Tim TITAN Posted January 23, 2005 Posted January 23, 2005 any problems using two sheets of plywood laminated to make a centerboard and then glassing over with a 4 or 6 oz cloth rather than doing the quarter sawn method for a CS20? I think it would be plenty strong and not warp since it will be glassed over, but will it flex too much? any other problems with doing it this way? Quote
Designer Posted January 23, 2005 Posted January 23, 2005 Stay with solid wood for the centerboard. Ply has half of the grain running across the centerboard and it will definitely break. The fiberglass you intent to put on is not enough to make up for the ply's lack of strength. Quote
Tim TITAN Posted January 23, 2005 Author Posted January 23, 2005 two sheets of 3/8 marine fir ply laminated together and glassed would break you think? Quote
Charlie Jones Posted January 23, 2005 Posted January 23, 2005 Yes, it would. Probably right where it exits the slot.. You would only have 3/8 inch of grain structure running longitudinally down the board- the remainder of the thickness would be doing nothing. So strength wise, you'd have a 3/8 board with some glass on it. Stick with the plans- there's a reason Graham designed it that way. And a broken centerboard can spoil your whole day Quote
PJPiercey Posted January 23, 2005 Posted January 23, 2005 Tim, You might want to take a look at this thread about using plywood for daggerboards. It explains how one failed and how I constructed mine to be successful. http://forums.bateau2.com/phpBB2/viewtopic.php?t=3978&highlight=centerboard The things I like about using the plywood are: Easy to laminate up a nice dimensional core. About 20 oz of fiberglass laminated between the first two layers of plywood gives you a nice solid trailing edge (after shaping) that is less prone to chipping. The leading edge becomes very durable with the solid fiberglass at the apex. Plywood gives you automatic contour lines to guide your shaping making it much easier to get a very fair shape. I agree with all the comments about the plywood strength verses the solid wood so glassing the exterior is a must. When you read my account of how I layed mine up keep in mind I used the wood I had available and I wanted the overall thickness to be one inch so I could create a NACA 0010 foil shape. Good luck with the building and I look forward to seeing some pictures. Paul Piercey Quote
Rob Blackburn Posted January 24, 2005 Posted January 24, 2005 Mate.... the CS 20 generates a fair bit of activity around the centreboard. Full sail, solid crew, pounding along to weather with the board right down... get the picture. Ply would break before you got out of site of the boat ramp. Rob Quote
Tim TITAN Posted January 24, 2005 Author Posted January 24, 2005 ok I'm sold. I'll be using solid wood for that. thanks for the help. Quote
Tim TITAN Posted February 4, 2005 Author Posted February 4, 2005 so I guess plywood glassed over would be fine for the rudder blade since its smaller and has less lateral force on it than the centerboard? Quote
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