my first BBO bow

[Eric Krewson]

I have made about 50 BBOs, my method is simple.

Draw your finished bow pattern on the belly of the bamboo, cut out the pattern outside your lines and sand carefully to your lines. Thin your bamboo edges to 1/16" from the handle to the tips  keeping the belly flat in the process.

Cut out your osage core leaving it oversized in width. I taper my core from fade to tip and floor tiller it.

Draw a center line on your core, butter up the pieces with glue, line up the bamboo with your core centerline. I like to tape everything together before apply the clamps.

   

When I remove the glue-up from my clamps I use a belt sander to thin the osage to the edge of the bamboo.

I have found no matter how well you line up your bamboo with the centerline it will be a little off after glue-up. I leave my bamboo tips a little wide, sight down the limb and even and center the limbs on a belt sander so I have clean matching limbs side to side with even tapers to the tips. I narrow my tips to a little less than 1/2".

I have found 2 1/2" of reflex on the glue-up table yields an straight limb to 1" or so reflex on the shot in bow.

     

 

[gjkerns]

Thank you, Eric, that is very helpful.  You make is sound *so simple*.  :-)  If I ever make it to 50 bows, maybe I will feel the same.  It's probably the other way around: only people who find it easy ever make it to 50 bows!

Please correct me if I am wrong, but it looked like the bow that Dean built was for shooting off the knuckle (and it looks like yours is too, at least at this early stage).  There's something about this idea that intrigues me, and I am strongly tempted to give this a try too.  I only have cedar shafts 45-55#, so it might mean a headache when it comes time for arrow tuning.  

But Dean didn't seem to be having any trouble... all of his shots were bullseyes!  :-)

[macbow]

I make mine very simular to Erics.
Once tillering is almost complete I then add shelfs as the handle is shaped.
Or shoot off the knuckle.

[Eric Krewson]

I glue on a rest and cut the sight window in about 1/8 to 1/4".

 

[gjkerns]

Here is my current plan for the bow.  The design is based on the closest I can figure from Dean's recommendations. I rounded mine out to 66" from his  65-3/4" so the numbers would work out better.  Note that the upper limb is 1-1/2" longer than the lower limb, because he said it layed better in the hand and was quicker to point-of-aim that way.

   

An open question to me is where the tapers should start.  Right now they are proportionally sized with the longer/shorter limb having the longer/shorter taper.  Dean left that question open, and maybe it's a matter of personal taste.  I would guess that the decision affects strength/stability/hand shock/cast.

[gjkerns]

Here is how it looks laid out on the bamboo.

 

I haven't made any cuts yet.

 

[gjkerns]

The blue dashes on the diagram are the recommended guide marks for the bamboo nodes.  It turns out that for my bamboo there are two nodes equally spaced from the center of the handle (which isn't the center of the bow), and the other nodes are similarly spaced on either side in relation to the marks.  Note that there was only one (1) bamboo configuration such that it worked out that way.  When you try to wrap your head around the unequally spaced nodes on the bamboo, the proportional marks different on each limb, the unequal limb lengths, etc., it's sort of spooky that it all works out just like that, exactly like Dean said it would.

[gjkerns]

By the way, I made my pattern from a roll of drawing paper that was sitting around for the kids to use.  

 

I drew the pattern on with a carpenter's square and covered it on both sides with laminating/contact paper.  

 

Eventually I'd like to transfer the pattern to a length of wood.  But for the time being, this will do.

 

[gjkerns]

Thanks to all for the guidance so far.  Please let me know if you notice any blunders on my part.

[macbow]

What you have should make a,good bow.
There are two schools of thought on doing the shorter lower limb.
I like to make mine even where the center of the bow is the center of the handle. Math and layout is much easier.
Others are in the shorter lower limb so that the arrow pass is closer to the center line.

I've made both and stick with the equal limbs.
I'm sure others will give their thoughts on the two.

Do a search on Bowjunkies and Roy from PA posts using the tillering tree and tillering for equal limb strngth and timing. Use this method for either type of design.

[Bowjunkie]

I like the top limb longer for the reasons Dean mentioned, I prefer how it balances in the hand while carrying, and how it points, cants, and moves braced and drawn... it balances more like an airplane propeller and rotates on an axis at my bow hand's middle finger location, which is where that hand's dynamic fulcrum is for me. This helps make it feel like a natural extension of me.

I also like how it's easier to tiller the limbs for good dynamic balance earlier on in the process because the string hand is drawing closer to bow center. Dean covers this in greater detail in his article "Tillering the Organic Bow" on his website.

Like Dean too, I like a convex taper from dips to tip, as opposed to a parallel inner limb leading to a straight taper to the tips... and lay the bamboo out with this profile after flattening, but prior to thinning and tapering.

BTW, none of that is to infer other ways won't work, just that there are other ways to skin a BBO bow.

[macbow]

Question on method.
Would it be the same if layed out for even limb length. After glue up just cut 1 1/2" off bottom limb.

[Bowjunkie]

Same thing, except you're cutting off a bit of the reflex and pushing the apex of the deflex out toward the tip a little more relative to the limb's length... which might make it look a little odd, or make one limb shaped a different than the other. But it would be minor and wouldn't hurt anything.

I design them asymmetrical from the get go, and glue them up so the reflex is equal and lowest point of deflex is proportional. In other words, even though one limb is shorter, the mid limb posts are both 1/2 way between dips and tips, or 2/3 or whatever.

[macbow]

Thanks