A how-to explode a recurve bow while tillering it

[dratera]

Try bracing it prematurely before getting tips bending, i think, was my mistake. Or, too thick in the outer limb part , where it exploded. Not sure really..  I think stress is really big just before the tips, when bracing a recurve low, right? Im starting another one, any tips and advice on tillering these things are greatly appreciated. And it is wych elm by the way

[bubbles]

Hmm, that straight line seperation a long the the back is interesting.  Could it have had too low MC?

[bubby]

When building a static i like to get it bending to about 18"-20" before putting in the recurves

[dratera]

Bubbles, that might be a reason. I gave it a quite thorough belly tempering, but weeks ago. Maybe too dry where i store it..

Bubby, yeah I think I will get it atleast half way tillerd before recurves now. Trying tillering it with recurves from floor tiller messed with my eyes

[Badger]

  How hard did you pull it?  The tips don't normally bend on a static recurve. It sounds like you just need to brush up on the procedure for floor tillering and knowing when to brace the bow. How many bows have you made so far?

[dratera]

I guess somewhere around 40-50 pounds, standing on a stringer when pulling it up. This was my 5th one, and first recurve. Was planning for working recurves but was thinking to thin them out last when i was getting closer to finished tillering,  to try to save them from pulling out too much. Youre right i def need to get better at floor tillering and such. Thanks for the input!

[dratera]

Question about string alignement : Just braced the new bow now,( no recurves/flipping yet) and see that string is way off to the left. Its because both limbs leans sideways to the left. No dramatic snakey stuff going on, but just a gradually, slight horizontal bend to the side. Now ive read about people using dry heat and weights to correct it but where on the limb should i do it? Just pick a spot and bend both sides, or should i do the handle? 

[Badger]

  Usually guys now build a cawl and do the alignment and reflexing all at the same time heating the entire bow. If you do it in one spot it might cause problems

[Dances with squirrels]

Look it over real good, unstrung. Is it crooked unstrung, or is it straight, but then twists when braced? Where and how much of the limb I heat and correct depends on where and how much of it is out of line. Sometimes it's the whole limb, sometimes an isolated spot, sometimes I correct it in the handle. Let the bow tell you what it needs.

Also, double check your thickness across the limbs in several places. It's easy, especially as a relatively new bow maker, to make one side of the limb thinner than the other as work is done, and this causes limb twist as well. If so, get this right, and reassess, before making any heat corrections.

[dratera]

Thanks for helping me through this bow! It was crooked unstrung, thickness was ok, i think it was crooked because of warping when drying. I ended up correcting it several spots because it was already heat treated and i didnt dare pushing it too hard. Got alignement from off the handle to half an inch to the left of center , decided it was good enough. Finished it some days ago and im happy with it. Check this post if you want to have a look at how it turned out  http://www.primitivearcher.com/smf/index.php/topic,51972.15.html

[JW_Halverson]

This was an utterly useless post! I already know how to ruin good wood!!  Teach me how to NOT blow 'em up, please!!!   

I feel your pain, brother.  Nice looking hook in the limb, though, woulda been pretty sweet had it lived!  Nice to know you are still in the game and haven't fouled out or struck out!  Keep swinging!

[mikekeswick]

On recurved bows I do a lot of tillering by simply clamping the handle in the vice and then bending the tip by hand. Of course you need a good feel for when to brace but I can get them just about perfect without having to brace them to early.

[joachimM]

During tillering I often gradually shorten my slack string to one that's still longer than the final string (very taut at zero brace, 1" brace, 2" brace etc). Helps me to avoid the big leap from slack to braced 5-6".

Also remember: if you overheat the belly, you may actually also be affecting the properties of the back. Toasting lowers equilibrium moisture content in the wood. The point of toasting is to keep this limited to the belly. If it also affects the back (it doesn't need to really toast for this to happen), you also make the back stronger and more brittle at the same time. That's like having a bow with 5% MC where you expect it to be closer to 10%. see http://www.primitivearcher.com/smf/index.php/topic,51962.msg703559.html#msg703559

Joachim

[dratera]

Jw: thanks man, yeah i have gotten over it now  mike thats actually a good idea, but yeah guess one need some experience to do it right. Maybe doing it with an already finished recurve the same way would help develop the feel.

Joachim: yes thats how i usually do it too, but with this one, when i tried bracing it really low it kindof creeped back to zero brace right away, not sure how to describe it. I had 2 inch brace, but when i released pressure it straightened out and got super tight at zero brace, wasnt pulling down and in, just inwards toward handle. Didnt like it so i tried to up the brace a bit and then , bam.

But i think what you are saying about the heating is spot on. I overdid it, too close and for too long with the heatgun, got several spots on the sides toasted aswell. I think that combined with mediocre tilleringskills made it go bang. And thanks for the link,  I will do a study on that one before next tempering session for sure