Can I make an IOR boat fast?

Discussion in 'Sailboats' started by neurotica, Feb 6, 2018.

  1. neurotica
    Joined: Jun 2015
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    neurotica New Member

    Here is the situation, I work at and have a composite shop. We specialize in making sailboats fast. Keel fairings, carbon stuff etc, we have a quantum sail loft, a rigging shop, and a chandelry. The question is can I take a c&c 1/2 ton and make it stable and relatively fast. Say 140 phrf? Can it be done? If so how?
     
  2. luff tension
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    luff tension Junior Member

    short answer - No probably not.
    The cheap part is the hull and decks. If you have an existing boat, the rig/deck hardware could be recycled onto a new, decently shaped and hull. Why waste time reshaping an old IOR hull shape dictated by an antiquated series of girth and freeboard measurements when for a similar effort you could make a decent hull shape that will actually go faster than its displacement speed.
     
  3. neurotica
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    neurotica New Member

    Hmmmm, so some more info, the deck was recently rebuilt professionally with infused foam core, the keel is off, it is gutted and easy to work on. And very, very cheap. Building a whole new hull is a big expense compared to modding the old one if possible. Even if I cut big chunks off and rebuilt it would still be easier to work off something. I however am a technician not a designer.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    With some relatively minor modifications to the hull form, you can marginally improve her speed. She's not that bad (assuming the last gen of the C&C designed near the end of that era) as she is, though everything can be improved. It's appendages can be refined a bit, made truly symmetrical, employing better sections, etc. I think some eddie making can be decreased with a new rudder pan form too. Her stern tried to take advance of the girth rules and had a significant hump, which may be removable or at least flattened out a bit, but now you're into major surgery and the cost effectiveness to speed gains may come to play. It might be possible to get some of the V out of her deadrise aft too. As to how she'd rate, well this tends to be a crap shoot in a lot of places and well placed 100 dollar bill, may help in this regard.
     
  5. CT249
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    CT249 Senior Member

    Luff, the C&C is a masthead rigger. The original rig is unlikely to be able to be recycled to fit a "modern" shape, IMHO.

    Wiki says the PHRF is 165. That compares to the Holland Shamrock types pretty accurately, it seems, since they rate slightly faster and the Shamrock won the worlds in which the C&C was sixth. Similarly, a Hawkfarm finished about the same place at the worlds around the same era, and they rate 168. So you're looking at almost 3% improvement in speed.

    Perhaps the fastest of the half tonners of anything like that weight were the X 95s (144 PHRF) and the racing versions of the Nicholson 303 "baby Imp" style, which were competitive at world level into the early '80s and would probably be about 144-150 PHRF at a guess. The production Nich rates a leisurely (and perhaps unfairly high) 168. The X95 was several years and about three design generations newer than the C&C and has a wider stern and flatter hull.

    My own half tonner picked up about 4% or more from a new rudder and changing from a masthead rig to a fractional, but she was much older and lighter and was originally badly under-rigged and had very poor foils. There's less room for improvement in the C&C and the rig change probably wouldn't work as well. Some of the IOR one tonners that were heavily altered picked up about 1-2% with keel alterations and fairing of the bumps, I think, but that was in newer boats with lighter and fairer hulls with wider sterns, which could respond to the higher speeds.

    Gut feeling is that improvements would certainly be possible as PAR says, but that 140 is a big stretch since you're still limited by the weight and basic shape. You then could run into the issue that you may be very quick upwind in a breeze with that much weight and good foils, and very quick downwind in the light with that big masthead kite and low wetted surface stern, but in other conditions you'll still be limited by hull speed and paying a high price in rating, plus probably a penalty for altering the boat.

    We've had some old heavy half tonners out here that did very well just because they were in good condition, optimised without undergoing major alterations, and well sailed and geared. I've done a couple of articles on optimising old IOR boats and discussed the issue with designers and measurers and the consensus probably is that for most heavier boats, minor tweaks are best - foil section optimisation, new and lighter rudder, weight concentration, optimised deck layout and hardware. Major alterations normally turn out rather disappointing.

    I love half tonners, although for where I sail I prefer light fractionals. Sure, they aren't fast, but if you want speed get a kitefoiler.

    Dunno if that helps.
     
  6. neurotica
    Joined: Jun 2015
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    neurotica New Member

    Wow, that's great help. For clarification I am not really interested in racing and am using the phrf numbers to come up with relative speed. Why for example is a j/30 so much faster? It weighs the same and has a galley! I am not worried about penalties. I have been looking for a j/30 to experiment on but this half tonner fell in my lap. Thanks for all the help. I will try to get some photos up soon. I must say, it sure would be fun to grab a recip saw and start chopping. A normal day for me is fairing a j/24 keel by a few thou with coats of performance epoxy and 800 grit. Building a new bow, stern, or hull would be fun.
    Thanks all
     
  7. luff tension
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    luff tension Junior Member

    Here in NZ there is little attention paid to any kind of measurement rules and its a case of make it as fast as you can with no penalty. I see the masthead rig as the limiting unless you sail in a predominantly light air place (which we definitely don't have here) but fairing out any IOR bustles and bumps has got to help it go faster. Adding stability with a new keel design or a bulb on the existing keel would have to help too.
     
  8. CT249
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    CT249 Senior Member

    I've never sailed a J/30 (Rod's second design) but I've sailed J/24s (his first design) and own a J/36 (his third design). I think the J/30 has a fairer hull at the stern, giving it a higher speed capacity and longer effective waterline. The waterlines are also wider at the stern low down, I think, giving it more form stability.

    I also only use PHRF numbers for relative speed, since we don't have PHRF here in Australia. Here we either race under rating systems like ORC or IRC, or golf handicapping like they often do in NZ. I hate racing under golf handicap only since many of the things that make a boat faster are an expensive hassle; under a rating system you can take the option of making the boat cheaper and easier to sail and getting a rating advantage. Sure, you may go slower but all keelboats are slow for their length and cost anyway.

    PS- My sympathy for having to spend time fairing keels. It's interesting that you North Americans seem to spend so much more time optimising your J/24s and other one designs. In Australia and the UK (and probably NZ) we seem to be much more into just getting out there and training. I wonder if it's because you often sail on more open and calmer waters with steadier winds, where the tiny nuances of straight-line speed make more difference?
     

  9. Chuck Losness
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    Chuck Losness Senior Member

    To try to make an old 1/2 tonner with the pinched in ends like the C&C 1/2 tonner even marginally faster is more trouble than it's worth. And would cost a fortune in time and materials. You would have to totally reshape the back third and the front third of the boat. Change the rudder and the keel. You would be way ahead of the game to drop that C&C 1/2 tonner in somebody else's lap and go buy a J/30 if that is the boat you really want to have. I guess it really depends on how you plan to use the boat. Different horses for different courses.
     
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