Clipper's Vera Cruise Build

Clipper's Vera Cruise Build

Sunday, August 24, 2014

More Fairing At The Bow

The bow of my boat has been the most challenging area of the build so far. There are a number of reasons. First, it's a continuously changing angle around the curve of the stem. Secondly, because the chine in this area was too far inboard, it was difficult to get the fairing correct so that the two skins that meet in this area will be even. So I am going to cover what I've done so far, and what I've learned.

In the area forward of frame 6, the side and bottom skins meet at the chine and must form a continuous surface. Ideally, they should present a flat surface across the seam, but a slight convex surface would be okay. What I don't want is a concave area because this would then have to be filled with filler before fiber glassing the skins latter. Sort of like doing body work on a car. The dent needs to be as slight as possible so that a  minimal amount of filler is needed to smooth things out.

The "too low" chines meant that shims had to be added to the chines outer surface in  order that this flat surface can be accomplished. That was done and I feel that that surface is now far enough out. In order to test this however, it was necessary for the fairing on the stem to be accomplished as well. What made this difficult was that the angle of the fairing on the stem is dependent upon the outer surface of the chine. So what I had to do was try to get the chine as close to where I wanted it to be first, then fair the stem, and finally test the fit of the two skins in this area. This has taken several weeks.

To fair the stem, I wanted to have notches cut every six inches. Each of these notches would have a slightly different angle downwards towards the chine. The idea here is that a straightedge, laid into the notch, would lie flat on the chine. In order to cut these notches at the correct angle, I used the same alignment tool I've used elsewhere. I added a length of straight lumber to it, parallel to the bottom edge, essentially an extension of the bottom edge.

In order to get the correct angles, it is necessary to measure around the curvature of the stem and the chines. Using a flexible steel ruler, I made marks every six inches. I also added a center line to the stem. The alignment tool is placed in position with one end on the 6 inch marks where it crosses the center line on the stem. The other end of the tool is lined up with the six  inch marks on the chines. The next two photos show this.



The tool was clamped to the chine so it wouldn't move and then I used the tool as a guide for my Japanese pull saw to cut slits. These slits would be cut until the blade reached the center line of the stem and was also parallel and just up to the chine surface.


A series of slits were made approximately 1/8" apart for about an inch. Then using a chisel and hammer, I chiseled out the slits and filed the notch smooth. The notch should be parallel to the chine surface.




At every six inch mark moving aft along the stem, this process was repeated until I reached frame 6. I did not continue past that point for reasons I'll get to in a minute. These additional notches are at slightly different angles and are all parallel to the chine. They represent where the fairing needs to be taken to when removing the remaining material.


At first, I thought that this process could be continued around the remainder of the stem as I moved aft past frame 6. But on my boat, the skin forward of frame 6 is flat, but the skins form a curved surface aft of frame 6. A straight line used to cut notches would have made the notch angles too sharp as the straight line from the notch to the stem would have cut through the curve of the skins.

However, before I realized this, I went to the trouble of determining how I was going to use that previous method to cut the notches. Although I am not planning on using this method in this area, I feel that this technique might be useful to get the approximate angles needed.

In this area, the chine is no longer parallel to the notches. A notch would have to be cut into the chine  in addition to the notch cut into the stem. I laid the alignment tool in position as before, aligning it to the six marks and the stem center line. The long tail of the tool extends away from the chine at an angle.



Using some basic geometry, I determined how far the angle was from the center line of the chine. This distance was marked on the upper surface of the chine in the six inch mark area. If the notch were cut, this line would be the extent of the cut (along with the center line on the chine).




As I mentioned however, I believe these notch angles would be incorrect. At this point, I am not yet sure how I am going to determine what angles these notches should be cut at. when I have figured that out, I will post something in my next article.

The remainder of this posting will cover the additional work I accomplished forward of frame 6. After having cut the notches on the stem every six inches, it should have been a simple matter of removing the material between the notches, blending the slanted forward edge into each notch. I proceeded to remove one section between the first set of notches.

At this point, I wanted to verify that the two skins would indeed lie flat across the center line of the chine. For the most part, the angles on the stem are correct. I've had to do a bit of tweaking but I felt confident enough to begin removing more of the stem material. After each section was removed, I had more mating surface available to test the fit of the bottom skin, so I would check it each time before moving on to the next removal.


Eventually I reached frame 6 and stopped there. All of this was accomplished on the starboard side. I still have to do the port side. Aft of frame 6 will have to wait until I can figure out the notch angles and how to make them. Here is what it looks like so far.




In the previous photo, you can see that frame six has been partially removed at the very end. This is the remaining work I accomplished in this session. Like the frames further aft, limbers must be cut into the frames to allow water to drain aft. That is why this small area was removed. It still needs to be cleaned up and the edges rounded. I'll accomplish that later when I have completed fairing.

In this last photo you can see the limber cut. You can also just make out another notch in the stem. This notch was cut parallel to frame 6.


I'm beginning to feel that fairing is getting closer to completion. For quite some time now, I have been kind of bummed out as I encountered and had to deal with the problems around the chine. But now, I am starting to get the more difficult parts of the fairing accomplished so I am feeling better about the progress.

I am hoping to compete fairing by the end of September. If I can, then I should be able to start fitting skins by the end of October. I figure that October will be occupied with quite a bit of clean up work and re-encapsulation.

Anyway, that's it for now. I'll bring more information when I have enough. UN til then, take care.

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