New low-cost "hardware store" racing class; input on proposed rules

Discussion in 'Sailboats' started by Petros, Mar 19, 2012.

  1. Sailor Alan
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    Sailor Alan Senior Member

    This one is easy. The laser rig can be let out to the point where its boom, and sail, is forward of the beam, and at this point, with the apparent wind, 'by the lee', the air is flowing 'correctly' across the sail. The air in this case, accelerates around the mast, then flows across the correctly cambered sail, producing maximum lift even at quite minimal apparent wind speed.

    With the boom/sail set exactly across the apparent wind, (as in a rig with stays), the turbulent air set up immediately behind the sail creates a fairly static pressure with little differential from that on the front, hence little thrust. As soon as this air on the leeward side of the sail moves, lower pressure appears and the sail develops thrust. In a typical situation, the apparent wind is divided by the leech (which itself develops turbulence) and, because it is a single skin, limited pressure differential, flowing ‘backwards’ across a camber set up for air flow in the opposite direction. Air does not like being divided by a thin edge at these air speeds, though classically it is microscopic vibrations of this edge that is doing the damage. A bulged leading edge, like a mast, or jib foil, should fool the air into thinking the area behind this edge has camber. In fact, over-rotating you jib furling foil should give improved lift to windward.

    In the case of a boom and sail let out until the apparent wind is flowing 'correctly' i.e. mast first, across the sail, the leeward air is more stable, following a camber with its belly forward, and therefor developing more pressure differential, hence more thrust.

    Likewise, rolling such a boat to windward in very light air, will simultaneously reduce the WL beam, the displacement stays the same, giving a better L/B ratio, and raising the sail area such that it presents a ‘square’ upper edge as high as possible above the earths boundary layer. Every little bit helps.
     
  2. Sailor Alan
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    Sailor Alan Senior Member

    This suggests a far aft mast rig. Assuming the 'main' sail was a wing sail, you still need the jib. Having the 'perminant' sail so far aft may lead to handeling issues as the wind increases in force. The jib could be roller furled, but how would you handle the wing main unless you simply roll the boat over in a blow. There are some cunning 'wing' sails out there with aluminium extrusion 'battens' and sailcloth skins, with or without movable TE's. Some presumably work, but they are not at all common so far.

    Any sail with a raked LE loses effectiveness compared to one with a near vertical LE, and in this case the jib will have a poor Aspect Ratio too, nearing unity.

    Though its total lift will be slightly poorer than a jib with a steeper LE, its angle of acceptance will be much better, avoiding a stall, and maintaining good lift over a wide range of air-steam entry angles. As a sail, by definition, can change its angle of acceptance, by sheeting in, or out, this is probably of little consequence.

    One point often overlooked, a sail with a shallow LE has a significant vertical lift component, and this can be significant. It will tend to lift the front of the boat, operating through the CP of the jib.

    Possibly the greatest development class of all, the Sydney 18's, nearley all use flat topped mains, smallish jibs, and large asymmetrics with quite raked LE's for off the wind. They clearley get plenty of lift too. Some are apparently experimenting with two crew, and this continues a trend, from whole rugby teams, to 4, then 3, and possibly 2 crew. If allowed, foils will be next i suspect.
     
  3. CT249
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    CT249 Senior Member

    Thanks for the info, Alan.

    Re "The laser rig can be let out to the point where its boom, and sail, is forward of the beam, and at this point, with the apparent wind, 'by the lee', the air is flowing 'correctly' across the sail. The air in this case, accelerates around the mast, then flows across the correctly cambered sail, producing maximum lift even at quite minimal apparent wind speed."

    When sailing by the lee in a Laser, the airflow goes from the leach to the luff, so it doesn't accelerate around the mast and flow across the sail.

    Re "Some are apparently experimenting with two crew, and this continues a trend, from whole rugby teams, to 4, then 3, and possibly 2 crew."

    18s have had a minimum of three crew since the late '80s. The two handers performed well at times but could not beat the 3 handers consistency, or when the latter went to wider wings. The 2-handers were already at the limit of difficulty with 25 foot wide wings so they could not extend any further. The two handers were later banned; whether it was to enhance the racing or because of conservatism depends on your point of view.

    The significance of the two handed saga, and 18 Foot Skiff rules in general, may be that they show how difficult it is to run a development class and how easily very good and innovative people may hold opposing ideas about rules.
     
  4. CT249
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    CT249 Senior Member

    Nice to know others have noticed the same usage.
     
  5. tdem
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    tdem Senior Member

    They are basically a one design hull with very restricted sailplan now, but they did evolve to this shape. Not exactly hardware store racing budgets though :)

     
  6. gggGuest
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    gggGuest ...

    Interesting theorising. But they sail with the flow from "leech" to "luff". See here for a respected coach explaining how to do it. http://www.roostersailing.com/articles/4TH DIM WEB ARTICLE.HTML

    It won't. Sure it will produce an upwards lifting force on the boat, but the sail will still pitch down the bows. It has to - the power is produced several feet above the hull where all the drag is. If the sail actually lifted the front of the boat you'd see crews shifting weight forward in a gust to keep the bows down. This myth was exploded a good many years ago now: see http://www.wb-sails.fi/Portals/209338/news/95_12_Cherub/Cherub.html
     
  7. TwoManyHulls
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    TwoManyHulls FlyingHulls

    This is a great idea, and I would love to design to it. I think the mast length limit is reasonable, but I think there should be a floating depth limit as well. One of the strengths of the idea would be the regional nature of it. In Puget Sound, all of the boats would probably have a traditional pointed bow, but here in the Midwest many would be scows.

    It will come as a great surprise to many on the list, but you can build a lighter mast and spars out of wood than you can buy in aluminum, and you don't need epoxy to do it. You can build"bird's mouth joint" spars using Type III Tightbond-type glues and they will last for years.

    I agree that the sail material is a big factor, and Tyvek is a good option. If you limit the material to a certain cost per sq ft that should solve that problem and weed out the expensive alternatives.

    How do you account for scrounging? I have been served well in both boat and house materials by scrounging. Perhaps you have to value it as a factor of new; 30% of the new price, for example.

    I agree that $300 is too low. $500 is more reasonable, $750.00 would make durable boats, I think.
     
  8. Sailor Alan
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    Sailor Alan Senior Member

    Welcome to the discussion 'TwoManyHulls.

    There are at least 4 boats being built to the curent rules, including keeping under $600US, as we speak. All so far have pointy bows, but we (our team) did discuss scows during our initial critical design review (several of us are ex moth sailors).

    One of our teams boats has hull planking complete, and i started my mast today as well.

    We have another boat being built entirely from recovered/recycled materials, i.e. basically no out of pocket expenses at all. The rules state we must cost this as if the material was new, but an interesting excercise reveled that current cost of recycling, i.e. dump fees etc, meant this boat would cost negative money, i.e. it was cheaper to build it than to throw the wood away?

    This will be a challenge to cost out, and should provide much discussion, and possibly another new class, the completely recycled boat.

    I notice Bahama Sloops using old advertising banners for sails, perhaps a similar approach here might work.
     
  9. TwoManyHulls
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    TwoManyHulls FlyingHulls

    Is there a link that shows the rules as you guys are designing to them? I have been trying to find a statement of the entire rules in this thread, but, other than the first post, haven't found anything definitive.

    Also, any design drawings or renderings revealed?
     
  10. Sailor Alan
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    Sailor Alan Senior Member

    Here are the rules, from page 37 (i think).

    Here is a rendering, screen shot actually, of my proposed design. Roughly 14' LOD, 5' BOA, 16' LOA, 20' mast from the deck up, about 125 sq/ft plain sail.
    Keeping under $600US, and under the weight stipulated (by me) is a serious challenge, but i am making my own sails, as well as the hull, oars, and empenages.
     

    Attached Files:

  11. Petros
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    Petros Senior Member

    For this first go around I am thinking to allow 7 ft beam overall. It will make a better sailing boat, and not affect porablity much since it is sell well under the 8.5 road limit.

    Sailor Alan, you do not have to make your own sails if you do not want to, it is only the material costs that count. One stipulation however in the rules, is that they be made in a manner that is typical of a well equipped home shop. So that would mean assembling the sail with normal tools, sewing machine or glue, hand stitch etc. No exotic seamless molded non-woven reinforced sheet goods as sail cloth.

    Most of my boats are often made with salvaged materials, and I will use some for this build as well. But the material cost rule is a means of keeping the "measure" the same, so it does not become a contest for who can salvage the best materials. IOW, salvaged and resawn lumber would be okay, but getting lots of carbon fiber from the trash bins of a textles plant would not. The idea is that your materials need to be available to all contestants to make it a fair contest.

    I like the idea of allowing salvage, and even award some kind of points for it, but not sure how to do that in a fair manner. Perhaps allow it for wood components only? to encourage wood boats, and as suggested, a limited "discount" like 30 percent of retail value (it would allow you to build a slightly better boat). Or perhaps offer a separate reward, points or prize to who ever builds the lowest cost boat counting the actual costs.

    After our first meet up we might discuss if there is a practial way to reward using recycled materials, yet keep the intent and scoring fair.
     
  12. Sailor Alan
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    Sailor Alan Senior Member

    Urgent

    Petros. Thank you for your reply, but please leave the beam at 5' for this year at least. You are causing concern in the ranks of the current builders. The 3 separate boats our 'team' are building are designed, one hull nearely complete, and the wood purchased for the other two, all at 5' beam. i also think 7' is just too wide for a general purpose boat, its pretty hard to carry on a rooftop, and it virtually copies the Merlin Rocket in size and function.

    Do we have any dates for the races yet, you mentioned Port Townsend, and Lake Union. Do you have contacts there? Im assuming foirst regatar in Port Townsend, though we have aranged our own tune up races on Lk Washington prior to that. A sort of Louis Viton Cup equivilent.
     
  13. Sailor Alan
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    Sailor Alan Senior Member

    Whew, I just realized it is April fools day, so Petros' comment on the 7' beam was just a joke.

    Here is a photo of my mast in initial dry assembly as a test.
    My assistant is my grandson, and you can see the extent of my workshop too.
     

    Attached Files:

  14. Richard Woods
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    Richard Woods Woods Designs

    My own design is 1900mm wide, but that includes demountable wings, the real hull beam is under 1200

    In part that is because my Zest dinghy is designed to be singlehanded but could be sailed by 2 people, rather than a double hander that could be sailed by one

    Maybe a good compromise for this year would be to say the maximum hull beam was 5ft but removable wings were allowed. I understand the cost/trailering reasons for the narrower beam, but as I said months ago even the Enterprise and GP14 are over 5ft wide.

    And a fast singlehander suitable for lightweights will need to be wider than 5ft or they won't have enough stability in winds over 15 knots or so. Making the boats wider means making them heavier and of thicker plywood. Both against the concept of the class.

    Incidentally the first Zest is now building and two more will start soon. Hull material cost is under USD 250, we plan to fit used masts, typically USD50-100, while a suitable new sail is readily available for under USD200

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     

  15. Sailor Alan
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    Sailor Alan Senior Member

    Just pointed out to me today, the use of 'wings' in the classic sense, implies violating the 'no hollow sections' part of the rule. Not that I'm complaining.

    About beam. This rule has been discussed for some years, and though a wider beam has been discussed, the rules as published stated 5', and several boats are being built to this specification.
     
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