Double Sheeting

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  • 15 Jul 2018 21:28
    Reply # 6382178 on 6127132

    I have the same rig on my Colvin Doxy. the problem is that if you go to a single sheet it has to go to a block well aft of the leech of your sail. There is not enough room between the leech of foresail and the mainmast to put a single sheet far enough aft from the leach of the fore to be effective. having said that, having two sheets on the foresail is rarely a problem- they dont foul if you run them FORWARD (towards the foremast on the cabin roof) and can be set to be self tacking.

    On the mainsail the leech is well over the transom and there is no hardpoint far enough aft to mount a single sheet. SO  spahhetti in the cockpit. you get used to it. also its handy having two sheets when one side breaks. I added a bimini cover and the euphroes stopped hitting me in the head. I think one serious advantage to the gazelle is the center cockpit. :)

    i think the last time i posted about this i was much more frustrated. i guess i have come to terms with the 2 sheet compromise for how well theboat sails menouvers and balances.

    margaret drummer

    colvin doxy 38'


  • 17 Jun 2018 12:50
    Reply # 6316901 on 6147025
    Scott Dufour wrote: Hey Eric,

    Referencing Sleive's files, I have to ask the question:

    Doesn't your approach - at least in step 1 - put the curve at exactly the wrong spot?  The aft section of the sail is usually kept as flat as possible because a hook in that area contributes mostly drag.  It's camber in the forward 1/3 that makes the lift to windward.

    Michael - are your forward sheets constantly getting hung up on something?

    Bonjour Scott

    Sorry I missed that answer.

    The idea is not to add some camber at the rear but to limit the camber at the rear when the wind is increasing. It allows more flexible battens in light airs. I'm convinced that, while efficient, rigids battens are contradiction to the natural adaptative flexibility of junk rig.

    The main issue I (re)found is that you can't have flexible battens on the forward part of the sail. It leads to "S bending" (PJR fig 1.8) (I tried and it is not confortable). At best, with a flat sail, with a rigidified fisrt third forward batten, you optain a flat entry (where you would like to have camber), a cambered middle third (similar bu smoother to articulated battens) and a rather flat third rear area (which is good). It's far from optimum. It may be improved by a forward barrel-cut for example.

    But the flat sail is not the point. The point is the junkwing ; with a thick rigid profile (build up out of flexible battens maintained by a limited structure), around the mast, on the first two thirds of the batten and a lambda sheeting at the end of the wishbone part and at the rear in order to use the rear third of the sail to provide the profile camber.

    I tried it on the demonstator, in light wind, and it worked very well.

    I tried it on the ground in heavy wind (25-30 kts gusting) and the very light build sail was not too bumpy and resisted well.

    The next step will be to build a sail for Mingming and try it at sea....

    Eric




  • 17 Jun 2018 07:14
    Reply # 6316777 on 6316749
    Bill F. wrote:

    noob question here, would adding a gurney flap to a fanned sail simplify passing the sheets over when tacking? 

    Bill

    I think we've discussed Gurney flaps, a while ago now, but they're really not what we're wanting, in a rig that's to sail to windward. They give a little extra lift, at the expense of a lot more drag. I'd set that thought aside.
  • 17 Jun 2018 04:28
    Reply # 6316749 on 6127132

    noob question here, would adding a gurney flap to a fanned sail simplify passing the sheets over when tacking? 


    I've occasionally wondered if i could use one of those dog leashes that automatically wind in the leash to keep the tail end of the sheet rope up and out of the way. I suppose salt water would destroy them though.


    Bill

    Last modified: 17 Jun 2018 05:50 | Anonymous member
  • 14 May 2018 01:35
    Reply # 6152979 on 6127132

    Thanks Lynda, I will look up the book... Cutting the Dragon's Tail 

    I appreciate the response.

  • 13 May 2018 16:12
    Reply # 6152111 on 6127132
    Anonymous member (Administrator)

    I have double sheeting on my 20 foot cruising boat, and I like it quite a lot. It keeps the cockpit clear of the mainsail sheets, and makes for much easier backwinding of the mizzen. I would honestly hate to give it up, though I do understand your concerns about lots of lines. Such trade-offs!

    Shemaya

    Last modified: 13 May 2018 16:17 | Anonymous member (Administrator)
  • 13 May 2018 12:56
    Reply # 6151742 on 6127132
    Anonymous member (Administrator)
    Michael Young wrote:

    Hi Everyone, 

    I have a Tom Colvin Gazelle. Both the main and the foresail are double sheeted meaning a sheet set on the port side and another on the starboard side. I am wanting to change this to a single sheeting in the center. Any reason why this shouldn’t be done?

    Hi Michael,

    David and I had a three masted Colvin boat and we also had double sheets.  While we changed the 'more traditional' aspects of Colvin's rigging plan,  we stuck with the double sheeting system which we found to be absolutely brilliant in many ways.   If you go to the library,  and look for the PDf of our book,  Cutting the Dragon's Tail,  you will find David's diagrams and text dealing with the whys and wherefores of the changes we made and our decision to keep the double sheeting system.    We now have a much smaller boat where,  unfortunately, we cannot have a double sheeting system,  but it would be nice if we could . . .   Lynda

    Last modified: 13 May 2018 13:07 | Anonymous member (Administrator)
  • 10 May 2018 15:23
    Reply # 6147025 on 6139966
    Eric Andlauer wrote:
    Michael Young wrote:

     Any thoughts?

    Bonjour

    On Mingming, on a slow process, i'm experimenting what I called Lambda sheeting. The iidea is to have a two sheeting points on the batten one at the aft end and the other about one therd of the batten length forward.low tec- low cost-wingsail demonstrator

    With a flexible (aft part) batten it allow to have a curved profile with a flat sail.

    It's a two step experimentation, the lambda sheeting is limited, as such, on a "flat saile" as the forward part of the sail (the most important) must remain flat to prevent "S-bending". It could be used, for example, in conjonction with a forward barel cut sail and flexible rear battens.

    the second stage of the experimentation deals with a junkwing with a profile on the forward part of the sail and a flap at the rear. Then the lambda sheeting would allow a flexible junkwing.

    With a lambda sheeting, the sheets are separated by the sail and are less messy than if both sheetings are linked to the leach.

    Eric


    Hey Eric,

    Referencing Sleive's files, I have to ask the question:

    Doesn't your approach - at least in step 1 - put the curve at exactly the wrong spot?  The aft section of the sail is usually kept as flat as possible because a hook in that area contributes mostly drag.  It's camber in the forward 1/3 that makes the lift to windward.

    Michael - are your forward sheets constantly getting hung up on something?

    Last modified: 10 May 2018 15:28 | Anonymous member
  • 06 May 2018 22:24
    Reply # 6139966 on 6137238
    Michael Young wrote:

     Any thoughts?

    Bonjour

    On Mingming, on a slow process, i'm experimenting what I called Lambda sheeting. The iidea is to have a two sheeting points on the batten one at the aft end and the other about one therd of the batten length forward.low tec- low cost-wingsail demonstrator

    With a flexible (aft part) batten it allow to have a curved profile with a flat sail.

    It's a two step experimentation, the lambda sheeting is limited, as such, on a "flat saile" as the forward part of the sail (the most important) must remain flat to prevent "S-bending". It could be used, for example, in conjonction with a forward barel cut sail and flexible rear battens.

    the second stage of the experimentation deals with a junkwing with a profile on the forward part of the sail and a flap at the rear. Then the lambda sheeting would allow a flexible junkwing.

    With a lambda sheeting, the sheets are separated by the sail and are less messy than if both sheetings are linked to the leach.

    Eric


    Last modified: 06 May 2018 22:27 | Anonymous member
  • 05 May 2018 16:59
    Reply # 6137238 on 6127132

    I agree that there is enough spagetti on deck without adding a whole additional set. So I am looking at reducing it to a single. I see the longer batten I think Arne does. Maybe this would make it feasible. If I can’t ... I might go to a gaff foresail. One advantage to that would be educational for the scouts who charter the boat. Any thoughts?

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