Primitive Archer
Main Discussion Area => Bows => Topic started by: islandpiper on September 30, 2008, 02:12:01 pm
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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
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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.
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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.
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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
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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
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If you are compulsive then I am obsessive...I scrape ten times and exercise it 30-50.
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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
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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.
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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
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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.
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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.
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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.
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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
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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.
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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
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AD, if you floor tiller a bow and then flip it around till you can't tell the difference when you flip it, it will be even when you brace it. If you are making a 50# bow you know what 50# bows allready feel like. I have gone from floor tiller to full draw on many occassions. Not saying it is bad cause I still do it also but if you have to excersize a limb to get the shape to settle in the bow even if you can't see it. There is a method of monitoring the condition of your wood, you can excersize it as little or as much as you want and it should not have any affect either way. I can explain it further if you like, it's very simple.
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I'm another one of those that don't exercise the limbs to any great extent during the building process. As Paul Comstock wrote in his book "The Bent Stick", good tapering produces good tillering. Achieve good tapering right off the bat and and there will be no hinges, flat/high spots to deal with. With only weight reduction to worry about I can bring a bow in rather quick and most times on weight. -ART B
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Hmmmm... I think I'll still use my tiller tree, and exercise the limbs between scrapes. I'm in no hurry. Maybe I'll give floor tillering a bit more thorough look. The thing for me with floor tillering is, I have a hard time seeing the limb bending. Do you guys stand in front of a mirror, or get someone else to watch while you flex the limbs?
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I exercise my limbs a little between the long and short string. When I am satisfied with the tiller at about 20" I start shooting a dozen arrows at less than a 20" draw between scrapings. I also end a tillering session for the day by leaving a bow strung for 3 or 4 hrs. My bows turn out pretty good so I guess I will keep doing what I have done in the past.
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I remove wood and exercise the bow with short pulls 20-30 times after each wood removal session. Easy does it. Gentle as a lamb. Just enough for the change to register. In my younger days I'd play catch up. Correct one limb. Work on the other only to have the original register its cahnge. I'm not sure I understand the rationale behind not exercising the bow between removal sessions. I'd rather have changes show up early on than later on. They're going to show up eventually. Jawge
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I do it about like Jawges ,Not as much if I am working with clean straight wood but I am
usually working with snaky ,knotty wood and if you don't work it ,sometimes you will get
a surprise you won't like. :( I do it slow and easy also out to where I was in Draw before I
took off wood,if all looks good I gradually go another inch or so,I keep this up till I get to full
draw never going over the weight I am looking for. I also do like David,I tiller in short sessions
usually out to 10 or 12 inches then give it a break then to about 20 and then full draw. :)
Pappy
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I wonder if there is a room big enough, or a bar long enough, to allow all of us to sit down and trade all these good ideas (as different as they are) face to face. Now, wouldn't that be an adventure. Everybody showing off all their bows and tools and ideas. Well, till then, we'll have to settle for pecking these keys and trading ideas.
piper
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I wonder if there is a room big enough, or a bar long enough, to allow all of us to sit down and trade all these good ideas (as different as they are) face to face. Now, wouldn't that be an adventure. Everybody showing off all their bows and tools and ideas. Well, till then, we'll have to settle for pecking these keys and trading ideas.
piper
Actually I do believe badger plans on opening a bowyers coffe shop when he retires :)
Fascinating how people do things so differently
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As long as Badger has Dietrich's Paradiso in a k cup, I'm there ! Jawge
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Jawge, if I get this coffee shop put together like I plan I will fly you our here for the grand opening and give you a free cup of Deitricks Paradiso! But I would probably put you to work with newbes once you got here so it may not be as good of a deal as it sounds, LOL.
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Further to what has been written, I like to sweat a bow by leaving it braced, versus using the tillering tree and only after I feel like the tiller is pretty much done. Also like Eric I want to work the bow more by shooting than by using the tree. While we describe what we do differently, I bet we all do pretty much similar things. Trial and error has a tendancy to shake out the riff-raff ideas and techniques and leave the effective stuff.
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For now I will stick with the 'scrape a little, excercise a lot' school of bowmaking. I am a poor judge of floor tillering since I am still fairly new at this, only about 30 or so bows under my belt. I can certainly see aiming for the 'floor tiller to full draw' method, though. Lignin fibers fail after a certain about of flexing, and just how much flexing they will take in their life is beyond my ability to foresee...ergo, excercising could lead to earlier failure or less efficiency.
I'd be willing to bet a good 50% of my time in making any bow is taken up with head scratching and staring at the wood, either on the bench or on the tillering tree. Maybe someday I will be able to speed up the process and crank bows out in no time at all...but that may ruin some of the wonderous mystery I feel in the wood.
Looking forward to seeing all of you at the bowyer's coffee bar, I'll be the one drinking the Full Draw Espresso.
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As long as the tiller on a bow is good it certainly won't hurt the bow to excersize it. Idealy it won't make any difference. If you check the poundage on your bow at a certain benchmark say 20" before excersizing and then check it again at the same benchmark after exercizing you want it to read the same. If it reads the same the excersize likely did no harm. When I am going for a high performance bow I watch the weight at my benchmarks like a hawk and let that determine how I tiller the bow as far as how much working limb I use and how close to the handle I get it bending. Steve
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badger, I would love for you to explain your technique further please. You can PM me if nobody else is interested. I love to see the way other bowyers differ in the method they use, because I like to experiment to improve performance especially in the archer (me). Someone may have a better or easier way to achieve the same performance. In my case I have used both exercizing limbs alot, and exercizing as little as possible IMO it comes down to the confidence you have in the quality of the stave and the imperfections in the wood. richard
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So I am looking back over some old threads to see if folks have changed their thinking about exercising while tillering and found this and other interesting comments.
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.
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Waiting for Weylin to weigh in on this question- I think I remember from either a previous post here, or maybe YouTube, that he had a different opinion on this question. As DanaM said, “Fascinating how people do things so differently.”
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I floor tillered and strung my 50# record bow. Adjusted the tiller at brace and worked on it till I liked the bend at about 20-24” . Not necessarily exercising that much. This was before I started using a tillering tree. Bow #225. In December I started using the tiller tree. I am at about 20 bows using the tree. I am liking the tree but it’s not a must. At 275 bows I like both ways. Still learning from using the tree. I noticed if you center the bow on the tree and center the pulling point with the scale pulling straight down . The scale hanging point will follow the stiff limb spots moving away from a straight line from center of bow drawn straight down. Not a good explanation of the bows response but best I can do. Does not show up so much on a 67” bow but wow how it magnifies a 42” crossbow . Here is a pic of my tree. Maybe you can figure out what I am trying to explain. Arvin
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The scale hanging point will follow the stiff limb spots moving away from a straight line from center of bow drawn straight down. Not a good explanation of the bows response but best I can do. Does not show up so much on a 67” bow but wow how it magnifies a 42” crossbow . Here is a pic of my tree. Maybe you can figure out what I am trying to explain. Arvin
Arvin,
I think I follow what you are saying.
if you have to slide the scale to one side or the other to keep the bow level when you draw, it will move towards the stiff limb?
275 :OK
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Yes, your tillering string will slide towards the strong limb. Jawge
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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
+1... nicely explained.
That's why it's easy to overshoot and take off too much wood... because the effect doesn't show up immediately.
Del
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I mentioned in an earlier post that I shoot the bow at a short draw, less than 20" as I get to that point on my tillering tree. Before I started doing this I would take what a nicely tillered bow out for it's first shots and something would drastically change, usually one limb would go weak.
Just my unproven conclusion but I believe the snap of an arrow leaving the bow registers a change must better than simply pulling the bow on a tillering tree. By seeing a slight change early on you can head it off at the pass before it can become a major problem down the road.
I still see slight tillering changes during the initial shoot-in, sometimes almost none, sometimes troublesome, it all depends on the quality of the bow wood you use.
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I mentioned in an earlier post that I shoot the bow at a short draw, less than 20" as I get to that point on my tillering tree. Before I started doing this I would take what a nicely tillered bow out for it's first shots and something would drastically change, usually one limb would go weak.
How many shots do you think are necessary for this to give full effect?
Mark
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I shoot a dozen or so but not with every scraping, I pull the bow on a tree 20 or so times between normal scrapings and gizmo checks. When my gizmo lines are getting really short or after 4 or 5 scraping sessions I shoot a dozen or so arrows and recheck with my gizmo to see if anything changed.
As I get closer to finished tiller I shoot more and more arrows and exercise the bow on the tree less, still at short draw.
I don't have a set pattern for any bow exercising, just what comes to mind at the moment.
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I didnt read everything,,
I start shooting the bow at 20 inches,, and pull on the tiller tree to look at the bend
and I leave it braced for several hours a day as I tiller
that seems to work ok for me,,
I went back and read some,, Steve to you its simple,,, ;D
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How about it, Simson? What's your thinking on this subject?
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I went back and read some,, Steve to you its simple,,, ;D
Brad,
I have tried Steves no-set/benchmark method a couple of different ways. For me, holding a particular draw length at the same time as letting a bouncing scale settle was not the easiest. I think my biggest problem was making sure I was exactly on the desired drawlength mark.
I now keep an actual weight on a bench at the foot of the tillertree. when I want to check a benchmark, I can hang the weight on the string and measure to the 1/8" to see drawlength increases easier.
Needless to say. I use Badgers no set principle on every bow I have made since I first tried it.