Clipper's Vera Cruise Build

Clipper's Vera Cruise Build

Saturday, April 5, 2014

Fitting The Chine Blocks - Part 1

The chine blocks (or simply chines) connect the middle frame corners of the frames together. They provide a place to attach the outer skin at the junction between the side of the boat and the bottom. They are also a major structural member of the boat and therefore require lumber that is quite thick, in my case 1 and 1/4" inches thick.

The other thing about the chines are that they are curved to match the shape of the boat. They start out fairly flat at the aft end of the boat but gradually curve inwards as they move forward. By the time they reach frame 4, the amount of bend is getting to the point where any further bending will be difficult to do and would most likely break the lumber. From frame 4 through frame 6 the bend gets even more severe  and then the chines attaches to the stem at the bow.

I plan on using steam on these parts of the bend which should soften the wood sufficiently and make these severe curves possible. But before I can get to that point I have to fit the chines to the frames at the aft and middle sections. That is what I will be covering in this article.

First off, I want to make a correction to a statement I made in the last article. The following photo showed the chines temporarily;y setting in the transom frame and I indicated that the chine would be faired away on the top edge and sides to match the frame contours.

This is incorrect. The chines do have to be faired away on the bottom edge  but they should be mounted to the frames in a manner where the chine sides are approximately parallel to the frame sides. So in the previous photo, the chine would need to be rotated counterclockwise some until it's long side is the same as the transom side. You can see that in the next photo near the foreground.

What you want to do is trim the frames to match the curve of the chine, but the outer chine surface should be relatively flat so it provides a mating surface for the plywood skins. The next photo shows how frame 4 will eventually need to be faired to match the curve of the chine. The curved chine is horizontal in the photo and you are looking down on frame 4. You can see how the frame sticks out beyond the chine.

Each frame needs to get a custom notch cut into it's corner to match up to the chine. The angles of the cut must match the angle that the chine intersects the frame. The previous photo shows this, however, that notch is still not quite right and needs to be trimmed more on the right side.

The way I tackled this was to start by temporarily clamping a shorter piece of stock in place to get an approximate idea of how the angles looked.I marked these angles and then proceeded to cut out the first notch. When doing this, you want to proceed slowly and cut the notch shallow. 

The process is, make an initial cut, fit the chine into position and see what corrections need to be made, then cut a little more. Fit again and make more cuts. Repeat this until the notch is correct. Each time, be careful not to cut too much material aware from the frame. Be cautious and go slow. Also be aware that as the chine lies further into the frame it's relative depth in relation to the frame changes. So it is quite easy to over cut the depth of the notch.

What you want to end up with is the outer upper chine corner higher than the frame and the inner upper chine corner slightly higher or even with the frame. You can see this somewhat in the following photos.

The cool thing about the chines are that when they are in position, you can actually see the shape of the boat. The next two photos show this. You can also see that I had to use ratchet straps to hold the chines into position. You're looking for a nice gradual curve as the chine moves from frame to frame.

To give some idea of the bend needed at the bow, I took the next couple of photos. The pictures don't show it real well, but  you can get some idea of what will be needed. The first photo shows the chine still needs to be bent more to even touch frame 5. In the second photo, frame 6 is in the foreground and the chine would eventually have to bend to meet this as well. Forward of frame 6, it curves even more to meet up withe stem at the bow.

You will probably notice in the previous photos that the chine does not appear to be long enough. This is correct. That piece of lumber is 17 feet long but the chine needs to be approximately 22 feet long. This will be accomplished with a scarf joint like I used with the keel. I have already performed this on one of the chines.

The next photo shows the sharp angle needed for the scarf joint where the two pieces of lumber are glued together to forma a longer piece. This is approximately a 5 degree angle which gives approximately a 1:12 gluing surface for the thickness of these pieces. I cut this angle using a router and the scarfing jig I made several months ago for the keel. I had to change the angle pieces on the jig for these parts because the keel was cut at approximately 7 degrees.

The length of the chine is too long for my garage so I had to glue it up outside. The glued up pieces are actually about 24 feet in length so I have extra material to work with as I fit the chine. The scarf joint needs to be in the aft end of the boat between frames. So I will have to trim extra material off the lumber as I do the final fitting.

After the epoxy cured sufficiently, I had to place it into my garage kitty corner until I am ready to do the final fitting and installation. Needless to say, having to work around this is a pain in the neck. I have already bumped my head on this at least four times. It would be nice to have a larger shop to build in.

The epoxy on this scarf joint should cure for at least several days to ensure maximum strength. As I start making the bends at the bow end of the chine, there is going to be stress on the scarf joint at the aft end. I want to insure that it does not come apart. I had to be extra careful when gluing this up so that there is sufficient glue in the joint and the joint is nice and straight.

So next week, I am hoping to buy the apparatus I need for steaming. I still have to glue up one more chine and both of them will need the glue cleaned up. I also have some tweaking to do on the notches and a few shims to make for slight over cuts. I will cover more of this process in the next posting. 

Take care until next time.

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