Tillering a Bamboo back bow, advise needed!

[RT]

Hi,
 
I am now in the process of long string tiller. The long string is 6 inches long than the bow NTN. I have the backing thin down to 1/8 . I am trying to do a raw Boo back and raw boo belly bow. Most tillering will be on side of bow
 
I have pre-tapered the core and it bends nicely on the Dry -run glue up. Since the core have bee pretillered, I would expect little to be done after glue up
 

The bow is being pulled to 29" on the long string tiller and i need a bit of advise how to proceed.

RT

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[Pat B]

It would be good to see the unbraced profile.
    Looks like you need to leave the handle area alone and remove wood to get the limbs to bend more. I have always heard to toast the belly boo to improve compression and leave the back raw for its tensile strength.   Pat

[RT]

yeap, the belly boo has been tempered on the stove for 25 min prior to glue up, u will be amaze how good the raw boo kicks back to it original form using it as the core wood.

oh, I forget to mention that this is a bending bow right thru the handle section, will build up the handle section using leather later.

[M-P]

Hi,  A bend in the handle bow is good, but it needs to bend evenly along the whole length!  As Pat pointed out, there is too much bend in the handle and none elsewhere.   Leave the handle area alone and start tillering the limbs from ~ 1/3 to the tips.  I've seen bows tillered to a perfect arc of circle and bows left slightly flat in the handle ( but arc of circle through the rest  of the bow) but one that bends most in the handle risks an early demise.  Ron

[Marc St Louis]

You should make your long string shorter. There should be no slack.

[RT]

thanks guys for the tip, watch this space and will up date when i have some more work done on the bow. RT

[RT]

Hi all, pls see append pics, I have managed to put the bow on a short string at 4" brace height, look pretty
good to me, now for more tillering.

Can critics comments most welcome.

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[Gordon]

It seems to bend more in the handle than I like, but I would need to see the unbraced profile to be sure.

[Pat B]

Take more from the outer 1/2 of each limb. The curve from handle to tip should be almost the part of a circle. I usually keep the last 6" of limb tip stiff but have even bending through out the rest of the limb.
 Its coming along nicely. Just take your time, step back and look at the bend. You have to train your eyes to see proper tiller.     Pat

[RT]

the left limb near the mid section raw boo has crystalised, see pics

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[RT]

It will be a waste if i gave up here, so , i cut a raw boo approximately 4" long and 4 to 5 mm thick and backed up the area that has crystalised, it work, back on the tillering tree............................

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[RT]

drawn to draw length at 24"

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[RT]

here is the unbraced profile after it has reached final tiller, pretty much a straight bow, the final weight at 24" is 45 lbs, I am pretty happy of the out come on this bow.

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[RT]

Here is anothe pic of the bow drawn to 24" .........you will realise that the black rubber tubing holding up the crysrtalise area has been remove and replace with pressure wrap using fishing string................

Would like to hear comments on the tiller, what can i do to improve it better?

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[DanaM]

I still think the last 1/2 to 1/3 of each limb should bend a bit more.
I like your determination to see this thru, way to go.