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Mast materials and Specifications

  • 02 Apr 2014 01:56
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    Reply # 1529642 on 1306051
    Anonymous member
    I used polyurethane pour in foam. That conduit ain't going anywhere.
  • 01 Apr 2014 23:08
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    Reply # 1529533 on 1306051
    Anonymous member
    I stuffed closed cell foam up mine, but the bubble wrap plus aluminium sounds a great scheme!
  • 01 Apr 2014 20:35
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    Reply # 1529452 on 1306051
    Deleted user
    I once used bubblewrap to stop cable-slap.
    Somewhere I've seen bubblewrap on an alloy foil backing.
    That would stop the slap and reflect radar signals too.
  • 01 Apr 2014 18:31
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    Reply # 1529357 on 1306051
    Anonymous member

    Hi,

    If you stuff some of the mast With aluminum foil from the Kitchen, you will get a very good radar reflector.
  • 01 Apr 2014 03:17
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    Reply # 1528999 on 1306051
    Deleted user
    The taper is about the same as I calculated using the formula in PJR for hollow wood spars, the pole manufactuers probably use the same taper formula from engineering manuals. The main tapers from 13 at the butt to about 6 at the head. I had two extra wraps put on because it was within my weight target but could probably have left them at the standard wall thickness. Whatley uses a proprietary polyurethane coating and when it's time to repaint I'm sure a marine polyurethane like Awlgrip will work well.

    I won't have my boat sailing until sometime in 2015 but when I do I'll report how these masts perform. If others want to try grp masts I think at this point they could reduce the scantlings a little from mine, but I have heard that excessive flex can be a problem if they're too thin, so I would be cautious.

    My only problem is that Whatley is not a mast manufacturer, and they put in conduits that are only secured at the ends. I'm definitely not going to step them with those conduits rattling around inside, so I need to find a way to secure them. I've been thinking of possible solutions like expanding foam, stuffing them with bean bag chair "peanuts", using bubblewrap wadded in, etc. etc. Any suggestions?
    Last modified: 01 Apr 2014 03:33 | Deleted user
  • 31 Mar 2014 22:04
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    Reply # 1528823 on 1306051
    Anonymous member
    Very interesting Robert  Is the shape, much the same you would have for a wooden mast, too. ie a similar taper? Are they finished with a gelcoat or paint?

    I think a lot of people will be watching to see how you get on, so it's good to know that you are happy to post.  If your GRP spars are a real alternative and considerably cheaper than alloy, I suspect you will be starting a new trend. 
  • 31 Mar 2014 16:04
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    Reply # 1528474 on 1306051
    Deleted user
    My new fiberglass masts arrived the other day and I'm relieved to find that they are very stiff, and I'm quite sure that excessive bending or whipping will not be a problem. Since using fiberglass seems to be a bit unusual I had little to go on for scantlings, so I was conservative and used scantlings for hollow wooden masts. The main is 35 feet (10.7m) with a 13-3/8" (340mm) butt diameter, wall thickness at the butt 7/8" (22mm). All 3 of them have a total weight of less than 500lb (227kg). With the mainmast supported at the ends when I sit on the middle (I weight around 105 kg) it bends maybe 10 - 15mm. All in all I'm very pleased and relieved, although I think I might have gotten away with a smaller section. At least this way I'm confident they won't break.

    http://www.junkrigassociation.org/resources/

    [edited to put a line return in the middle of the links, so that the text doesn't bleed out of the frame - DT]
    Last modified: 31 Mar 2014 22:01 | Anonymous member
  • 21 Mar 2014 08:02
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    Reply # 1522059 on 1306051
    Anonymous member

    Jerry

    I've found it difficult to source an ali tube in the UK or Europe.  Like you I emailed and phoned numerous suppliers in the UK and received very few replies.  Those that did reply were either unable to supply more than 3mm wall thickness, had minimum order requirements (Nedal), or thought I was mad to contemplate using their poles in this manner.  Strangely I got no reply from ALC but now I know you have had a positive response I will contact them again. 

    Peter

     
  • 20 Mar 2014 16:15
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    Reply # 1521604 on 1306051
    Anonymous member
    The weight of the complete column is 82 Kg, but I calculated the weight of the bit I wanted (the top 29') at 44Kg. Most of the weight of the original tube is of course in the bottom end, where it has a long parallel section at maximum diametre and is sleeved internally. And of the 44Kg that I was left with, probably more than half the weight is in the bottom quarter to third. It may be worth pointing out too that the top 18" or so of the column is parallel, to take the light fitting, and with 5mm walls. This made it perfect for plugging with an oak plug before through bolting the masthead fitting.

    Roger
  • 20 Mar 2014 14:47
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    Reply # 1521496 on 1306051
    Anonymous member
    Thanks David for the explanation of strength and stiffness relative to alloy grade.

    Sako, I haven't received a drawing of the pole for my boat yet but the one of Roger Taylor's 13.7 metre 199mm x 76mm x 3.5mm lighting column shows a weight of 82kg.

    Brian, I assumed an email carried as much weight as a phone call when it comes to offering business to a company, especially in the current economic climate. Personally I find it much easier to put down in writing exactly what I'm after rather than trying to do it on the phone. Also, having only a PAYG mobile makes lengthy phone conversations a less than attractive option :-)
       " ...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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