer because the warp angle is so much smaller than woven. Since it is outdoor construction material I am sure they don't spare the UV protection. LDPE can be welded but I an not sure of the overlap you would need for full strength and stiffness.
     
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  10. ch3oh
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    ch3oh Junior Member

    There are still assets this tarp is lacking. The most obivious thing being complete lack of cross fibers. As discussed, dacron is tightly resin-bound to cope with these forces among other reasons and there's ALWAYS at least 3 fibre orientations in mylar clear sail laminates. For a reason. Also, in close inspection monarflex's lengthwise fibers are bound from 2 bunches around straight 90deg fibers. So it has slightly more stretch longitudally. I'm thinking adding some fibers (maybe pulling strands off a dyneema rope) with a clear tape might help.
     
  11. Pericles
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    Pericles Senior Member

    ch3oh

    Boat design is about compromise. Icopal is not a sail making cloth, but beggars cant be choosers when the Devil drives. It will stand up to gale force winds on scaffolding. If it stretched too much, it would start banging against the poles & draw the ire of sleeping citizens. For a lug sail who cares if it's all baggy cringles; for a leg o' mutton, cut it diagonally & sail away. :D
     
  12. BATAAN
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    BATAAN Senior Member

    Some years ago a Sausalito sailmaker, David Westwood, showed me his secret to getting an excellent set in his dacron lug sails and it was a dart at the throat. His sails really were excellent and I wish he was still in business. Originally from England and trained there in the trade.
     
  13. bjn
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    bjn Senior Member

    Wow, nice sail. Did you make it yourself?
    Have you tried putting it on the boat?
     

  14. ch3oh
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    ch3oh Junior Member

    I made it myself from ground up. Even the batten pocket end plates are diy. I have test fitted it on mast tube and boom, but the cat isn't even remotely ready to hit water. Maybe later this summer.. Now that the fore triangle measurements are final, I should really do a jib too. It will be a small self-tacking one featuring a luff pocket with zipper and maybe 3-4 full battens.
     
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