Cracked Oar Blade

[JRG]

I saw the piece on rapairing an oar blade in the newest WB - Getting Started in Boats section using sailmakers twine. It seems to me that the bumps left by the twine will catch on things and just get in the way. The author referred to other methods of repairing cracked oars using epoxy. Anyone have an idea of how best to repair using the epoxy method? I'm trying to salvage an old set for many, many more years of use.

jrg

[Bob Smalser]

Gentle action with a heat gun or hair dryer thins unthickened epoxy to the consistency of water, allowing it to penetrate both into the wood and to the furthest depths of the crack.

Keep applying til it wont take any more, use rubber bands or surgical tubing as a (gentle) clamp if required, allow to cure, sand and repaint, and that's all you need to do. The epoxy joint created will be significantly stronger that the intact wood on either side of it.

[Thorne]

Yeah, I was stunned to see that piece too. Perhaps a field repair on a long trip might involve drilling holes and using twine -- but surely not a shop repair??

For any location near civilization you'd want to use epoxy as Bob suggests above. And with most oars these days being glued together right where the blade edges meet the loom, wouldn't most repairs be re-gluing cracked glue lines rather than repairing solid wood that was splitting?

For general-use oars I like laying several beads of heavily thickened epoxy along the bottom edge (aka 'wash') of the blade to protect against impact, abrasion and further splitting.

[Brian Palmer]

I thought the repair idea in WB #211 was pretty good. I would coat the repair with epoxy for abrasion resistance, though.

I could see doing the same repair to a wood canoe paddle, especially on a back woods trip, or with wood that is water saturated.

If the grain at the end of the crack runs out to the edge of the oar or paddle, and the crack is already more than halfway up the length of the blade, one option is to just complete the split so the piece is free. You then have good access to both faces and you can then glue the whole piece back together.

Brian
Brian

[skuthorp]

What Bob said, absolutely, and it's good to see you about Bob.
On the other hand this oar that was used on the Murray River is mine, but I've never tried to use it:
‘I found it on the woodheap at a Mallee (http://en.wikipedia.org/wiki/The_Mallee) (sandy desert without water) clearing sale. The closest water is an irrigation channel, near the Murray river. It’s six feet long, and made of wood, with iron spikes, some cotton sash cord, a little rubberised canvas, nails and red paint.
‘The roughly shaped triangular “blades” of the oar fixed by iron rod roughly peened over and in some cases using triangular galvanised “roves”. It’s absolutely out of balance, but a prize for my collection nevertheless!
http://intheboatshed.net/wp-content/uploads/2008/05/oar-2-470.jpg (http://intheboatshed.net/wp-content/uploads/2008/05/oar-2.jpg)
http://intheboatshed.net/wp-content/uploads/2008/05/oar-4.jpg

[Tom Hunter]

I did what Bob suggested to one of my oars three years ago, they are fine. It is a very simple repair.

[George Ray]

I often edge drill the blade near the tip and drive through a brass/bronze rod. (from welding supply)

[davebrown]

bob, if you are still reading this one, when you speak about heating epoxy, do you mean heating it before you mix, or heating it after you apply to the crack? i have a new set of oars i have been carving on foff and on for so long that one of them finally heat cracked at the blade tip, and i am trying to decide whether to force the crack open a bit and then clamp, or whether to try and get glue in the way it is. it runs about six inches up the blade from the end.

[Clinton B Chase]

Dave, Repairs like this depend on getting the glue into the crack...pry it open, use a syringe (and/or a flexible putty knife) to inject the crack with a ketchup consistency epoxy and close the crack...but clamp carefully, because it is easy to squeeze out ALL the glue you just injected. You want a little bit of a gap. If is is cosmetic you could use wood flour to help it blend with the wood or use an epoxy that cures clear.

[Bob Smalser]

bob, if you are still reading this one, when you speak about heating epoxy, do you mean heating it before you mix, or heating it after you apply to the crack? i have a new set of oars i have been carving on foff and on for so long that one of them finally heat cracked at the blade tip, and i am trying to decide whether to force the crack open a bit and then clamp, or whether to try and get glue in the way it is. it runs about six inches up the blade from the end.

Spatula it on cold then heat it gently as you work it into the cracks. Less messy.

And if you are making them from scratch or have some blade thickness to work with, in addition to George's bronze drift, a simple hardwood spline is easy to install using a router with a slotting cutter or a back saw and chisel.

http://pic20.picturetrail.com/VOL12/1104763/4518261/57039474.jpg

http://pic20.picturetrail.com/VOL12/1104763/4518261/56705590.jpg

[rbgarr]

I saw the piece on rapairing an oar blade in the newest WB - Getting Started in Boats section using sailmakers twine.

I thought it was wonderful.

[chiefypoo]

good to see you back on the forum Bob. and fellas todays price of oars and the labor to make new ones( if you can find decient material) will make you more aware of the importance of takeing good care of the ones you got, I treat mine like good que sticks.

[boylesboats]

Bob, that is great idea... warmin' the epoxy so it will flow better..

Have anyone tried CPES?.. it's runny as water, it'll seep in the cracks, soakin' into wood fibers

[SMARTINSEN]

The idea about drilling a hole at the end of the crack to stop the propagation is a good one, though.

[JimConlin]

Three thoughts-
As the mass of the oar blade is considerably greater than that of the epoxy to be administered to the crack, might it work even better to pre-heat the blade with heat lamps?

If the crack in a blade has been working for a while and is contaminated, I'd consider kerfing it out with a handsaw even if a spline or filler is needed.

Can't remember where I saw the idea of applying an epoxy-soaked nylon cord across the end of a blade. The elasticity of the nylon might get along with expansion.

[davebrown]

thanks clint and bob: again, hope i am not hijacking the post, but i think the saw kerf is a good idea for my split; perhaps i will also drop a 6" splinter of spruce in there as well just to hold it. it is hairline right now and goes about 3/4 deep towards opposing side, so it must be addressed if these are to last very long.

i have abused my first set of oars for 9 yrs thus far, and my second for 6...theya re a delight! i encourage any of the forumites to cut their own.

[boylesboats]

Can't remember where I saw the idea of applying an epoxy-soaked nylon cord across the end of a blade. The elasticity of the nylon might get along with expansion.

Gil Gilpatrick's book on "Strip Building Canoe".... Just read that chapter on making canoe paddle few days ago....