Exercising bow during tillering?

[islandpiper]

Can one (or several) of you more experienced guys explain this so an old farte might better understand?   Several times i have read that the limbs need to be flexed or exercised when tillering, between scrapings, etc.   Why is that?   How critical is it?   Does it vary with wood type and bow design?  Is six enough, twelve too many?  hmmmm   as usual, your expertise and varied opinions will be appreciated.   

Back to the bench.   piper

[adb]

Limbs need to be taught to bend. In order to do this, you need to flex them. Is this critical? YES!! Remove a bit of wood from the belly, exposing new cells, and then "crush" them as you flex the limbs, teaching them to bend. Watch for hinges and flat spots, and repeat. I work the limbs for 40-50 pulls between wood removal, going slow. if you rush, you'll probably break the bow. Never pull the limbs past final intended draw weight. Rinse, repeat. I do this for all types of wood.

[Fundin]

Otherwise you might end up like I did on my last bow. I had a perfectly tillered 63#@28" longbow. the outer end of the lower limb might have been a tad to stiff. After 100 shots, the exact spot that was stiff is developing int0o0 a hinge. Excersising is necessary to detect such a spot.

[Pat B]

In a lot of cases you won't notice any change in bend after removing wood. By exercising the wood between wood removals the wood will usually register the wood that was removed.
   This is probably what happened to your bow. You took enough wood to make the hinge but it didn't register until after you shot the bow 100 times. I believe it also helps reduce set and it eliminates most of the weight loss during the normal "break-in" period because you have taught the wood how to bend and how much bend is expected of it under normal use.  Pat

[sailordad]

i dont hink you can over excersize it,  my rule of thumb is 2 flex's per very one scrape,if i do a total of 50 scrapes on both limbs combined,i excesize it 100 times
thats just me,some say im compulsive

[stiknstring]

If you are  compulsive then I am obsessive...I scrape ten times and exercise it 30-50.

[Pat B]

I usually do about 20 to 30 exercise pulls for each time I remove wood and if everything is OK I gradually pull farther and farther  between wood removal and exercising until I hit the desired draw length.     Pat

[DCM]

For millenia men thought you had to hobble horses to "break" them to the saddle.  Then some smart fella put his head down, showed his shoulder to a horse and the horse accepted him as the herd leader.  Now folks don't hobble horses.

Similarly when I first started building bows I exercised the crap out of them after every adjustment.  Then a smart fella out in Oregon reckoned that was probably not necessarily the best plan.  Now I only bend a bow far enough to see a flaw, and as little as possible overall.  Similarly, I only work a bow for a relatively short tillering session, say an hour, then let it rest for half a day or more and come back to it.  Once I get the bow bending perfectly, at about 24" for 28" final draw, then I sweat it out to set the wood, by leaving it braced and shooting it.  Then establish the desired draw weight and adjust the tiller if necessary.  IMHO, I can get 5% or better improvement in cast using this approach, manifest in less set or string follow.

I'm not suggesting this is the preferred approach for a rookie, as intuition forged by experience, bad experiences in particular, are a necessary prerequisite for this technique, in my view.  But after a fella has made several dozen bows and feels confident, it is a desirable and natural evolution in my view.  In fact I think many bowyers follow this path, as they simply get to good tiller more quickly with less trial and error, and perhaps don't realize they haven't "worked" the bow as much.

[islandpiper]

Every time I learn something, I find out there are two more things to learn to back the first thing up.  I may be too lold to get started on this.   heh heh heh

piper

[JackCrafty]

Thanks DCM for posting that.

I thought I was an oddball for not exercising the bow during tillering.  I usually pull and hold, as opposed to pulling in rapid succession.  I think I pull my bows less than 100 times during tillering.

In my engineering classes, I learned about something called "fatigue failure": if a material is stressed enough times (even in small increments) it will eventually fail.  This concept has me worried that an exercised bow will be at middle age before it takes its first steps.

[adb]

When I'm exercising limbs between scrapes, I don't pull in rapid succession. I pull in slow even movements, going an inch or two more after several scraping sessions. Slow even pressure, not jerky.

[stiknstring]

When I am exercising the bow I usually pull it on the tree 10 to 20 times to get an idea what draw length I hit weight at.  Then I take a full length aluminum arrow and mark that length with a rubber band and proceed to shoot another 10 to twenty shots to finish the exercise session....i guess it might be more exercise for me than the bow but it seems to work well and my tiler seldom if ever changes when I reach full draw at my intended weight.

[Badger]

        I almost hate to post this as it goes against the grain a bit, very much inline with what DCM posted actually. When a bow is wide and thin it does take more to register scrapings and seems excersize is a bit more important. But I don't believe you have to teach a bow to bend, some bows would beak if not excersized but in these cases you are just breaking them down a bit. I commonly will build a bow simply by floor tillering till it feels about right then string it up and go shoot. I notice on my boo backed osage r/d bows I often need to excersize them more to "set" the tiller, but in these same cases the bow has usually broken down a bit more than I would have liked. When I am working a difficult stave I still find myself excerzing quite a bit but I have to be honest and say my best bows were not really excerzised much. Possibly a little risky but I like the results. Anytime drawing a bow changes anything about the way the bow bends or it's draw weight you are crushing wood cells. We have learned to accept a certain degree of this as being almost inevitable but it's really not neccessary, I am not good enough to bring in everybow with zero wood deformantion but it is possible if the demensions are good and the bow was not overstressed durring tillering. When you finish a bow that has basicaly no memory of ever having been bent the results will amaze you. You may not accomplish that all the time but the closer you get the better. Steve

[adb]

Steve,
So, let me get this straight... you can floor tiller a bow 'til it "feels" about right, string it, and go shoot? How? How do you arrive at draw weight? or length? How do you see tiller? or hinges? or flat spots? How can you have a viable bow, without teaching it to bend? Am I missing something? Seems pretty far fetched to me. No offense.

[Rich Saffold]

I never have exercised my bows either for just the reasons Badger and DCM elaborated on...Hell I rarely use a tiller tree unless I'm tutoring newbies since its another way to accidentally crush belly cells and end up with a mediocre bow..I have been floor tillering and stringing bows for many years. This is all the exercise a bow needs..

You get a real good floor tiller, the hard part is done..Most don't properly learn this first and most important step..

Rich