Primitive Archer
Main Discussion Area => English Warbow => Topic started by: bershirebowmen on November 03, 2015, 12:07:47 pm
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Greetings all,
I'm in the process of reworking an Italian yew warbow. It was meant to be 162@32 and is 81&1/4" long. I found the bow to be very whip ended with little movement in the inner limbs and no movement in the centre, it stacked terribly and stress frets developed on the mid outer limb around knots and were becoming a concern. I also coud not draw it past 28" which was disappointing me after training hard to do so .I took some wood off at the centre and inner limbs to take off the stress(quite a bit)/and got it moving throughout the bow and weighed it and I got 160@31"!?! Anyway I've decided to shorten the bow to around 78". I' also going to steam it straight (doesn't need to much) and maybe temper the belly too with a heatgun sometime after, then retiller from again from scratch(and narrow it some, its 42mm wide at the centre), That's the plan. One question I have is about a knot mid outer limb. It's been left bulbous on the belly and was causing it to fret above and below, I've reduced it some which took out some of the stress, is it nessescary to leave it so built up on the belly?, sorry I can't seem to load a pic. (Edited my terminology: inner limb for lower limb(closest to centre). Outer limb for upper limb, furthest from centre).)
Berkshirebowmen.
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Managed to resize pics,
(Also 4" of the bottom limp tip looked in danger of snapping if I could of got a longer draw from it)
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Different people have different opinions on leaving knots proud on the belly. I've personally found that as soon as you get into the serious weights ignoring knots or even pins on the belly is asking for trouble.
I've had this happen once too many times to ignore belly knots now - this is on a 125# self yew and I left it thinking it was far too small to even consider.
(http://i1202.photobucket.com/albums/bb363/Will_Sherman/FB_IMG_1437777547057_zpslygxivbe.jpg) (http://s1202.photobucket.com/user/Will_Sherman/media/FB_IMG_1437777547057_zpslygxivbe.jpg.html)
So I would say always leave a small bulge both back and belly around knots, no matter how small they are.
I assume by your description of the original tiller it was a certain C.P. made bow?
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Yep your right, anyway these pics are after I've reduced it, and seems to of reduced stress, now on to straightening and shortening. Thanks, I'll leave it like this for now then
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Ome more pic of the belly view
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IMO The reason that pin in WillS's picture caused a fret is because or the bark inclusion around the pin. The bark has no compression strength, so the pin is like having a hole in the bow... that's why I pick out any black manky bark stuff round the pin. The actual pin then often just falls out. I fill with either wood or wood dust epoxy mix.
Now't wrong with leaving a very slight bulge, but surely it's better to solve the problem than trying to cure the result of the problem.
I'd say look at the grain of the wood and follow that.
In your first pic, the extra thickness is IMO ludicrous. Bear in mind that stiffness is proportional to the cube of thickness.
Measuring from the pic the limb thickness to the left of the knot is 23mm and at the knot it's 30mm. That gives the knot a relative stiffness off more than twice the rest of the limb (comparing 23 cubed vs 30 cubed). That is self evidently bonkers and simply creates a relatively weak spot either side of the bulge inviting chrysals there. The whole bow should be in harmony, not a series of alternating stiff and weak points.
I think it's a matter of degree.
I'm not saying that leaving a little extra is "wrong".. but I'd suggest either a very little extra thickness or better, simply leave a tiny bit of extra width, (or leave the belly a bit less rounded at the pin) extra width has the advantage of increasing the amount of sapwood on the back, which is where the real problem is. Chrysals don't often cause bows to explode... weak points on the back do make 'em explode.
I've seen plenty of Warbows from plenty of big name bowyers and some have horrendous pinches alongside un-plugged pins.
You have to take which advice works for you.
I'd generally advise not shortening a heavy bow if you can avoid it... length is your friend as it reduces the stress.
All just my opinion of course, other opinions are also available, terms and conditions apply, contestants must be 18 years or over ;)
Del
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Thanks Del, advice taken on board ;D
I see what you mean about it over stressing above and below, I had the similar bulge on my 140, and I think it made a weak point just under and maybe contributed to a sap wood splinter occuring 2 inches under(?) and the 8" above to the nock is curled over in a backward set, my main bow out of action :-\, thanks for advice, I'll have a ponder on what to do, 160@31 is too much for me, I'll have to have a think on what to do, I was thinking of shortening and narrowing the bow to avoid it looking like a fat flat bow if you know what I mean due to it being so wide, also i may of gone a little thin below the knot to even out the tiller, looks a little a skinny there now.I'm not fussed about the bowweight it comes out at I just want a functional reasonably heavy bow ( and being 5ft 6 inches with a 6ft 9 inch bow does come into it :)). Thanks for advice about making it wider around the knot, that was something I wished to question about as one of those two knots is quite close to the edge on the back, wasn'tsure what to do there if I narrowed it some.
berkofabowman
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It's slightly odd re-tillering a bow. You almost have to start from scratch. Reduce it to some sort of clean even taper, decide on a target weight and work towards that getting the tiller even being the first priority.
I'd say set yourself a definite target weight that is withing the amount of wood you have and your physical limit.
Don't worry about the bow being a bit wide, wide and thinner gives a better safety margin IMO.
Del
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Thanks Del, I'll give that a go, I wish I'd done that to start with instead of a quick fix attempt to sort it out, I may of lost a lot now compensating for that bulge, the string doesn't run parralel when strung, more gap towards the top limb at the handle, just hope I haven't buggered it totally, if I have I might be taking up golf :-\
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You should have plenty to play with... better to have a well tillered 95# or 110# than a badly tillered 160# that is an accident waiting to happen.
Slow and steady wins the day.
Gotta remember the golden rule... when in doubt stop (and drink tea :)), and even when you are sure remove half as much as you think you should... ::)
It makes for slow tillering, but you get a decent bow ... eventually :laugh:
Del
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Thanks again, 8) will do, although I'd prefer to be shooting with my spare time, to the garage it is then and not the field :-\
Berkman
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Good advise as usual from Del.
Patience is a must for a bowyer. If you don't have it, your going to have problems.
Even those with it get tested often, and yes tea helps!
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Thanks meanwood, and thanks again Del, you've been a real help. I feel I know what to do now to best sort it out. I was wondering about a 7" section below the centre line that was also left bulky, there's no knots there so maybe that was to act as a counter balance to the extra wood around the two knots on the top limb?(pictured) that's another weak spot underneath that section to sort out, and think that's lost a lot to this bow.
Berkman.
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I don't really understand what you are saying ???... What centre line? You can draw a centre line across the bow at the geometric center which is roughly where you hold it, or you can draw a centreline along the back or belly from nock to nock, or you can draw a centreline along the side of the bow midway between back and belly like the line you'd get if you glued a back and belly of equal thickness together.
So that's 3 possible centrelines!
And don't even start me on what you mean by "below".
You need to be very careful with your words, or better still draw a sketch, scan it and attach it.
Del
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Sorry Del, I meant the line I mark on across the bow where you hold it, should of explained that better. ::), here's a pic , it was more but I've reduced it considerably, on the belly starting just above the arrow pass (masking tape) and heading south 7 or so inches with a sloping step down into the continuing limb( doesn't show so much because Ireduced it) bottom limb is facing downwards.when I reduced that section the the balance of weight towards the top limb increased a lot, that's why I questioned it, it was, and still is a bit, a very static 8"-9" section .
( sorry if I'm not making sense and don't worry about it , I think I will shelve it at the moment and leave it alone for a while, I'm probably writing what I'm thinking which is never a good idea)
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I normally leave a bit of a bulge at the grip.
Del
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O.k. thanks Del, this was quite pronounced before reduction and I think better now. I've stopped stressing about it and feel a little more optimistic, I think I've been snowballing issues the more I stressed. Took a step back and made a plan of action as recommended and came to the conclusion I may not get it perfect but as long as I take it steady I will improve the bow more to my liking, not dreading working on it but looking forward to it now.( I swapped my coffee for tea which I think helps when pondering. :D)
Thanks again and will post pic and vid with work on the tiller.
Berkman.
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Here's where I am on the tiller after my first original removal of wood, a skim off both sides and the belly with a surform two thirds of the way up both limbs (including centre) as even as I could. Its on a 25" draw. The outer limbs have not been touched. Im working from the centre outwards to even out the limbs and then draw it to 30 after and see what it looks like from there. The top limb is to the right.Thanks for any input or advice.
(Just using a scraper from here on)
Berkshirebowmen.
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We need to see the unstrung bow shape, as presumably that kink near the left tip is there in the stave anyway?
It looks like the inner and middle of each limb isn't doing much yet.
take thickness measurements every 6" just to help check for even thickness taper and rough symmetry (lower limb should be a tad thicker at all points) Even if you don't worry too much about the actual measurement, locking the calipers at one point and then running them along the limb allows you to watch the gap between the jaws and the bow open up as you go along and so helps show any thick spots.
You can get digital vernier calipers pretty cheap (about £30), and mechanical ones even cheaper (about £6).
You really need to get a scale on there to measure draw weight, fishing scales are relatively cheap online.
http://www.ebay.co.uk/itm/like/301255889005?adgroupid=13585920426&hlpht=true&hlpv=2&rlsatarget=kwd-75951445986&adtype=pla&ff3=1&lpid=122&poi=&ul_noapp=true&limghlpsr=true&device=c&chn=ps&campaignid=207297426&crdt=0&ff12=67&ff11=ICEP3.0.0-L&ff14=122&viphx=1&ops=true&ff13=80 (http://www.ebay.co.uk/itm/like/301255889005?adgroupid=13585920426&hlpht=true&hlpv=2&rlsatarget=kwd-75951445986&adtype=pla&ff3=1&lpid=122&poi=&ul_noapp=true&limghlpsr=true&device=c&chn=ps&campaignid=207297426&crdt=0&ff12=67&ff11=ICEP3.0.0-L&ff14=122&viphx=1&ops=true&ff13=80)
Del
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Thanks Del,
That bottom limb end is a slight natural kink compounded by a tadge of set, I'll get a pic of it soon as i can. The limbs are pretty even in depth...i dont know if you can see in the pic but ive got it marked off every six inches with a strips of masking tape folded over the sapwood edge and marked a dot with a pen. I've got fishing scales, although I'm not going for a weight, by the time I get the limbs working even it might be near what i want, im drawing it to the side of my face as it is and i want a heavy bow to get on top of, as long as its working properly. Ill get that pic..
Berkshirebowmen
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Here's a couple of pics, the sapwood propellers a fair bit on this bow, as it does at this end, so heartwood is a little varied viewed from both sides.(the bow isn't strung) and me drawing it to 31+, hard work and a bit shakey, gave me a rope burn pulling that down :D
I've taken a fair bit off so you can apreciate how whip ended it was.
Berkman.
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That bend looks pretty good (allowing for the kink at the left tip) :)
Del
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Your hair has given your identity away :P I couldn't think of anybody else from your area who had a Poletti of that weight!
I think the tiller looks good. There still seems to be something odd happening mid-limb on both sides, but it doesn't look problematic. That's the sort of thing that softens up as it shoots anyway.
Nicely done mate.
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Thanks Del 8), I'm wearing a wig WillS ;D
Yep agreed, I'm going to lightly scrape the mid lower limb to get a bit more movement (and I think that kink will show less (?)) , I can see where the wood's a little thick there. And reduce around that knot area on the mid top limb and get some more movement and I reckon that will be just right, not too much though I think the wood has got used to bending around there. Should weigh around 155+@31" I reckon now.I was a little worried I took to much off the centre but it looks o.k. to me. Well happy days...I didn't muck it up after all, :)
Berkman.
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I'm scouring your photos for signs of a Shillelagh, then I'll know for sure... ;)
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(Lol, that lot all split to blazes,errr...someone told me, :D)
I was wondering what ideal arrow weight for this bow, I got some stout 80g-83g with type 10's, sound about right?,
Berkman
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What weight are the Type 10s? If they're Hector's they'll be quite chunky, and if they're made by Milos they'll be super duper light - or that could be just me, cos I keep nagging him to make them lighter.... He made me an 11g half inch Type 16 the other day. Phwoarr! Great on light aspen shafts, but a bit twitchy when you put them on something like ash or birch.
155lb is a good 30lb above what I shoot though, so I'm "shooting in the dark" so to speak.
80g sounds reasonable for roving or target shooting though. 60g is still safe out of something like 180lb, so you've got plenty of room for experimenting.
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Thanks WillS, I got Hector Coles. Rather them a little heavy ( 80g-83g is the finished 6 arrows with them on). Took a bit off where I said and burnt in an arrow pass, I'll have a look again tomorrow but I reckon it's good enough for me now. A happy conclusion. I don't think there's much I can do about the kink in the bottom limb tip, atleast there is less stress there now. Happy I managed to keep the profile as round as I did. I won't do any steam straightening, probably mess up what I got..quit while I'm ahead. :D Thanks for all the help and advice, spared me taking a longer road to get to a poorer destination. 8)
Berkman.