Repair or replace ribs and conditioning wood

[Dave Nagel]

I am getting ready to fix cracked ribs, replace planking and varnish and I have a couple questions.

First has anyone tried to remove cracked ribs, break them off at the crack then glue them back together? If you could do that then you would still have the original look of the wood. I guess the hard part would be removing the ribs without getting gnarly marks from where the tacks were clinched. Is there a way to get them out without grinding the ends off/gouging up the ribs?

I am also wondering what people do about conditioning the wood before varnishing. Are modern varnishes good enough now that pre conditioning is not needed. If it is needed what do people use?

I was also wondering if people varnish the outside of the canoe as well as the inside and why or why not.

I appreciate all your help and look forward to hearing what you have to say
Thanks
Dave

 

[ebeeby]

The rules of thumb for gluing wood would require a scarf joint that the old rib simply cannot provide. Good cedar does have a certain amount of give to it and this is necessary to the survival of the canoe. Obviously dried out cedar has les give and even new cedar will break, pushed to certain point.
That said, you want to put a fresh rib in and then work to match it in color to the other ribs.

The production shops simply were unwilling to spend the money for varnish of the outside of the planks. In a restoration, the idea is to get some moisture/oils back into the wood and mixtures of boiled linseed oil/turps are used. I varnished (using Spar varnish NOT polyurethane) the inside first before coating the outside with the linseed/turps knowing that some of the linseed/turps would flow through the plank seams and onto the inside. Conditioning before varnish consisted of removing all the old varnish and then sanding. Many use bleaches to remove any darkening of the wood as well (I did not).

You can see the process of my 1929 restoration here:

http://www.canoehullabaloo.com/beeby-canoe/intro.html

Click on the 3 links once you get to this page.

 

[Dave Nagel]

Thanks for the reply. Sounds Like I have a plan for conditioning the wood. On the gluing the ribs, my experience has been if you have wood that has broken and you can fit it back just how they were and glue that joint it will be as strong or stronger than it was. Are you saying that if you don't scarf it it will not flex? or were you talking about softening it up by conditioning it? Maybe both.

Dave

 

[Canerodz]

I think the point is that it is wood under stress, and it won't function as it should with a glued butt joint. Gluing wood end grain to end grain is inherently the weakest joint we can make, splicing on a long diagonal cut gets around this by effectively gluing face grain. There is not enough wood in the original parts to cut the splice joint properly. The joint wouldn't hold when the canoe flexed.

 

[Dave Nagel]

Thank you both for the input. I figured there was a reason everybody replaces or splices them.

When splicing rib tips how do you cut the old rib straight and square so they match the new one without taking them off the canoe?

Dave

 

[Dave Osborn]

Wait!!

There is a way to fix a broken rib, provided that it is not totally disarticulated. I know there are detractors from this method out there, but it has worked well for me. Repairing a broken or cracked rib or two in a hull does not in my opinion make for a weaker hull. The method that I use is called a back-side rib repair. In cases that I deem a backside repair acceptable, I remove the planking around the break and cut out a rectangle about two inches either side of the crack, and to about 1/4 inch from the each edge. I chisel out about 1/2 the thickness of the rib and clue in a hardwood patch that fits the rectangular area that you have chiseled out. Glue and clamp in the patch with epoxy or equivalent. You may have to shape the patch with a curve if needed. Generally on a straight part of the rib, the hardwood patch draws up the broken sections to become straight again. The reason that I do this is because (to me) there is nothing like original patina. A brand new white cedar rib will stick out like a sore thumb unless you are a master at staining to match. The crack will still show, but the strength, and patina are still there.

Dave

 

[113932]

Related Cracked Rib Question

I have a rib that is cracked one half of the way through on the top side. This crack then joins a one inch crack that splits the rib down the middle for an inch. The bottom half of the thickness of the rib remains solid.

Does this justify replacing the whole rib?

 

[Dan Lindberg]

I'll second Dave's backside repair, it's common method of repairing/retaining a cracked rib.

I've done it several times, but only when replacing the rib was a larger impact to the canoe, ie, only 1 rib was broken and a single new rib would stickout, or maybe a cant rib that was broken away from the main bend.

If a number of ribs needed replacing, then they all got replaced.

As for the method, I'm even less traditional then Dave. I've just exposed the back of the rib, and made a cavity about 2" long by 3/4 the width of the rib, ie, leave maybe 1/4" of "wall" at the edge, and then I just filled the cavity with epoxy "peanut butter". ie, sawdust filled resin. Cover the resin with a piece of plastic of wax paper and smooth flush with the rib surface. When hardened, a light sanding and replace the planking.

If you cut the planking carefully, you won't be able to find the repair inside.

As for glueing a cracked rib, don't . I've tried and I suspect that due to debrie and/or oil in the wood, epoxy doesn't/didn't stick, at least for me. And I wouldn't use any other glue for this job.

Forgot, "113", it depends on how many others you need to replace, but in my (limited) experience, if one rib looked as you describe, there were others, and then I would replace all of them.

Dan

 

[113932]

Cracks

I like the sound of the half-way method.
I have two ribs cracked half way through on the top side. The half way method would not improve the situation. Is a half-way cracked rib a dead rib?

 

[Douglas Ingram]

If the fracture of the broken rib is not severe, then I use the back-side rib repair as a matter of course. My variation is that I make the slot as long as possible, trying to get about 5" length, and I try and go as deep as possible, leaving maybe 1/8" at the focus of the fracture. Long sloping ramps out of the slot make for a good glue joint. I use cedar slats to maintain the same kind of structure character as the rib, and to allow the tacks to function as usual. Epoxy to glue them in, of course.