Resin castings weeping sticky mess!

[bob the builder]

Good day, all!


I've run into something that I haven't seen before and wanted help from the experts.

I am finishing up a Russian Alfa buildup for a customer using a customer-supplied hull of unknown origin. Main hull castings are crisp and clean and are laid up in nice, thin epoxy. The issue that I'm running into is that the rear horizontal stabilizers seem to be weeping out a sticky substance through the paint. Prior to priming and painting, the fins were washed and scrubbed with solvent, sanded with high grit paper, then primed and painted.

I'm assuming this is the result of improperly mixed resin during the casting process that is post-curing somehow, but I'm not sure. Regardless, I'd appreciate advice on how to stop the madness from occurring more.

Thanks, in advance!


Bob

[Ralph --- SSBN 598]

I am no expert with epoxy or fiberglass.

However if the parts are weeping, it may not stop.
I would clean the parts the best I could and then make molds of the parts to reproduce new parts.
Or hand make new parts.

I'll be watching this thread to see how the experts would take on this issue.

[tsenecal]

Bob,

what you have there is an area of the casting that was has not cured, and will not cure. not necessarily due to improper mixing, but may be a reaction to impurities added to the resin by accident, or some other "foreign" substance. there may be no answer on solving this, but in the past i have had some success by encapsulating the (cleaned) resin piece in a thin coat of superglue, basically sealing it.

others have had to go so far as to drill out all the uncured area and fill it with putty or bondo

Tim

[thor]

Bob,

If this is a customer build, might I suggest producing new parts for the boat. I have seen this before, as well. There is a chance that it will work its way to the surface and blister up underneath the paint.

[bob the builder]

Parts were adhered to the boat when I got it. All the linkages are run and the control surfaces are pinned to the hull by them. Replacing/repairing will require a massive amount of work. I guess I'll reach out and see what he wants to do.

I like the idea of maybe using a thin layer of CA to encapsulate the area in question. Good news is that this will be a weathered boat and the rear planes are under the waterline, so nice and scummy..

[JWLaRue]

I've run into this problem in the past as well. In my case the areas affected were not too large, so I removed the bad areas and filled them back in with new material. Perhaps that would work in your case?

-Jeff

[bob the builder]

I've scrubbed the parts with solvent, sanded them out, added a coat of epoxy, skimmed them with filler, sanded, primed and re-painted. That's about as good as I think it will get.

On a related note, I was actually approached via a roundabout manner from someone who thinks they may be the original kit manufacturer. I've emailed him a few pics and we'll see if it is, indeed, his boat!


Bob

[JWLaRue]

Bob,

If I understand your reply, I'm not sure you are doing what I was suggesting? Think of it as similar to how a dentist takes care of a cavity. You need to clean out all the bad stuff and a little bit (more) of the good stuff....then put in a filling. I don't think just sanding is enough?

-Jeff

[bob the builder]

Jeff, I was posting fast and didn't make clear detail of what I did. Yes, I gouged out the "rotten" parts and filled them with glazing putty. Provided the sticky stuff doesn't ooze from other parts through the new material I added, I think I'll be good, but what a pain.

The creator of the kit did, indeed, email me and this was his message:

Bob, was just dumb luck I happened to read the sub committee forums as I seldom ever do anymore. Saw the weeping problem you had with Alfa and I knew it had to be mine. Had the same problem when I was casting the stern planes in black alumilite casting resin. I thought I had finally gotten a good set for that Alfa. As you saw in the pics I sent of that Alfa no weeping. Guess it just took awhile for it to seep through. I don't have that problem at all with the tan. Only thing I can think of is the guy that I bought the resin from on ebay either had that resin sit on the shelves for too long or bad resin from Alumilite. If you can't fix the problem let me know and I will send you a brand new set of stern planes cast in resin.

[JWLaRue]

Hi Bob,

Ahhh.....I was wondering why you hadn't tried removing all the bad areas! From the sound of it, this parts could just keep on being a problem due to the bad resin. As much extra work as it may mean, I think I'd take him up on the offer to get a new set of stern planes.

-Jeff