The "Sib-Lim" Challenge

  • 03 Feb 2015 17:48
    Reply # 3216882 on 3216506
    Arne Kverneland wrote:

    High AR sail versus low AR:
    Remember; a HAR sloop rig is a different animal than a HAR schooner rig. The schooners sails are HAR because their booms and battens are short, not because the masts are so tall. To get a decent sail area on a HAR sloop, one needs to have a tall mast. That may be less fun on a boat with only inboard ballast. It could work if someone gave you a thin and strong carbon mast, but if you have to pay for your mast, a hybrid of wood and aluminium would probably be your choice (as it would for me). Then, even just a half-decent SA/disp. factor of 18 would call for 37-38sqm. A HAR version of that sail will call for a mast which may approach the practical limits for a hybrid mast.

    BTW, in my eyes, for a sloop a medium AR sail is 2.00 to 2.05. 

    Arne

    All good sense here, Arne. I would add that the higher you go, the more difficult it is to sheet the sail. The higher the AR, the shorter and lighter the yard and battens become, even if the mast is longer and heavier, so there's some levelling of the scales here. My new wing sail has an AR of 2.36, measured as: distance from tack to the tip of the yard/chord. One man's high AR is another man's medium AR, but this is as high as I think it is feasible to go, with JR. And I think that with that kind of AR, one can go for SA/D of 15 for Annie's use, because the sail will be more efficient than a lower AR. Someone bigger and stronger might well go for a larger SA/D, but I keep reminding myself that I am designing for just one "client", in the first instance, with just one client's needs and preferences.
  • 03 Feb 2015 12:14
    Reply # 3216506 on 3144241
    Anonymous member (Administrator)

    David and Annie

    David, woops, I missed your deck beams. Your twin rudders with full size endplates looks great.

    Annie. I found no reason for shifting the 50kg engine of Johanna around  -  it has been sitting on its bracket since 2006. All it has needed for service is changing motor oil and gear oil a couple of times, and replace a pair of sets of sparkplugs. “Winter conservation” has consisted of 2-3 start-ups each winter, with 10 minutes of running in gear. Forget what you remember  from the Seagull years: Modern outboards are very good, so if you get a good deal on a long-leg 2-cylinder motor, I suggest you go for it. Anyway, getting the propeller right  -  big diameter and fine pitch, makes a lot of difference.

    High AR sail versus low AR:
    Remember; a HAR sloop rig is a different animal than a HAR schooner rig. The schooners sails are HAR because their booms and battens are short, not because the masts are so tall. To get a decent sail area on a HAR sloop, one needs to have a tall mast. That may be less fun on a boat with only inboard ballast. It could work if someone gave you a thin and strong carbon mast, but if you have to pay for your mast, a hybrid of wood and aluminium would probably be your choice (as it would for me). Then, even just a half-decent SA/disp. factor of 18 would call for 37-38sqm. A HAR version of that sail will call for a mast which may approach the practical limits for a hybrid mast.

    BTW, in my eyes, for a sloop a medium AR sail is 2.00 to 2.05. The reason why my Ingeborg’s new sail has an AR=1.90 is not that I prefer LAR sails, but just to solve the balance equation.

    Arne

  • 03 Feb 2015 11:07
    Reply # 3216492 on 3144241
    Deleted user
    3215480 of 2nd Feb.

    I really don't like sliding hatches.  You lean against them - and they slide.  You go over a big wash and they slide the other way and trap your finger.  Or, more often than not, they don't damn well slide at all and you have to push and shove.  And with driving rain from astern (and don't forget I spend a lot of time in tidal anchorages), the water starts to percolate along the runner and drip.  So can we try and avoid one, please?

    I am having trouble keeping up, this thread is moving so fast, Annie is your rotating pram hood made as  drawn in PJR?

    Thanks Ash

  • 02 Feb 2015 23:49
    Reply # 3216243 on 3144241

    Hi Arne,

    That's what I was talking about in Reply # 3216210 !

    I've just put some endplates on the rudders, and I've uploaded images of endplates and a cross-section of a principal deck stringer to the Sib-Lim album.

    Last modified: 03 Feb 2015 00:20 | Anonymous member
  • 02 Feb 2015 23:27
    Reply # 3216225 on 3144241
    Anonymous member (Administrator)

    Deck beams  -   one way or the other.

    Hi again A & D,
    just a fast idea, nicked from some of Phil Bolger's plans. I see that the longest span between the bulkheads in the cabin is about 6'. What about  fitting 'deckbeams' lengthwise and let them rest on those bulkheads? If one avoids such a beam right at the centreline, there would be full headroom here to let one walk back and forth.

     

    Arne 

    Last modified: 02 Feb 2015 23:28 | Anonymous member (Administrator)
  • 02 Feb 2015 23:11
    Reply # 3216215 on 3144241

    A: Talking of the developments of the hull panels: what about turning the plywood through 90° at that area where it's not quite wide enough.  It wouldn't matter would it?

    Actually, there’s a good reason to keep the sloping hull panels fore and aft. The 4ft width of ply puts the join just where the bilge board slot lies, so the sequence would be something like this: set up bulkheads and longitudinals (including the inner and outer sides of the bilgeboard case),  put on the bottom panel, put on the 4ft wide part of the sloping panel with its outer edge butting against the board case, probably with a stringer underneath the outer edge acting as a butt strap and reinforcing the join, then the topsides, then the narrow extra piece of sloping panel out to the chine.


  • 02 Feb 2015 23:06
    Reply # 3216210 on 3144241

    I’ve reworked the cockpit, in line with Annie’s predilections, and a “perspective" view of it is now at http://www.junkrigassociation.org/Sys/PublicProfile

    /2757889/PhotoAlbums/38135030.

    To put some numbers on it:

    Inside height of companionway - 1060mm. Annie, please compare with Fantail’s and let me know.

    Cockpit sole to top of companionway - 1300mm. You will be able to see over it while standing at the helm. Ditto. Easy to adjust both heights.

    I was originally thinking of a long shaft OB, for 20in transom, and that was what set the cockpit sole height. Now I’ve lowered it, and the OB will be a standard shaft for 15in transom. Cockpit sole 200mm above DWL at aft end.

    Cockpit seats 450mm above sole.

    Bridge deck added, at half of that height. An easy step up. Stowage for halyard tail etc.

    Wedge-shaped addition to deck, that can take a pramhood. A loose closer for the pramhood? You can not be serious, man! Worse than a loose washboard. This wedge can accommodate a slide, which will drain forward and out of holes in the side. Top of wedge overhangs bulkhead by 110mm.

    Height from seat to sheer at forward end of cockpit - 406mm. You should be able to step up to the deck easily.

    Height from seat to sheer at aft end of cockpit - 665mm. You should be able to nestle at aft end, glass in hand, out of the wind but able to see all around.

    A: I have to confess, I like deck beams: they do give a very reassuring sense of strength.

    OK, we could use two layers of 6mm on beams. They look nice, if exposed, but actually are a throwback to longitudinal planked decks. With decks of sheet materials, it makes more practical sense to use longitudinal stringers resting on the bulkheads.

    I like your plan of building from the inside out. That’s what I tried to get them to do on Tystie, but didn’t win the day. They chose to do it the hard way, adding the lining last.

    So: 

    3mm ply headlining (underside brought to as near to finished as possible), laid down on the bulkheads and as many temporary formers as needed, a central 4ft sheet and then more to make up the width.

    60 x 30mm stringer, 2ft off the centreline, with groove routed on its underside for cabin lighting cables.

    More smaller stringers, at intervals to be decided.

    Insulation between stringers, 25mm extruded polystyrene house insulation.

    Blocking instead of insulation in way of mast and deck fittings.

    A central 4ft sheet of 6mm ply, to land its edge on the stringers. More to make up the width.

    A second layer of 6mm ply, butting its inner edges on the centreline. More to make up the width.

    Removable wooden cover strip over cable groove.


  • 02 Feb 2015 22:28
    Reply # 3216169 on 3144241
    D: May I introduce the idea of a ply/foam/ply deck for Sib-Lim? I’m still a bit concerned about getting enough sailing stiffness and stability with such shoal draught, and I would like to make the deck as light as possible and as low as possible. If the deck is of 6mm ply/25mm structural foam/6mm ply, it will avoid the weight of deep-sectioned deck beams and maximise the headroom. With this style of deck, and my current design, I can get 5ft 5in headroom on the centreline. This is about what I have over my galley, and I’m quite comfortable with that, with my air draught of 5ft 9in. I don’t think my Sadler 25 had as much as 5ft 5in.

    A: I can see your point, David.  The problem is ensuring that it stays laminated.  The sun in NZ is very fierce and there are more than a few boats around that have had the foam come away from the wood due to the difference in expansion and contraction.  Then there is the added irritation that occurs whenever you want to add any deck fittings.  One of the reasons I want a wooden boat is so that I can screw things into it after the event.  I have to confess, I like deck beams: they do give a very reassuring sense of strength.  And if I made them from kahikatea, they wouldn't be that heavy.  I do like the idea of an insulation layer, but the method I'd been thinking of was building the deck beams, attaching the headlining of whatever to them, putting insulation between them and then the plywood on top.  I can be happy with 5ft 5in, especially with a pram hood where tall people can stand up for a minute or two before sitting down. 

    D: Did you notice how I’d widened the forward end of the cockpit to over 5ft, and dispensed with sidedecks, so that you could sit right out to the weather side and to weather of the tiller to steer? The seats are angled, too, so that you face a little more forward and don’t crick your neck. This is the tiller equivalent of the twin wheels that big posh boats fit so that the helmsman can see where to go, over the curve of the sidedeck and past the rig. We’d have to put a shallow triangular sectioned footbar on the cockpit sole, down the centreline.

    A: Oh, that's why they have two wheels!  I'd always wondered.  To be honest, I didn't realise that you had widened the cockpit, but then most of the lovely little images you send me have no scale on them.  (How true it is, even for someone as non-visual as I, that one picture is worth a thousand words!)

    I hadn't had time to comment on the 'view from the port quarter' that you sent me, but if I had, I would have asked about the now-eliminated side decks.  I hadn't quite appreciated that the tillers were so close to the centreline, but of course, it's obvious now that they can easily be used in a fairly conventional manner.  Indeed for someone with my LOA, they are probably more user-friendly than a single one, especially with the wide stern.  The foot bar also makes sense when one is hauling on a sheet, in a wide cockpit like this one.  Not being able to brace oneself can be quite dangerous.  I have problems, even with Fantail's relatively narrow cockpit, at times.

    What I like about this layout, is that it will be much easier to move from cockpit to deck.  I would envisage deck boxes acting as a step at the forward end.  These would also make comfortable seats and provide rope stowage, a la Badger.  An idea that worked wonderfully well: I haven't come up with anything remotely so usable on F.

    D: So the cockpit is quite wide, which you may or may not like. If you don’t, you could fit a kind of stub tiller to the centre of a crossbar mounted at the forward ends of the tillers. But that would take up cockpit space, and you couldn’t hinge the tillers up out of the way.

    A: I don't think I really have an opinion on the width of the cockpit.  I can see it being a great asset at junkets with lots of people on board.  I have much more of an issue with a cockpit that has no 'sides' than whether it is wide or narrow.  On a well-heeled boat I find it quite frightening to have the sea only inches away from the cockpit side deck.  The tiff seems to show a reassuring bulwark. I know that wide sterns induce surfing and I'd prefer to have a boat that doesn't surf.  Too scary and needs too much concentration.  But I can always reef!  Talking of extreme eventualities (well, you never know, do you?) would the twin rudders make any difference to using a Series drogue?

    Is there a bridgedeck?  It doesn't look like it.  I like bridge decks.

    D: I think you either go for low AR, fanned and not too cambered, or you go for high AR, Van Loan/LC, with quite deep camber. The latter is probably the better performer, so long as the boat has enough stiffness to carry it, and is better for balance, furling and deep reefing too. I didn’t think Tystie had enough stiffness, to begin with, but now I’ve gone high AR, and found that she can carry that kind of sail, I’ve changed my mind. Doesn’t look as pretty as a fantail sail, though.

    A: One of the things I really like about La Chica's sails is that the running luff hauling parrels are almost redundant.  They set up quite slack.  Having bent one of my battens because of the loads from the original set up (twice around the mast), I am a little disenchanted with them.  To be fair, however, my present system needs much less heaving.

    I agree that the fantail sail is the prettier of the two, but do have a couple of continuing issues.  I set up the boom as per your design: 1m above deck with the forward end 1m forward to the centreline of the mast.  All well and good.  But the lower panel always has a crease in it.  I can eliminate this by moving the boom forward about another 200mm, but the result of that is that its after end is dramatically lowered and swipes me in the cockpit.  Unfortunately, this is unacceptable to the point of being dangerous, so I have to live with the crease.  Neither Footprints nor Tystie seems to have had this issue.

    As for stiffness: LC is anything but and nor, for that matter, is Zebedee, but they both have quite HAR, deeply-cambered sails.  I think it's watching them sail that has made me in favour of HAR once again.  After all, once the sail is reefed, the aspect ratio of the rig is no longer high!

    Last modified: 02 Feb 2015 22:35 | Anonymous member
  • 02 Feb 2015 22:21
    Reply # 3216165 on 3216116
    Arne Kverneland wrote:

    Twin rudders  -  yes! There are so many shallow draught sailboats with inferior rudders, but this one will do fine.

    Great to have you on board for this debate, Arne.  I was a bit nervous about the twin rudder concept, so knowing that you have definite views about rudders am more than happy with this endorsement!

    I found that fitting the ob. engine at the centreline on Johanna had two positive effects:

    1.      The engine became surprisingly resistant against cavitating as the boat rolled, and even if we were motorsailing. This happened in spite of the engine being fitted to a semi-long counter. Moreover, with the engine swung up, it will not dip its leg on one tack.

    It's most reassuring to hear about the lack of cavitation.  One of my nastiest places to sail is around Cape Brett, where I often lose the wind and end up in the most unpleasant sea, stirred up by a strong tide and made worse by the backwash from the cliffs (which extends a long way offshore)  An ideal situation for an ob to misbehave itself.

    2.      Thanks to the extra long leg, plus central mounting, there is no need to have a lifting bracket, it being enough to swing the engine up and down.

    I can see your point with adding a slot in the hull for the leg, if only to bring the engine within more comfortable reach (and inside the sheet). In addition, I guess it will in be less prone to being swamped  or knocked off by offshore waves with this inboard installation. Could I suggest that you make the slot wide enough to let you turn the engine at least 30° to each side? Sometimes, if one has to evacuate a tight spot in some winds, the vectored thrust of the ob. can make up for being on the small side. With the windage of the sloop JR mast, I have found this to be very useful.

    I have to say that I was very happy with the idea of the engine being brought further forward for the reasons you outline.  A good point about being able to turn it.

    I guess a 6hp engine would do (weight 26kg) but those of 8hp (40kg) normally come with 2 cylinders, so are quieter and more dependable. It is no hardship to swing up a 40 kg engine  as they are so well balanced. Johanna’s 9.9hp ob. is a downrated 15hp Yamaha 4-stroke, 324ccm and 50kg, but I never struggled with swinging it up.

    There is also the considerable extra expense of an 8hp engine, as well as the weight.  I'm sure that swinging it up and down would be quite easy, but I might have to take it off from time to time.  40 kg is well beyond my limits, even if I rigged up blocks and tackles to help me..
  • 02 Feb 2015 21:05
    Reply # 3216116 on 3144241
    Anonymous member (Administrator)

    Rudders and ob. engines

    Annie and David,
    it seems to me that you have gotten this very right.

    Twin rudders  -  yes! There are so many shallow draught sailboats with inferior rudders, but this one will do fine.

    I found that fitting the ob. engine at the centreline on Johanna had two positive effects:

    1.      The engine became surprisingly resistant against cavitating as the boat rolled, and even if we were motorsailing. This happened in spite of the engine being fitted to a semi-long counter. Moreover, with the engine swung up, it will not dip its leg on one tack.

    2.      Thanks to the extra long leg, plus central mounting, there is no need to have a lifting bracket, it being enough to swing the engine up and down.

    I can see your point with adding a slot in the hull for the leg, if only to bring the engine within more comfortable reach (and inside the sheet). In addition, I guess it will in be less prone to being swamped  or knocked off by offshore waves with this inboard installation. Could I suggest that you make the slot wide enough to let you turn the engine at least 30° to each side? Sometimes, if one has to evacuate a tight spot in some winds, the vectored thrust of the ob. can make up for being on the small side. With the windage of the sloop JR mast, I have found this to be very useful.

    I guess a 6hp engine would do (weight 26kg) but those of 8hp (40kg) normally come with 2 cylinders, so are quieter and more dependable. It is no hardship to swing up a 40 kg engine  as they are so well balanced. Johanna’s 9.9hp ob. is a downrated 15hp Yamaha 4-stroke, 324ccm and 50kg, but I never struggled with swinging it up.

    Good luck!

    Arne

     

    Last modified: 02 Feb 2015 21:12 | Anonymous member (Administrator)
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