Advice on removing outwales?

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Mattcliff
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Joined: Mon Jun 25, 2007 3:26 pm

Advice on removing outwales?

Post by Mattcliff »

Hi:

I built my first canoe, a Prospector, this year -- thanks to all the help from this site -- and the good news is that it paddles beautifully. Looks pretty good, too -- I scarfed together cedar strips from lumber I high-graded from a local lumberyard, then painted the outside. Nice look.

Now the bad news. For reasons I won't bore you with, the scarf joints failed on my ash outwales with the first hard use. I'm machining a replacement set, but I'm going to have to figure out how to get the "old" ones off without trashing the boat. Of course, when installing the old ones, I didn't mess around -- they're epoxied on, with screws every 8" or so, and the screw heads plugged with dowels.

Any advice on removing these? The best I can come up with is carefully sawing them down to the hull level on either side of the screws, then going after the resulting 8" sections with a (gulp!) chisel, then maybe cleaning up what's (hopefully) left with a plane I don't care about too much. Sounds like a mess.

Any better ideas?

Thanks,

Matt
Missoula, Montana
jimmar57
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Post by jimmar57 »

You've got me a little worried. I've only buit one canoe which has scarfed outwales also, Cherry....I'm not even close to being an expert, but....couldn't you just re-glue, clamp and screw the joints together and then plug, without removing the whole outwhale?
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Davesbuild
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Post by Davesbuild »

Matt,

Try an angle grinder with a sanding "flap-disc" on it. I use one quite extensively. You can eat away the outer gunnel in no time with a high speed angle grinder. Don't even worry about the screws, the angle grinder with the sanding flap-disc will eat them away also...

Be careful, the disc will also eat your hull, pants, skin, fingers and any small dogs that happen to wander near it.

Hope this helps.

Good Luck,
Davesbuild.
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Bryan Hansel
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Post by Bryan Hansel »

Could try heating the epoxy until it gives...

...this is exactly why I don't like glued on gunwales. Replacement is near impossible. With screws, you don't need to worry about that.
canoeblderinmt
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Post by canoeblderinmt »

Besides, Bryan, it saves a couple of ounces, right? :laughing
" Choose to chance the rapids, Dare to dance the tide..."
Mattcliff
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Joined: Mon Jun 25, 2007 3:26 pm

Post by Mattcliff »

jimmar57 wrote:You've got me a little worried. I've only buit one canoe which has scarfed outwales also, Cherry....I'm not even close to being an expert, but....couldn't you just re-glue, clamp and screw the joints together and then plug, without removing the whole outwhale?
Jimmar:

Don't worry about your scarfs. The reason mine failed is that I was in a huge hurry when I machined the outwales -- desperate to finish my boat before I moved from my house-with-woodshop in Montana to an apartment in San Francisco -- and I ended up machining them such that the scarfs were rotated 90 degrees in the wrong direction. So there was way too much stress on the joints. Plus I put them exactly midships, where there is the maximum amount of bending stress on them, as I learned when I installed them. I really don't think there's a problem when the scarf is in the right plane, and is staggered properly. But I guess I'll find out.

Matt
Mattcliff
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Post by Mattcliff »

Bryan Hansel wrote:Could try heating the epoxy until it gives...

...this is exactly why I don't like glued on gunwales. Replacement is near impossible. With screws, you don't need to worry about that.
Yeah, I thought of heating the epoxy -- that's how I deal with ferrules on the bamboo fly rods I work on -- but the hull of my canoe is pretty much MADE of epoxy -- does that seem like a good idea? Plus I don't want to de-laminate the inwales, which are actually quite nice (and properly scarfed).

I can't just re-clamp and glue, because that won't fix the underlying problem (scarfs oriented in the wrong plane). Maybe I'll try the angle grinder route.

Thanks everyone.

Matt
woodman
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Can you use a magnet?

Post by woodman »

Can you use a magnet to find your screws?
Firstly see if you have any screws left over and if they will magnetise.
If they do hold the magnet on the inside of the hull and dust iron filings over the outside (vertical edge) of the gunwales.
The filings may hold better to the gunwale where the screws are.
Mark them and cut around.

Otherwise a small metal detector from radio shack (Dick Smith for us Aussies) might be the way to go.

Either way let us know what process you use and what the results are.

Woodman.
AlanWS
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Post by AlanWS »

Could you drill around the plugs with a self-centering plug cutter, then break out the plugs and remove the screws? A circular saw could be fitted with a base and a fence to guide it, and a kerf cut along the outwale, partway through. This kerf will make it a lot easier to chisel off the waste. I wouldn't cut all the way through with the saw because that would remove the support that keeps you from cutting into the hull.

By the way, if your scarf joints failed, I would use a shallower scarf angle, and possibly be more careful in how I glued them next time. The orientation of the scarf should not make too much difference to the strength, unless it also made you change the angle. An 8:1 scarf should be strong.
Alan
alick burt
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Post by alick burt »

Hi Matt
Before you make a mess removing the wood plugs or cutting around them try this.Locate the wood plug either by sighting along the gunwale edge with a carefully placed light or using a metal detector.Then put a (no 4metric or no 6 imperial) twin threaded woodscrew into the centre of the plug with a cordless driver and keep driving it in till it hits the centre of your screwhead underneath.When it does this continues driving it in and it should pull out the wood plug like a cork from a bottle!
Then you can remove your screws before cutting away your gunwales or repairing your splices as you wish.You should be able to re plug the holes again once you have made your changes or adjustments.
Regards
Alick Burt
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Jim Dodd
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Post by Jim Dodd »

Hi Matt
Did you glue and screw your inwhales to the hull, and then glue the outwhale on ?
That's how I build mine, and believe it's still the best.

That's another topic for discusion later.

For now, and to date I have'nt had to remove any gunnels.

I would start on the outwhale with a good block plane.

It's not fun, but necessary.

Good luck

Jim



I
Keep your paddle wet and your seat dry!
Mattcliff
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Joined: Mon Jun 25, 2007 3:26 pm

Outwales removed

Post by Mattcliff »

I posted on this a while back. Just got around to the actual job.

Turned out to be no big deal. A few strokes with a coping saw on either side of each screw, and then a tap of a chisel, and the screw heads are exposed. Then back out the screws. Gently tap a chisel under the outwale toward the end, then pry, and the whole thing peels off. By far the hardest part is backing out those soft brass screws. Some of them break.

I had this vision of the epoxy basically fusing the ash to the hull, so they were effectively one piece. Doesn't happen.

Now I just need to re-prime and paint the whole canoe to get rid of the ugly seam, and install the new outwales.

Matt
AlanWS
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Post by AlanWS »

I think there may be a problem either with your epoxy, or with your prep for it. The scarf joints should not fail, and the gunwale should be better attached than that. In this instance it was convenient to help you get the old outwale off, but you might want to glue a few test blocks to find how to get a better bond.

It's possible that being in a hurry caused you to stress the joints too soon. Epoxy that has just hardened is still quite weak, and continues to get stronger for a long time. Typically that's on the order of about a week for boatbuilding epoxies, though it varies with epoxy and temperature.

It is the slope of the scarf that should make more difference in strength, rather than the direction. Seven or eight to one is good. The main reason to make the plane of the scarf vertical is for looks, with a secondary reason that it takes less material for the same slope.
Alan
Mattcliff
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Joined: Mon Jun 25, 2007 3:26 pm

Post by Mattcliff »

All good advice, and much appreciated.

In retrospect, it is no surprise that these particular scarfs failed. If I were deliberately trying to make them fail, I'm not sure I could have done a better job. I put them exactly at the center of the canoe, meaning they were at the apex of the bend of the outwales, so there was a hinge-ing action on the horzontal plane of the scarf joints. I agree that normally orientation should not matter, but in this case I think it did (this is hard to describe but easily understood when you see it. I meant to have the plane aligned vertically, but due to a brain fart I machined the outwales 90 degrees off. Then it did not help that I ended up with a gunwale screw through the middle of the joints. Oh, and I used El Cheapo brand epoxy.

My inwale scarfs, which did not suffer from the above defects (other than the cheap epoxy), are doing just fine. We'll see how they hold up over time. The ratio of all the scarfs is about 6:1 -- the most I could get with my set-up.

My new outwales are also scarfed 6:1, but I've placed them where I've now learned the bending stress is least, and I've oriented the joint like the ones on the inwales (vertical glue plane). If they end up failing, I'll do another post for everyone's edification.

Thanks again for everyone's help.
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