I really need some "mass principle" help

[RyanY]

Don, I’d recommend making sure your tiller is spot on. If you can make bows with low set and good string tension at brace then speed will follow. Keep those tips narrow. No need to be wider than 3/8” at the tips. Avoid inner limb set.

[PatM]

The principle is maybe a bit  outdated.  Not long after it came out it was already being revised. 

 I don't bother weighing bows for mass.  It doesn't seem like a number to chase.

That's fine if you already know how to build efficient bows. It's definitely a learning tool for us who need it

 It might make you jump too far to the extreme though.   Steve builds bows in  large quantities and tends to not shoot them for too long before moving on to the next one.  He also wants them to remain brand new and fresh.  That leaves no margin for error and may be why the pendulum has swung back to at least slightly overbuilt bows.
 
 It's more of a learning tool for after you have considerable experience.

It sounds like you don't think it's the best avenue to pursue. With 10-12 bows under my belt that shoot ok and a desire to get better performance, what would be your recommendation? After all that's the ultimate goal here is just continue to get better.

  Keep striving to improve your tiller and minimize tip weight.   Reduce limb width as that gets better, shorten the bows relative to draw length or make the working limb shorter....

[Badger]

     The original purpose of the mass theory was to be able to produce good performing bows that did not take too much set. The goal was never to minimize mass. On the contrary it leaned heavily toward making sure we had enough wood to not take excessive set. For example, my typical osage bow 50# and 64" long stiff handles would usually come in around 16 oz. Using the mass principle they now come in between 19 and 20 oz.  Over the years I have found several things in the mass theory that tend to discredit it on some applications while for the most part I find it usually works quite well for me.

     A few years ago I built a number of backed English long bows, some of them were backed with hickory or other white woods while others were backed with bamboo. The lengths ranged from 67" to 72". The belly woods were primarily ipe, cherry, bullet wood, maple, white oak and red oak. With the exception of the red oak which lagged slightly behind the others but still performed well they all shot around the same distance and some of them broke world records in the English longbow classes. What was interesting was they all came out at the same mass weight but the physical dimensions were vastly different. When finished they all adhered pretty closely to the 5/8 rule of thickness to width. What didn't make sense to me was how thick the cherry bow came out when finished.

     Another one I have no answer for is how light deflexed reflexed recurve bows come out, far below projected mass. ( Mark St Louis style) Especially on the shorter versions ( 60" and below).

     And the big one that throws a screw into the whole mess was when I decided to go super wide on some osage bows just to see how they would perform. I was expecting a significant gain in mass weight however they actually came out lower in mass inspite of the extra width. The only logical explanation I can come up with for that is that we may be doing more damage to the wood than we think we are even when it doesn't show up in set.

[bradsmith2010]

cool

[Digital Caveman]

So how well did the supper wide bow preform?  What were the dimensions?  Did it have narrow outer limbs?

Sorry for all the questions, sort of 

[Badger]

     I don't remember now if I chronoed the bow but I did take it out and shoot it for distance and it performed well. I ended up recurving it with big recurves several inches behind the back. I know it ended up taking set after that. I think it was about 2 1/2 inches wide maybe a bit less. The bow had a short working limb area and the tips were stiff and narrow.

[Don W]

well, if anything this has help me understand I still don't understand. But I am definitely going to pay attention to mass and i'll try that "no set tillering" process. I've made a couple bows shot better and are definitely lighter now, but i never was one to shot for average. And I'm way to old to think I have time to do something like build 25 pyramids of all different lengths, about 25 elbs of all different lengths and about 25 parallel limb bows all different lengths. But i guess I can die trying!

[scp]

The easiest way to do "no set tillering" is to build two identical bows with same "no character" material and never bending one bow while working on both of them at the same time. The finished bow that has never been bent will have no set, at least until you start bending it too much.

There are several "perfect bow" designs available online. You can pick one and simply keep on making bows of that design until you "make" it.

Cf. Topic: Best bow design?
http://www.primitivearcher.com/smf/index.php?topic=9274.0

[Don W]

Most of the bows I've built are American flatbows. Parallel limbs about half way looks best to me. I don't like the looks of a wide pyramid bow.

I'm sure i will have one of the "duh" moments at some point, but the theory behind the perfect tiller alludes me. I get that taking off the sides takes more mass than draw weight. But to narrow and wood will crystalize. So it's a tightrope walk between to narrow and to much mass.

I am also assuming there are a lot of game taken with bows that are not necessarily efficient. Speed is secondary to accuracy and weight? I'm sure there is a sliding scale somewhere to show that.

The baffling part is all the videos I've watched and all the texts I've read, it's always "take some wood off the belly" to get the right bend. Yes they mention keeping the tips narrow but never mention the rest of the limb.

[Allyn T]

That's because most people fit tiller to front view shape so you only need to take wood off the belly to work on tiller. You could take wood off the sides if you thought you had too much mass but most folks already have starting dimensions in mind when they shape the bow

[Don W]

That's because most people fit tiller to front view shape so you only need to take wood off the belly to work on tiller. You could take wood off the sides if you thought you had too much mass but most folks already have starting dimensions in mind when they shape the bow

So how do you know what your starting dimensions should be? If it were that simple it would seem someone could post the perfect dimensions and thickness and then you could just follow those dimensions every time for the perfect bow. But that doesn't work, right?

[HH~]

Just had a pyramid I made a year or so ago. Osage 66", 13" non working handle 1/4" at tip and 1' 5/8ths at fade maybe 3/8th thick. Never shot it much and di not hunt it at all. Picked it up and start shooting it and noticed it gained some weight. Blowing arrows right over target. Limbs on this bow weigh nothing but riser weighs a bunch. Very shot working limb. Shoots wonderful.

Guess it depends what your doing with a bow? If your playing games I guess speed helps. If your feeding a family or two or three a selfbow that shoots well without holding it sideways and shoots a 550-600grn arra 125-135fps will kill everything you'll ever need to keep babies smiling.

Hedge~

[Don W]

I don't necessarily call learning to make a better bow, "playing", although I do tend to latch onto something and want to learn enough to be good at it. I can make consistent 130fps bows.

I'm sure all the author's in tbb felt the same

[HH~]

Games is games. Flight, 3d, field, 2d, IFAA, NFAA, WA, games is games. Just like NRA or CMP matches and are called Games Matches.

A selfbow, non backed you shoot over and over and over for years that'll do 135-155fps of any mass with a 500-550 or so grain arra is real quality tool /wpn. Building one of these is not to awful difficult using good wood put up right and tillered out slowly. Prolly not going to do it your first few bows but ya will shortly. Over tens of thousands of shots and years of poking the pucker brush I think it's hard to beat a good elm, take yer pick cept the red stuff.

HH~

[RyanY]

That's because most people fit tiller to front view shape so you only need to take wood off the belly to work on tiller. You could take wood off the sides if you thought you had too much mass but most folks already have starting dimensions in mind when they shape the bow

So how do you know what your starting dimensions should be? If it were that simple it would seem someone could post the perfect dimensions and thickness and then you could just follow those dimensions every time for the perfect bow. But that doesn't work, right?

I base my dimensions on experience based off of all of the bows I’ve ever made and trying to find dimension of bows others have made. I know based off of previous designs that if a wood is a certain density then I will need to make it a certain width based on the design/draw weight I want to make. The thickness is more determined by the working limb length and draw length as that doesn’t seem to vary much across hardwood species. I’m not so nit picky that I’m going for absolute perfection but I’ve been able to achieve low set (<1”) pretty consistently. A couple times where bows have not taken any set I started to remove wood from the sides later in the tillering process and those were with exceptional pieces of wood.  Judging wood based on density can allow you to use new woods with higher success as the other properties of compression/tension strength are usually not a huge factor if making conservative flat bow designs with flat bellies.