Hi all. I'm new to the board and to boatbuilding. I'm building a Bob's Special and I have my strips cut, my strongback built, and my forms cut. This was fairly easy as I have worked with wood many times.
Being new to the glassing process, however, I tried my hand at a test glassing project on something I made for my kids. For the most part, the fiberglass looks great, but in two spots on the project, the epoxy remains somewhat tacky. The rest of the surface is hard, smooth and dry. What did I do wrong. The wood surface was clean and freshly sanded and the epoxy resin was well mixed. The remaining epoxy in the plastic bowl hardened nicely with no hint of tackiness. Why did these two spots not dry properly? :rolling eyes
Thanks for any hints you can offer.
Epoxy question
If the epoxy was mixed well in the correct ratio (as supported by the fact that most of it cured properly, including that in the mixing pot), and there was nothing on the wood, I'm placing my bet on there being something on the glass cloth. Perhaps oil or dirt from handling or at some point during it's storage or transport?
Cheers,
Bryan
Cheers,
Bryan
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Erik, Belgium
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- Location: Gierle, Belgium
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Bryan, sorry but I don't really agree with you. If the cloth was contaminated with oil/greese, the epoxy will still harden, but won't stick on the cloth in that area.
My bet is that
a) the mixture wasn't well enough stirred. I always mix epoxy & resin for at least 3 minutes, and always go well on the inner sides of the container to make sure there is no unmixed epoxy left on the sides. The resin will harden out by chemical process. This can only happen when the mixture is WELL stirred.
b) the container itself may have been contaminated.
You can read the do's and don't's here: http://www.epoxy.com/install.htm
Erik, Belgium.
My bet is that
a) the mixture wasn't well enough stirred. I always mix epoxy & resin for at least 3 minutes, and always go well on the inner sides of the container to make sure there is no unmixed epoxy left on the sides. The resin will harden out by chemical process. This can only happen when the mixture is WELL stirred.
b) the container itself may have been contaminated.
You can read the do's and don't's here: http://www.epoxy.com/install.htm
Erik, Belgium.
Thanks guys. As I said, every bit of the remaining resin in the mixing bowl hardened nicely with absolutely no hint of softness. I guess it is possible that the part that was not blended well ended up on the piece and therefore did not harden.
Any idea how I fix it?
This is exactly why I decided to do a test project. Thanks for your help.
Any idea how I fix it?
This is exactly why I decided to do a test project. Thanks for your help.
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Glen Smith
- Posts: 3719
- Joined: Sat May 08, 2004 9:08 am
- Location: Baie-St-Paul, Quebec, Canada
Hi Mac, what brand of epoxy did you use? Did you use calibrated pumps or some other dispensing and measuring method? What type of container did you use for the mixing? What did you use for the mixing? How long did you mix it? Was your workshop at a comfortable temperature or quite hot or cold? What type of material is the epoxy applied to? Does it include fiberglass cloth or just epoxy? If cloth used, what type and weight? Is the soft epoxy beneath cloth or above it? How was the surface prepared before applying the cloth and/or epoxy? How many coats of epoxy did you apply and at what time interval between coats?
There are so many things that can go wrong with epoxy that it can't usually just be blamed on bad ratio or poor mixing. Sources of contamination can be any of the objects or substances that have come in contact with the epoxy before, during and after application. If the wood substrate wasn't well cleaned before application you could have a problem with the wood's natural oils. If your shop was quite hot and you were sweating, 2 drops of sweat on the epoxy could cause 2 soft spots. A lot of variables to cover.
To remove the soft spots you should first scrape off as much as you can with a wood stick, putty knife or other instrument. Then use dry rags to wipe off as much of the remainder as possible. Then the spots should be washed with a rag dampened with warm water with a drop of white vinegar mixed in. Throughly dry the spots the sand, clean up and recoat. To test your skills at patching, you can fill the spots with epoxy then apply a piece of plastic sheeting over top and run the squeegee over the plastic to level the epoxy and force out the excess. Remove the plastic only after the epoxy has set for about 4 hours.
It is much better to be learning about these things now on a test panel rather than later on your boat.
There are so many things that can go wrong with epoxy that it can't usually just be blamed on bad ratio or poor mixing. Sources of contamination can be any of the objects or substances that have come in contact with the epoxy before, during and after application. If the wood substrate wasn't well cleaned before application you could have a problem with the wood's natural oils. If your shop was quite hot and you were sweating, 2 drops of sweat on the epoxy could cause 2 soft spots. A lot of variables to cover.
To remove the soft spots you should first scrape off as much as you can with a wood stick, putty knife or other instrument. Then use dry rags to wipe off as much of the remainder as possible. Then the spots should be washed with a rag dampened with warm water with a drop of white vinegar mixed in. Throughly dry the spots the sand, clean up and recoat. To test your skills at patching, you can fill the spots with epoxy then apply a piece of plastic sheeting over top and run the squeegee over the plastic to level the epoxy and force out the excess. Remove the plastic only after the epoxy has set for about 4 hours.
It is much better to be learning about these things now on a test panel rather than later on your boat.
Wow, great info Glen; thanks
I did not use calibrated pumps. My test piece is about 6 square feet in size. The bad spots total about 16 square inches. I did use 6oz cloth for my test, but the epoxy is the small can you get at home depot with the "bondo" brand. I know it's not what I'll use on the boat, but I just wanted to get a feel for the process.
I used a plastic cool whip container to mix and a brand new, disposable plastic spoon. Temperature was probably in the 65 degree range
The surface is cedar strips, freshly sanded and clean. I put a coating of the epoxy down first, then layed the glass over it and wetted out the glass with another application. The more I think about it, the more I think that something got on the wood prior to the expoxy application. I will try the repair method you suggested.
I am so happy that I decided to do a test run; I think this would be a good idea for any new builder prior to dumping a bunch of goo on your new work of art. :eyebrows
I did not use calibrated pumps. My test piece is about 6 square feet in size. The bad spots total about 16 square inches. I did use 6oz cloth for my test, but the epoxy is the small can you get at home depot with the "bondo" brand. I know it's not what I'll use on the boat, but I just wanted to get a feel for the process.
I used a plastic cool whip container to mix and a brand new, disposable plastic spoon. Temperature was probably in the 65 degree range
The surface is cedar strips, freshly sanded and clean. I put a coating of the epoxy down first, then layed the glass over it and wetted out the glass with another application. The more I think about it, the more I think that something got on the wood prior to the expoxy application. I will try the repair method you suggested.
I am so happy that I decided to do a test run; I think this would be a good idea for any new builder prior to dumping a bunch of goo on your new work of art. :eyebrows
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Glen Smith
- Posts: 3719
- Joined: Sat May 08, 2004 9:08 am
- Location: Baie-St-Paul, Quebec, Canada
I have always recommended making a test panel to try out any new products or techniques before commiting them to a boat.
"Bondo" is sold as either epoxy resin or polyester resin. I hope you got the epoxy resin and hardener. Bondo may be prone to "amine blush" which could be your problem. Try to just wash the surface first with water and vinegar and wipe dry with paper towels. If it remains sticky then you will have to remove it.
Brand new plastic spoons can have an oily substance on them that was used as a release agent for the molding process. I prefer to use wooden coffee stir sticks or tongue depressors. Any used container from the kitchen must be thoroughly washed, rinsed and dried before using with epoxy to prevent contamination.
If you laid the cloth over wet epoxy, please note that this is not the standard boat building process you should use when glassing your boat. You should lay out the cloth over bare, dry wood then wet out the cloth and wood in one step or you can apply a sealer coat to the wood and allow it to dry before applying the epoxy. The actual precoat process can be more complicated than this, it depends on the brand of epoxy used and the elapsed time between precoating and cloth wetout.
Let us know how the experiment goes.
"Bondo" is sold as either epoxy resin or polyester resin. I hope you got the epoxy resin and hardener. Bondo may be prone to "amine blush" which could be your problem. Try to just wash the surface first with water and vinegar and wipe dry with paper towels. If it remains sticky then you will have to remove it.
Brand new plastic spoons can have an oily substance on them that was used as a release agent for the molding process. I prefer to use wooden coffee stir sticks or tongue depressors. Any used container from the kitchen must be thoroughly washed, rinsed and dried before using with epoxy to prevent contamination.
If you laid the cloth over wet epoxy, please note that this is not the standard boat building process you should use when glassing your boat. You should lay out the cloth over bare, dry wood then wet out the cloth and wood in one step or you can apply a sealer coat to the wood and allow it to dry before applying the epoxy. The actual precoat process can be more complicated than this, it depends on the brand of epoxy used and the elapsed time between precoating and cloth wetout.
Let us know how the experiment goes.
Epoxy
Mac, Glen is the expert here.
I use 6 oz plastic drinking cups and toss them after each mix. I've used all kinds of stirring sticks, each has their good and bad traits.
I like the #804 mixing sticks made by West System. They are reusable and can be wiped clean. The sides and end of the sticks are thin and sharp and will wipe off the epoxy from the sides of the mixing cup. It seems like these stir sticks don't introduce as much air bubbles as wooden sticks I've used. As it's been said, mix and mix again.
Sooner or later you will have to invest in a good epoxy system as well as calibrated pumps, for glassing your canoe. I would suggest you then run your tests as Glen suggests with the real epoxy.
Ed..
I use 6 oz plastic drinking cups and toss them after each mix. I've used all kinds of stirring sticks, each has their good and bad traits.
I like the #804 mixing sticks made by West System. They are reusable and can be wiped clean. The sides and end of the sticks are thin and sharp and will wipe off the epoxy from the sides of the mixing cup. It seems like these stir sticks don't introduce as much air bubbles as wooden sticks I've used. As it's been said, mix and mix again.
Sooner or later you will have to invest in a good epoxy system as well as calibrated pumps, for glassing your canoe. I would suggest you then run your tests as Glen suggests with the real epoxy.
Ed..
Ed Alger