Overweight tiller best approach?

[stuckinthemud]

Ok, so I am tillering a yew hunting bow. I’m going for an arc of circle bend through handle round belly/fat galleon design.  The tips are both twisted for the last 3” but the bow itself has no twist. It’s 64” ttt  with a bit of character but not as much as I usually deal with so I find myself with a bow that has a sweet bend but is double the target draw weight.  It is 80lb at 16”, but I am aiming for 60@29.  When you are in this situation, what approach do you find works best?

[Pappy]

If it looks good, just good even strokes off both limbs, a little at a time , checking as I go, and don't get in a hurry, things can happen pretty quick sometimes, I love it when all looks good and just need to remove weight,that's a good spot to be in.
 Pappy

[George Tsoukalas]

What Pappy said for sure.

I don't have a lot of experience with yew though I have made a few yew bows.

Your stave is about 62" and not pristine.

I am wondering if drawing it 29" even if it bends in the handle might be a reach.

Perhaps a rawhide backing would help?

Jawge

[bradsmith2010]

same,, I just remove wood slowly and keep the tiller even as possible,,no need to draw it to 80,, if you aiming for 60..
its about 60 at 12,,,
some even suggest not stringing it to you get a bit closer to target weight,, estimating the draw wieght with long string,,

[superdav95]

Like others have said here I would do even scrapes till you get closer to your draw target.  I make it a point not to ever surpass my draw weight during tiller.  I also stop an inch short of my full draw length target and finish the bow up and shoot it.  It usually gets me pretty close to my target at intended full draw finished and sealed bow.  With yew a little sanding and scrapes go a long way in my experience.  Burnish with burnishing rod or piece of porcelain or something smooth when done sanding the bow to get it really shiny and smooth.  Best of luck. 

[BowEd]

Good sound advice by others here.Hav'nt made many yew bows but I'd be patient and sneak up on it myself.
I generally start out from brace a little closer to my final draw weight though.
I really don't see why you pulled it to 80#'s if you wanted 60#'s.You should be ok yet hopefully because it was only to 16".
Removing even amounts or counting strokes from each limb.Stay away from the hee haw syndrome of overly positive and negative tiller showing if you can.That means a little at a time.Exercize it properly between wood removal.Check amount of draw weight loss from removal at same draw length previously checked.Good place to be though with it already bending evenly.

[stuckinthemud]

I'm used to wrestling really "characterful" staves to brace height, to do that usually means finding the place where a hinge (or hinges) is going to be and smoothing the rest of the stave down to the same level before the weak points become a problem. I am so used to pulling it an inch, finding the weak points, correcting then pulling 2 inches and repeating until the stave is bending nice and even. Often weak points don't appear until the bow is bending a good few inches and the stresses have all evened out.  For me, this is a really good stave (two or three knots and a bit of twist and a bit of sideways correcting is a good stave !), and this stave ended up overweight by a long way. Its only the second or third time this has happened and it kinda freaks me out.  Why bend it?  So I can find and correct any weak points before they become a problem.  They were there, they got corrected, but no-where near as bad as I am used to and now I am a long way overweight.  The stave came with a bit of reflex where I could fit my little finger under the handle rubbing the bow and the bench, the reflex is still exactly the same, so no set yet, and the 16" draw on my stretchy long string is more or less brace height.

[Del the cat]

Its one of the fundamental questions... how much wood to remove to drop a certain poundage.
It's down to experience... but to drop 20-30# requires a fairly enthusiastic rasping along the belly of each limb.
I tend to follow the mantra of "remove half as much as you think you need... then check the tiller".
Of course you have to take it off proportionally... less off as you move towards the tips (e.g 1mm off a 23mm thickness near the grip, has less effect that 1mm off a 10mm tip)
Del

[stuckinthemud]

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?

[superdav95]

I wouldn’t recommend taking down any of the sapwood.  I know others do it but the rings on yew is often very thin and can be a challenge to get to a single ring.  It may not be a deal breaker to violate a ring with yew I don’t like to do it if it can be helped.  1/4” sapwood is sort of the standard but wood is wood.  If you e got thick sapwood maybe consider a narrower limb design to get more heartwood to sapwood ratio.  I don’t think I would even make a wider limbed recurve type bow with yew that had real thick sapwood.  I think you’d be fine with a ratio of 30/70 like you say generally.  I’ve got a yew bow I’m doing now that has some character and the sapwood is thicker on one side of the limb then the other.  Wood is wood and we just have to roll with it and make the best bow we can with it.  I certainly wouldn’t violate a ring to even sapwood out imho.   Best of luck. 

[Del the cat]

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?

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   
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]

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.

 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