Need help tillering first board bow

[Marquero]

Hi all,

I'm tillering a red oak board bow for my wife.  The draw weight goal is around 30# at 27".  The original board was 1" x 2" x 72" cut on a bias but with mostly straight grain (only one or two growth rings running off the sides and faces of the board).

The bow is now around 66.5" nock to nock, just under 1.5" wide at the fades and tapers gradually to just over 0.5" at the nocks.  I've glued a double thickness riser on for the handle.

I've gotten the bow to full brace at 6.5" and drawing about 28# at 25".  The tiller looks good to me with no obvious hinges or overly stiff sections.  However, when the bow is braced (and even more so when the bow is drawn) the limbs twist in opposing directions.  I've tried to reduce the thickness of the limbs on what is apparently the stronger side (side that limbs are twisting towards) but this does not seem to reduce the twist at all.  My sense is that the twist is being induced by the orientation of the wood grain rather than uneven tiller across the width of the belly.  

Here are some pics of the bow in it's current state...

 
Unbraced pic.

 
Braced.

 
At almost full draw.

 
End view of upper limb at almost full draw.

 
End view of lower limb at almost full draw.

 
End view of upper limb at brace with string aligned with camera.

 
Side view of riser section.

 
Back view of riser section.


My questions for the Bench are these...

1.  How does the tiller look to you?

2.  Is there anything that I can do about the limb twist?  If not should I scrap the bow now and move on, or can a bow with this much twist still result in a good shooter?

3.  Can I feel reasonably safe cutting in an arrow rest as sketched on the back of the handle section?

4.  Is is possible that my nock grooves are somehow contributing to the limb twist?

5.  Any other tips or advice would be welcome!


Thanks in advance for your help.

Best,

Mark

[Steve B.]

Hey Mark,
It seems you understand a lot about bow making and your bow looks good.  I'm not sure about the grain runoff but I don't think that is the issue.
What I notice about the bow is the limbs look too narrow to me.
I would be curious what the limb width is about 12" or so below each tip?
I think the limbs are unstable because they are flimbsy (sp?)
So if I'm right then there's no way to fix it.

If your mid limb width is wide enough you might be able to cut the bow down significantly in length and try to make something of it.

But don't do anything based on what I say as there are others here with more experience.

[4est trekker]

Ditto to the above, but here's some more that may help.

1) Pretty good, although a little flat midlimb on the right limb.

2) Take a look at the post in the link below.  It might be of some help.  However, the bow will probably not suffer too severely from the twist.  Obviously, it stresses on side of the limbs over the other, but there are worse (and quicker) ways to kill a bow!    

  http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=006654  

3) I would NOT cut an arrow rest in...leave it full width.  It will shoot straight and true with properly spined/fletched arrows.  

4) Yes, they could.  However, the twist looks typical of the type induced by favoring a particular side when working each limb.  I've done it dozens of times and have just learned to be aware of it while tillering...adjusting working angles, hands, side of the limb I stand on, etc.  Also, when using the gizmo, I mark the entire width of the bow to help with equal wood removal.

5)  Get this one shooting and then start your next one!  Good work so far on your first bow.        

PS:  At the end of the day, it may just remain twisted.  I've had some bows that, not matter how careful I measured, worked the limbs, exercised them, etc., I still had a small amount of twist.  It's organic and not like a laminated bow.  You might just have to call it good.

[George Tsoukalas]

Don't worry about the twist. It's ok. Enjoy the bow. Tiller is good. But board bows should not twist. I bet if you checked  both sides of each limb you'll see uneven wood removal. Check as you tiller. Look at it or run your hands over it. Now, this one should just be enjoyed and left alone. But to fix it, remove wood from the  strong side. I don't do cut in shelves either. There's info on my site. Jawge
 http://georgeandjoni.home.comcast.net/~georgeandjoni/index.html

[Marquero]

Thanks for the input guys.  

Steve B.:  The limbs are about 1" wide 12" in from the nocks.  I guess I should have kept the limbs full width for a bit before beginning the taper to the tips.  Next time.

4est:  I'll work on getting some more bend in the right midlimb.  Thanks for the link to your pine slat experiment.  It was helpful, and indeed points out that my intuition may have been leading me astray in terms of correcting my limb twist.  So if I'm getting it right, the limbs will twist towards the weaker side rather than the stronger side of the bow and to correct this, one should take some wood off the side that the limbs are twisting away from.  Yes?  

4est & Jawge:  I was pretty careful to make sure to remove wood evenly.  I did many checks by running hands over, measuring with ruler, etc. as I tillered.  I really think that the intrinsic characteristics of this particular board (possibly in combination with insufficient limb width as suggested by Steve B.) is the primary culprit.  I may try removing a bit of wood from the apparent "strong" side of the limbs and see if that does any good.  Otherwise, I think I'll follow your advice and get her shooting.  By the way (and I know that this horse has likely already been beaten to death in numerous venues) what is the short version of your reasoning behind not cutting in shelves?

Thanks again for sharing your valuable experience with all of us newbies.  In fact, a great big thanks to all of the folks that contribute to and participate in the Bowyer's Bench.  I haven't posted here much, but I'm an avid lurker and I have learned so much from you all.

Best,

Mark

[George Tsoukalas]

That's sure possible assuming the nocks are evenly cut. I've had that happen. Was the twist there before you started tillering? Jawge

[Marquero]

Jawge:  The twist is and always was only apparent when the limbs were bending.  The original board was very straight.  At rest, the limbs are and always have been straight.  At brace, and higher, the twist becomes more and more evident.  Since the twist is only induced by bending, and since I did some tillering before I got her bending, I only noticed twist after starting the tillering process.  

Mark

[George Tsoukalas]

I'd just leave it. You have a working bow. Twists are rarely a problem. What I used to do was was favor one side and then the same side on the other limb so I'd get a prop twist on a straight stave.

I remember working on a yew stave. Yew doesn't grow on trees here so I was very careful with it. I even checked with calipers to make sure wood removal was even on each side of each limb. I should mention this stave was straight before starting. Sure enough it twisted on the first stringing. I fixed it by removing wood from the high side.

I've made tons of bows with twists and unless the twist is more than 30 deg I'm ok with it. Check this.

Heat is an option.


 Jawge

 http://georgeandjoni.home.comcast.net/~georgeandjoni/index.html

[Marquero]

Update on my first attempt at a board bow:

Thanks to the advice posted above, I was able to reduce (but not entirely eliminate) the limb twist by taking some wood away from the strong side of the limbs.

Against the advice posted above, and at the urging of my wife (the intended shooter of the bow), I went ahead and cut in a shelf.  

The bow seemed to be fairly well tillered and was flinging arrows fairly nicely so I decided to go ahead and scrape, sand and finish with tru-oil.

Here are some pics.

 

 

 

 

 

 

 

 

I thought that the bow was looking pretty good until...

[Marquero]

...I noticed these...

 

 

 

There are three small cracks running across some of the exposed early-wood areas along one side of the upper limb.  These cracks run perpendicular to the long axis of the bow.  One is in the outer portion of the middle third of the limb and the other two are a few inches from one another in the inner portion of the outer third of the limb.

So my questions for the Bench are these:

1.  Should I give up on this first try and move on?  

2.  Assuming that is not possible (as I'm pretty hard headed when it comes to finishing a project), can I make the bow relatively safe to shoot by repairing the cracked areas?  

Note: My repair plan would be to saturate the cracks in super-glue then wrap the limb area around the cracks with hemp/jute/serving (for about 1 - 1.5" in each direction) and saturate the wrap with super glue.

3.  If I attempt such a repair, is it necessary to sand/steel wool all of the tru-oil off the repair area?

4.  What is the preferred material for wrapping?  I like the looks of organic fiber materials such as hemp, but string serving material seems to be stronger.  Is there enough strength imparted by the super glue to make the wrap material choice less important?

5.  What do you think caused this cracking?  How do I avoid it in the future?

Thanks again for your help and advice!

Best,

Mark

[vanillabear?]

[Marquero]

Cracks are on the back of the upper limb.

[macbow]

If they were on the belly they'd  be called crystals.
And would be serious .

My suggestion would be,to put a backing on the bow like rawhide.
Linen or even brown paper has been used.

The wrapping of thread or sinew would be ok but it looks like they are rather far apart.

What ever you do . Both limbs should be done the same..

If you want to try rawhide and need some contact me and I'll send you some.
Ron

[vanillabear?]

[macbow]

It looks like you have put a lot of effort into this bow.
It has very good lines.
So it is,worth saving it at this point.
Red oak is easy to get and makes great wood to practice with.
There are others here with more experience with it but I don't think it is real strong when it comes to tension for the back.

You would,have to sand all the finish off to glue any type of backing on.

[Black Mockingbird]

Those are tension cracks...u need to pay attention to any little "ticks" you hear whenever making,pulling,n shooting all wood bows. I'm sure it made them whenever you were pulling it. As soon as you hear it,you need to immediately inspect the bow thoroughly(sunlight is best),and unbrace it,and not continue to pull it cus its a ticking time bomb and will explode. You can either wrap those areas with sinew,rawhide,serving,but your best bet would be to back the whole thing with rawhide,linen,or silk. I wouldn't use paper bag or sack like materials...rawhide or high grade silk is your best choices,and I highly recommend those only to protect those tension cracks if you wanna save this bow. And if your using a glue like titebondIII you won't have to sand off all the finish,just give it a quick rub down and decreasing with acetone or denatured alcohol.

[PEARL DRUMS]

Just to be sure we are together here. The back of the bow faces away when your gripping it, the belly looks at you when your drawing. These are on the back surface? Never seen that before, not without a splinter immediately popping up.

[Steve B.]

I had that same small crack on my last bow which was a vine maple shorty and stressed.  It has a matching crack acrossed the limb on the other side.  I was sure it was cracks.  And it was on the back at the most bendy point.  I shoot it anyway but I'll probably back it as mentioned because my nerves can't take it and a lot of work went into it.

[Whitehawk23]

Ok so what happens if you have those cracks on the belly? How do you fix that?

[Marquero]

Black M.:  While exercising the bow after taking some wood off, I did notice some very quiet "tick" noises.  I inspected the bow after hearing these and did not see any cracks or splinters.  However, when I started to finish the bow with tru-oil, these hairline cracks appeared.

Pearl D.:  We're on the same page.  The cracks are on the back (tension) side of the bow.  Not on the belly (compression) side of the bow.  Just hairline cracks.  No splinters.

It sounds like I should seriously consider backing the whole bow.  Any good sources for suitable rawhide?

Thanks tons for all of the advice and input.

Best,

Mark