Aluminium Batten specs

  • 28 Nov 2012 10:43
    Reply # 1147672 on 1056315
    I'll save that info Gary, thanks.
  • 28 Nov 2012 09:52
    Reply # 1147656 on 1056315
    Deleted user
    (Moved this from other thread)
    Did some number crunching comparing different tubes available in my neck of the woods.
    Calculated deflections of a batten supported both ends with 5kg placed in the middle.
    (Using formula from this site)
    I realise a JR sail doesnt exert point load only at the centre of the battens, but this gives a comparison between different batten specs.

    Alloy, temper, length, OD, Wall, weight - Deflection

    6060 T5, 4.4m x 40mm x 1.6mm, 2.3kg - 36mm
    6060 T5, 4.4m x 44mm x 1.6mm, 2.5kg - 27mm
    6106 T6, 4.4m x 38.1mm x 2.0mm, 2.7kg - 35mm
    6060 T5, 4.4m x 44mm x 3.0mm, 4.6kg - 16mm

    The bottom one is the stiffest, best choice for upper battens.

    But when you consider the yield stress of the T6 is ~ 210MPa and the T5 is only ~110MPa, that 38.1mm dia T6 tubing is almost the same "strength" as the bottom tube, just bendier.

    The batten David Thatcher mentioned:
    6060 T5, 6.5m x 63mm x 1.5mm, 5.1kg - 30mm
    But because bigger sail area its more likely the loads would be bigger too, even if there are a couple more battens to share the load.
    Last modified: 28 Nov 2012 10:59 | Deleted user
  • 26 Nov 2012 20:59
    Reply # 1146320 on 1056315
    I recently heard from Paul Fay. He was looking into the possibility of using aircraft spec 7075 alloy, which is very much stronger than the 6000 series alloys. Yes, you can get 7075 tube, but it has to be made especially to order, and it would cost as much as the boat is worth... Even CFRP doesn't cost that much.
    Oh well, we'll have to stick with 6000 series alloy, CFRP and pultruded GRP, timber and bamboo.
  • 26 Nov 2012 19:44
    Reply # 1146274 on 1056315
    There's more on this topic in Bamboo and Aluminium Battens.
    Last modified: 26 Nov 2012 19:46 | Anonymous member
  • 27 Aug 2012 03:04
    Reply # 1057294 on 1056315
    Comparative data from another boat - mehitabel's mainsail battens:

    4.9m long, 37mm diameter x 3mm wall and not hard tempered.
    Sail area is 41sqm. 6 panels, all flat-cut.

    The top batten is or isn't sheeted, and is double (batten both sides of sail instead of a backing batten one side. (foresail same)

    Before doubling the top batten, the top and boom battens took on slight bends, easily straightened, in very hard use one season. (I think I could have avoided the top bending if I'd watched better and tensioned the sheets less, especially hove-to. The boom batten had too much strain on the tack-line, now improved.)

    I consider them good enough, but a few seconds of bad sail-handling in enough wind could break them and punish me.

    Last modified: 27 Aug 2012 03:09 | Anonymous member
  • 25 Aug 2012 15:18
    Message # 1056315
    Arion has 38 x 3 mm alloy battens, 4.6m long, supporting a 35.7 sq m sail.  Robert Groves uses 25 x 3mm alloy tubular battens on Easy Go but once again I think his flat sail places lesser stress on his battens.  When my yard broke the top three battens bent.  The top, unsheeted batten bent the most and the third batten down also bent a lot.  For some reason the top sheeted batten, (second batten from the top) which also extends beyond the leech by 400mm, bent the least.  When I got into port I straightened them using the marina walkway railings as a fulcrum and was surprised by how much force was needed to bend them straight.  I think it is unlikely that these battens would bend under any circumstances other than yard failure, though I think a really good boltrope on the leech in particular and on the luff of the sail is important to spread the load in squalls.  I don't have any experience with wooden battens but Alan on Zebedee told me that if you can stop the top two battens breaking you wont break any others.  He made them heavier.  For a medium to heavy displacement cruising boat I think it makes sense to accept the weight penalty as a trade off against reliability.  It is also a relatively cheap solution and the components are easily repaired or replaced.  For performance cruising and racing, the criteria and therefor the solutions will be different. 

    Last modified: 26 Nov 2012 19:43 | Anonymous member
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