Knots, wooden ones that is.

[Lon nan Gruagach]

I have some timber that I want to use to make some oars. It is a bit knotty though.
Do I not worry about it or knock them out and fill with epoxy or drill them out and fill. I was thinking of epoxy thickened with sawdust.
Whaddya reckon?

TIA
Dougal

 

[Wooden Boat Fittings]

If you're proposing to use solid timber with one or more knots running all the way through it, forget it. It's just not a viable option, epoxy or not.

There are two things you might possibly be able to do, depending on the number and severity of the knots and the length of the oars. The first is to rip the timber lengthwise, knock out the knots, glue the two pieces back together end-for-end, then fill the half holes with epoxy thickened with wood-flour, as you suggest. Or secondly, if only one or two knots, cut the timber into pieces so as to remove the knots from the stock altogether, and then scarf the remaining pieces of stock back together again

Personally, I'd be looking for straight-grained timber to start with.

Mike

 

[tolhurstorganic]

WBF is right find some decent timber it is not as if you will need very much. A very small knot in a large piece of timber is no problem but any knot in small dimension stuff will greatly weaken the piece. Epoxy is not as strong as longitudinal fibres of wood so would add no strength at all. Almost any straight grained timber will do, softwood is the usual, the largest knot I would want to see in an oar loom would be maximum size of 3-4mm, so about 10% of timber cross section size. Douglas fir, larch or any clear pine will do a good job. Ash is wonderful as it is very strong for its weight but not so easy to buy in small amounts.

 

[Lon nan Gruagach]

Thanks WBF and tolhurstorganic. The wood has already been planked half thickness in order to fold and glue together. The tree is just what had fallen and so easily available, buying better timber is tricky and expensive on the island. Just trying to make the most of what is to hand, but yeah, I was hoping for a cleaner cut.

 

[DownWest]

Agree, filling in knots with époxy is pretty useless, might as well just leave it in. One of the reasons I built all my spars with the 'birdsmouth' technique is I had difficulty finding decent stock, so scarfed the lathes with 12/1 joints and staggered the scarfes. It has been used for oars, but a bit of a faff. For more info, look at the Duckworks site or guggle birdsmouth spars
With grown masts the fibres have flowed round the knots, but once you plank the tree up, the fibres have been cut too much, so much weaker.

 

[Poignard]

"If a job's worth doing ....."

Imagine you went to buy some oars and you were shown some that had many holes of assorted sizes drilled into them at random. Would you buy them?

Well that's what you're planning to waste hours of your precious time making!

Get some decent timber from somewhere like Robbins Timber Ltd, Bristol, and do the job properly.

 

[Lon nan Gruagach]

Re: "If a job's worth doing ....."

Imagine you went to buy some oars and you were shown some that had many holes of assorted sizes drilled into them at random. Would you buy them?

Well that's what you're planning to waste hours of your precious time making!

Get some decent timber from somewhere like Robbins Timber Ltd, Bristol, and do the job properly.

Thanks, but an option that would not happen for a long time. My time is far more plentiful than dosh.

I'm kinda leaning towards the birds mouth lath and scarf approach.