Can set predict when a bow will fail?

[Matt S.]

I've tried searching but haven't found anything concerning this question: while tillering, can you get a decent indication of how much more a bow can take before failure based on set?

For example, I'm currently working on Red Oak longbow that is very similar to the "Yew Longbow" in TBB1 in tiller and dimensions. I am hoping to make my first "lite" warbow, so going for a 32" draw length.
So far, I've been closely monitoring set (and weight, but my bows always seem to come in at least 4 ounces heavy) to determine if the draw weight is safe for the bow, so I would pull it on the tillering tree to, say, 55# (while making sure the tiller was still good). After pulling it to 55# numerous times, I'd remove the string and measure set. If set is low, I'd repeat the process but pull it to 60#, etc.

So here I am,  the bow is currently pulling ~70# at 28" and ~75# at 30". Current just-unbraced string follow is right at 7/8 to 1". I consider 1 1/2" set to be acceptable.

Do you think I can use the set to determine if it is safe to continue pulling the bow towards 32" or is set an unreliable indicator of how much more a bow limb can take? I'm sort of nervous because this is the heaviest bow I've ever attempted, plus I usually only tiller for a 28-29" draw.

Thanks for any advice!

[DEllis]

Set is an indicator of when a bow will fail, but it varies depending on the type of wood(juniper will accept very little set before breaking, hickory much more for example) and the degree of reflex or deflex you started with as well as the particulars of the individual peice you are working on(crown, density, fibre violation etc.) So it is usefull but only as far as your experience with similar circumstance goes. I consider anything under 1.5 inches as good but it may not be safe if the back is violated or weaker for any reason. Not much help I guess
Best of luck,
Darcy

[Matt S.]

Darcy, that's sound advice.
This particular bow is from a board (1x2x6) with a fairly good back. Not sure how much Red Oak will show in set before giving up, but I do have a couple of RO board bows with nearly 2" set. I suppose a lot does depend on the condition of the back fibers.

I guess I just want the easy way out and have somebody tell me to either "go for it" or "don't push it"  I don't want the bow to break, but I also want the heaviest weight possible out of this board - the suspense is killing me!

[George Tsoukalas]

I don't think so. Only if the belly is chrysalled along with the set. Jawge

[mullet]

 I think "set" has helped to keep your bow from failing.

[sailordad]

im with George and Eddie on this

[denny]

MY two cents.! Let me say this , The longer the bow , I have found less set. However like what has been said wood and dimensions come into play, especially shaping a "d{" style bow. I would be more concerned about chrysalis than string follow. My 1 to 3 inches is not uncommon , I would think for such a long bow.Red oak is somewhat brittle for a warbow, I have found,but with a good backing I would give it a go. I like white oak, it seems better for me. But ash is awesome for warbows in my opinion.When I try to duplicate a old style bow I shop for all kinds of answers before I attempt the project, there by eliminating less doubt.But it sounds like you have a handle on things. If concerned about breakage , put it on a tillering tree and stand back and tester her. Also when I am in doubt I never pull the bow full draw , before i break the bow in training the grain. I am talking maybe 50 to 100 arrows and recheck the till. Then I would give that first full draw for 1 to 7 seconds and let her fly. String follow is the bow training the grain. Good Luck and be careful Denny

[Matt S.]

Well, I decided to call it finished and leave it at its 30" max draw. It's almost 80# at 30" and that's about all care to pull it on the tree - because my arms get tired repeatedly pulling that weight!
It will probably lose a couple of pounds after I get done sanding it, but that's fine. I still can't draw it past 25" anyway. This bow was a multitude of experiments for me, but I've grown to really like the way it's come out, so I don't want to risk breaking it! I've learned a lot from this bugger (and had a close call earlier in its construction )

I'll make a new post in about a week when all the finishing work is done.

[crooketarrow]

    First off set is damaged wood sells from over stressed wood. So if your getting set your doing something wrong. Meaning if your wood is well seasoned. Then you have to make yours limbs a little wider or longer or both. White wood has good compression and d bows use that compression the very well. Old war bows were made of whitewood ash mainly. Good cheap wood for army bowyers to surply the army with. Sence your useing the right design Your D's arn't big enough or the limbs are to short. BEEF UP AND ADD A COUPLE INCHS. Untill you find out what you can get away with at the poundage you want.
  I've built 2 war bows 102 #'s and 96 #'s with less than and 1 inch and a 1 1/8 of set. And once saw at a shoot a 126 pound elm that had a little reflex in it. I never heard of and don't beleive you can get 100 pounds not set with a board bow. Remember real war bows did'nt have any backing. But I don't know I 've never built a board bow before. Good luck.

[George Tsoukalas]

Set happens. jawge

[Matt S.]

    First off set is damaged wood sells from over stressed wood. So if your getting set your doing something wrong. Meaning if your wood is well seasoned. Then you have to make yours limbs a little wider or longer or both. White wood has good compression and d bows use that compression the very well. Old war bows were made of whitewood ash mainly. Good cheap wood for army bowyers to surply the army with. Sence your useing the right design Your D's arn't big enough or the limbs are to short. BEEF UP AND ADD A COUPLE INCHS. Untill you find out what you can get away with at the poundage you want.
  I've built 2 war bows 102 #'s and 96 #'s with less than and 1 inch and a 1 1/8 of set. And once saw at a shoot a 126 pound elm that had a little reflex in it. I never heard of and don't beleive you can get 100 pounds not set with a board bow. Remember real war bows did'nt have any backing. But I don't know I 've never built a board bow before. Good luck.

The overall amount of set with this bow is very good, by my standards. 1" or less is pretty good out of a highly strained red oak board bow IMHO. I think true war bows out of "better" wood and staves are in a completely different realm from by humble red oak boards.
Part of the intrigue that motivated me to make this bow was to see how far I could push a less-than-perfect 1x2x6 red oak board, I never truly thought it would be a "proper" war bow, but an attempt to see how close I could get with the limited materials I have to work with.

How do you like your two war bows? I wish I could draw a heavy bow like that but it ain't happening any time soon! I guess I now have a bow I can practice with

[George Tsoukalas]

Anything under 2 in is fine. IMHO. Jawge

[DEllis]

I think that long narrow bows of white woods will handle more strain than a lot of people give them credit for when they are made to bend through the handle.........there's a lot of working limb there.
Matt S. Almost 80# at 30 inches is great from an oak 1x2 "thumbs up" ........can't wait to see the pics.
Darcy

[Pappy]

Just curious,if you only pull 25 why are you tillering it out to 29/30. 
   Pappy

[Matt S.]

Just curious,if you only pull 25 why are you tillering it out to 29/30. 
   Pappy

My draw-to-the-mouth draw is 28" and I wanted to try a draw-to-the-ear shooting method with this bow. The reason I've only drawn it to 25" is because that's as far as I can draw it before my shoulder and arms say "no way, we aren't going any farther"