Search results

  1. K

    My improved dagger board and rudder

    Why do people climb mountains? It is an engineering challenge, and I like that. The current foils also have a lot of drag during maneuvering and I hope to quicken tacks. I doubt many people would want to sail with the original dagger board - the FRP ones are nice, but could be better...
  2. K

    My improved dagger board and rudder

    Great question! It is the same for aircraft design, but planes mostly fly straight and level in calm air which makes testing much easier. Prediction methods (CFD codes) are so good these days for basic foils and wing-like shapes that such things are rarely tested anymore in wind tunnels or...
  3. K

    My improved dagger board and rudder

    Thank you for the good comments - expert input is very important to me. A small difference in foil cross section and fin planform can make a big difference in performance, especially at for low speed flow in water. Lengthening a board will help if other aspects are considered. This is of...
  4. K

    My improved dagger board and rudder

    Dear friends, I recently designed a new dagger board that promises a 20% improvement in performance, based on the ratio of side force to drag compared to the composite/FRP board I am now using. I am currently making a composite prototype to test the design on my boat. When this is done I will...
  5. K

    DIY daggerboard options

    No sorry I did not meet Mr. Bennett but my work on a few AC boats (Sail America and Prada) was a long time ago and sort of unplanned. My employer (Cray Research) gave the designers time on our crazy expensive supercomputers and I was the fluids guy there. Attached is a picture of the esteemed...
  6. K

    DIY daggerboard options

    The foils appear too much of a Rube Goldberg yet, keeping them stable without some kind of electrically-actuated autopilot seems to be a real challenge. I am more interested in minimalist, KISS-based, fail-safe stuff. The airplane guy in me says try a wing instead of sailcloth. The first big AC...
  7. K

    DIY daggerboard options

    You are probably correct. I do not follow these things. They were one of many new ideas tried by the S&S team in 1987. The cats have pretty much changed everything and they are quite amazing.
  8. K

    DIY daggerboard options

    Sorry, I am out of riblet tape! 3M worked on this stuff but as I recall there never was a clear indication of it working. Her is an old article on the work: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020087761.pdf The riblet pattern needed to be aligned with the flow...
  9. K

    DIY daggerboard options

    Gee - it seems that Sunfish people are just like my flying buddies - no respect - just my type. :cool:
  10. K

    DIY daggerboard options

    Dennis Connor? Or Dennis Conner? I only know of the latter from Stars & Stripes. Neat guy. His book 'The Art of Winning' is a good read.
  11. K

    DIY daggerboard options

    Thank you for the encouragement. I am impressed be the One Design racers, but do not want to be limited by those rules. Pratt in Hartford, CT was a client of mine in my previous aerospace career and they have some terrific engineers. I want to see what I can get out of the board. It would be...
  12. K

    DIY daggerboard options

    Thanks Coastal Redneck from Central Carolina Redneck, and proud of it! War Eagle! Especially sailplane pilots are often sailboat enthusiasts. Self included. The reasons are the same - it's just me, my craft and nature / my Maker. My grad school adviser, an old-school German\ aerodynamicist...
  13. K

    DIY daggerboard options

    Good point. We have squirrely winds on our lake, surrounded by tall pine trees. I have climbed up the daggerboard a few times after getting a dunking. I figure, if Boeing can make the B787 from carbon, a daggerboard ought to be strong enough if designed correctly. I have a new FRP board and...
  14. K

    DIY daggerboard options

    Solid might indeed be better. You could probably wrap cardboard in epoxy and this too would work, but maybe put a spar in their as on a wing. In my case I just wanted something quick for a season as I intend to do it 'right' with carbon fiber. I am sure others here know what wood would be best...
  15. K

    DIY daggerboard options

    Yes, last year. It vibrated a lot though and eventually delaminated. Water got into the plies and weakened it. It snapped at the bottom of the truck when I flipped the boat in high winds and was righting it. After that I decided this was too critical of a part and I bought an FRP board from...
  16. K

    DIY daggerboard options

    Here are pictures of the plywood I used. The original rudder I made from 19mm (.75") birch, the lighter-colored wood. The second I made from Lauan, 18mm. Since it only has to last one season until I make the carbon fiber parts, all I wanted was something smooth. The thickness of these...
  17. K

    Thrift Store Sunfish!

    Some great suggestions here - wish I had joined this forum when I started work on an old Sunfish two years ago. I was looking for a trailer for a wooden skiboat I just finished and found an old Sunfish, sold with a trailer. The trailer works great and I now enjoy sailing the Sunfish and making...
  18. K

    DIY daggerboard options

    I made a new daggerboard and rudder for my vintage Sunfish last summer from laminated birch plywood, the material used for furniture. I shaped them as good as possible compared to the standard drawings one finds. I gave them 5-6 coats of spar varnish - but this did not prevent their...
Top