Wood filler vs epoxy for rib tips?
- Thread starter johnle
- Start date
Worth Gretter
LOVES Wooden Canoes
Johnie, I tested a bunch of wood fillers (including one by Minwax) for possible use on the outer hull of my canoe. I wanted the hull pretty smooth since I was going with Dacron instead of canvas.
For my test, I used a hammer to put big dimples in a scrap of cedar planking, filled the dimples with wood filler, varnished over it, then soaked in water. None of the wood fillers held up well.
I wound up using epoxy, after finding a way to weaken it so it would sand easier. Details are at
https://forums.wcha.org/threads/fairing-planking-or-canvas-or-both.15985/post-101983
In your case, I would definitely use epoxy, but not with micro balloons as you want strength in your rib ends (to hold the ring nails for the inwales). To use epoxy as a gap-filling adhesive, I have always used silica, although chopped fiber glass is also an option.
If the damage is not too bad, just glue with sawdust might also do the job.
-Worth
For my test, I used a hammer to put big dimples in a scrap of cedar planking, filled the dimples with wood filler, varnished over it, then soaked in water. None of the wood fillers held up well.
I wound up using epoxy, after finding a way to weaken it so it would sand easier. Details are at
https://forums.wcha.org/threads/fairing-planking-or-canvas-or-both.15985/post-101983
In your case, I would definitely use epoxy, but not with micro balloons as you want strength in your rib ends (to hold the ring nails for the inwales). To use epoxy as a gap-filling adhesive, I have always used silica, although chopped fiber glass is also an option.
If the damage is not too bad, just glue with sawdust might also do the job.
-Worth
Gil Cramer
The wooden canoe Shop, Inc.
Sometimes canoe builders used ribs that were long enough to tack to the rail, but not quite long enough to reach the top of the the rail. A small piece of rib was glued onto the rib after the outwale was installed. This looks better than either epoxy or filler. Obviously, I have done this on many occasions.
Michael Grace
Lifetime Member
I'm not sure the test above is a good one, especially not with respect to the question raised here. Smashing cedar with a hammer, filling the divots with wood filler, and then exposing this to water - of course the filler is destined to fail as the water swells the compressed wood back out. For cracks in rib tops, the best approach might be to glue properly-sized slivers of wood in place using either a quality wood glue like Titebond III or perhaps epoxy. Especially if defects are large, traditional epoxy can be a problem because of its brittleness and because it is so hard that fasteners cannot readily penetrate it. Gluing in wooden splines replaces wood with wood, and if epoxy is used its amount is limited.
MGC
Scrapmaker
I am not shy about using epoxy and prefer it to TB3 for many things, including rib tips. As has been noted, typical epoxies set brittle and may not be the best choice. For that specific reason, I keep a good supply of thickened G-Flex near my bench. It does not have the quick set time of most epoxies and because of this (and by design) it hardens with a degree of flexibility that is uncommon in most hardware store epoxies. It is not intended to be used as a filler, but it can be mixed with saw dust for that purpose. As a rule, if I am going to try to put a fastener through a filler of any kind, I pre-drill.
That out of the way, if the top of a rib is badly damaged, I splice on a replacement tip, using G-Flex.
That out of the way, if the top of a rib is badly damaged, I splice on a replacement tip, using G-Flex.
Michael Grace
Lifetime Member
Yes, I also use epoxy for many things including rib splices. Drill through solid epoxy before fastening - good advice. But I much prefer to use epoxy as a bonding agent rather than to bridge large gaps, preferring more wood and less epoxy wherever possible in a wooden boat.
And by the way, in addition to using and enjoying G-Flex, I've done a few tests (nothing truly scientific) and found that adding a little acetone to uncured epoxy results a softer, more flexible cured product. It might be worth doing some more careful tests to determine the effects of different ratios of epoxy and acetone on bond strength and ultimate hardness vs. flexibility, but initial tests suggest that epoxy can be modified to good effect. What I've done has been only with West System 105 resin and 205/206/207 hardeners; nothing with any other epoxies.
And by the way, in addition to using and enjoying G-Flex, I've done a few tests (nothing truly scientific) and found that adding a little acetone to uncured epoxy results a softer, more flexible cured product. It might be worth doing some more careful tests to determine the effects of different ratios of epoxy and acetone on bond strength and ultimate hardness vs. flexibility, but initial tests suggest that epoxy can be modified to good effect. What I've done has been only with West System 105 resin and 205/206/207 hardeners; nothing with any other epoxies.
chris pearson
Michigan Canoe Nut
I’ve never had a failure using a true marine grade epoxy like west system or total boat…
chris pearson
Michigan Canoe Nut
I would never do a “filler” for this. As Michael and Gil stated , add a pc or partial pc of wood.
Worth Gretter
LOVES Wooden Canoes
Well, a lot of options have been presented. You can glue in slivers, glue on a cap, or mix glue with sawdust. Or use epoxy.
But I will go out on a limb and say there are NO suitable wood fillers on the market. Or if there are, I have given up looking for them. The last one I tried was Famowood, which meets the waterproof test but fails otherwise because the color changes when you sand it.
Whatever you do, you should pre-drill for the inwale nails.
But I will go out on a limb and say there are NO suitable wood fillers on the market. Or if there are, I have given up looking for them. The last one I tried was Famowood, which meets the waterproof test but fails otherwise because the color changes when you sand it.
Whatever you do, you should pre-drill for the inwale nails.
Dave Osborn
LIFE MEMBER
I hate the look of filler repaired rib tips. Even when they are neatly done. I usually scarf in new tips, or do what Gil suggested, by shortening the tip and glueing in a new piece of wood. My goal is to make a canoe look like it’s never been repaired. Some folks have different expectations of the outcome.
