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Completing the pattern cutting

I cut the last few patterns from the hardboard this evening, stations 0, 0.5, 6 & 7. After this, I will sand down the outer edges of the hardboard exactly to the pattern lines, cut out the strongback holes, and drill holes in the control lines (c/l and w/l). Then I'll be ready to tack these hardboard pieces down to the particle board, and rout around the pattern to get the stations.

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Cutting the patterns

Today was the day for cutting the patterns out.

I got started around 1:30. After doing one small piece, I realised I needed some eye and nose protection. I ran off to ACE hardware and picked up some safety goggles and a facemask; I already had earplugs.

Manouvering the jigsaw (I bought a Skil 4580) was pretty easy. The supplied blade broke after about 1/3rd of the way through; I picked up 6 new Bosch blades with 20 teeth per inch, and they cut much better than the Skil blade did. Another one of these blades broke as well, but this didn't phase me as much (it was getting dull anyway).

I found it easiest to sight down the left side of the blade, which meant cutting counter-clockwise around the patterns. Generally I tried to cut off parts of the hardboard so I wouldn't have to make many curved lines in the middle of the board, although that doesn't work out all the time (sometimes the distance you have to cut isn't worth it).

Each station took around 30 to 40 minutes to completely cut out, depending on the size.

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Construction begins

Last night Tamara gave the OK to start building, even though we haven't moved into the new house. I went down to Home Depot (Lowe's didn't have 1/4" hardboard) and picked up the first elements for the station patterns.

Greg on the mailing list had a great idea:

One more tip. If you are just about up to cutting your sections now. Consider gluing the paper sections on thinner base material say 1/4" hardboard (Masonite to you Aussies). Its easier to sand to the exact size. Drill holes through the control lines then overlay it on the station particle board and rout around it with a top ball bearing 1/2" diameter pattern/flush trim cutting bit (MLCS 2 flute carbide # 6506 1/4" shank $15) . This will leave you with an exact copy of the section plan. You can mark the control lines on it and the scrap piece is 1/2 inch larger all round and so with a 1/4" carpet padding will perfectly fit the bottom of the hull when it comes time to rotate the hull. It would also be a good template to help make the cedar cradle and dolly.

That MLCS router bit is here.

This is a great idea, and it's what I decided to do. I picked up three sheets of 1/4" 4x8 hardboard, and one sheet of 1/2" 4x8 particle board.

This morning, after dropping Tamara, Tristan, and grandma at the airport, I started in earnest. Per the instructions, I did the following:

• laid out the full sheets on the 4x8;
• drew a positioning line along the top edge and the side edge;
• marked the centerpoint, to make it easier to line up the sheets when the adhesive is tacky;
• sprayed 3M Super-77 down;
• placed the pattern down, then smoothed it out from the centre outwards;
• trimmed away the excess paper, 1cm from the outer edge of the pattern;
• pressed the pattern down again, especially along the edges, to ensure it's tightly glued.

All this took about 5 hours from start to finish. I used two medium (270g) containers of Super-77, although I probably could have gotten by with just one large one. Towards the end, I put a lot on the hardboard; this ensures a good bond, but on the downside it can get stuck to the guide on the jigsaw and cause a gluey mess stuck there (in one case it ripped the edge of one of the patterns).

The Super-77 is pretty forgiving, although it sets up quickly. Getting a good bond (especially if you're being stingy) has to happen pretty quickly, within 20 seconds. You can the pattern off and reposition it, but you have to do this quickly.

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Stations

Well, I spent some time and pulled measurements from the plans (have to do something to pass the time until we move and I can actually start construction).

I bought 3 sheets of 18x24 vellum. I drew a line down the left side of one of them, 1cm from the edge, and a waterline 20cm up from the bottom. From these two lines, I carefully plotted a 10 cm x 10 cm grid; along the 10cm lines I put a dot down every 2 cm. I then stacked all the vellum on top of each other and used a pin to transfer the points through to the other sheets (but didn't bother marking them). Align the dots together and tape the three sheets together vertically.

Now put the vellum down on a pattern, and line up the centerline and the waterline. Using the 2cm dots to ensure the ruler is straight, move 2 cm from the centerline or waterline each time and move your ruler down first parallel to the waterline, then parallel to the centerline. Measure the distance from the reference line to the intersection of the hull line.

The results are pretty to look at, but probably not terribly useful. Because the allowed margin of error is ¼”, there is likely enough error in my measurements and the resulting numbers that you couldn't build a compliant boat from the numbers. Bram's patterns converted to metric have precision to four decimal places, 100x more accurate than these.

Measurements

Bram posted a while back that he had tried to use Kinko's large poster copier to make copies of the plans, and that the results had been less than satisfactory. The copies had come out by up to 1/4" off. I've already been down there to make copies of the plans (just before his post, actually) and thus I figured I would measure the originals to see what the copies are up to. Here are the results (all measurements in centimetres):

Pity. It looks like the Kinko's poster copier is out about 1 cm in 200 (about 0.5%), and it adds width, not height. The errors are all quite consistent, right between 0.4% and 0.6%. Since the class only allows an error of 1/4", this won't cut it. A $50 photocopy job rendered useless.

What I plan to do is create my own lofting sheet from the plans, and use the masters for the templates and station molds.

Note that point '2' on this graph is really station 1/2, so the slight deviation from a nice curve makes sense, since if it was correctly placed the graph would be smoother.

My number

Bram has posted sail numbers. I am USA 012.