Adding seats

Well I know I've been too busy when I can't get to something I enjoy like messing in boats. Tomorrow Spring starts!

Back to the drawing board (or computer). This time adding seats. I've got two options, build seats as part of watertight bulkheads or if that's too heavy-one with simple seats and canoe floating bags. I'll use freeship to do most of the estimate. I prefer the watertight bulkheads because it's safer because it adds flotation abeam which makes is inherently more stable than float bags or compartments at the end of the boat.  It also serves as storage for dry cloths after recovering the boat.

Most of the advise I see online from Woodenboat (http://www.woodenboatpeople.com) about seats say they need to be at least 7 inches off the floor and about 6 inches below the oarlocks. I've got 14 inch mid ship height, so I'm going to go with 8 inch seats (from baseline). The aft seat will be for my wife, not for rowing so I'll make it the same height so oars can lay flat for short periods. The bow seat shear hieght will be about 16 or 17 inches, so I'm going to make that one 9.5 inches from the baseline. Using the dialog box I chose not to show all the layers (e.g., bottom, sides etc) but leave the control lines so I could continue to see the hull as I placed the seats. Below is the perspective and plan view. Note, I haven't trimmed off the excess where it intercepts the hull. I'll do that next time.

In freeships the easiest way to make seat is add the points away from the boat, select all the points, create a layer/face and finally use transform>move to place it on the hull. I used edge>split to add a curve to the seats; it adds no functional improvement but aesthetically makes for a pretty boat.

Adding a skeg

Most dories have skegs to improve directional stability while rowing--probably a good idea given their flat bottoms. I decided to design a simple one made of 1" stock (3/4") a couple feet long and curved so the wear and tear from dragging the boat around wasn't on one point. This would also allow me to add a protective metal half round if I wanted. Many skegs running deeper than the bottom amid ship, but I decided to make it the same depth. From other boats I've rowed there usually enough water flow upwards towards the stern to provide plenty of grid. Also I've seen several boats with longer skegs damaged after some rough treatment being pulled on shore or hitting something underwater while drifting sideways.   Keeping it small would save weight and less vulnerable. If it doesn't work, I can always laminate another strip on the gentle curve.

Just as a started a noticed a problem. I'd designed the transom to a point. My first task was to make it the same width as the skeg. This isn't very hard in Freeship as long as you're careful to preserve the surfaces as you extrude edges, remove or add point and edges. Here are the results:

To add the skeg I selected the three aft bottom center edges and extrude them vertical by about 4 inches. Like this:

I set the vertical height of all the bottom points to zero, adjust the most aft so it slopes in line with the transom and round the two corner points. Next I extrude the whole skeg transverse by 3/8" which is half the final thickness. That completes the skeg (see below). I left the control points in view so you can see how the rounded corners work.

Next time  I'll be designing the seats, and thinking about the framing and bow construction.

Curvature progress

 Last time I discussed the flat spots in the curvature. Control point by control point I went through the chine. The curvature tool and ability to move the view into any perspective helps here. After a few hours things are much better. First the dory using the curvature tool again.

The curvature is much more uniform along the length of each chine.
Here's an idea of what the hull looks like, with some color this time.

Converting to Freeship....problems

Imported the lines from Hulls into Freeship. I allowed internal stations to be imported so now there are 10 stations.

I pull up the linesplan, which shows all the plan, profile there are at least two obvious problems.

1) The stem is misshaped. There's too much of a bulb at the lower chine.

2) The bottom plan view (looking down) is odd and hump where Hulls station 4 used to be instead of a smooth transition from bow to stern.

To confirm what I'm seeing isn't an optical illusion from the lines, I select the edges and curvature change (purple in Freeship). . To confirm that, I choice perspective view, and select all the chines. Now I can see the double hump in curvature and slack curvature near the bottom mid-frame; not only that but all the chines show a similar slack.  This is probably a problem of how it imported from the 5 station shape and interpolated it into the 10 stations of Freeship. I've got work to do....

modifying the dory...making it mine :-)

A note about getting Hulls to run on a modern machine.

I've been playing with Hulls for about ten years used it to design another small boat, and as a recreation even during my time in Iraq because it ran on my netbook. I'm running 64bit Windows 7 Home Premium doesn't have a built in emulator. I think Hulls is a 16 bit program so there was no easy way to get it to run. To make a long story short, I installed a free program called VMWare Player, which is a virtual machine program, dug through my closet for and old copy of XP professional and loaded it up. Windows XP and Hulls work really well.  Here's the web page for more about VMWare Player, http://www.vmware.com/products/player/

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As much as I like the dory, it was really too heavy and more boat than I needed. 

Every boat is a compromise. What I wanted to do is nudge this excellent design towards features I wanted while decreasing some features that I didn't need.

My first priority was to lighten the boat, I narrowed the hull by two inches and reduced the bow freeboard by four inches. That's a lot and risk ruining the shear line, so I'll need to be careful.

I wanted better initial stability so widened the bottom by about 4 inches. Hulls makes it easy to rescale the entire table of offsets based on changing length, height, or beam.  

A few aesthetic concerns. To make the boat look even more like a swampscott dory, and dispel the plywood slab sided look, I added another chine. To do this I just took the mid height between the existing 2nd chine and the shear line. I also added slit round.  

As much as I like dories, I'm not a big fan of wedge shaped dory tombstone transoms. Using the added chines, I rounded the transom sides. 

To compare the two boats: 

FSK Dory

LOA: 12' 3”

BOA: 3' 6”

LWL 2'
BWL 2' at 300 pounds which is boat plus one person

Height of the bow: 24 3/4”

Height of stern: 17 3/4”

Height of mid shear: 14 1/2”

Weight: 120-150# (estimate from traditional construction)

Lynx Dory

LOA: 13' 6”

BOA: 3' 4”

LWL: 11' 7”

BWL: 2' 10”

Height of the bow: ~21”

Height of stern: ~17”

Height of mid shear: ~15”

For the next blog post I'll convert into freeship.

Getting started....The Lynx Dory

As a start point I used a cute dory designed by Francis S. Kinney featured in Skene's “Elements of Yacht Design” It's 12 feet long, which is small for a dory, and has two chines giving a slightly rounded sides suggesting a Swampscott dory. Several people who've tried them report they were delightful rowers for being so short, good cargo haulers and far more capable in waves than most boats its size. Of course being a dory, it's a bit fiddly with low initial stability, not the type you'd want to stand up in, but having great stability with loads or heeled well over.

To start I plug the lines directly into Gregg Carlson's Chine Hull Designer, each bulkhead in Skene's book corresponding with a bulk head and Hulls (though in reverse order). Hulls allows direct entry into the table of offsets. The results are below. 

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As a bit of exciting news. John Welsford commented on his Yahoo groups page http://groups.yahoo.com/group/jwbuilders/  that plans for Pelegrin, a cabin version of Pilgrim will be done in the next month or two. (If you haven't seen Pilgrim take a look at chip's page http://www.flickr.com/photos/chipspilgrim/) A sturdy gaff-rigged cutter it might make the perfect boat for exploring any rugged coast with as much comfort, safety and attention from bystanders as any 17 foot boat can bring. I can hardly wait!

Ok...now the hard part. What type of boat do I want? I like just about all small boats. I've owned a number of small boats over the years including an

o Old Town 13' Discovery canoe,

o 15' Mike Snook's Merry Wherry rowing shell,

o John Welsford's 8 foot Tender Behind,

o Selway Fisher's 12' dory,
o 12' home designed sailing skiff, and a

o Joel White's 12' Pooduck Skiff

That's quite a range and I liked them all!

Which ones did I use the most? The canoe, the skiff I designed and the rowing shell. Why? Because the others were heavy, which required either breaking my back to pull them up on top of the rack, or a trailer which limited their use to where ramps exit.

How will I use it? For fly fishing, photographing wildlife, and slow explorations of ponds, slower rivers, and marshes. On nice days my wife will keep me company. Sometimes I'll be in Puget sound among the wakes of motorboats.

I love canoes but I'll be by myself most of the time. Rowing is so much better for making miles, exercise and tracking in a crosswind than steering alone from the stern of a canoe. Rowing shells are good for mileage and exercise, but too unstable for comfortable fishing.

I'm looking for something I can row, light enough to throw on top of a car and carry a small adult passenger.

I've made a decision, but will spend a few post going through what I'd been thinking the past few weeks.

Ray