Getting to full draw without losing thickness or gaining set?

[stuckinthemud]

I am copying a historic yew bow from Scandinavia. The thirteenth century original was compression wood and cold climate yew. My yew is less knotty stem-wood but mild climate and so much less dense.  I am currently on the mark for width and thickness and am starting to show signs of set as I get close to brace height. The original had a little more set than I am showing, but It was a working bow and I am only at brace height.  Any advice on how to get to full draw without increasing set and without loosing too much thickness?  Gizmo shows good even bend on both limbs

[Pat B]

As long as your tiller is even you can continue to pull the bow towards full draw.

[mmattockx]

I am copying a historic yew bow from Scandinavia. The thirteenth century original was compression wood and cold climate yew. My yew is less knotty stem-wood but mild climate and so much less dense.  I am currently on the mark for width and thickness and am starting to show signs of set as I get close to brace height. The original had a little more set than I am showing, but It was a working bow and I am only at brace height.  Any advice on how to get to full draw without increasing set and without loosing too much thickness?  Gizmo shows good even bend on both limbs

Getting to brace on a flat bow normally puts about 1/2 the strain on the limbs that you see at full draw, so you are going to pick up a bunch more set getting to full draw. There is no way to stop this aside from using a better piece of wood that will withstand the strain level of this bow. You have two options. You can either opt to keep the thickness and live with however much set you get or you can remove thickness from the limbs and minimize the set, at a cost to limb thickness and draw weight.

If you have a nice bend going on then you need to just reduce thickness evenly along both limbs to drop weight while keeping the good tiller.


Mark

[superdav95]

I agree with what has been said as well.  The other thing that could be done is to reduce width.  I know that this may ruffle some feathers but it is an option to help with reducing the amount of set.  I find that on a narrower bow limb that is slightly thicker will often take less set then wider thinner limbs.  Many factors come into play here but this has been my experience.  If all things being equal such as how well a bow has been tillered and laid out as far as design goes then generally I find that slightly narrower thicker limbs can take less set.  Now this opens up another conversation… does this always translate into better performance in the end?  The short answer is, Not always.  A little Set is not always a deal breaker as far as performance goes.  Minimizing set is the ideal for wood bows and some set is I believe inevitable.  Quality of wood such as density, mc, type/species, grain and ring quality all play a role among others in set as well.  Not trying to make a general statement here about width and thickness layout but it’s been my experience so far.  The game of controlling compression failures or even compromised belly seen or unseen is often overlooked I feel.  In tension strong woods such as hickory for example thinning too much on wider bow will likely show compression issues and or set.  Things can be done with hickory to limit this like heat treatment but still can be an issue.  Osage for example is obviously different then hickory.  It’s density is gonna be better for the most part depending on quality of Osage and such but is generally better in compression then hickory.  This dose t mean that compression issues won’t surface on an Osage build but one could get away with a little more on a good piece of Osage.  Anyway I’m rambling on here but I hope my point I’m trying to make is that sometimes narrower thicker can translate into less set and sometimes better performance if done well.  Hopefully this is not too general of a statement in this context but gives you something to consider when doing your build.    Cheers. 

[stuckinthemud]

I don’t have any margin for thickness but I did factor in 10 percent extra width to compensate for the difference in density, I think cutting out that extra material makes a lot of sense

[Hamish]

Did you add any heated in reflex prior to tillering? If not, do so, then let it rest for a week before continuing tillering.

[stuckinthemud]

Not done any tempering on this as I have lost a couple of yew bows that blew for no reason and some of the more experienced forum members have suggested this can happen with heat treated yew, also, the original probably wasn’t heat treated and I’d like to stay “correct “ if at all possible

[RyanY]

I agree with what has been said as well.  The other thing that could be done is to reduce width.  I know that this may ruffle some feathers but it is an option to help with reducing the amount of set.  I find that on a narrower bow limb that is slightly thicker will often take less set then wider thinner limbs.  Many factors come into play here but this has been my experience.  If all things being equal such as how well a bow has been tillered and laid out as far as design goes then generally I find that slightly narrower thicker limbs can take less set.  Now this opens up another conversation… does this always translate into better performance in the end?  The short answer is, Not always.  A little Set is not always a deal breaker as far as performance goes.  Minimizing set is the ideal for wood bows and some set is I believe inevitable.  Quality of wood such as density, mc, type/species, grain and ring quality all play a role among others in set as well.  Not trying to make a general statement here about width and thickness layout but it’s been my experience so far.  The game of controlling compression failures or even compromised belly seen or unseen is often overlooked I feel.  In tension strong woods such as hickory for example thinning too much on wider bow will likely show compression issues and or set.  Things can be done with hickory to limit this like heat treatment but still can be an issue.  Osage for example is obviously different then hickory.  It’s density is gonna be better for the most part depending on quality of Osage and such but is generally better in compression then hickory.  This dose t mean that compression issues won’t surface on an Osage build but one could get away with a little more on a good piece of Osage.  Anyway I’m rambling on here but I hope my point I’m trying to make is that sometimes narrower thicker can translate into less set and sometimes better performance if done well.  Hopefully this is not too general of a statement in this context but gives you something to consider when doing your build.    Cheers.

This is exactly counter to what we know about bending limbs. If thickness remains the same then the distance the belly has to compress remains the same. That distance is what determines the strain and therefore set. The width and draw weight has no bearing on this.

[superdav95]

I agree with what has been said as well.  The other thing that could be done is to reduce width.  I know that this may ruffle some feathers but it is an option to help with reducing the amount of set.  I find that on a narrower bow limb that is slightly thicker will often take less set then wider thinner limbs.  Many factors come into play here but this has been my experience.  If all things being equal such as how well a bow has been tillered and laid out as far as design goes then generally I find that slightly narrower thicker limbs can take less set.  Now this opens up another conversation… does this always translate into better performance in the end?  The short answer is, Not always.  A little Set is not always a deal breaker as far as performance goes.  Minimizing set is the ideal for wood bows and some set is I believe inevitable.  Quality of wood such as density, mc, type/species, grain and ring quality all play a role among others in set as well.  Not trying to make a general statement here about width and thickness layout but it’s been my experience so far.  The game of controlling compression failures or even compromised belly seen or unseen is often overlooked I feel.  In tension strong woods such as hickory for example thinning too much on wider bow will likely show compression issues and or set.  Things can be done with hickory to limit this like heat treatment but still can be an issue.  Osage for example is obviously different then hickory.  It’s density is gonna be better for the most part depending on quality of Osage and such but is generally better in compression then hickory.  This dose t mean that compression issues won’t surface on an Osage build but one could get away with a little more on a good piece of Osage.  Anyway I’m rambling on here but I hope my point I’m trying to make is that sometimes narrower thicker can translate into less set and sometimes better performance if done well.  Hopefully this is not too general of a statement in this context but gives you something to consider when doing your build.    Cheers.

This is exactly counter to what we know about bending limbs. If thickness remains the same then the distance the belly has to compress remains the same. That distance is what determines the strain and therefore set. The width and draw weight has no bearing on this.

Ryan.  I think I understand what you are saying… what I think I’m trying to say is that compression is increased and often less set has been observed in my experience depending on layout and wood species.  Not a hard fast rule for all woods obviously.  Narrow and thicker in some cases with certain woods while wider thinner limbs with other type woods where best suited.  Doubling the thickness generally increases strength 8-10 times while doubling width is around 2 times increase and also increases more in weight.  It’s a fine balance to achieve the narrowest lightest bow design that best suits the draw length and weight that is wanted in final bow.  Not to mention the right bow wood material for the particular design.  I believe this yields a bow that gives great performance and the least amount of set based on my experience so far.  If a yew wood bow is designed too thin and wide it may take more set then wanted.  If an ash wood bow is made too narrow and thick we may see compression issues and some resulting set.    Generally thinner wider limbs for most white woods and longer and narrower for yew and junipers.  With some exceptions.  Heat treating throws a twist into the mix for some white woods and I’ve found that they can be treated nearly like quality Osage wood if thoroughly heat treated and of good density. Not a hard fast rule obviously as there are lots of other factors.  Osage is good in tension and compression and can benefit from the narrowest bow limb design allowable for target draw and weight but can also make a great slightly wider thinner limbed shorter recurve bow layout.  Again depending on the quality of wood and ring thickness ect.   Hope this makes better sense.  Cheers.  Dave.

[stuckinthemud]

I have found I can tune a bow by reducing width, I certainly have been able to increase draw length by reducing width, but I’ve only done this for small adjustments - a few inches draw length - but this might need a bit more than that. Still got to be the best place to start

[Aksel]

May I ask which bow you´re copying?

[RyanY]

Dave, I think the issue is that changing the design parameters doesn’t change the properties of the wood including how far it can compress or stretch. While I can’t discount your anecdotal experience, it doesn’t make sense with what we know about bending physics and doesn’t match my experience.

[willie]

depending on layout and wood species.

ok maybe if it was longer......... or osage.....

but comparing apples to apples, or in the case of the bow being discussed, hoping to maintain thickness while bending further without taking additional set is unrealistic

that said, stuck needs to decide if the bow needs to be a replica with exact limb thickness dimensions or a shooter, which tillering without set, calls for slightly thinner limb.
If going for a shooter, the reduction in thickness is not all that much

[stuckinthemud]

So much of this game is psychological.  I cleaned up the side profiles and lost a couple of mm width but then I rolled over the corners which will also have removed a fraction off back and belly along the length of the bow. The extra step seemed to reset me as well so had a productive hour or two without adding to the set, though I also didn’t add to the draw length either…

[superdav95]

Dave, I think the issue is that changing the design parameters doesn’t change the properties of the wood including how far it can compress or stretch. While I can’t discount your anecdotal experience, it doesn’t make sense with what we know about bending physics and doesn’t match my experience.

Ryan.  That’s fair.  I’m not trying to convince anyone or suggesting that my thinking on this is the only way or right way to go about it.  My findings may indeed be filled with many other factors that have contributed to what I’ve seen too.  I did not conduct any scientific studies or controlled studies on this finding or opinion and I merely mentioned it reluctantly here as a consideration for stuck. I was aware it may go against the grain.   Agree to disagree may be the way to end this debate for now until I can have some solid tests to satisfactorily prove my opinion.  I’m open to new ideas especially when it comes to making bows.    I acknowledge that I may be wrong on this point according to the current data out there available to us as well as the experience of others.  I’m open to that.  I’m ready and willing to absorb new information and ideas about building bows. That’s the fun of it.   Some things we thought were constants and fixed may not be so fixed tomorrow or in the days ahead.    I meant no harm by giving my opinion and hope none is offended.  Cheers.