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Does this camber look OK?

  • 19 Oct 2018 20:25
    Quote
    Reply # 6814576 on 6755485
    Anonymous member

    Well.... Interesting.

    Arne,

       You are right, I probably have stretched the leech by peaking up the yard, as a result the camber probably moved aft....

      The plastic sail was just made so I could find the shape that would work on the boat, see it, find what parrels I need for setting it. Then, stitch up a Polytarp sail.

      Testing the boat with this plastic sail is a good idea. Not stopping now, is a damn good idea!

    Phil, 

       Duct Tape is brilliant. Thinking about it, why not tape the boltrope to the luff and lech? meaning, run thin ropes up luff and leech, tape them to the plastic, screw the battens on both sides, clamping the bolt rope in between and done.....

    Go sailing.....

    Thanks Guys, will test it on some scrap and see how it goes.
  • 19 Oct 2018 16:29
    Quote
    Reply # 6811026 on 6809276
    Anonymous member (Administrator)
    Anonymous wrote:

    I therefore suggest you strengthen your sail with some sort of boltrope. This could be made of webbing or of strips of old sailcloth. The point is to avoid stretching the luff and leech.

    Good luck!

    Arne


    What about using a couple of layers of  heavy dutty wide tape, the kind tthat has a fiber grid pattern running through it such as a quality duct tape? 

    ..sounds like a good idea to me...

    Anything that is cheap, available and good enough would be fine...

    Arne
  • 19 Oct 2018 14:31
    Quote
    Reply # 6809276 on 6783771
    Deleted user

    I therefore suggest you strengthen your sail with some sort of boltrope. This could be made of webbing or of strips of old sailcloth. The point is to avoid stretching the luff and leech.

    Good luck!

    Arne


    What about using a couple of layers of  heavy dutty wide tape, the kind tthat has a fiber grid pattern running through it such as a quality duct tape? 
  • 18 Oct 2018 08:27
    Quote
    Reply # 6783771 on 6755485
    Anonymous member (Administrator)

    Rael,

    Now I have had a look at your sail. According to the aerodynamic gurus, the position of the max camber point is not that critical. My own experience is that the actual centre of pressure, CP, moves forward or aft with the max  camber point, so from that reason, I guess a shunting proa would want a sail with the max camber point well forward. However, don’t let that stop you now. Try it.

    Another thing. The Chinese were happy to use weak stuff for ‘sailcloth’, so your plastic film is fine. However, the Chinese always made their sails with a stout boltrope around it. The boltrope is an essential part of the structure of a Chinese sail, while the sailcloth itself is only there to collect the wind pressure and then transfer the force to the battens. On a cambered panel sail just about all the vertical loads move out to the luff and leech.  In your sail, at best, that will cause the plastic to stretch and deform the camber. At worst, it will rip.

    I therefore suggest you strengthen your sail with some sort of boltrope. This could be made of webbing or of strips of old sailcloth. The point is to avoid stretching the luff and leech.

    Good luck!

    Arne


    Last modified: 18 Oct 2018 12:41 | Anonymous member (Administrator)
  • 18 Oct 2018 06:38
    Quote
    Reply # 6782407 on 6755485
    Anonymous member

    Robert,

     True you cant see camber depth, but the creases in the plastic show camber position. A narrow section of the luff if flat, then start the creases in the plastic that go towards the leech, They end quite a way before the leech.

      The creased area is clearly oriented towards the front of the sail, it's center, max camber depth was ahead of mid chord.

      What I really wanted to know is how well does a sail work when camber is so far aft?

    Thanks.
  • 17 Oct 2018 19:00
    Quote
    Reply # 6772825 on 6755485
    Deleted user
    Anonymous wrote:

    I plan on making the real thing finally, I do think adding a bit of depth (6%) will help, this is not going to be a very fast proa, though I don't think it's going to be slow ether.

    The top panel is flat, the second should have 3% (I didn't measure it, so may be less). The bottom 3 turned out to have 5%

    Hi Rael--I found it hard to see the camber perhaps 'cause the material is transparent? Perhaps draw some quick and dirty black lines (magic marker) along the seams...can't see the seams.

    rself

    PS-Without wind filling the panel it is hard (for me) to make an evaluation. However, these are (minor?) details. You more-or-less have an enlarged windsurfer. The vessel will be fast in smooth water.

    Last modified: 17 Oct 2018 19:13 | Deleted user
  • 16 Oct 2018 19:57
    Quote
    Message # 6755485
    Anonymous member

    In the clip below at 4:22 minutes you can see the whole sail.

    I measured the camber of this full size model, and at first I didn't like it, as I said in the vid. I expected it to be further ahead and deeper..... maybe I was expecting too much...

    Now I have second thoughts, because it is ahead of mid chord and at 4:22 when I pause the vid it looks o.k. I think....

    I plan on making the real thing finally, I do think adding a bit of depth (6%) will help, this is not going to be a very fast proa, though I don't think it's going to be slow ether.

    The top panel is flat, the second should have 3% (I didn't measure it, so may be less). The bottom 3 turned out to have 5%

    The creases in the sail show the camber, should I attempt to move it forward?

    Did I get anything else wrong? If so, now is the time to know about it... 

    https://youtu.be/cm9ZDicRZck

    Thanks for any input. 

    All the best.

    Rael 
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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