Clipper's Vera Cruise Build

Clipper's Vera Cruise Build

Wednesday, October 10, 2012

Bit Of A Setback To Deal With

I began work on the third frame last weekend by laying out the frame outlines on my plywood layout board. When I went to match up the pattern to the layout, it didn't match up. Further checking of the pattern against the plan measurements showed that my assumptions about certain points on the patterns were wrong and were actually short of the mark in some cases.

What this means is that some of the parts were made too short. The shortage is not a great amount, but it throws off the entire frame if not compensated for. Being suspicious about this, I decided to go back and check the frames that I had already worked on. I found that they too were a bit off.



This is all rather embarrassing because it means that I was not careful enough when doing the initial layout of frame parts. No excuses here, I simply missed this step in my process and didn't notice it until later.

So what this means is that I have to step back and re-evaluate my work. I did that on Sunday and determined that I needed to correct nearly all the pieces. Fortunately, the amount of shortage is small in almost all cases (typically less than 1/8")  and can be compensated for by laminating a small piece of wood on the ends of the frame parts.

Determining the exact amount of shortage however, requires a different way of doing the initial assembly on the layout board. Previously, I was using the patterns, lining them up on reference lines on the layout board, and then drawing the pattern outlines. Some of the patterns had to be flipped over a centerline and duplicated. I made sure that these were identically placed. But what I neglected to do was compare the layout size to the measurements on the plans.

The new approach I am going to use is to layout the measurement points of the frame on the layout board. These points are where the frame meets the keel, the sheer, the chine block, as well as measurements from a centerline and baseline below the frame. Then I am going to align the patterns to these measurement points and draw the outline of the frame. Finally I will align the parts I've made to the outline and see how much they are short of the measurement points. Once I have these figures, I can go about correcting the parts.

Since the frames will be slightly wider and slightly taller than I originally thought, some of the plywood floor timbers and possibly some of the gussets may no longer fit. I haven't determined this yet. Fortunately, I have only made a few gussets and floor timbers so if these parts must be made over , I have not lost too much plywood. The biggest loss is the time it will take to redo some of the work.

In order to use this new approach, I determined that I needed a second plywood layout board attached to the original board. This gives me the room to layout a baseline to measure the measurement points from. I have purchased this additional board and will be attaching it to the original board this evening. I also plan on putting a coat of flat white paint on the boards to make it easier to see the measured lines and points. I hope to have this initial work completed by tomorrow.

Then I can begin the layout of the measurement points for the frames I've already worked on and begin correcting those parts.

Finally, because I've mentioned these terms several times and will certainly have to mention them again, I wanted to give a quick explanation of what the keel, sheer, stem, chine, and batten components are.

If you think of the frames as defining the shape of the boat when viewed from the front, and imagine them placed standing up so that they are spaced apart lengthwise to form the length of the boat; you can then imagine that they need to be connected along that length with additional lumber.

This additional lumber defines the shape of the boat lengthwise and further defines the shape of the boat in three dimensions. The keel is a large piece of lumber at the very bottom of the hull that is essentially the backbone of the hull. Most of the frames are connected to this as well as the stem of the boat. The stem is a part that serves to define the shape of the bow of the boat and is also a sort of backbone for this area.

The sheer (or sheer clamp) is a long piece of wood that runs from the bow to the stern along the top edge of the hull. Think of it as the edge of the boat if you were going to climb into the boat. It defines the shape of the top of the boat and serves as a structural connection between the frames and the bow of the boat.

The chine (or chine block) serve as similar function as the sheer except that it runs at the point on the hull where the sides transition to the bottom. This corresponds to the points on the frames where the frame sides transition to the frame bottoms. The chine also serves as a structural connection between the frames and the bow of the boat.

The battens are simply long pieces of wood connecting the frames and are laid between the sheer and the chine as well as between the chine and the keel..They serve as attachment pints for the skin of the hull. and further define the shape of the boat in three dimensions.

The image below illustrates these parts




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