Q about reflex and performance

[simk]

Hi Guys

What I have learned about making bows is that a high early string tension is one key to a good performer and high early string tension is greatly affected by the amount of overall reflex a bow shows.

When making wooden bows this mainly means you try to minimize set. When it comes to overall reflex you are pretty much limitated by the wood. Keeping a 0 or 2" of reflex over time alredy seems like superb result. Glass  on the other hand seems to tolerate the stress much better and would allow tremendous amount of reflex in the bow. I imagine 4-8" of reflex on a longbow  or recurve would not be much of a problem?!? Or do you run into specific problems?

What I have noticed however is that you glass-guys do not put overly much reflex in your bows either, give away that potential. Or am I wrong? What are your thoughts about it?

Very curious.

Simon

[kennym]

I had a pretty straight riser(not much deflex) longbow that I put the nocks 4" ahead of bow back. It didn't make it go much faster, but it sure was a a pain to be accurate with. You had to be on top of your game.  I think it was easy to torque, but may have been the grip shape or other reasons also.

That said, I added an inch of reflex to my 64" longbow form and made 5 lbs and 5 fps. The nocks are about an inch ahead of the bow back.

[Mad Max]

I searched back to 2022 and found this


I think this is the post you mentioned Max. It is a quote, more or less from the book Ottoman Turkish Bows by Adam Karpowicz:

“We can now summarize the design characteristics of a fast bow … 1. make it as short as possible and the limbs, including the bending section, as thick and narrow as possible 2. draw as far as possible 3. reflex the limbs as much as possible 4. keep the bending as close to the grip as possible for the longest limb path. All four requirements can be met, but only within the constraints of material properties, the skill of the bowyer and by the strength of the archer.”


Rich Redd is getting fast results with his D shaped R/D.

So who knows what is true

[Kirkll]

It’s not just the reflex, or the measured amount the tips are in front of the back of the riser  that determines the pre load on your limbs. The shape of the limb itself , and the taper rates used have a huge impact.

 I agree that  the deeper core, narrow limbs will always be faster regardless of limb geometry or limb shape. I also believe that limb travel to pre load ratios are very important. The only way the stored energy in the limbs gets transferred to the shaft is by stopping the forward limb travel clean. This clean stop and transfer is also effected  by the mass weight in the outer portion of the limb that is actually traveling.   

As far as bow length goes. I believe the actual bow length is not as important as the length of the working portion of the limb, and where that working portion is located.

For example:  if you have a straight long bow with short wedges and low preload that is coming hard off the fades, this typically increases the limb travel. The result is a lot of hand shock and lower performance levels. With a TD bow,  If you take the same limb shape coming out of the same form and change the limb pad angle pushing the tips further past the back of the riser and increase the preload. This alone will increase performance and reduce hand shock…..

 Now instead of shortening the over all limb length, or bow length…. You increase your wedge length, and use tip wedges to shorten the working portion of the limb.
This forces all the energy storage into a shorter section of the limb, and doesn’t require the same amount limb travel to store more energy. As you draw the bow the string is moving and the limbs are compressing as the string angle changes….

This is where the static tip RC or even hybrid long bows really shine, and the Turkish style bows rule. If you watch the limbs closely as a static tip recurve is drawn, the first half of the draw the tips are going from a reflex shape to a vertical position and actually increasing, or maintaining the same length over all bow length before the string even lifts off of the belly of the limb, and your limb travel is minimized and more importantly the direction of the limb travel is changed. The limbs are coming slowly together as the energy is stored, rather than the limbs coming back.

As the string is dropped, and the limbs come back to brace position, the string rolls back up over those static tips making the two contact points of the string much shorter with much higher string tension to stop the string itself, and any limb movement clean….

I’ve never played with the Turkish style bows, but they have always amazed me how well they perform coming off the fades so hard. But I believe the shape of those limbs and incredible preload they have is the key….

There’s about .06 cents worth….        Kir

[mmattockx]

Hi Guys

What I have learned about making bows is that a high early string tension is one key to a good performer and high early string tension is greatly affected by the amount of overall reflex a bow shows.

When making wooden bows this mainly means you try to minimize set. When it comes to overall reflex you are pretty much limitated by the wood. Keeping a 0 or 2" of reflex over time alredy seems like superb result. Glass  on the other hand seems to tolerate the stress much better and would allow tremendous amount of reflex in the bow. I imagine 4-8" of reflex on a longbow  or recurve would not be much of a problem?!? Or do you run into specific problems?

What I have noticed however is that you glass-guys do not put overly much reflex in your bows either, give away that potential. Or am I wrong? What are your thoughts about it?

Very curious.

Simon

As you note, early tension is the key to a fat F/D curve and lots of energy storage, which helps throw arrows faster. My experience making wood bows also agrees with your thoughts that keeping any reflex at all through tillering is a very good result on a wood bow.

While fibreglass allows much higher stresses in the limbs, it also has a number of weaknesses. It is heavy compared to wood, so you have heavy tips that hurt performance. To really strain FG significantly you end up with very radically curved recurve limbs and those have stability problems that are hard to manage. Because FG is much stronger than any wood it is also hard on the limb cores and you have to be careful not to overstress the core wood even though the FG lams can carry the loads easily. Howard Hill style bows show this problem quite a bit, often taking significant set because the core lams are over stressed.

The bottom line is that FG has weight and stability problems that limit its maximum performance while wood has strength issues that limit its performance. A well designed/made/tillered wood bow gets very near all the potential performance out of the material while a well designed/made/tillered FG bow only gets maybe 50% of the potential out of the material.

Note this applies only to traditional bows with long limbs. To see the optimum way to use FG in a bow limb, look at compound bows. Extremely short, stiff limbs store a ton of energy through small amounts of movement and put all that energy into the arrow through the use of levers (pulleys and cams in this case) to multiply the limb motion. The short limbs avoid the stability problems that our bows have and the limbs are solid FG so there is no core material to fail early. By limiting limb motion the weight of FG is irrelevant because the limb never moves very fast.


Mark

[Mad Max]

While fibreglass allows much higher stresses in the limbs, it also has a number of weaknesses. It is heavy compared to wood, so you have heavy tips that hurt performance. To really strain FG significantly you end up with very radically curved recurve limbs and those have stability problems that are hard to manage. Because FG is much stronger than any wood it is also hard on the limb cores and you have to be careful not to overstress the core wood even though the FG lams can carry the loads easily. Howard Hill style bows show this problem quite a bit, often taking significant set because the core lams are over stressed.



Mark

cutting off  6" of the tip of a glass bow verses the all wood bow same draw weight the wood would be heaver for these short recurves.

No stability problems for me. 50" NTN




Top 3 bows

[Buemaker]

Max.The bow at brace height, may I ask what kind of tapers and is there a tip wedge. Sexy looking thing.

[Mad Max]

Max.The bow at brace height, may I ask what kind of tapers and is there a tip wedge. Sexy looking thing.

The picture with 4 bow's ?? That is the Sheepeater bow (Shoshone Bighorn)
.004 total taper, the 2-1/2" radius dosent need a wedge, Static

[Buemaker]

It was the picture in the middle I was thinking about, sorry did not see that two of them were strung. Thank you.

[Mad Max]

It was the picture in the middle I was thinking about, sorry did not see that two of them were strung. Thank you.

Parallel
Tip is a belly wedge with string grooves to help keep it line up.
It's not brace, I'm just holding the string in the grooves in the picture bue

[Kirkll]

You’ve done some amazing work Max…

I’ll  bet  that top bow is fun to get a string on it.

[simk]

Thanks everybody for contributing, looks a like another can of worms....

especially if the topic is widened towards a general "recipe to make a faster bow".

I'm familiar with Karpovitz' theroy but mixing up all the elements is confusing. I could even enlarge confusion now and bring "string angle" into play wich is directly related to shape of tiller.  Or I could add in the topic of limb vibrations. But I don't.

My initial question was only about reflex on glass bows and how you deal with that tuning-option on longbows and recurves. I was curious how you determine your "sweet spot" regarding reflex and why the amount of reflex in standard bows in general seems to be pretty moderate.

I leraned that Kennym wasn't happy with too much reflex which lead to a poor shooter for him.

Then MadMax showed us strongly reflexed static-recurve bows - pretty close to what I would do/try if I was messing around with glass. Very cool bows. How do they shoot Max? Did you measure fps? What was your intention creating these? Flight only ore are these good target bows as well? Is this your standard model Max?

Why do we not see more bows like these on the market?  Just because they are a pain to string?

Like so often, I think there must be a sweet spot. How do you determine that sweet spot for reflex,  which factors come into play and how do you weigh them up against each other. Advantages vs. disadvantages of more reflex?

Wish you a nice sunday!

Thank you for the interesting discussion.




Edit: Just glued up 7" of reflex into a 63" longbow. The last one with 5.5" was great, so I thought I'd increase some on the next one 




 

[Stagmitis]

Hey simon my Hills range anywhere from a slight string follow up to 2" of backset(glass version). 

What I notice is as I increase reflex the speed increases, accuracy decreases and the bow becomes harder to draw. The higher backset bows are miserable to draw compared to the lesser ones and feel heavier in draw weight.

I think each ammount of reflex has a certain purpose for its intended use. My favorite is a 3/4" backset for everday shooting and hunting deer sized game. For targets and 3-D a slight string follow or about 1/2 backset gives me the highest ammount of accuracy but still has good speed. If I were to hunt large african game I would opt for a 2" backset bow intended to push a heavy arrow as fast as possible.

On my bamboo backed Hills Ill reflex 3-4 inches to either get a slight string follow or about a 3/4 " finished backset bow.

[Mad Max]

Sheepeater Sprit static recurve, Brent Rudolph, Black Mountain Bows.
I was obsessed with this bow when I first started making selfbows, I was willing to buy a fiberglass bow but could not find one for sale, he was already out of business. His passion was to replicate a Horn bow the Sheepeater Indians made. with no shelf and a rattan grip.
Horn bow I found on the web.


Customers always want something different than what you sell, shelf, and more of a grip. His passion was going in a different direction with the modifications and a Take down was wanted also. I call him many times with no answers over a year time, finally talked to him for a hour or so.
Over time I got enough info from him to build one.

His bow is behind mine on the tiller tree.



Here is some info on his bow.
http://peteward.com/2007%20new%20pages/test.sheepeater.html

[Mad Max]

I was told years ago that 2 or 3" reflex on all wood bows was all you should go.
I see you have Bamboo back and horn belly on that one?? That could/should work but not sure.
Keep us posted on it

[Kirkll]

Wow!  I used to correspond with Pete Ward a lot years ago. Haven’t heard anything from him in years.  Is he still kicking?     Kirk

[Mad Max]

Not sure Kirk

[Bob T.]

Kirk. I believe that Pete Ward passed a while ago.

[simk]

Thanks Stagmitis and Max: Yes, glueing in more than 4" of reflex on wooden bows makes no sense. When I started I went with 4". Nowadays I normally do 2 or 3".
Thank you Max for links and pics. You did a pretty precise replica of that bow 
Still curious why we don't often see more reflexed FG bows (-;

My experimental bow is balanced and strung. Now it needs  some tillering. It feels pretty strong...I'd say 50# @ 24". Going to shhot my light arrows quick 

Cheers

[onetone]

Quote from simk:
“Why do we not see more bows like these on the market?  Just because they are a pain to string?”

I can’t answer your question, yet I share your wonder. I have built a number of Ottoman style horsebows using fiberglass which exhibit extreme reflex before bracing, similar to the bow in Max’s first couple of photos. I had reservations about such short, light weight at the start and had several failures on my way to building a durable design. The longer bow design is 48” long braced, 50# @ 28” and I have shot thousands of arrows through a couple of them to test durability. I actually have counted and am not pulling numbers out of the air. My target arrows are 8+ gpp and flight arrows are 3.5 gpp or less. I am satisfied with the durability of these bows.

I will mention a few factors I like about these bows. They are short, light and good in a blind or in the brush. They are quiet, no need for string dampeners. There is no need for an arm guard as the string doesn’t vibrate enough to hit the forearm. They are fast shooters, in part because of the heavy preload and low limb mass. They require less than half the materials I use to make western style recurves, which matters in these times of rising costs. Some say shorter bows are not as accurate as their longer kind. I have not found this to be true in my experience and I shoot fairly regularly out to 60 yds.

Although it is possible to shoot these bows with fingers, I early on adopted using a thumb ring and found it provides a cleaner release, another plus of this branch of archery.

On the down side there is the issue of stringing these bows which can be an “adventure” with scabs. Still, that process can be mastered, even by an ol’ fart like myself at 75. 

The major reflex is a big part of what makes such bows outstanding and I too wonder why more archers do not take advantage of this particular aspect of design.