I have read and seen where people have after make a new selfbow from a stave, would string it and let it set for hours strung before finsihing the bow. What does this do and why is it done
When a bow is maybe 5 pounds overweight and cleaned up nicely with fine cabinet scrapers and 80 grit sandpaper, I like to leave it braced for several hours, often overnight, to settle the limbs. The bow will usually take some more set and often drop a pound from this. The bow is going to do this sooner or later from being braced and shooting. I prefer all of that to occur before the bow is finished, so I can be certain my hunting stints won't have any affect on it.
Some guys feel that duly exercising the limbs throughout construction and shooting in is enough, but this is an extra step that I feel makes for a more rock solid bow.
although I can't prove it, I suspect that there is similar, and less taxing, virtue in simply shooting, allowing bow to FULLY RELAX and repeating over the course of several days, checking tiller and weight after each shooting session. after 200-300 shots (in addition to the the workouts on tillering tree along the way) with no change in weight or tiller, I'm satisfied that it has settled permanently. in my humble experience, this has proven to be effective.
I don't recall any hunting situation(or other circumstance) where I needed a braced bow for 12 hours straight, and I do plenty of hunting. indeed, I would never leave a selbow braced for that length of time under any circumstance, particularly during its construction. bamboo backed bows would probably be able to take that without suffering needlessly, but I don't leave any bow that isn't laminated fiberglass braced unnecessarily. no good can come from it, only string follow.
the notion of tiller settling in permanently necessarily implies the assumption that the bow is designed properly for the materials being used, that those materials are properly dried prior to final tillering, the bow is tillered properly, that the bow is not ever subjected to overdrawing, and that it is finished(sealed) properly to protect the wood from radical changes in its moisture content for its entire life.
What Adam said but I never leave a stave or bow strung. I work with a rope and pulley. I exercise the stave between wood removal sessions so by the time the bow is done it is pretty well broken in. Jawge
I work my selfbows on the tiller tree as I remove wood and once I get to brace I will brace and let it sit for an hour. As tillering progresses I make the brace time longer up to as much as 6 hours.
When I'm hunting I brace my bow when I leave camp and unbrace it when I return. This is generally 4 to 6 hours so I want to be sure it can take it before I take it out.
Just before I apply finish to my bows I leave them strung 5 or 6 hours then recheck tiller. If everything checks out OK I slap the finish on them.
When a bow is close to weight and at full brace height, I leave it strung while I tiller. This is generally a fairly short period if I've done my job correctly thus far. But, I will leave them strung for a few hours before finishing to help them settle into the times when I am hunting or shooting for several hours at a time. I think it helps to make sure tiller won't change. It's a bummer to find that out after finishing it :)