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PostPosted: September 27th, 2007, 1:38 am 
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Joined: July 9th, 2003, 11:48 am
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Location: Back to Winnipeg
Hello builder-types,

I've seen threads and other resources about how to install wood gunwales, what types of wood to use, and whether to varnish them or what to oil them with, and how to spell "gunnel", but I've got a question about repairing a rotten section...

Around one screw hole about mid-boat, one outwale completely rotted, then cracked, and has now crumbled (at a spot where my tarp leaked a drip all winter, or 2 :oops: ). Seems like something I could repair (the gunwale that is, but the trap too!), rather than replacing all the gunwales.

My plan is to:
1. Buy a small piece of hardwood at Home Depot, or wherever, and shape it like the gunwale (NovaCraft uses white ash for gunwales). The screws might be 8" apart; so, including some overlap to the next screws, I might need a 2' section to work with. Maybe 6" are affected by the rot, and I could use less, but I might as well go out to the next screws instead of adding new screw spots.
2. Oil up the new gunwale piece pre-installation?
3. Cut out the section of bad gunwale to near the next screws, leaving several inches to taper some overlap beyond those next 2 screws.
4. Fit, glue/epoxy and clamp the new piece in, then drill and re-screw the 3 screws.

Sound reasonable?

Questions:

Should I oil the new wood before I install it? Seems sensible, but I assume would affect any glueing. I guess I'll only the non-glueing surfaces.

For fitting/overlapping the new section with the old - does it matter if the new wood goes over or under the old; or should it alternate, and if so, is there any rhyme or reason for deciding that?
p.s. Just learned in another thread that this might be called "scarfing"?

Will a repair hold? It seems much easier/cheaper than totally replacing gunwales, even if it only buys a few years, and I don't care too much about how a patch job looks.

Thanks, hopefully these are simple questions (and a simple job). I'm OK with repairing ww Royalex cracks and gouges etc, but the wood stuff is all new to me.

Cheers, PY.

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PostPosted: September 27th, 2007, 7:03 am 
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Joined: August 27th, 2002, 7:00 pm
Posts: 2560
Location: Geraldton, Ontario Can
Hmmmm...I'm assuming you have already removed the gunwale in question? What you are proposing to do is actually probably more difficult than just replacing the gunwale. To do it properly, you will indeed have to scarf the new piece and the ends of your old pieces. Scarf reccomendations are about five inches on the diagonal to one inch thickness, so probably about a four inch scarf would suffice. You will also have to do some ticky-boo measurements to figure out all four scarfs to get you gunwale to be the same length as previous. If you use a good expoxy, the scarf joints will be very strong. i use them for all my gunwales.

However, since you will have to take the old one off anyway, if it were me, I would replace the whole thing. If you can't get a strip or two of hardwood somewhere, places like Noah's in Toronto sell pre-made gunwales, and they are not that expensive...think they were something like 25 bucks each.

Have fun!

Oh ya, don't oil the peice before you glue it!


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PostPosted: September 27th, 2007, 7:50 am 
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Joined: June 13th, 2007, 1:31 pm
Posts: 1102
Yarnelboat

I would propose not removing the entire gunwale, but just removing
the deteriorated section, plus a few inches either way with a simple
perpendicular cut... then use a Router to cut a mortise channel in the
middle 1/3 of either end of the still attached gunwale.

Buy your ashpiece and cut-to-length the exact measurement from the
depth of each mortise channel.

Then go to the table saw, raise/lock the blade the 1/3 measurement,
and continuously run your stock thru the blade to remove the excess 1/3.
Reverse your stock, and repeat the process to the other side , creating a
Tenon.

Rotate the stock end-for-end and repeat the process for the opposite
tenon... taking care to not exceed the shoulder-to-shoulder measurement
on the still-attached gunnel... otherwise, you'll leave water penetration
points once reattached.

You may oil the replacement piece ahead of time, if you are carefull not
to oil the tenons... otherwise gluebond will not be secure.

Tap the manufactured joint into place for fit... to check... remove, and glue
both tenons all 4 sides and both mortises and 3 sides. Tap piece into
place.

Drill small pilot holes thru each mortise and tenon joint, and screw it off
with brass or stainless wood screws. Clamp til glue lays up... a day.

Remove clamps... sand or scrape excess glue... re-oil...
and you're good to go.

Sundown


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PostPosted: September 27th, 2007, 7:09 pm 
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Joined: July 9th, 2003, 11:48 am
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Location: Back to Winnipeg
Thanks for the comments.

I haven't removed anything, but the rotted section has started to remove itself.

I was only planning to remove the 3 screws, as per Sundown's thinking.

I was thinking of a 4" "scarf" (diagonal overlap) as RH mentioned. Does it matter which ends of which pieces overlap to the outside or inside?

If I can find good wood that cheap, I probably will replace the whole gunwales.

Thanks, Pat.

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Learning to paddle is like learning a language:
It's easy to learn the basics, but will you be understood in a strong wind?


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PostPosted: September 27th, 2007, 8:53 pm 
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Joined: August 27th, 2002, 7:00 pm
Posts: 2560
Location: Geraldton, Ontario Can
I don't think it will really matter which way you have y our scarf, although if you are not taking the gunwale off, it would probably be easier to leave the length of the backside of scarf laying along the canoe. At most comercial lumber places, White ash usually runs anywhere from 3.50 to 5 bucks a board foot. A three inch wide by 8 1/2 feet long piece should cost you under 15 bucks. Find a friend to rip it to desired width on a table saw...if they have a router table, round off the edges, or just use a small block plane or spokeshave to round off the outside edges, then sand it all down, and oil it up. Are the screws holding the outwale on drilled from the inwale side or from the outwale side? If from the inwale, re-attachment is just a matter of clamping on the outwale, pre-drilling through the existing holes and then putting your screws in. I just use regular wood screws now, they've been fine, my wood-butchery style of carpentry usually twists the heads off the brass ones.


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