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My newest project

34249 Views 238 Replies 49 Participants Last post by  bobperry
This is a new 43'er for a PNW client. The boat has twin diesels on sail drives. The builder is James Betts in Anacortes, WA. This is a custom project and what you see is what the client wants. But this image is a bit obsolete now. The hull ports have gone. The dink is off the housetop and the cabin trunk portlights are now all the same size. Details. Construction will be composite with epoxy.
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Handsome boat and a very interesting design. Its almost a very big and updated Bristol Channel Cutter. That is a very creative solution to protecting and supporting the bottom of the outboard rudder while being able to cut away the aft end of the keel.

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I'd rather JeffH answer your question. He knows his stuff and I can;t type worth a damn.
If Jeff doesn't answer it I'll do it.
Bob- Thank you for the vote of confidence.

I think that SloopJonB did a great job of explaining the terms that CCRiders was asking about. In basic engineering terms a composite is simply using dissimilar materials to create a unified structure that takes advantage of the characteristics of each material. As noted the term has been used in many ways in boat building such as wooden boats with metal frames in the late 19th & early 20th centuries, or FG or FG with metal framing.

In the case of an FRP laminate, as a composite material, the fabric/fibers handles all of the tensile loads, and the resin glues the fabric together, takes sheer between the layers and takes the vast majority of compressive loads.

I am not sure that it was clear from the write up that epoxy is a much more expensive resin than conventional polyester or vinylester resin and offers no real strength advantage when used with conventional E or S glass. High strength, low stretch fibers like carbon or Kevlar, require either epoxy or vinylester resin to fully utilize the strength advantages of these materials.

Epoxy does offer the advantage of near zero moisture permeability, which is especially important with carbon fiber which can be damaged by moisture intrusion due to electrolysis or corrosion. Then again vinylester offers similar though not as good strength and permeability characteristics at a less expensive cost, and offers a little better ductility.

Epoxy-Kevlar laminates have particularly higher resistance to abrasion than most laminates and a very good resistance to being punctured in an impact. Vinylester/Kevlar laminates also have very high impact resistance and are used to create bullet resistant military helmets. Vinylester/conventional glass are used for motorcycle helmets. Cored vinylester resin laminates offer the highest impact resistance and stiffness for the fiber involved also offering the added advantage of some sound and thermal insulation value.

Properly laminated the reduced flexure and fatigue of a cored hull offers the longest durable strength characteristics but the layup needs to be perfect. The poor layup and protection of the core on many early cored hulls have given them a bad rep.

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I don't see how you can use winglets on a rudder with a raked rudder post without generating excessive drag due to the change in incident angle to the water flow as the rudder steering angle changes. To explain my thinking on this, assuming that the winglets could be designed to have an angle of attack which minimized drag with the rudder on center, as the rudder rotatated the aft edge of the winglet would become higher relative to the foward edge of the winglet, increasing angle of attack and greatly increasing drag an turbulence.

It would be different if the rudder post were vertical but envelope if the post were verticle the attack angle would change simply due to heel angle and leeway since the flow over the rudder assumes a larger vertical component with increased heel and side forces.

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