Bamboo backing

[lignum]

Hello Everybody,

I want to back my bow with bamboo to make him stronger.
The bow is made in ash, 65" long, 1,7" wide by the fade outs and 0,5" by the tips.
he pulls actually 40lbs. It´s a selfbow with light recurves and has actuall a set of 1"

My questions are:

How thick has to be the bamboo by the fade outs and by the tips?
Which is the best glue?
Should I glue it with stressing the bow in a reflex?
With how many pounds increasing I can messure with the backing?
Anything else?

Thanks in advance
Lignum

[Pat B]

  To bamboo back a self bow you will have to decrown(flatten) the back first so you have good surface contact with the flattened bamboo. The bamboo should be about 1/8" at the crown near the handle and can be flat or tapered to the tips. Urac glue or TiteBond glue work well for bamboo backing but others will work also. Perry reflex(added reflex during glue-up) will add considerable weight and performance to your bow.
   Now, after all of that, you would be better off starting a boo backed bow from scratch. You will have better results. Keep your other bow as it is and if it is too weak for you, give it to a friend that doesn't have a bow.     Pat

[Justin Snyder]

I like a guy that addresses all the questions before he starts.  I have never backed ash with boo.  I think a hickory backing might be a better option.  If you do want to use boo, you want it super thin.  After the profile is cut out, thin it down to razor thin at the edges at the fades and maybe 1/16 or less at the tips.  Anytime I back a bow I add about 3" of Perry reflex.  I like to use smooth on, but any of the glues used for bow making will work for this. Its hard to say how much weight you will add.  How thick is the bow now?  Realistically, by adding a 1/16" backing you could double the weight.  Justin

[Justin Snyder]

I guess I could have known Pat would be posting while I was typing.  Justin

[lignum]

Thanks Pat,

if I understand it right, I can flat the bamboo to the tips , or let it in that thickness.

I unserstood your idea to start a new bow. O.K. I will think about it and let you know.

Another questions. Does it gives a formular , like the wood for the belly has to be thick about that, that you get roughly 50lbs draw weight bow by using 1/8 bamboo for backing?

Usually I use for my bows ash or locust.

Regards
Roger

[lignum]

Hello Justin,

the bow is by the fade outs roundabout 0,78" (2cm) and gooes to the tips down to 0,39(1 cm).

Hope my inches are right calculated, because I messure normally in metric system

regards
Roger

[Justin Snyder]

Formula?? If I understand the question correct.  No there is not a set formula for how much weight you will gain by backing the bow.  There is too much difference in the density of the backings and the belly wood.  I read that the general rule for backings is, the backing should be less than 1/2 the thickness of the belly wood. Justin

[lignum]

Thanks Justin,

is fine to me, because the backing I worked out is about 3-4mm. The stave thickness I started is normally 2-3cm. So I´m more than less of the half backing to belly

Regards
Roger

[Badger]

If I am working with a dense tropical wood I use the boo thicker, if I am using a lighter wood, below 75 sg, I try to get the boo below 1/8 at the crown. I really prefer boo on denser woods. Steve

[Justin Snyder]

Bamboo is a really strong backing.  You want it super thin.  Your math is correct on the cm to inches.  2-3 cm is pretty thick. What thickness do you usually end up with?  Justin

[markinengland]

As a rough guide you can say that a backing will add ten pounds draw weight and each inch of glued in reflex will add another ten pounds. This will vary on how thick and strong the backing is, the belly wood, the bow length etc but does work out quite well when I have tried this.
You can see why the perry reflex works so well. A 30lb belly can easily perform as a 60lb bow!
Mark in England