Small improvement of Aerojunk rig

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  • 23 May 2025 12:18
    Reply # 13502542 on 13496653

    Devo as you could read in my previous post, I was wingling between the 4 mm outhoul starting at top or bottom.

    I see you think we need the 4 mm to go down all the way to the cockpit.

    But my idea was to connect the 4 mm at the top to the one line sheet which is already there. The sheet has already an automatic pull tension created by the wind force on the whole sail.

    So the sheet pulls the 4 mm. My spreadsheet was only dealing with a linear power over all the blocks, which of course is not the truth. Part of the overall friction is less on the top for so to increase lower down. But there again the sail area is a bit bigger, maybe balancing out the differences.

    The spreadsheet shows there is abundance of spare power to pull the camber flatter when the wind force increases. But now the trick. How much does the system have to pull each grommet to make the perfect camber for each wind force?

    The bungees was also in my mind, but I am afraid we end up again with an approx. Maybe we should think about different friction for each grommet according the camber we want?


    Last modified: 23 May 2025 12:46 | Anonymous member
  • 23 May 2025 02:49
    Reply # 13502476 on 13496653

    Another alternative (better?) is the run the 4mm sheet from top down, instead of bottom up. 

    Scenario: wind picks up, you pull the 4mm sheet to flatten all battens/panels. Wind dies down a little; release the 4mm sheet a little, and the bottom panels gets camber first, while the top panels remain flat. Once the winds dies to light winds,  release the 4mm sheet completely.

    Certainly, experimentation is needed; maybe releasing the 4mm line a little, causes all the battens to equalize, and all the panels are midway flat. I suppose, one can put different strength bungees according to top or middle or bottom battens.

    Doing it this way, there is little weight of the 4mm line from the boom to your cleat point. You don't need as long as a line, and you don't have a long  line from the top batten to somewhere at your deck.

    Whereas, original way, if you run the 4mm line to the top most batten, that ~10m (mast height dependent) of 4mm weight is "adding" to the friction (of the top batten block) you are trying to counteract. 

    Last modified: 23 May 2025 03:12 | Anonymous member
  • 23 May 2025 02:21
    Reply # 13502471 on 13496653

    If the friction of the small blocks cause the sail to stay flat, then use a bungee to pull the opposite direction to get camber on the sail.

    1. Uncleat 4mm line to let leech relax 

    2. The bungee pulls the leech toward luff

    3. The top most panel will get camber and slowly works its way down to the boom.

    disclaimer: I haven't tried this yet. Some experiment must be done to figure out the friction per batten, the weight of the 4mm sheet, from yard to bottom cleating point, the pull force of each bungee, ... etc.

    I am in the process of redoing all my sails to a luff pocket aerojunk rig (aka wing'soul). As all junks, its has superb reefing and twist management abilities. Add performance increases of the slot affect (from the mini-jibs), and the low turbulence of luff pocketing the mast... should be an outstanding rig. 

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    Last modified: 23 May 2025 02:57 | Anonymous member
  • 16 May 2025 11:17
    Reply # 13499884 on 13496653

    Paul, the spreadsheet shows that the friction has been overcome.

    There is enough surplus power left to reduce the camber.  

  • 15 May 2025 13:06
    Reply # 13499433 on 13496653

    Hi Nic,

    I would also be in doubt whether the friction could be overcome... However, there is no better way than to build and test it! ;-)

    Cheers,

    Paul

  • 15 May 2025 09:11
    Reply # 13499396 on 13496653

    OK, did go through all calculations.

    Changed and redefined a few cells and the result convinced  me that it is indeed doable.

    Any arguments against, with calculated explanation is welcome.

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    Last modified: 15 May 2025 09:12 | Anonymous member
  • 11 May 2025 11:49
    Reply # 13497808 on 13496653

    Hmm, forgot the Jib, which means that the tension on the sheet would be 25% less?

  • 11 May 2025 04:21
    Reply # 13497787 on 13496653

    I did make a spreadsheet with a calculation of the pull force on the outhaul arrangement. I only need a sane approximately value for resistance.

    Any ideas?


    Edit

    I found some factor on the internet and implemented it in the spreadsheet.

    It shows that my original idea does nor work, but starting from the top and attaching it to the sheet in the bottom would probably go?

    That seems to be wrong thinking.

    Last modified: 15 May 2025 09:12 | Anonymous member
  • 09 May 2025 16:27
    Reply # 13497288 on 13497270
    Anonymous wrote:

    I think you will find your idea will suffer from friction with all the blocks but if you want to try it then please go ahead. 

    Hi Paul,

    yes I was considering that too, but we need first to establish a number for how much force would be needed to pull the system, then.assume a factor of resistance for the blocks (nylon would help). If the tension of the sheet would be showing to be to little, it could be solved by a multiple-part pull system like we do with halyards and sheets.

    Can you estimate how much pull force would be required per grommet?

  • 09 May 2025 16:02
    Reply # 13497270 on 13496653

    Hi Nic, yours is an interesting idea. I did think of ways to flatten or deepen the camber but in the end designed the sail for an ‘average’ wind. 

    I think you will find your idea will suffer from friction with all the blocks but if you want to try it then please go ahead. 

    Paul

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