reverse daggerboard angle
Posted 30 June 2006 - 08:42 PM
Posted 01 July 2006 - 06:33 PM
1 a shift forward of the center of lateral resistance which I think would increase weather helm significantly, even in a little boat like a spindrift.
2 when you happen to hit a submerged pot warp or anchor rode it would tend to travel up the leading edge and get stuck at the intersection of the db and the bottom. Probably easy enough to clear if you know what you hit but some reverse rake makes it easier to deal with.
just my $.02.
Posted 03 July 2006 - 07:47 AM
You did say that you would probably build a nesting dinghy. A reverse or even straight daggerboard will not work on a nesting dinghy simply because the stern section must be kept clear for the bow section to fit in it. The daggerboard trunk must be located in the forward section.
You will notice that the non-nesting Spindrfits have a straight daggerboard. The nesting version has the trunk in the forward section so the daggerboard is swept aft to maintain the correct balance for the boat. At least, that is my guess.
Posted 03 July 2006 - 10:37 AM
Posted 03 July 2006 - 12:15 PM
Years ago, I adapted a standard pram design to be nesting. I also wanted a daggerboard so I came up with the design sketched below (you have to click on it to see it clearly). It worked great for nesting even thought it maed the bundle a little longer. It also worked great when assembling the two halves in the water since the tapered section guided themselves easily into place. I always assembled it in the water, even during a storm.
Unfortunately, it didn't work great for sailing because it was way out of balance. I only tried it once and gave up. I probably could have moved the mast location for better balance.
Posted 03 July 2006 - 03:03 PM
Posted 04 July 2006 - 05:00 PM
Posted 04 July 2006 - 08:43 PM
I think the thing would almost have to be triangular because it seems like the angle would have to be pretty drastic to overcome friction. In the end it would try to pivot in the trunk and would probably jam at exactly the wrong moment. Well, there's always a centerboard (or leeboards)...
Redesigning the shape of a daggerboard would probably have just as drastic an effect on balance as changing the angle though - Not something to be taken lightly...
Posted 04 July 2006 - 09:42 PM
Posted 05 July 2006 - 09:56 AM
Canting forward does offer a slight performance increase, test have born out, but the disadvantages have so far discouraged the fad catching on. Of course you'd like the root of the board to start in an acceptable location, placing it's center in proper lead. On a small boat this could be just a few inches.
Curved daggerboards have had some successes in the "retraceable on strike" column (also clearing the boom). Several designers have tried this arrangement, most with variations in curve and angle. Which ones work best is subjective.
A razor let into the leading edge can solve many of these issues, but like all things in yacht design, brings up its own set to contend with.
In small craft, particularly sail, it is a delicate balancing act, you have little margin for error. Every piece, its size, location, weight, relationship and effect with, or on others, make the tasks required interesting.
Posted 06 July 2006 - 01:16 PM
Posted 06 July 2006 - 06:44 PM
I was sort of thinking out loud on that one. I've had daggerboards before and I've never grounded hard enough to hurt the boat but it certainly is a warm fuzzy feeling knowing that I can use my (future) centerboard as a depth sounder...
I think that if I required that warm fuzzy feeling in a boat I'd either convert to a centerboard with the same underwater profile as the original daggerboard (and lose the interior space) or switch to a boat design that started out with a centerboard. It's all about the tradeoffs isn't it?
Posted 18 July 2006 - 06:16 AM
As far as "bouncing" the board as a depth sounder...
I don't know what its like where you are but where I sail just a slight touch on those barnicle infested rocks and I am spending two days building my three layers of 8 oz cloth back up :-)
Posted 18 July 2006 - 07:53 PM
Posted 25 February 2012 - 07:50 AM
I also built an OSB with my Grandson and incorporated the design of a PDR center daggerboard into it. Not unusual other than the OSB plans were for a row boat and not a sailboat. It sailed well, but performed more like a sailing canoe than a sailboat.
Finally, I made a PDRacer for my wife. One of her specifications was that she have ample room to carry Grandkids. After more research online I discovered an Oz PDR that had the daggerboard in the side air box. I engineered her PDR to that end. I used plans I bought online, but modified them considerably as the plans called for a traditional center located daggerboard box. As it is the box is encased in the starboard air box and is both easy to use and leaves the cabin of the PDR completely open. After tuning the rigging she sails like she has an outboard motor attached.
Posted 01 July 2012 - 06:26 PM
Marissa 18 'Salty' (under const)
CS 17 Hull#78 "Lively"
Marples 3Meter Constant Camber Tri "Bananas"
17'6" Pigmy Coho kayak
16' Redwood Stripper Canoe
Posted 03 July 2012 - 06:50 AM