Yew bow 2nd attempt; tiller help please. Autopsy required

[Justin Snyder]

I think the right limb looks a little stiff in the middle. I would take a few extra scrapes off that area first. The left is looking good.
If you don't get that sucker braced real soon you will wind up under weight again.  It might not be a bad idea to put some super glue on that knot right now.  Justin

[duffontap]

If it were me, I would get it bending out towards the tips more.  It's partially just my preference.  Some of the performance gurus keep the tips stiffer like that, but I think Yew thrives a well-distributed bend.  Again--personal preference speaking.  And, even Yew will kick in the hand if you put too much mass out toward the tips.  Just a little something to be cognizant of.

My main advice would be to round your corners and get it sanded (or very carefully scraped/filed) before you progress further.  This will drop the weight and you can finesse the tip weight down a little while your cleaning it up.  I find that it's better to go through this inevitable loss of weight earlier in the process rather than hit your goal weight and have to scrape and sand 5 pounds off to get the bow looking nice. 

I have never had a problem with a Yew knot--yet--but I would wrap that one to be on the safe side.  That's a stave with some challenges but it looks like you're doing it justice.  Good luck.

           J. D. Duff

[Red Dwarf]

I have  worked the tips some more and rounded things off a little and am starting to develop some limb twist as I draw. Do I remove wood from the side the limb is twisting towards?
Also, I set out the bow as per TBB vol. 1 which gave me a top limb 2" longer than the bottom. I am thinking about reducing it to be just 1" longer. Would now be a good time or should I wait until I am at my weight?

Red Dwarf

[Ryano]

A little limb twist wont hurt any thing in a long bow. I wouldn't recommend removing wood from one side more than the other to correct it, this causes more problems than it solves.  If you must correct it use a heat gun and a form.

[duffontap]

I'm with Ryan.  Leave the twist or heat it out.  I would use steam though.  I've had bad luck with using dry heat on Yew.  It doesn't limber up like Osage does and the heat treated areas wont age to the same color as the rest of the bow so it's blotchy looking.   

            J. D.

[Red Dwarf]

The twist is not really apparent when not braced but develops when braced and more so as the billets are drawn, with both limbs twisting to the same side and therefore pulling the string away from the centre line by quite a bit. I can actually see the handle section rising off of the support block on my tiller tree on one side and the handle slides towards me!
It seems to me that twisting the limbs in the opposite direction would give me a bow with limbs that are twisted when in the unbraced position; something that I do not have now.

Is there any way that I can gauge the moisture content of the billets without a moisture meter?

Red Dwarf

[duffontap]

The twist is not really apparent when not braced but develops when braced and more so as the billets are drawn, with both limbs twisting to the same side and therefore pulling the string away from the centre line by quite a bit. I can actually see the handle section rising off of the support block on my tiller tree on one side and the handle slides towards me!
It seems to me that twisting the limbs in the opposite direction would give me a bow with limbs that are twisted when in the unbraced position; something that I do not have now.

Is there any way that I can gauge the moisture content of the billets without a moisture meter?

Red Dwarf

Limbs twist toward the weaker side.  Could it be that your tips aren't lined up with the handle?

Moisture content reveals itself in string follow...

       J. D.

[Red Dwarf]

Limb tips line up well when unbraced, but both move to the same side when braced/drawn.
I thought that I had read somewhere that the tips would move towards the stiffer side as this side is bending less...? (Just found the section in TBB1 and it does say it twists towards the weaker side. Where's that caffeine?)

I was wondering about the whole moisture content thing and the string follow that I am seeing. I do not have a meter but the billets have been in my dry & heated basement shop for 4 weeks after 22 months seasoning outside. Could they be too dry?


Red Dwarf

[D. Tiller]

Think it would take a little longer to dry them out too much in just a few weeks.  Check the curve of the belly  and verify that the crown down the middle is not veering to one side or the other. This can throw it all out of wack. Also make a blank for the belly crown to run up and down the belly to make sure the crown is staying in the center of the bow.

Before I used a blank to verify the belly's shape I had a lot of problems simmilar to what you are having.

David T

[Red Dwarf]

Dave

I am very new to bow making but think that my billets are too wavy to have a central crown. I am just trying to follow the profile of the back with the shape of the belly. That said, however, it was not until I "rounded things off" that the twist appeared so I have probably rounded off unevenly. Just a little unsure which edge to go after to straighten things out. I know I could find out by trial and error but am fearful of taking too much off of the wrong edge and losing too much weight.
(Just read in TBB1 confirming that the limbs will twist to the weaker side. Now its time to go scrape some more )

Thanks again to all for taking the time to respond


Red Dwarf

[D. Tiller]

Hey Red!

Trust me on the profile, it is really important with the belly. Can I ask how wide the bow is at the handle?

If you know the width of your bow then you have the diameter of a circle. Divide this in half to get the radius. Knowing the radius you can now draw the belly's curve onto a blank along one of its edges. This will show as a half circle. Now cut it out of the blank and you now have a tool to check the radius of the bows belly along its length. If made from a piece of mettle, like a cabinet scraper, you can sharpen the inside to use as a scraper to actually form the bellies profile. Trick I learned from a professional bow builder up here in WA who makes yew bows for a living. Makes sure everything lines up correctly down the center of the bow. Does not matter that the bow is snaky either but an ELB design really needs an even profile along its belly since that is where all the compression forces are lining up. move this to one side or the other and the limb will start to twist.

A flatbow is not as susceptible to this since it is easier to see where it is thicker on one side or the other and remove the wood from there. Its only when you get to more circular profiles that you start having problems like you are having. I had the same problems until I found out about using a blank form to run up and down the limb to check for even curving along each limb. It also makes sure that all those compression forces on the belly Align evenly and this will create better energy storage in this design. (My own pet theory of course! :-)

Have fun with the bow and remember to take your time. All the guys here on this site will also be happy to give you a hand and the benefit of their experiences.

David T

[deerhunter97370]

Red Dwarf, I dont have any advise just wanted to thank you for all your questions about this bow your on. The advise everyone is is giving you will help with problems I expect or can prevent with my next Yew bow. Thanks Joel

[Red Dwarf]

David T

I think I understand the tillering principle that you are suggesting. How would I apply this technique to this particular piece of yew where the back has a number of bumps that appear on one edge only and not right across the back. If I try to maintain an even thickness across the width of the bow the centre of the crown would surely have to move over towards the edge that has the hump?

I am not building (attempting to build) and ELB but rather a bow with a belly that is raised rather than rounded.

BTW the width of the handle section is 1", increasing to 1 1/4" at the fades and tapering to 1/2" at the nocks.


Joel:

I am glad that my floundering is doing somebody some good! I figure nobody lives long enough to make all of the mistakes themselves and must therefore take the opportunity to learn from those made by others.

Red Dwarf

[D. Tiller]

Can you show us a picture of the front and back side of that limb. Dont quite get the picture.

The gauge I use is the thickness of a handsaw blade. In fact it is and old handsaw blade I cut out into rectangles and them draw the half circle on one edge and then cut it out to shape. Use the gauge only on the belly and just run it up and down the belly to verify the curve is correct from Center to nocks. If you see light peak through you just remove the high spots and that should even out the curve across the belly.  If the widest part of the limb is 1 1/2 inches then the radius of your circle will be 3/4" (?). Use that with a compass to lay out the circle on the material that will be your gauge.  Or, change the curve to match your limb design but manetain the diameter, adjust the curve from a circle to more of an elipse to make a flatter profile. Its pretty much just a gauge and you can make it any shape you want. I think some people like more of an ellipse on the belly of their bows and others more pyramid while some like the circle.

At this point it will help you to maintain an even balance to the limbs and true up that problem with the limb twist. It will show you which side is out of wack and where to remove the excess material. What your making sounds still like and ELB but narrowed a bit at the handle like an American flatbow and a rounded belly. Should make a nice bow!

Just remember the bowyers motto "Go Slow!" :-)

David T

[Red Dwarf]

David

Here are a couple of pictures of part of one limb. They show the same section of lims from both sides. Although the focus is not too good you will be able to see that on one side the edge runs relatively straight but on the other there is a pronounced bump in the back.

I cannot get my head around how you would maintain a central crown unless you ignore the profile of the back of the bow?

Hope the pics will help you throw some light in my direction.


Red Dwarf

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