To clean or not to clean off uncured fiberglass

[Ed_K]

While repairing my transmission tunnel cover, I mixed up a batch of fiberglass resin and applied it to the cover and it never cured. The resin was left over from the repairs to my gas tank which worked fine two years ago but apparently something important has evaporated out of the resin or the hardener since then. I am left with a thin layer of uncured resin that is painted onto the tunnel in various locations.
It has been over 24 hours so I know it will never cure as is.
I have peeled off the fiberglass cloth patches and threw them away already....
... Do I have to completely clean off the remaining uncured resin from the cover with acetone or MEK before applying a new coat of fiberglass ( from newly purchased ingredients ) ? or
will the heat from a good batch applied over the remaining uncured resin, cure the remaining uncured resin ?
I don't have very much experience with fiberglass, ( that is obvious by now ), and could use some advice from the voice of experience.
Thanks,
Ed

 

[John Loftus]

Re: To clean or not to clean off uncured fiberglas

If you are doing thin layers you want 'finishing resin'. It has a wax which seals the layer and helps it kick off solid so it isn't tacky. Some of the other laminating resins are slightly tacky to allow further coats.

I would wash off as much of the uncured resin with acetone as possible. In the future, sometimes you can use a heat lamp (or sunshine) to warm and 'kickoff' the resin. Next time make a sample batch to make sure the resin, hardener and proportions you are measuring are correct. BTW, Don't use more hardener than recommended. If it kicks off too fast it is not as strong and you won't have much time to work with it.

Another thought is to use Epoxy resin. It is stronger and always kicks off well for me. You just need to be more careful to keep it off your skin because certain formulations can be absorbed through the skin.

Cheers,
John

 

[Ed_K]

Re: To clean or not to clean off uncured fiberglas

John,
I did try an electric space heater placed next to the tunnel for over an hour with no noticeable increase of solidity.
Guess I'll clean it off with MEK tomorrow and try again with newly purchased materials. Only lost 1 + 1/2 days and a few dollars.
Thanks,
Ed

 

[tiga2]

...Maybe I am too late on this, but I have worked a lot with FRP and have made this mistake also. In fact this happened to the FRP I just put on the deck of the boat I am restoring. I just mixed up a "hot batch" and re-applied, seemed to work just fine. This would not be a good idea for structual FRP!

 

[pan]

Ed,
John's advice is sound. Washing with acetone will remove enough uncured resin to allow the new application to bond.
Polyester resin has a very limited shelf life so it is best to safely discard any unused material if you have finished your job.
Be careful with "hot batchs". As John says, there is little strength.
Alwyn

 

[vette]

Ed, I concur with John Loftus as well. I have seen production shops get uncured resin to kick off with alot of direct heat the next day. They're more concerned with getting it out the door than strength, etc. I would clean as much if not all of it off before restarting. My thoughts are that what is left on will not have the proper percentage composition and at that point you don't know what you have. Throw away the old stuff. I once used year old resin and hardner and came back after a week vacation and it still wasn't hard, and it set just inside a window with the western sun baking on it every day for a week.

 

[Ed_K]

Re: To clean or not to clean off uncured fiberglas

Last weekend I spent some quality time with some rubber gloves , MEK, and a wire wheel on one of my drills. I got all of the uncured resin off of it and then started over with new resin. My lesson learned is to ALWAYS throw out the leftover resin and hardener from any fiberglass project. The materials must have a shelf life of less than two years.
... Now if I can figure out a way to sand the reconstructed bottom edges of my tunnel cover perfectly flat. I am using a belt sander and perhaps if I take off a little at a time and then check it for flatness often I can do it.
Thank you all for the input/advice.
Ed

 

[GregW]

Re: To clean or not to clean off uncured fiberglas

Just tie it to your bumper with a rope and drag it down the street. It's like the worlds largest belt sander. Thanks for the info on the resin. I've got some that has probably expired from when I did my steering wheel and dash. Off to haz mat!

 

[John Loftus]

Re: To clean or not to clean off uncured fiberglas

... Now if I can figure out a way to sand the reconstructed bottom edges of my tunnel cover perfectly flat.

Hi Ed,

You can spray glue some sheets of coarse sandpaper to a large flat surface like a piece MDF or plywood. Glue the sandpaper down in two strips equaling the width of the tunnel. Then move the tunnel back and forth across the board/sandpaper to sand it flat.

Another option is to make a 3 foot long and 4 or 5" wide sanding stick from plywood or MDF. Glue the coarse sandpaper to that (you can even cut belt sander loops and glue them down). Turn the tunnel upside down and figure out some way to hold it securely. Then holding the sanding stick at a 45 degree angle, bridge across both sides and sand back and forth down the length of the tunnel. Check occasionally with a straight edge.

Cheers,
John

 

[Ed_K]

Re: To clean or not to clean off uncured fiberglas

... Now if I can figure out a way to sand the reconstructed bottom edges of my tunnel cover perfectly flat.

Hi Ed,

You can spray glue some sheets of coarse sandpaper to a large flat surface like a piece MDF or plywood. Glue the sandpaper down in two strips equaling the width of the tunnel. Then move the tunnel back and forth across the board/sandpaper to sand it flat.


Another option is to make a 3 foot long and 4 or 5" wide sanding stick from plywood or MDF. Glue the coarse sandpaper to that (you can even cut belt sander loops and glue them down). Turn the tunnel upside down and figure out some way to hold it securely. Then holding the sanding stick at a 45 degree angle, bridge across both sides and sand back and forth down the length of the tunnel. Check occasionally with a straight edge.

Cheers,
John

John,
Yes, thats a good idea and has me thinking if there is any reason why I can't glue some down to the flat concrete floor of my garage and skip using a piece of plywood. I can't think of any reason why I shouldn't try it.
Thanks for the idea !
Ed

 

[John Loftus]

Re: To clean or not to clean off uncured fiberglas

Ed,

I was going to mention just using the concrete floor .. it's just more of a one time thing (I keep my coarse and fine sanding sticks for other jobs).

You could probably just get away with doing one side at a time. Once both sides are flat and about the same thickness you will be good to go.

 

[Ed_K]

Re: To clean or not to clean off uncured fiberglas

Greg and John,
Thanks to both of your ideas, I took a look at my concrete garage floor and driveway. I discovered that my flat concrete driveway is about 80 grit rough so I sat down and pushed my tunnel cover back and forth to sand down the repaired fiberglass edges. It works like a a big flat 80 grit sanding block and flattened the edges up in perfect relationship to each other !
I then filled up the last remaining voids in the edge. One more driveway session should finish the job. This is the way to get this done unless you happen to have a three foot wide industrial belt sander or something.
/bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif

 

[GregW]

Re: To clean or not to clean off uncured fiberglas

I guess that's a good argument for me not to put tile down in my garage. Woo Hoo, scratch a chore off the list! Glad you got it sorted out. /bcforum/images/%%GRAEMLIN_URL%%/cheers.gif