Time to get junk rigged!

  • 20 Oct 2013 14:18
    Reply # 1417154 on 1414460
    Thanks for all the reponses so far!

    David, the main dilemma for me with a hybrid mast is that building it during the winter would require a workspace which I unfortunately don't have, so it would overlap with the other modification projects I have planned for the boat[1] in the spring, from April forwards, all of which will keep me from sailing next summer. My current long-term plan is to sail locally (around the Baltic) during summers 2014 and 2015 and be ready for a longer voyage from 2016 onwards.

    If I had access to a warm large space during the winter where I could build the mast and cure epoxy, an alu/wood hybrid would be a more attractive choice. With a tapered steel pole construction is simple and fast, basically a matter of finishing it and building a masthead fitting which shouldn't take much time. And it's slightly less expensive than a hybrid.

    If a 10 meter hybrid mast would be in the 70 kg ballpark and we add 30-40 kg for sail/battens/yard, we're looking at 100-110 kg for the hybrid vs 120-130 kg with steel. Not a huge difference, even if weight aloft (or lack thereof) is important. Or..?

    In any case I don't need to make a final decision right now. I will construct the sail during winter and if I can get a hold of a warm space to build a hybrid mast I'll consider it, otherwise I'll just go with steel. I can always upgrade later. In a perfect world I'd prefer an all-aluminum mast but that will have to wait until I'm somewhere in the world where tapered aluminum poles are more readily available.

    By the way, I'm curious as to why you think a half-barrel shape would be better than a straight taper?

    Arne, the rig has to be offshore-capable.

    Bottom line: Yes, a steel or solid wooden mast is on the heavy side and probably suboptimal, but it will most likely have to do for now. The general opinion here seems to be that it will work all right for my boat. And reading the discussion about heavy masts[2] it might even be somewhat of a Good Thing.

    [1] Spring 2014 projects: Last spring I built a double berth in the forepeak and now with the junk rig it's going to be ruined with a mast in the middle of it, so I'm planning to build a new one behind the companionway stairs, which requires shrinking the cockpit footwell and raising the bridgedeck. I also did a hasty bottom job to be able to get the boat in the water as soon as possible and it will likely need to be redone. The deck will also need a bunch of work to accomodate the JR mast; reinforcements, partner, move the hatch, etc.

    [2] Why try for a light mast (stability, mast weight and rolling): http://junkrigassociation.org/technical_forum?mode=MessageList&eid=1313268
  • 20 Oct 2013 10:58
    Reply # 1417110 on 1414460
    Anonymous member (Administrator)

    Stavanger, Sunday

    I agree with David that the light hybrid mast is an attractive alternative. However. The Fingal 27 is a whole number bigger than the Contessa 26:

     

    The Fingal’s displacement starts at 3000kg and her lead ballast is 1.250kg, while

    the Contessa’s displacement starts at 2400kg and has a ballast of  only 1043kg.

     

    Actually it is remarkable that Mariposa coped as well as she did with her 120kg rig. I bet she felt sluggish, just as my 1400kg Malena did with her first 80kg+ mast.

     

    Moreover, if I got my sums right, that suggested 6” * 1 /4” aluminium tube has a yield strength of about 2600kpm, against about 3200kpm for that 188mm/90kg steel mast.

     

    In my view, the Fingal 27 is closer to my Johanna (3000kg/1400kg) in righting moment, so that 6” aluminium tube seems to be on the weak side to me. But of course, that depends on what kind of sailing Oscar plans to do.

     

    Cheers, Arne

    Last modified: 21 Oct 2013 08:58 | Anonymous member (Administrator)
  • 20 Oct 2013 10:35
    Reply # 1417106 on 1414460

    Oscar

    As David mentions above, I am in the process of replacing my solid wooden mast due to the weight.  Several 'hybrid' masts have been built and Arne recently did a write up of his.  In a previous magazine (not sure which issue) there is an article written by Annie about her hybrid mast.  I've found it fairly straightforward to source the section of aluminium required, and I estimate the total cost of my new mast will be around £500.

    Peter

  • 20 Oct 2013 03:30
    Reply # 1416993 on 1414460
    I recently discussed with Peter Scandling the possibility of replacing Mariposa's 120kg wooden mast, which we agreed is far too heavy for a 26ft GRP boat, with a hybrid mast.

    I made calculations of weight as follows:

    A PJR-spec hollow mast would have a top dia of 9.5 cm, and dia at deck of 23.25, for LAP of 8m and SA of 34.5 sq m. Allow 10% less diameter for a solid mast, which would be 8.55cm at the top, so Mariposa's mast, at 7.8cm top diameter, is definitely under-sized by any reckoning, yet still overweight.

    The best form for a wooden topmast would be half-barrel shaped staved construction.

    With wall thickness of 20% of tube diameter 15.2cm = 3.02cm, and top dia of 9.5cm, length 445cm ( to allow for 45cm bury in the tube) and Douglas Fir at 35lb/cu ft, I calculate the topmast weight at 15kg.

    I calculate the weight of an alloy tube 5m x 6"dia x 1/4" wall at 39.2kg

    Add an estimated 10kg for glass, epoxy, conduit and a head fitting, and it comes to 64kg.

    This is what I would recommend, Oscar. I think it's rather unfair to be asking a 27ft GRP boat of moderate displacement to carry the weight of a solid wooden mast, or a steel mast.

  • 17 Oct 2013 23:34
    Reply # 1415315 on 1414460
    Deleted user
    OK Oscar, good. I mentioned it partly to bring it to peoples' attention again.

    When Lesley and I get the new JRA members' Projects Forum going - hopefully this weekend - one of them will be asking for a 'volunteer' to update it by comparing what's in it already with what's been added to members' profiles since it was published.
  • 17 Oct 2013 22:53
    Reply # 1415290 on 1414460
    Ketil, as suspected (and unfortunately) the price of a carbon fibre mast is in a whole other ballpark. Given that 90 kg isn't that excessive (even if CF would've been around 45) I'm going to settle for steel.

    Paul, the pole is already hot dip galvanized. Good pointers on dampening the sound, I'll be sure to do that.

    Brian, I've checked the mast database but there weren't many entries of steel masts (especially on wall thickness). I'll be sure to fill in all the details of mine when I'm done. :)

    And Arne, thanks!
  • 17 Oct 2013 21:55
    Reply # 1415241 on 1414460
    Deleted user
    Oscar, don't forget members produced a mast database which you can download via that link. You can also access it through Junk Information > Useful Links > Sails, Masts and Gear.
  • 17 Oct 2013 19:39
    Reply # 1415123 on 1414460
    Oscar, the 188mm mast will be more than strong enough. The 3mm wall is also ample (but do not go thiner for reasons of corrosion resistance and also impact resistance) however because margins for corrosion are low, I would urge you to get the mast hot dipped galvanized. That will ensure the mast is protected both inside and outside. Be sure to weld caps on both ends (to seal it) and also fill the mast with polystyrene balls or polyurethane foam (or something of that nature) else the mast will ring like a bell when your halyards tap it. You can then finish the job with a couple of coats of epoxy and two coats of polyurethane for the top coat on the outside, no need to do anything further for the inside.

    I have used steel masts in four of my rig designs now, one of which is Aphrodite (48ft junk schooner used to be owned by JRA member Carl Bostek) another  gaff rigged cutter (Archimedes 42ft) and my own boat La Chica a 32ft junk rigged schooner (and also in her previous incarnation as a gaff ketch). I have found them quite satisfactory. There are photo's in my profile gallery (just click on my name under the photo to get there).

    If you need more information or assistance, post here or feel free to email me directly. My email address is in my profile.

    Last modified: 17 Oct 2013 23:24 | Anonymous member
  • 17 Oct 2013 18:00
    Reply # 1415035 on 1414460
    Thanks for the tip, I just emailed him. Although I doubt that the price will be anywhere near the quote I got for the steel pole.
  • 17 Oct 2013 17:26
    Reply # 1414996 on 1414460

    Hi Oscar,

    Have you gotten a figure from Rudolph vd Brug of the cost of a carbon fibre mast?

    It might be less expensive than you think.

    Regards

    Ketil

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

                                                              Site contents © the Junk Rig Association and/or individual authors

Powered by Wild Apricot Membership Software