Starting dimensions for yew warbow

[Ruddy Darter]

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.

[Del the cat]

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 it’s 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

[Ruddy Darter]

Thanks a lot Del, 

  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.

[Aaron H]

Belt sanders have their place, but can be very detrimental in this game

[Del the cat]

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
Del

[Ruddy Darter]

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.

[WillS]

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.

[Ruddy Darter]

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.

[Del the cat]

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!

[Ruddy Darter]

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 , 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.

[WillS]

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.

[Ruddy Darter]

Ah, that's great Wills, thanks a lot 

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  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.

[Del the cat]

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

[WillS]

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!

[Ruddy Darter]

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 , 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.   
  Ruddy Darter.