Juniper core

Looks nice and also daring with the horn. But uhm... how do you define reflex?

Sorry for the bad explanation. This reflex is only from the angle of kasan and ear. Then the sinew shrink and draw in more reflex. This is what I call factory reflex :)
Added reflex are made by drawing the tips together with tread during the drying time. The tips can meet when done. This what I call added reflex :)

Redhorse wrote:

Sorry for the bad explanation. This reflex is only from the angle of kasan and ear. Then the sinew shrink and draw in more reflex. This is what I call factory reflex :)
Added reflex are made by drawing the tips together with tread during the drying time. The tips can meet when done. This what I call added reflex :)

Hang on, I thought this made reflex in the sal part happen, not at the kasan/siyah junction ...
Also how do you measure reflex in inches? I've always been used to measuring bends and curves in degrees.

Do you have a picture of it strung? And how broad is it?

From beginning the core is flat laying on table. The kasan is made with a angle and the ear also. I make it so the ear at 90 degree to the table still with flat sal on the table. Then the horn is put on, many do flatten the horn before gluing, I don't. I let it have the curve it has. Here we got the first amount of reflex, all depending on thickness of the wood and horn. Now the kasan eye will be higher from the flat table. And at last when the sinew is dry it got some more reflex. Factory reflex :)
But you can add more reflex mechanical. Man made reflex.

I did cut away 1/2 inch on the ears and made it a 46" bow.
Made a new fd-curve. Interesting is that the early weight did drop.A higher weight at full draw as it should be. And the efficiency did raise, the bow is 7 grams lower mass of course at the tips.. Still bad but better.

If you keep shortening the siyahs, you will loose more early weight and increase the efficiency. Then, in the end, you'll have a linear force draw curve and the highest efficiency. This characteristic reminds me of another type of bow. ;)

Theoretical yes. But the straight bow will never have the same efficiency as the reflex hornbow. If it could they had already been made :)
We can have a high energy storage and shot fast with it even if we have a lower efficiency. Some energy is waist but we can still out shot other bow designs.

When extending the draw length it did crack in one limb and a hinge occur. It did shot still.
But I did remove the horn and the core is broken.
I been thinking of an absolute meaningless repair. Copy the core and rasp it away from the sinew and glue in the copy under the sinew :)

Actually both sal was broken :(
So I made a new core.
First picture at 7" and second before any bend. The kasan feels weak so they will get more sinew. The load is about 40-45lb each limb so it indicate a draw weight about +80lb.

hello redhorse, I am not claiing to understand this complex subject, but I believe it is a common problem when working out fd-curves for these type of bows, that the energy in these bows is very high when braced, due to there nature of being highly reflexed, but much of this energy can never leave the bow and this is why they apear to be innefficient, the only way all of this energy can be tansferred to the arrow is if the string broke when it returned to brace position! otherwise during a normal shot it can never release the energy stored in reserve at brace, so to speak. The energy stored when bow is braced needs to be calculated and subtracted to give real efficiency figures,???? What do you think??

A fd-curve shows only the energy that is put in at draw, not the stored energy at brace.
I watch a American bowyers video where he claim that his bow also put the energy stored at brace in the arrow.
I can't see how that can happen?

The energy put in the bow is the are between zero axle and the curve.
This is divided between the arrow mass and the dynamic mass of the bow and string.


Bows with reflex inhibit high early draw wight and thus store more
energy with the same max draw strength. That is the idea of reflex.


There is also energy that is put bracing the bow. It cannot be released without unbracing the bow.

jkekoni wrote:

The energy put in the bow is the are between zero axle and the curve.
This is divided between the arrow mass and the dynamic mass of the bow and string.


Bows with reflex inhibit high early draw wight and thus store more
energy with the same max draw strength. That is the idea of reflex.


There is also energy that is put bracing the bow. It cannot be released without unbracing the bow.

All is correct, but you don't get the energy to the arrow from the reflex. With more reflex the efficiency drops. So its waist energy to draw the strong bow if its not going to the arrow.

I think that the energy put into the bow in order to brace it can not be released without unbracing the bow as you say, but this "trapped" energy still indirectly gives its energy to the arrow, because it effects the energy needed to draw the bow. A bow with more energy stored at brace is harder to draw!, which causes the archer to have to put more energy into the draw so the arrow recieves more energy when released,so surely this energy needs to be included in the efficiency formula ??

Still, more reflex means more stress which means the bow has to have more mass to do the work and probably broader limbs to keep it stable. Perhaps a highly reflexed bow is better with heavy arrows, while it isn't as important for bows shooting light arrows?

That doesn't conform to the old turkish bows though, where it seems impossible to put more reflex into the bows. I guess they just demanded both high efficiency and reflex, by stressing the materials even more

Kviljo wrote:

Still, more reflex means more stress which means the bow has to have more mass to do the work and probably broader limbs to keep it stable. Perhaps a highly reflexed bow is better with heavy arrows, while it isn't as important for bows shooting light arrows?

That doesn't conform to the old turkish bows though, where it seems impossible to put more reflex into the bows. I guess they just demanded both high efficiency and reflex, by stressing the materials even more

Actually we don't know how good a museum bow shot. We like to believe they are very good, but we don't know. All we know is some records :)
Our modern hornbows can be better :) or they can be worse, but we don't know.
But logic, if you were going out at field for some time, you would take a bow with you that you know do hold the trip.
If you are living in the city and only shoots at Sundays for distance you would think in other directions.
But then to the evidence, Adams fastest bow was not the shortest, you can shot longer with stronger of course but that is poor efficiency.
I have notice that longer is faster, but shorter is stronger :)

To my knowledge a recurved bow will always store more energy than a straight one of the same draw weight at a certain draw length. This is due to the fact that its initial draw weight (at brace height) is higher. The draw weight will then increase relatively evenly to the maximum, while the straight bow will have a lower initial draw weight and a draw-weight-curve that becomes steeper and steeper towards the max (so called "stacking").
Speed is basically dependent on how effectively this potential energy is transferred to the arrow. That in turn depends on factors like the mass of the limbs or tips, flexibility of materials etc.
A. Karpowicz has detailed this ratio in an article in the JSAA 50 (2007), pp.49-51. According to his findings only composite bows of higher draw weights will show better performance than self-bows because only then the ratio of mass and draw-weight will allow for better efficiency.

Could the reflex in the old bows be about stressing the materials to the maximum, and not just about having a fat draw force curve? Perhaps the explanation for all the reflex is related to the same issue as you mention, jsachers. As the horn/sinews need to be stressed higly to perform efficiently, perhaps the reflex is there to stress the materials even more and by that gaining efficiency?

Doesn't Adams test confirm that the bows needed to be highly reflexed to perform as they did?

Kviljo wrote:

Could the reflex in the old bows be about stressing the materials to the maximum, and not just about having a fat draw force curve? Perhaps the explanation for all the reflex is related to the same issue as you mention, jsachers. As the horn/sinews need to be stressed higly to perform efficiently, perhaps the reflex is there to stress the materials even more and by that gaining efficiency?

That's what I'd believe, but I can neither prove nor explain it ??I'm neither a bowyer nor a physicist.
But I am convinced that this is exactly the reason for gluing on the horn first and then add layers of sinew to form a reflex ??and not the other way around as is suggested in the "Reflexbogen" book!
The American bowyer Dan Perry "invented" what is now called the Perry-Reflex: he believes he can achieve better performance in laminated wooden bows by prestressing the laminates to a reflex form. The principle is the same as far as I can see. The physical explanation however is beyond my knowledge I'm afraid.

Still all is in the wish and believe stage. One day maybe we know also :)

Stressing the materials to the max makes sense only in the context of "low mass/high draw weight". As long as the bow does not acquire an excessive string follow, the reflex can be maxed-out to have low mass plus the heavy bow. We actually want to minimize stress in the bow to minimize creep in materials.

I think Redhorse is referring to one of my tested bows as the example of a good efficiency at the longer length. As I recall, these bow was drawn to 30 inches, not 27-28 like most others. It means the powere stroke was greater too and the bow was more efficient (=more weight/energy at the same limb mass). It is the case with all bows. If I tested the shorter bows at a longer draw, the bows would perform better too. Add two inches of bulk at the grip's belly (as it is the case of many all-wood bows) and you get two inches of free power stroke.

I believe the bows shoot fast if the limbs move fast (as per the, ahem..., complicated explanation in my book). Therefore the short bows are better in this respect. As long as the arrow is not too heavy, these bows are then the best for flight shooting, even if the reflex is low. But if one manages to make a short bow AND at the same time well reflexed, with no breakdown in use, then such bow will perform well with heavier arrows too, since the stored energy is greater with the reflex.

Adam

I have tested bows with different draw length and had bows that was more efficient with shorter power stroke.
What I think is that the balance in the bow is what makes it good.
And what is the balance?

What is the balance of the bow?

jack farrell wrote:

What is the balance of the bow?

I have a few idea of it but is interested in what other thinks.

The balance:

That?s the final question?
It includes the design and the material(quality) of bow and arrow, as well as the capablities of the bowyer and the archer.
The design is actually much over- estimated, endless discussions here, in the Paleoplanet, the quality of the materials is almost completely out of discussion.
If you have a serious look at the old reports, it is easy to see,that our ancestors knew very well where to get the best raw- material for their best bows.
In self- bowery the impact of material is very obvious. It is not to difficult to make a 50+lbs selfbow of elm casting an arrow about 160-180m, but how did Marc St.Louis manage it to make the "same" bow(60lbs) to cast an arrow about 340m?
Let?s go on to discuss this topic, it will be very worth it, but I don?t think, that it is possible to come to a final conclusion, cause our bowery is a living thing. And for to be honest, I don?t like final conclusions.

Michael

I have shot straight bows and strongly reflexed recurves and there is no doubt in my mind that the quality of drawing and shooting the recurves is smoother and 'nicer' Straight wooden bows may be nearly as fast or faster but the need to pull harder and harder as full draw approaches is not so good.
Perhaps it is all about the quality oif the draw and the shot not just the speed and the power???
I believe a bow is balanced when both limbs match and behave exactly the same

I did have the bow in the press and had balance in limbs, bending better now. I had put on more sinew on the handle and fades. But I did hear cracking sound and just leave it, suddenly one horn explode. It did break a few inch before the kasan eye. Sad is that the core got some compression damage but maybe I will splice in a new horn strip anyway, just for experience :)
A similarly thing happened in a bow a year ago. It had the same fault, it had a twist in the limb and was also made from a inner curv.

I am sorry to hear that your bow broke, good luck for when you try again.