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Go Back   SailNet Community > On Board > Gear & Maintenance > Closing up holes in the cockpit
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Thread: Closing up holes in the cockpit Reply to Thread
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Topic Review (Newest First)
06-25-2009 03:16 PM
dgr MAS says:
"10. What is BLUSH, and how do I remove it?

Blush may form over the fast mix MAS Hardener and MAS Resin. The MAS Slow mix generally will not blush. Blush is noticeable as a slippery film formed over the cured surfaces. It can be removed with warm water and a sponge (rinse and wipe)."

I read that as their system uses amines in the hardener and both hardners will blush. I further read the MSDS (COMMON NAME - Cycloaliphatic Amine) as containing amines. From our resident epoxy technician, epoxymoron, I understand that blush is caused by amines and any amine presence in the product will potentially cause blush. If it was me, I'd just assume that there was blush present and take the 10 seconds to rinse and wipe before I started sanding.
06-24-2009 09:06 PM
roline There are two epoxy systems available to us, polyamide and polyamine. The polyamine systems will react/mix with a little moisture in the air and forms amine blush slime layer as a function of cross linking. The polyamide system manages to crosslink without is side effect. An example of ideal application is underwater epoxies, amine epoxies react with the water and are not suitable.
I was a strong fan of the West system, used it for yrs, had difficulty in finding it, local stores switched to MAS. I was quite vocal about not liking the change until I tried it. To gel coat over it still requires proper surface prep, just less amine blush to worry about. MAS is an amine based epoxy, Ive used the slow and medium hardeners without experiencing any blush. (They do market it as blush free)

Blush is a reaction of moisture and carbon-dioxide in the atmosphere with the hydroscopic nature of the " simple amine" compounds due to excessive free radicals that are present during the reaction/ curing process. (very common in the lower end epoxies) Cycloaliphatic diamines / Cycloaliphatic Amines are almost completely void of the free radicals that hydroscopicly react making them inherently the most stable to not forming "salts of amine carbonate" aka, blush, but this comes with a higher price tag. Another down side is that they have difficulty in being reactive at low temperatures.

Be wary of those that try to appear larger than life by attempting to make everyone around them appear smaller.
06-24-2009 02:18 PM
jarcher
Quote:
Originally Posted by sailingdog View Post
If the fiberglass is that thin, it won't support its own weight... How big are these holes??? I seriously doubt the fiberglass is less than an 1/8" thick at a minimum.
Oh it's probably 1/8 or so. I got the impression from his diagram that it was expected to be thicker.
06-24-2009 10:17 AM
zz4gta I would've found access to the back and put a wad of 5200 on the back of the screws. Done.
06-24-2009 08:20 AM
sailingdog If the fiberglass is that thin, it won't support its own weight... How big are these holes??? I seriously doubt the fiberglass is less than an 1/8" thick at a minimum.
Quote:
Originally Posted by jarcher View Post
Thanks for all the tips! One thing I am concerned about that i did not mention, the fiberglass in the cockpit is very thin, probably no thicker then the gel coat. Your picture made me think about that. The epoxy won't fill a deep hole with sides, its a hole that is much wider than it is deep. How does that impact it?
06-24-2009 01:15 AM
jarcher
Quote:
Originally Posted by dgr View Post
J,
I think you want your gelcoat to be a little thicker than that. 15-25 mils. But, on a repair of that size, if you prep properly and finish level, you can hardly avoid getting the correct thickness -- or at least the thickness of what you already have on the boat. Here is a picture that may help illustrate. Sorry it is so crude.



That is where you should be prior to sanding the new gelcoat down. The new gelcoat, if you catch it soon after it is hard, will be much softer than the old gelcoat and it will be easy to sand it flush.

For small, unobtrusive holes, you may find that marine-tex is "good enough." It may also help you get started with a white pigment base on what you are trying to accomplish.

I like using PVA to overcoat the final gelcoat layer to exclude air during cure. It's really easy to remove. But, it's something else you have to carry around/store. You can also buy a wax additive you add to the last batch of gelcaot or you can buy regular and finishing gelcoat.

The gelcoat that west marine sells kicks REALLY fast. Good for small areas; not so good for larger areas or working in the heat. You can always speed up a slower setting gelcoat with a heater and/or more catalyst.... You might get enough thickness with gelcoat paste.
Thanks for all the tips! One thing I am concerned about that i did not mention, the fiberglass in the cockpit is very thin, probably no thicker then the gel coat. Your picture made me think about that. The epoxy won't fill a deep hole with sides, its a hole that is much wider than it is deep. How does that impact it?
06-23-2009 06:12 PM
dgr J,
I think you want your gelcoat to be a little thicker than that. 15-25 mils. But, on a repair of that size, if you prep properly and finish level, you can hardly avoid getting the correct thickness -- or at least the thickness of what you already have on the boat. Here is a picture that may help illustrate. Sorry it is so crude.



That is where you should be prior to sanding the new gelcoat down. The new gelcoat, if you catch it soon after it is hard, will be much softer than the old gelcoat and it will be easy to sand it flush.

For small, unobtrusive holes, you may find that marine-tex is "good enough." It may also help you get started with a white pigment base on what you are trying to accomplish.

I like using PVA to overcoat the final gelcoat layer to exclude air during cure. It's really easy to remove. But, it's something else you have to carry around/store. You can also buy a wax additive you add to the last batch of gelcaot or you can buy regular and finishing gelcoat.

The gelcoat that west marine sells kicks REALLY fast. Good for small areas; not so good for larger areas or working in the heat. You can always speed up a slower setting gelcoat with a heater and/or more catalyst.... You might get enough thickness with gelcoat paste.
06-23-2009 02:38 AM
jarcher
Quote:
Originally Posted by TomKeffer View Post
You're on the right track.

It's easier to get a smooth surface if you pile the epoxy on a little proud, then sand down so it's slightly (very slightly) concave.
I need 10 mills for the gel coat, right? That seems like a lot. If the area being filled is concave, then the gel coat will be very thin at the edges of the hole. Will that cause it to fail?
06-22-2009 10:21 PM
TomKeffer
Quote:
Originally Posted by jarcher View Post
Thanks. Once the epoxy hardens, it is likely to be flush with the gel coat, so I guess then the thing to do is sand it down to make room for the gel coat?
You're on the right track.

It's easier to get a smooth surface if you pile the epoxy on a little proud, then sand down so it's slightly (very slightly) concave. Masking the surrounding area helps avoid scarring it, but usually any blemishes will get buffed out by the final sanding job. Specialized sanding tools can help (I use a Fein Multimaster).

Gel coat paste is easier to use, especially on vertical surfaces: it's not as runny, so it won't form drips. Also, make sure you don't get the air-inhibited kind. If you have to cover it, it's just about impossible to get a smooth initial surface.

As for the ear plug 'trick', it's in the West System's "Fiberglass Boat Repair & Maintenance" booklet, section 7.1.1 in my copy. I suppose one should first make sure that the plug you use is not made of closed foam!

I am by no means an expert! Just a weekend hack. But, you should be able to get something that looks acceptable.

Good luck

-tk
06-20-2009 10:16 PM
jarcher
Quote:
Originally Posted by TomKeffer View Post
If the epoxy was properly mixed (correct hardener ratio) and cured, and if you're careful to remove the amine blush (soap and water followed by 100 grit sandpaper), gelcoat will stick just fine to it.
Thanks. Once the epoxy hardens, it is likely to be flush with the gel coat, so I guess then the thing to do is sand it down to make room for the gel coat?

Today I went to West marine and they had an epoxy repair pack, or something with a similar name. It came with 4 plastic cups, stiring sticks, a brush, gloves, a syringe, 4 alcohol wipes, some matte, two different thickeners and some packets of resin and hardener, already measured out. This was about $35.00.

I grabbed one, and I also got a set of plastic putty knives for another $9.00. I decided to try on the holes that are on the under side of the cockpit and above the quarter birth. These holes allow water that somehow leaks through the cockpit to drip onto the quarter birth cushion. Since the cushions are only a few weeks old I wanted to fix this soon.

When I got to the boat, I realized that I forgot to get the white coloring agent they sell, but I decided to do the project anyhow, since no one can really see these holes unless they are lying on the bunk.

I carefully cleaned around the holes with soft scrub, then sanded them down. I then used a countersink bit, in reverse, figuring this would give the epoxy something to grab. Its not a 12:1 bevel, but creating that bevel with such small holes didn't seem feasible. Then I cleaned again to remove the dust and any loose material.

What the kit didn't come with were instructions. Fortunately I had just read the West epoxy users guide this morning. I mixed the resin and hardener in one of the plastic cups, for a solid minute until it was consistently clear. I then mixed in some thickener, and kept adding it until it was uniform and the epoxy was like peanut butter.

I used the stirring stick to apply it to the holes and a plastic putty knife to smooth it. I was able to get all the holes done before the pot time was exceeded, probably 15 minutes (it was cool today). This did result in a lot of epoxy smeared around the holes. I was trying to make it thin to minimize the sanding later.

Looking back, I wish I had gone back for the white coloring agent, so I could see how it would look when cured. Also, it occurs to me that I could use painters tape around the holes, to prevent the putty knife from smearing epoxy where I don't want it or need it.

I left after about 4 hours, and it was starting to rain. The epoxy seemed to have hardened, although I know it didn't cure fully by then. I'll go back tomorrow to sand it.

I don't need to gel coat this set of holes, but I might as a test. Last time I gel coated a vertical surface, I didn't thicken the gel coat and had a miserable time. Now I know better.

I am also going to look into the ear plug idea.
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