Saturday, 23 July 2016

The Knot Dilemma, and a New Technique?

The 60 pounder has a good few knots, but one is a bit of a tease.
Do you leave a knot until the bow explodes and then sagely rub your chin and exclaim "Ah I knew it would break there" ? Or do you take preventative action?
It's a fairly small knot, but this a relatively short bow and a good poundage.

The problem with knots is, you can't believe a word they say! This one is a foot from the nock, which is exactly where longbows like to break, it's dead centre in the limb running right through belly to back. It looks solid on the belly but has a fine black ring round clean wood on the back, there is a raised streak of heartwood showing on back too above and below the knot (see first pic)
Now I've made bows with heartwood showing through on the back before ("Ridgeback" being the most notable), but this one had me worried...
I had a little pick at the knot with my ground down needle file and it waggles, so I picked it out and it went deeper and deeper... it went so deep, I soon found I'd broken into the London Underground system (Ok, slight exag' ).
I'd been thinking for a while that a V shaped piece of sapwood inlaid over a filled knot would be a great way of fixing knots. I suggested similar to a bloke on a Warbow forum who was asking how to deal with a knot, e.g excavate and fill the knot then do a sapwood patch over it. He didn't want to do it because it would "spoil the look of the bow". Now one of my pet hates is people who ask your advice and then tell you why it's wrong. I'll offer advice and people are fee to take it or leave it, but I do rather object to having to justify my opinion when I've already offered supporting evidence.... whoops sorry about that.

Anyhow, having cleaned out the hole (or so I thought) I used a Stanley (craft) knife to cut out a deep V, widest and deepest where the knot was, tapering out to nothing either side (total length about 2 1/4" ). Now the V was opened up I could see into the hole better, and it still needed more cleaning out!
I think it's the big pocket of unsound wood which knots conceal that is the big danger. Ok, there is a weakness and discontinuity in the back which was what was worrying me in the first place, but you have to deal with the whole problem.
I filled the cavity with Yew dust and epoxy mix, mixed fairy dry and packed in tight. When that had dried the V was cleaned up again and the fillet of sapwood made to fit.
The piece of sapwood was cut from an off-cut of the same wood taking care to have the grain orientation the same. It was mostly whittled with the Stanley knife and cleaned up on the belt sander to give a press fit into the V. Once it fit in, I rasped off most of the excess, this make it more flexible and more able to deform into the V. It was glued in with Resintite and left clamped up firmly overnight. This morning I carefully rasped, scraped and sanded to blend it in.

I s'pose I should mention the other ways to deal with the problem:-
With other woods and other styles of bow like an Osage American Longbow or primitive, it would be a matter of leaving a knot or popping it out to make a hole and following the grain as it flows round making the bow wider at that point, so the wood missing form the hole is effectively just flowing round the sides of the limb. On an English longbow the advice is often to allow more thickness/depth on the back. I have seen bows with extra wood on the belly too, which I think is wrong as it will cause a stiff spot, and by inference a weak point either side of that. The problem with extra wood on the back, is it doesn't necessarily give you more continuous sapwood to take the strain. Effectively if the knot is like a hole, then extra wood on the back is just making a deeper hole, and holes aren't very good in tension! Anyhow, make up your own minds, take each knot as an individual challenge, and don't assume there is sound wood under the surface.

Time will tell if it is a good fix, and we'll never know if it would have broken.
I'll let you decide if I've spoiled the look of the bow.


  1. Hi Derek
    I would tell myself its all about doing what is best for the bow based on how the wood presents itself, not about how it looks. and I'd choose a patch over two separate limbs any day.
    Which log was the bow made out of?
    Thanks for digging deeper and saving some misery down under.

    1. It's from neither of the logs you sent as I want them to season.
      Do you want BLACK or PALE horn nocks? I want to get them done so I can finish the bow.
      (I did E-mail you asking this 3 days ago!)

  2. I can't be arsed to wait any longer, I'll go for pale to make it stand out less if it is to be used for hunting.

    1. would have said pale.
      apologies been of that account recently.

  3. Your patch work always amazes me awesome work Del! Keep em' COMING! Cheers- Brendan