Clipper's Vera Cruise Build

Clipper's Vera Cruise Build

Sunday, May 10, 2015

Middle Bottom Skins Fitting And Install

The two middle skins on the bottom are the largest pieces to be installed. They have a slight curve from chine to keel, easily handled by the plywood. However, at the front, because of where the forward bottom skins end, there is a slight bend downwards in addition to the curve.

This additional downward bend made the butt joints more challenging than I had originally anticipated. This area at the front could be pulled in but only using screws with nuts and washers. Regular wood screws by themselves were insufficient to do the job. 

This meant drilling holes through the skin and backing plates.I was reluctant to do this but in the end had no choice. It turned out that the holes were easily filled when completed. Since the bottom and side skins will be eventually covered with fiberglass, the small holes were not going to be a problem.

On the port skin, I did have a problem with the two forward corners which didn't pull down because of insufficient clearance between the skin and the other installed skins. I decided to cut a small section out and examine the glue joints. Fortunately, the glue joints were solid except in the very corners. The areas I removed were still within the bonding areas of the backing plates and the chine and keel. 

So I cleaned up the area where I removed the corners and replaced the sections with fresh plywood epoxied into position.

 The rest of the skin went down well enough but did require a considerable amount of time to install. The port skin actually took me longer than the more difficult skins at the front of the boat. Part of this was the extra area that required epoxy (three battens in addition to the backing plates, the keel, and the chine). Part of it was the extra time needed to pull in the skins with the screws and nuts (mentioned previously).

 The repairs mentioned above were performed a couple of days after the skin had been epoxied and screwed into position. I also filled in the screw holes and countersunk screw heads with epoxy. Then everything was sanded smooth.

 I spent some time thinking over the install and realized that it was a mistake to try an install something this large by myself. So I have made arrangements to get some help when the starboard skin will be installed next weekend.

I also wanted to avoid the problems I had with the corners on the port skin. That skin had been installed from back to front because I had tried using placement blocks to set it's position and I thought I should try "walking " the panel down to the curve at the front. However, the problem with that approach was that it didn't allow any margin for error in the front fit which led to the corner problems.

Therefore I decided to do the starboard skin differently. This would be installed from front to back, insuring that these critical fit areas were done first. This also gave me more leverage as the skin was laid down because of the length going back and the relative flatness of the remainder of the structure.

Finally, I wanted to allow a little more "wiggle" room for the fit so I loosened up the joint tolerances a bit.

Working from the front to back worked out well during the fitting process. I was able to get the transition joint to fit properly as well a the corner by the keel and the other skin. Since the curve of the panel is at the front and then immediately flattens out, I had the advantage of leverage from the panel. Any adjustments needed in getting the panel to lie flat worked them selves out as I moved aft.

The starboard skin was going to need additional trimming at the keel joint for the entire length. I performed this using a multi-function  tool and a cutting blade. Basically, working a foot or two at a time (starting from the front), I would trim off excess material (but not to the final cut). This allowed me to better see how much remaining material needed to be removed.

Then I would make a second smaller removal which got me close to the final cut. The remaining cut was then performed using a 90 degree air powered die grinder and sanding disk.

 This took most of my time today because I was forced to work on my knees on top of the boat which I could only stand to do for about an hour at a time. Eventually, I completed the trimming and the panel now lies flat across the entire bonding surface. Even better, this time I have alignment marks in place to allow a front to back installation when I do the glue up.

The only disadvantage to the front to back method is that I am going to have to support the aft and middle of the skin (with epoxy already applied) while I fasten down the front before moving aft.Since I will have a helper this time, I anticipate this to go smoother.

The remainder of this week will be spent in catching up on excess glue clean up on the inner surfaces of the skins. On the port skin, the install took so long that I was not able to scrape off the excess on the inner surface like I usually do. This excess will therefore have to be sanded to have it removed.

So that's all for now. I know that the readers out there are probably getting tired of skinning articles. I am equally tired to doing them. Fortunately, after this next install, I only have the two remaining shorter (and flatter) aft bottom skins. But this skinning was originally supposed to be completed by the end of February. It now looks like the end of June before I will be completed, possibly slightly sooner. Sigh!

Anyway, until next time, take care.

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