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Pacific Spray - Booms, Battens and Sheeting

  • 06 Dec 2011 21:51
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    Reply # 767372 on 765598
    Anonymous member (Administrator)

    Stavanger, still Tuesday here

    Annie, you wrote:

    "On the other hand, I still look at my battens with less than unalloyed enthusiasm (sorry, couldn't resist the pun) as so many people have had problems with them.  Of course, people break wooden ones, too."

    I find aluminium battens to be very good because they are more flexible than wood, so will bend and complain to me long before they take a permanent bend – or break. By checking your battens from the cockpit in a full F5 you can detect any pumping, panting or flexing in one or more battens. If they do that, they should be beefed up in case they are to take more winds (upper battens). Just remember that wind force (load) varies with the square of the wind velocity and the batten strength varies with the cube of the diameter (if the wall thickness varies with the diameter).

    In other words; if the upper battens shows sign of some bending in a F5, replace them with new that are twice as strong (same diameter with just over twice the wall thickness or by increasing the diameter about 26%).

    Finally; I was originally sceptical to using the 50mm by 1.5mm battens for Johanna, being afraid they would be dented and collapse. However, there has been no sign of that happening (..yet...). Therefore I recommend big diameters and fairly thin walls for battens, giving good stiffness and strength for the weight.

    Arne

    PS: Apposite... Annie, thanks for teaching me new words all the time – surely no one knows more adjectives than you do! Well, I guess I live as long as I learn...

    Last modified: 06 Dec 2011 22:00 | Anonymous member (Administrator)
  • 06 Dec 2011 19:47
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    Reply # 767278 on 765598
    Anonymous member
    Annie,
    I agree 100% with all you say about heavy weather gybing and the inadvisability of using a boom brake.
    I can add that a ketch is only different from a schooner in that the larger sail, forward, is blanketed by the mizzen, and so it's easier to deal with than the larger sail, aft, of the schooner.
  • 06 Dec 2011 19:08
    Quote
    Reply # 767252 on 765598
    Anonymous member
    Arne (all legible) - the comparison table is a brilliant idea.  It would help many people at the decision-making stage.  It could be done on a simple spread sheet and we could even break that down to different pages by size and number of masts to make it as user-friendly as possible.

    Your comments re batten scantlings are again apposite.  The big yard we had on Badger was very reassuring, but the elegant alloy one on Fantail gives me no worries at all.  On the other hand, I still look at my battens with less than unalloyed enthusiasm (sorry, couldn't resist the pun) as so many people have had problems with them.  Of course, people break wooden ones, too.

    Re gybing in heavy weather.  I would run a mile from a boom brake - the boom would snap like a carrot unless you went to gaffer/bermudian-type scantlings.  Ideally, when gybing, one brings the wind so far onto the other quarter that the sail is almost feathered when it has finished its gybe, in order avoid shock loads.  A lot of people find this a bit hard to get used to and a fan-up preventer is recommended for a heavily-reefed sail.  So an alternative method is to bring the wind so that you are sailing well by the lee.  Now, without taking the sheet off its cleat/winch, quickly haul in the mainsheet hand over hand while putting the helm even further up, and as the sail comes across, let go of the sheet, which will run out to its full extent.  But as you have the wind well on the quarter rather than dead aft, it will not bring up with a heavy shock.  If you have a schooner, sheet the foresail in fore-and aft before starting operations.  I have no experience on a ketch.

    If the sea state is too scary for any of the above.  Drop the sail down to its top 2 or 3 panels and do a hard gybe, ie sheet the sail in amidships before gybing.  Even then, I would usually let the sheet run out as soon as the sail comes across to reduce the shock (to me, as much as the vessel).  Shaking out a couple of reefs again is not really biggie, after all.

    Unintentional gybes are, in my experience, a rare event with a single sail or the mainsail of a schooner.  The foresail may well misbehave, but that is because it is in the lee of the mainsail, so there should be no weight in the gybe.  Reef it and sheet it hard in if it's being a nuisance.

    A forward rake to the mast further reduces a sail's tendency to gybe until required to.
  • 06 Dec 2011 13:42
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    Reply # 766988 on 765598
    Deleted user
    Brian, surely the boom on a junk rig will be too lightweight to take the forces of a "boombrake"???  It is barely more than a batten, using it to halt a gybe will put the whole weight of the sail/and bundle on to the boom alone .  TONY and SALLY
  • 06 Dec 2011 13:20
    Quote
    Reply # 766968 on 765598
    Anonymous member (Administrator)

    Stavanger, Tuesday

    This is a very important thread which hopefully, rapidly will lead us up the ladder of knowledge on scantlings. It shows a very serious shortcoming of the PJR book:

    1. Sail area and LAP alone defines the scantlings of the mast(s). No mentioning (?) of compensating for varying displacement.

    2. Sail shape and size alone defines the scantlings of the (wooden) yard, battens and boom.

    On light boats with big sails (Malena, Johanna) this would have lead to over-heavy masts, so I ended up modifying the formula to write the boat’s displacement indirectly into it (see my write-up "Chapter 6, The Mast")

    The same happened to the yard: A PJR yard in wood turned out to be a heavy monster on Johanna, so it was replaced with a braced aluminium yard. The battens and boom (5.8m +10cm) all started as 50mm diameter, 1.5mm wall tubes of ordinary aluminium. I noticed that the long batten no. 2 (6.3m long, the top sheeted) "pumped" a bit in a F5. In a make-it-or-break-it sail (F6), downwind with full sail, a weld in the yard broke and batten no. 2 was bent. The yard was repaired with better welds and the bent batten was replaced with one of double strength by going for 3.2mm wall (still 50mm diameter). No problems after that.

    It’s a pity I don’t have the dimensions of the 23ton "Samson"s battens here, but I know they are a lot heavier than those on "Pacific Spray", on Ron Glas or on Ti Gitu. Despite carrying only 37sqm in her fore sail, Samson’s fore mast is 28cm, solid wood, versus 25cm hollow spruce on Johanna’s 48sqm sail.

    Conclusion, so far:

    We need a new folder on this website, called boat, rig and sail database, or something, where each member (in a .doc or .pdf format) can write up their own boat(s) in dry numbers and with comments on how the components have stood up in use. Personally I would also like to see a listing of parrels and sheets used, and how – but that’s me... Until The Formula of Everything is ready (Einstein failed to find it), this database would be a tremendous help for people who want to fit or improve a junkrig. Just by looking up boats of similar displacement and rig type in that database, they would soon be able to lash up a good rig without too much wild guessing on scantlings.

    Arne

    PS: Did any of this text get hidden outside the edge?

    Last modified: 06 Dec 2011 15:42 | Anonymous member (Administrator)
  • 06 Dec 2011 12:52
    Quote
    Reply # 766952 on 765598
    Deleted user
    Re gybing, intentional or unintentional: Our Freedom 39 (now converted to schooner junk) came with a ' Dutchman Boom Brake', which I can vouch effectively controlled gybes on the Freedom rig and I'm hoping will control them on our junk conversion. It's essentially a friction device - the more turns of the appropriate rope on the helical drum, the more difficult a gybe is. Control of the tension is via a couple of handy billies, one each side of the boat. I'll be trying it out next season and will report back. They often come up on eBay, and there's a discussion about them here on the Freedom web site. A couple of members discuss using instead a DIY version - climbing ascender instead of the patent brake. Thought I'd seen some pictures on the site but haven't been able to track down.
  • 06 Dec 2011 04:03
    Quote
    Reply # 766743 on 765901
    Anonymous member
    Gary Pick wrote:Annie no disrespect to my Kiwi neighbours but NZ Oregon is rubbish. I'd look around for a timber salvage yard and see if they had any North American old growth kicking around.

    Just so dear man - that's what I said!
  • 05 Dec 2011 23:50
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    Reply # 766569 on 766511
    Anonymous member
    Robert Prince wrote:
    Paul Thompson wrote:
    Robert Prince wrote:The battens we had were identical to Fantail's, being Ullrich Alluminuim UA7420 drawn tube with drawn tube sleeving at the joints.

    Rob and Maren


    Well Rob, then you know the answer. Annie's sail is 317 ft.sq. and her boat is under 3 tons. The 38mm battens that she has are adequate for the job on her boat. No ways are they going to do the job for you when the lady (your Spray) puts her shoulder in and gets down to some serious work.


    Hi Paul,

    Good point, we agree.

    In defence of Pacific Spray she does appear to be easily driven, despite her weight and the wooden masts take a bit of tension off the sails. We agree that the battens are too light but maybe the wooden booms are too bendy? Have you any thoughts on alloy boom sizes?

    Rob and Maren

    David Tyler has already said what I would have. I'd just suggest that for booms (not battens) there is some merit in using a square section rather than round a it makes it easier to fasten things to. However be sure the get a section with rounded corners as some have completely square corners. Not kind to you or the sail.
  • 05 Dec 2011 23:20
    Quote
    Reply # 766553 on 766506
    Anonymous member
    Robert Prince wrote:

    Of the seven mainsail battens, 6 of them are over 5 metres, with the longest being 5780mm. This means sleeving the joints. Ullrich have a UA7410 drawn tube which we used before to sleeve the battens joints. Its a very good fit and like the UA7420 is 1.45mm wall thickness. There is no evidence of bending where the sleeving was situated. What do you think about putting the sleeve the whole length of the batten making a 2.9mm wall thickness for its whole length? This means we could use the existing pockets and all the alloy end caps.

    We like the alloy battens and are amazed how quick they are to repair or jury rig - some sleeving, a hand saw, a battery drill and a pop rivet gun. Could almost be done at sea.

    Rob and Maren

    Two tubes sleeved together are not quite as strong as one tube of the same total thickness, but will be more flexible (think of a leaf spring). However two tubes of higher spec sleeved together will probably be as good as, or better than, one tube of the same total thickness of lower spec – So I'd agree with using UA7410 + UA7420 since it will allow you to leave the batten pockets as they are.
    For the booms, there's an advantage in having a bit of weight. I'd suggest 76 dia x 3 tube.
  • 05 Dec 2011 23:18
    Quote
    Reply # 766551 on 765644
    Anonymous member
    David Thatcher wrote:

    ... I could build them myself as I understood and was experienced in the technology (wood & fibreglass); relatively light weight...

    Hi David

    Your solution sounds great and is probably very durable. However, I have the feeling that we will have to stick with some sort of aluminium battens. Being liveaboards we have neither a section or workshop to carry out the wood work, and I might as well admit it, nor do we have the tools and skill. We are very much looking forward to meeting you at the Northern Rally and to have look at FOOTPRINTS.

    Cheers

    Rob & Maren
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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