Lofting the Palm Beach 22

Mack Brown helps with lofting the lines of the Palm Beach 22
Mack Brown helps with lofting the lines of the Palm Beach 22.  Look closely and you can see the curves of the boat!

So, we’ve decided on boat plans and purchased them.  We’ve detailed the lumber we’ll need and ordered it.  Now it’s time to draw the boat’s lines full scale.  That means we’ll end up with a 22 foot long drawing of the boat, since the boat will in fact be 22 feet long.  As a friend of mine in the construction industry used to say, we’re going to draw it at a scale of 12 inches to the foot.  The process is called lofting, because the only place big enough to do this in boat shops of old was the sail loft.

Building a lofting platform out of 2x6 framing and plywood.
Building a lofting platform out of 2×6 framing and plywood.

To do that, we need a flat plane large enough.  Now a concrete slab shop floor is notoriously not flat.  It has all sorts of dips and hills.  Just spray a little water on it, and look at all the puddles if you don’t think so.   At any rate, I built a platform of with 2×6 framing that I milled to straight edges so that when I fastened the frame together and shimmed the low spots, I had a reasonably flat surface to work on.



Lines drawing consists of the Profile View (top), Body Plan (middle) and the Half Breadth View (bottom) along with the Table of Offsets (very bottom)
Lines drawing consists of the Profile View (top), Body Plan (middle) and the Half Breadth View (bottom) along with the Table of Offsets (very bottom)

Now the fun begins.  Here you see the lines drawing I mentioned in the first paragraph.  Our job is to “blow this up” to full size.  You do that by first laying out an accurate grid that matches the one the designer gave you in his drawing.  This brings up all kinds of questions that come up all the time in building a boat.  For instance, how accurate does it have to be?  Well, the more accurate the better, but for my purposes, I want my grid to be accurate to within 1/32 of an inch.  Also, how do you get a dead-on perpendicular?  I mean exactly 90 degrees to your baseline?  It’s easy in a CAD program.  You just tell the program to do it for you.  But how do you do it in the real world?  Answer: strike a couple of arcs off the baseline with a beam compass.  Google it.  You can’t get any more accurate than this.

Once you have the grid laid out, it’s time to start laying down the curves of the boat.  Again, our designer, Mr. Nelson Zimmer, gave us a table of offsets, telling us at what point each of the lines of the boat intersect the grid.  You just measure and tick them off on the grid.  Then connect them with a batten held to the curve, and draw it in pencil.  Take a look back at the top picture in this post.  There you see my friend Mack, and if you look really closely, you can see the straight grid lines as well as the curved lines of the boat.

There’s a fair amount of detail I’ve skipped here for expedience.  And I realize most people find the details somewhat tedious.  But, when you have the profile view and the half breadth view laid out full scale on your lofting board, you have an incredibly useful resource.  You can use the two views to construct the body plan drawing (the one in the middle of the paper plan shown above) that describes the exact shape of any cross sectional view of the boat.  Think of that!  You know exactly what shape an internal bulkhead needs to fit in your boat.  Just cut it out and put it in.  If you did a good job lofting, it’ll fit first time, every time.  Also, we’ll use the curve of the keel line when we’re building the keel.  Stay tuned for that.

As always, I’m excited to hear your comments and questions.  Feel free to post them here, or stop by and chat!

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