Junk Rig Conversion Part 6 - Sewing the Sails

24 05 2013 Posted by Daniel

I took a break in the middle of the dodger project to visit a friend’s apartment cross-country for a week. It was a great space to assemble the sails, so I took full advantage of the opportunity. Carrying a sewing machine through the airport, especially one as heavy as the Sailrite LSZ-1, was not a fun job, but it all worked out in the end.

I don’t plan to go into too much detail on the process here, as sewing junk sails is something of a unique process to each sail and craft, but the general gist of it is well written in many books. Some of the references I have used are:

Practical Junk Rig by Hassler and McLeod, which is considered the modern “bible” of junk rig design.

Thomas Colvin’s excellent Sailmaking, a book written by a man who has spent the majority of his life aboard, building, or designing junk rigs of various kinds, with a particular emphasis on the traditional Chinese styles.

And the fine folks at the Junk Rig Association, in whose company are some of the finest and best known round-the-world and adventure sailors alive today. Without their help this project would not have gotten off as well as it has so far.

I also solicited advice from my designer, naval architect Tad Roberts and fellow sailing conspirator RLW at the fantastic Boat Bits blog, whom I mention here from time to time. His other site, Volkscruiser, focuses on simple sailing designs and philosophy for the average person, and I highly recommend it as well.

So, with the proper credits where they are due, and armed with a bevy of ideas, I set out to translate the design of my sails as handed to me by Tad into a physical creation of cloth, thread, webbing, and brass grommets that would hopefully actually fit my boat.

For those of you hoping for some more technical information, here you go.

Fabric is Odyssey III, a fairly lightweight (~7.5 oz) waterproof, UV resistant acrylic-coated polyester fabric designed as a cover and awning material. As a result it is somewhat more UV durable than standard dacron sailcloth, although I expect to make covers for my sails nevertheless at some point. Total construction time for the two sails was approximately 96 man-hours, but the mainsail took about 2/3 of this as I was figuring things out as I went. The foresail went significantly faster as I began learning some tricks to speed the work up. I believe that, with help, I could knock out both of these sails again in about half the time, especially if I had a more suitable work area like a place with a slick floor and not carpet.

The foresail is roughly 29 square metres, and the mainsail is roughly 31 sqm. in area, each of them have a pseudo-parallelogram for all but the two topmost panels, and the very topmost panel is a large triangular storm sail akin to a “crab claw” sail which reportedly is a very good sail shape for high winds. This panel has an area of about 4.7 sqm. for each sail.

The general sail shape is reminiscent of the suite of sails designed for the famous Badger, sailed by Annie and Pete Hill for many years, with the batten angles changed slightly to enhance the fanning and natural cambering of a flat-cut sail. There is zero camber in the panels. The aspect ratio is pretty close to 3:1. There are 6 battens in the main and 5 in the fore. I’ll go into more detail on the battens, yard and boom construction, and actual rigging in the next post of this series.

Now that they are made and the dimensions doublechecked (they came out within an inch of all expected dimensions!), I just hope they fit the boat!

The following photographs show portions of the process, along with a member of my loyal shore crew.









An "instant" fiberglass hard dodger - Part 3, Putting it all together

23 05 2013 Posted by Daniel

Last I left off, the dodger and arch were roughly in place, but completely unfinished.

After fitting the arch in place, I connected the arch and the dodger via some handrails which I made out of Alaskan Cedar, a strong, lightweight wood.



I bonded the dodger to the deck with a heavy fillet of thickened epoxy and three layers of 9 ounce fiberglass tape.



Once that was cured and sanded, and the rough parts of the dodger filled in and faired, it was time for paint.



The solar panels were refitted, using the mounts I’d fabricated earlier during the test fit.



I very carefully measured, then cut and epoxy sealed the window frames.



And finally cut the windows themselves out of 1/4” Lexan polycarbonate, for which I was fortunately able to find a local direct source (SABIC, the company who bought the Lexan brand, has a commercial sales group in Charleston and has excellent prices as there are no middlemen, effectively).



The end result is, to my eye, quite nice:







After all of that work, it is finally time to rig the sails!


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Comments Closed

16 05 2013 Posted by Daniel

Sorry everybody: due to a huge influx of spam comments, I’m having to turn comments off for the site. Feel free to contact me directly, though!

Just a reminder, you can email me at my first name AT oddasea DOT com.


More updates to come shortly - been busy getting ALETHEIA ready for her first sea trials!

We now bring you this important message...

07 05 2013 Posted by Daniel

My blog buddy Bob over at Boat Bits is running a fantastic giveaway and all you need to do to enter is think for a minute.

The prize is the stunning DVD “Ice Blink” which I have yet to see but very much want to. So get in on the giveaway here.

That is all.


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An "instant" fiberglass hard dodger - Part 2, The Arch

19 04 2013 Posted by Daniel

In the previous installment on this subject, I covered the origin and general construction of a hard dodger for my boat.

The dodger in and of itself is a lot of nice protection, especially for the companionway area and the very forward ends of the cockpit. However, it’s not quite the right size, shape, or position to put the solar panels, nor does it provide any shelter overhead from rain for those sitting in the cockpit proper. For this we need to extend a covering back aft to a strong support where the panels will also attach. The most useful structure for doing this efficiently is to simply put an arch across the cockpit wherever we want it, and to span the space between the arch and the dodger with a waterproof canvas. In this case, the canvas makes good sense because it’s removable if we don’t want it, if it goes overboard in a heavy wave we don’t lose the protection afforded by the dodger, and it’s lightweight and easily replaced unlike the complex shapes of a canvas dodger and frame structure. The arch, on the other hand, must be quite solid.

I designed the arch to be able to do chin-ups on with regularity, although the height is not optimal since it must roughly match the dodger’s. I did not want the arch height to exceed the dodger height, even though that would be convenient for standing under. The main reason was that I wanted the solar panels to be relatively flat in case the sun was shining from aft, to at least pick up some power. Another reason was that it would create even more windage. A hard dodger is effectively permanent windage on a boat, and though I tried to make mine rather low and at least somewhat aerodynamic (haha) it will present some not-insignificant windage, especially in very strong winds. I did not want the arch to add significantly to this.

So the arch needed to match the dodger’s height and camber, and be quite strong. Initially I decided to go with a laminate of plywood (the Luan doorskins again as they bend easily to match curves, are generally a quality wood, and are inexpensive so I can template as I go). I set up the arch shapes for the crossbeam and, just for an extra measure of strength and hopefully some stiffness, I added some carbonfiber tape to the laminate as well. Here they are curing on the forms:



However, despite being much stiffer than ordinary plywood, they were still relatively too flexible for what I was looking for. And in this moment I learned a very important lesson: strength does not equal stiffness.

For a particular structure to be strong it simply needs to be built of materials with high tensile and shear strength. A few layers of kevlar, carbon fiber, or even multiple layers of fiberglass can all accomplish this. However, this often creates a very strong structure that is rather flexible at the same time - much like a willow tree is very strong but also flexible. After some research and consultation, again mostly with Bob, I found a solution. To add the stiffness easily, without adding significant weight or expense in exotic materials, I resorted to a construction called the “torsion box”. In fact, the torsion box form of construction is so stiff that I didn’t need any exotic fibers at all, and so with the exception of re-using the laminate I’d already made with the carbon fiber in it, I made the entire structure out of simple wood, epoxy, and fiberglass as I did with the dodger.

The first step was to re-laminate the arch crosspiece to match the dodger curve. This time, I did it directly on the dodger, screwing the wood pieces together to clamp the epoxy in place. I added an extra block to increase the curve, knowing that to some small degree the entire piece would spring back a bit when I released it. I wanted the natural curve of the piece to be that of the dodger, so this extra block compensates for that springback.



To add the stiffness via the torsion box, I added some 1/2” rips of 1” dimensional cypress wood to the edges of both sides of the laminate. In the photo, the top side is getting these pieces.

The wood strips were then topped with another sheet of plywood, forming a hollow beam with the two layers of plywood as the surfaces and the wood strips as the sides.



I constructed the side pieces of the arch the same way, but was able to glue them up as a complete unit in one go since there was no complicated curve to worry about.



The box structure is clearly visible here.



It makes a very nice wood pattern on the sides too.



The arch crosspiece getting the final surface installed. The epoxy bottles help ensure that the extra pieces conform to the curve already in the previous laminates, rather than trying to pull those laminates straight.



The finished crosspiece is a very nice piece of work. I got a lot of compliments on the dock for this one.



The arch with sidepieces installed, getting a test fit in the cockpit. The dodger is flipped up behind it for a layer of filler before final sanding and painting.



Getting the angles right… note the laminated bases for the arch to adjust the final height, and the temporarily-screwed-in-place side pieces to ensure the feet of the arch stay in position until the epoxy cures. These were super helpful additions to help “flow” the arch structure into the boat and hold it in place during initial curing.



Using some cheap conduit to help align the arch and dodger, and to layout the solar panel mount spacing.

The arch got a full coat of fiberglass, with extra reinforcements in the corners and at the base. I was able to do a chin-up without the arch moving much if at all. It definitely feels rock solid and like a part of the boat!

In part 3 I’ll cover finishing the arch and dodger and installing the solar panels.


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