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Overweight tiller best approach?
Del the cat:
--- Quote from: stuckinthemud on October 11, 2022, 06:37:31 pm ---The alternative is to thin the sapwood but I have been caught out by doing this as if it goes wrong you have to start all over on another ring and it is very easy to end up going too far and lose too much weight. In this case the sapwood is relatively thin at one point and I am not at all certain reducing the sapwood is a good idea in case I go through to the heartwood at that place. What is the minimum ratio of sapwood to heartwood before performance is affected? Is 30:70 sapwood to heartwood too much sapwood for example?
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30:70 is fine.... 50:50 is ok
As long as you have some heartwood maybe as little as 4-5mm, just gotta work with what you have.
Reducing sapwood can be tricky as the heartwood underneath won't always be an even layer, it can swell up especially where there are undulations. Also depends on the curvature of the log, the heartwood may be cowned up under the sapwood.
If you saw the stave into 6" sections you can see exactly where the heartwood sapwood boundary is ;) :o >:D O:)
Del
BTW, you don't need to follow a ring, yes it's pretty, but not necessary.
ssrhythm:
You probably know this, but I’ m going to post it anyway just in case. If you are that heavy, you likely don’t have a string on it, and no matter how short your tillering string is, it’s going to show you a weight greater than what it actually is.! The more slack in that tillering string, the more stack you’ll encounter more quickly as you bend the bow, and the greater the poundage will read above what the actual poundage is. Again, I know you probably know that, but I hate assuming anything, and I overshot the wood reduction and ended up with some surprisingly low poundage bows at first stringing on my first few attempts because I overlooked this concept. Otherwise, wise advice above; go slow and get a string on it as soon as possible.
Badger:
--- Quote from: ssrhythm on October 13, 2022, 11:25:18 am ---You probably know this, but I’ m going to post it anyway just in case. If you are that heavy, you likely don’t have a string on it, and no matter how short your tillering string is, it’s going to show you a weight greater than what it actually is.! The more slack in that tillering string, the more stack you’ll encounter more quickly as you bend the bow, and the greater the poundage will read above what the actual poundage is. Again, I know you probably know that, but I hate assuming anything, and I overshot the wood reduction and ended up with some surprisingly low poundage bows at first stringing on my first few attempts because I overlooked this concept. Otherwise, wise advice above; go slow and get a string on it as soon as possible.
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You know for the past 15 years or so I have been using the long string to gage the weight of my bows as I build. I have done this on hundreds of bows not just a few. If the string is hanging loose somewhere between 1" and 9" It will read surprisingly close to the actual draw weight if it were braced. I normally brace a bow when it reads target weight at about 23 or 24 inches for a 28" draw bow. It doesn't seem to matter the style of the bow. I usually take it to this weight with a well-controlled draw knife but will use a scraper or rasp on occasion. Once it is braced, I use only a scraper and I never think of myself as reducing weight, I like to think I am just perfecting the tiller and when it hits its target weight, I just no longer have any more room to perfect tiller.
stuckinthemud:
I keep my long string quite tight to the stave, hanging down so it starts pulling the tips at about 3” string movement. I have found it’s a pretty good indicator of draw weight but when I started in this craft I used a very slack string which was far from accurate
George Tsoukalas:
i use a string that is about 9 or 10" more than the stave. I don't remember exactly. I look for a good bend at 10" and about 5 # over the draw weight I want. This puts me at 15# or so over my potential draw weight. Plenty of room for tillering.
Stringing a bow that is more than 20# over potential draw weight is not a good idea.
I could go on about how I "sneak up" on tiller but ...
Jawge
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