formula for bows

[twoknifes7]

#7141

I have a question for the public I have been plagued with my explosions and lack of reaching my goal on poundage is there a formula to bring that into a science?

[grumpy]

#58520

What do you mean by explosions??

You might read my thread on building the bow.

Remember:

Just becouse it didn’t work does not mean it is not a good idea. At least now you know what dosn’t work, and knowledge is precious.

The only BAD ideas are the ideas that involve the ER and/or the COPS.

[Arne Moe]

#58524

Single growth ring on the back of the bow or backed with something. As you tiller, never pull the bow farther than the desired end weight. If you pull to 50# for example and get that at 10″ keep scraping until your get 50# at 11″, etc. You have to “sneak up” on final draw length and weight by NEVER exceeding your target weight.

If I understand your question correctly.

Arne

[David Coulter]

#59813

Arne,

Why is that? Why should you not pull the bow back farther than the weight you are trying to end up with? Interesting. dwc

[Arne Moe]

#60248

The way I was taught was to never stress an all wood bow beyond it’s target draw weight. That reduces (reduces, not eliminates) the bow taking set or crysalling. Other more experienced bowyers may have other ideas but again, as I understand it pulling a bow to (say) 70# but at less than final draw length during tillering when you want a 50# bow in the end will crush the fibers or overstress the limbs.

I learned this from a Jim Hamm bow class I took a few years ago and it is mentioned in several books.

For me, theory aside, it allows me to hit my draw weight pretty close and at the desired draw length. This is also one of the reasons that for self bows, you don’t want someone with a t 30″ draw length to shoot your self bow that was made to shoot at 28″.

Arne

[David Coulter]

#60320

Arne,

thanks for the explanation. It all makes sense. I thought it must be something like that. There’s a lot to making a bow. Maybe someday I’ll give it a swing. Thanks, dwc

[twoknifes7]

#64082

I have made many selfbows and had a few break but now I am trying to make a laminate bow and so far I’ve had every one break I am using actionbamboo for the back and osage veneers fir the core and curly maple for the belly I’ve had 3 break and one to come under weight. I thought that maybe there was a formula for the thickness of each lam would be for a desired weight.

[Arne Moe]

#64089

I wouldn’t have said a word if I’d known you were talking laminated bows. Quite a different animal.

Arne

[handirifle]

#11372

twoknifes7 wrote: I have made many selfbows and had a few break but now I am trying to make a laminate bow and so far I’ve had every one break I am using actionbamboo for the back and osage veneers fir the core and curly maple for the belly I’ve had 3 break and one to come under weight. I thought that maybe there was a formula for the thickness of each lam would be for a desired weight.

I had some bows break when I was making them, and from my experience it was usually one of two causes.

The most common cause is inadequate glue coverage. Are you coating BOTH sides of EACH internal piece? Only the inside side of the outer pieces get covered.

What glue are you using? Smooth On and most others are measured by weight. The resin and hardener need to be the same weight, before mixing.

On the glue up, if the wood has any oils on it from your hands or any dirt, the glue can give way.

What temperature are you curing the bow at? Usually 160-180 deg will be the norm

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