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Author Topic:   Bewildered by Epoxy
minimontauk posted 05-02-2003 01:30 PM ET (US)   Profile for minimontauk   Send Email to minimontauk  
This is probably covered in a thread somewhere, but there seem to be some real differences of opinion out there:
Having decided to first time paint my 15' Whaler bottom, I need to fill some minor dings and scrapes on the keel and chines that have exposed the green mat below. A visit to West Marine turned up at least 8 different products being sold as gelcoat patch, fairing compound, polyester putty, etc. I will be sealing the bottom w/ Interprotect after patching. Three different salesmen swore up and down the best thing to use was Marine-Tex (salesman #1) or 3M polyester fairing putty (salesman #2), or West System epoxy with 404 filler added (salesman #3). They were literally debating this in front of me.
Since Im painting the bottom, color matching the patch work isn't an issue. I'll use Spectrum Gelcoat Patch topsides for screwholes. The bottom dings and scrapes were caused by beaching originally, so I want something tough enough to withstand an accidental touch landing, without being so hard I end up sanding through the surrounding intact gelcoat trying to fair the stuff out. In confusion, I bought two small packages of Marine-Tex, not yet opened. What's the consensus, given my particular situation?
glassman posted 05-04-2003 03:12 AM ET (US)     Profile for glassman  Send Email to glassman     
Word to the wise. First off never take a salesmen word on how to patch. Would you let an auto salesmen or a machanic tell you how to do a valve job. This looks like a job for ....
First off patch polyester with polyester.Save the epoxy for wood, depending on the type or a hollow foam core composite. Since you've gone through to the green CSM(Chopped strand mat)check for soft spots caused by the rollers by tapping the area and listening for a change in tone. If there is you should fix this problem more so in the keel. If you just put gellcoat over a soft spot unless you move the roller locations when it comes in contact with that same sorce the gell will crack.If it is soft no problem. Since your showing raw glass anyway sand the area about an inch bigger all around. Drill some 1/8" to 3/16" holes along the soft area spaced at 1 to 2 inches apart, depending on leingth of soft spot. Put white masking tape over all holes left and right of center hole. Inject a mixture of catalized polyester laminating resin."no wax" into center holes as it fans out you will see the white tape turn dark when resin fills holes. If soft spot is long move a few holes down and do the same thing.Majority of these hole are just used to see the travel of resin to make sure it flows through whole area.When dry tap check again.If good, pull tape sand holes wipe with Acetone glass back with 4 layers 3/4oz mat or 2 layers 1,1/2oz mat useing the laminating resin with surfaceing ajent added (wax) because you' will need to sand smooth. Use a metal or nylon roller to roll out bubbles in mat it looks like a roller made of a bunch of washers butted together. Get a 3" x 3/8" daiameter roller.- ( Now... you can ask a saleman to help point it out to you. This time they won't be dissagreeing with each other eigther)- Re-gel with polyester gell any color or to save money just brush two coats of your laminated resin over the patch. First coat straight lam, second coat wax added since it will have bottom paint on it anyway it won't matter if its clear. The amount of surfaceing ajent to add is roughly 2 to 3 times the amount of catalist used. By the way surfaceing ajent is just styrine with parafin wax in it. the wax desolves in the styrine which is the naturel thinner for resin and the parafin floats to the top seeling it off from air contact. Most polyesters are laminated which stays tacky when in contact with air for multiple layer glassing. If I can help with any other matters, remember I am the ( GLASSMAN )

glassman posted 05-04-2003 03:24 AM ET (US)     Profile for glassman  Send Email to glassman     
Pardon the spelling and gramer. I just noticed some mistakes. I'm a blue collar guy. Beer over wine, beef jurkey over caviare.So for the dude checking everyones speeling. Have a cold beer and relax.

[Actually, it appears that there are far more people who complain about other people complaining about spelling than there are actually people complaining about spelling. --jimh]

doobee posted 05-04-2003 08:06 AM ET (US)     Profile for doobee  Send Email to doobee     
If you have delamination, Glassman has it covered. The delaminated area will sound hollow if you tap it with something solid.

However, it sounds like you just want to fix some minor chips and scratches, and these are not necessarily a sign of delamination. If you are just trying to get the bottom smooth, use some West System low density or microlight fairing filler. It is a powder that can be mixed with either polyester or epoxy resin, to produce whatever consistency desired. It sands very easily and it's durable enough to do what you want. If you're working upside down you may need to add some silica to thicken it. West publishes a free user's guide that explains the whole process very well. They should have it at E&B. I know Hyannis marine and Bosun's have it.

jimh posted 05-04-2003 10:56 AM ET (US)     Profile for jimh  Send Email to jimh     
Having been in the exact situation minimontauk describes, I made repairs using epoxy. The results were excellent, as I describe in an article.


I suspect people tend to use materials which they are familiar with and that they have on hand. Or, if doing the job professionally, the cost of the materials may influence the choice.

Epoxy has a higher cost, but the packaging is very convenient, the stuff cures to a hard finish without having to buy PVA or wax additives, it produces a stronger bond, and it can be top coated with gel coat if desired.

glassman posted 05-05-2003 06:27 AM ET (US)     Profile for glassman  Send Email to glassman     
Sorry for the misunderstanding minimontauk.When you said you went through to the green mat. I assumed it was from repeated pounding or rubbing in the same area and a "possible" soft spot mite have occured unbenounced to you. So I just thought I'd cover you on that incase it was so. With that said, I'll think I'll step a side now, don't want to start debating in front of you (like those three salesmen)with jimh. If it's just a bunch of dings and no soft spots. Then just patch it with any of those products the 3 salesmen recomended, they will all work. Follow the instructions then bottom paint. If you have any major damage in the future drop me a line.Good luck with the job.
minimontauk posted 05-05-2003 12:59 PM ET (US)     Profile for minimontauk  Send Email to minimontauk     
Thanks, Glassman. I was having a heart failure reading your post till I realized you were assuming worse damage than I have. I spent about 4 hours under the boat yesterday scrubbing the bottom with acetone to get the wax and dirt off. I got a good close look at the damage. The scrapes are just through the gelcoat, no apparent glass or core damage. One question, what's the rationale for sanding the dings before infilling with putty? I can see removing the loose or cracked surrounding gelcoat, but why enlarge the damaged area? Won't any sharp edges be sanded out while fairing the patch anyway?
glassman posted 05-06-2003 04:10 AM ET (US)     Profile for glassman  Send Email to glassman     
Your correct in a way mini. The comment I wrote about sanding the area 1" bigger and such. Only applies to that soft spot repair I talked about. Reason being with the drilled holes down the center of the keel. When you glass it back in layers, pyramid style, one layer slightly smaller then the first,next inside of that and so on. The area of focus which are now the holes has most of the protection.The pyramid style doesn't leave a hard edge and helps with the fairing out prior to gellcoating. But back to your chips and dings. I'll try to be quick about why you have to sand dings also. Useing this example. Lets say you have hardend resin in a wax papper cup about 1/4" thick for example. Nock it out of the cup and you have a resin pancake. The smooth side would be your boats finish. Now snap it in half. Look at the broken edge, you'll see it's just as slick and shiny as the top. No patch will stick to this surface. Your dings are probably on a smaller scale but basicly when gell gets knocked or chipped even if you don't see the smooth surface, trust me it's there. Sometimes when you get dings theres undercuts on them. Undercuts are dings that are kind of like a dovetail joint in wood working. If you have undercuts in gellcoat they need to be knocked off and turned inward 45 degrees because ther is no fibers in gell holding it together, That sharp point will split at the inside angle. Dove tail repairs are handy in certain situations when doing through glass hull repairs.Don't worry, I wont go there. As for sratches,you can't exactly sand in some of them and sometimes, you can just putty over them and they hold up for some time, Self etching primmer might do the trick prefably clear, like the glass etching type but since your going to paint the bottom, the color type is cheapest. Hope that helped, (GLASSMAN)

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