Keel frames with the top web half glassed
There has not been much action on the boat building front due to a trip to Perth and three scheduled sailing days since then. It took longer than expected to glue the doubling blocks to the middle of the keel frames and router the edges of the completed units. It also took longer than expected to lay up the first three layers of 495 gram unidirectional glass on the top web of the frame. That is the stage of the photo below. Since then I have added a further two layers to get my target 2 mm of high strength epoxy glass. I estimate the design strength for the unidirectional laminate to be 300 MPa or about six times the strength of the wood onto which it is bonded. Conceptually the 2 mm of very high strength epoxy glass is in tension equivalent to 12 mm of timber which would give a similar strength to a 60 mm frame compared to the 48 mm design. It is not quite the same as the extra depth of 12 mm timber would give different area moments to resist the keel but it is pretty close. Just to be conservative I have assumed a design strength of 150 MPa and I have topped off the five layers of unidirectional with a layer of biaxial under the keelson because once the keelson goes on there is no further opportunity to reinforce the frames. All this glassing is a lot of work and messy work at that but we are installing a deeper keel to improve the windward performance with more righting moment and more lift.