ScottWidmier Posted July 30, 2009 Report Share Posted July 30, 2009 I am building a self-designed boat for participation in trips like the Florida 120, Texas 200, and OBX 130. The boat is 12' long, looks wicked, and is designed to go fast (plane) but that is all I will tell you because I want a grand unveiling with this boat at the next Florida 120. Now, the question I have for you is if I should go with a centerboard or dagger board. Whichever I choose the trunk will have to fit under a 7" high deck. Not a big problem with the dagger board but does this make for a skinny centerboard. Here are the positives and negatives for each: Centerboard: + able to kick up which is a big advantage in shallow water + no open slot to spray water on me - added complexity including waterproofing pivot bolt - long large slot creates drag Daggerboard: + much more efficient with no drag due to long slot + I can make it as wide as I want since I am not trying to make it fit below a 7" high deck + simple, rugged, and easy to repair/replace - doesn't kick up as well as a centerboard which is a negative in Shoal waters (see solutions below) - open daggerboard slot can spray water at speed (boat is self draining) I guess I am leaning towards the daggerboard myself since the objective behind this boat is performance. I do know a way to make the daggerboard kick up by slanting the front of the trunk and making a lip at the back of the trunk that the daggerboard tucks under. Hit bottom and the bottom of the board goes back, front goes forward against the slanted front of the trunk, the daggerboard slips out from the lip, and boyancy pops the board up. This works some of the time. Another solution is to carry two daggerboards on-board with one being long for performance and the other short for shoal water ability. I can choose based upon the conditions I face. Gives me a built-in spare as well. It just that the centerboard gives such care-free sailing in shoal waters. Quote Link to comment Share on other sites More sharing options...
Tom Lathrop Posted July 30, 2009 Report Share Posted July 30, 2009 You have a good handle on the features of each although the leaking pivot on a CB is a non-issue if you do it right. Most of my racing boats have had daggerboards, including a 26 footer. The rest are CB's which I much prefer for shallow water use. I suppose the drag of a CB slot is measurable but will not be noticed by most sailors. Hey, it's your choice. I am not at all clear on the deck height thing limiting the width of the CB. I would want more freeboard than 7" on a boat for the use you intend. Quote Link to comment Share on other sites More sharing options...
Charlie Jones Posted July 30, 2009 Report Share Posted July 30, 2009 You don't HAVE to shove the dagger board all the way down you know- half up acts like a shorter board We often sail Traveler off the wind with half a board. Quote Link to comment Share on other sites More sharing options...
PAR Posted July 30, 2009 Report Share Posted July 30, 2009 A 7" tall daggerboard case isn't much purchase on the board. A gasket over the centerboard slot eliminates much of the turbulence. Quote Link to comment Share on other sites More sharing options...
Andrew_Butchart Posted July 31, 2009 Report Share Posted July 31, 2009 If you're looking for performance you'll get it more with a daggerboard than a centreboard. As Charlie says - you can tune your daggerboard for your conditions but when a centreboard pivots it moves the centre of lateral resistance aft. If you look at any racing board boat you'll see that all of them have daggerboards. Reinforce the slot more than you think necessary, and carry a spare board. I've seen a lot of boats going cheap with the daggerboard case ripped half out of them. Quote Link to comment Share on other sites More sharing options...
Charlie Jones Posted July 31, 2009 Report Share Posted July 31, 2009 And DON'T BUILD IT WITH PLYWOOD!!!!! Quote Link to comment Share on other sites More sharing options...
Tom Lathrop Posted July 31, 2009 Report Share Posted July 31, 2009 If you're looking for performance you'll get it more with a daggerboard than a centreboard. As Charlie says - you can tune your daggerboard for your conditions but when a centreboard pivots it moves the centre of lateral resistance aft. If you look at any racing board boat you'll see that all of them have daggerboards. Reinforce the slot more than you think necessary, and carry a spare board. I've seen a lot of boats going cheap with the daggerboard case ripped half out of them. A lot of boats including, as you say, the boardboats have daggerboards. That may have more to do with cost to manufacture than anything else. Most larger racing dinghys have centerboards. A CB is a lot easier to live with. Quote Link to comment Share on other sites More sharing options...
ScottWidmier Posted July 31, 2009 Author Report Share Posted July 31, 2009 This is one thing I love about sailboats, there are so many different ways to go that give different strengths and weaknesses. I guess my big concern is for the dimensions of the centerboard I can fit under the cockpit floor. A 7" wide centerboard would necessarily have to be fairly long whereas a 12" wide daggerboard could be shorter (more shoal draft). Am I wrong in thinking this? Is there any utility in as narrow a board? I considered an offset board which I have done on some other boats but there is just a lack of crispness when turning one direction I don't want in a performance boat. The small leverage 7" will give on a daggerboard trunk is a valid concern! I was going to have bulkhead's fore and aft of the trunk and a hardwood beam under the cockpit sole at the midpoint of the trunk. I always put my trunks in with logs which should help reinforce the deck attachment. The kick-up daggerboard trunk means you would need notches in the trailing edge of the daggerboard to run with it partway up for any distance. Notches means turbulence when the board is down which is why I am thinking two boards with one being for maximum upwind effectiveness and the other for shoal water work. Any board I build would be out of solid wood laminated together with a good foil shape. Again, I have used and still use plywood boards on some of my boats but those are light lower performance boats that I am willing to take the risk on. I definitely am not willing to take the risk on a long-distance performance boat especially after reading the stories from the Texas 200! I think based upon the advice here I will go with the dagger board for its performance, simplicity, and that I can make it wider than 7". Unless someone has another idea? I am dying to share this boat but will hold off. I used Hulls to design the shape which is a good thing as the panels turned out fairly complex in shape. Amazing how everything fit together though. I am planning to use this boat as a testbed for a couple different rig types. Quote Link to comment Share on other sites More sharing options...
PAR Posted July 31, 2009 Report Share Posted July 31, 2009 Use tandem boards (not bilge boards like scow), the main board is the biggest and further forward then typical, the second board is smaller and fairly well aft. With this arrangement you can self steer the boat with just the boards. In other words, by arranging the two boards, you can balance the sail plan perfectly and take a break from helm duties. You also can employ a kickup feature (to a degree) without notching the trailing edge, but by angling the leading edge aft, over a "fulcrum". Assuming you're maximizing your rig and hull, you'll want a narrow, deep board, in preference to a wider, less deep one for performance. Quote Link to comment Share on other sites More sharing options...
Charlie Jones Posted July 31, 2009 Report Share Posted July 31, 2009 Yep- dual boards work really well Here's a a picture of Laura steering a 54 foot sloop set up like that- dagger board forward, swing board aft See how hard she's working? ;D Quote Link to comment Share on other sites More sharing options...
PAR Posted August 1, 2009 Report Share Posted August 1, 2009 One of the several advantages to tandem boards is the ability to increase area in low speed situations, which is when fancy high aspect boards really suck. Quote Link to comment Share on other sites More sharing options...
lbrewer Posted August 1, 2009 Report Share Posted August 1, 2009 You could possibly widen the center board in front of the pivot hole by a couple of inches. When stowed, the leading edge of the board would protrude from the slot a bit. If there is to be a keel of any sort along the centerline, the protruding edge could fill a longitudinal gap, completing the shallow keel when stowed. Don't take measurements off the diagram ...just an idea. Quote Link to comment Share on other sites More sharing options...
ScottWidmier Posted August 3, 2009 Author Report Share Posted August 3, 2009 There is no keel on the bottom of the boat. I hope to have the bottom of the boat flat and smooth for less wetted surface. Plan on using up the rest of my dynel cloth on the bottom so I can beach it without worry. Given the size of the boat, I think my preference would be to sleep with the boat on the beach if possible. The dual boards are interesting. Didn't know too much about them and had to do a little research. However, I think I still prefer one board at the center of resistance for crisp response to the helm. Quote Link to comment Share on other sites More sharing options...
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