Conversion - could you/would you?

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  • 24 Nov 2017 15:20
    Reply # 5600105 on 5600005
    Webmaster JRA wrote:

    Phil

    You can read more about Paul's aerojunk rig in Magazine issues 61-66.

    Chris

    Thanks Chris, that's making good reading, have started with the issue 61... but couldn't help but read pretty much every other article in it too! :)

    Phil

  • 24 Nov 2017 12:03
    Reply # 5600005 on 5595959
    Anonymous member (Administrator)

    Phil

    You can read more about Paul's aerojunk rig in Magazine issues 61-66.

    Chris

  • 24 Nov 2017 09:31
    Reply # 5599932 on 5599750
    Paul McKay wrote:

    Yes Phil, I would too. Your boat is not so different to mine - an Etap 23i. As it happens I have just finished my AeroJunk Folio, apart from a couple of photographs next spring. The Folio shows you where the mast might go and how to design your new sail. If you send me your email address I’ll send you a copy. Best wishes, Paul McKay

    Thanks Paul, that's a great offer of help - I like your design, some more info as to how it tensions, reefs, where the stiffness needs to be in the battens (I imagine there's a better name for these as they're more than that) etc will be great. And of course I'm very pleased to see that you're doing this on a boat so similar in many ways to mine. Have already got images in my head as to building a jig and playing with a few different materials to get these made up :) But have lots to understand and answer before I get the work bench cleared & tools out!

    Phil.



  • 23 Nov 2017 22:03
    Reply # 5599750 on 5595959

    Yes Phil, I would too. Your boat is not so different to mine - an Etap 23i. As it happens I have just finished my AeroJunk Folio, apart from a couple of photographs next spring. The Folio shows you where the mast might go and how to design your new sail. If you send me your email address I’ll send you a copy. Best wishes, Paul McKay

  • 22 Nov 2017 22:00
    Reply # 5598909 on 5595959

    Ok, have ordered the book, I like the Aerojunk design that's been mentioned - very elegant, and am taking in the advice, I'll need to feel pretty confident that Zigzag would make a full recovery from her surgery - but a junk rig Django could be a great little lifting keel cruiser I think.

  • 22 Nov 2017 21:09
    Reply # 5598843 on 5597526
    David Tyler wrote:. Are you planning on club racing in Poole Harbour? If so, you should go and see the split junk rig on Amiina. Edward Hooper has it as his main aim to develop a form of the rig that can compete on equal terms against the pointy-tops, and puts in very creditable performances in the Round The Island Race. 
    Another option would be Paul McKay's Aerojunk, for four reasons: it has a lower top weight than a conventional junk; it is adjustable in the proportions of sail area in the two sections that allow the centre of effort to be moved to a greater extent and, in general, to allow a mast position further aft; it is, on the basis of the evidence Paul has provided, highly efficient to windward as a result (presumably) of the slot effect, and, finally, when executed to Paul's designs, is an extremely beautiful profile that may look more appropriate on a contemporary hull design than the other JR alternatives.
  • 22 Nov 2017 20:43
    Reply # 5598830 on 5598732
    David Tyler wrote:

    To help you towards answers to your questions, I'd better hand out the usual advice we give to newbies - get hold of a copy of Practical Junk Rig. We've moved on a bit since it was published, but there is little actively to disagree with.

    And might I suggest that you go to the Home page, read Get Started and study Arne Kverneland's 'Junk Rig for Beginners', to help you understand things like mast placement.

    Sounds like a great boat for JR.

  • 22 Nov 2017 19:58
    Reply # 5598792 on 5598532
    Phil Clough wrote:


    Am avidly enjoying the adventures of RT in Mingming at the moment, though I think he'd scoff at my little plastic duck of a boat :)


    There is much to be said for 'little'.  There is much to be said for 'plastic'.  

    And I don't think that any JRA member would 'scoff' at what you are considering;  it sounds very exciting.   

  • 22 Nov 2017 18:29
    Reply # 5598732 on 5595959

    To help you towards answers to your questions, I'd better hand out the usual advice we give to newbies - get hold of a copy of Practical Junk Rig. We've moved on a bit since it was published, but there is little actively to disagree with. It goes through the whole design process, but just to get you started, the mast for a split junk rig is often close to the bermudan position, but it depends on the amount of area that is put forward of the mast. The best windward performance is claimed when the balance is as much as 33%, but I'm uneasy about using so much in a cruising rig, so the mast might be a little ahead of the bermudan position. For a conventional junk rig, it's quite well ahead of the bermudan position. A boat like the Django 6.7 is going to have its centre of lateral resistance very close to the centre of that narrow keel foil, and the lead that we use for the centre of area of the sail is about 10%. A sail like mine, of moderately high aspect ratio and a low angle to the yard, has its centre of area at about 50% of the chord. 

    Looking at the Django 6.7 tech spec, I see that the sail area is positively vast - a main of 18/22 sq m (depending on whether it's a flat top?) and a headsail of 15 sq m. I have 22 sq m total, and find this to be quite enough for cruising, on a boat a little heavier than yours. In fact, I'd be quite happy to use the design of my rig, as it stands, on Zigzag. My mast is at 18.5% of the waterline length aft, but 20% might be better - the helm balance is perfect, but maybe some people might consider it too perfect :-)

  • 22 Nov 2017 16:24
    Reply # 5598532 on 5595959

    Thanks chaps, I'm liking the initial positivity. I'm not averse to a little risk - in fact I rather relish the challenge. Mostly I'm concerned that it simply couldn't work for some boat design reason, but why that should be I can't think. I can already see that there is a great deal of knowledge on here and if I bite the bullet and go for it then I'll need quite a bit of technical advice. To start with - it will only work if I can get the mast placed correctly - but where is that, is it the same as a BR or further forward maybe? Then sail area, am I aiming for the same in a fully set JR as the designed combination m2 for my std rig... and then let that therefore dictate the mast height above deck? So much to learn! But that's fun.

    As to my aspirations, the truth is I get a few weeks a year to go adventuring alone, what little solo sailing I have done I have loved & I've got a boat the currently I'd be happy to take away for decent chunks of time - so a bit more than Poole bay sailing, but not quite ready for Biscay or the Atlantic.

    Am avidly enjoying the adventures of RT in Mingming at the moment, though I think he'd scoff at my little plastic duck of a boat :)

    Tapered ally might be ideal then (maybe I could persuade them to sell it to my business? we sell construction materials, so maybe half way there... am happy to try for others here if that is useful, no promises, but it might work? 


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