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I am in the process of transfering the plans to the MDF mold material for my 16' Prospector. I see the sheer line is clearly marked as the bottom of the mushroom head. I notice most of the forms posted have the molds actually lower (higher if the boat wasn't upside down). Ed made a nice post in the builder's tips section showing how he put a removable extention on his molds. He also has some great pictures of his build. I will probably try this method myself.
My question is: Why? Is there an advantage to having the mold be a little bigger and marking the sheer line rather than having the mold cut right at the sheer line?
You guys said there were no stupid questions. Hopefully I won't test that theory too hard!!!!
Andy, It's nice to be able to hold the first strip proud of the shear line so that when it comes time to actually cut the shear line, a little of that first strip can be trimmed. I like to hold my first strip about 1/4" proud of the shear line at mold zero.
In order to do this, I add an extra inch to the mold and make it removable. This give some support to that first strip. Then when the time comes to cut the shear, remove the added mold extensions and then layout the shear line with a piece of cardboard with a 5/16" slot cut on one end. The cardboard is a kind of story stick to transpose the mold shear by straddling the template over the hull strip edge. Mark the shear and then use your favorite method to draw a fair shear line from mold zero out to the stems. I use a 3/8" strip ripped from a full strip, about 1/2" the length of the hull.
Andy, this doesn't have to be done this way. a lot of fine canoes have been made without this elaborate scheme. I just like to do it this way.
Ed...
PS: Another reason why I like this method is because I don't use staples but use clamps to hold the first and succeding strips. The 1" extensions provide the extra support for my clamps.
Andy, I would very much echo Ed's last comment in his previous post. Adding an inch or two below the sheer line will make it much easier to mount the brackets and clamps if you go stapleless. I had an inch extra on mine and I really wished I had a bit more room.
Adam
Who travels not by water knows not the fear of God --- 17th Century Sailor
This will become especially apparent when you start filling in the sheer of the cnaoe at each end. You will want some "extra" at those stations. The middle of the canoe you can get by without it, but if you have a choice from the start, then leave a couple inches below your drawn sheer line.
Thanks guys. I'll leave a few inches. I just finished transferring the plans to the MDF mold material. I won't get to cut them out until next week. Thanks for the great advice!
You should make a shallow saw cut at all the sheerline marks to be able to locate it later. It would also help if all molds extend beyond the sheerline by the same amount, make it consistent. If you add 1" then you will just have to measure up 1" from the edge of all molds to determine the sheerline.
