Plugging know holes

[Gordon Hafner]

Is there any downside to plugging knot holes in cedar planking with a hardwood dowel and epoxy (after drilling out of course)?

[Chris Woodward]

Re: Plugging know holes

Use cedar plugs.

[Canoeyawl]

Re: Plugging know holes

Dowels are wicks...
use a bung cut with a hole saw maybe?

[Gordon Hafner]

Re: Plugging know holes

So I've tried using my Fuller countersink/counterbore bits, and the plugs they produce tend to be a bit too short, even though the planks are only 7/16" thick. Anybody have other thoughts? I've seen recommendations on using a lathe to cut longer ones, but that's a bit pricey .

[Peerie Maa]

Re: Plugging know holes

So I've tried using my Fuller countersink/counterbore bits, and the plugs they produce tend to be a bit too short, even though the planks are only 7/16" thick. Anybody have other thoughts? I've seen recommendations on using a lathe to cut longer ones, but that's a bit pricey .

Glue one on top of the other, with the glue line halfway through. Use epoxy and there should be no issue.

[wizbang 13]

Re: Plugging know holes

the grain goes the wrong way
get better wood
if yer gonna use epoxy, jus fill em up

[long time lurker]

Re: Plugging know holes

Is there any downside to plugging knot holes in cedar planking with a hardwood dowel and epoxy (after drilling out of course)?

Definitely.

The grain will be at 90 degrees to the grain of the planking. They will shrink and swell at different rates which will result in the planks cracking.

Epoxy won't shrink or swell at all, same results.

Here's how to do it right.

Cut a rectangular patch large enough to entirely cover the hole and any curvy grain fore and aft of the hole. Your planking is flat grain so use flat grain of the same species to make the patch. It's ends and edges should have very slight bevels so that when you press it in it tightens and you get a nice fit.

Trace the smaller face onto the plank with a knife. Route/chisel it out 1/2 way through the plank. Press the patch (Dutchman) into the chiseled out area bedded in epoxy. Make sure to soak the exposed end grain areas in epoxy first, applying all that they will soak up.

Once the glue has cured repeat on the inside but shorter and narrower. Fair it in, seal it with epoxy and you'll be good for life.

If the holes are really small just fill them with Sika. You can use a coutersink to bevel the inside and outside of the small holes to increase bonding area and shape the hole so that the Sika will never fall out, not that it would anyway. Sealing the beveled holes first with epoxy will stabilize the plank.

https://www.xometry.com/resources/ma...%20cylindrical.

[Peerie Maa]

Re: Plugging know holes

For lots of small dead knots, that is overkill.
I have seen the knothole drilled out and a wedged plug like a treenail used. Cross-grained bungs glued in is less obtrusive. After all you would not cover every counter bored fastening with a Dutchman, although if you are salvaging a plank with one big dead knot that may be appropriate.

[Paul Schweiss]

Re: Plugging know holes

When finishing my apprenticeship in Norway, we were building a lot of modest sized lapstrake vessels, but also did one 40’ carvel plank fish boat. Any knots that had a black line around them were drilled out and plugged with a proper bung, the live knots were left alone. The planking was probably net 1-1/2”, of Norwegian Pine (Furu) which was very similar to Western Larch The bungs were put in like finish work, with the grain paralleling the grain of the plank, with low tech glue. These were working boats that needed to be built to a price but had to withstand a rugged working environment.
Fuller makes plug cutters that eject the bung when drilled all the way through the stock, you would need to see how many diameters to best get rid of the size knots in your stock.