IMPORTANT! Check your fiberglass

[Mike Mecredy]

Hey, everyone.  I just got a large order of 2" wide glass from Bingham's and what's supposed to be.040 is closer to .035.   I know it doens't sounf like much but when your counting on .080 of glass thickness in your stack, and you end up .010 too thin, it's the difference of around 5# or so.  In the past I just assummed it was .040 and pressed on and made my laminations accordingly but now with several bows that came out too light, I'm checking every time.  I let Bingham's know about it already, but I'm not ceratain if they'll do abything about it or not.

Just be sure and check, I think Gordon's composits need to check their calibrations.

-Mike

[kennym]

Mike, I've found some of that also.

I check every pc. as it is packaged. .002 is my self-imposed limit, so .040 glass can be .038 to .042

You are right, check all components. They may average out or they may  give you a bow 5-10 off!

Good of you to post this, I hadn't really thought of it because I check em.

[rkmnt2]

Great post Mike....like Kenny, it's just something I do never really thinking about it being an issue for others. I'm a machinist by trade so it's just in-grained that everything has to have a tolerance.

[Mike Mecredy]

I have a big problem; I believing I get what I pay for, and that the people I pay every month for supplies try as hard as I do.  Apparently not. I always had the trust and felt I didn't have to check.
So I just added .080 to my lamination stack and called it good.  So is it my fault for not checking or their fault for not sending me .040 glass?

[PV]

Caveat emptor
Never so true as in todays economy.I believe in getting what I pay for as well but I check just the same.

 Guys like Kenny are,unfortunately,the exception rather than the rule.

Hows the knee Kenny?

[Bob Sarrels]

I usually order a little thick and sand to desired thickness.  Don't know if I have ever received a piece of glass that was spot on.  You gotta look.

[Walt Francis]

Mike, I hear ya!  However, with only one major manufacture of bow glass, they set the industries tolerance levels and we have to live with it.  

When I started building glass bows I was taught/told by my bowyer friend that the variance was the industry/manufacture standard and to always check the glass thickness.  I checked the first dozen glass strips I bought, which had come from Bingham’s, and found a variance in different sticks of .006.  The glass I have bought from Kenny has been within .002 of each other.  Not all glass is uniform throughout it entire length either, I find most pieces vary at least +/- .001-.002 in places.  I am still developing/designing my glass bows, so I check everything to eliminate as many variables as possible.

After saying all that, the variance in lamination density (not thickness) probably effects ones bow formula as much as any variance in the glass.

[Mike Mecredy]

I just noticed it this year,  Since 2006 when I stated my business I've never had a problem.  I suppose gordon's composits hired a new guy or something.

[wildwood]

Has my bow become a problem child? Im typing this with one finger cause hand in cast Brian P.

[legends1]

Mike,i also just went through the same thing last month with 1 3/4" glass.I talk to them too. I should have said something but thought it was just a one time thing because i had never had a problem.

[Mike Mecredy]

Yes brian, yours, I'll get it though. I had 2 versions of yours come out 4# light so far.  On the bright side one is spoken for.

Last year, for the entire year, I only had 3 come out under weight, those were all my fault for not using a calculator.

[**DONOTDELETE**]

Originally posted by Walt Francis:
Mike, I hear ya!  However, with only one major manufacture of bow glass, they set the industries tolerance levels and we have to live with it.  

When I started building glass bows I was taught/told by my bowyer friend that the variance was the industry/manufacture standard and to always check the glass thickness.  I checked the first dozen glass strips I bought, which had come from Bingham’s, and found a variance in different sticks of .006.  The glass I have bought from Kenny has been within .002 of each other.    Not all glass is uniform throughout it entire length either, I find most pieces vary at least +/- .001-.002 in places.  Not all glass is uniform throughout it entire length either, I find most pieces vary at least +/- .001-.002 in places.  I am still developing/designing my glass bows, so I check everything to eliminate as many variables as possible.

After saying all that, the variance in lamination density (not thickness) probably effects ones bow formula as much as any variance in the glass.

This is something that has always been a problem for bowyers that don't take the time to check, and use their glass "As-Is". I've found it varies from one shipment to the next not only in thickness, but in deflection properties as well. Trying to save time using your glass without sanding prior to lay up is too inconsistent for my likes. I run every piece through the drum sander with precision sleds. if i want .040 glass i order .043 and even then sometimes end up with a net of .038.

the best way i know to get good consistency is buy your glass in larger quantities and grind it to desired thickness. and every time you get a new shipment it's still a crap shoot on your deflection rates on that particular run of glass.

I've had identical stack heights using identical cores, vary as much as 8 pounds due to different shipments of glass... Ya gotta roll with the flow brutha... that's all we can do.

[wildwood]

Glad I could help .....I think...LOL

[Mike Mecredy]

All I'm saying is it's not something I should have to do.  But I do have to do it, because of other's short comings.  I don't have to run lab testing on my smooth-on to make sure the bond is as strong as they claim.

[recurvericky]

I agree with you Mike. With the technology and quality assurance standards of today, you should be able to get what you ordered. I wonder what the manufacturer would have to say on this subject?

[Sixby]

Heres what we have to do.

Check our entire stack . I mic each side too . If you have three or four lams and each one is a couple thousands heavy and they happen to stack up on one side you can get a limb with up to .010 heavy on one side. If its a recurve that is 10 lbs of twist. I can't even tell you how many times I have had to flip lams around to get a harmonious even stack side to side. Good enough is just not good enough unless poor is the goal.

I make it a habit to mic my glsss right off the bat and make sure I have the same amount of glass in each limb. Tonight I miced glass that was .038 yesterday I miced glass that was .042. Mix that up and you could have .008 difference , side to side in just glass in the limb. That is a bunch of twist going to happen. Now put a .038 on one stack and a .042 on the same stack and you have .040 of glass in each limb. It is wise to put the same glass strength on either the top or the bottom too. I prefer the lighter glass on the back. I can then lightly sand the belly if I have to for any tillering reason beyond side dressing. Othere nay prefer the heavy glass on the back. I am sure we all have our reasons.

Guys I cringe when I see nocks filed off to one side because a limb is so much stronger on a side that the center line is not the true center.  the real problem is that the guy having to do that is fighting it and very likely doesn'tknow what the problem is.

If we get the stack level then the center is center and you do not have to hardly ever cut a nock deeper or sand a side off to make a limb work. Once in a while perhaps but I have looked at racks of bows and every nock cut differently. Some bowyers even make it a practice instead of laying the limbs up right to start.

I would strongly suggest that heavy use of a micrometer is in order and much less use of files and sandpaper.
God Bless, Steve

As to manufacturer. I belive that they hold the best tolerances that they can. a couple of thousands is really tight. In the aircraft business as a machinist .003 was the acceptable tolerance on just about every part I ever saw milled. Its the build up we have to really worry about and especially with glass.

God bless you all, steve

[GREG IN MALAD]

Personally, I measure everything. If you compare the amount of time it takes to measure glass compared to the time it takes to make a replacement bow, i'll measure glass. Plus, what happens if somebody ships .050 glass in a box marked .040?

[Mike Mecredy]

Since I started making bows in 2001, this is the first time I've seen it off this much.  I made it nearly 10 years without having to do something I guess it made me a bit complacent.  But still, If I order .040 I still believe, no matter how much people tell me I should have checked it, I should be confident that the the company I just sent $306 dollars to, will put what I ordered in the box. It's not that hard to wrap up 20 peices of fiberglass and put it in a box and ship it.  THEY SHOULD MAKE SURE IT's RIGHT, NOT THE CUSTOMER.  Every lamination (before I started making my own) I've ever ordered from Kenny has been perfect.  Why can't Bingham's make sure Gordon's sent the them the right glass?  Why can't Gordon's send out the right product?  Why Can't the Democrats show up and vote? I can go on and on...

My Customers don't have to check their draw weight to make sure the bow I built is actually what I marked on the riser.  And if I am a pound or two off I tell them and if it's cool I send it, if they insist on 43# instead of 41.5# I fix it.  

If I go to the hospital and pay them for a bypass opperation should I get a vasectomy?  Just saying,  

This post was just to let everyone know that it never pays to rely on anybody but ourselves, (Oh...you can rely on God, but it seems when I mention anything about that it gets pulled) don't count on getting the right product anymore, check everything.  Before you take your tylenol send a sample to the lab to make sure it's not actully rat poison.    

[GREG IN MALAD]

Mike,
Call Gordons and ask what their tolerance range is, if your glass is out of spec then send it back to them. If Elmont only shipped 20 pieces of glass per year then your request that he measure everything for you would be reasonable. However he ships TONS of glass and I think it's unreasonable to demand that he do something that you refuse to do for yourself. I still cant understand why you wouldn't include the glass when you measure the stack height. You made a mistake, learn from it and move on.

[Mike Mecredy]

Greg I started this thread to let people know what's going on.  Plus, when did I mention I don't include the glass when measuring my stack thickness?

 Just so you all know, (and I shouldn't even have to mention this,) I make my laminations so the finished bow will be around .005 -.010 thicker than I need, so +/- .002 should'nt be an issue, but when it comes out .007 too thin inspite of me making the laminations thicker, that goes a little beyond my mistake. 002+/- is fine, but some of the ".040" I ordered last month is .033", -.007 too thin, that's not fine.  Anyone who thinks that's okay is way too accepting of inadequecy.  

This thread was meant to be helpful to those that don't have a shop full of machinery like I do.  The one that uses his hard earned weekends trying to make his kid a bow for his ucoming birthday, trying to get that 40# minimum, so his kid can hunt with him this fall, only to find out the stack he ordered is .014 too thin, because the glass isn't what he ordered.

(By the way the several bows that came out too light, (2 to be exact), both are already sold, but that still didn't get the finished product to the customer that ordered it yet.

I used to have to post them on the sposor's classifieds.)