VIDEO: Pango on top of the world

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  • 04 Feb 2020 15:08
    Reply # 8721657 on 8705299

    Your sail looks really great. Thanks for the video.

  • 04 Feb 2020 04:20
    Reply # 8720091 on 8712139
    Anonymous wrote:

    I wonder,
    has the actual, resulting camber in the lower panels of Pango’s sail been measured? I am asking because I wonder if a general rule of thumb has been established to find the ratio between the ‘camber’ of the half-lenses and the resulting camber in the panel.

    On my sails, the max rounding of the barrel curve is roughly 55% of the resulting camber I aim for. However, this varies a bit with varying ratio between height (P) and width (B) of each panel. That’s why I found ‘the chain calculator’ to be useful.

    Arne

     


    Have not measured it but I have found on average, maximum camber on a shelf foot sail is about 2% more than the calculated camber. So if I want a 8% sail I use 6% and 8% for a 10% sail and so on. However it is not an absolute measure as the width of the panel also effects the outcome (wider panels tend to develop more camber) so one needs to use a little judgement gleaned from experience. I don't loose sleep over it as I'm not building sails for an America's Cup boat. Should I bother to measure, it's more to satisfy my curiosity than anything else. Also the narrower panels and lower aspect ratios tend to make the camber appear more dramatic than it's actually is.

    Over all, I'm pretty satisfied with the sail on Zane's Pango, the boat is fast and weatherly. Despite Zane's lack of experience, he has done well.

    Last modified: 04 Feb 2020 04:22 | Anonymous member
  • 03 Feb 2020 09:30
    Reply # 8712139 on 8705299
    Anonymous member (Administrator)

    I wonder,
    has the actual, resulting camber in the lower panels of Pango’s sail been measured? I am asking because I wonder if a general rule of thumb has been established to find the ratio between the ‘camber’ of the half-lenses and the resulting camber in the panel.

    On my sails, the max rounding of the barrel curve is roughly 55% of the resulting camber I aim for. However, this varies a bit with varying ratio between height (P) and width (B) of each panel. That’s why I found ‘the chain calculator’ to be useful.

    Arne

     


    Last modified: 04 Feb 2020 20:56 | Anonymous member (Administrator)
  • 03 Feb 2020 08:01
    Reply # 8712098 on 8705299

    Just to add a little more to the very clear explanations by Graeme and Ueli:

    The 90˚ shelf is actually as easy to plot and cut as the barrel cut of Arne's methods, as the panel is a simple quadrilateral and only the shelf or lens has a convex curve to be plotted. The one down-side is that it does put a little too much extra cloth in, which has to be lifted and inflated in light airs.

    Which is why Slieve came up with the 45˚ shelf, and a spreadsheet method of calculating the offsets (the panel has a concave curved edge, and the shelf or lens has a convex edge).

    To get a good combination of ease of calculation with effectiveness, a 60˚ shelf or lens works well. A 60˚/30˚ triangle has sides in the ratio of 1:2:root 3. So the panel can have a concave curve with an offset of 1 unit, to match a shelf or lens with a convex curve with an offset of 2 units, at any point along them. Not quite accurate as regards depth of camber, but we're talking sailmaking here, not precision engineering. The middle of the panel will belly out from the theoretical 1.732 (root 3) units to 2 units - 2 units being equivalent to the aimed-for camber at any point. Also, it's easier to baste and sew a seam with these two curves than with a curve and a straight edge. This method of calculation also works with tucks and broad seam, which extend into the convex edge of a panel twice as far as the amount of that convexity.

    Last modified: 04 Feb 2020 07:53 | Anonymous member
  • 03 Feb 2020 04:49
    Reply # 8712015 on 8705299
    Anonymous

    Yes to be clear as touched on by Arne, the mastery of my sail is due to the expert hand of Paul Thompson.
    I wouldn't know the difference between 'Shelf Foot' and 'Big Foot'.

    Once I get a few teething details sorted out on my rig,  then Im really looking forward to see what I can get out her as I feel PANGO can go even faster than she did in the Tallships.  Bryan from FANTAIL reckons my sail "pulls like a train".

    I also encourage other junkies to take video and post it up on youtube if you feel so inclined.  I have received a lot of private email messages of support via Youtube from non junkie people about how they love the look of my sail.  Can only be a good thing for junk rig.

    But, I do realise social media outlets like Youtube are not everyone's bag, so each to their own.

    Last modified: 03 Feb 2020 04:53 | Anonymous
  • 03 Feb 2020 04:04
    Reply # 8712002 on 8705299

    hi mark

    the 'shelf foot' is a piece of sailcloth added at the top and bottom of the panels to define the profile of the sail (to connect the profiled sail to a straight batten…)

    sometimes the part added at the bottom of a panel and the one added to the top of the next panel downwards are made of one single piece of cloth. this is often called 'lens cut' because of the lens shape of those double profiled elements. but in fact it's still a shelf foot.

    ueli

    edit: graeme was faster.

    Last modified: 03 Feb 2020 04:05 | Anonymous member
  • 03 Feb 2020 03:53
    Reply # 8711985 on 8705299

    Mark: I'm not the most qualified to discuss sailmaking but I'll chime in here because I happen to have a photo of Zane's shelf-foot sail and the coloured cloth shows the "shelfs" quite well.

    Each of the sail panels is made from three parts: the central main part of the panel, which is black in the photo - and two "half-lens-shaped" parts, one at the top and one at the bottom of each panel - you can see the "half-lenses" here (light grey) at the top of each panel - the ones at the bottom of each panel are obscured - apart from the one at the very bottom panel.

    These "half-lenses" or "shelfs" are straight where they are attached to the horizontal spars (the so-called battens) - and curved where they are stitched to the (black) main body of the sail panel. This results in the aerofoil shape you can see which is built into each of the panels of this sail.

    The "shelfs" in this case are designed to be at 90 degrees to the sail, though in practice the sail cloth is soft and the shelfs curve down somewhat into the belly of the sail when it is filled, rather than standing out stiffly at 90 degrees like a shelf would, if it were made from plywood. Some people prefer "45 degree shelf foot" - the shelfs are then (in theory) designed to stand at 45 degrees to the sail, which is said to inflate a little more easily in light airs.

    Its not the conventional way to build shape into a sail, but it does (I think) rather suit the panels of a junk sail quite well - though it is by no means the only way to build a successful cambered junk sail. 

    Why is it called "shelf foot?" Like a lot of junk terminology the term has been borrowed from traditional sailing vocabulary and is a slight misnomer. If you look closely at a conventional bermudan sail you will sometimes see, along the foot of the sail, this same half-lens-shaped component which is called a "shelf foot", and which helps to put camber into the lower part of the bermudan sail. On a junk rig "shelf foot" sail you will see this half-lens-shaped component not just at the foot, but at the top and bottom of each of the sail panels.

    edit: Ueli was more concise!



    Last modified: 03 Feb 2020 05:03 | Anonymous member
  • 03 Feb 2020 01:17
    Reply # 8711885 on 8705299

    TO Annie hi, can anyone explain to me by what is meant by 'shelf-foot' method when it comes to sailmaking.  Also in Sydney Australia are their any other junk rig fans who might just be able to show me a bit about sailing a junk-rigid boat. I'm currently finishing off an eight foot lug-rigged mini cruiser design called 'Ocean Explorer' by Michael Storrer & hope to be out sailing soon in her  but would love to start learning more a bout the ins & outs of Junk sailing. Regards Mark

  • 02 Feb 2020 20:06
    Reply # 8711423 on 8710909
    Arne wrote:Sooo, IMHO, the best construction method is the one you can ... manage yourself.
    And the most satisfying :-)
    Last modified: 02 Feb 2020 20:07 | Anonymous member
  • 02 Feb 2020 09:01
    Reply # 8710909 on 8705299
    Anonymous member (Administrator)

    Well..

    I surely agree that Pango’s sail looks great, even spectacularly great with the contrasting colours. It may even be faster than sails with camber achieved in simpler ways, but it comes at a price: It requires more skills and workspace than, for instance my amateur methods. Not everyone has a Paul Thompson or Chris Scanes around who can do it for them. For professional sail makers, I am sure the shelf foot method will move up to be the standard, at least in the lower panels with a lot of camber. I see nothing wrong in that.

    Still, most junkies are more or less forced to make their own sails, both for economic and logistic reasons.

    Sooo, IMHO, the best construction method is the one you can afford to buy, or can manage yourself.

    Arne


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