Bamboo backing sapling bow

[Roballa]

Hi everyone,
I’m very new to the world of bow making, but it’s safe to say I’m completely hooked and loving the variety of different techniques, and making small improvements along the way. My first bow was made at a workshop, and developed a small crack on one of the limbs. I recognise now it was because the board I was given had some grain run-off, and I salvaged it using linen thread and a linen fabric backing. My next two bows were a pyramid board bow design, with leopard print linen backing on instruction from my youngest son! 40Lb @ 27 inches for me, and 15Lb at 22 inches for my son.

I’ve been using spotted gum boards, which is one of the best bow woods in Australia. Unfortunately, none of our wood suppliers have even heard of Osage!

Chinese Elm is a pest species here, but there are some trees growing near my place, and I have two saplings drying in the garage. As a white wood, I thought it might be interesting to try a bamboo backing this time. I’ve seen a few videos where the back is fairly flat, so the bamboo can be thinned, tillered and applied. My question is regarding sapling bows. I understand the aim is to not violate the 1st growth ring below the bark. However, this will make a very curved back after tillering.
Has anyone applied bamboo backing to a sapling bow? Does the curved back make it too difficult to apply the bamboo, or if the bamboo is thin enough, can it still wrap itself to the back? I could easily leave it bare, or use my usual linen technique - however I thought it might be interesting to try something different, especially on a wood variety that is prone to set.

Sorry for the long post! Hope that makes sense. Thanks for any tips.

[Pat B]

Welcome to PA, Roballa. Do you have any pics of your bow(s).

[Hamish]

Hey Roballa, fellow Aussie here. Plenty of bows have been made out of Chinese elm. It doesn't need a backing unless the stave has been damaged.
Either take the bark off and use the surface just under it, or go down to a lower growth ring if you choose.

Bamboo backing needs a flat surface to glue it on to the stave. You need to plane it or rasp it flat, otherwise you would get poor adhesion. If you try and force the bamboo flat from clamping, it will split lengthwise.

Too reduce set in whitewoods you can heat treat, and or reflex the stave over a form.

A lot of chinese elm grows around northern NSW, and southern QLD. If you let me know what State you're in I can recommend some places that sell suitable species of wood for bows?
                                                    Hamish.

[willie]

welcome Roballa

if your elm is prone to set, heatreating will help as Hamish mentioned, although perhaps he can clarify how reflexing will help reduce set also.

putting a stiffer materiel on the back (which I assume bamboo is) will actually cause more set

[Hamish]

Heat induced reflex...  The reflexing if done 1-2" will not stop set but it will compensate for apparent set. The bow will now  perform better in cast and speed than if you hadn't reflexed it. Combine that with a deep heat treat on the reflex form, which will drive out moisture and temper the wood, giving you the best chance to minimize set during tillering.

[bassman211]

I have only ever worked with American elm, and some very good bow builders claim Chinese elm is better for bow making. Elm is my favorite white wood, but even small knots on the bow's back can be problematic in my experience with the elm that I have used. With heavy belly heat treat you can reflex elm, and it will hold some reflex after tillering. In the past I have had failures from even small knots on the bow's back, but with a clean back it  makes a sound bow that is a good shooter. JME

[Roballa]

Thanks everyone. Great advice! Hamish - I’m in Samford Valley, Brisbane so there are a few Chinese Elms and saplings nearby.

Regarding the reflex - as per a technique I saw online (helping a sapling to dry by thinning out the belly), I used a draw knife to take the sapling belly halfway through the thickness on each limb, sealing the back and ends and leaving the handle section full thickness. While monitoring the drying process I’ve noticed it’s naturally pulled itself into a reflex. I’ve left the width profile alone for now (while drying) to avoid twisting. Is this enough reflex and/or would you heat treat anyway to ‘lock’ it in this shape?

I’ll attach a couple of pics of the sapling back and side, and sitting on a bench showing a 1.5inch reflex bend at the handle (apologies if that’s the wrong terminology!)

I’ll also send a couple of pics of my recent spotted gum board bow and late-ish tiller…

Rob

[Roballa]

…and the spotted gum board bow…

[Roballa]

Sorry - trying to get the hang of attaching pics!
Hopefully a couple more of the spotted gum bow. Rob

[superdav95]

Looking pretty darn good!   As for the boo backing on a sapling, I agree with hamish.  The only other thing you could try if you are wanting to keep the crowned back of the sapling is to dish out your backing strip to match very closely.  Find a boo strip that has a similar crown contour to your sapling back perhaps???  I’ve not tried this yet but it makes sense that it could work.  I’ve done some boo backing strips on smaller to medium diameter tree staves but not saplings.  I’ve always flattened them to matching boo strip and been fine.  The other issue is to ensure you trap the back when tillering and not make your strip too thick so that it overpowers the belly wood.  You will get chrystals forming in belly.  Fire hardening helps with this but wood is wood and the boo strip will overpower if too thick.  Getting the taper right is also important.  Just a few thoughts.  Best of luck

[Hamish]

Hey Rob, The spotted gum bow looks really good.

I would put the elm stave on a form for heat treating, and just to even up the reflex, makes tillering easier. Yes, it is a fair bit of work, especially if you need to make a form, but it can be used on further staves.

For bow timber, I'd try Matthei Timber at Yatala. It's at the other end of Brisbane to you. I haven't been there for a while, (I live down in Sydney)but they stocked Bulletwood/Beefwood/Massandubra, locally called Pacific jarrah. I rate this as a top bow wood, when backed with boo, hickory, or even a strip of straight grained bulletwood, and reflexed 1-2" in glue up.
 They also stocked some lemonwood, I think that was called Pacific ash, or something similar. Again, another highly rated bow wood when used the same way as with bulletwood, backed.
They had a small amount of Ipe, another top bow wood.

There should also be some bow wood, growing around your region. Red/Pink ash, alphtonia excelsa. Its usually a small to medium understory tree in dry sclerophyll forests. In rainforest areas, Saffronheart is another great native bowwood.

[Roballa]

Thanks for all the encouragement and tips! Hamish - I’ll definitely check out the Yatala place next time I’m passing by.

After taking on board your advice I’ll leave the boo backing for another board bow instead of trying to back the elm sapling. In that case I’ll definitely try the heat gun on the belly as Hamish suggested (another new technique to try out!).

Just a couple of quick questions re the heat treating…

1. Should I wait for the sapling to dry out to stable weight/moisture content, then roughly shape and floor filler before heat treating while clamped to a reflex mould?

2. Would you heat treat again in the reflex mould after final tillering to further reduce set and strengthen the bow?

I’ve heard heat treating is good for white woods like this one, but comes at the cost of weakening the fibres - too much of a good thing?!

Thanks again Hamish and co - Keen to hear your thoughts on the right ‘order of operations’ to approach the heat treating for the elm sapling.

Cheers, Rob

[Hamish]

Keep the tips wide, and start to floor tiller the limbs, so you get about 4-6" of travel. It should reach ambient moisture content quite quickly. Check it after a couple of weeks. You can correct the reflex without a really deep heat treat, with a heat gun, it still should perform really well.
If it's starting to take more set than you like during tillering, you can put it back on the form and give it a really long toasting session. After a good even heating you then try for an evenly toasted belly, darkened look(though not charred). That would absolutely maximise the stave's performance.

There are plenty of good videos about fire tempering white wood bows in 24hrs. Clay Hayes has done some which from memory were pretty good.
Its a little riskier than using a heat gun. Never tried it myself, but by all accounts, if done properly works like a dream for whitewood bows. Hopefully some other guys that do it regularly will chime in for some more in depth help.

Looking forward to seeing your results.