Moderated Re: ECO 6 Build - rudder blade failure
¿ªÔÆÌåÓýI have been using a similar fold up method for dagger boards and rudder blades over the last 40 years except instead of using plywood I use a Sheetmetal mold to lay up a composite part. The most recent ones I did were a pair of dagger board rudder blades about 300mm chord x 2m length. The system involves having a Sheetmetal shop fold up a simple mold out of 16 gauge steel, an appropriate die is used for ?the leading edge radius and it is folded to about 45 degrees then I have them do a 90 degree fold at the trailing edge to create a flange that I can screw a strip of wood to so I can use clamps to pull the two sides together if that makes sense. Basically you are making a Vee shaped mold with a flange at the trailing edge to stiffen it. You need to make a simple wooden jig to support it leading edge down while you apply mold release and do the fiberglass layup (or carbon). After it has cured you fold it up around a beam at the thickest point and glue the trailing edge together. I use predominantly uni glass and double bias in the laminate to make a structural skin so there is no extra glasswork done after releasing from the mold and the blade is perfectly fair and is ready to sand and apply paint. You do need to of course, plug the ends and I now use Coosa board for this. I have used various foams to fill the blade in the past but have settled on leaving them hollow as there is no chance of exotherm causing fairness problems and also if you sustain damage and get water in the blade you can just drill a hole and drain it out with no risk of waterlogged foam. With this method you do have the cost of the mold but it is not very much, I believe it cost me about 160 usd for my current mold which can be reused. My current blades are on a 31ft 7000lb Gemini cat. For the beam that you fold around I have settled on a diy fiberglass I beam that I make by making 2 channels glued together back to back so the web is twice the thickness of the flanges. ? ? Steve ? ? ? ? ? ? ? ? ? ? ? Sent from for Windows ? From: christopher gent
Sent: Sunday, March 19, 2023 5:55 AM To: [email protected] Subject: Re: [K-Designs-Multihull-Sailboats] ECO 6 Build - rudder blade failure ? Hi Rod. I built an Eco7.5. My rudders were laminated wood. But my dagger board used Bernd¡¯s V system. I had problem because I could only get 6mm plywood instead of recommended 4mm.? ? Bernd¡¯s advice to me was to use a router for 1-2 mm along the whole ?length of the inside faces (spaced about 5 cms apart.) This again was straining the ply a bit so I ended up repeating the router groves as deep as 3mm. It worked out fine. I used some slightly thickened epoxy on the inside of all the grooves before closing it all up.? ? I hope you get some success?with this method. ? ? Best regards ? Chris Gent.? ? On Sat, 18 Mar 2023 at 23.01 Rod McLaren <nkosuohene@...> wrote:
? |
