Starting dimensions for yew warbow

[WillS]

No doubt leaving excess is the safe choice!  I've only been brave enough to cut to final dimensions on bows I'm not particularly bothered about, or ones I think will blow up anyway due to bad knots, rot etc.  Reasonable tiller success on those ones however, using that method! 

Definitely not something to take seriously when marking out a "proper" bow! 

[Del the cat]

I think there is some confusion here.
I've plotted WillS's average thickness figures. You can see that they do NOT give a linear taper. Thus as I said in my original post, a linear taper is good for roughing out.
The final taper is steeper near the tip.
If you use a linear taper you will have slightly stiff, ugly, heavy tips
I hope this clarifies it.
Del

[WillS]

Remember I'm saying these work for beginning a tiller and roughing out a bow.  I'm not saying you can use that taper calculation to mark out a bow, fit the nocks, polish it and put it on eBay for sale.

For starters, the formula assumes the actual end of the bow stave is half inch, which gives you a thicker limb tip.  Once you've come back far enough to fit the nocks, made it 1/2" there and blended and reduced the limb tip accordingly, you're getting close.

[Ruddy Darter]

Thanks for those tips chaps, I got a roll of scrap wallpaper to draw out a profile to see what it looks like first off, I'll sketch it out  until I get something looking right for a start out plan and then copy the measurements accordingly.


 Ruddy Darter.

[mikekeswick]

I use a linear taper to rough out then I look at how it bends......

[WillS]

+1

Exactly.

[willie]

Will

I have made a few bows with 2:1 taper, and it works well for my needs. Just curious tho, when you do it this way, do you have a different width taper than the average MR? Or you prefer stiffer tips?
 I see that the MR average is just about 2:1., until the last third.....

Perhaps you and Del prefer a different tiller shape?


Shall I presume that the 1800mm bow with a linear taper is to be drawn 32"?

willie

[mikekeswick]

The woods preferred tiller shape is the only way to go! That is predetermined by the thickness/width tapers. Any and every bow irrelevant of overall design recurve,elb anything will tell you the correct tiller shape by showing set as it's progressively pulled further. The wood in the bow doesn't 'know' what type of bendy stick you are turning it into all it knows is the stress it feels as you bend it and the factor that determines how far it can bend is thickness (and the woods own properties). If you deviate from this ideal because you have a set tiller shape in mind then your bow won't be quite as good as it could've been because by definition it will be overstrained somewhere. All this stuff is obvious once you learn to read what the wood is telling you. Once you've 'got it' all bows are essentially the same and you can make any design and know that the 'tiller shape' is correct.

[willie]

Should a warbow  always have equal strain through out the bow, or are there historical designs that call for slightly stiffer handles and/or tips?
Or asked another way, If you are judging strain by set, are you letting the even development of set override the need for the bow to conform to a circular tiller shape, in the final 6 inches of tillering?

[WillS]

I think Mike is spot on.  You can't force a tiller shape onto a bow.

Personally all the linear taper stuff is for starting.  I've had it work extremely well on a few occasions right out to around 28" of draw, at which point the tips required adjusting.

When you say width, do you mean thickness?  The width measurements are always different based on the properties of the piece of wood.  Some yew can take quite narrow width dimensions and some is lower quality and needs to be a lot wider for the same draw weight.  Generally speaking (although certainly not always the case) English yew needs to be made wider than Alpine yew such as the timber used for the original MR bows but you do of course get exceptions.

As for the 32" draw question - it's currently being researched a lot by people like Joe Gibbs and Glennan Carnie.  It was assumed for a very long time that 32" was the sensible draw length for "modern man" as we're supposed to be taller than medieval men.  This is rubbish and has been proved as such, and Joe is now tillering bows only to 30", which is of course the length of the MR arrows.  His results are good, and even people like Glennan who usually shoot up to 34" arrows are dropping down to 30".

Weirdly enough, a lot of the MR bows that were taken from the ship and drawn on a tiller have pretty bad tiller shapes.  Whether that's due to being under water for 400 years we don't know, but I've got a niggling feeling that tiller shape wasn't too important for them.  We're used to making bows today and posting them online and having people criticize them to death for not being perfect and having stiff areas etc with lines and circles being laid over them.  When making them in the hundreds of thousands for livery issue I can't somehow imagine that being the case.  They're all so similar in terms of average dimensions that it seems far more likely that they were roughed out to standard dimensions, rough-tillered and finished as quickly as possible.  They weren't designed to be used over and over and over again so it probably wasn't important.

Just my opinion of course, I may be completely wrong!

[willie]

Will

Whether that's due to being under water for 400 years we don't know, but I've got a niggling feeling that tiller shape wasn't too important for them

Interesting observation about the MR bows.

my question about width relates to tiller shape at the tips with that thicker tip, but is a bit of a moot point if their were quite a variety of tillers shapes found with the MR bows.

Do the MR  reproductions (the ones that tried to be faithful to the original dimensions) seem to be highly strained bows? if they were actually shot at shorter than previously presumed lengths, what would the average draw weight be at say 28"?

willie

[Del the cat]

You can approximate quite simply by assuming draw weight is linear and ignoring brace height.
Take 160# at 32", 160/32=5 pounds per inch.
So at 28" it would be 140#
Note, I said this is an approximation which experience has shown to be reasonable, (so I won't enter into any discussion or justification for my figures, as I have no interest in "having the last word" ).
Also note there were many arrows of approx 28" length on the Mary Rose.
All warbows are by deffinition highly strained!

I think there may be some miss-use of the term "tiller shape". There is the shape of the unstrung bow, and the shape of it at full draw. AFIK the Tiller shape refers to the full draw shape, and of course very few of the MR bows have been taken to full draw. The odd shapes of some of the staves (some have huge recurve) is largely unexplained and debated, this is however not "tiller shape" as far as I understand the term.
Again, I won't enter into any discussion or justification for this assertion, as I have no interest in "having the last word" .
Del

[willie]

Del,

 I appreciate your comments, and am certainly not trying to encourage a debate. I am just a dumb yankee that is developing an appreciation for a famous traditional bow design, and hopefully, some day I can find some yew and develop a appreciation for is enduring special qualities.

Is there room in this discussion for some more dumb questions?

If you were to reproduce a typical MR bow from yew, how much set would be considered normal for the design?

And how much allowance for overdraw,(beyond 28") would you expect the typical MR bow to withstand? would set become excessive @32?  How much set is considered excessive with yew warbows?

I know, the concept of overdrawing a warbow strains more than my mind, I can barely pull over 60 anymore

  willie

[WillS]

Wood quality and bow quality determine much of what you're asking. 

For example, the record-breaking self yew bow that Ian Coote built based on MR bows is 175lb at 32" and Joe Gibbs shoots it at 32" regularly and it's still got some reflex I believe.  There have been MR replica bows posted on here heavier than that with little to no set at all.  There are of course also countless MR replica bows that are much lower in weight with all sorts of amount of string follow.

It's slightly too open a question to answer really.  Some of the MR bows themselves had lots of string follow (we can't know if it's set or just string follow of course) and plenty of them had masses of reflex.  None of it actually matters because even bows with lots of set can shoot well. 

[sieddy]

175#@32"!!!