An experimental warbow

[Rich Saffold]

Mark I have a couple on my website, and I will post my latest one tomorrow.  The skinny one which is a 50/50 ipe/boo mix has been most entertaining design. The tri-lams might have couple fps edge, but nothing scientific has been undertaken..(was more than happy with the speed )..

What Steve says in his last post is why I floor tiller my bows well past brace height before stringing them..Feeling the bow flex in my hands tells me when I am getting it close to straining it. I have seen too many bows over strained by someone leaning back with the pulley rope in their hand, and this is fine for learning and you have to see these angles to learn..I'm happy when I can do very little to the tiller after the first stringing, and basically start shooting with a scraper in my back pocket in case I need to touch  up a limb while shooting it in. My philosophy is I like having my limbs break-in by quickly releasing arrows as opposed to going back and forth slowly on the tiller tree. At least it works for me..

Rich-more to come

[markinengland]

Steve,
I agree that it is good not to overstrain a bow in the making. I am learning this as I make more bows. I no longer try to break a bow in, but gentle it. At one time I felt you had to work a bow to make it give in. Still, even these bows proved to be durable and shoot OK.
If you never pull a bow over the draw weight you want you will not undershoot when you have worked the bow back to the weight and draw length you are seeking. Also you will not have too much set as there should not be much overstrained wood there, just enough that tells you you are on or near the limit.
I feel that there may be a bow/arrow design that would give good performance at failry low brace tension. Maybe a long draw design similar to the yumi or even the English Warbow? It seems that for every rule we come up with there is a design that performs well that is basically the opposite! Maybe there is a bow design in which the initial release and acceleration is fast but that the final release of the arrow from the string is soft? What is lost in the lack of final push may be gained in terms of spine tolerance and arrow flight? Would there be a bow that is basically made to eb delfexed at brace height for very low brace tension but that would unwind during the draw to have high tension? Maybe a delfexed bow with a lot of contact recurve or a deflexed bow with hidden reflex within straight limbs?
Anyway, that is getting at least a couple of years ahead of my speed and time for bow making. Here I am making a slightly reflexed slightly recurved heavy bow and thinking of other things already.
Why do you feel your 140lb Osage had such low early draw weight and how did it perform? I have seen some big warbows shooting big heavy long arrows that performed quite well with relatively low early draw weight. It seems that some find a bow that has a significant amount of the draw weight past 30 inches or so works well for them as this is where their bodies find the leverage for pulling the high weight. I wonder if some of the warbow's dynamics are as much about the leverage/machine properties of the human bodies ability to pull such a weight as the performance? There would be little point have very efficient bows if the draw weight lower in the draw was such that the archer could not pull past this to get to the point where the body can be put into the bow to pull greater weight.
Rich, Maybe I am not experienced enough at floor tillering, but I find it very hard to truly guage the final draw weight of a stave at floor tillering. If the bow is at all reflexed floor tillering feel can be decieving and a bow can be reduced too much and end up underweight. I find it works better for me to floor tiller for basic bend and then get to a low brace height as soon as possible. I then tiller at very low draw lengths of no more than 6 inches past brace height never going over or too near the final desired final draw weight. I keep doing this until I have the brace height tiller shape I want, with good shape and even bend. I then gradually pull the bow further an inch at a time, keeping at or below fina draw weight, exercising the bow well after each wood removal. This allows me to creep up on the final draw length and weight with a well exercised and proven bow. I'd guess that tillering this way may make for a bow that performs slightly less well but that is less likely to fail in use? For a flight bow I'd guess that your method would be best. Make a bow to a proven formula, make it to brace height, pull it no more than 6 inches and make the first shot the one you do for the record. Risky but it would mean that the very best performance of the bow was on the flight shooting ground and not tied to the tiller!
Must go now as I have an experimental bow calling me.
Mark

[markinengland]

Well, I started tillering.
The bow is somewhat weak in the handle area. I think I would add an extra section between the belly and backing on the next bow I do like this. The Ipe flooring I have is a little thin in depth for heavier bows unless I go wider at the handle.
I got the bow to around 66 pounds at 23 inches and just starting to show a little set in the handle area. Bow mass is 28.5 ounces. The bow is bending too much in the handle though brace shape isn't too bad the weak handle shows up when it is drawn. I'll have to reduce the mid limb and tips more. Unfortunately I don't think the bow will make the weight I was after as it stands.
I am torn between making the bow to the weight it wants to be or adding a narrow second boo backing to up the strength.
Here is the bow at about 22 inches, 64lbs or so. I had a reflex deflex shape in mind so was prepared for a shape that looked wrong to my eyes, limbs looking stiff and handle looking too bendy but I think the handle area is bending too much and the outer and mid limbs too little, probably more mid limb that outer allowing for the glued in reflex in the outer limbs.

Here is the bow side profile just after taking the bow down from the tiller and relaxing the string. Now about half an hour later there is  about 1/16th or so of set in the handle.

Thoughts?
Mark

[Badger]

Mark, as weak as that handle area appears I would be tempted to cut the bow down to about 70" and reshape the sides. Simply not enough beef in the center for the kind of weight you were after. Steve

[markinengland]

Steve,
Have you ever added a backing to a bow part way through? My thinking is that I could shorten the bow to say 72 or 70 inches to increase the draw weight a bit but this would simply move the strong area to the tips and leave the centre weak.. I could reduce the width and depth of the mid limb and limb tips but I would need to remove a fair amount to compensate for the extra strength the localised reflex is causing.
Would adding a boo backing allow me to alter the thickness and width of the backing as well as the reflex to compensate and add to the potential of the bow instead of reduce it?
Mark

[Badger]

Mark, that very well could work. Worth a shot I think. The center arera that is bending at 65# is just responding to the draw weight and I think has nothing to do with the tips being strong. What kind of width to thicness ratio do you have in the handle area of the bow now? I would not go past 1 to 1 for sure. Steve

[markinengland]

Steve,
The width at the handle is one and one eighth, the depth seven eighths. That gives me a quarter of an inch to play with!
A bamboo backing could be made to be thick at the handle (though not across the whole of the back) but thinner as it goes towars the tips becoming almost a feather edge at the tips. I could give the handle area a degree of reflex and leave the rest basically as it is. This may even things up somewhat as well as unintentionally allow me to try adding a second backing.
Mark

[Rich Saffold]

Mark,What if you built up the grip area, and do what Steve said? You should have enough wood there for 90#'s  Have a rigid grip and get the midlimbs working a bit more. Check out the bow I posted on the general forum. It's the same basic idea with a rigid grip.

Rich

[markinengland]

Rich,
Thanks for posting your bows. Very nice.
I have now glued on a boo backing and given the central handle area some back set. We'll see what it loooks like when it is cleaned up. A learning experience again!
Mark

[Rich Saffold]

Experimenting is the fun part. We all have a bow we can hunt with

Rich

[Marc St Louis]

I don't think you have enough width to go really heavy. It will become unstable laterally and try to flip flop

[markinengland]

Marc,
I'll find out what kind of THING I have created when I take it out the clamp and rubber wrap tomorrow. Flip flop bows aren't fun.
Mark

[markinengland]

Well, it broke.
It cleaned up OK. Looked like it would be a goer.


Basic bend even looked good.

I was reducing the limbs to get it to near weight, stringing it to a no brace height to get a feel for how it was bending and how the weight was dropping. I guess I rushed things as it broke while being strung.

[markinengland]

So what have I learnt from this experiment?
I am embarrassed to say I have learnt some of these things before!
1) With Ipe a little relfex goes a long way - still.
2) Long narrow Ipe bows with reflex are bad news - Mark, you know this! Repeat one hundred times.
3) Don't rush - once you have it is too late to unrush.
4) Believe your eyes. It doesn't matter how much you would like the shape to be something else. Go with what you see - it really is there!
5) You can't force a bow to be something it isn't. If the bow wants to be 70lbs and you want it to be 110lbs, it will either be 70lbs or broke! - look at the broken bits if you doubt this Mark.
6) Over a certain draw weight the beey stave needs to be over a certain thickness. With the wood I have I need a central lam even if only in the handle area.
7) A second lam apparently really really ups the draw weight.
Using resorcinol bamboo doen't glue too well to horn and not that well to hickory.
9) Using the layout I experimented with and a central lam in the handle area a LITTLE reflex at the tips could produce a good fast bow with stiff light tips, but the middle of the bow needs to be adjusted to compensate.
10) There may be potential in a bow with two seperate backings, but the extra stress means that glue lines are critical and the bow must be designed with this in mind to begin with, not as an after thought.
11) The s econd backing must go under the nock/nock overlay.

As with most learning experiences I guess it was useful, but I wish I didn't keep doing this to myself.   

Mark

[SimonUK]

Sorry to hear that mark, I was looking forward to seeing the finished bow.