help needed re: aluminium tube for mast & battens

  • 28 Jun 2011 23:14
    Reply # 633776 on 630389
    I've just found the discussion on wedges, partners, etc a few pages back  so I'm now a bit clearer on the subject.

    Today I amputated all twelve 10mm stainless studs bonded into my partners that were part of the 'Yeong' arrangement I was planning to use. A messy, brutal task with my big angle grinder, and lots of epoxy fairing needed to fill all the disc cuts in the top surface of the partners caused by removing the studs below flush. But at least I'm now ready for wedging the 4" tube mast.




  • 27 Jun 2011 17:50
    Reply # 632659 on 630389
    I've just ordered the aluminium tube for my mast and battens, all in 5 metre lengths so the offcuts left over after cutting the battens to length should do for a couple of multi-section, spigot jointed emergency spares, easily stowed down below.

    I think I'll go with my original plan of modest sail and short mast, see how it performs, and if I find it needs a bit of turbocharging it would be simple enough to add a wood topmast 'hybrid' arrangement as Annie has done on Fantail, and to add a lower panel to my sail.

    A while ago I was reading on the forum about wedging a parallel tube mast in the partners but I now can't seem to find the discussion topic. Is it necessary to taper both partners and wedges or would a parallel sided partners work OK with the taper only in the wedges? I ask as my previous boat's sheathed wooden mast used the 'Yeong' arrangement as shown in PJR where a ring permanently bonded to the mast fits over a circle arrangement of stainless steel studs or bolts in the partners and is held captive with washers and nuts.

    I've already installed the same arrangement on my 18 footer as I'd planned to use another wood mast but now that I'm going with aluminium tube I'll need to rethink. The partners are 6" diameter so there's plenty of room to wedge my 4" tube, but do I need to give the hole a taper, as suggested in PJR, or would a simple straight sided hole do the job? If the latter I can use a short length of PVC water pipe as a removeable mould to form the correct diameter hole. I'd use epoxy and glass so the wedging surface on the partners would be totally cylindrical and very hardwearing.
  • 26 Jun 2011 23:39
    Reply # 631091 on 631054
    Annie Hill wrote:Hi Jerry - great to have you on board.

    Your Hagar sounds like a very interesting boat, though I'm not sure if Mr Buehler would approve or your using plywood and epoxy!  Your previous two boats are quite different - you obviously like to try something new.

    Buehler's boats tend to be fairly heavy displacement and 130 sq ft seems a bit on the conservative side.  As Arne so often says, junk rig is so easy to reef that you might as well put on plenty of sail area. The top of the mast doesn't weigh much, so another 18" may not make much difference to the ultimate stiffness of your boat while adding substantially to you efficiency - and pleasure - in sailing in light airs.  John Welsford's Swaggie design is a similar boat to Hagar, but carries 247 sq ft on its junk rig.  She is a delightful pocket cruiser and, designed for a builder on the South Coast of Australia - a fairly boisterous part of the world, with a dearth of havens - as a little ship that can stand out to sea and tuck her head under her wing in heavy weather.  Obviously, Welsford is happy that the sail area can be combined with offshore integrity.  Stripped displacement 1200 kg, maximum 1900 kg.  Also hard chine.  You might be interested to have a look at her: www.jwboatdesigns.co.nz/plans/swaggie 

    Thanks Annie and David,

    I'm sure the great man would think I'm a bit deranged building a reduced version of one of his designs; his motto seems to be 'the bigger the better', and as for ply/epoxy, well he'd think I was equally bonkers wasting money on expensive plastic goop!

    However I'm most at home with plywood, glass and epoxy so I suppose it's a case of sticking with what I know best. It's allowed me to make all the sharp edges of normal chine construction nicely rounded with generous radii and large fillets, which as a side  benefit should add a fair amount of extra strength.

    My boat is an amalgam of Welsford's 'Swaggie', Buehler's 'Hagar' and the MacNaughton 'Coin Collection' boats. She has a heavily cambered continuous flush deck from stem to stern, a tiny doghouse with a Hasler pram hood on top, no other hatches and no cockpit.  I I agree that 130 sq ft is a tad 'Chicken' as Arne would say, so I'll fiddle about with the sailplan, perhaps adding the 6th panel of the original Reddish rig to the bottom of my truncated 5 panel sail. I didn't want to make the battens any longer as I'm at the limit of Dmin already for the top panel's sheet span, so it would appear the only way is up. I desperately want to avoid having a boat that sails all over the habour when anchored in a breeze, and also want to maximize the chances of retaining my mast when I suffer the inevitable knockdown, or worse still, 360 degree roll. Hence my tendency towards a low, conservative rig with a short mast, even at the expense of ghosting ability.

    Perhaps I should also mention that I won't be dragging a great big prop around- no engine, just an ash yuloh. The boat draws 2' 9" of which 9" is the ballast casting, so the hull itself is not hugely deep, and I reckon the displacement is approx one ton fully laden which is a good bit less than Swaggie.






  • 26 Jun 2011 22:38
    Reply # 631070 on 630389
    Jerry,
    1 1/4" x 1/8" pultruded GRP tube would be equally suitable. I concur with Annie regarding sail area - a little more would be advisable.
  • 26 Jun 2011 21:44
    Reply # 631054 on 630389
    Hi Jerry - great to have you on board.

    Your Hagar sounds like a very interesting boat, though I'm not sure if Mr Buehler would approve or your using plywood and epoxy!  Your previous two boats are quite different - you obviously like to try something new.

    Buehler's boats tend to be fairly heavy displacement and 130 sq ft seems a bit on the conservative side.  As Arne so often says, junk rig is so easy to reef that you might as well put on plenty of sail area. The top of the mast doesn't weigh much, so another 18" may not make much difference to the ultimate stiffness of your boat while adding substantially to you efficiency - and pleasure - in sailing in light airs.  John Welsford's Swaggie design is a similar boat to Hagar, but carries 247 sq ft on its junk rig.  She is a delightful pocket cruiser and, designed for a builder on the South Coast of Australia - a fairly boisterous part of the world, with a dearth of havens - as a little ship that can stand out to sea and tuck her head under her wing in heavy weather.  Obviously, Welsford is happy that the sail area can be combined with offshore integrity.  Stripped displacement 1200 kg, maximum 1900 kg.  Also hard chine.  You might be interested to have a look at her: www.jwboatdesigns.co.nz/plans/swaggie 
  • 26 Jun 2011 20:56
    Reply # 631039 on 630408
    David Tyler wrote:Hi Jerry, and welcome to the JRA. You only joined a few hours ago, and here's your first posting. You lost no time!
    The JRA used to own an 18ft dayboat, Ariel, and she had a 4" x 1/8" alloy mast. She made some offshore trips with that mast. However, the displacement of your cruiser will be greater, and 4" x 1/4" might be advisable, if you need the space down below. If you can fit a larger diameter with 1/8" wall, that would be better.
    Similarly with battens - 1/16" wall with a greater diameter gives you a lighter, stiffer stronger batten than 1/8" wall with a lesser diameter. I would suggest 1 1/4" x 1/16" for your battens, with something a little bigger for the boom and the topmost sheeted batten, which is more heavily loaded than the others. 
    I'm a fan of low aspect ratio fanned sails for small boats, and apart from some rounding at the head and foot, they don't necessarily need built in camber. It doesn't hurt to add some rounding to the edges of seams in way of the battens, though. It keeps the leech from fluttering.


    Hi David,

    Please excuse my haste in posting. I've been reading the forum comments for many weeks now and thought it was about time I joined the Association and participate properly. I used to be a member several years ago and have a decent collection of past newsletters including the edition containing Vincent Reddish's original article, and the one featuring your very own Tystie, both of which have been a great help when planning my own rig.

    Many thanks for the suggestions on mast and batten dimensions. My boat has a typical George Buehler hull form, ie single chine with a very deep V shape, so relatively tender initially but with a correspondingly easy motion. Although heavier in displacement than Ariel I doubt if the loads would be much greater thanks to this tenderness.

    I'll go ahead and order the tube for mast and battens and get busy with the hacksaw.
  • 25 Jun 2011 23:58
    Reply # 630408 on 630389
    Hi Jerry, and welcome to the JRA. You only joined a few hours ago, and here's your first posting. You lost no time!
    The JRA used to own an 18ft dayboat, Ariel, and she had a 4" x 1/8" alloy mast. She made some offshore trips with that mast. However, the displacement of your cruiser will be greater, and 4" x 1/4" might be advisable, if you need the space down below. If you can fit a larger diameter with 1/8" wall, that would be better.
    Similarly with battens - 1/16" wall with a greater diameter gives you a lighter, stiffer stronger batten than 1/8" wall with a lesser diameter. I would suggest 1 1/4" x 1/16" for your battens, with something a little bigger for the boom and the topmost sheeted batten, which is more heavily loaded than the others. 
    I'm a fan of low aspect ratio fanned sails for small boats, and apart from some rounding at the head and foot, they don't necessarily need built in camber. It doesn't hurt to add some rounding to the edges of seams in way of the battens, though. It keeps the leech from fluttering.

  • 25 Jun 2011 22:32
    Message # 630389
    Hi all,

    I'm currently building an 18ft double ended, long keel cruiser with lines derived from a larger George Buehler design and have finally reached the stage of rig construction. I've drawn up a very modest 130 sq ft 5 panel Reddish sailplan (I particularly wanted a low aspect rig with the shortest possible mast) but I'm trying to decide on mast and batten materials.

    On the Reddish rigged Robert Clark 30ft steel yacht I built a few years ago I used solid European Redwood sheathed with uni-directional glass/epoxy for the mast and 2" dia pultruded glass tube for the battens. The mast took quite a lot of work and before I repeat the process on my little 18 footer I was thinking about using a standard 5 metre length of 4" x 1/4" 6082 grade aluminium tube instead. Any thoughts on whether this sounds about right?

    For battens I'm erring on the side of aluminium tube rather than glass tube or solid wood but should I go for a smaller diameter/thick wall eg 1" x 1/8" or would a larger diameter/thinner wall eg 1 1/2" x 1/16" be a better choice. Batten length is 135" and the sail panels range from 20 sq ft to about 28 sq ft. I'm still undecided about camber vs flat but I do know the Reddish design gives a limited amount of camber in a flat sail through twist alone.

    I'm hoping to do some long distance cruising with my little craft so high performance is less important to me than rig integrity, low forward windage for a well behaved boat at anchor, and keeping everything simple.

    Any advice would be much appreciated.






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