Primitive Archer
Main Discussion Area => English Warbow => Topic started by: Ruddy Darter on March 18, 2016, 08:08:29 am
-
Hi all,
Could anyone offer me starting dimensions for a 135-140@32 self yew, approx 78-78&1/2" in length?, my main concern is the tapers & length of tapers and when they start from the nocks, I'm leaving it equal 6" up and down from the centre..I presume this is correct for the hand grip area? A rough idea would be great.
Many thanks for any help,
Ruddy Darter.
-
Here are some dimensions for a finished bow:-
Dunno if it will attach as a word file.... nah, doesn't seem to work
I usually go on a thickness taper of about 1.5 to 2mm every 6"
Here is the txt... but of course the formatting is messed up. hope you can make sense of it
Yew Warbow 76 Ύ nock to nock. ~ 120# @32 DH 18.01.2016
Dimensions taken every 6 with manual Vernier to nearest 0.1mm estimated.
Note:- Lower limb belly heat treated over inner 2/3 of its length.
Upper Limb Lower Limb
Width mm Depth mm Width mm Depth mm
CENTRE 38.8 32.2
6 38.8 30.0 39.0 29.5
12 38.5 27.5 36.3 27.4
18 32.4 26.4 34.4 25.9
24 30.0 23.6 31.8 24.0
30 25.5 21.5 29.1 20.8
36 17.8 17.5 19.2 17.9
Base of horn 12.2 12.2 12.7 12.7
This is final dims... have to make allowance when roughing out, and differences in wood, overall length etc.
Bottom line is you can't make one by numbers, but it can help you get close.
Del
-
Thanks a lot Del, 8)
It's a rough idea I'm after for a starting shape and that's most helpful, I'll draw out a diagram of these dimensions to get a better idea. Going to buy a belt sander with extraction dust bag first off, thanks again and much appreciated :)
Ruddy Darter.
-
Belt sanders have their place, but can be very detrimental in this game
-
Belt sanders have their place, but can be very detrimental in this game
+1
I only use them in the very final stages for cleaning straightening the sides/edges of a warbow especially the tips where I leave plenty of extra width early on to help stop sideways bend and to to allow room for string adjustment.
My Youtube Warbow build along is worth a look if you haven't seen it. It is the bow that I've given the dimensions for.
https://www.youtube.com/playlist?list=PLBz2tD9476KRkSOSICLsc-zj5ADyPKLZB (https://www.youtube.com/playlist?list=PLBz2tD9476KRkSOSICLsc-zj5ADyPKLZB)
Del
-
Yep, sorry I should of added that's what I wanted it for, finishing the sides nice and even and for the knock ends on a fine grade belt. Cheers,
Ruddy Darter.
-
I did an average of every Mary Rose bow in Weapons Of Warre dimensions a while ago, and put them on a post on Facebook, but they're committed to memory now so this might help a bit:
Centre - 35mm wide x 33mm deep
100mm from centre - 35mm x 32mm
200mm - 35mm x 30mm
400mm - 31mm x 28mm
600mm - 28mm x 25mm
800mm - 20mm x 20mm
900mm - 16mm x 16mm
That's a set of "average" dimensions from MR bows, so all things equal and using extremely good quality European yew you'll end up with something in the 150, 160lb range. Using "normal" yew it should be spot on for something around 130/140lb. That's finished dimensions of course, so add a few mm to everything for tiller adjustments.
-
Ace WillS, thank you very much,
I may aim for 76"bow length, maybe as short as 74" to avoid a dodgy kink in the bottom limb tip, so I may go for a slightly lower draw weight, see how it goes :)
Many thanks,
Ruddy Darter.
-
Just a note of caution!
It's easy to get confused with MR dimensions as they are NOT given at EVEN intervals!
E.G. They are not every 100mm or every 200 mm!
bad scientific practice IMO... that's why I do it every 6"
Del
@Will... Fine work averaging out all that data!
-
O.k., thanks for that tip Del, I was going to do every six inches with 35-37mm wide at the handle, but nice to have those dimension averages to correspond with 8), off to look for some measuring callipers now, they got a digital set in Homebase for £12.99. Just found a couple of predrilled horn nocks 14mm in diameter..should be o.k.?
Ruddy Darter.
-
A really nice way of working out an actual taper for each limb (if you want to get all mathematic instead of using instinct / feel etc) is to take the overall length from tip to centre in mm, divide it by the difference between centre thickness and tip thickness and that gives you the measurement in mm for each mm you drop.
For example :-
76" bow = 38" tip to middle
38" in mm = 965.2mm
33mm thick in the middle, and 16mm thick at the tip is a difference of 20mm
965.2mm divided by 20mm = 48.25mm
That means you mark a point every 48.25mm from the centre, and each time you get to a new mark you take off 1mm from the thickness. That is to say, you start at the middle with 33mm in thickness, mark a point 48.25mm away and make it 32mm in thickness. Then mark a point 48.25mm from that and make it 31mm and so on.
This works beautifully with reasonably clean staves and if you're brave enough to cut the bow out to exactly those marks you normally get an almost perfect tiller without doing anything at all to it. That's as long as the wood itself doesn't throw up any surprise areas of dense/less dense material which changes the properties and so on.
-
Ah, that's great Wills, thanks a lot 8)
That gives me a real good picture of what to look for and hopefully cut out a fair bit of dust making, I'll mark it out a couple of mm oversized with the method you have shared .COOL ;D I'm going for 74" in length, maybe 75" and I'm not chasing a weight but hopefully around the 130lbs@31". Your help is very much appreciated. :). Ta very much guys.
Ruddy Darter.
-
Oh dear... I'm may appear argumentative here :-[
Be wary... working out an even taper is fine for ROUGHING OUT... but beware, the outer 1/3 of each limb tapers at a faster rate to give that Spitfire's wing look that the MR bows have.
Where the knocks fit, you don't want to more than 1/2" (12.5mm) diameter.
If you plot actual limb thickness I think you will see it's not an even taper.
Del
-
Works for me ;)
It's how I've been doing it for ages now. I've had a couple of bows since doing it that have gone on the tiller for the first bend on the long string and I've not touched the belly for adjustments until around 28" or so at full brace.
Everybody does it differently though!
-
Good point Del and thanks for bringing that up, I was just thinking that myself, although I will use this method from 6" from centre to 6" from the nock, I'll have a separate sharper taper there and play it by ear, I'll scan through all the dimensions given for a nice starting shape giving myself some play room for error.
You just beat my post WillS ;D, I don't doubt it will work well WillS for you, but I'd better give myself a margin of error for my novice disposition. :D
Ruddy Darter.
-
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! ;D
-
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
-
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.
-
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.
-
I use a linear taper to rough out then I look at how it bends......;)
-
+1
Exactly.
-
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
-
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.
-
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?
-
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!
-
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
-
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
-
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
-
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.
-
175#@32"!!! :o
-
Yeah, nothing unusual about that any more, and that's with natural hemp strings, too! His 175lb laburnum bow is quite a looker as well.
-
Hemp strings! :o
-
@WillS: It΄s a very interesting hint, that there are experiments with 30" arrows now, which show that 30" seems to be the best draw lenght for Mary Rose bows. Do 30" arrows have a higher velocity or a better penetration than 32" arrows? How do the light weight 28" arrows perform?
It always seemed very odd to me that most warbow archers now use longer arrows than in the 15th and 16th century. Recently I read an interesting german study on body hights in earlyer periods. The average body hight of a man in the 16th century in the southern Germany and northern Tyrol would have been about 167 cm, people from northern Germany and England were about 171 cm tall. Having only facts like these, people from today would assume shorter draw lengths for archers in earlyer periods. But interestingly, previous people often had different body proportions. Their legs were often shorter but, the upper body was just as big as today. I even read somewhere that the arms were as long as today or sometimes even longer. The different body proportions come from hard physical work during the age of growth.
-
I think it's more the fact that a bow tillered to 150lb at 30" is far less stressed than a bow tillered to 150lb at 32". The wood stays healthier, therefore the performance is better.
I suppose when somebody decides to document it, or do some extensive testing we'll know for sure.
-
Why do these bows have such a long parallel section, and then a sudden extreme taper at the tips?
That's how it looks to me anyways
-
I think it's more the fact that a bow tillered to 150lb at 30" is far less stressed than a bow tillered to 150lb at 32". The wood stays healthier, therefore the performance is better.
I suppose when somebody decides to document it, or do some extensive testing we'll know for sure.
If you make the 32 inch draw bow a wee bit wider or longer it isn't more strained. The aim on all bows should be to make them feel the correct strain for the wood at full draw. Be that 30# 50# or 150#. Wood doesn't know what bow/design it is in - it just feels the strain upto its limits then fails if we push it past.
A longer draw on the same bow/same arrow makes it more efficient.
-
Why do these bows have such a long parallel section, and then a sudden extreme taper at the tips?
That's how it looks to me anyways
Parallel, because they are narrow to start with, and if you go too narrow too quick they can bend sideways. The thickness tapers so the width doesn't need too.
They taper quickly and gracefully at the tip because they can, and it saves weight. I see very few bows that couldn't actually be thinner at the tip. I see plenty where they look like pencils at the end, where the horn nock has been fitted but there has been no attempt to blend that into the limb. Bear in mind you are going from a circular section at the nock to a D section in the limb, if it's not done nicely it looks hideous!
Here's a post that shows what I mean...
http://bowyersdiary.blogspot.co.uk/2014/02/back-patch-and-tip-tidy.html (http://bowyersdiary.blogspot.co.uk/2014/02/back-patch-and-tip-tidy.html)
Del