Primitive Archer
Main Discussion Area => Bows => Topic started by: stuckinthemud on September 12, 2015, 06:16:44 am
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Hi All,
Everything I have learned about 'set' has been by lurking on PA and trying to work out what more experienced bowyers already know about it. Anyway, I figure that just plain old asking is better than guessing, so:
1. What is set? I guess its where a bow takes on a small, permanent curve along its whole length??
2. What causes it - is there more than one cause?
3. Is it a bad thing?
4. Can/should set be heat-treated out of a bow? If so, at what stage in the build?
5. Any additional words of wisdom ?
Thanks for your time :D :D
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All I'd say is would you rather have set or chrysals or a smashed bow?
I'd rather have a bit of set....
I hate chrysals with a passion only normally reserved for telecoms companies ;D
Del
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Set is the result, generally due to belly compression/compaction, of a bow’s inability to return to its original shape. For instance, if a bow was constructed from a bow stave with 3” of reflex and after tillering, shooting in, and unstringing, the bow then shows 1” of reflex, the bow is said to have taken 2” of set. It can be spread out over the entire limb, or localized in a smaller area.
What it's telling us is the wood is overstressed in the area the set occurs in. It can be due to pushing beyond the wood's ability to resist compression because of how it's designed.... too narrow, thick, short, etc. Or due to abuse.... like drawing it farther than it was designed to go. A bow can also take set because its moisture content was too high prior to flexing its limbs... or because it was drawn farther before a tiller correction was made. In other words... if there is a spot on a limb that is stiff and not flexing, the areas to either side will have to flex more to make up for it, and if they're not designed to be able to do so, set will result.
Even if everything is designed and tillered right, a bow can take excessive set if the wood wasn't seasoned properly. I've seen white woods like hickory, ash, and elm do this when improper care of staves caused the wood to degrade internally.
Is it a bad thing? Well, imo, it's a matter of degree. A wee little bit of set in an otherwise resilient and springy bow tells me I pushed the wood's limits just enough that it's not overbuilt. It will shoot fine and I'll be happy with it. More than a little, and I'm trying to understand why and may make some adjustments on the next one.
If I were going to heat treat, I'd do it before the set occurred... better as a preventative than a 'fix'.
Learn from set. Limb set should be viewed more as a mentor than an adversary. It simply points to where we could make improvements.
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^ well said
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Very well said...I just finished making a hickory-backed black walnut bow today and was shocked to see the amount of set it took. I realise now that the majority of black walnut bow designs that I saw prior to working the wood were very wide limbed. The bow I made was a thinner limbed long bow. That is most likely the reason it took so much set: bad design for the wood. Live and learn.
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Great analysis of your bow's situation Limbit.
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BTW. in answer to number 4.
Yes set can be heat treated out of a bow.
IMO Heat treating is best done when a bow at or near brace height.
It can re-vitalise an old bow, but it should be done with tiller improvements, else the same problems will just re-surface..
I've restored my first ever Yew English longbow which is over 40 years old and now shoots faster and further than ever!
Some woods like it better than others.
Del
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Dances with squirrels answered the question beautifully and Del added some good comments as well I feel.
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Some people (including myself) think that a bow with some set shoots smother than a bow with reflex. In my opinion once you get over about 2in of set you start to lose a lot of performance but anywhere in the 1-1.5 in range is good and a 1in or less is superb.
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I agree with you bow and arrow, 2" is not bad. I like my everyday shooters to be about straight when unbraced give or take about 1" either way.
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DWS, very nice post. Jawge
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Thanks DWS that makes things a lot clearer, also, thanks everyone else for the reassurance that my bows are not as badly set as I thought they were
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Wood fibers stretch and not every piece of wood is equal. Having said that ~ some bowyers say that their bows that have taken set shoot good. The way I see it if a bow takes a lot of set, I know it is stressed and often over stressed. It will never break. >:D
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I have built my bows for a long time knowing they wood take some set . Ending up with reflex -deflex.
This makes a smooth shooting bow . That been said the same bow design that does not take set makes for a faster shooting bow. I have only had a hand full that took no or very little set (meaning less than 1" ) that just means the tiller was perfect. The wood moisture content was perfect and the design was perfect. The deminishing mass was perfect. It's hard to make one perfect. All this coming from a unperfect Arvin. :-\
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I have heard a bow with set shoots smoother or better or something,, I have never found that to be true with the bows I made,,I think they both shoot well when tuned properly and have the right arrow,, :)
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No doubt Brad. But it does read nice doesn't it.
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I guess its where a bow takes on a small, permanent curve along its whole length??
if this describes your set, then you are straining the limb equally all along its length. much better than set just at the tips or just at midlimb. (presuming the bows designed to bend that way).
I like to trace the back profile on a piece of paper before first brace, and once some set becomes apparent during the tillering process, make a comparison to the tracing to confirm the set is actually occurring in the limb where the design calls for the most strain
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That's smart Willie. ;)
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There are actually two types of set. I call them hard set and soft set. If you unstring a bow after shooting and see it has some set and give it a little push backward and it goes back to its shape that would be soft set. If you push it backward and nothing happens I call it hard set. Hard set is better than soft set. 2" of hard set is not bad. I prefer 0 follow but have seen some very good shooting bows with 2" of string follow.
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I think there may be another kind of set, though it is not truly set like the other varieties spoken of. On backed bows with glued in reflex, some of the reflex can be lost as belly wood is removed. I think this is more a result of the bottom "beam" getting weaker and a new equilibrium point being reached versus actual change in the wood. (but I have not tested this and it couldmbe argued that the change in strain due to the change in strength is a change in the wood)
The closer the belly wood is to final shape when glued, the less of this type of set should be experienced.
Ken
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I think most people find the opposite true, that reflex often increases as belly wood is removed, no?
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I think most people find the opposite true, that reflex often increases as belly wood is removed, no?
+1
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With thin backings, I've seen that as well. As backings get thicker, the balance shifts. It is also affected by the initial thickness ratios of the two pieces compared to the final thickness ratio (but I have not done any experimenting). Trapping the back would also affect the final result. My real point was that glued in reflex affects apparent set but that it is hard to quantify and is not true set, the way most would interpret it.
Ken
PS - one obvious experiment is to make a reflexed bow and take it to final "tiller" without actually flexing it so that any change in reflex is experienced without any other form of set occuŕing. I guess a second bow woulld need to be made in parallel but it would be fully tillered. Then the 2 could be compared for final shape.