• Content Count

  • Joined

  • Last visited

Community Reputation

0 Neutral

About k76

  • Rank

Profile Information

  • Location
    Lake Macquarie

Recent Profile Visitors

2,354 profile views
  1. k76

    DC Designs

    You're right Dan, I was thinking more sailplan than stick. Looking at the stick I agree that the finn mast is a highly developed piece of equipment. I hope we don't go there though, I think that kind of stick lends itself too well for professional analysis and advanced construction techniques. The Finn and the Europe has shown itself to be classes where you pay someone to develop stuff and that's no fun. But if its fast I'm sure we will go there eventually, me included.
  2. k76

    DC Designs

    Phil, I both agree and disagree with what you are saying. I think Geoff's point with inertia about the heel axis is important as it will be the trigger for something to happen. For a properly set up rig that something shouold be the topmast flexing &/or square top flexing out, twisting out the top in gusts, lowering the centre of effort of sails and increasing the drive force for the same righting moment. That is something you can't achieve to the same extent just by sheeting out or feathering, and you certainly can't match the reaction time. It won't last very long, in longer gusts you have to take manual action. Maybe we are discussing different timeframes for our gusts?
  3. k76

    DC Designs

    Danny Boy, Why wouldn't a UNA rig be faster in light air? I've always pictured a fast UNA rig for an IC as something A class like (like the rig Steve found didn't really work although it looks good). Anyway, based on a rig like that: (all upwind) In really light air the benefit of having more sail area up high surely would outweight any advantage from the two sails having a higher effiency? In light to medium wind the two sail boat has the jib sheeted so tight that you are in marginal territory with the slot anyway. Once the slot gets too narrow you might as well not have the jib. You just end up with a very flat main to stop it backwinding. In this wind range you are still benefiting from more wind and better apparent wind angle up high too. Once you start to depower the two sail rig is conceptually better with a lower center of effort and the slot is in the effective range. I understand a triangular finn style sail would have a lower center of effort so all of the above doesn't apply. But is that the right way to go remembering that the canoe has relatively much more righting moment/sail area than a finn?
  4. k76

    DC Designs

    Frank, I'm not a believer, but maybe that's just because I haven't seen any results from it. We haven't seen any results from it because of RRS 54: 54 FORESTAYS AND HEADSAIL TACKS Forestays and headsail tacks, except those of spinnaker staysails when the boat is not close-hauled, shall be attached approximately on a boat’s centreline. I'm not sure how much you can push the "approximately" but there is some opening for interpretation there. I think I remember some arguments in the IOM class, where someone attached their forestay at the hull bottom and let it pass through an oval hole in the deck. That boat apart, the model boats are actually doing the opposite, pulling their tack to windward because of their jib boom setup. If that really had an adverse effect on performance I think they would have found another way to sheet their jibs.
  5. k76

    DC Designs

    I think what is a big deal with the canoe is getting everything right and sorted. A gybing board is another thing on the list, and lets face it, we all struggle to find the time to sort our boats out. Spending time on improving your rig and sails and making sure you can sail a regatta series without any kind of equipment failure is probably time better spent than messing with a gybing board. (But not as fun!!!) The other thing I sort of hinted about in my last post is that a simple but good conventional board is better than a badly designed and/or built gybing board. If you have a 100% reliable setup (and you can stop congratulating yourself about that while sailing) I don't see that it will detract you much while sailing though.
  6. k76

    DC Designs

    Jim C, You are almost right that the gybing angle only affects the angle of the hull. The little bit that you are missing is that this is the big deal. The hull is providing sideforce, and with that comes drag. For small angles of attack you actually get a useful sideforce at almost no drag penalty, but for larger angles of attack its shortcomings as a lifting surface become evident. So although you can theoretically gybe the board to give zero leeway of the hull you are just giving away your "free" lift. Gybing the board even further to "claw" your way up just means your hull is counteracting the board, its a fantasy that doesn't work. What works is this: Have your hull at the optimum angle. I'm not sure exactly what it is, but its more than zero degrees and less than the optimum angle of a non-gybing board. If you are trying to achieve the optimum angle of the hull with a conventional board you immediately run into a tradeoff of having to increase the size of the board, which gives you more drag from the board. A gybing board or a trim tab allows you to decouple this by providing more lift at small angles of attack with less overall drag. A secondary effect is that you are now free to chase the optimum loading on your foil for achieving laminar flow. It may even be the more important effect. So just gybing a big NACA00XX board may not give you much effect, but Oliver is making the right noises by using a smaller board with a good section. And then the rudder size and rig position comes into play as the sideforce is shared between the keel and the rudder. I don't think this is ever going to be a copy and paste excersize given the differences in our boats. To sum up the gains to be had are: Less drag from hull, less leeway(never zero) and less drag from board.
  7. k76

    DC Designs

    Hi all, Sorry I couldn't make it to the worlds, but congrats to you all. Thanks for everyone's writeups on the DC designs. Was there any great differences in the relative performance of the boats in different conditions? I always expected Chris' machine to be a killer in a blow, but that maybe the narrower stern designs would have their day in lighter conditions? Or is the crossover windspeed so low as to be irrelevant? Same thing with the UNA rig, did it show promise in the lighter conditions?