Notus Racing and Cruising Canoe: An exercise in using FREE!ship

The Notus beckons back to a simpler time, a time when racing sailing canoes were/was all the rage, and people attended to these poor person’s yachts with all the love and tenderness, as they would have spent on massive sailing ship. In 1887, R.W. Gibson had the Notus built. It was a refinement of another canoe, the Vesper. It has some of the most striking lines of any sailing canoe from that period.

Although I’ve looked at these canoes before, I’m a relatively new convert to loving these designs, and I hope to learn as much as I can about this period, and I recently found out about FREE!Ship. So, I figured that why not combine both my new found interest and a newly found boat design program. So, in order to try out Martijn van Engeland’s FREE!Ship’s ability to import offsets, I decided to use Notus. What follows is a set-by step account of how I translated the Notus offsets into Free!Ship, and then added a deck, cockpit, and sails. You will also find the file that I used to input the offsets, and the final two versions of the Notus in Free!Ship format. One is with the sails and one without. And also included with this tutorial is a handy excel spreadsheet to help with the conversion of offsets to a readable format for Free!Ship.

Most of the tutorial was posted originally on the Canadain Canoe Routes Forum.

Why Do This? What Does it Have to Do with Lightweight Canoeing and Kayaking?

Simply, it’s a really good way to see some of the old Rushton designs that Nessmuk paddled (This canoe isn’t a Rushton design, but the Vesper was built by Rushton.), and it’s pretty fun to see these old boats become 3D representations, but also by studying the hydrostatics and resistance numbers of the old designs we can learn from them, and, hopefully, gain a greater appreciation of canoes and kayaks in general. I can imagine a future where when around the campfire, our thoughts and discussions go back to the classic designs of the late 1800s and early 1900s carrying us away to a time when sailing canoes dominated the scenery with their graceful sails and flowing lines. And if we’re lucky, I can imagine a future where sailing canoes once again grace many lakes, ponds, and rivers where I like to paddle.

Getting Started

First, you should read the manual, because it will help you get used to the concepts used in the program. If you’ve never used a program for boat design or 3D graphics before, this program will probably feel slightly foreign to you, but a little practice will go a long way, and by using the steps outlined below you will, hopefully, be able to have a design entered quickly to play around with. Experimentation with a plentiful use of the undo command will likely help you learn the program quicker than any tutorial I could write.

Where to Get Boat Offsets

I used the offsets for the Notus from the Dragonfly Canoe site. (Thanks Dan!) Dan Miller has made W.P. Stephens’ book in which the offset appear available on the Internet at his site. You can spend hours looking at his website. Other sources of offsets include many boat-building books, like Canoecraft and many of the books on this boat-building book list. The Adirondack Museum also has plans available for many old canoe designs, like Rushton’s and Nessmuk’s Wee Lassie. You can also measure boats in The Bark Canoes and Skin Boats of North America by Edwin Adney.

Other Nice Tools to Have

You will need some kind of computer program that is able to create a .txt file. I used Windows Notepad, and a calculator is nice to have. I’ve also developed a spreadsheet to enter the offset in feet-inches-eights and that spreadsheet turns out the required numbers. Feel free to use this spreadsheet.

Entering Offsets

If you’re using the above-mentioned spreadsheet to enter your offsets, you can ignore this section and skip ahead, but it is worth knowing how to enter the offsets by hand to understand the process in case you need to trouble shoot your file.

Free!Ship uses a text file to import boats. So, that is what must be created from our table of offsets.

The first number which will appear in the text file must be a “1” or a “0”. A “1” lets that program know that we are importing Imperial numbers, and a “0” is metric. Because our Notus offsets are Imperial, we’ll enter “1.” Depending on the version of the program you have this may not work right (It has been fixed for the next release.), so after the design is imported to Free!Ship, use the Scale 3D command to change everything by .305 to change meters to feet.

Second, you enter the offsets into the text file. You have to skip a space between the “1” and the first station. Then you have to skip a space between each station you enter. To do this you have to reduce feet-inches-eights to a decimal point. So, divide the eights by eight add the inches divide by 12 to get your decimal and then add the feet. In the text file, you have to enter three columns for each station. These are x, y, and z. X is the location of the station, y is the width from centerline of the point, and z is the height from the baseline. So, the first station of the Notus looks like this:

• Keel * I skipped the keel (but used 0 0 to close the bottom of the canoe.)
• 2″ * 0-6
• 4″ * 1-3
• 6″ * 2
• 8″ * 2-5
• Deck * 3-7

In the text file it ends up looking like this:

• 1 0 0
• 1 .0625 .17
• 1 .1146 .33
• 1 .1667 .5
• 1 .2188 .67
• 1 .3229 1.3021

The 1 0 0 line closes the bottom of the canoe. There must be, at least, one space between x, y, and z numbers.

I should note that for station 0 and 16 I did this:

• 0 0 0
• 0 0 .17
• 0 0 .33
• 0 0 .5
• 0 0 .67
• 0 0 1.5

This closes the bow and stern of the canoe.

Importing into Free!Ship

After you finish with each station, you need to import it into Free!Ship using the Surface command in the File menu. You will be prompted for the number of columns and rows. The key is to use as few as you can to reproduce the shape, because it will be easier to fair your import with less rows and columns. If the shape is complicated then it will require more rows and columns. For the Notus, I used exactly what the program suggested, but I imagine that less could be used. For canoes from Adney’s book, I’ve used 9 and 7, respectively. I’m going to try 7 and 5 to see how it works on the next canoe.

After you import the canoe, use the Scale 3D function in the Edit menu, if you need to do so. After that, you need to set up the design properties, because these are used to calculate design hydrostatics these need to be filled out. Go into the Project Menu and select Project Settings. Fill out the design length, width, and draft. If you know the design draft of a boat use it in the draft. If you don’t know the design draft, a good number to start with is “0.4” for canoes and kayaks. Now, you have the basic hull entered into the program.

Fairing the Boat

Most likely, the canoe will need some fairing. Free!Ship has a nice feature that lets you add a control curve to any edges, and then you can use a funky looking curvature plot to fair the canoe. The manual is a good read on this topic. With the Notus, you’ll probably want to spend a little time using control curves to fair out the sheer line.

The Stems

Because, we imported the stems as a plumb line, we need to shape them. You can easily manually change the stem profiles to visually to match the Notus pictures from Dragonfly Canoe. Just click on one of the points and drag it. I think I got mine pretty close, so you should be able to also.

Adding a Deck

This is where things get interesting, because unlike in all the previous steps, we’re now going to add to the canoe. First, you need to select the sheerline by ctlr clicking one edge, which is the line between two points, on the sheerline. Then you use the extrude command in the Edge Menu this line towards the center. I choose “-1 foot” in the transverse direction. This will give you a deck, but you have to make sure that all the points were on the centerline. Select each point and enter 0 in the “y” box.

You could stop here, but I bet you’re having a good time, so you should select the edges between 4 and 12 foot stations and send them out towards the gunwales, then split, which is found in the Edge menu, a couple of edges around the front and back of the newly formed square cockpit to be able to round the back and front of the cockpit. You should move these points around until they look good.

After the shape of the cockpit looks right, select the cockpit edges and extrude them up and then by hand angle the front few points out to make the coaming angle.

With the cockpit finished, you can use the same technique to make the hatch and hatch cover. This area has given me some slight problems, and I still didn’t get it perfect, but it should work. A trick here is to use the box that you can check in the control point box corner that is marked “corner.”

Adding the Sails

For the masts, you have to add a couple of control points by splitting the edge near each mast and then move these points towards the sheer making sure the “corner” checkbox is unchecked. Then you need to extrude the edges of the mast up the distance specified for each mast.

For the sail, select the back edge of each mast and split it into the right number of points needed to shape the sail. Then extrude these edges and move the control points into the correct positions.

The other thing that I did to get different colors is to assign each part to a different layer. You click the “show interior edge” box and then select the interior edges that you want to become part of a layer, and then you click the “Automatic grouping of selected controlfaces into a new layer” button. Then you can select a color for each layer. It helps to select new layers by turning off those you’ve already created. I used layers this way: hull, deck, cockpit opening, hatch, front mast and sail, rear mast and sail. If I had added a centerboard and rudder, those would have been in separate layers.

Hydrostatics

After you’ve finished your import to your satisfaction, more fun starts. You can check the hydrostatics. Here are the hydrostatics for our Notus:

• Length on waterline: 15.907 [ft]
• Beam on waterline: 2.480 [ft]
• Displaced volume: 9.335 [ft3]
• Displacement: 0.267 [tons]
• Longitudinal center of bouyancy: 8.617 [ft]
• Vertical center of bouyancy: 0.298 [ft]
• Block coeff. based on mainparticulars: 0.4667
• Block coeff. based on wl. properties: 0.4732
• Prismatic coeff. based on mainparticulars: 0.5993
• Prismatic coeff. based on wl. properties: 0.6028
• Wetted surface area: 32.761 [ft2]

Using these numbers we can calculate resistance using the KAPER Drag prediction spreadsheet, which was designed by John Winters. If you buy his ebook, The Shape of the Canoe, which you should own anyway, the spreadsheet is included. I think it would be great if everyone that imports a canoe into the program would do KAPER calculations, so we could compare canoes. If you’re interested, let me know. In the future, as FREE!Ship is updated, more data will be available for comparisons.

KAPER
• 2 knots 1.40
• 3 knots 2.91
• 4 knots 5.72
• 4.5 knots 7.81
• 5 knots 10.31
• 6 knots 17.56

Even More Fun, Adding Stations and Waterlines

Most everyone enjoys seeing stations and waterlines on the boat that they’ve been working on, and this program does not disappoint. It lets you specify stations and waterlines at intervals or where ever you want one. Choose Intersections from the Calculations Menu and then right click on the box it pulls up. Make sure that the checkmark is on Stations and then select range. For an exercise specify 1.0 intervals. Add buttocks, waterlines, and diagonals as you please. Three or so of each give a good sampling. When you’re finsihed, select Linesplan from the Project Menu. The shading is nice, but you can turn it off to get a better view. Here’s another Linesplan showing the Modern Malecite 2.5 Fathom St. John River Canoe on page 79 of Adney’s The Bark Canoes and Skin boats of North America.

Conclusion

Hopefully, this helps. If something doesn’t make sense, let me know, and I’ll try to explain it better. A lot I did was trial and error during this learning experience. It took me about four hours for this one canoe, but now that I’ve learned it, it took around an hour plus fairing. With the spreadsheet I created I might when go faster than that. Not a bad way to spend a spare hour, I think. So, find some offsets and plug away.

The Following Files Are Zipped

• Notus with Sails
• Notus without Sails
• Offset Entering Spreadsheet
• Notus Text File
• Malecite Canoe
• Malecite Canoe Text File

Notus Zip Files

The files in the zip folder are:

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.