Making pattern for outside stems

[smallboatshop]

Once again I'm having a problem making a pattern for new outside stems. Usually the cardboard pattern, once cut out doesn't fit the curve, so i do it over and over until the shop floor is covered with cardboard and the air is full of curses.

There must be a better way. What do others do?

Dan

 

[crosscuts]

Using 1/8" plywood door skin plywood and the round top of a 36" sander (or any round sand drum or wheel) it is easy to sand off a bit here and there until the pattern fits. There might still be a lot of cursing but only a little sawdust on the floor.

R.C.

 

[Todd Bradshaw]

When Norm Sims and I used to take the lines off of canoes we used a frame secured next to the hull and stapled a bunch of "pointers" to it, touching the hull. Once done, you drop it on a sheet of paper and draw a dot at the end of each point. Connect the dots with a flexible batten, fair the curve a bit if needed and you have an accurate cross section or stem profile.

Here is a section taken from one of my kayaks to build a padded cradle showing the frame and pointers. The second photo shows the lines for Norm's old Morris and you can see the dots on the sections.

 

[Dan Miller]

I've bent outside stems directly on the canoe. Might not have been the best idea, but it worked.

 

[Dave Osborn]

I've done as Dan suggests with good success. Steam the stock with a steel backer strap attached. The strap has holes in it to be able to pre drill and drive construction screws in it as the bend takes place. It's a 2 man job. Once the wood has cooled down, the backer is removed and stem re fastened to the inner stem.
Have had an occasional failure with stock that wants to twist, but all in all a time saver if you don't have a form tweeked to your particular stem profile. I do it early in the restoration process on the bare stem.... It gets left on the hull for the entire time until you are ready for canvas. Sanding and varnishing are done as it is mounted to the canoe.

 

[smallboatshop]

Thank you all for your advice. I combined some of the suggestions. These outside stems are for a war canoe so they are large.
I held the cardboard against the canoe and Lindy drew the outline, then we stapled the cardboard to a piece of 3/4" plywood. Hole were punched with an ice pick every 3 or 4 inches along the pencil line, the cardboard removed and nails tapped into the holes. Then, as Todd had done, I bent a batten around the nails and drew a line on the plywood following the fir curve that the batten made.
The form was made, the stock steamed and bent and those outside stems fit as well as they might!

Thanks, Dan