Boo back and Belly- Please help me with this Tiller ?

[robin]

Hi, This is a Boo back and belly bow. Specs are

Boo back 4mm and taper to 2.5mm
Core is balau wood 4mm tapers to 2.5mm
13.5 inch long and one inch thick handle
Boo Belly (heat tempered 4mm taper to 2.5 mm)

Can some one advise me where I should the limbs to be more bending before I start pulling the limbs more ?

 https://goo.gl/photos/KMCX7gmSKMmWQJxz9

Thank you for your help and advise.  ;D

[Roy from Pa]

First thing I suggest is to get rid of that super long tillering string. Put a string on it that lays tight against the belly when the bow is strung.

[robin]

Ok done  that...what's next?

[Roy from Pa]

Begin working the bow on the tree, pull the tree rope down to about 3 inches a good 25 times, look for a nice even bend. If there are weak spots, stay away from them and remove some material from any flat spots. Don't pull the bow down any farther till you have it bending nice and even. Then pull it about 2 inches more than you did the last time, 25 times. Work the bow about 25 times after removing any material. Once the limb tips are traveling down to about 9 inches and it's bending nice and even, shorten up the string so you have about a 3" brace height. And continue working the bow down the tree 2 inches farther than before, looking for an even bend. Stay away from weak spots and remove a little material from any flat spots. Once the tips are bending to about 9 inches, shorten the string to a 6" brace height and continue tillering to your draw length. All the while maintaining an even bend. Don't ever pull the bow farther until you have an even bend.

With this being an all bamboo bow, you will remove wood from the edges of the limbs, not off the back or belly.

[robin]

Ok done  that...what's next?

[Roy from Pa]

Well I can't see how you did that so fast, but I guess the bow is done! How's it look?

[robin]

Sorry duplicated post wll revert again when done. Tks

[mikkekeswick]

I've done a few of these and you pretty much need to get it perfect before glue-up! It took me three attempts to get a bow of the correct poundage. High, low and then just right.
The problem is that with 'normal' tillering you are removing wood (mainly) from the belly and when you are talking thickness removal you only need to remove 1/8th of the total thickness to halve the draw weight. When you tiller one of these you are removing wood from the sides. To drop the draw weight by half you would need to remove half of the bows width!
So you won't see 'normal' changes in tiller with wood removal from the sides - it's pretty subtle hence why you need to be pretty much perfect pre-glueup.

[fujimo]

holeee Robin- you had me thinking that was quick    
 got any pics

[robin]

https://goo.gl/photos/Cjbbq54qpipqCGEr5

[robin]

Finally go the bow on a bow string hugging the belly lams as Roy suggested. Worked on it more ....first it was the left limbs bending more just pass the fades as the left limb had more reflex and this causes just passed the fades to bend more. Once I had the left limbs worked out. Started to work on the right as just passed the fades to the tips wasn't bending much at all.

Well, finally all worked out well tillers get to brace at 5" the limbs differences are 1/8. Will keep all posted till I reach 19"......keep tune

[Roy from Pa]

Looks ok, brace it to 6" and continue.. The shorter the string gets, the more stress is applied to the outer third of the limbs.

[robin]

https://goo.gl/photos/7VmVeV8ssU1LjerN7

 https://goo.gl/photos/meowAppVdcXG8QVn8

Worked on the cut in shelf on riser and the try to string it again and it broke.

[robin]

Roy, I sent you a PM. Pls check...rob

[Nezwin]

Originally posted by robin:
Boo back 4mm and taper to 2.5mm
Core is balau wood 4mm tapers to 2.5mm
13.5 inch long and one inch thick handle
Boo Belly (heat tempered 4mm taper to 2.5 mm

Have you used Balau successfully before? We get it here in Australia and I haven't considered it. Short grain-structure and (relatively) low Mod. Crushing for it's stiffness, didn't think it would make a good bow wood.

How wide was the bow at the fades? Too narrow and the 'boo would've overpowered the Balau?

[robin]

Ihave had success using this balau before. This is boo back and boo belly. Balau os used for the core, thus dont think it will be compressed in middle

bow is 33 mm at the fades. What bow do u built?