Sunday, January 24, 2010

Phase One: lofting, patterns, frames, and stems



This first posting is a duplicate of the two postings from the previous Dark Secret project blog. With apologies to Gold Coast Marine Distributors, I have moved the project to this site.

I am building "Dark Secret (everybody else seems to have one; I want mine), William Atkin's 18'7" Valgerda. She is based on the traditional Norwegian faeirngs of Hardangersfjord. Desginer's study plan and commentary are here:

http://www.boat-links.com/Atkinco/Sail/Valgerda.html

She is a very simple boat, and is extremely elegant. Three frames, three planks per side, and a smattering of structural details makes for a manageable project. To those considering building their first boat I highly recommend this design.

I am fortunate to be employed at a boatyard where there is some unused space in the loft above the carpentry shop. This is where the project is happening. In my role as carpentry department head, I find that I spend enough time on the phone, writing estimates, ordering parts, and maintaining tools that I don't get to use my tools (or skills) as much as I'd like to during the work day. Building this boat is basically a way to keep my juices flowing and to stay sharp at something on which I spent a great deal of time and effort to learn how to do.

My intent is to remain faithful to the design, with a few carefully considered modifications. Construction method will be "Joel White Style" - laminated frames and epoxied laps, a la the Nutshell Pram, as opposed to the built-up frames and seam battens as designed. This will result in a MUCH cleaner interior, and will not sacrifice any appreciable strength. I also like the fact that the laps will show on the exterior and give a nice, crisp shadow line. The battened seams, bevelled to meet flush at the knuckles just wouldn't have the same look.

I will not be fitting her with the deep skeg as shown in the plans. I will fit a more traditional skeg, molded about 4". The designer is clear about the fact that she is primarily a rowing boat. The deep skeg will ruin her as a beach boat and won't do her any favors when rowing. The small chunk of ballast will be installed as shown in the plans. It will just be closer to the rabbet. The effect this will have on stability should be minimal. It doesn't provide much righting force, even in its as-designed location. There is a lot of debate about the skeg on this boat in various forums. My decision is based entirely on the boat's intended use.

The only other change I am making is to split the backbone at the apex line. The set-up will be: inner stems, frames, and inner keel (apron), with plywood skin landing on a bevel. Outer stems and batten keel will be affixed after the skin is complete.

I will NOT be sheathing this boat. This also seems to be a point of contention among builders. While she will not be treated like a holy relic, she will not be subjected to hard use. Brass half-oval on the centerline and a pair of runners inboard of the first lap, about 4' long, so that she can lay on her chine on the beach is the extent of bottom protection that will be installed.

I have a copy of "Sailboats and Auxiliaries You Can Build", part of the MotorBoating Ideal Series, that contains the MotorBoating article written by Mr. Atkin, as well as lines, offsets, sail plan, and construction details for this design. I am building from this data. There is one issue with the plans as published: The forward and aft perpendiculars are shown at the stemheads in profile, and at the rabbet line in plan. I did not discover this until well into the lofting process. I will cover my solution to this in a future posting. I don't know whether the full building plans available through the above link have had this rectified or not.

Having me attempt to explain what went on at the loft floor would be a waste of your time. There are many texts and treatises on lofting available, and all of them do a better job of explaining the process than I can. Valgerda is not a difficult boat to loft. There is enough of it involved to gain a real and useful understanding of the process, but not so much that you get bogged down in the minutiae required for a round-bottomed boat.

Before we move from lofting to construction, let's go over some of the infrastructure requirements for this project. Valgerda's size makes her a manageable undertaking. She will fit in a single garage bay. It will get tight in there during construction, but it's do-able. Being built the way she is puts less of a premium on large stationary tools than traditionally built boats. A decent table saw (I used a portable Makita for the bulk of the milling of laminating stock), a small band saw, a circular saw, and a set of basic hand tools will take care of the bulk of the project. The only time you are likely to need a thickness planer is for dimensioning laminated parts after they are removed from the jigs. Laminate them in a batch and you can go to your local voc/tech school or woodworking shop to strike a deal. Cutting the scarf joints in the plywood planking stock might be something you want to do with a power planer, but you may find that it's pleasant, meditative work to do by hand.

Don't underestimate how many clamps you will need. Don't get the good ones, though. You'll be slinging a lot of goo around. Get the cheapo made-in-China clamps. Order them through McMaster Carr. At about $4/clamp, you won't feel too bad if the threads get full of glue and you have to throw it in the recycle bin. If you already have good clamps, protect them by spraying them with WD-40, Lanacote, Boeshield, or even Pam. Also from McMaster Carr, get yourself about two dozen wood-handled ice picks. they are about $2 each and they are great for lofting, template making, and all kinds of other tasks.

As of this writing, I have used about a gallon and a half of Gougeon epoxy. Another gallon should take care of the rest of the boat. I use Gougeon's stuff because I am comfortable with it. There are others out there, but I don't know enough about them to warrant switching. Most of the others are less expensive, but materials are the cheap part of a job like this. You don't want to throw away your labor to try to save a few bucks on glue. The only other big laminates left to do are the breast hooks ("rangs" on a faering) and outer stems.

So, on to construction:

I laminated the inner stems directly over the lofting. I don't have photos of this part of the process. It was pretty straight-forward with a sheet of clear plastic to keep the glue where it belongs. I anticipated a bit of spring-back when the clamps were released, but there was none. Zero. I laminated the stems about six years ago and then put the project away to deal with some changes in my life. When I got going again and laid them down on the lofting, they had not moved a bit.

Each of the three frames has 28 laminates in it. Rule #1 - when planning a glue-up, a dry run is your best friend. It is so much easier to set up your clamps, organize the materials, and spot problems before you mix the glue. If something is going to go wrong, you want it to happen before you have $50 worth of glue mixed up. After getting everything wet out and bent around the jig, spend a few minutes making sure that the laminates are all pushed down as flat to the bench as you can get them. This will make it much easier to run the parts through the planer after the glue kicks. If you are sending them through a planer that is not yours, offer to pay for sharpening the knives. Cured epoxy can do a number on them.

This is as far as I have progressed. Next is the keel, ladder frame, and set-up.

The first photo shows the 'midship frame on the laminating bench. Packing tape on the 2x4 blocking, clear plastic sheet over the bench, and a little bit of Pam on the clamps to keep things from sticking where they don't belong. Don't wear any clothing or shoes that you care about while doing this.

The second photo is a shot of the template for the laminating jig for one of the frames. Above the template you can see a completed frame.