G/Flex Epoxy
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chuckneese
- C Boater
- Posts: 48
- Joined: Tue Aug 16, 2005 4:08 am
- Location: Birmingham, AL
G/Flex Epoxy
Has anyone had experience with G/flex on an ABS whitewater canoe?
Re: G/Flex Epoxy
Yes. Pretty extensive. I have used it to fill and bond cracks and do more extensive repairs using both aramid and fiberglass cloth and I have used it to apply about 20 some Dynel skid plates. It works very well.
Others have used the more conventional (and cheaper) epoxies such as West Systems 105 resin/205 or 206 hardener and had good results on ABS boats but I have seen repairs (done by others) using 105/205-6 or comparable epoxies from MAS or System 3 delaminate over time so I have preferred using the G-Flex. It can also be mixed up in very small batches by eye, which is convenient when one is filling and fairing small cracks and areas of damage.
The G Flex is more viscous than West 105/205-206 so it takes a little longer to work it into cloth when wetting out, and I have not tried wetting out multiple layers of cloth simultaneously. At typical working temperatures it has a longer pot life and working life than 105/206 so you have time.
If you read the instructions for G Flex, West Systems states that pretreating ABS by passing the flame of a propane torch over the surface is "optional". While flame pretreating is absolutely essential for obtaining a good bond to polyethylene, I have found it unnecessary for Royalex. I did it once, have not done it since, and have not had any failures. I have found that the G Flex bonds well to Royalex whether the vinyl skin is present or not. Make sure you clean the Royalex well with denatured or isopropyl alcohol, and I would also lightly sand the surface with 80-120 grit sandpaper before cleaning with alcohol.
Others have used the more conventional (and cheaper) epoxies such as West Systems 105 resin/205 or 206 hardener and had good results on ABS boats but I have seen repairs (done by others) using 105/205-6 or comparable epoxies from MAS or System 3 delaminate over time so I have preferred using the G-Flex. It can also be mixed up in very small batches by eye, which is convenient when one is filling and fairing small cracks and areas of damage.
The G Flex is more viscous than West 105/205-206 so it takes a little longer to work it into cloth when wetting out, and I have not tried wetting out multiple layers of cloth simultaneously. At typical working temperatures it has a longer pot life and working life than 105/206 so you have time.
If you read the instructions for G Flex, West Systems states that pretreating ABS by passing the flame of a propane torch over the surface is "optional". While flame pretreating is absolutely essential for obtaining a good bond to polyethylene, I have found it unnecessary for Royalex. I did it once, have not done it since, and have not had any failures. I have found that the G Flex bonds well to Royalex whether the vinyl skin is present or not. Make sure you clean the Royalex well with denatured or isopropyl alcohol, and I would also lightly sand the surface with 80-120 grit sandpaper before cleaning with alcohol.
Re: G/Flex Epoxy
What he said.
Another thing. When I am serious about using epoxy to attach something to Royalex, I first remove the vinyl outer layer of the Royalex. The vinyl itself is not as strong as the ABS underneath, and the bond of the vinyl to the ABS is not as strong as the bond epoxy will make to the ABS.
Folks used to remove the vinyl layer by sanding, but I've found that it can be skimmed off quickly, using a half inch sharp chisel held at a low angle. The chisel blade will cut down through the soft vinyl, but when it hits the hard ABS, it will ride along the ABS surface, lifting the vinyl off right at the boundary. It also helps to push the chisel blade at a small angle, maybe 15 to 20 degrees. And, you can overlap subsequent swaths as if you were cutting the lawn. Be a bit more careful if you are skimming vinyl off a concave surface, like the inside of your boat.
Once nearly all the vinyl is off the area where the epoxy will form the bond, a little sanding will prepare the surface.
pblanc noted that G-flex may not soak into cloth as easily as West 105/205. Be aware that certain cloth weaves may make G-flex a poor choice. I have a small batch of a special satin weave S-glass that I got from sweetcomposites.com. All S-glass has very fine fibers, so S-glass doesn't wet out as easily as most E-glass. I found that my strange satin weave S-glass is hard to wet out even with West 105/205, and I would not try G-flex on a bet.
I think the stiffness/flexibility of West 105/205 is very close to that of ABS, while G-flex is a bit more flexible. For laying cloth on ABS, 105/205 may work as well or better. I have a 2-layer S-glass wear patch right under the pedestal of my Royalex ww boat, and its resistance to being dragged over sharp rocks has been outstanding over about four years. Of course the vinyl was removed, and I used 105/205 resin.
But if I were attaching something like a thigh strap mount to the inside of a Royalex boat, I would choose G-flex, because of the kind of stresses applied to such fittings.
Another thing. When I am serious about using epoxy to attach something to Royalex, I first remove the vinyl outer layer of the Royalex. The vinyl itself is not as strong as the ABS underneath, and the bond of the vinyl to the ABS is not as strong as the bond epoxy will make to the ABS.
Folks used to remove the vinyl layer by sanding, but I've found that it can be skimmed off quickly, using a half inch sharp chisel held at a low angle. The chisel blade will cut down through the soft vinyl, but when it hits the hard ABS, it will ride along the ABS surface, lifting the vinyl off right at the boundary. It also helps to push the chisel blade at a small angle, maybe 15 to 20 degrees. And, you can overlap subsequent swaths as if you were cutting the lawn. Be a bit more careful if you are skimming vinyl off a concave surface, like the inside of your boat.
Once nearly all the vinyl is off the area where the epoxy will form the bond, a little sanding will prepare the surface.
pblanc noted that G-flex may not soak into cloth as easily as West 105/205. Be aware that certain cloth weaves may make G-flex a poor choice. I have a small batch of a special satin weave S-glass that I got from sweetcomposites.com. All S-glass has very fine fibers, so S-glass doesn't wet out as easily as most E-glass. I found that my strange satin weave S-glass is hard to wet out even with West 105/205, and I would not try G-flex on a bet.
I think the stiffness/flexibility of West 105/205 is very close to that of ABS, while G-flex is a bit more flexible. For laying cloth on ABS, 105/205 may work as well or better. I have a 2-layer S-glass wear patch right under the pedestal of my Royalex ww boat, and its resistance to being dragged over sharp rocks has been outstanding over about four years. Of course the vinyl was removed, and I used 105/205 resin.
But if I were attaching something like a thigh strap mount to the inside of a Royalex boat, I would choose G-flex, because of the kind of stresses applied to such fittings.
Re: G/Flex Epoxy
I am a big fan of G-flex for ABS repair, but recently have had disappointing results with it adhering to vinyl. I contacted the folks at West Systems and they said the same thing. For best results they recommend removing the vinyl. On the ends of boats where there is less flexibility like for stem repairs on applying grunge pads 105/205 is as good as G-flex and lots cheaper.
Re: G/Flex Epoxy
I used Gflex for two boats with major repairs, one a replacement of a football sized, through the hull patch of cracked and deteriorated down-to-the-foam Viper bottom, one an army of cracks that developed in a spark from excessive glue application under a saddle.
Both done without cloth whatsoever. If you use cloth, think twice about the Gflex - cloth is not flexible, gflex is. You can actually use ABS sheets (buy at your local RC model shop for a dollar..) to re-surface anything. Thats what I did on the bottom of the Viper, and on the inside of the Spark.
Now the trick is in the filler - either low weight volume filler, cotton flour for bonding.. without creating a non-flexible mess that will pop right off. You could also use abrasion-resistant aluminum dust (actually aluminum oxide, mind you.. hard hard hard!) to cover outsides of repairs, or paddle tips.
If you want to save money, mix it 50/50 with regular 105/205 resin&hardener mix.. it should still work in most applications.
To find out about the mechanical properties of the diferent fills, I would suggest pouring little 1mm plates, cutting them out and torturing them along with a piece of ABS sheet to see how they stand up to it. Testing - takes time, but it's worth it!
Cheers,
Jan
ps. here's a couple images of my repairs, among others.
Viper:
http://www.ipernity.com/doc/mahyongg/8381331" onclick="window.open(this.href);return false;
Spark:
http://www.ipernity.com/doc/mahyongg/7750679" onclick="window.open(this.href);return false;
Both done without cloth whatsoever. If you use cloth, think twice about the Gflex - cloth is not flexible, gflex is. You can actually use ABS sheets (buy at your local RC model shop for a dollar..) to re-surface anything. Thats what I did on the bottom of the Viper, and on the inside of the Spark.
Now the trick is in the filler - either low weight volume filler, cotton flour for bonding.. without creating a non-flexible mess that will pop right off. You could also use abrasion-resistant aluminum dust (actually aluminum oxide, mind you.. hard hard hard!) to cover outsides of repairs, or paddle tips.
If you want to save money, mix it 50/50 with regular 105/205 resin&hardener mix.. it should still work in most applications.
To find out about the mechanical properties of the diferent fills, I would suggest pouring little 1mm plates, cutting them out and torturing them along with a piece of ABS sheet to see how they stand up to it. Testing - takes time, but it's worth it!
Cheers,
Jan
ps. here's a couple images of my repairs, among others.
Viper:
http://www.ipernity.com/doc/mahyongg/8381331" onclick="window.open(this.href);return false;
Spark:
http://www.ipernity.com/doc/mahyongg/7750679" onclick="window.open(this.href);return false;
Re: G/Flex Epoxy
mahyongg, I'm not sure what you mean about cloth not being flexible. The patches I have put on Royalex boats, using glass and epoxy, certainly are flexible. If I needed more flexibility, I would use nylon or polyester cloth, or Kevlar.
It is good to have a reasonable match between the resin's flexibility (once hardened) and the underling ABS. West 105/205 is certainly a good match.
I don't have anything against using ABS sheet for repairs, or painting on ABS that has been dissolved in acetone. But I wouldn't want anyone steered away from using cloth and epoxy for situations where ABS sheet might be hard to apply.
It is good to have a reasonable match between the resin's flexibility (once hardened) and the underling ABS. West 105/205 is certainly a good match.
I don't have anything against using ABS sheet for repairs, or painting on ABS that has been dissolved in acetone. But I wouldn't want anyone steered away from using cloth and epoxy for situations where ABS sheet might be hard to apply.