Clipper's Vera Cruise Build

Clipper's Vera Cruise Build

Sunday, February 8, 2015

Bottom Battens Part 1

Before the bottom skins can be applied, the remaining bottom structure must be completed. This means the battens. Battens are the longitudinal pieces that run fore and aft and provide additional stiffness to the bottom skins.

On this boat (and many of the other Glen L designs), the battens are partial, meaning that they do not run the full length of the boat . I am not sure about the reasoning behind this, but I suspect at least some of it has to do with the difficulty in getting these pieces to conform to the curves up front.  I have seen other designs that use a narrower batten width and all of them run from the transom to the stem and connect on both ends.

On my boat, the plans call for 3 inch wide battens. The inner most one (closest to the keel) runs from the transom to just past frame 5. The middle one runs to just past frame 4, and the outer one (near the chine) runs to past frame 3. The amount of batten past the frames varies with the outermost extending the farthest past the frame. These loose ends are intended to eventually be attached to the skin but needs to be loose so that they will conform to the curve of the skin.

Before I could install these parts, I had to do some minor fairing on the bottom and I also wanted to see just how good the fit of the ends of the battens would be when lying against the skin. The one that concerns me most is the innermost batten. It extends past frame 5 into the extremely curve bow section and must not only bend back down , but also twist outboard (more on this in a minute).

In order to test the fit of these parts, I had to first insure that the skin would lie down flat. This is where the minor fairing on the bottom came into play. Frame 5's bottom edge still needed some trimming and sanding in order for the skins to take a nice curve around the frames and boat.

This took about two hours of attaching and checking where the interference was, removing the skins and sanding down the interference and then checking the fit again. After about four tries I had it where I wanted it.

Then, I had to clamp the battens in place and test the fit of the skin over the loose ends of the battens. Since they are not attached on one end, they tend to stick out straight from the last frame they are attached to. This straightness interferes with the skin fit to varying degrees. As mentioned before, the innermost batten has the worst fit.

After clamping the scrap piece of plywood in place, I took a look at the batten fit and was pleased to see that the outer two battens laid up against the skin nice and flat. Just what I was hoping for. In the following photos you can see a gap where the skin lies on the other batten and the keel, but this is simply because I was not applying an external pressure on these areas. I did test these areas to insure they would fit correctly and they only need a minor amount of downward pressure to fit perfectly.

However, the innermost batten was definitely going to be a problem. It only extends past the frame about 10 inches so it is fairly stiff at the end. You can see that in the following photo.

In this photo, looking at the batten end on, it appears that the batten lays in the same general plane as the frame curve, but it sticks straight out and that is where the problem lies. You can also see the difficulty I had in clamping this in place. This is only the fitting. When I glued it up it took four clamps and a ratchet strap to hold down while I added the screws.

There are a few ways to deal with this fit problem. One is to do what is called kerfing; basically slicing a slot in the end of the batten back to the frame. This slot is cut crosswise through the end of the batten from the end.. What you are after is two thinner pieces that can be bent more easily.

I wasn't sure this would work on my battens because of the short length past the frame, so I was reluctant to make the cut in the part. I tried experimenting on a scrap piece of lumber similar to the batten material and I didn't feel confident in this approach. I do know that other's have used this approach with success and it is called out as one option in the "Boatbuilding With Plywood" book I have.

 A second option is to use steam on the end and apply the twist and a slight downward bend. After studying the part in place for quite awhile, I feel like this is the approach I am going to use. The part only needs a slight outward twist at the end and a slight downward bend in order to fit under the skin. If necessary and this doesn't work, then I will kerf the ends.

Today, I decided to begin installing the starboard battens. At first I thought this was going to go quickly because of the limited gluing areas, but the difficulties with clamping and the fact that I had to repeatedly crawl under and through the boat to do the work made the first batten (the innermost one) take several hours to get into position.

The main difficulty was in clamping the front end down while I added the screws to hold it permanently. As with other parts of the boat structure, these are attached with a combination of epoxy and screws, so I was also fighting the pot life of the epoxy. I finally used a combination of clamps (some to hold the other clamps in position) and a ratchet strap to get the batten in it's correct position.

Screws were added and then the excess glue was cleaned up. The middle batten and the outer batten went in easier, although the middle batten also required a sister batten on it's inner edge. This sister batten is so the motor well sides (which will be added at a future date) will have a way to tie into the boat structure. This sister batten required a bit of extra work to get into proper position.

All three of the battens also have backing blocks under the aft end that reinforce them at the transom. This reinforcement is needed because of the limber passages I cut in the battens (see last week's posting).

So after several hours , I ended up with the starboard side battens completed. I still need to let the epoxy cure and then do a bit of clean up on them, but they are in position. It also looks like the inner most forward end may actually need less tweaking than I originally thought, but I won't know for sure until I can test the fit in a few days.

One other thing I've started doing is getting the side skins ready for fiberglassing. There is quite a bit of work that needs to be done before this can occur. The first step is to fill in all the screw holes with epoxy. So I filled the holes on two of the starboard skins. These will be sanded smooth before any of the other prep work is accomplished. I'll cover more of that in the future. Since there are so many holes to fill and I am not particularly fond of sanding, I am doing this in stages.

So that's it for this week.  I basically have to repeat this entire process on the port side. I will also be doing a lot of sanding. So the next several weeks may have less "photogenic" material to show. At any rate, I am happy to get this one side done and I look forward to getting the skinning completed.

Until next time, take care.

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