Overbuilt bows

[PEARL DRUMS]

Over built to me means 2-4" longer than the usual recipe for a given draw length. Other than that I don't change anything when I build an over built bow.

[PatM]

 For me it's adding a bit of width.

[meanewood]

Good question and I love the way it makes you think about how to get the most out of a stave.

A good historical example of bowyers trying to push the boundaries could be Bow X1-3 from the 'Mary Rose'.

That Elm bow has had the width of the outer limbs reduced dramatically, probably in an effort to reduce as much weight as possible in the areas where set is less likely to happen!

It's an extreme example of whip tillering and shows those guys were trying to get the best performance from the bow as possible.

[Jim Davis]

Is this going to turn into a "power lam" definition argument.  lol

 ... Overbuilding does tend to add in a certain amount of protection to overdrawing although doing so routinely ultimately means  you are just asking the bow to be an optimally designed bow relative to the materials.   It's no longer overbuilt then.

Exactly.

[leonwood]

Well I have the habit of making my bows quite wide from handle to mid limb and slimming my tips to the extreme sometimes... So I probably overbuild and underbuild my bows at the same time

[bjrogg]

Overbuilt to me means like Pearl and Jim Davis said. Most all of my early bows I consider overbuilt. I was looking for a successful bow and not pushing the limits. Some were tillered well and some not so much. The not so much ones took a bit of set but probably not nearly as much if they had been 2"or 4" shorter. They survived. As my tillering skills advanced I still  overbuilt bows but got all the limb moving. My profiles held much better. My bows were capable of being draw a bit further than my intended draw. I still believe I overbuild my bows a bit. I have started pushing the limits a bit more though. I'm still in a comfortable spot yet though. I think sometimes when we have a few extra inches of bow length to work with we maybe don't try to get everything working as well as we could possibly get it. I like what Badger once said. Something like, when you think the tiller is good and you need
More draw length. It's time to perfect the tiller. Don't just think of removing weight.
Bjrogg

[Badger]

      If I was a young bowyer just starting off and I was trying to unlock all of the secrets of building the perfect bow I think I would invest my energy into studying set and trying to identify one type of set from another. I am pretty sure that several types of set exist although I can't prove it or for that matter even positively identify it when I see it. Over compensating to the point of getting diminishing returns is how I would define over built.

     Here are some things to think about when a bow starts taking set. Has the back of the bow gotten compressed and we are simply uncompressing it or are we crushing belly cells. I suspect a lot of reflex we loose is often because the back of the bow is simply becoming uncompressed. The only way I have found to tell the difference is to actually start monitoring the efficiency of the bow in the very early stages ( say around 22" draw on a 28" draw bow) Any bow will loose weight if it takes set regardless of the reason but it will only loose efficiency if we are crushing belly cells. This requires taking force draw curves and shooting through a chrono until you become familiar with expected performances at various draw lengths.

      I started over building my bows 6 or 7 years ago and got much better results than when I was underbuilding them. I think about 2 years ago I may have started taking it just a tad too far and this year I am backing off a little but not much. I am hesitant to throw numbers out there because we all have different releases when we test so one guy might be thinking his bows are slower where in reality he may just be using more of a hunter or target shooters type release. But speaking only for myself I can say I have had a pretty dramatic increase when I started using more wood per the mass formula. I used to figure about 172 fps using a 10 grain arrow and 28" draw. When I went to more of a no set tillering technique 175 to 176 became more typical with 180 to 182 not being unusual. I didn't notice much of an increase in my boo backed bows but the gap between self bows and boo backed became much smaller.

     When I say overbuilt I am usually referring to starting wider at the fades. That little 4" area coming off the handle can be a god send. If a bow is starting to take a little set and we still have 6" to go if we had kept that 4" area a little on the stiff side we can now go back in there and get what we need. If we don't need it all the merrier, less working limb equates to more efficiency.

     Losses in efficiency are mostly do to hysteresis which drastically increases rapidly when the belly starts crushing. Uncompressing the back does not seem to have this same effect.  If a bow is truly overbuilt you will notice low efficiency numbers early on even before set becomes an issue if you are testing. Once you are finished with a bow I don't really know how you can tell the difference except maybe some extra handshock. 

     

[Pat B]

My idea of an overbuilt bow is the way Paul Comstock described it in the Bent stick, full width for most of the limb with the tip taper in the last few inches. This is a good design for a weaker wood or if you want a less stressed, more durable bow.

[DC]

      I suspect a lot of reflex we loose is often because the back of the bow is simply becoming uncompressed.

I've noticed that a backed bow with glued in reflex holds the reflex much much better than one with heated it reflex. As PatM said a while back it's because the backing is actually shorter rather than being compressed.

[bradsmith2010]

I had the Sinew come off a bow,..even though the bow had been drawn quite far,,,it showed no set,.I think the Sinew kept the wood back from becoming uncompressed

[Bayou Ben]

Thanks for the insight Steve.  One of those re-read a bunch of times write ups to let it soak in.

[/quote]

I've noticed that a backed bow with glued in reflex holds the reflex much much better than one with heated it reflex. As PatM said a while back it's because the backing is actually shorter rather than being compressed.
[/quote]

I'm trying to understand this.  Wouldn't a glued in back be compressed too? 

[PatM]

I think the term compressed isn't  the best for describing a back.   The cells probably shrink but that's not the same as being squeezed in compression. So they are shorter but for a different reason and by a different mechanism.

 When done as a glue-up the compression on the back has to be insignificant relative to the actual shortening of the backing strip due to moving the glue line.

[DC]

I'm trying to understand this.  Wouldn't a glued in back be compressed too? 

If you glue in the reflex as soon as you take it off the caul the back goes into tension. The belly wood is trying to straighten it. Does that help?

[Jim Davis]

It has been widely said that a bow is 90% broken at full draw. My observation is that an overbuilt bow is some amount less than 90% broken at full draw. (Don't recall whether the % was 90 or 95, but the concept remains.)

[Badger]

I'm trying to understand this.  Wouldn't a glued in back be compressed too? 

If you glue in the reflex as soon as you take it off the caul the back goes into tension. The belly wood is trying to straighten it. Does that help?

   I mostly agree Pat, I think when you do a glue up as you said earlier the wood is just shorter, But when a piece of wood is forced into reflex either by heat or through the drying process I think the back cells are compressing some. If it grows that way natural I would suspect they are just shorter as in a glue up.