View Full Version : Finger Joints vs. Scarf on Strip Planked Canoes?
01-13-2003, 10:22 AM
Anybody here have an opinion (I know, it's a silly question...if there wasn't an opinion on this I'd be scared, very scared) regarding the use of router-made finger joints as opposed to traditional scarfs when building a stripper canoe?
B. Darrah Thomas
01-13-2003, 11:04 AM
Planking?... Full length
01-13-2003, 11:17 AM
Planking is where I'm thinking of doing the finger joints.
Inwales and other elements would be scarfed for appearance. For discussion, what would be the drawback of a finger joint?
01-13-2003, 11:57 AM
If it is standard cedar strip/sheathed construction, there is no need to to either. You can join the strips in work, via simple butt splice at a mold section (staggering the joints as you go along). This will be strong enough throughout the stripping and fairing processing and plenty strong after sheathing inside and out. Finger joints would be nice if you have the patience and time; cedar strips this small are mighty delicate. Proper scarphs are definitely strong, but then plain ole butt splicing is plenty strong for this type of small boat construction, as the joint is reenforced by the surrounding strips as well as the complete sheathing it receives.
Gunnels and sheer clamps - scarphs - 8 to 1 minimum.
I am building a Redbird right now. I was able to find 20' long clear stock, so therefore didn't have any scarfs, but i did have one crack in the process. I used a butt joint, as per the instructions in Canoecraft, and it turned out great. Bead and cove held it together nicely. Also, I used the stapleless construction method.
01-13-2003, 12:36 PM
01-13-2003, 01:02 PM
As long as you pick your spots carefully, avoiding areas that have a lot of twist or edge set, butting them on the forms like Dee said is the way to go. Both finger and scarph-jointed strips have a tendency to look rather irregular when the hull is faired-out and call attention to themselves. Butts show too, but usually look cleaner and don't call as much attention to the joints. It's kosher to use any means required to hold things in alignment until the glue dries, from tape to clothspins, clamps, hot-melt glue, inner tubing or what have you.
Strength is not a problem. I've built boats where nearly every strip was more than one piece and some that had pretty wide feature strips made mostly from butt joints.
01-14-2003, 12:45 PM
I'm sure some wood technonogist can cite chapter-n-verse on how bullet proof finger joints are supposed to be, but in my experience they are weaker than the wood, tend to break there, and show rather badly. How that applys to stripping a canoe, I couldn't guess.
01-15-2003, 07:14 PM
What a resource!
I knew that I'd get what it needed from this group. Everybody has such valid arguments for and against this process.
Here's where my thinking comes from:
First, I believe that the structural integrity of the finger joint/scarf/butt joint becomes pretty academic after the skins are applied to the structure. All that you really need is something to hold the skins apart (strips of wood) and how they are made into long enough strips is a matter of tools, time and skill.
But, my big concern is in piecing together clear strips to run through the router for the bead 'n cove edge treatment. I'm afraid that a butt joint simply will not stand up to the handling and doing all those scarfs by hand will take an inordinate amount of time. I'm no plane pilot so I'll probably have inconsistent results too.
My logic was that I already have a router and router table. Once the wood was ripped and chopped to provde clear strips, it wouldn't be that big a deal to set up and finger joint the pieces into the longer strips that I need for the canoes. Glueing should be a little easier too because of the 'self-aliging'nature of the finger joint cut
MLCS offers a finger joint router bit (http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_windo.html) thats only $55.00. It should do the job, shouldn't it?
[ 01-15-2003, 08:16 PM: Message edited by: RCL ]
01-15-2003, 08:10 PM
In case you haven't played much with strips yet, they are pretty slight, bordering on floppy until you get them on the forms. It is probably going to be easier to handle them while doing the bead and cove thing before they are spliced into longer, more unwieldly pieces. It seems kind of silly to invest $55 in a bit that makes ugly joints and spend a lot of time pre-splicing on the bench when it's so simple just to do it on the forms as you build the boat. There will be plenty of steps in the building process that are a bit tricky the first time you try them, but splicing strips usually isn't one of them.
01-17-2003, 10:04 AM
I too think that going beyond the butt-joint is not making the best use of your time. My next stripper will be made with much shorter (cheaper) boards. Every run will have a butt joint. They just don't matter, and you can't see them easily anyway.
And most of the strength of this boat comes from the fiberglass/epoxy, and the hull's roundish shapes. The cedar is as much a spacer as anything, there to give a shape and to hold the 2 layers of cloth apart.
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