SibLim 10 metre

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  • 18 Nov 2021 22:41
    Reply # 12136179 on 12134087
    Anonymous member (Administrator)
    Anonymous wrote:
    ... However, sooner or later I think I will need to change to a sail with a much more horizontal boom and a yard that can hang naturally.  In the meantime, I feel much happier with how the boat is sailing and the relatively small amount of camber built into the sail seems sufficent to get her to windward.

    Annie,
    Maybe you could persuade David to draw you a Fantail-style sail? This would be easy to set further aft, and the boom is nearly horizontal.
    Good luck!

    Arne

    PS: Should this discussion about FanShi be given its own topic?
    Last modified: 19 Nov 2021 00:05 | Anonymous member (Administrator)
  • 18 Nov 2021 19:52
    Reply # 12135946 on 12102843
    Rudolf wrote:
    David wrote:

    A quick peek at SibLim 10m with Poppy's SJR. The mast is a hybrid base on a 10 inch diameter tube.

    At first glance I would want the mast a bit more forward. Maybe one mast diameter.
    You were right, Rudolf. I've had to put the mast hard up against the after end of the double berth and rake it forward by 2˚; and then move the keel aft by 100mm and make the skegs very large, to get the helm balance looking somewhere near right.
    1 file
    Last modified: 18 Nov 2021 19:54 | Anonymous member
  • 17 Nov 2021 21:09
    Reply # 12134087 on 12107939
    Arnie wrote:Possible remedies:
    • ·         If the lee helm is not severe (rudder angle?), and the boat tacks reliably, leave it as it is. I got used to the moderate lee helm on my Johanna (light winds only, close-hauled).
    • ·         Move the halyard on the yard as far forward as you can before the sail gets tail heavy. This may reduce the problem.
    • ·         Would it be possible to shift the bottom end of the mast a bit forward within the tabernacle? To get the mast top 30cm aft (=2°), the bottom end only needs to be shifted 3.7cm forward. The total ‘pole’  -  mast plus tabernacle  -  would then get a little bend on it, but hardly enough to cause too high twisting stress.
    PS: I think that what Annie calls a "running yard parrel", in fact is a Throat Hauling Parrel, THP.

    Arne, as ever, thank you for your input.

    The lee helm, when I first sailed the boat, was definitely severe and noticeable in a good F3, even up to F4. 

    I tried moving the halliard forward to the correct position, but it made reefind very difficult with the sail likely to get out of control.  After two scary occasions I moved it back where it should be.

    We will agree to disagree about a plumb mast.  I like sailing in light airs.  This coastline often has an onshore swell.  The forward rake keeps the sail asleep.  And, no, I couldn't move the base of the mast 3.7 cm forward and still keep it secured in the tabernacle without a considerable amount of work.

    What I called the running yard parrel was different from a throat hauling parrel, but it didn't work, so we'll forget about it.

    Since my last posting, I have taken all the knuckles out of the battens and gone back to a standing yard parrel, which prevents the sling point from hanging where it wants to when the sail is fully hauled.  It makes hauling up the last 3 panels very hard work, but as I have a winch, I can live with that.  I have a luff hauling parrel from the first sheeted batten down to the next one which stops the luff going too far forward.  For the moment, I am sailing with looser lazyjacks to keep the foot of the sail lower.  This of course makes the reefing less than elegant.

    The other day, I sailed close-hauled in enough wind that I was happy to have 2 reefs in the sail - probably F4.  I reef early, having clouds of canvas.  The boat sailed really very well, tacking reliably and pointing,nicely. If I left the helm on port tack - the one that had the worst lee helm - she now sailed herself following the wind shifts.  I needed a light hand on the helm to stop her luffing up on starboard tack.  I was very happy with her progress.  I then ran up an inlet and anchored.  The next day I sailed through the moorings and out to another inlet, which I ran down.  She really needed more sail to be confident of tacking while I was among the moorings, but with both boards down, she was pointing well and responsive.  Again, this was on the dreaded port tack.  I rather feel that my wonderful, hinged battens may have been partly responsible for her bad manners.  However, sooner or later I think I will need to change to a sail with a much more horizontal boom and a yard that can hang naturally.  In the meantime, I feel much happier with how the boat is sailing and the relatively small amount of camber built into the sail seems sufficent to get her to windward.

  • 16 Nov 2021 02:05
    Reply # 12130054 on 12128864
    David wrote:

    Today, I’ve been having a long hard think about the hull size and proportions. As a result, the LOA has grown a couple of inches to 10.1m / 33ft, and the beam has decreased about a foot, to 3.45m / 11ft 3in - still a beamy boat, a foot more than Don's current boat, a  Nicholson 31, and the planned accommodation still fits in. I think this is a better boat on all the aspects that I can think of. The companionway width is now a more reasonable 650mm minus any framing. Also, I’ve spaced the sections at 1.05m to decrease the number of temporary moulds between permanent bulkheads. This will make setting up a lot easier - you need enough shoulder room to wriggle through and around the moulds.

    Those are about the exact same dimensions as Shoestring and Footprints except they were only 3.3m in beam. With the flush deck that makes for a very roomy boat for just a couple of people. When we did our New Caledonia cruise in Footprints as a family of three, two adults and a child, we found that she had more than adequate space and we did not feel at all crowded in after 4 months of living onboard together. The one thing that helped with this was that the Footprints design has the two separate sleeping cabins, one at either end of the boat which helped with privacy for mum and dad, or maybe for daughter. Regardless the Siblim 10 is going to be a very comfortable spacious cruising yacht.
  • 15 Nov 2021 17:15
    Reply # 12128864 on 10668989

    Today, I’ve been having a long hard think about the hull size and proportions. As a result, the LOA has grown a couple of inches to 10.1m / 33ft, and the beam has decreased about a foot, to 3.45m / 11ft 3in - still a beamy boat, a foot more than Don's current boat, a  Nicholson 31, and the planned accommodation still fits in. I think this is a better boat on all the aspects that I can think of. The companionway width is now a more reasonable 650mm minus any framing. Also, I’ve spaced the sections at 1.05m to decrease the number of temporary moulds between permanent bulkheads. This will make setting up a lot easier - you need enough shoulder room to wriggle through and around the moulds.

    4 files
  • 08 Nov 2021 09:52
    Reply # 12109506 on 10668989
    Anonymous member (Administrator)

    The opposite problem...
    When I converted my Ingeborg to JR, I didn’t do my homework properly, so ended up with a bit too much weather helm. Luckily, there was room for moving the sail forward on the mast until the halyard blocks on the yard (sitting 5% aft of the middle) were sitting close to the mast. The Tack Parrel, TP, down at the boom, was then eased until the luff became parallel to the mast.
    This fixed the steering balance, and suddenly the forces in the Throat Hauling Parrel, THP dropped a lot as well. Win-win!

    Halyard drift -  my new 18% rule...
    To prevent myself from cutting a mast too short again, I have lately started to design in a halyard drift of 18% of the batten (and yard) length, B. The real drift will be a bit shorter, since the yard will take up a bit space (I don’t bother with drawing in yard and boom in my sailplans).
    Ingeborg’s present mast is tall enough, but only just so. The “18% rule” would have made her mast 25cm taller, which would give more elbowroom for making adjustments.

    Arne

    PS: For the newcomers; here the lines have been explained:

    http://goo.gl/vzGLzi

    (Note: the Throat Hauling Parrel, THP is just a special version of the shown LHP, but now only working on the forward end of the yard, plus  -  quite often  -  on batten no. 2 from top)

    Last modified: 08 Nov 2021 10:48 | Anonymous member (Administrator)
  • 08 Nov 2021 00:28
    Reply # 12108513 on 10668989

    I think Arne is right – anyway, I can say I had a very similar situation with my little SJR sail - “…the sail…wants to set too far forward from where it should be…”.

    The SJR should not need the conventional hauling parrels, as it is designed to drape almost by itself, without them, but I was forced to try adding a standing parrel to the yard, because the sail kept slouching forward. (With SJR there is no choice – the sail has to be set “where it should be” because of the slot).  So, I added this parrel, (edit: I believe it is called a Throat Hauling Parrel, anyway, its purpose is to haul the yard back). And then I found, same as Annie, that it had become unacceptably difficult getting the last part of the sail hoisted, though the sail could haul up and set very comfortably with one reef in.

    Since the sail had to be forced into position regardless, I never found out if it would have caused lee helm.  I didn’t want to add a running parrel to this rig, but something had to be done. At first I did not realise what the problem was, but it had to be something to do with the geometry of the set-up, and I realised in the end it was because in the last couple of metres of raising the sail, the halyard angle became too great, resulting in a large component of the halyard force pushing the yard forward. The halyard attachment point of the yard was already as far forward as I could make it.

    The halyard angle was too great, simply because the mast was too short.


    This problem was not intuitive to me when I made the mast. I had made sure the halyard blocks would not be chock-a-block, and that there would be enough halyard drift to allow the yard to rotate – but I found out too late that, in my case anyway, this is still not enough.

    (The clue for me was the realisation that with one reef in, there is heaps of halyard drift. That meant the angle of the halyard is less, and thus the unbalanced horizontal component of the halyard force is less.)

    Luckily, I did not need to add a running parrel to haul the yard forward back, because (1) the SJR mast is vertical, which alleviates some of the halyard angle and (2) because of a peculiarity of my tabernacle arrangement I was able to raise the mast up higher, and gain the extra halyard drift that was needed. The problem was 99% solved, and if I get around to it, I will raise the mast another few inches more this summer.

    My reason for chiming in is not directed at Annie (who is onto it, and knows more about these things than me  anyway) but as a warning to anyone else who is building for the first time a low yard angle rig such as the Amiina Mll SJR, or quite possibly any low yard angle rig: though it may not seem necessary, the mast height must be at least as high as the peak of the yard, and higher still would be better. This is to ensure that the angle between the halyard and vertical (not the angle between the halyard and the mast) is kept within an acceptable limit. I think Arne can probably advise what would be the optimum halyard angle, but for the Amiina Mkll rig, that minimum mast height quoted above would be my rule of thumb.

    (With SJR you don’t have the luxury of altering mast rake (actually, forward rake exacerbates the halyard angle problem) and you don’t have the luxury of being able to haul the sail forward or aft.  So allow for plenty of halyard drift and achieve the minimum halyard angle. You can always shorten the mast later (but you probably won’t)).

    PS A little bit more thinking about the geometry of it, leads me to believe that this requirement for halyard drift is greater with the low yard-angle rigs, and maybe less of an issue for the high peaked yard of, say, the Johanna rig. I think Arne was aready alluding to that. (If I am correct, this makes two reasons why the Johanna-type rig gives maximum sail area for minimum mast height.)

     Forward rake also adds to this halyard angle problem. It is interesting to draw some diagrams and look at the relationships between yard angle, sail balance, mast rake, halyard drift and halyard angle. 

    The more these parameters can be harmonised, the better.

    (PS thanks to Arne for pointing out my mistake in terminology, which I hope I have now corrected. I am not familiar with the terms YHP, THP, HKP etc because the split junk rig has  a different system for controlling the drape of the sail - and my copy of "Hasler/McLeod is locked away and I couldn't look it up!)

    Last modified: 09 Nov 2021 08:15 | Anonymous member
  • 07 Nov 2021 19:05
    Reply # 12107939 on 12105622
    Anonymous member (Administrator)
    Annie wrote:
    David wrote:

    Yes, the rig does look quite far aft, doesn't it? On the other hand, Annie says that Fanshi has too much lee helm in light conditions, and I think that's because the twin skegs are more effective than a single skeg would be, at holding the stern up to weather. So I'm proposing to use less lead than is usual, maybe no more than 5%.



    I wouldn't bet on that, David.  I think it is the sail.  It 'wants' to set too far forward because the halliard hauls the centre of the yard forward from where it 'should' be according to the sail plan.  I am adjusting it (yet again) today and have rigged up a running yard parrel that drags  the yard back more to where it should be at full sail.  (I had a standing one, but it made pulling the sail up shockingly hard work.)  I'm also removing the cones from the battens (sorry about that) - the sail just doesn't look right with them so far aft.

    As soon as I reef, the sling point can move aft more easily and the lee helm vanishes.  The skegs make no difference to how the boat moves at anchor.  I would have expectedd them to do so if they make so much difference to how she sails.  I am no expert and not a designer, but my feeling is that it's the sail that is wrong and not the mast placement.  (I have also confirmed my hunch that you designed a sail for a 2 degree rake, instead of the 4 degrees that we have.)


    Reasons for lee helm, and how to deal with it.

    Annie,
    I had very much the same experience with lee helm on my Johanna as you have. The reason in both cases is the obvious one  -  the required position  of the sail is difficult to achieve with a full sail because the halliard is pointing too far aft.
    The reason for this on Johanna was simply that I had cut the mast too short. As soon as the first reef was taken (photo), the sail could be hauled aft, and steering balance was again restored.

    Now I have had a close look at your sailplan, and have a few ideas:
    The low yard angle will naturally move the slingpoint on the yard aft and away from the mast. In addition, the mast angle on that sailplan is 2° forward of vertical. This means that the mast top on the plan now sits about 30cm forward of where it would be on a plumb mast (rotating around the top of the tabernacle). Had the mast been plumb, your present sail would be easy to set in the drawn position.

    Possible remedies:

    • ·         If the lee helm is not severe (rudder angle?), and the boat tacks reliably, leave it as it is. I got used to the moderate lee helm on my Johanna (light winds only, close-hauled).
    • ·         Move the halyard on the yard as far forward as you can before the sail gets tail heavy. This may reduce the problem.
    • ·         Would it be possible to shift the bottom end of the mast a bit forward within the tabernacle? To get the mast top 30cm aft (=2°), the bottom end only needs to be shifted 3.7cm forward. The total ‘pole’  -  mast plus tabernacle  -  would then get a little bend on it, but hardly enough to cause too high twisting stress.

    As you can see on Fanshi’s sailplan, the high-peaking (Ingeborg-)sail I have dropped on top of the original, is easier to pull aft without too flat halliard angle.

    Good luck!
    Arne

    PS: I think that what Annie calls a "running yard parrel", in fact is a Throat Hauling Parrel, THP.


    Photo: Peter Manning, 2008


    Last modified: 08 Nov 2021 14:16 | Anonymous member (Administrator)
  • 06 Nov 2021 20:06
    Reply # 12105710 on 12095106
    Zane wrote:

    I read somewhere that modern petrol cars will be less a carbon burden on the world than the carbon / fossil fuels needed to produce electric vehicles.

    I believe in the science of global warming, I am yet to be convinced that the lithium alternative to fossil fuels is all it is cracked up to be as far as being the brake on global warming that we all hope it will be


    Zane, what this comes down to is that there is no such thing as a good car.  You just have to choose the one that is least bad, if you really feel you have to have one.  The fact that we still live in a consumer society where there is no incentive for anyone to persuade you not to buy a car, doesn't really help.

    I don't believe that we are going too far off-topic here.  After all, the thread is about SibLim - Small Is Beautiful, Less Is More and as long as the design has that name, it should be the underlying consideration.  If you need a car to build the boat, like I did, then the philosophy needs to be applied here.  I have to say that reckoning it all up is by no means easy!!

    Last modified: 06 Nov 2021 20:10 | Anonymous member
  • 06 Nov 2021 20:02
    Reply # 12105705 on 12095674
    Anonymous wrote:

    Green-ness? Ecology? The only sustainable answer is to consume less. If we want to be "green", we'd better not cut down trees and stick their timbers together with synthetic resins, then make sails out of synthetic materials. In fact, we'd better just make coracles and kayaks with wicker frames and natural fibre or animal skins.

    All of which has nothing to do with the choice of auxiliary for this boat, which decision needs to be based on convenience, cost, availability and suchlike factors. There is no "green" solution. Or rather the only "green" solution would be to have no auxiliary at all.


    But David, it isn't a case of either/or, and presenting it this way is what makes people despair about having any power at all, over their chance to stop things getting worse.

    No-one is suggesting that you go around naked.  However, go and see if you can find what you are looking for second-hand, before buying new.  As I mentioned, ecological overshoot is at least as important as reducing carbon but no-one is discussing it.  If you buy something already existing, then at least you have used no more resources to keep you warm or whichever example you want to choose.  And when you buy, or build, new, try and make something that will last for decades or even longer.  I have two woollen jumpers that are both about 50 years old!

    Yes, the green solution would be to have no auxiliary at all and I wish I had the mentaility to go with that.  The next greenest thing is to avoid using one's engine.  Having a smaller boat with a sail and a low horsepower engine is a better alternative to a twin-engined launch.  None is as good as nothing, but better to try for success and fail now and then rather than give up completely.

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