Archive for January, 2008

1:16 Fiddlehead – Bottom

Thursday, January 31st, 2008

bottomUnlike many canoes, this one has a flat bottom. It is very much like a dory bottom, flat, wide, and with a very slight bit of rocker (fore and aft curvature). One of the benefits of this sort of bottom is relatively high “initial stability,” meaning that it isn’t as tippy as a narrow round bottom or v-bottomed boat might be when you first step in to it. It’s also very easy to construct.

We won’t find boards wide enough for the full width, nearly 15 inches. So, we edge glue as many boards as needed to make up the width. Due to lumber availability, the 1:1 version will likely require 3 boards, and that is what I did for the model. These joints are probably the most critical in the boat. They are edge joins of boards that are 9/16 inch thick, and are fastened solely with glue. The edges have to mate as close to perfectly as possible. They will be a good place to use a #8 jointer plane.

The photo shows how I simply cut out parts of the drawings and rubber cement them to the actual parts for cutting. The technique minimizes a lot of measuring and the errors that come along with measuring.

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1:16 Fiddlehead – Small Parts

Sunday, January 27th, 2008

I shaped some very small parts today, the coaming support knees and the stems. Doubling up boards certainly reduces the amount of sawing. The bulkheads were doubled (opposing grain directions), and the perimeters were cut. Most are straight line facets. Tomorrow: the elliptical holes in the bulkheads.

1:16 Fiddlehead – Mid-frame and Bulkheads

Saturday, January 26th, 2008

the small scale of partsA few of the parts are very small. Don’t sneeze. Some of the parts need to be made in multiples. The strategy for creating multiple identical parts is to glue boards together temporarily. Cut one pattern. Separate the boards. The temporary glue is rubber cement. It holds just well enough to get the job done. The same cement is used to affix paper patterns cut from the plans produced at the start of the project.

jewelers saw and keyholeMost parts cutting is done with a jeweler’s saw that has teeth so fine as to be barely visible.

The mid-frame is made of seven parts, all quite small. These and many other parts of this boat are small both to minimize weight and to get them from narrow width (inexpensive) lumber.

The frame was assembled directly over the plan. A temporary cross spall is needed to keep the frame at the proper width until the planking is complete. On the 1:1 version, this cross spall is a single piece that can be unscrewed when needed. mid frame assembledFor the model, I made the cross spall in a layered assembly that can be readily removed. Trennels, made of bamboo, are substitutes for screws, adding both appearance and strength.

bulkheads laid out for cuttingWhile waiting for glue to set up on the mid-frame, I started the bulkheads. Two methods are described for these parts. One method uses lightweight cedar laminated from two 1/4 inch thin layers. Why not a single 1/2 inch construction? Strength while remaining lightweight is the reason. Laminating layers with opposing grain directions adds more strength than if a single layer were used. The alternate construction uses 1/2 plywood as a heavier substitute. I chose the first approach. Here we see patterns applied to boards that have been edge glued together to get to the needed width.

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1:16 Fiddlehead – Milling the Lumber

Thursday, January 24th, 2008

The Fiddlehead is designed to be a very light boat. If built with the lightest recommended materials, the 12 foot boat weighs about 50 pounds. Weight is kept low by using not only lightweight materials such as northern white cedar, but also using very thin materials. The planks are a mere 5/16 inch and the decking and covering boards thinner yet at 3/16 inch.

The Fiddlehead designer, Harry Bryan, suggests northern white cedar, spruce, and ash for optimal weight and strength results. He also offers suggestions for alternate when those are not available. In general, he advises using what is locally available, but warns it might not be as light. For example, northern white cedar is abundant in the northeast US and rare in the rest of the country. People out on the left coast will substitute western red cedar.

While discussing types of wood, this is a good place to mention woods I use for model building. Some model builders like to use exactly the same woods in a model as used in the full sized boat. I don’t. My reason is that most softwoods used in full size boats have large grain patterns that look very out of place when reduced to scale. Many modelers also prefer using basswood because it’s so commonly available and inexpensive. I don’t. It’s too soft for many purposes and can’t hold a sharp edge. Anytime a part will be finished bright, or will need to have very crisp features, I use boxwood. Boxwood has a very fine grain that can be made noticeable if desired and it holds a sharp edge. Cherry is also good, as are swiss pear, yellowwood, holly and purpleheart. For parts that will be painted, I’ll relax a bit and use basswood or maybe aspen. This model uses boxwood for everything except the planking, sheer clamps and carlins. Those are aspen.

thin lumber on a carrying boardNow, let’s consider reducing lumber thickness to the required size. While this is handy work for hand tools such as scrub planes in full size, we need something a lot more accurate at 1:16 scale. The bottom planks, 9/16 inch thick full size (hereafter 1:1) are 0.035 inch thick at 1:16. The 3/16 inch decking, 1:1, becomes 0.011 inch thick at 1:16. Put another way, 0.011 is 3/4 of 1/64th of an inch. That’s not much thicker than the typical index card or manila file folder material, really thin stuff.

The best tool I’ve found for achieving these delicate results is a thickness sander made by Jim Byrnes of Model Machines. For you 1:1 woodworkers, think of this as a planer that uses a sanding drum instead of rotating knives. We can get to ten-thousandth accuracy with this machine. Yet, the lumber itself won’t tolerate the work forces when very thin. Thinner than about 0.020, the lumber is likely to break when being pushed through. So, I do very thin work by attaching the workpiece to a strip of plywood carrier that’s been milled to a constant thickness. The carrier not only eases the forces on the workpiece, it also helps avoid the “snipe” that often occurs near the ends of workpieces. Rubber cement makes the temporary bond. This first picture shows material for the bottom planks ready to enter the machine.

guding the workpieceThe secret to good results is passing the material through the machine with one steady smooth pass, and doing it the same way every pass. While I can make a carrier of constant thickness, it’s nearly impossible to have one that is absolutely flat. There’s always a small amount of bowing along the length. To counter the bowing, I use a finger (much like a featherboard) right at the mouth of the tool. There’s no safety concern as the mouth is never open wide enough to admit a finger. Then the carrier is pushed smoothly from the end until the workpiece clears the sanding head.

clearing the workpieceI stop pushing the carrier at that point and switch pressure to the outfeed side so that the carrier can be pushed the rest of the way trough, using a push stick, without engaging the carrier against the sanding head. These steps ensure good results for the workpiece and protect the carrier from accidental dings.

measuringLastly, a digital caliper measures the results. I usually pre-calculate the thickness of the optimal workpiece thickness plus the carrier plus a finish sanding allowance and write that down for each piece before I mill it. It’s so easy to keep pushing stuff through the mill until it’s way too thin. Measure once and cut once and you’ll be back for more. The results are so even that I milled all of the lumber for this boat using the carrier technique.

The first milling session produced stock for the bottom, the stems, the carlins and the mid-frame parts, all boxwood. We’ll be seeing pictures of them in coming posts.

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Harry Bryan’s 12 foot Fiddlehead

Sunday, January 20th, 2008

completed modelHarry Bryan drew plans for a classic, lightweight, decked canoe. He calls it the Fiddlehead and has it available in several lengths. I find it appealing because it is built using traditional wooden boat building techniques, has a very pleasing lapstrake design, and looks reasonably achievable as a first boatbuilding project … and we won’t need a trailer to get it to the lake!

Harry Bryan\'s fine plans and drawingsThis will be a dual project. Since my boat shop doesn’t exist yet, and it’s cold out there, I’ll build a model first. My modeling approach is to mimic as closely as possible the full size techniques. So, I expect to learn things that will be helpful when going full scale.

(That picture over on the right is a clue that I’m back dating this build log. The model is almost complete as I write this in May 2008, but the entries are dated closer to when the actual work occurred.)

Like most boat plans, Harry’s plans and drawings are essentially a license to build a boat. After I complete one boat and start another for my wife, I’ll be happy to buy another license from Harry. The plans are four sheets of drawings and a booklet of instructions. The 36 page booklet is in revision 5 and appears to be very complete.

For the model, I scan the plans and reduce to 1:16 scale, a favorite scale for showing reasonable detail while still making relatively small models. A long time user of Adobe Photoshop, I’ve decided to stop paying high priced license fees and have switched to the freeware, open source, graphic editor known as GIMP. Having done this rescaling job before, I’m pleased to find that GIMP handles it just as well as Photoshop. With both tools, the job is tedious and time consuming, but having actual size drawings for the model is incredibly convenient as we shall see.

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