Blkskmr Posted March 22, 2016 Report Share Posted March 22, 2016 Graham, For those of us not inclined to modify the centerboard, are there other adjustments we can make to improve pointing ability? 1) Would moving the mizzen mast aft a few inches help? 2) Would reducing the area of the main while maintaining area of the mizzen help? My thought is to move center of effort slightly aft and reduce area of main to reduce tendency to heal to keep boat flat and therefore maintain lateral resistance. If I can avoid cutting the boat up, I would like to. I would also like to point. Thank you Quote Link to comment Share on other sites More sharing options...
Chick Ludwig Posted March 22, 2016 Report Share Posted March 22, 2016 How about deepening the "keel" by an inch or two? That seemed to work well with my Princess 22. I could live with a bit of extra draft to keep from having to cut-up the boat. If I were at an earlier stage of construction it wouldn't have been such a big deal to modify the trunk, but now...... Blkskmr, balance isn't the problem. The centerboard just doesn't have enough area to counter the sail area and reduce leeway. It's a trade off in design between lateral plane to reduce leeway, and the drag that keel and centerboard induces. Quote Link to comment Share on other sites More sharing options...
Designer Posted March 22, 2016 Author Report Share Posted March 22, 2016 Chick, I am off to the shop. I will answer tonight. Quote Link to comment Share on other sites More sharing options...
alexscott Posted March 22, 2016 Report Share Posted March 22, 2016 Drafts of the 17 & 20 Core Sounds from the website: CS 17 - 3' 6" CS 17 Mk 3 - 2' 10" (8" less) CS 20 - 3' 9" CS 20 Mk 3 - 3' 6 1/4" (2 3/4" Less) EC 22 - 6' Sure looks like a longer board will help the 17 Mk 3 Quote Link to comment Share on other sites More sharing options...
Chick Ludwig Posted March 22, 2016 Report Share Posted March 22, 2016 alexscot, These drafts you listed are for the centerboard lowered. A longer centerboard would add to the drafts you list. A slightly deeper "keel" like I'm asking about would only add to the draft with the board up. I'm just wondering about a solution for the CS-17 Mk-3's that are already built. Graham is changing the plans and kits for future boats to have the longer board and trunk. A"slightly deeper keel" would not apply to these. Quote Link to comment Share on other sites More sharing options...
alexscott Posted March 22, 2016 Report Share Posted March 22, 2016 Chick, You are correct- In fact I should have compared Max - Min drafts which would be the length of the lowered centerboard below the hull. Check with Graham, but you might be able to make a virtue out of necessity by adding bilge keels like the Belhaven 19 and get not only better windward performance but also level beaching/grounding without any added draft. Quote Link to comment Share on other sites More sharing options...
PAR Posted March 22, 2016 Report Share Posted March 22, 2016 Adding a little more depth to the skeg (what you're calling the keel), isn't going to help all that much, unless you add several inches. This type of addition would be costly on most points of sail, simply from the area and increased drag. A more reasonably retro fit, instead of making the case longer, might be to make it taller, increasing the cord of the foil, which offers more area. Quote Link to comment Share on other sites More sharing options...
Chick Ludwig Posted March 22, 2016 Report Share Posted March 22, 2016 Par, that would be a much easier job! Maybe Graham will go for it. Quote Link to comment Share on other sites More sharing options...
PAR Posted March 23, 2016 Report Share Posted March 23, 2016 I'm sure Graham is looking for more aspect ratio as well as lateral area (my assumption). Quote Link to comment Share on other sites More sharing options...
Chick Ludwig Posted March 23, 2016 Report Share Posted March 23, 2016 I agree that Graham is more interested in aspect ratio for for best performance and efficiency, but for us non-race oriented folks, maybe a lower aspect ratio is a fair trade-off for not having to cut into our boat as much.It'll be interesting to hear his reply to all of this. Quote Link to comment Share on other sites More sharing options...
Jknight611 Posted March 23, 2016 Report Share Posted March 23, 2016 Hi all, if you built the swing keel that didn't completely retract into the case ( drilling the pivot hole "higher) the cord could easily be increased with no messing about with the case. The skeg would protect the board when retracted the board stood proud of the bottom 1 inch or so. On our visit at the Messabout 2015 I noticed Carlita had provisions for a forward centerboard in construction. I wonder...... Best to all BTW, Southern Express is living up to all of our expectations, except for the aft (ouch) hatch. And I am "workin" that problem Quote Link to comment Share on other sites More sharing options...
Action Tiger Posted March 23, 2016 Report Share Posted March 23, 2016 Would a longer board also shift the lateral plane aft a little? I'm thinking especially with the board partially retracted, like on a reach. I'm just curious, and I learn a bunch of stuff on this board. Shoot, that last line was no attempt at humor. Just coincidence. Quote Link to comment Share on other sites More sharing options...
Blkskmr Posted March 23, 2016 Report Share Posted March 23, 2016 Chick et all, I agree with you. It would be good to have a solution for us non-racers. I have been thinking of this statement you made in a prior post, " The centerboard just doesn't have enough area to counter the sail area and reduce leeway." This makes me wonder what the sail area would have to be reduced to in order to be the functional equivalent of the present rudder and centerboard. I would be comfortable with that. The boat only weighs 600lbs at worst, so it won't take much force to drive it. We shall see. Regards Quote Link to comment Share on other sites More sharing options...
Chick Ludwig Posted March 23, 2016 Report Share Posted March 23, 2016 Blkskmer, there is more to it than that. Wetted surface of the hull and the area of the boat above the water also need to be considered. Wetted surface makes "friction" and the exposed hull above the waterline has the wind blowing against it. Ya just gotta have enough sail area to "overcome" those forces. We want a good solution, but don't want the boat to become a "slug" and not sail satisfactorily. AND the slower the boat goes, the less effect the centerboard will have on leeway. STUPID HYDRODYNAMICS!!! I'll bet Graham is laughing his head off about now. Quote Link to comment Share on other sites More sharing options...
Blkskmr Posted March 23, 2016 Report Share Posted March 23, 2016 Chick, Slugs are attracted to beer. I am attracted to beer. At least we would have something in common. I guess I could give the boat a brown leopard color scheme, put a couple of horns on the bow and figure out how to leave a watery slime trail, vegetable oil.. organic. It would be novel, but hardly the stuff of legends. We could get together and have a "Slug Fest" Rgds Quote Link to comment Share on other sites More sharing options...
Designer Posted March 23, 2016 Author Report Share Posted March 23, 2016 Chick is right, reducing sail area will not solve the problem. Here is a picture of my board. You can see that it has been glassed and the the peel ply is being removed from left to right. I felt that the board was under sized and I maxed out the length that my trunk would take. You can see the 7/8" spacer between the lead and the board. There is room to increase the chord which I did not do under the press of time. It is a very good foil, being machine cut, so we can rule out that question. You could also increase the chord so that it was maxed out in the trunk plus you could allow a couple of inches to always protrude from the bottom. That would increase the size of the board a fair amount without cutting into the trunk. Par is right that deepening the outside keel will not help a lot. I had a 3/4" deep sacrificial keel on the outside. I did not have time to put on the SS hollow back and it looks pretty scruffy now, but it did it's job. Alan will be back in a few days, after he recovers I am sure that he would like to help me do some on the water testing of some ideas that I have. I can screw on a temporary keel extension to see how much it helps. Quote Link to comment Share on other sites More sharing options...
PAR Posted March 23, 2016 Report Share Posted March 23, 2016 For the non-racer there are a few options to fight excessive leeway. Bilge runners and a deeper chord are what I think are the easiest ways to go, in this regard. Moving the pivot would help offer some room too. Quote Link to comment Share on other sites More sharing options...
Blkskmr Posted March 23, 2016 Report Share Posted March 23, 2016 Ok... sounds like the best path would be to continue with present build / design. It would be nice if in six months to a year there would be a re-designed optimized board we could purchase for this first group of boats that would not require modifying the trunk, for those of us who don't want to cut into the boat. I am not looking for perfect, just better. Graham, thank you for giving us the heads up and working so quickly to try and come up with solution. When I spoke to you Monday morning I was not aware this was brewing. Best Regards to all. I flip the boat tomorrow. Quote Link to comment Share on other sites More sharing options...
Blkskmr Posted March 24, 2016 Report Share Posted March 24, 2016 Wider board option 03 24 16.pdfGood morning, I had an idea, probably not practical, but seems to meet the idea of increased cross section for the board. I am not a fan of cutting into the centerboard well, but removing the top of the well from behind bh 4 to to its end would be less invasive. I prefer an open centerboard well, but it could be re-closed. The board would maintain present length. The chord at top could be lengthened as required and maintained to as low as possible on the board. The one draw back is the tip must still be tapered to allow the board to swing down. I expect there are any number of draw backs to this idea that will render it useless, but it is a modification that as an amateur I would feel comfortable attempting. The work would take place above the floor boards. The good thing about bad ideas is that they are catalyst for better ideas. ( Please see attachment) Thank you. Quote Link to comment Share on other sites More sharing options...
Phil Garland Posted March 24, 2016 Report Share Posted March 24, 2016 Graham, great report on your EC voyage...we hope to be there next year with La Perla. I've always been intrigued by Matt Laydon's chine runners he used on Enigma and other designs. He used those with no boards and they seemed pretty effective. Those would be a relatively easy modification as opposed to a longer centerboard. Owning 2 cat ketch designs (Presto 30 and CS17) with good sails and spars, going to windward is not its best point of sail, however it reaches and runs very well. When we did the EC in the CS17 we rigged a bowsprit to set a small jib (from a Thistle) for light air. It certainly helped going to weather but it created lee helm...we also set an assymetrical spin from the sprit and the boat was planing in 14-16 kts of breeze. Overall I have been very impressed with the performance of the Core Sound design and it's a perfect craft for expedition/adventure races and camp cruising. Quote Link to comment Share on other sites More sharing options...
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