Cracks in glass

[buckeyebowhunter]

I have been noticing these on a few sets of limbs ive glued up recently. At first i thought they were in the glass when i bought it but i got to thinking that maybe my air hose being old and having some dry smooth on, on it im getting some pressure points and actually causing the crack myself when i air up the hose.

I'm not going to throw away these limbs, there's probably a 100 dollars or more in materials on them. But do you think these will get worse over time? This one shows up really well, and it's just past the fade out on my wedge.

Anyone ever had this issue?

[Buggs]

I think I would save the limbs and throw away the hose!  If it came off the form looking like that, it's a manufacturing defect and not a mechanical failure. I bet you could stop that from getting worse. The stuff is made from epoxy so you should be able to wick some low viscosity epoxy in the crack (and the hole!) after warming it up, and then block it out.

P.S. by manufacturing, I mean the bowyer!

[Longcruise]

Looks like an impact.

[garyschuler]

I would check your bottom form for being square along its length. Do you have your form lined with a piece of glass?. Looks like either a cupped form surface and to much pressure. Check form for something by running a square along its length and watching for something stopping the square or snagging it. Very unusual for just the one spot with a crack. Like something embedded in the hose and or form. If it’s on the belly side. Check the hose, on the back of now check the form. Good lucky.

[kennym]

"I have been noticing these on a few sets of limbs ive glued up recently. "

If it's on a few sets, I'm guessing it isn't the glass.

Either something on the form or like you say something on the hose.  You should be able to feel something on the form if that side.  Are you using a pressure strip (if it's on the hose side)?

Always in same place, I don't think it will be the glass .

Stay with it , you'll find it.

[buckeyebowhunter]

Kenny, not always showing up in the same place. I should've mentioned these are on the back of the bow not the belly. I always use a metal pressure strip. Nothing on the pressure strip, my hose is getting in bad shape, I've been hard on it. There's quite a few spots of glue on it, I've ordered a new section of hose and a new pressure strip.

I'm more worried about shooting those limbs than anything or giving it to someone to shoot. I bet the cracks will be hardly noticeable once finish is on the bow. Just not sure if they are detrimental to the integrity of the limbs.

[kennym]

Will be interested if the new hose and strip cure it.   Reckon the hose glue boogers could push hard enough thru the strip to do that? 

Did you drill the crack in the pic or is that how it came out? 

Hope you get it figured out!

[buckeyebowhunter]

That is exactly how it was when i peeled the tape.

I didn't think the hose boogers would be that much of an issue, but i honestly don't know what else it could be unless there is a piece stuck on the pressure strip that im missing 

[kennym]

Hope ya figure it out, stuff like that can drive ya crazy!

[buckeyebowhunter]

No doubt man, especially considering the price of glass.

I just can't make any sense of it. I don't see any glue boogers on the hose or the pressure strip in the areas where the problem spots are. And ive used this form for many limbs without issues before. 

[Kirkll]

In that photo it looks pretty obvious there was something on your limb, the masking tape, or the plastic. you wrapped the limb in....looks like a grain of sand might be the culprit.....That pin point in the center of the crack gives it away.

I don't know what type of prep work you do prior to loading the bow or limbs in the form. But i think you should look at it closely. I have air hoses i've used for 15 years that were covered in smooth on at one point or another. I just air up the hose and sand it off with a palm sander and they are still going....But.... This is does not look like an air hose issue to me.

I used stainless steel pressure strips that also serve as heat strips. I sand these smooth and check the surface carefully before each lay up for glue.  I don't use masking tape on the limbs either... After lay up, i carefully wipe the limbs clean with lacquer thinner, and then use a thin painters plastic on a dust free bench to wrap the limbs. Everything is wiped down prior to loading into the form......   

If this has happened several times, i think you are missing something prepping the the pressure strips or getting something on your plastic or tape on the limbs..... I would also check the forms real well, but if its in different spots its probably not the forms.     .02 cents worth.    Kirk

[buckeyebowhunter]

Kirk, thanks for the post. My prep work isn't quite as intricate as yours but out of probably 60 limbs in this form ive only had this happen to 3 and only just recently. If it happened more i didn't catch them.

Hopefully the hose and new metal strip will help.  It's the same hose ive used since the beginning.

I guess a spec of dust or chip from the shop couldve ended up stuck to the glass just before glue up.

It's very strange. It's also very apparent because of the dark camo veneer under the glass. If i were betting I'd say there are many bows with glass cracks like that that weren't caught by the bowyer or customer due to them blending in with light veneers.

[garyschuler]

Most firehouse has 2 layers of canvas covering. I have in the past cut off one layer to get back to clean canvas covering. I don’t recommend more than 45 psi and use only until I find new hose. As a side note I get most of my hose from Fire Stations as they replace out dated hose. It’s still good hose but some sections might have cracking on the rubber lining. But I get 100 ft at a time for free and cut good sections out for bow building.

[buckeyebowhunter]

I've always aired up between 60 and 70psi, perhaps as more glue has built up on my fire hose over time it's created more psi in certain areas causing pressure points. This is the only logical conclusion i can come to after looking over my equipment multiple times. Not all the cracks are identical to the one in the picture.

[Kirkll]

I've always aired up between 60 and 70psi, perhaps as more glue has built up on my fire hose over time it's created more psi in certain areas causing pressure points. This is the only logical conclusion i can come to after looking over my equipment multiple times. Not all the cracks are identical to the one in the picture.

Brutha..... you need not use that much air pressure at all. 50-60 psi should be max. I've laid up limbs with 25# psi before and they came out fine. It wasn't on purpose though. i typically put in 20-25# then wait a minute or so to bring it up to 50-60#. But the phone rang and i got side tracked.... That being done, i laid up the second limb with low pressure too....... Those limbs have been shooting 10 years now....

It pays off to clean your glass and use new plastic every time.... My bet is a grain of sand on the glass itself or on the pressure strip up against the glass. Your hose didn't do that.      Kirk

[buckeyebowhunter]

Kirk, thanks for the tip. Years ago when I started i remember watching or reading in the Bingham's kit that 60psi was the norm. I guess i get a little heavy handed with the compressor Haha. I will back off on pressure some.

I always clean the sanded side and then painter's tape on the slick side. It is very possible that some sand or dirt got trapped. I just found it strange that it's happened twice in a row and none before.

I will update when i get my next set of limbs laid up.  Lams and glass are in the mail 

Thanks to everyone that posted to try and help me resolve this issue.

[Mad Max]

I always use just enough air psi plus 5/10 to close up the gaps on the belly ramps of the riser on a dry run.

[Kirkll]

Kirk, thanks for the tip. Years ago when I started i remember watching or reading in the Bingham's kit that 60psi was the norm. I guess i get a little heavy handed with the compressor Haha. I will back off on pressure some.

I always clean the sanded side and then painter's tape on the slick side. It is very possible that some sand or dirt got trapped. I just found it strange that it's happened twice in a row and none before.

I will update when i get my next set of limbs laid up.  Lams and glass are in the mail 

Thanks to everyone that posted to try and help me resolve this issue.

You might try just wrapping the limbs in clean plastic without the masking tape. There really isn't any reason to cook that stuff on your limbs. Just wipe the glass clean with lacquer thinner before wrapping

After you have your limbs edges dressed up and parallel, THEN use a bit of masking tape for you limb butt drilling, and maybe a bit on the tips to lay out the tip notch location. If you make limb profile patterns, you can just use spray paint to get the shape.... It's very consistent, and easier to edge sand  without the tape curling up.    another .02 cents.

https://photos.app.goo.gl/MB6pDhdCktdrPcsZA

[EvilDogBeast]

If you make limb profile patterns, you can just use spray paint to get the shape.... It's very consistent, and easier to edge sand  without the tape curling up.    another .02 cents.

That's handy!  You should put this in Tips and Tricks.

[buckeyebowhunter]

Kirk nice post