Primitive Archer

Main Discussion Area => Bows => Topic started by: DC on November 24, 2019, 06:45:18 pm

Title: Yew belly grain
Post by: DC on November 24, 2019, 06:45:18 pm
I'm working on a Boo backed Yew that wants to hinge right where this irregularity is in the belly. The belly is flat and the thickness taper is good in this area. I'm treating it like a thin spot and scraping all around to relieve the strain on it but I can't seem to get the hinge to go away. There is no sign of chrysals there, yet. Do you think the wood may be slowly collapsing in this spot? Ever had this happen? More pictures on request :) I'm at full brace and 40@ 24" so I'm running out of wood.
Title: Re: Yew belly grain
Post by: aznboi3644 on November 24, 2019, 06:54:08 pm
Looks like the grain running around a pin knot.  Maybe the fibers arenít in line with the rest and isnít as strong causing the weak point.
Title: Re: Yew belly grain
Post by: DC on November 24, 2019, 07:04:01 pm
You made me go look at it again and there is no indication of a knot. But what I did notice, and you can see it in the picture, at the top the wood is a little lighter colour. That's because it's sapwood. The sapwood dipped in the billet there so when I sawed it out there was still a bit of sapwood there. I didn't think it mattered because at the time there was lots of heartwood. As I tillered I reduced the heartwood until what I've got now is about 50% sapwood in that spot. Maybe it's collapsing.
Title: Re: Yew belly grain
Post by: Weylin on November 24, 2019, 08:48:51 pm
That's interesting. Sorry that it's giving you trouble. It goes to show the difference between yew sapwood and heartwood. I hope you can make it work.
Title: Re: Yew belly grain
Post by: DC on November 24, 2019, 09:27:02 pm
Yeah, I cut a bunch of billets from small diameter Yew trees so in spots the sapwood still shows. I've used it like that before with no problem but I guess it depends how much there is. I'll have to watch that from now on. That's what I get for trying to try to stretch my Yew stash.
Of course I'm still speculating that the sapwood is my problem and that it's not the grain wiggle.
Title: Re: Yew belly grain
Post by: PatM on November 24, 2019, 11:26:38 pm
If those growth rings were laminations what would you expect to happen?
Title: Re: Yew belly grain
Post by: DC on November 24, 2019, 11:53:19 pm
I'd expect them to crush together. That's what I was thinking until I thought of the sapwood thing. My minds still open though. I'm kind of waiting for someone to say,"That happened to me too."
Title: Re: Yew belly grain
Post by: bownarra on November 25, 2019, 01:27:10 am
Straight grain can resist compression because it is flat :)
When you have a dip like that the fibers are no where near parallel with the surface of the limb thus causing a weakness in compression.
I learnt on (on the edge~) ipe bellied elbs that straight grained belly wood is somewhere as near important as a straight grained backing is.
Yew sapwood isn't great in compression BUT I've had it on a small spot on belly lams with no real issues. The problem is the grain or at least most of it.
Title: Re: Yew belly grain
Post by: Del the cat on November 25, 2019, 02:38:35 am
Never had a problem like that. I've had plenty of undulating grain and hints of sapwood in the belly.
Could just be soft spot in the wood, I don't think there is problem with grain direction, Yew isn't fussy.
Rasp out a shallow scoop and patch it.
My 50# boo/yew flight bow that won a comp' had a belly patch !  ;D
Del
Title: Re: Yew belly grain
Post by: bradsmith2010 on November 25, 2019, 09:11:57 am
Try leaving it thicker like u been doing,..if u come in under weight...the bow could still be a shooter...
Title: Re: Yew belly grain
Post by: NonBacked on November 25, 2019, 09:40:54 am
DC Ė Could you take a picture of the hinged limb at brace or maybe at 20Ē? If the hinge is significant at this point, it may have damaged the wood beyond repair.
H
Title: Re: Yew belly grain
Post by: PatM on November 25, 2019, 10:15:11 am
I would just reduce the whole belly and apply an entire new belly and leave  what you have as a core.
Title: Re: Yew belly grain
Post by: DC on November 25, 2019, 10:51:12 am
Let me finish my coffee and get the shop warmed a bit, cold here this morning. Then I'll take some pictures. I'm thinking PatM's idea is what I'll go with. I'm sure a patch like Del suggested would be good but I'm not good at inletting unless it's a flat surface. Curved just kills me. A little confession to make, I've already put on a belly lam because this same limb was giving me problems earlier so it's already a dogs breakfast. My plan this second(could change ;D) is to continue tillering to see if I can rescue this and still keep it above 35#. If that fails I'll grind it down and apply a new belly. Pictures in a bit first.
Title: Re: Yew belly grain
Post by: Del the cat on November 25, 2019, 10:58:11 am
Let me finish my coffee and get the shop warmed a bit, cold here this morning. Then I'll take some pictures. I'm thinking PatM's idea is what I'll go with. I'm sure a patch like Del suggested would be good but I'm not good at inletting unless it's a flat surface. Curved just kills me. A little confession to make, I've already put on a belly lam because this same limb was giving me problems earlier so it's already a dogs breakfast. My plan this second(could change ;D) is to continue tillering to see if I can rescue this and still keep it above 35#. If that fails I'll grind it down and apply a new belly. Pictures in a bit first.
Hmm... maybe the weakness is in the back?
Del
Title: Re: Yew belly grain
Post by: DC on November 25, 2019, 11:09:27 am
It's a Bamboo back, it "should" be good.
Here's some pictures. The last one is about 26#@17"
Title: Re: Yew belly grain
Post by: bradsmith2010 on November 25, 2019, 12:02:13 pm
U can do it,,,, )P(
Title: Re: Yew belly grain
Post by: simk on November 25, 2019, 12:35:36 pm
Sad story - I think it could be saved by Del's or PatM's way. Del's way sure is less work; if you rasp/sand out a scoop long enough its not a big deal and easy to just glue in a thin laminate (max 1/8") with enough pressure - no need to create a precise counterpart. Just put a clamp and epoxy, then cut/sand the excessive wood. The draw weight is low so the patch will hold together.

Imho its the sap creating that hinge; regarding the width of the bow its more than 10%sapwood that doesen't take pressure and maybe even the first heartwood rings next to the sap isnt full developed regarding compression ability...

I did messie yew bellies now more than once and have never had any issues - this bow pulls 60#

Good luck!
Title: Re: Yew belly grain
Post by: DC on November 25, 2019, 02:24:04 pm
I got it to 40#@28" but it looks like this. I thought I would chrono it so at 10gpp I was getting 182 so I lightened the tips and got 185. It's getting a bad launch because there is no arrow pass(shot a hole in the garage door ::)) so that and I can narrow the tips a bit more. But it would still have the ugly tiller. If I got the inners working better(some) and it dropped to 35# do you think it may shoot a 350grain arrow better than 185? I'm still planning a re belly but in the meantime I'm having fun with this. Haven't had fun tillering for a while. Second picture is with one layer mirror imaged so you can compare limbs.
Title: Re: Yew belly grain
Post by: bradsmith2010 on November 25, 2019, 04:04:30 pm
Stop,...u are good,,.its beautiful
Title: Re: Yew belly grain
Post by: DC on November 25, 2019, 04:32:26 pm
Ya think? Here's another overlay. This is unbraced over full draw. It doesn't look like the inner limbs are doing much.
PS Well the first few inches anyway :D
Title: Re: Yew belly grain
Post by: bradsmith2010 on November 25, 2019, 05:17:54 pm
yes they are doing 185fps,, :D
someone told me the other day,, I had never heard it,,
you stop tightening a bolt 1/4 turn before you strip the threads,, wow thats universal,,,
you are 1/4 turn before stripping the threads,, I think,,,, :)

ok now,, if you want more speed,, seems like increase the draw one inch,, would take less work than re tillering to 35,,,
if it does not take set it should shoot a bit faster 10 gpp,, at the increased draw and weight,, but I think you wil be 1/8 turn from stripping the threads,,,, (lol)
Title: Re: Yew belly grain
Post by: DC on November 25, 2019, 06:04:59 pm
I took your advise after a couple more scrapes, I just couldn't leave it like that. Then I rounded off a couple of corners, arrow pass that stuff then chronoed it again and it's 181. It lost a few pounds in the finishing. I haven't looked at the weight. I can't have the shooting machine and the tree set up at the same time. It was to the point where I thought it was better to finish this one and start another rather than re belly this one although I will end up with two bows rather than one and I'm running out of room to hang them. It's about 20 fps shy of my target but i think I learned a few things. I'll check the weight in a bit and then chrono it with a true 10gpp.
Title: Re: Yew belly grain
Post by: DC on November 25, 2019, 06:44:53 pm
It is 39#@28" and a 392 grain arrow hit 187 three times in four shots. The odd one was 185. I'm happy. ;D I tried a 305gr arrow for the halibut and got 204fps. Considering the hoops this one made me jump through I think it turned out well.
Title: Re: Yew belly grain
Post by: bradsmith2010 on November 25, 2019, 07:00:57 pm
Great :OK
Title: Re: Yew belly grain
Post by: DC on November 26, 2019, 01:22:10 pm
First time I've ever lifted a splinter on the belly. OK for a rousing chorus of "I told you so". It's only been shot maybe ten times. No dry fire. I never noticed it until I sanded the belly this morning. Put a drop of CA on it and it travelled about 1/2" to the right so it's a substantial splinter. I'll probably go with plan"B", new belly. Oh well, at least it didn't happen after I put the finish on. Ignore the stain above it, that's just sloppiness on my part. ;D
Title: Re: Yew belly grain
Post by: PatM on November 26, 2019, 01:27:31 pm
Plate tectonics essentially.  Some woods handle this really well, others not so much.
Title: Re: Yew belly grain
Post by: DC on November 26, 2019, 01:44:24 pm
Good description Pat. Here's a picture we've all heard about. The old split a bow to see where the set takes place. It's actually not as bad as I was expecting. And there's no kink where the bad spot is.
Title: Re: Yew belly grain
Post by: DC on November 26, 2019, 01:45:14 pm
U can do it,,,, )P(

Uh, no I can't ;D ;D ;D
Title: Re: Yew belly grain
Post by: bradsmith2010 on November 26, 2019, 01:52:19 pm
well at least you know what kind of performance to expect with a good piece of wood on the belly,,
I think if you had taken my advice and pulled it to 29,, it would have been a bit exciting, and more than a splinter,, (-S
Title: Re: Yew belly grain
Post by: DC on November 30, 2019, 01:52:32 pm
I ground the belly down right to the bamboo from about 10" from centre to the tips and glued on a new 3/8" belly(two pieces) heat treated both sides. It started with 5 3/8" reflex. The tillering was going well until I was just about to brace it. It was 40#@ 17". One last pull on the long string and this time it went 18,19,20 and wouldn't get to 40#. It was collapsing in about the same spot as before. No grain malfunction this time. Since it's in roughly the same spot my first idea was that the bamboo was failing but that doesn't make sense to me. It would splinter or something. To do what it's doing the boo would have to stretch. In that area of the bow the Yew has been tillered down to just over 1/4" thick but it's even. The other limb is the same. No sign of chrysals. Having taken 1/8" off the belly it makes me wonder if I went through the heat treat. All that's left is that I've just exceeded the woods limitations or I've exceeded my talent limitations ;D ;D
Title: Re: Yew belly grain
Post by: Del the cat on November 30, 2019, 02:15:15 pm
Blimey that's weird... there comes a point where you have to think maybe the peculiarity is with the other limb! Maybe it's particularly stiff yew in that limb or someone sneaked in and glued some glass between the boo and Yew   ::) :o
We've all had the odd weird one... I'm stumped.
Del
Title: Re: Yew belly grain
Post by: bradsmith2010 on November 30, 2019, 05:01:06 pm
Wow )P(