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SAIL MAKING MY TAKE ON THE SPLIT RIG SAIL

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  • 02 Oct 2014 17:41
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    Reply # 3114613 on 3095604
    Deleted user

    Hello Ash. the jiblets are all one sail I have posted the dimensions on the technical Illustrations forum.

    The camber I put into the main part of the sail was 6% me thinks this was too little, so the sail I will be making over the winter months will have 10% camber with 6% in the top panel.

    On the starboard tack sailing in the Humber Estuary with the incoming tide I had to use the transom hung  rudder as a paddle to bring the boat around.

    On the port tack I made very little head way, ok to tack with the assistance of the tide.

      
  • 02 Oct 2014 13:01
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    Reply # 3113665 on 3095604
    Deleted user

    Bob,

    Are you able to experiment with individual jiblets, and detach / attach them as individuals. Having made my test sail panels of  polytarp and in the case of SJ made the jiblett as per Slieves design, i am about to make another jiblet getting camber by barrel and darts to stop the draught pulling aft. I would be happy to knock up a jiblet to your overall dimensions and send it up for your assessment.

    How much camber are you getting in the main, and roughly where is the point of max draft?

    Ash

    Last modified: 02 Oct 2014 13:02 | Deleted user
  • 02 Oct 2014 08:07
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    Reply # 3113558 on 3095604
    Anonymous member

    Hi Bob

    The camber in the jibs looks much better. You say it seems to work well, and appears to be pointing well in what are obviously light conditions, and that is what we need. I wonder how flat or older rig designs would preform in these conditions? Hopefully you will see the advantages of the rig, and will feel it was worth the extra effort to make it.

    Cheers, Slieve.


    Last modified: 02 Oct 2014 08:08 | Anonymous member
  • 01 Oct 2014 20:37
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    Reply # 3113299 on 3095604
    Deleted user

    Hi Bob, good pictures.

    The one with the close hauled, wind arrow is  impressive - obviously light airs, was she making way ok and able to tack?

    Ash
  • 01 Oct 2014 15:36
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    Reply # 3112996 on 3095604
    Deleted user

    HAVE POSTED A COUPLE OF PICTURES  IN THE TECHNICAL ILLUSTRATIONS OF THE SECOND MODIFICATION TO THE JIBLETS,I HAVE PUT IN ABOUT 10% CAMBER OF SORTS ALL SEEMED TO WORK WELL .THE ONLY PROBLEM WAS THE WIND, NOT MUCH OF IT ABOUT LAST WEEKEND, WILL BE OUT AGAIN THIS COMING WEEKEND. HAVE DECIDED TO MAKE A NEW SPLIT RIG  SAIL OVER THE WINTER MONTHS FROM 2oz RIP STOP NYLON AND ABOUT 200 sq ft AND JIBLETS AT 28%.

    Bob  
  • 15 Sep 2014 00:12
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    Reply # 3099281 on 3095604
    Anonymous member

    Hi Sleive and Bob, if I may butt in for a moment. I tried adding extra sail via cone-shaped panels in the jib of my AeroJunk. The idea was to get even more drive. It worked after a fashion but I discovered the boat would no longer point upwind as high as before. So everything comes at a price. I have now gone back to my original sail and fitted stoppers that ensure the jib leech cannot go beyond 17 degrees to the batten centre-line. This appears to be the best compromise.

    Best wishes, Paul
  • 14 Sep 2014 08:21
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    Reply # 3098997 on 3095604
    Anonymous member

    Now that is really interesting Bob. 

    My understanding of airflow and how the forces are directed does suggest that even with a simple cone shape you will get a gain over the flat sail, but that it would not be very much without the camber. It may be that more thought should go into 'sheeting angle' in the future. I have been in discussion about increasing sheeting angle in an effort to increase forward drive, but have been nervous about getting too much material in the sail. Maybe I should be more bold?

    Even the flat junk rig goes well off wind and down wind, as the sail is well spread or effectively 'polled out' by the battens, but theory and practice suggests that the split rig gives additional drive with the wind up to about 135° from the bow and it looks as if this is what you're also finding.

    Keep up the good work Bob. My one concern is that it is very difficult to assess any small gains you may (or may not) get with each small change, like adding camber to the jibs. It may be that it will effect pointing angle more, but it can be a mistake to pinch too much and not drive off more. Without expanded scale instruments it is very hard to judge and assess the performance. This is where comparing with other similar boats is so useful.

    Thanks for telling us about your experiences,

    Cheers, Slieve

    PS. You now have me wondering if simply adding an element of 'barrel shape' to the simple cone jib panel might give an adequate camber on a small sail, without the need to use angled shelf foot construction. Something more to think about!

    Last modified: 14 Sep 2014 08:29 | Anonymous member
  • 13 Sep 2014 12:18
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    Reply # 3098632 on 3095604
    Deleted user

    Hello Slieve,  As a sailor on a limited budget the need to create a cheap simple sail that alleviate some of the problems junk sails have with the mast.

    Practical no difference in cost or difficulty between making a flat, cambered or split rig sail, and as I had already made a cambered sail the mast problem was still there.

    As with cutting the jiblet panels in a cone shape this seemed to be a simple and effective method,ok may not have the same drive as a cambered jiblet, but it worked.

    The boat held it own when sailing with a Leisure 23 (230 sq ft) and a Medusa 25 (256 sq ft),knocking the pants off them downwind. When the wind dropped the sails of the other two boat went limp where as  the rip stop nylon jiblets  of mine still drove the boat forward.

    In the next couple of weeks I will make a set of jiblets with about 8/9% camber, and take a weekend sail testing to see what improvement have been made. If ok will make a full set out of rip stop nylon over the winter, will not be able to test as my boat is lifted out in October for the winter.


    Bob 

     

    Last modified: 17 Jan 2015 14:25 | Deleted user
  • 12 Sep 2014 11:08
    Quote
    Reply # 3097600 on 3095604
    Anonymous member

    Hi Robert,

    Thanks for the interesting details, and the pictures in the technical section.

    Looking at the drawing of the jib panels it would seem that you have made them without any inbuilt camber, and more like sections of a cone. If this is the case then I feel you probably won't get the real benefit of having the split rig. By not building a camber into the jibs you will end up with what looks like a split junk but will not get the forward drive and higher lift/ drag that the split junk can provide for sailing up wind. The whole point is to get camber in the first third of the sail, and in clear air in front of the mast. Without a good camber there is little or no point in taking on the extra work and expense.

    So far we have only used angled shelf-foot patterns to get a useful camber and are still looking for other ways to achieve the same effect. The challenge is to get the best shape for the camber. An aeroplane with a bad wing section won't fly, and similarly a boat with a bad sail section (camber) won't fly either, and will stumble along stalled with the poor windward performance for which the junk rig is (in)famous.

    If you want to have a chat about it Robert, just give me a ring.

    Cheers, Slieve.


    Last modified: 12 Sep 2014 11:12 | Anonymous member
  • 11 Sep 2014 14:08
    Quote
    Reply # 3097019 on 3095604
    Deleted user

    I first got interested in making my own sail after viewing an article online in the Duckworks Magazine. This was about putting camber into a junk sail made from a poly tarp. At the time I had a quantity of light weight rip stop nylon so I set about the task of making a sail. Once I had worked out the method the rest was relatively easy,this sail had about 8/9% camber and was a copy of my original flat sail .I use this sail for one season 6/7 months of mainly weekend sailing, it worked quite well sailing closer to the wind and about 1/2 a knot faster. Its main test was a force 4/5 maybe gusting 6, came through well, problem with rip stop nylon is that it does not take abrasion. 

    No sailing over the winter, read David Hardings report in the PBO magazine about Slieve McGalliards split rig on Poppy and also pictures of Amiina. Next job I bought a 8x4 metre white poly tarp and set about working out the size and pattens for the panels. Most of the decisions about measurements and shapes were more intuitive than calculated.

    I do think that having the jiblets at 33% was a little to much, maybe 28%would be a more realistic balance. Slieves query about the battens, I got the size wrong the OD is 25 mm and wall thickness is 3 mm.

    Had the boat out in a force 5 with all the panels up,as I sail single handed it was a bit scary but no bending or problems with the battens.

    Have made a modification to the jiblets I cut out the poly tarp ones and have made new ones from my previous rip stop nylon sail also carried the split through to the top panel.

    Fitted and sailed last weekend no problems does sail close to the wind but best to back off a little, kept pace with a Medusa 25 and a Leisure 23 on a beam reach, and  on a down wind running was noticeable faster.

    The idea behind using rip stop nylon was it would act like a spinnaker in light winds ,at 285 grams for a 6 sq metre sail it is very light weight.

    See new pictures in the Technical Illustration Forum.   

        
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