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I know this has been discussed already (spent a while last night reading through search results), but I am still undecided about how to work around the issue.
I'm planning to build the Huron Cruiser, which is listed with a length of 15'9" in the book. I was planning to build the strongback as described in CanoeCraft as well (16' long).
I know CanoeCraft (and other posts here) suggest adding a few inches to the molds. I have a few quick questions about this that I didn't see the answer to anywhere:
In Canoecraft revised edition, on page 92, there is a full page picture of the redbird molds on the stongback. The stem is on and the top of it comes right down to touch the strongback surface. Am I missing something or is this actually what we are trying to avoid by adding a few inches to molds?
If I were to add 2" to mold heights, I picture just drawing a new 'baseline' on my plywood, 2" above the factory edge, and referencing the plan's baseline to that drawn line when tracing the mold onto it. Then I'd just add vertical lines from the factory edge to appropriate points on the 'raised' baseline to define the added sections on the plywood. Having said this, I'm wary of introducing error (ie drawn baseline not perfectly square, etc). Is there a better way, or is it just a matter of being as accurate as possible?
If I am to do the above adjustments, is the same done for the stem molds? (ie nothing special done about the curve that normally comes right down to strongback surface height?)
To avoid issues with introducing error as described above, I thought maybe I would just make a shorter strongback and stick to using standard height molds and factory edge of plywood as baseline. However, I'd like to re-use the strongback later for a slightly longer canoe (i.e. maybe Prospector). Are there general rules for how much shorter a strongback can be? For example, how bad is it to create a strongback 15' long, and have multiple inches of of the stem molds hanging over the ends?
Lastly, how do I relate the stated length of the canoe to the length from stem-top to stem-top. For example, I think the Redbird is reported as some 17+ feet long, but the distance between the tops of the stems is quite a bit shorter. I'm not sure how to easily get that stem-to-stem distance, which is what seems to matter when figuring out a proper strongback length.
Your stem molds can extend beyond your strongback several inches (i.e., it's just fine to build a shorter strongback. You will find it actually handy to have the stems hang out beyond the strongback...
Last edited by Patricks Dad on Mon Jul 14, 2014 8:50 pm, edited 1 time in total.
I don't think so. You can probably make a reasonable guess by looking at the scale drawings.
I don't see why you would ever need to know with a lot of precision...
Ok, thanks. I suspect I'm just over-thinking this. I basically wanted to make sure I wasn't going to end up with too much stem mold overhang (making it flimsy?) or too little, making it hard to work on the stems.
I don't know if you've already solved this problem but if not, here's how I did it. I cut the molds exactly as the dimensions stated in Canoecraft. Then I made up riser blocks that elevated each mold 2". The canoe fits on the strongback with just enough room to work the ends of the stems.
I knew at the start that I'd probably want to reuse the strongback for making another canoe, so I didn't want to shorten it. If I build a redbird or a nomad, or an 18' kayak then I don't want to have to make new strongback parts.
That seems like a good method, Phantom. I'm also planning to build at least slightly larger canoes later, so I would like to keep my strong back from getting too short.
EDIT: Removing question about how you made your risers....I read your project blog and saw them there. Very good idea!
For anyone curious, the risers were made from 2x4 blocks instead of 2x2, and he cut a dado through the centre of the block to seat the mold. One very clever trick used was to continue the dado (albeit a more shallow cut) around the side of the block to make a reference representing where to align the block with the station lines on the strongback.
I think I will do something very similar to solve my issue, although I might just use a rabbet to seat the mold into my block on one side. In theory that way I could still just align the side of the block to the station line...
