S2 6.7 Junk Rig Conversion

  • 29 Jun 2021 21:50
    Reply # 10712001 on 6872873

    You’d better look out David, or your family members will have to start locking their things away from you!

    This yoga mat stuff seems to have very useful properties, if it is the same stuff I am thinking of. It appears to be a sheet of polyurethane rubber which, in liquid form (with solvents?) makes an incredibly strong, flexible and resilient glue. I don’t know anything about the chemistry of it, but it appears to be the same stuff which is used industrially to mount big engines on, between the engine and the concrete floor. I’ve not heard of it being used for marine engines, but I did once mount a little single cylinder Volvo Penta on some lumps of the industrial stuff, and as far as I could see it worked OK.

    I once did a Hiab job on a yacht, whose owner told me he had bought (from The Warehouse) a cheap camping ground mat – same stuff as your wife’s yoga mat I think - and used it as a dry bedding for going between his chainplates and the ferrocement hull – bolted down extremely tight and the excess cut off – a quick, easy and cheap job which, on inspection a few years later, proved to have allowed no moisture to penetrate (often a problem with fc in this sort of detail). Its not cheap to buy in its industrial form, but if it’s the same stuff as used domestically it is relatively cheap and its amazing “memory” makes it potentially a material worth considering for a lot of applications besides fendering spars.

    Maybe someone who knows more about these things can enlighten us with a bit more information.

    PS

    Leather, as you used on your boom jaws, is tougher of course. Good old-fashion leather- I read somewhere that the famous Fangio once ran a big-end bearing during a long-distance rally in Argentina - drained the oil and pulled off the sump on the side of the road and replaced the bearing shells with some pieces cut from his leather belt - and completed the race. I guess that toughness, and its ability to carry stiches, makes leather so good for fendering between oars and rowlocks as has been done probably for centuries.

    Last modified: 29 Jun 2021 22:12 | Anonymous member
  • 29 Jun 2021 20:28
    Reply # 10711807 on 6872873

    On the subject of fendering of the yard, boom, and battens; On the new sail on 'Footprints' we cut up my wife's yoga mat into strips and sewed that into the batten pockets, and yard and boom pockets. This seemed to work well, and yes, I did eventually replace the yoga mat.

    But I also came against this issue in a small way on the gaff jaws of my little catamaran. I tried a couple of different types of rubber glued onto the inside of the jaws to provide some cushioning and prevent damage to the paint work on the mast. I was not having much success because whatever I used I seemed to get a lot of friction when raising or lowering the sail. Then I came on some scraps of sheep skin which my daughter had been using in some craftwork. I cut up a strip of that, trimmed back the wooly bits and then glued it on top of the thin bit of rubber already in the jaw. It works really well, no friction, and no damage to the mast. So maybe worth a try for cushioning on a junk rig.

  • 29 Jun 2021 19:06
    Reply # 10711566 on 6872873
    Anonymous member (Administrator)

    Chapter 7, about rigging the sail

    I realise now that a few makers of these sails have run into trouble during rigging it. This was much due to the fact that I was late to write the ‘rigging Chapter’  -  no.7.
    Now I have put a PS at the end of Chapter 5, suggesting reading Chapter 7 before starting on the rigging.

    Arne


    Last modified: 30 Jun 2021 08:40 | Anonymous member (Administrator)
  • 29 Jun 2021 18:18
    Reply # 10711419 on 6872873

    After my short overnight coastal trip I noticed something had been scraping up the mast pretty good. It is inside the red box drawn on the attached photo.

    I think this was caused by the YHP block, which has a stainless steel body, hitting the mast when the sail is squared out on a port tack.

    After reading Arne's instructions again I figured out how to rig the YHP higher up the yard than the sling point. I hope this will prevent more metal-on-metal damage.

    I also added some more appropriate fendering to the yard. I used marine vinyl that was left over from the batten pockets and laced it to the yard.

    Both of these updates are shown in the attached photo.

    I still need to get fendering on the boom. I have the material cut and the holes punched, but the wind was blowing around 12 knots or so when I installed the yard fendering. Now I am waiting for calm weather to coincide with my free time. When that happens I will lace on the the boom fendering.


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    Last modified: 29 Jun 2021 18:18 | Anonymous member
  • 29 Jun 2021 16:48
    Reply # 10711124 on 10647269
    Arne wrote:

    Scott,

    [...]

    • If the batten parrels are slack, the sail will ride at a bit distance from the mast on sb. tack. Then the sail will act as if it has been sheeted harder in, sort of.
    [...]


    Arne,

    Thank you for the suggestions. At the moment the sail acts as if it is sheeted in harder when sailing on a port tack. If the slack parrels can cause the opposite effect then it seems like I have the sheet attached way too far to the port side. I may make some sort of adjustable anchor point this winter so I can fuss with it out on the water next year. For now it is not so bad to mess with the sheet after tacking. It is certainly a lot less trouble than handling a large head sail on a Bermudian rig.

  • 16 Jun 2021 10:46
    Reply # 10647269 on 6872873
    Anonymous member (Administrator)

    Scott,

    I notice the same asymmetry on my Ingeborg. When doing very short tacking up a channel, I leave it as it is, but on longer legs, I may do small corrections from tack to tack.

    Anyway, it is common practice among racing folks to ease the mainsheet a bit as they come about, to speed up acceleration, and then they haul in the sheet, as the speed has been won.

    There are two more noise-factors with respect to symmetric tacking in a JR:

    • ·         If the batten parrels are slack, the sail will ride at a bit distance from the mast on sb. tack. Then the sail will act as if it has been sheeted harder in, sort of.
    • ·         In my waters, at least, the direction of wind and waves is often not the same: On one tack, it feels like heading almost right into the chop, while on the other, the waves are more on the side. I frequently adjust the pointing angle with this in mind.

    I therefore am not too concerned about getting the sheetpoint perfectly “symmetric”.

    Arne


  • 15 Jun 2021 14:16
    Reply # 10641578 on 10602152
    David wrote:

    [...]

    Just a thought about your difference in tack.

    I notice the sheeting point on the transom is more to one side.

    Is it a bit too far to one side, I wonder.

    If you don't adjust your sheet slightly after you tack from starboard to port, I think the sail will be hauled in tighter on port, resulting in more weather helm on port.

    [...]

    Hi David,

    After correcting the more significant problem by adding HK parrels it is clear that the double block for the sheet should be closer to the center of the boat. When starting on a new tack I have to adjust the sheet to make up for this difference.

    I think I will re-work the entire sheeting setup. In addition to getting it positioned properly, I would like to have the sheet block up on a rail and add some sort of hoop to prevent the sheets from grabbing me and/or the tiller!

  • 13 Jun 2021 16:54
    Reply # 10628877 on 6872873
    Anonymous member (Administrator)

    Good, Scott  -
    when everything fails, read the instructions...

    As for that tack line, I recommend using an elastic tack line; one with a stout rubbersnubber on it, as shown on page 6 of this write-up.

    I also recommend fitting one telltale to the leech of every panel. These prevent you from making the standard blunder  -  oversheeting the sail.

    Arne

    Last modified: 13 Jun 2021 21:00 | Anonymous member (Administrator)
  • 13 Jun 2021 15:57
    Reply # 10628655 on 10602260
    Arne wrote:

    Scott,
    after all the hard work you have done to get that rig working, I think both you and the sail deserve to finish the job:

    To get rid of all those diagonal creases, I suggest you fit Hong Kong parrels and a running throat parrel.

    In addition, to stop that lowest leech from fluttering, an elastic tack line, tied to the boom so it looks like a kicking strap, should be fitted. When the sail is fully up, the TL should have some stretch in it.

    Good luck  -  remember that a sail has only been finished when it has been correctly rigged.

    Arne

    PS: Here is how it should look. The HK parrels do most of the job, but by pulling a bit on the THP, the load on the HKPs is much reduced. No bend in the battens.

    PPS:
    The diagonal creases in your sail are not just cosmetic. They remove a good deal of camber, so I think you lose some drive and suffer added drag instead.
    Going upwind and tacking is all about improving the lift to drag ratio.


    You were, of course, absolutely correct Arne. I got it in my head that the creases were just cosmetic. I added HK parrels. The difference in performance is like night and day. I was having too much fun sailing to stop and get a photo, but my sail sets much like the one in your latest reply. I have not missed a tack with the HK parrels rigged.

    It seems I needed to learn the importance of HK parrels on my own. Thank you for explaining to me personally why they are necessary. It is clearly described in your book and write-ups. I should have just done what you said to do! You have been such a great help.

    I am very happy with the sail I made following your design. I will be sure to get a photo, next time, showing the beautiful camber that develops with the HK parrels rigged.

    I am having a little more trouble with the standing tack line. If it is taught enough to pull the boom down when sailing on the wind then it is too short to let the boom swing all the way out when running directly down wind.

    I am also attempting to build a tiller brake following your write up.



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  • 08 Jun 2021 09:12
    Reply # 10604097 on 10601801
    Anonymous member (Administrator)
    Anonymous wrote:

    The video shows me tacking to change from the starboard to port tack. It is much more difficult to 'make' this tack. I have 'missed' and got blown back onto the starboard tack several times. (It seems to happen most often when people on shore can see me). Tacking the other direction is very easy. I have never had a problem.

    I am trying to decide if this is a problem that I can fix, or if this is just the way it is.

    Me too, Scott, and I’ll be interested to hear any solutions?  In light airs the boat (Newbridge Venturer 22 - so a quite heavy bilge keeled) has not got enough momentum to go through the tack, and in a F5 it has some momentum but gets held up by th chop.  And yes, there’s always someone watching! 
       " ...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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