Tapered ribs

[Jeff block]

On my 1919 old town ideal model I am replacing 4 ribs. Three are in a row. They are cracked below the water line a little .I see the tapered sides all point towards the center of the canoe. But I also see the tapers are all slightly different from rib to rib through out the canoe. The tapering starts in different spots with different widths through the tapers. So my question is we’re they made by hand? My table saw makes the taper very definite and the same. The originals seem to be rounded a little. So how do I make the replacements? I replaced one rib with mixed results. Should I only be splicing in a new rib at the broken spot?

 

[patrick corry]

Generally speaking, each rib moving away from the center of a canoe will be progressively shorter in overall length (gunwale to gunwale). In practice, the rib blanks cut for much of the center third (perhaps) of a canoe will be cut to the same length, another batch cut to a similar length for the next couple of feet, and a shorter batch cut for ends of the canoe. Each batch will be pre-tapered prior to steaming.

If all the rib blanks were cut to the same length, pre-tapered, then as ribs neared the stems the taper would progressively approach the gunwale, resulting in less visible taper each time. I think the appropriate approach would to be to cut each rib blank only about 1" longer at each gunwale, then cut tapers to a consistent length on a table saw jig. When steamed each marked rib would be installed at it's correspondingly marked final location.

 

[Jeff block]

Thanks Patrick

 

[1905Gerrish]

Jeff,
Don't hesitate to try backside rib repairs for cracked ribs. Broken with wood missing is one thing but a crack can be repaired without the much more work that you are experiencing keeping the original color and patina. Ribs made but hand you ask above, you bet! I see ribs placed in backwards occasionally. But the men that made these are just like todays workers. Days ended, work weeks ended and then there was lunch time each day. I'm sure some said "I think we can get one more in" a few times! The newer the canoe the less workmanship in each I find. Grades of course as well make a difference. Also, some manufacturers put much more effort into making finer crafts than others. I won't mention names to stir pots. I tend to hand sand replacement parts quite a bit to get them perfect in my eyes but I work on my own items and don't turn over many canoes. Tapers, bevels and champers for sure. You ask how do I make replacements above, simple, trace the original. Duct tape them together if need be and get a helper. Start in the middle and roll the rib on the strait new stock and have a helper trace the rib as you roll. Cut the excess off with the table saw and make your rough bevels and tapers with your benchtop sander. I steam and bend from here as some break. If the rib comes out well, the orbital sander and hand sanding finish the rib off.
Zack

 

[Jeff block]

I will have to check out the backside rib repair method. I think one is cracked at a bend causing the planking to bow out some but I could expose it and epoxy it together in that spot and c clamp it at the right curvature. If not, I can stick to plan A and change it. The fourth rib is near the stem and the hull is not deformed there so may be easier. Thank you for your input.

 

[MGC]

I will have to check out the backside rib repair method. .

There are a number of ways to repair a rib from "the backside". All of them involve removing cracked wood from the rib and replacing it with fresh solid wood. The epoxy you select is important. You need to use one that is both strong and somewhat flexible even when set. I use thickened West Systems G-Flex whenever I am repairing or splicing canoe wood.
Here are a few shots of a backside repair...when you remove the planking be sure that you do not put splices in line with each other. You will need to remove longer pieces than you might want to get it right. Make your cuts in the middle of a rib.
An alternative method is to carefully remove the rib, repair it and replace it. If you have a historic boat that you want keep original, you might consider this.

 

[dtdcanoes]

And if not said prior , don't forget to pre-drill for a plank tack if one must go there or you get a pre-clinch as it were and a loose plank, ya.
Dave

 

[Michael Grace]

Mike (MGC) provides excellent advice on using backside rib repairs to save cracked ribs, and many of us have used this technique effectively. Not to denigrate anyone else's approach, but I do backside rib repairs a bit differently.

I do backside rib repairs in place as MGC shows, but instead of a square-ended mortice in the rib, I taper the slots for the spline smoothly from full depth around the rib crack to nothing at the surface of the rib. A square-ended repair means that the grain of the spline and the grain of the rib meet end-to-end, and end-grain glue-ups are generally considered weak. The flats of the spline and rib should make for an exceptionally strong joint but the end-to-end junctions may set up for relatively easy breaks at one or both ends of the spline sometime in the future. After cutting the slot in the bib, all that's left of continuous rib grain are the small bits on either side and a thin layer at the inside surface of the rib - very weak. With a tapered spline and slot, you've got that (very) little bit of original strength plus the strength of a long tapered glue joint. Just as spliced rib tops and spliced gunwale repairs benefit from a long, tapered glue surface, backside rib repairs should as well.

Just my approach for what it's worth... everyone can choose their own roads.

Oh, and heed Dave's excellent advice... If you use a good hardwood for the spline and no matter what kind of wood if you use epoxy, the canoe tacks don't like to go in! Pre-drilling with a tiny bit solves that problem.

Michael

 

[Todd F]

Michael, please share some photos of your technique when able.

 

[MGC]

Having spent many years designing complex high-speed machines and mechanisms and with a related background in tribology, I'd have to agree that Michael's observation that a tapered splice eliminate stress raisers...
That said, it has been my experience that the demonstrated butted splice is more than adequate presuming that it is properly fit and bonded with the correct adhesive. I have never had such a joint fail even subject to hard use.
I always use a splice made from the same material as the rib, cedar. If you chose to use hardwood, it would have dissimilar load behavior and would definitely require a tapered splice to distribute stresses across the joined areas.

 

[Todd F]

I had to look up tribology.....

 

[Michael Grace]

Here's a photo of a backside repair in my shop years ago. You can see that I backed up the rib during repair with a shaped form because the rib was deformed from the crack. In this case clamps on the spline pulled everything into proper position. Sometimes in a case like this I'll also make an outside clamping form to ensure everything trues up properly. I make the spline deeper than the slot cut into the rib, and I make it the same thickness its entire length. After the glue (here it's epoxy with cotton microfibers) has set, just use chisels, planes and spokeshaves to bring the spline down to the level of the rib's surface.

Just now I couldn't find the better photos showing more elaborate backside repairs, but if I find them I'll post more. This rib was cracked right in the tightest part of the bilge turn, and I wondered how it would fare. It has now been about 12 years and the repair has performed perfectly.

After all this, the hull was just as smooth as it was originally. The next rib over is a replacement because the original had two breaks and the section between breaks was missing.

In case it hasn't already been said, remove the tacks and planking carefully around the ribs that will be serviced. With care the planking can be put back in its original position, and from inside the canoe no one will ever know that a repair has been made.

And then just for fun, see the attached thumbnail for some nanotribology (from an unusual source - the skin of pythons!)

 

[dtdcanoes]

TODD, I think it is a threesome at the lanes for a the best-of-three challenge . risers and stresses .....what Rollin solves with the stand back and stare protocol. I have always " imagined " that the maximum area in contact with proper glue would best resist the forces at each end of the insert especially when it is hard to imagine there ever being much force directed at a significant angle to the joint when the rib is well fastened beginning close to the end edges. But I do wonder how much we should rely upon our imaginations to solve this knotty problem .
Have fun, TODD

 

[Todd F]

OK, I have a degree in Anthropology and a minor in Marine Ecology. For the last 30 years I worked in a different profession, certainly not tribology! I like Rollins protocol, I will stand back and stare...and learn!

 

[MGC]

Michael, your example is a perfect representation of the amount of creative problem solving that some repairs may require. When the repair is on such a shaped part of the hull, making a fitting form to shape the splice to fit is absolutely necessary. It is required to hold the piece on place while the epoxy sets. And here, making a splice to join the parts is absolutely necessary. A square edge (as in mine) would not benefit from the strength of the adhesive. In the case I shared, the joined areas is actually stronger than the adjoining areas. when the planking is tacked back in place, it's a good as new.
The attached piece is brilliantly written. The visual images throughout create crystal-clear images. I particularly love the concertina locomotion.

 

[Gil Cramer]

I have never been a big fan of back side rib repairs, and what I never understood was why one would do a backside repair after removing the planking. Why not chisel a space through the planking and rib , and then install a splint? Back side repairs have a place on truly historic canoes, but otherwise; I'll replace the rib----but I love bending ribs. Personal preference!!!!

 

[Todd F]

 

[MGC]

I have never been a big fan of back side rib repairs, and what I never understood was why one would do a backside repair after removing the planking. Why not chisel a space through the planking and rib , and then install a splint? Back side repairs have a place on truly historic canoes, but otherwise; I'll replace the rib----but I love bending ribs. Personal preference!!!!

I 100% agree (except for the splint). Unless a canoe is something pretty special and you are trying to preserve the original wood, a rib replacement is also my first choice. To do a backside splice you need to cut into perfectly nice long runs of planking.
I have backside splices on a Rushton and a Gerrish.

 

[Dave Osborn]

I make mine like this…. Pre-bend the patch if necessary. Always use a backer. (I’ve got a shelf full of them)
I also shoot epoxy into the crack if possible to stabilize it prior chiseling out the pocket. Rounded or pointed ends to minimize stress risers.
I’d rather see a secured crack on a rib than try to match patina on a brand new white cedar rib.

 

[Michael Grace]

Personal preference!!!!

Agreed. My personal preference is like Dave's. I find a small crack far less obvious than a new rib, and in practice I've never found a few shortened planks to be a problem even after many years of use. I try to span at least 5 ribs when removing planking, and I always try to have at least one end of the removed plank to be at an original plank end to reduce the number of junctions.

I work carefully to match new ribs (and planking) to old, and I've gotten very good at it. Even so and even if other people don't pick out new material, I still can. So I prefer a repair rather than replacement as long as it can be made structurally sound and and not obvious. My own canoes with splices are certainly worth it to me (Gerrish, Rushton, long-decked courting canoe, etc.). The one in the photo above is an otherwise perfect Morris Type 3 - not exceptionally rare but every part of it other than two ribs, cane, and canvas was perfect. If I'm restoring for someone else, owners get the pros and cons of replacing vs. repairing cracked ribs and they see examples, and then the approach is whatever the owners want.

And by the way, this discussion illustrates a great value of the WCHA. This free exchange of ideas, like so many others on these forums, is very helpful. I've changed or modified my approaches many times based upon things I've learned from the good folks here. If this were easy and if there weren't still new things to be learned, I would have gotten bored a long time ago.