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Sailmaking detail questions

  • 13 Mar 2013 08:14
    Quote
    Reply # 1241347 on 1238226
    Anonymous member
    Hi Daniel,

    If I read your Ps, Us and Bs correctly, you have only one batten ending near the yard at the throat, as in mehitabel's sails. And all battens are the same length. Both right?

    And you've raised the angle of the four battens under the yard and left the bottom 3 parallel. Evidently.

    You only mention one value for P, so your panels are all the same height at the luff. Yes?

    mehitabel has her P varying up the luff (from the bottom: P-~2"; P; P+~2"; P+U; P+U; U at the yard.) 
    - It's so that reefs are smallest to begin with, 'balancing reefs' as I mentioned in the article...
    - And so that we can use 3-point sheet spans without raising the whole sail farther off the deck to provide the necessary sheet drift, Dmin.

    So your sails differ from mehitabel's in these ways:
    - higher aspect ratio
    - one batten more
    - incorporating more 'fanning' of the upper spars
    - P at luff same for all panels.
    Does that seem correct?

    Forgive me for reminding you that you must check each panel for the batten stagger it creates, using compass and all, as in Figure 6.35 and relevant text in PJR. On mehitabel the stagger isn't overly-generous but is enough. 

    You're using higher batten angles than I did, and you must check not only batten stagger, but also where your deeply-reefed and furled sail will end up. This part of the design can take you way back to calculating the rise above horizontal (pp. 100-102) and for me there was no easier way than iteration, to make sure I wasn't wrecking something by changing Ps and batten angles. Numbers have to be flexible while you're doing the geometry.

    Provided you do/did that homework with rigour, I think you'll end up with great sails.

    Cheers,
    Kurt

    Last modified: 13 Mar 2013 08:20 | Anonymous member
  • 12 Mar 2013 00:50
    Quote
    Reply # 1240074 on 1239757
    Deleted user
    Kurt Jon Ulmer wrote:Hi Daniel,

    Parrels - For the aft attachment of the batten parrels, here's one way:
    Make a loop using about 2' of ~1/4" or thinner cord, join the ends with a fisherman's knot, make a Prussik on the batten with 2 or 3 wraps, hard against and aft of the hockey tape, which will be well-stuck and twisted for a little bulk. Then take the main parrel rope/webbing and becket-hitch (sheet bend) it to the loop. (There's your adjustment.) The thin cord won't make a big chafe-prone lump in the sail.

    For the forward attachment, you may have other options at the batten end, if your sail balance isn't much. I use a becket loop there too, so parrels can be changed etc. and so only the small cord needs to go through grommets, or whatever you use.

    Sail plan - Are you working through Hasler & McLeod's sail design chapters? Practical Junk Rig Figure 6.34 and all that?

    Yes.  So far I have:

    Mainsail: 
    P=3' 8"
    B=12' 6"
    U=6" (but only one "U", not two as shown)
    L=22' (as shown, not counting U)
    Batten angles: 10,10,10,12,14,17,22,60 (yard)

    Foresail:
    P=4' 0"
    B= 12' 6"
    U=6" (again only one)
    L=20' (as shown, not counting U)
    Batten angles: 10,10,12,14,17,22,60 (yard)

    About hollowed leech, I'm sure David Tyler is right, that you can shape the panel to make it unnecessary. Or else you'd better hollow the leech a little.
    If the latter, it's hard to avoid a wee bit of a 'hook.'

    I think I will shape the panels a wee bit, just to spread the load evenly.  Since it makes sense to construct them in panels anyway (due to working in a living room) this will be ok with me.  
  • 12 Mar 2013 00:39
    Quote
    Reply # 1240067 on 1239725
    Deleted user
    David Tyler wrote:I have quite a lot of 8mm double braid, half-used, left over from my previous rig, and I'm using it up on the batten parrels. This would be too big to tie neatly around a batten, so I tie a bowline about 6" forward of the batten protrusion, and then make a lashing with 3mm cord around the batten and through the bowline, to tension the parrel. I find I have to pull quite hard, and to retension after a bit of sailing, because there is a lot of initial stretch in the line. After about 6000 miles, I'm seeing no evidence of chafe on the sail (there should be a patch protecting the sail at this point, though, just in case). 
    Got it, makes sense.
    When I have used up the stock of old line, and the batten parrels are degrading and chafing, I have some 3/16" bare Dyneema for replacements - excellent chafe and  UV resistance, very high strength, very low stretch. I would expect to be able to tie this directly around the batten, and then  tension it at the forward end.
    I have 1/4" Amsteel (same stuff) in scads laying around from my old rig which came down.  That and some Dynex Dux.  Was thinking along similar lines (heh).
  • 12 Mar 2013 00:39
    Quote
    Reply # 1240066 on 1238226
    Deleted user
    Our battens have high pressure hose on them to stand off the masts and keep thing quiet. The hose is secure to the battens. We were fortunate enough to get hose that went on the battens tightly and will be impossible to remove. The batten parrels are tied to the battens at either end of the hose with hitches. They have never moved and after securing the end of the knots with constrictor knots have not undone themselves. This system has worked quite well. We use batten pockets and have not regretted this decision.
  • 11 Mar 2013 18:17
    Quote
    Reply # 1239757 on 1238226
    Anonymous member
    Hi Daniel,

    Parrels - For the aft attachment of the batten parrels, here's one way:
    Make a loop using about 2' of ~1/4" or thinner cord, join the ends with a fisherman's knot, make a Prussik on the batten with 2 or 3 wraps, hard against and aft of the hockey tape, which will be well-stuck and twisted for a little bulk. Then take the main parrel rope/webbing and becket-hitch (sheet bend) it to the loop. (There's your adjustment.) The thin cord won't make a big chafe-prone lump in the sail.

    For the forward attachment, you may have other options at the batten end, if your sail balance isn't much. I use a becket loop there too, so parrels can be changed etc. and so only the small cord needs to go through grommets, or whatever you use.

    Sail plan - Are you working through Hasler & McLeod's sail design chapters? Practical Junk Rig Figure 6.34 and all that?

    About hollowed leech, I'm sure David Tyler is right, that you can shape the panel to make it unnecessary. Or else you'd better hollow the leech a little.
    If the latter, it's hard to avoid a wee bit of a 'hook.'

    Cheers,
    Kurt

  • 11 Mar 2013 17:52
    Quote
    Reply # 1239725 on 1239588
    Anonymous member
    Daniel Collins wrote:.

    So do the light cords themselves serve as the adjustment for the parrel or does the parrel have adjustments built in and the cords are simply the attachment for them like a rope grommet?

    Is there a problem doing what you did without the backing batten?  Will chafe on the patch be a big issue here?

    I have quite a lot of 8mm double braid, half-used, left over from my previous rig, and I'm using it up on the batten parrels. This would be too big to tie neatly around a batten, so I tie a bowline about 6" forward of the batten protrusion, and then make a lashing with 3mm cord around the batten and through the bowline, to tension the parrel. I find I have to pull quite hard, and to retension after a bit of sailing, because there is a lot of initial stretch in the line. After about 6000 miles, I'm seeing no evidence of chafe on the sail (there should be a patch protecting the sail at this point, though, just in case). 

    When I have used up the stock of old line, and the batten parrels are degrading and chafing, I have some 3/16" bare Dyneema for replacements - excellent chafe and  UV resistance, very high strength, very low stretch. I would expect to be able to tie this directly around the batten, and then  tension it at the forward end.
  • 11 Mar 2013 16:38
    Quote
    Reply # 1239649 on 1238226
    Deleted user
    Good day Daniel,

    First of all congrats on working a new rig. I'm sure you wil enjoy building it as well as sailing it. I notice you are close (relatively) . I have a stack of rolls of firehoses as high as my waist and you are welcome to as much as you need. My method was to just cut short segments of it and slip it over the battens as I assembled them into the sail. The rubber on the inside of the hose keeps it in place and the canvas on the outside rubs on the mast well. For the battens I used about your size, and was lucky enough to have a roll of 4" diameter as well which I use on the yards and booms. There are some pictures in my files of the arrangement, but the hose is hard to see. If you cant rob some off of the local volunteers, we can do this: send me your diameters and I can leave a roll with my brother in Raleigh,NC. I am with family so I can't get further south right this time.

    In the meantime I will take a picture of the stack of rolls and send it to you with the hose diameters.

    It's an exciting project, isn't it!

    Sincerely,

    John C.
  • 11 Mar 2013 15:03
    Quote
    Reply # 1239588 on 1239377
    Deleted user
    Kurt Jon Ulmer wrote:Hi Daniel,

    Getting enough ideas?

    My head is exploding!


    Couple points:

    Top Panels - The mehitabel plans, both actual and would-do versions, have fairly big top panels. (Main ~90sqft; Fore ~70) Our raised-above-parallel top batten makes the triangle smaller, but leaving out the middle-of-triangle batten makes it bigger.

    The top triangle alone is a usable crab-claw sort of sail, which can be set up to be taut or wind-spilling. The top two panels are a very surprising fanning curvy sail that I use in lighter winds to go slowly, or in strong winds to sail under control.

    Ok, see I did kind of like that about the sails - it's sort of like what Dave Z. is doing on the Triloboat rig... just without quite the loss of area in the severely hollowed leech.

    Parrels - Ours are hitched to 1/4" or thinner cords that go through grommets and wrap around the batten and backing batten. Without grommets, various gripping knots can be semi-effective on the batten directly, and with a few twisty wraps of hockey tape beside them, perfectly effective.

    The point here is that light cord loops grip better in Prussik knots, and can be becket-hitched to whatever kind of parrel rope/webbing you like, allowing easy adjustment and replacement and chafe-movement and dismounting.

    So do the light cords themselves serve as the adjustment for the parrel or does the parrel have adjustments built in and the cords are simply the attachment for them like a rope grommet?

    Is there a problem doing what you did without the backing batten?  Will chafe on the patch be a big issue here?

  • 11 Mar 2013 05:06
    Quote
    Reply # 1239377 on 1238226
    Anonymous member
    Hi Daniel,

    Getting enough ideas?

    Couple points:

    Top Panels - The mehitabel plans, both actual and would-do versions, have fairly big top panels. (Main ~90sqft; Fore ~70) Our raised-above-parallel top batten makes the triangle smaller, but leaving out the middle-of-triangle batten makes it bigger.

    The top triangle alone is a usable crab-claw sort of sail, which can be set up to be taut or wind-spilling. The top two panels are a very surprising fanning curvy sail that I use in lighter winds to go slowly, or in strong winds to sail under control. 

    (One reason I often omit sheeting the top batten, is to allow raising sail to two panels without touching the sheets, and also to sheet in and drop the last two without touching the sheets again. The other reason is to allow some twist.)

    My point is that I'm pleased with the top part of the sail, including when hove-to in gales and sailing offshore, but mostly in routine use, especially single-handing. If smaller triangles are truly advisable, I may find out some day, whereas you can act on that advice now.

    Parrels - Ours are hitched to 1/4" or thinner cords that go through grommets and wrap around the batten and backing batten. Without grommets, various gripping knots can be semi-effective on the batten directly, and with a few twisty wraps of hockey tape beside them, perfectly effective. 

    The point here is that light cord loops grip better in Prussik knots, and can be becket-hitched to whatever kind of parrel rope/webbing you like, allowing easy adjustment and replacement and chafe-movement and dismounting.

    Hope you're enjoying the sketching and distilling!
    Best of luck!

    Cheers,
    Kurt

  • 11 Mar 2013 01:17
    Quote
    Reply # 1239191 on 1238994
    Anonymous member
    Kurt Jon Ulmer wrote:Hi Daniel,

    Construction - I looked out on the brand-new flat vertically-seamed acre of fabric, big enough for the parellelogram portion of our sail, on the firehall floor. Let's see... we could cut it up into individual panels and sew them back together with horizontal seams and batten strips, or... we could roll it up and master getting it through the sewing machine. 

    For a flat sail and easy-working fabric like Top Gun or Odyssey, the latter was a clear choice. Even if someone could now point and show me the bad effect of not rounding .5% between panels, I wouldn't cut the sail apart to put it in. This is soft fabric, not thin plywood!

    Cheers,
    Kurt

    I've seen the effect frequently, particularly in the top parts of sails made from hard polyester sailcloth. The middle of the panel is "starved", and stretched taut, whilst the luff and leech are slack and flapping. Granted, the stretchier cloths will not exhibit the effect as strongly, and granted, the lower part of the sail is less highly loaded, so again, the effect won't be marked.

    So yes, if you have a large hall at your disposal, by all means cut the lower panels all of a piece, and the upper panels individually. If you have a smaller space to work in, then cut all the panels individually, and make a virtue of necessity by adding some rounding. Dare I say it, by adding enough rounding that camber starts to develop?
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
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