A little how-to with Sketchup

Hiya folks.

First off, I do plan on cutting some more wood today, but I thought a little post about how I use Sketchup to help visualize things might help out some of you who aren't familiar with it.

Sketchup is a 3D surface modelling program distributed for free by Google. "Surface modelling" just means that the things you make in it are composed of surfaces, and aren't actually solid models... .but this is not really important for what I'm going to show you today.

I'm using a cut-out plan for the Pathfinder pieces that I found on the JWBuilders forum. It shows a plan for cutting out all the frames economically, using the minimum amount of plywood. What it doesn't show is all of the dimensions... you have to pull those from the plans. As anyone who's worked on a Pathfinder has seen, several of the middle frames are formed of one large, wide piece that spans the width of the boat, and two smaller pieces that attach to it and go up the sides. When you're cutting the wide pieces out, the line forming the top of the frame member is not dimensioned. You could, of course, use a scale ruler to try to get that dimension right, or transfer the angle from the plans using a bevel. I, instead, use Sketchup.

When you start the latest version of Sketchup, it will ask you for a template to use... I use the Woodworking template in millimeters, since John's plans are metric.

Start off by forming two lines in Sketchup using the TapeMeasure tool (shortcut T). These lines should be perpinducular, with one forming the centerline of the boat, and the other representing the waterline.

Next, again using the TapeMeasure, draw lines up and down from the intersection, using the dimensions John gives you for the length. How do you enter dimensions? Well, here's the sequence:
1. Choose the TapeMeasure tool (either clicking on the icon, or hitting T on your keyboard)
2. Move your mouse down from the intersection. It will drag a green arrow with it.
3. Without clicking anything, type 150. You'll see this show up in the "Measurements" box in the lower right hand corner. Now hit "Enter"
4. Poof! You just created a little measurement line exactly 150 mm long. This is the bottom measurement for frame 3 on the Pathfinder.
5. Repeat the above, pulling lines down 80mm, and up 48, 210, and 453.

6. Now, starting at the little crosshair designating the point 150, click again and drag to the right (it will drag a red arrow). Type in 402, hit Enter. The point at the end of this line is the corner of the bottom stringer shown on the plans. Repeat with appropriate dimensions for the above measurements.
7. After finishing the above, choose the Line tool (L), click on the bottom center point, then the point to the right, and up around the curve of the hull. This will create solid lines connecting these points, and you now have the shape of frame 3, dimensionally accurate, drawn in Sketchup!
8. To check on the dimension of the top of the frame, use the T tool again to measure up from the intersection of the waterline and centerline, this time to 57mm (a dimension helpfully provided on the plans). Now use the T tool to measure to the right from that point, straight over to the diagonal line. The line you're dragging might try to pop to an intersection... if it does, then hold down the Shift key while the line is still red. This will force it to follow that angle, and not shift around. When you drag the end of the measuring line over the diaganol, it will show you that that dimension is precisely 816.9mm. (it won't look exactly like the picture, but you'll see it.) Edited to add: I screwed up in the image... the dimension is actually 816.9, not 817.9. Durrr.)

You can also use Sketchup to check the dimensions on some of the curves. For example, this is what I found on the top of the Transom. You'll see a circled area where the curve doesn't cross the little crosshair. At this point, John had given an offset of 178mm, but I found that it was actually 171mm to produce a fair curve. I did this by drawing in all the points similar to how I did for frame 3 above, then drawing an arc (A on the keyboard) from the endpoint to the middle, making sure that the arc landed on one of the offset points. All of the offsets John gave landed almost exactly on the line except for this one. I then measured from the starting point down to the intersection of the dashed line and the arc, and it came up as 171.1mm.(You can also click on "Window > Entity Info" in the menu bar, and it will open a little window showing information about the entity you've clicked on. Clicking on the arc will tell you that its radius is precisely 1495.4mm.)


I know this probably sounds like a lot of work, but Sketchup is a remarkably user-friendly program, it's free, and checking your dimensions in this way helps (me, at least) to visualize what I'm about to do before I apply pencil (or saw!) to expensive plywood.

Hope this helps someone out. :)

Jason

Oh yes, I forgot to mention: There are all sorts of free Sketchup lessons online, from step-by-step guides like the above, to videos on YouTube, to people who have posted animated Sketchup files you can download and watch right in the program. Try:
http://www.sketchucation.com/
http://www.aidanchopra.com/ (This is a page from the author of Sketchup For Dummies... it has videos showing you things from the book.)

First pieces cut!

So, I had some time to kill this weekend, so... first pieces cut.

And, since I just couldn't wait to see how big it was going to be...



Drawing out the pieces wasn't that big of a deal for me... I've taken a manual drafting class, and this is just like that, only on plywood. What did help is that I had Google Sketchup open on my computer in the next room. I could quickly draw the piece out in Sketchup to make sure all the points on the curves fit, and then nudge them around until they do. It's also nice to draw a smooth curve that fits the points in Sketchup, then measure the arc to find the radius. After that, it's usually easy to draw with a 4' ruler converted to compass duty. Sorry for the short post, but sleep is beckoning.

About me, and about Pathfinder

So who am I, and what am I doing?

My name is Jason Folkers. I'm originally from Florida, but have been living in the Canadian prairies near Calgary since 2003. I caught the sailing and cruising bug from some of my friends back and Florida, and now have dreams of sailing over blue water to a distant island paradise.

Don't we all?

The reality, though, is that boats that can make journeys like that are relatively pricey, and living in the middle of the prairies doesn't lend itself well to learning blue-water sailing skills. As a result, I started looking around for something a little smaller that I could use on local lakes. At the same time, though, I wanted a boat that I could potentially tow out to the British Columbia coast and sail around the islands.

In my search I came across quite a few smaller boats that would do this, but my eye was caught by a design for an open wooden cruising dinghy by Kiwi designer John Welsford. The Pathfinder was designed to be a slightly larger version of his very successful Navigator design. At 17' long, it's short enough to build in my garage, yet long enough to spend significant time on should I have a few weeks off to sail in BC. It has a relatively low-tech, low-stress rig, great load-bearing capacity, and can handle pretty serious weather. It also only weighs about 600 pounds, so I should be able to tow it behind a normal car, with a simple trailer. Building the boat myself allows me to spread the cost out over the build time, and gives me something to tinker with and improve my woodworking skills.

So, that's the intro. Where am I on the build progress? Well, just yesterday I picked up my plywood that I had ordered in from Westwind Hardwood in BC. They carry the Hydrotek brand of Meranti plywood. This plywood is supposedly lighter and more abrasion resistant than the Okoume ply I could get locally, and was significantly less expensive, even including the $300 shipping from BC to Calgary. The sheets were packaged well and arrived swiftly... I wouldn't hesitate to order from Westwind again.

Next steps are to loft the frames from the drawings onto the plywood, and start cutting them out! I also need to order silicon-bronze screws and assorted hardware, order in a few more tools, and get my first load of epoxy. Pics will come as soon as I start doing anything worth seeing. :)