Ozbow

I have one .03 and one .04 Gordon's botuff fiberglass strips and want to make a 66" hill style longbow with straight limbs no reflex....please tell me what is the maximum Pound bow I can get and should the .04 glass go on the belly
Thanks.

If this is the kit you purchased from Bingham's it may be best to send an email to them and get their recommendations.

Daryl.

Daryl this is just some glass I picked up sometime ago the kit comes with .05 glass
I forgot to add that I will use a riser of 16" with .03 on the back and .04 on belly or the other way around depending on what is the right way according to what the experienced bowyers say..... And try to get the maximum! Poundage bow possible with safety and durability in consideration.
Thanks....

I would suggest the .030 glass for the back and the .040 glass for the belly.

I have not used this combination before but up to 50# may be ok, personally I would not go any heavier.

Daryl.

Thanks...I thought so too since glass is stronger in tension but wanted to confirm that before committing myself.
But what would be a safe maximum draw weight I can attain.....

Preston wrote:......... And try to get the maximum! Poundage bow possible with safety and durability in consideration.

greybeard wrote:.....I have not used this combination before but up to 50# may be ok, personally I would not go any heavier..

Preston wrote:.....But what would be a safe maximum draw weight I can attain.....

I don't know, perhaps someone else can give you an answer.

Daryl.

I too would use the .040 on belly. Hard to say what the max. poundage that could be achieved as it all depends on taper rates , number of lams etc, but with both glass strips being .040 and 4 lams with taper rate of .001. wood stack of around 380 would give you 50# . using the criteria of 1# per thou of glass, the thinner .030 glass would drop it by 10# meaning 40#. a 'rule of thumb' we allude to is the wood [ lams] stack being between 20% - 25% of total stack. Hard to give you a definitive answer as there are too many variables.

Thanks for your replies...I was reading on pirates of archery and one bowyer thinks the opposite is better with the .03 on the belly! I may end up making two longbows with same thickness and width profile to see which shoots better....

But my question was what maximum draweight I can get away with safetly without limb failure using .03 on back and .04 on belly and if the other way around what would be the max safe drawweight

Or another way of asking my question would be is if I followed the rule of 20 to 25% glass to wood ratio then the max thickness would be .35 to .28 wood lam thickness does this mean that I can make a bow with any reasonable draw weight upto 55@ 28" and it would be safe and I will not have any limb failure due to the glass failure
I hope Im not making you mad with my questions!!!!!!!

Preston wrote:.......But my question was what maximum draweight I can get away with safetly without limb failure using .03 on back and .04 on belly and if the other way around what would be the max safe drawweight.....

How long is a piece of string?

For safety / durability you may have more success building an American flat bow, i.e. the widest part of the limb is wider than the handle.

If you are using 1.5" glass the widest part of the limb can be a fraction narrower.

Daryl.

Daryl thanks for your reply.....
OK I'll go ahead and glue up a flatbow and keep the width at fades the max that should give me the max draw weight!!!
Why didn't I think of that???? And using the safe glass ratio I should end up with the max draw weight and safe bow limbs that I want.... is that correct?
With the fades being as wide as possible say 1-3/8" with .002 or a .003 taper or should I use a .004 taper? I will not be using tip wedges or powerlams etc...maybe I should leave the limbs parallel for about 2 to 3 inches after the fades too to keep the limbs from bending to close to the fades....then tapered to about 1/2" width at the tips and see what draweight I get. The bow will be 66" long ntn with a 16 to 17" riser....do you think this design will work OK?

I use a max. of .004 tapers in total, and begin my narrowing of limbs at the fades, going from 1/1/2'' at faded down to approx 1/2'' at tips for my howard hill style longbows and they have a great curve at full draw without tip wedges etc. in my humble opinion, you wont have to worry to much about limbs bending too much.

Thanks Bob so I'll use .004 taper 16" riser and taper from fade to tips. Do you make the lower limb shorter as measured from riser center? On my boo backed bows I started cutting the limbs using my locator point on the riser as center with the slelf cut just above and cut to 1/8" from center so that the arrow is almost touching my index finger and the bow is close to center shot. when I grip the bow that balances the bow nicely for me....should I follow the same setup on my glass bow will that be OK? Where do you cut your shelf?

One more thing where do you suggest I put my thicker glass strip on the belly or back?
Thanks for your patience and help.

Morning.

A suggestion.

John Clark who owns Ausbow in SA has a booklet for sale on making fibreglass reinforced composite bows. Buy a copy and have a read. It is very basic and an excellent starting point.

There may be alternative publications elsewhere or there may be suitable/appropriate material available on the Web.

http://www.ausbow.com.au/

Daryl, in response to your question, "how long is a piece of string?", the answer is 'twice its half length'.

Ranger

Lol...thanks ranger for answering that for me I was stuck for words!!!!

although some eminent bowyers such as Paul Comstock have promoted the advantages of asymmetrical limbs i still favour rightly or otherwise, equal length limbs and tillering to suit.My shelf is cut in according to the balance between static and dynamic centres, but that mostly equates to about 1 3/4'' above centre.Two schools of thought regarding where to place the .040 glass.Some say on the belly as compressive forces can be greater, others say on the back but then the forces there can overpower the thinner glass on belly. Toss a coin.

Bob thanks for your reply....yeah I've been reading the pros and con of where the thicker glass should go...I think since I want a safe and as powerful a bow as I can get I'll go with the .04 on the belly as common sense will dicatate. my shelf location I'll think about that and decide after glue up with the riser in the center so that I can always shorten the lower limb if I want to.....