Worst Glue Line EVER

[willie]

have you checked with any local suppliers that sell glue for boat building or marine use ...epoxies or urea types?
some sort of way to spread the load under the clamps is helpful, and if you use string, try to find nylon string in a diameter that gives a little stretch.

have you seen yumi construction methods that use string (maybe non stretch is better here) and narrow wedges?

I see that you have just bought some new clamps though, maybe if you do one limb at a time?


many good tips on this thread.

[arachnid]

A while ago I started researching about building FG lam bows (yah yah, I knows... But I want to try it...). I contacted the company that distributes Smooth on here in Israel, but they stopped working with it. Instead they offered me a 2 part epoxy called 'Biresin CR80' manufactured by a german company called Sika. I asked on Tradgang but no one knew it. Does anyone heard of it? Can it be used for bow building? I've tried to read the technical sheet but I'm no technician, I didn't understand. I'll be glad to use it if it's suitable, I can get it pretty easily.

[PatM]

You can get West epoxy in a marine store in Tel Aviv.

[DC]

I have used a product(not for bows) called Sikaflex. Incredible stuff. If their epoxy is anywhere near the quality of this stuff I would use it in a minute. I am also of the opinion that any epoxy made by a reputable manufacturer will work for bows. I use West Systems 105/205 which is made for laminating fiberglass and it works great.

[arachnid]

I just checked that marin store`s wed site. They seem to have West System 105&205 epoxy. I need to give them a call to check out th price and delivary. If it`s good for making bows (wood bows and FG laminated bows) and I can get it in a good price, it might make this glue up failure worth it.
I always thought only smooth on is good for bows because it stays flexible after curing.

[DC]

West 105/205 is a 5:1 mix. West offers a set of pumps that dispenses the right amount but the minimum(1 pump of each) is about an ounce. This is about right for laminating a bow but for gluing a handle on or patches you want less. I went down to the veterinarian's office and got two small hypodermic syringes, just the ones for dispensing oral medicines. I routinely mix 1/2 cc of hardener and 2 1/2 cc of resin for these small jobs and have never had a problem with it not curing. I leave the syringes in a block so they are ready to use.   

[PatM]

I just checked that marin store`s wed site. They seem to have West System 105&205 epoxy. I need to give them a call to check out th price and delivary. If it`s good for making bows (wood bows and FG laminated bows) and I can get it in a good price, it might make this glue up failure worth it.
I always thought only smooth on is good for bows because it stays flexible after curing.

  Not at all. Glue can be relatively brittle and still handle being an internal glue line.  Too flexible and you get creep.

 Remember that pretty much anything is flexible when it is as thin as a good glue line.

 Check and see if the have G flex or 610. They are thicker and won't be as prone to running out of the joint. You can buy thickening agents for the 105 stuff.

[arachnid]

I just checked that marin store`s wed site. They seem to have West System 105&205 epoxy. I need to give them a call to check out th price and delivary. If it`s good for making bows (wood bows and FG laminated bows) and I can get it in a good price, it might make this glue up failure worth it.
I always thought only smooth on is good for bows because it stays flexible after curing.

  Not at all. Glue can be relatively brittle and still handle being an internal glue line.  Too flexible and you get creep.

 Remember that pretty much anything is flexible when it is as thin as a good glue line.

 Check and see if the have G flex or 610. They are thicker and won't be as prone to running out of the joint. You can buy thickening agents for the 105 stuff.

Wait a minute, I`m comfused... Is West System epoxy good for bows or not? Is it too thin?

[PatM]

It's fine but generally pure bonding epoxy is thicker. Thinner stuff can make it easier to starve the joint. G Flex is thicker and 610 is even thicker still.
  The 105 just requires a bit of care or additives which West  provides in various forms.

[DC]

I use an additive called Cab-O-Sil. The people that sell West stuff will have it. No matter what you use you should cover the back of the bow with masking tape. I also wrap it with plastic wrap before I put the inner tube wrap on. Epoxy will glue the tube to your bow. It comes off but then you can't re-use the tube strips. Oh, I cut my tube strips 1/2" wide and make 2 or 3 passes. I've done 3 boo backed yew bows and numerous patches. I've been about 95% happy with the joints. The 5% was my screw-ups

[mikekeswick]

All you needed to do with your original glue-up was use a pressure strip to even out the pressure.
Just about any of these glues will work. People have their own favourites.
The best advice I can offer is no matter what glue you use get the data sheet with it when you buy. Follow the preparation steps to the letter.
Thin lams really need a form.
With the gle-up you have done. Use heat to release both sides. Clean them both back up with a drum sander. Make a 1/16th thick lam to take up the reduction in thickness you'll have after cleaning them up. Make a basic form. figure out your glue and how best to use it. Then use a pressure strip regardless of if you use clamps or inner tubes for clamping.

[DC]

I read somewhere that water based(like PVA) glues can cause thin pieces(like backing) to cup. If the edges curled up on yours maybe that was the issue. Clamps won't help in this case because they don't all reach the edge. Rubber tubes hold the edges down, sometimes at the expense of the middle, so we use the pressure strip down the middle. If you put the backing on the other way, so the edges curl down, you still need the pressure strip. Epoxy doesn't cause cupping

[PatM]

The water in the PVA gets absorbed and allows the wood to swell unevenly.