Advice please! Bamboo backed Osage - my first piece of Osage ever

[bobnewboy]

Hi All,  despite what I wrote in another thread earlier today, I have actuallly got my hands on some Osage, and I have a couple of nice pieces of bamboo for backing (already ground and thinned out).  So I am set on making my first Osage based bow, with a bamboo back. 

My pieces of osage are 72 x 2 1/8 x 5/8 inches, and 72 x 1 7/8 x 3/4 inches.  The bamboo backs are 1 5/8 inch wide and a little under 3/16" thick between the nodes.

Having never worked with osage before, my question is this: is this enough timber to make a flatbow of 50-60lb draw-weight at 28" draw?  I was thinking of about 66" nock to nock, with a bit of Perry recurve/setback glued in.  I have plenty of other interesting wood to build up the handle area as I think it would be a bit thin when the fades are cut otherwise.

Also, while I'm on  , how should one cook the bamboo backing to get the best work out of it ?  I have an electrical heat gun and I understand that I should heat the bamboo from the centre towards the ends to drive off excess moisture, which also tempers the bamboo.  Is this correct?

Thanks for the help.  I'll post some pics when I'm getting started!

//Bob

[Justin Snyder]

I would narrow the bow to around 1 1/4" at the handle. You have plenty of wood for a 100# bow.    I would add a thin lamination between the boo and the osage at the handle.  I have never cooked the boo on any of my bows.  I'm a little confused, are you going for Perry reflex,  or a reflex deflex style?  Justin

[cowboy]

Hey Bob - I'll be glad to see you build along with it, you'll get a lot of good advice here and so will I. lets go........

[Pat B]

The only time you want to cook boo is as a belly to increase the compression properties but not for the backing.  You want your boo backing no more than 1/8" at the crown, at the fades and handle. It can stay that thick throughout the entire bows length or each limb can taper, thickness wise to the tips. If you taper your belly wood also, sometimes called reverse tiller, you will get a more sweeping bend at glue-up. Otherwise, most of the bend will be in the center(handle area) of the bow. Add about 3" of Perry reflex  at glue-up and after shot in, you should have a bow with 1" of backset or a flat side profile.
Shape the boo backing to almost your final shape before thinning it to 1/8" at the crown or the tips on the final bow will come out too thick.  66"long and 1 1/4 at the fades and a straight taper to 3/8"(or less) tips will give you at least a 50#@28"bow and probably a lot more...100# like Justin said. 
   Keep us posted.         Pat

[snedeker]

At that thickness, you'll have a lot of wood to remove from the belly but that will be good for you.  you will be nice and thick at the handle area and not be prone to riser pop-off problems.  I cut my osage slats to 9/16" to be backed.  Better more than enough than not enough.

Dave

[bobnewboy]

Hi Fellas, thanks very much for the advice.  Not having to cook the bamboo sounds good to me, one less job to do!  Pat, as you can see in the photos,  the bamboo is currently 3/16" thick, and I will cut to shape and thin towards the limb tips (v. good tip because a previous Ipe/BB bow I made was a touch thick at the tips).

Justin, apologies for my confusing text - Pat got it right, I'll try for about 3" reflex at glue-up, and then hope to keep some after tillering and shooting in.  The belly osage will be tapered before glue up, as that worked well when I used Ipe before.  The Ipe bow came out lin excellent shape, "rings" nicely when strung, and shoots very well.  I am hoping for the osage to come out the same or better as my experience improves (I have only made 4 bows!!).

Cowboy, you may expire from waiting for a buildalong with me I'm afraid    I'm not the quickest bowyer, and have to fit it in with other demands on my time - but here's a couple of pix for now - the raw materials and a closeup of the bamboo backing.

Regards, Bob.




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[cowboy]

Thanks Bob - don't worry, I have plenty of time. Post pic's as you go along. Think I've seen this all before, but I glean a little more info every time - just need time myself to get one started .

[bobnewboy]

Next step, I've created a wooden form to reflex the bow during the glue-up.  Two pieces of 4x2, with blocks to holdit together and make it sit upright on the floor when being loaded, if I dont hold it in the workmate.  The curve gradually decreases in radius (i.e tightens) towards the limb tip areas.  For the 66" bow, this should give me 3-4" of reflex, some of which will spring out when the glue-up is released from the form.  The other thing is the marked up bamboo back, not had time to cut it down at the tips or thin it yet.

More when I get on with it   

//Bob


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[bobnewboy]

Rats  , forgot to ask: Justin, why add a lamination between the BB backing and the osage belly slat?  Just for aesthetic reasons, or does it have some function?  If it is for looks, I have some ipe or spalled birch I could put in...hmmmm.

Another question for all you Kings of Osage:  just as a guess, how thick should the osage slat be at the limb tips? I'll leave it the thickness which I already have in the handle area, but need to taper it towards the limb tips before glue up.  I'd guess that tapering the slat with a scraper will take some time - good for the soul but maybe not for my mental health...

Thanks guys!

//Bob

[bobnewboy]

Hi All, 

Here's the next instalment : the glue up.  The bamboo and osage are keyed, cleaned with acetone, buttered with glue and pressed together.  Then I wrapped the loose wood in sandwich wrap film to reduce messyness (I always seem to use too much glue).  Then I wrapped the loose wood in bicycle innertubes pulled tight.  Finally I pulled the whole lot down onto my former to induce the reflex while drying.  I cam to the conclusion while doing this that I had not thinned the osage down enough, but I'll know next time 

Here's the glue up on the former.


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[bobnewboy]

After waiting a week, with the whole lot drying in a warm place (we call it the airing cupboard in the UK), here is the glueup released from the former.  Note that some reflex is lost on release.



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[bobnewboy]

...And here it is after a bit of a cleanup and handle shaping.....Almost ready to start tillering now.



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[bobnewboy]

Oddly, the glueup has gained a camo finish from the glueing and wrapping....Maybe I'll leave it as it is 



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[medicinewheel]

wow...looks like you had a good start on this-one!
frank

[cowboy]

Lookin good so far! I have some idea's and need to get one started soon .