Sharp hooks ( a how to and lots of argument as to their merits )

[Danzn Bar]

Pending on bow length and draw length you may have to cut some length off of those hooks........the main thing is having the string lift off the limb at about one or two inches from full draw..... anything else is wasted weight/mass.
DBar

 Has this ever been proven?

I usually never get into forum debates ...but In my mind, there's no difference if the string lifts off at the nock or two inches down the limb from the nock, therefore more mass....what is your point?  Why do you add tight recurves?
DBar

[PatM]

Because they've been proven to work. The debate is whether they don't work until the string actually lifts off.  They are dead weight either way.

[Danzn Bar]

Because they've been proven to work. The debate is whether they don't work until the string actually lifts off.  They are dead weight either way.

That's why I don't debate.. just listen........my point is they don't work as intended if the string doesn't lift off the limb.....maybe it's just adding "more" dead weight.
DBar

[PatM]

So just speculating then. A good test would be to build a bow that has sharp hooks and lifts off two inches from full draw and then increase the curves a few degrees so that it doesn't lift off and test it again.

[Danzn Bar]

Some people have no common sense ....................everything must be proven/tested to them...
I don't think you have ever build a bow......prove it/test it with a full draw pic....or am I speculating?
Good night I'm done,
DBar

[PatM]

  Just say you don't know then. 

[Bryce]

YAAAARGH! I likes to boil me hooks💀

If you put a barb on that you could catch fish

Seconds as a gaff hook

[joachimM]

Proving that too sharp hooks don't work when they don't lift off: easy.
recurves that don't lift off add mass to the bow. Mass that's not working at any point during the draw or increasing leverage. So you might as well have a shorter recurve and add lead to them. The longer it takes for a recurve to lift off during the draw, the longer it's dead mass. Sure, it gives a fatter force-draw curve. That's expended energy. Large part of that fatness is needed during release to move the heavy tips instead of the arrow. Hence, you're losing efficiency.

See it in terms of leverage and tip mass. Recurves have high early draw weight because early in the draw they are functionally shorter bows. A 60" bow with 5" hooks is at brace a 50" bow with the mass of a 60" bow. The functionally shorter bow strains the wood more at each increment of draw, so you have higher early draw weight. Later during the draw, when the string lifts off, the extra leverage comes into play. The bow becomes functionally longer, with more leverage, so less draw weight gains per draw length increment. But only when the hooks are cantered 90° relative to their original position is the leverage fully realized. Before that, the bow is still functionally shorter than its initial 60". But at all times, it carries at its tips the mass of the 60" bow. So the trick is to find where this trade-off between extra mass and extra leverage is optimized.

Kooi & Bergman 1997 http://www.bio.vu.nl/thb/users/kooi/kobe97.pdf
showcase this very nicely. With the extreme Hickman working recurve (2/3 of recurve) as a good example to contrast to a normal working recurve and static turkish and persian recurves.
https://www.flickr.com/photos/farflinger/5177069236/in/album-72157625386947492/

This bow design was patented by Hickman as a revolutionary new bow design. String lifts off completely at about 21". That means that before that, it's functionally a shorter bow, but with the extra mass of a longer bow, concentrated at the tips. The reason we aren't all shooting this high-energy storage bow is that it's not efficient at all. The fat force draw curve deceives the eye but not the arrow. And neither the mathematic model by Kooi & Bergman. In fact it isn't faster than a well designed straight stave bow with a flat force draw curve. Anything above the straight line in the force-draw curve of that bow is energy wasted in moving a returning limb with a portion of dead mass that becomes larger during the return of the limb. With cartilage-unfriendly hand shock.

If you don't buy this explanation: experience for yourself. Make a recurve with 90° hooks that don't lift off. And make them looooong. 10". And make a recurve with shorter hooks, that lift off early during the draw. See which shoots best. If you don't want to waste good bow wood for this, make these example bows out of PVC. Will take you 1 h in total.
it's just a matter of dead mass caused by bow parts that cannot store nor impart energy to the arrow by either working or adding leverage during the entire draw. 

There's a reason why the fastest @10gpp wood-only bow built so far is a long straight stave bow without sharp recurves...

Joachim

[Stixnstones]

Sleek, i'm fairly new to the whole flippin tips thing. Here's my 2 pennies. I tried dry heat and lifted splinters twice. Steamed 4 different bows worth of tips, zero problems. I just let the bow sit for a few days after steaming. I vote steaming. But the choice is yours . Good luck either way.

[PatM]

Still a lot of speculation there, Joachim. The static portion doesn't do any work whether it lifts off or not, right?
 We are talking about static recurves, not working here.
   
Until that long straight bow outshoots the short flight bows with 90 degree hooks then there must be more going on.
  Using your example of two different bows proves nothing, you need to use the same bow and only change the degree of the hooks. Apples to Apples.
   It would take you  half an hour with a piece of PVC.

[Marc St Louis]

Proving that too sharp hooks don't work when they don't lift off: easy.
recurves that don't lift off add mass to the bow. Mass that's not working at any point during the draw or increasing leverage. So you might as well have a shorter recurve and add lead to them. The longer it takes for a recurve to lift off during the draw, the longer it's dead mass. Sure, it gives a fatter force-draw curve. That's expended energy. Large part of that fatness is needed during release to move the heavy tips instead of the arrow. Hence, you're losing efficiency.

See it in terms of leverage and tip mass. Recurves have high early draw weight because early in the draw they are functionally shorter bows. A 60" bow with 5" hooks is at brace a 50" bow with the mass of a 60" bow. The functionally shorter bow strains the wood more at each increment of draw, so you have higher early draw weight. Later during the draw, when the string lifts off, the extra leverage comes into play. The bow becomes functionally longer, with more leverage, so less draw weight gains per draw length increment. But only when the hooks are cantered 90° relative to their original position is the leverage fully realized. Before that, the bow is still functionally shorter than its initial 60". But at all times, it carries at its tips the mass of the 60" bow. So the trick is to find where this trade-off between extra mass and extra leverage is optimized.

Kooi & Bergman 1997 http://www.bio.vu.nl/thb/users/kooi/kobe97.pdf
showcase this very nicely. With the extreme Hickman working recurve (2/3 of recurve) as a good example to contrast to a normal working recurve and static turkish and persian recurves.
https://www.flickr.com/photos/farflinger/5177069236/in/album-72157625386947492/

This bow design was patented by Hickman as a revolutionary new bow design. String lifts off completely at about 21". That means that before that, it's functionally a shorter bow, but with the extra mass of a longer bow, concentrated at the tips. The reason we aren't all shooting this high-energy storage bow is that it's not efficient at all. The fat force draw curve deceives the eye but not the arrow. And neither the mathematic model by Kooi & Bergman. In fact it isn't faster than a well designed straight stave bow with a flat force draw curve. Anything above the straight line in the force-draw curve of that bow is energy wasted in moving a returning limb with a portion of dead mass that becomes larger during the return of the limb. With cartilage-unfriendly hand shock.

If you don't buy this explanation: experience for yourself. Make a recurve with 90° hooks that don't lift off. And make them looooong. 10". And make a recurve with shorter hooks, that lift off early during the draw. See which shoots best. If you don't want to waste good bow wood for this, make these example bows out of PVC. Will take you 1 h in total.
it's just a matter of dead mass caused by bow parts that cannot store nor impart energy to the arrow by either working or adding leverage during the entire draw. 

There's a reason why the fastest @10gpp wood-only bow built so far is a long straight stave bow without sharp recurves...

Joachim

I sure would like to know where you got that statistic because it is quite contrary to my observations and to my experiences

I have made a lot of recurves both with short and long hooks and my chronograph experience has shown that in relation to speed it doesn't matter, flightbows might benefit a bit though.  The real difference that I have found is that long recurves are much more sensitive to string tracking and the slightest imbalance will exacerbate limb twist, not so with short hooks.  Quite frankly there's just too many variables at work here for accurate predictions

[blackhawk]

I could care less if a static is faster or slower,or what the optimum  length and angle is with them,or at what point its best for the string to lift off in the draw......i just like the sweet smooth draw of them and how nasty sweet  ~90° hooks look    and yeah besides good looks on a bow they do spit an arra to my liking 

Btw...i use steam alone,no straps,n bend it all at once with good results that usually makes a nice clean non torn or splintered wood...such as this 

[BowEd]

On my tillering tree I can see when the string lifts off the static.

[joachimM]

There's a reason why the fastest @10gpp wood-only bow built so far is a long straight stave bow without sharp recurves...

I sure would like to know where you got that statistic because it is quite contrary to my observations and to my experiences
[/quote]

Don't take it too literally. Rather, one of the fastest. I'm referring to one of Tim Baker's pecan bows shooting (if y remember right?) 192 fps at 10gpp and 28" draw. There may be or have been bows of similar performance (see your HHB bow on p66 of TBB4), but I'd be surprised if any of they had long 90° hooks.
Don't get me wrong either: I'm not saying (static) recurves are always bad and reduce efficiency. My point is that there is an important trade-off to take into consideration, which I tried to explain above. Just assuming that big hooks will boost performance of any bow is wrong.

Kooi & Bergman 1997 equally conclude that net efficiency of Turkish composites (with rather small static recurves) must be smaller than that of straight-stave bows:
"Notwithstanding this, the efficiency η of the ‘Persian’ bow, and certainly that of the ‘Turkish’ bow, is rather low. This implies that the initial velocity ν is not as large as one would expect on the basis of the static performance.  This is caused by the relatively heavy ears.  These considerations demonstrate why these bows can, inherently, be no better than long straight-end bows; a large part of the available energy remains in the vibrating limbs and string after the arrow
leaves the string"

This is confirmed in practice by tests of Adam Karpowicz (http://www.atarn.org/islamic/Performance/Performance_of_Turkish_bows.htm). None of his bows shoot faster at 10 gpp than 185 fps, which is less than the 190 fps of your own HHB or Tim Baker's pecan board bow. Note that with your HHB recurve there is a nearly immediate lift-off early in the draw, which is required to boost efficiency.

joachim

[PatM]

I don't believe anyone said big hooks, they said sharp. Whatever length you need to make them sharp.
  The bottom line is still what cast is achieved with each type and sharp hooks historically have done much better.