Tiller before hickory backing?

[Red Dwarf]

I am about to start on an elm flatbow (from a board) with a hickory backing but have never tried a backed bow before.
At what stage do I apply the backing, and what prep work should I do to the backing & board before glue-up?

Thanks

Red Dwarf

[Pat B]

RD, If you floor tiller both the belly and back before glue-up, glue them with about 3" of Perry Reflex you will have a nice even bend to your limbs when relaxed. Depending on the glue used, some prefer having a toothed or roughed up surface(Urac and other gap filling glues) and some prefer smooth surfaces(TiteBond glues). Be sure to degrease the gluing surfaces.
  With hickory backing, if you notice the belly wood getting thin and your targeted weight aways off, you can reduce the backing to reduce weight. I use a scraper to do this when needed.   Pat

[markinengland]

Red Dwarf,
I think it is a good idea to pre tiller your belly stave before glueing on the backing.
A hickory backing will add something like 10lbs of draw weight. EAch inch of glued in reflex will add something like 10lbs of draw weight. So for a 60lb bow you need a belly stave that is well tillered and that at low draw length (say 10 inches) pulls the same as a 30lbs bow at the same low draw length and then glue it into two inches of reflex. It doesn't matter if some of that relfex pulls out when takne out the form, or even if some set occurs. You'll get a bow somewhere pretty close to 60lb with a minimum of further wood removal. it is important to preshape the backing as close as you can to the final shape before glueing on. small changs to the edges or even sanding can remove a suprising amount of poundage and reflex on a bow once glued up.
Hope this helps,
Mark in England

[Red Dwarf]

I am looking for around 45# @ 26" out of this one.
By floor tillering the backing do you mean trimming the sides to profile rather than tapering the thickness?
I was planning on 1/8" for the backing thickness.
Can I use Titebond II for the glue-up?
I have a cawl with about 1 1/2 reflex and was hoping to use this.

What is Perry reflex?

Sorry for all of the questions, but when in doubt....


RD

[markinengland]

Red Dwarf,
I haven't tillered backings as such. All I do is cut the backing accurately to the bow shape and round the front face. This means that when it is glued on there is very little but cleaning up with a file and sandpaper to do so little tension is lost.
1/8th thick backing is OK.
All the Titebonds 1, 2 and 3 seem good enough for bow work.
I apply the glue and wrap with rubber strip and then just clamps the bow ahndle down and lift the tips onto wooden blocks to give the relfex. It works and is simple. You really don't need anything complex.
Perry Reflex is named after Dan Perry, a top flight archer who first "discovered" that a bow will perform better when a backing is glued on and allowed to set in reflex. The induced compression in the backing and tension in the belly mean that some work is needed to bring the bow back to straight. This has the effect of increrasing performance at reduced mass and reduced stress in the wood at full draw. It was Dan perry who gave me the advice I passed onto you. Perry Reflex is mentioned briefly in one of the Bowyers Bible volumes.
Mark in England

[Pat B]

Mark gave good advise!
  You have to shape the profile of the backing before you thin it or the tips will turn out too thick. This is primarily a cosmetic problem. 1/8" thickness at the crown at the fades is about right. By pre-tillering I mean taper the thickness of both the back and belly so they will bend evenly before glue up. Some backing thickness tapering is acceptable but you don't need much. The more evenly the components bend before glue up the better the limbs will bend after glue up.   Pat

[Red Dwarf]

Thanks Pat & Mark for the great advice.

I hope to be at the glue up stage later this week and will keep you posted.

Cheers

Red Dwarf

ps Where about in Blighty are you Mark?