TOPIC: Poly resin question

For all you glass experts out there. I have a new keel strip and transom installed in my Redfish Capri. It is now covered and in my carport for the winter. I noticed recently that a small amount of water got in and froze over the new glass near the transom area (still only matt there).

My question is this: Where the water was, the resin has taken a cloudy white appearance. I am sure that no water actually got through to the wood below, but am just curious why the cured poly resin has taken a chalky appearance where the water was. Any thoughts?

Andrew

I cant give you a true scientific reason. But if you didnt use wax in your resin, the resin doesnt fully cure out. it is air inhibited to a full cure. meaning that with out it being sealed off from air the top surface is still tacky. So the water that pools up on the surface causes a milky color. It doesnt cause a problem but before you paint or add another layer of glass you need to sand for anything to stick to it. Most resins even with out wax added should be sanded after 72 hours for anything to stick.

Ditto on the above. Contraty to what you might think, Polyester resin is actually water soluable - but extremely slowly. The more recent that the resin was applied, the easier it is for this to happen. If that resin had been on there a season or two - the water probably wouldn't have done a thing to the resin. The blush on your boat isn't a big deal, but it is a good idea to keep this from happening again. The main concern is that the lay-up is tight with no air bubbles or "pockets". If there are, water will find a way in there.

Just as a side note. I like what your doing with that project. Looks great. DAMN winter.

Thanks for the reply gents. It has been a very slow project since I started two years ago. But I like it that way. I get to plan and dream in intricate detail, and have been having a great time collecting all NOS bling. My family is now heavy into geo-caching and just enjoying the outdoors. The boat is cozy in the car port and will wait patiently for me until the spring. That is when the real fun begins... installation of a new balsa floor. Oh yes, and I am now posted permanently ashore and my career will see no more time at sea. I will miss it, but my wife and kids are sure glad I am at home.

I assume Poly Resin means you used polyester based resin. The polyester resins are permiable so they will absorb moisture, they will not pass liquid "water" but will absorb water molecules. Epoxy resins are far superior to polyester in this regard. Epoxy resins have better adhesion and are stronger. Epoxy cures to a tighter molecular structure.
I would highly recommend you switch to epoxy resins to do your balsa as it will limit moisture intrusion.I have done a balsa cored boat and it was easy to see that the original balsa had absorbed moisture in the exact footprint of the water line even though the boat never leaked and was well taken care of. It was due to years of moisture working it's way into the laminate from when boat sat in the water. Hard to beleive but true.
This process is also why you see some boats blister, it's moisture that has passed through the gel coat and reacts with the resins in the laminate that starts pushing the bond layer and pops it off. The absorption is similar to osmosis but not quite the same but might help in the understanding. My career involves me with adhesives and plastics and permiability is well understood some materials are better than others even though they may appear to be the same.
I always laminate a layer of fiberglass with epoxy resin to the inside of the boat as a first step after it has been cleaned back to the original laminate. This protects any wood structure as best possible from falling prey to this absorption. You can still do this prior to any balsa work you are going to do. You can argue that this is overkill but it is superior and does not involve any more work, just a different resin choice.
West Epoxy delves into permiability of common resins vs. epoxy on their website, intersting reading. My 2 cents.
So far your boat looks great...waiting for warmer weather here too!
Randy

Thanks for useful info. I will now paint the inside of hull when I am done glassing. I use a two part high quality epoxy on all of my metal projects. I never would have thought to use it to protect fiberglass poly resin. Thanks!! Dave 1959 Playmaster

That is great info Randy. Thank you.
So if I do the cored balsa with epoxy there should be no problems with it adhering to the existing poly resin on the interior hull and transom?

When I made the decision to stick with polyester, it was due to wanting to stay true to the old gals original materials.

Andrew

Epoxy will bond to the cured polyester with no issues but, I would grind the top of the polyester first to clean and roughen it up. Polyester WILL NOT bond well to cured epoxy so you cannot go back to it once epoxy is on there. Please note that cured Epoxy will have what's known as blush which is a sticky substance on the top surface after it has cured. This must be removed before subsequent layers can be added or they will not bond. It can be washed off with water,then dried and then surface roughed up with a grinder. You can keep laminating on top of not yet quite cured epoxy with no blush issues if you plan ahead and keep going. I generally que everything up so I can do all bonding/laminating in a day to minimize the times I have to remove the blush before going onto the next step. If you are going to paint over the cured epoxy this also needs to be done for the paint to stick. Do not have the epoxy exposed to the sunlight as it is not UV protected and will degrade. Either paint, carpet or UV blocking varnish/ polyurethane should go on. Doesn't matter where the sun don't shine...under floors and decks etc.
Epoxy has superior properties for adhesion, permiability and strength plus is does not smell like th epolyesters do! They are a little more labor intensive mixing the two parts and removing the blush but result in a better finished product in my humble opinion. Also, use the slowest cure hardner if working above 50 degrees or you will waste a lot curing in the mix container before you get a chance to use it.
West Epoxies web site has a lot of reading about proper use etc.
applicable no matter who's you use. raka.com has fabrics and epoxies at good prices. System 3 is also another epoxy supplier.
I generally get my glass needs from raka and my epoxy from West, only becasue I have used their stuff for so many years not becasue I think it is better. fiberglast.com is a good source to buy stuff from too, they also have balsa and plastic foam core materials too.
Randy