Minimum preferred mast height

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  • 27 Mar 2019 02:33
    Reply # 7246938 on 7246671
    Graeme Kenyon wrote:

    For anyone (like me) trying to design (or choose) a suitable junk rig for a conversion, this is a very fundamental question, but I have not seen anything explicit on minimum preferred mast length.

    I would be very interested (and grateful) to read some informed comments on this subject. Or a reference if this subject has already been covered in another thread.


    I think the question of what is the minimum preferred mast length is a bit like the question - 'how long is a piece of string?' It will depend entirely on your chosen sail plan-form and required sail area for the particular vessel. What I will say from experience is that I always wished the mast on Footprints was at least 1.5m higher. This would have allowed a higher aspect ratio sail with possible better windward performance, shorter yard and batten lengths, and would have made it easier to deal with the original weather helm issue. It would have opened up a lot more options than having to stay with the low aspect ratio sail. Her sister ship 'Shoestring' has a mast which is from memory about 2 metres taller than that on 'Footprints'. The reason for choice of a taller mast is that one could then go to the type of sail David Tyler has used on 'Weaverbird' which has a shorter, more horizontal yard. I would not go for a long high-peaked yard again based on the 12 years experience I have had with the junk rig.


    Last modified: 27 Mar 2019 04:25 | Anonymous member
  • 26 Mar 2019 22:40
    Message # 7246671

    In the “S2 6.7 Junk Rig Conversion” thread Scott indicated that he wanted to keep his mast length to a minimum, and this may be one of the reasons why he chose to go with Arne’s planform in his final choice of rig.

    I think it may be conceded that the high-peaked HM planform does allow a somewhat shorter mast than, say, David’s Weaverbird plan, or Slieve’s Split Junk. My question is: how much shorter?

    And a more general question: Once a decision has been made as to sail area and aspect ratio, how is mast length (or, should I say, mast hoist point) decided for any of these planforms? It might seem a dumb question, but in all the written material I can find on this subject, no specific rules seem to have been given – even in Arne’s excellent and explicit scalable standard plans, minimum mast length seems to be missing. The preferred position for the mast hoist point is not shown on the standard sail plan drawings.

    By reading Arne’s work a little more deeply I found that in his recommendation, the mast should be placed to give 10% sail balance (as a starting point) to allow later adjustment within a range of, say, 5% to 15%. Various hints are given in various threads, that halyard drift should not be too short – and by looking at various photographs etc one can infer that with Arne’s rig, the hoist point seems to be at a height of just slightly higher than the height of the midpoint of the yard.

    Looking at photographs of Weaverbird, and of the split junks Poppy and Amiina, it would appear that for these, the mast hoist point is at about the same height or possible even a little higher than the top of the (lower-peaked) yard.

    For anyone (like me) trying to design (or choose) a suitable junk rig for a conversion, this is a very fundamental question, but I have not seen anything explicit on minimum preferred mast length.

    I would be very interested (and grateful) to read some informed comments on this subject. Or a reference if this subject has already been covered in another thread.


    Last modified: 27 Mar 2019 05:27 | Anonymous member
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