Hi!

I crawled under my trailer and took a couple pictures of the wear/damage on the bottom of the hulls of my Nacra 450. Looks like the gelcoat is worn off both of them in the same place, right before it curves up to the transom. About 4-6" long by 1" wide. From these points forward, it's worn off a little, but not near as badly.

First pic here is of the port hull, next pic on next post will be of the starboard hull. Last pic, 3rd post, will be of the port hull, forward of the first pic.

I've never repaired gelcoat. I think I got Meguire's products for taking out scratches and minor blems in the gelcoat. Got that problem on another boat. The cat hull skeg repair would need new gelcoat or epoxy or whatever. I've read a little about gelcoat repair. West System is mentioned a fair amount.

So what is needed here, and what are the different methods? I'll checkout a book or 2 at the library. Vaitses and Wiley are 2 authors.

Also, this damage was done, I'm sure, by beaching the cat by the previous owners. I won't be doing that much beaching at all. So what if I do nothing to it now?

Go Seahawks,
Danno

And here's the area forward of that bad spot.

and finally, the bottom of the starboard hull. Looks like it was repaired sometime before, too.

You can do this repair yourelf. Buy white gelcoat. You can get it from West Marine if there is a store near you if not www.fibreglast.com will sell you what you need (you can also call them for how-to advice). Gelcoat is sold in quarts (you'll only need one quart to do all the minor repairs you have) with catylizing agent (MEKP, which you can buy at Home Depot). Mix only what you can use in 15 minutes or less (I'd go with 4 ounces, maybe 8 tops). Apply with brush (use a dispoeable or clean IMMEDIATELY with acetone). You may need to apply more than one coat, sand with 180 grit between coats and then after final coat use some 300 then 600 grit. I wear disposable gloves and old painting clothes.

But before to do this I would suggest you prepare the old surface first

1, Clean well with water
2, rough up the exposed glassed areas with a very rough file
3, clean with acetone

Steps 1 - 3 should ensure a good physical and chemical bond.

If you have some volume to return (say on the bottom of the skegs etc) when mix up the first batch with micro ballons (the website quoted will know what these are - but they are exactly what they sound like) or chopped up glass matt, this will allow the gelcoat to be formed into more robust shapes (and will be almost bullet proof afterwards)

When applying the gelcoat, it must be sealed in order to 'go off' properly. The best method by far is to use Cooking (tin) foil.

When filling small 'dinks' or holes, clean as above, fill the hole with Gelcoat and then cover with smoothed out tin foil - if done properly, you will need the minimum sanding afterwards to get a good finish.

When repairing skegs etc, the tin foil can be used to shape the mixture before it 'goes off'

Read the instructions carefully, they should contain curing times for various temps.

When sanding back (you should always put too much on, even when using the foil method) you will need to got from

a course file (depending on volume to remove)
Fine file
80 grit wet and dry
160 grit w/d
400/600 grit w/d
and finally 1000 grit w/d

Good luck

The gel coat will not cure with out a barrier to the air, it must be completly sealed off. Use a wax that is designed for this. You mix a small amount in each bach and it will allow the gel coat to harden. Ask about it at the marine supply store. I think you can alos use sheets of mylar too.

Thanks, guys.

So about getting an air barrier to promote curing...

Are there types of gelcoat that don't need this, or have the wax premixed? And as far as the wax goes, it 'knows' where the outside is, cuz it's 'downward' on this skeg repair.

Cellophane wouldn't work, cuz it would be disolved?

How do you seal airtight with aluminum foil? Tape the edges?

Ciao,
Danno

It only needs to be 'fairly air-tight'

If you do not seal gelcoat, a small top portion of the gell does not 'go off' not the whole lot.

I've never used wax in 25 years - I am sure tin foil will be cheaper !

I would use PVA mold release available at West Marine. This stuff sprays on and creates a barrier then it just washes off. Much better than dealing with wax.

Mike Hill
Tiger #1520

Thanks again, guys :-)

I'm also sure it would be much easier to turtle it and work on the skegs that way, as opposed to working from underneath on the trailer. Too many Vicodin from my knee surgery?

Danno

I spent waaaaay to many hours re-gelcoating the bottoms of my old Hobie 16 and finally just got tired of doing it. The boat was getting old so I decided to just use Marine Tex and was never happier. The advantage is that (a) the stuph cures slowly giving you plenty of time to work, (b) is thick so it spreads easily to where you want it and to the desired thickness (don't get me wrong, its gluey and takes some patience to work with, but worth the effort), (c) sands/fairs very well and (d) is harder than GelCoat (at least it seems like it to me.) The only disadvantage I found is that MarineTex is not quite as white as gelcoat and seems to be a bit more porous and will suck up stain in some kinds of water. However, with the small strips of wear and (you show), the marine tex--if it stains, can't be seen when the boat is right side up. You Do spend most of your time right side up, right?

Just something to consider.

So far, I have spent most of the time upright. But I'm just beginning.

Is MarineTex an epoxy? I've heard these are stronger.

Danno

Add styrene wax to gelcoat and mix. Then add catalysis (MEK). No mold release necessary. Equal parts of styrene and catalysis.

In this thread the catalyst has been referred to as MEKP (correct) as well as MEK (incorrect!). Since Home Depot was mentioned as a source of MEKP, you can also find MEK there and naively think the MEK will catalysis your glass. You’d wait a VERY long time…forever. The "P" is really the key, Methyl Ethyl Ketone PEROXIDE.

Watch your chemical shorthand. NO mistakes! A Google search of MEKP will lead to you to a lot of pyrotechnics sites. That stuff can be hotter than you think! Be careful!

Never, NEVER underestimate home chemistry.

David,

And I just finished my lunch...yuck!

Is that injury from explosion or chemical burn?

Sorry about the photo. I had just looked up MEKP and read how it can be used in home "entertainment" for Bevis and Butthead types. The site did include a warning and that photo of explosion results. After years of teaching organic chemistry, I can assure you it's easy to hurt yourself with organic reagents, especially peroxides.

Let's see if I can attach a photo of those pyro type guys...

Typo. MEKP is the right stuff.

Danno,
I've done hull repairs for over 20 years on my cats. I've done them both ways with fiberglass and also with marine tex. It is my opionion that all the fuss of doing it with fiberglass is not work the effort. Marine Tex has worked fine on my Supercat , Inter and Hobie catamarans. If you are going to do it don't worry about sanding the bottom perfectly smooth. Let the sand on the beach do it. Also don't mix it in a big glob because it will heat up fast and cure before you know it. After a year or so just do some spot repairs with marine tex if you need it. Just depends on how much you drag you boat on the beach.

Good luck,
I hope it works out which ever way you choose.

Mike

instead of tin foil, use wax paper. It works better and creates a very smooth higher gloss finish.

I just did a repair to a small ding (well hole actually) in my Tornado about 6 inches up from the keel line midway from the forebeam to the bow. The damage happened while lauching off my new trailer...boat blew sideways and hit the fender mount bracket edge. Only the outer skin of the hull was punctured, through to the foam, about 1/4" diameter.

Since my boat is painted (previous owner) a slight off-white grey, using straight white gelcoat as a finish would stick out like a sore thumb (or quite possibly a VERY sore hand blown apart by homebrew chemistry). Got a quote from the B.Y. repair guy...$600!!!!?!? So, there went another weekend for me. Used West System epoxy (whole boat is epoxy based) & light weight filler pl;us a little heavier density fairing filler for strength to fill the hole & surface scrape. I then used West Marine's gelcoat color match kit. It comes with a toothpast tube of clear gelcoat and a set of color tinting agents. I used a bit of white and a very slight amount of black to give a very close match. Used a little extra plus a bit more black tint to make a chip repair to my darker grey non-skid deck. Just "stippled" the surface a bit and sanded off the peaks later to give a real close match to texture.
Still got to do final fairing/polishing on the repair.

BTW, why do all the polyester based resins sold in West Marine state "Not to be used on epoxy"? I've never found any problem here.

Mike.