Ozbow

As you may be aware I employ the use of steam in quite a few of my bamboo backed recurve bows and have mentioned that I prefer this method over dry heat which at times requires the use of cooking oil.

Kerfing is another method that produces excellent results and a curve that does not pull out. As I have mentioned in previous posts heat induced curves can lose up to 50 percent of their initial curve.

This method can also be used to build reflex into straight limbed bows and help to minimise string follow.

Power tools offer a distinct advantage but the process can be carried out with hand tools.

The sample piece is half inch thick hickory and because of the radius of the curve I decided to use two kerfing cuts.

An Osage lamination off cut was used for the slats which were ground to the thickness of the saw cut in the sample piece.

The photographs probably illustrate the process better than words.
As a precaution small blocks clamped at the end of the cut prevents splitting down the limb.
The curving form below is the one I normally use when steaming limb tips.
The above is an overview of the process but you will need to carry out you own tests to determine limb thickness and number of kerfs required for the particular curve in the bow.

Daryl.

Very nifty Daryl ...it would look quite nice to once the bow has had the finish applied. So im guessing the curve is held in shape via the glue?

cmoore wrote:Very nifty Daryl ...it would look quite nice to once the bow has had the finish applied. So im guessing the curve is held in shape via the glue?

Same principle as a full laminate bow, only partially laminating the limbs. The glue holds the curve, or rather, the glue works against the shear stresses.

I would agree though, very nifty!

Nice little trick to try out at some stage!!

Good stuff Daryl.

Colin

another piece of ingenuity here Daryl. I will definitely keep it in mind when I ever get to do one of my bucket list bows, a bamboo backed recurve, which may or may not incorporate a static tip.

How cool is that!.........I would like to see the process of cutting the Kerfs Daryl. You have done a very neat even job there........

looking at the different radii lengths at the curve, I certainly can appreciate how much stress the wood fibres would be under just using the heat method. I doubt the fibres would be plastic enough to accommodate such treatment with out some internal conflict.It amazes me how they even manage to withstand the treatment as successfully as they do.

Great post Daryl, very thought provoking.

Cheers... Rod

Good afternoon gentlemen, thank you for your kind words.

The idea of kerfing limb tips has been around for a long time having first seen it when Dean Torges was building reflex into his bamboo backed Osage longbows earlier this century.

To the best of my knowledge not a great deal was done in kerfing recurved tips although I did manage to find the following image on the internet.
As heat bending appears to be difficult [or lack of understanding of particular timber properties] to some kerfing is an easy alternative.

mikaluger wrote:How cool is that!.........I would like to see the process of cutting the Kerfs Daryl. You have done a very neat even job there........

Mick, it is just a matter of setting the fence on the bandsaw and making the cuts. If doing two cuts I would make the one closest to the back a little longer for a more pleasing look.

bigbob wrote:looking at the different radii lengths at the curve, I certainly can appreciate how much stress the wood fibres would be under just using the heat method. I doubt the fibres would be plastic enough to accommodate such treatment with out some internal conflict.It amazes me how they even manage to withstand the treatment as successfully as they do.

Bob, if you go to 1.40 mins into the video it explains why timber bends once sufficent heat has been applied.

https://www.youtube.com/watch?v=4q8m-haPCxI

This is the stuff that binds the wood fibres together. Lignin extraction occurs during the pulping process of paper making.

rodlonq wrote:Great post Daryl, very thought provoking....

Rod, it may be useful for recurving timbers that have no history of being used as a bow wood.

Daryl.

heat bending wood is not entirely unlike doing the same on metal, as it involves molecular re distribution. With steel as the heat is applied, molecules become 'agitated' and this causes the linking of molecular chains to become extended and increase in dimensions. Annealing is a process that applies heat in a manner that allows said molecular chains to 'relax' a little, removing some of that induced stress caused by heat application. With timber it seems the plastic expansion of the lignin allows it to be formed into required shape. I still feel the fibres would be somewhat stressed and compromised beyond original state as there is no equivalent 'annealing process

You are a clever man, Daryl.

How did you come on that kerfing idea? I have never seen it discussed anywhere before; not even in my substantial library of old archer how-to books and magazines.

I have seen it used in Viking boat building but had never thought of using it in bow making... Something I'm definitely going to try on a bow.

After all that, I have just remembered that I have a couple of Ben Pearson Old Hickory static recurve bows which have had the recurves made in the same manner, but only with three laminations instead of Daryl's 5. There was only the one kerf cut into the limb end and a single piece glued in when the recurve was formed.

I wondered at the time what was going on with them and did not understand the reason that it was done when with his earlier static recurves in my collection, they were all wet bent. Now, I understand why they did it.

Dennis La Varenne wrote:After all that, I have just remembered that I have a couple of Ben Pearson Old Hickory static recurve bows which have had the recurves made in the same manner, but only with three laminations instead of Daryl's 5. There was only the one kerf cut into the limb end and a single piece glued in when the recurve was formed..... Now, I understand why they did it.

Dennis, thank you for filling in some of the gaps.

As mentioned previously my first introduction to this technique was watching Dean Torges building reflex into his bamboo backed Osage bows using this method.

My reason for using two kerfs was because the hickory offcut was 1/2" thick and I was unsure how it would react to cold bending.

When stocks of Degame become available I want to make a bamboo backed bow with recurved tips using a tapered slat in a contrasting colour.

I think you would have to agree that this a simple solution to what could be a more difficult situation. As a bonus the curve does not pull out compared to heat recurving.

Daryl.

greybeard wrote:I think you would have to agree that this a simple solution to what could be a more difficult situation. As a bonus the curve does not pull out compared to heat recurving.

Indeed it is. I should have remembered it earlier. Presently I am up at Jeff's place visiting, but when I get home, I will post some pics of how Ben Pearson did it which was almost certainly for the same reasons you propose it. It would also have to built greater rigidity into the recurves too.

Most of the old Ben Pearsons I have which are wet heat curved have very little of it left. In my old catalogues, you can see how they were done in his 'you finish' staves. The curves were heated into a 90 degree bent to the limb axis around a very small radius which you probably would not be able to do with anything other than Hickory.

On the subject of Lemonwood, in my old copies of ARCHERY which is/was the NFAA magazine, there was an 'ask the expert' section done by a bloke named Tracey Stalker. He was often asked about inducing reflex into Lemonwood using heat and his advice was always that it is very very difficult to get it to bend by conventional means back then. But there was never a mention of kerfing at any stage.

I remember your post about your Lemonwood bow earlier and my comments about the highland variety which was denser and harder than the lowland stuff. You have the same reference that I have for it from L.M. Stemmler's little book on the stuff, but his opinion is very much corroborated in the book - THE NEW ARCHERY – HOBBY, SPORT, CRAFT, Gordon, Paul H., D. Appleton-Century Co., New York, London, 1939 if you happen upon one. It is well worth a read. I am not sure if this Paul H. Gordon is the plastics man who founded Gordon Plastics though.

Dennis,

I find it interesting that whatever ideas we come up with in regards to wooden bows we usually find out at a later stage that it has all been done before.

Is the future for wooden bows in Australia on the decline?

With the majority of 'traditional style' archers preferring to shoot plastic bows I don't see a positive future for the wooden bow.

Daryl.

Daryl,

Yes, I am a with you on that one, however, some of us oldies doggedly hang onto our oldest archery traditions and try to pass them on to others whenever we can.

Wood bows will probably never be significant in Australia because the alternatives are so much easier to work with in this age of the 30-second attention span which also translates into the 30-second skill acquisition timespan.

Just the same, I will hang on in there so long as Ozbow continues and I will continue to rattle cages when I consider that handed down knowledge, traditions and techniques are being compromised. This is also why I am very glad to see a resurgence in interest in the skills of mediaeval Enlish archery even though it is not directly hunting related.

I have visited a good number of 'traditional' archery sites and joined very few because I find that Ozbow is arguably the only genuine traditional wood-based archery site left in the world, and we have a knowledge base of a breadth and depth that I have not found on any other site anywhere so far.

We have our punch-ups and always will as people do, but I am a stickler for evidence-based knowledge to substantiate a claim if it is not offered as opinion only. Many find this irritating as if I am questioning their integrity rather than the veracity of a claim.

I have also had many occasions to question much of our handed down knowledge when the reasons for an ancient item of knowledge seems very doubtful to me and that also irritates some. But the purpose in doing so is to find provable explanations for what has been a clearly functional technique for many centuries rather than an often 'best guess' more ancient explanation when the knowledge of those times did not allow it.

Just the same, I do not believe that in doing so we compromise those ancient skills rather than substantiate their worth through more modern understanding of how things work by the application of engineering principles not available to our forebears.

But one of my biggest concerns is the loss of our vocabulary and its correct use which is the only way by which we can maintain a direct link to our heritage - through its special language. When you lose the language of a culture, you lose the culture itself, because the lost language is non-replaceable with modern concepts.

Witness the loss of so much Aboriginal culture because the old people who speak their language die out and it is not passed on to the young people. It is just the same for us.

I did mean to mention this earlier but slipped my feeble mind I guess, I am not unfamiliar with the process of kerfing as it is a recognised procedure when making circular objects in wood working . The main point of difference is in that situation the cuts are mostly done cross ways to enable the piece to form a circular path. Doubt though I would have seen the light bulb moment with applying it to forming recurved tips though without Daryl's praiseworthy accomplishments.

Interesting, if you take it to the limit and kerf all the way to the centre of the stave then you have a bundle of laminations to glue together...

As promised earlier, here are some pictures of a Ben Pearson Deerslayer hickory static recurve which has been built using the kerfing system to make the recurve.

These bows were still being made by Pearson in 1958 (pp7 of the Ben Pearson 1958 catalogue) by which time, most of his line of bows was glassed. They were offered as a cheap bow for $US15.95 for the heavy model 503 bow with draw weights of 55, 60 and 65lbs and for $US12.95 for the lighter 503-1 model which came in draw weights from 40 , 45 and 50lbs. My bow is a 503-1 at 50lbs but has in excess of 2.5" of set in the upper limb and 4" in the lower limb, probably from standing reposed in a humid environment.

They were most notable for their sheer ugliness due to an obviously over-sized riser which tried to copy the then new style of overdraw arrow shelves noted in the blurb for this bow which were becoming popular back then.

This bow has lost its spiral leather handle wrapping as these bows so often do. But this bow is imminently restorable and the limbs can easily be straightened out.

Dennis,

Thank you for the pictures of the old Ben Pearson bow with the kerf tips. I believe tapered inserts as Pearson has done are a bonus for stiffening the curve.

Dennis La Varenne wrote:......They were most notable for their sheer ugliness due to an obviously over-sized riser

I would have to agree but I do think we should give some credit for trying different ideas.

What was noticeable in the photo was the geometry of the bow. Some allowances may have to be made because of the angle of the bow in the photograph.

The white lines in the photo depicting effective limb length from the riser are the same length. Daryl.