Where do rebuilt stems break?

[Tim Belcher]

I'm working on a 1913 OT Charles River CS and have cut new pieces for the tops of the stems that are now expoxied in place with no other fastener. I've seen a number of techniques for securing the stems to the inwales and deck, and also reinforcing the connection between the old and new stem components. In weighing all the different approaches, it occurs to me that I don't really know what I'm protecting against. Here are my questions:

1. When stem repairs break in use, where or how do they normally break? Am I correct to assume that the weak point is the connection between the old and new pieces of the stem, rather than the connection to the inwales and deck?

2. If I try to reinforce the connection between the new and old stems with a screw from the back of the new piece going into the back of the old, won't I be weakening the old stem by removing more wood?

 

[Rob Stevens]

Great question, Tim.
I think most stem repairs are to replace rotted wood, not broken stems.
Once a stem is in place, it will be mutually connected and supported by the planking, deck, inwales and sometime a stemband. That should be sufficiently strong to prevent it from breaking from an impact from the front.

Has anyone broken as stem while paddling, presumably from a hard impact?

Rob

 

[Michael Grace]

Hi Tim,

I've never broken a stem whether original or spliced during restoration. In repairing your stem, you're not so much protecting against anything as you are simply rebuilding the structure of the canoe. The stems (inside stems) are places for planking to land and be attached, and for attaching the canvas. As Rob said, once you've completed the job, you've got a variety of things all coming together at the stem, and they all work together to provide structural integrity to the canoe. To answer your specific questions:

1. They don't normally break. A good glue joint is usually stronger than the wood itself when wood is joined edge grain to edge grain. End grain glue joints are weaker but again you've got a vatiety of structural components all working together to provide structural strength there at the canoe's ends.

2. Yes installing screws means a little less wood, but is it enough to make a difference, to lead to failure? You can solve this potential problem and increase
the strength of the junction by using Rollin Thurlow's method of adding a supporting backer as shown here:

http://forums.wcha.org/index.php?threads/stem-repair.16778/

Hope this helps,
Michael

 

[Tim Belcher]

Thank you both. Makes sense.

 

[Dave Osborn]

I epoxy a strip to the inside of the stem. It is the width of the inside of the stem, goes beyond the old/new joint by a couple of inches both ways. Thickness is 3/32” or a little less.