Is Set At All Linear?

[mmattockx]

The question is if set comes on in a linear fashion or if it is very non-linear. I expect it is non-linear but would like to hear from those more experienced on this.

What I mean is do you see a little bit of set early on while tillering, then a bit more and a bit more as the draw length is increased while pulling to the target weight or is it nothing, nothing, nothing and then lots in a fairly short step?


Mark

[willie]

 Set with the birch I work with seems fairly linear, once I can detect it.
I would like to see it happen later in the tillering process, maybe just as you reach your drawlength goal or only a couple of inches before.

[Pat B]

If you are seeing set early on in the tillering process you are either overstressing the bow or it's not seasoned enough. Set is inevitable with wood bows but the degree of set is on the maker. 

[DC]

Usually I see it come on slowly but I have had it develop very quickly. I'm not sure if there is something else happening there. It's only been with backed bows but then that's about all I make. It could be a small hinge that I didn't notice and then I went too far and it just collapsed. I tried to blame the glue but that just doesn't hold water.

[PatM]

I had a bow that took minuscule set just from first brace and then it didn't add any more after being drawn 30 inches.  That doesn't seem linear.

[DC]

It sounds like the set follows your(everyone, not just Pat's ) tillering errors. If you make a tiny error early you will get a tiny bit of set early. If you don't make any more errors, no more set. In my case, I probably made a relatively large error and paid the price.

[willie]

Usually I see it come on slowly but I have had it develop very quickly. I'm not sure if there is something else happening there. It's only been with backed bows but then that's about all I make. It could be a small hinge that I didn't notice and then I went too far and it just collapsed. I tried to blame the glue but that just doesn't hold water.

I had a bow that took minuscule set just from first brace and then it didn't add any more after being drawn 30 inches.  That doesn't seem linear.

Just curious if either of these bows had heat bent wood or glued in reflex, in other words, what is called set might also be called pull-out

[DC]

Don't know for sure but most of my bows are boo backed and I don't think you get pull out with glued in reflex. Although I can see a freshly glued up reflexed bow equalising when you take it off the caul. It may not relax all the way and maybe the first pull or bend would equalise everything. Speculation. Kind of like when you take a car down off a jack. It sometimes sits a little high until you bounce it a bit.

[PatM]

The bow I was talking about was just s straight Maple flatbow.  It was dead straight when roughed out and was not heat treated at all.  I was anticipating linear set and thinking it would take about an inch but that was it after the first quarter.  It was wide though.

[Del the cat]

I think it is generally only apparent once you get to brace unless of course the tillering is out.
Sometimes it will only slowly creep in as the bow gets used.
I think it's not really going to happen when you are still removing wood in the early stages, as any stressed wood is tending to get removed as you progress.
It's the reason we exercise a bow on the tiller, the stress isn't effecting the wood immediately, but it may do with exercise and further stress.
The distribution of set along the limbs is all down to the tillering.
Del

[bownarra]

To get a better understanding of what is actually going on with set and why/where in the wood it is happening.
Make a quick test bow with good tiller, pull it too far and induce a good amount of set. Now take that bow and cut it in half on the edge to edge plane eg. separate the back and belly.
You will find the back goes back to its original profile and the belly goes into about double the set the bow was showing.
Woods that are known as being subpar often just need the back stressing appropriately.
It is an interesting experiment to try for yourself.

[mmattockx]

Set with the birch I work with seems fairly linear, once I can detect it.

I like the sound of that, much more than thinking it is going OK and then getting hit with a big change all at once.

If you are seeing set early on in the tillering process you are either overstressing the bow or it's not seasoned enough.

What would you define as 'early in the tillering process"?

It sounds like the set follows your(everyone, not just Pat's ) tillering errors.

I can see that. Since the question is about the behaviour of the wood only, I guess my question assumes a good tillering job with no bowyer induced errors or weak spots.

The distribution of set along the limbs is all down to the tillering.

This is a good follow up. Since it seems some set is pretty inevitable if you aren't Badger, what is considered a good or desirable distribution of set? All parts of the limb holding a smooth curve with the set evenly distributed?


Great answers so far, thanks to all for the replies.


Mark

[Badger]

Set with the birch I work with seems fairly linear, once I can detect it.

I like the sound of that, much more than thinking it is going OK and then getting hit with a big change all at once.

If you are seeing set early on in the tillering process you are either overstressing the bow or it's not seasoned enough.

What would you define as 'early in the tillering process"?

It sounds like the set follows your(everyone, not just Pat's ) tillering errors.

I can see that. Since the question is about the behaviour of the wood only, I guess my question assumes a good tillering job with no bowyer induced errors or weak spots.

The distribution of set along the limbs is all down to the tillering.

This is a good follow up. Since it seems some set is pretty inevitable if you aren't Badger, what is considered a good or desirable distribution of set? All parts of the limb holding a smooth curve with the set evenly distributed?


Great answers so far, thanks to all for the replies.


Mark

     I think that most set in linear. If it is not linear something else is going on such as maybe the wood reflexed itself a little while drying and some of that might have just pulled out early, it is still set. Some set causes hysteresis and other kinds of set not so much. The best way I have found to distinguish between the two types of set is to check the bow immediately after unbracing and then check again a few minutes later. If it hasn't changed the bow may not have much hysteresis from set but if the bow slowly returns to its original shape it likely is carrying more hysteresis.

[willie]

Woods that are known as being subpar often just need the back stressing appropriately.

Mike, would you consider woods like maple or birch to fall into the subpar category? I assume you are suggesting trapping the back would be the thing to do?

[bownarra]

I don't have enough experience with either of those woods as selfbows to really comment specifically on them. Yes trapping is one of the most underated techniques imo.