Lofting transom camber

[gashmore]

I am at a lost on this one. The top of my transom is 11' wide and has a verticle camber of 4 1/2" and a horizontal camber of 3 1/2". That part I have down. The problem is that the transom slopes downward at about a 40 degree angle. How do you establish the camber on the angled surface?

[Ian McColgin]

To spell his name phonetically , Vatsey's book (check WBbookstore) has the only explanation I could understand.

[Ross Faneuf]

It's Alan Vaitses book on lofting. He covers this as well as humanly possible, but it IS a challenge.

[Mitchel Larsen]

This might seem from left field but there are a couple of stairbuilding and handrailing books from the turn of the century that might help.
The geometry is the same but the terminology is closer to home. You would find in these books a mimi tutorial on three dimensional geometry- cones, cylinders, prismatic solids etc.
George Ellis and a fellow by the name of Mowat.
Both books are from Linden publishing. Vaitses is great, as are other boaty sources but it helps to get different perspective sometimes.
Mitch

[Will]

Gashmore, I've got the books mentioned and have e-mailed you on the subject.
Bill Perkins

[gashmore]

I've got Vaites' book but quite frankly, chapter 9 scaired the heck out of me.<g>

Someone e-mailed me a suggestion that the camber of the raked transom would be the hypotenuse of a triangle whose other two sides are the verticle and horizontal cambers of the top edge. It took a while for me to visualize this but I believe that might work. If a vertical arch of the desired camber is rotated to the desired angle, it will be described by two cambers, one vertical and the other horizontal. Which I have. So I think it makes sense.

[Dale Harvey]

Yeah, the lofting is a bear, but just wait until you start cuttin the sucker out! A fair compound transom is the mark of a distinguished builder. Very, very, few amatures get it right the first time. Geometry is fine stuff, but this takes Zen.

[Wilson Fitt]

I lofted and built the transom on my boat without too much grief. It is about 7 ft wide at the deck, has a 10 ft radius and is raked 45 degrees or so. Didn't worry about the camber on the top until all the deckbeams were in, just let it run tall then marked it by extending the run of the deck aft to the inner face of the transom with a stiff batten. A lot of this stuff is hard to describe or visualize on paper but quite straightforward when it sits before you in three dimensions.

[Ross Faneuf]

I second Wilson. I agonized over lofting Ceol Mor's transom despite it having an easy-to-loft shape (it's vertical). This was important for cutting the transom to shape everywhere but the top. It turned out that the final shape of the top of the transom had to come at the very end, to integrate it visually with the rest of the boat anyway. Loft enough to make sure you have extra stock to saw away, and finish it in the boat. I had to do a lot of fudging to get it right, since I didn't come up with final ideas for rail trim until the last minute, and the transom has to match those.

[gashmore]

I believe that is what I will have to do. The only problem is, I am a not-so-pure-wooden-boatbuilder. The transom is cored with foam and the perimeter of the core is laminated mahogany. Guess I will just have to guestimate the curve and make the top rail extra thick so I have enough solid material to plane it to look right.

[Ross Faneuf]

OK, confession time. I made the mistake of cutting Ceol Mor's transom to what I thought would be a good line. Catch is, this was before I did the covering board and toe rail. Result: transom now too short by the thickness of the covering board. I had to laminate up a filler piece and glue it to the transom with a spline. Fortunately, since Ceol Mor also has a decorative sheer strake, the continuation of that covers this error.

The final trim for Ceol Mor includes bright-finished mahogany strake matching the sheer strake, and top molding matching the covering board. I had to laminate both of this in place, remove for shaping and molding, then glue in and clean up. It was probably the most conceptually challenging job I had.

I don't have any handy photos online here, but you can see this in a website article that was done about Ceol Mor's launch:

http://camden.k2bh.com/Opinions/GuestCols.cfm?StoryID=752