Sourcing a tapered aluminium pole in UK

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  • 05 Jan 2020 22:23
    Reply # 8486363 on 3055881

    Hey thanks Asmat,

    i’ll give them a call..


  • 04 Jan 2020 17:27
    Reply # 8474894 on 3055881

    Paul, Aluminium Lighting Company will no longer sell lamp posts for use as masts. Googling around, I've found mallatite.co.uk, who supply tapared aluminium street lighting poles up to 15m tall. Have you tried them?

    Asmat


  • 03 Jan 2020 23:52
    Reply # 8468256 on 3055881

    Hey Guys,

    Thank you so much for the replies, you’ve given me much to think about.

    I’m really looking forward to getting on with it now.

    Mark, all in (including delivery and VAT) the quote was about £1140.

    The next size down - a 10 metre post top column base d 177mm top d 76

    was about £200 cheaper, but this only measured 8.8 metres above the inspection hatch cutout so was too short for me


  • 03 Jan 2020 22:29
    Reply # 8467689 on 3055881

    Hi Paul,

    if we look at the forces at the base of the proposed mast, there will be virtually no bending moment and there will be a shear load of a little over half a ton depending on the sail area set and distance of the C of A above the deck. I am also assuming a bury of about four feet for the mast. The cross section of your proposed mast has a sectional area of about 3.4 square inches and using a value of 20,000 pounds per square inch, this gives a shear strength of over 60,000 pounds, say 30 tons!! I think that it would be fine if you welded in the inspection plate and cut wherever you wanted. I know the welding will reduce the strength of the aluminium by about 40% but that should not be a problem with the loading at the base of the mast and will provide the circumferential strength that is important to stop cracking/bursting at the base. Just drill a hole in the inspection plate to pass your masthead wires through.

    All the best with the project.

    David.

    Last modified: 03 Jan 2020 22:32 | Anonymous member
  • 03 Jan 2020 21:31
    Reply # 8467236 on 3055881

    The bottom couple of feet of the mast is probably out of sight, out of the weather and not in the way of anything, yet easily inspected at any time. And a little bit of bulk and/or a couple of kg of extra weight down there is nothing. If the top 10.8 m is OK then there must be a dozen ways of beefing up the bottom 0.2m. Apart from the other normal considerations, the compromised lower 10” of mast needs to be strengthened so that it cannot crush or stretch in circumference. You then need to consider how it will be stepped.

    In writing: “Make the step as a socket, and the situation should be better, but I still wouldn't trust it” I do wonder if David T is being a little too conservative. David, would there be anything wrong with inserting a nicely fitted 0.4m (say) internal sleeve, or wooden plug, and then (as you suggest) housing the heel in an outer sleeve or socket? This outer sleeve could possibly even be a metal clamp or series of clamps strong enough to resist stretching or opening up around the circumference. Alternatively, a larger diameter piece of aluminium tube for an external sleeve can be packed to fit – or 3mm aluminium sheet folded into any sectional shape will do if fastened to itself and packed to fit. Whatever, the internal plug or sleeve  must resist crushing, the outer sleeve or housing must resist stretching. The mast step itself, which could be part of the solution, must meet all the other usual requirements. I think that is still being careful and conservative.

    Paul, I do feel strongly that if the sail plan is already decided, you should not compromise by shortening the mast. You could, as David suggests, change the sail plan if you think you can’t make the foot of the mast strong enough – but do be generous with your allowance for halyard span at the top of the mast, and paired-downhaul spans between the boom and the deck. Good luck with your split rig, you will like it.


    PS here's another thought: make the mast slightly more than 11m so that the bottom 6" is below the hatch cut-out and comprises the full circumference. Then just sleeve or plug the bottom of the mast up to a point, say, 6" or more above the hatch cut-out (the more the better).


    Last modified: 05 Jan 2020 07:49 | Anonymous member
  • 03 Jan 2020 18:16
    Reply # 8465705 on 3055881

    Paul, 

    well done in sourcing more or less what you wish.  
    Dare I ask how much you are paying

  • 03 Jan 2020 14:20
    Reply # 8464020 on 3055881

    As suggested by others, it's probably an insurance thing that has made them reluctant to talk about using the poles as masts.

    Doubtless if you looked to buy a simple tapered lighting pole from their suggested supplier, they'd sell you one, no problem.

    Just don't mention the word "mast".

    With the generous help available on this forum, you can get the spec right for your order.




  • 03 Jan 2020 13:45
    Reply # 8463769 on 3055881

    Hello David,

    Thanks for the advice, as soon as I can I’ll make a scale model of the rig to get a more accurate idea of mast height.
    Incidentally, I’ve just ordered a sample of Sea Dog’s soft sailcloth which you recommended in another post..

  • 03 Jan 2020 11:56
    Reply # 8463060 on 3055881

    Hello Paul,

    I had a junk rigged Sadler 25 with twin keels, Lliutro, for about 12 years. A great little boat. As far as I remember, the mast was no more than 10.5m overall, a 26ft x 5in dia x 0.128in wall tube with a timber topmast (which wasn't strong enough, I bent it). Your proposed mast tube sounds fine.

    However, what aluminium tubes really don't like is being subjected to bursting loads, as the extrusion process makes for less tensile strength circumferentially. Put in a cutout at the heel, and the situation is worse, if you make the mast step in the form of an internal spigot. Make the step as a socket, and the situation should be better, but I still wouldn't trust it. I'd try to find a way of working within 10.8m, by using a wider, lower sailplan if necessary.

  • 03 Jan 2020 11:11
    Reply # 8462777 on 3055881

    Hi Everyone,

    I joined the JRA several years ago, but have been a spectator up until now,

    this is my first post.

    I own a Sadler 25 (twin keel) which I am about to convert to Split Junk Rig.

    According to my preliminary drawings (following the suggestions Slieve McGalliard very kindly gave me a year ago) it looks as if I’ll need an 11 metre mast.


    I’ve been in touch with Marwood Electrical and they can supply a 12metre (13.7m total height, 12m above ground) aluminium post top column whose dimensions are :-

    Base D 199mm

    Top D 76mm

    Wall 3.5mm at base

    6005a-T6 Aluminium

    Unfortunately the measurement from the top of the access door cutout to the top of the column is only 10.8 metres, which may be enough.

    If it isn’t I’d like to know if it would be acceptable to insert an inner sleeve (made from the discarded length of column) perhaps with a wooden plug as well, to patch the door cutout in order to get the full 11 metres.
    ie- the base of my mast would have a u shaped cutout 200mm high by 100mm wide backed by the inserted sleeve.

    Apologies - I’ve tried to upload the plan of the column but am getting an error message stating the file is too large.

    I’d appreciate your thoughts..


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