Newbie Q: To Seal or Not?

[rgball]

Hi, I'm a novice builder attempting to build a 15ft prospector. I'm almost finished sanding the hull and getting nervous as I prepare for the fiberglass. In the reading I've done it seems some advocate applying a full coat of epoxy as a seal coat before laying the fiberglass while others say it is not necessary. My question is - what are the advantages of not using a seal coat? Sorry if this has been asked/answered - I could not find it elsewhere on the forum.
Thanks
Rick

[Patricks Dad]

Rick, Welcome to the forum. You've asked an age-old question. Different people have different views. Personally, I never pre-coat. The arguments FOR pre-coating are to ensure an even and consistent coat of epoxy before you have to contend with glass and avoiding any places where the glass is "starved" because the (unsealed) wood below absorbs too much epoxy and you don't put enough on in those places. Theoretically, you would produce a slightly lighter result this way as well.

Arguments for not sealing are:
1. You don't have to worry about sanding between the sealer coat and the glassing job. If I were to sand the sealer coat, I would no doubt sand through the sealer coat in some places rendering the reasons for doing it in the first place moot.
2. You don't have to worry about glassing soon after applying the sealer coat (to avoid sanding) - just after it is no longer tacky so you can get a chemical bond but before you would need to sand to achieve a mechanical bond. I've never figured out how I would do this. I like to drape my glass on the hull the night before and start applying epoxy very early in the morning so I can do all the coats in one day. If sealed, I'd take at least an extra day and find myself sanding the sealer coat - and probably not making that final coat by the end of the day and then sanding before the final coat). Imagine trying to drape your glass on a hull with a sealer coat and doing it a bit too early (while the coat is still tacky).
3. In my view, if a particular piece of wood wants to absorb additional epoxy, I'd rather let it have it for the strength rather than give it a thin coat to save weight (the deeper the penetration, the better bond you will have with the glass. It does require that you pay attention as you glass to look for places that look thirsty and give it some more to ensure it is covered.

I'm sure others will comment with pros and cons on the subject. Some guys seal. some don't. Each camp has it's zealots and are convinced their approach is optimal (and they may be - for them).

Best of luck on your project.

[BearLeeAlive]

I too debated this in my head a lot, and went the same way as Randy. No regrets.

[rgball]

Thanks for the feedback. This is exactly what I was looking for - primary reasons guys don't put on a seal coat. It will be helpful in the decision making process.
Thanks.

[Jim Dodd]

Welcome also to the site !

I always seal.
1. It fills small voids, including staple holes. For staple holes, after I roll on the seal coat, I wait about an hour, and come back with a small foam brush and recoat the staple holes. This really seals them.

2. I don't believe it adds weight. It will reduce the amount of resin you need for the first wet out coat.

3. Peace of mind, any problems that show up can be fixed before going on with the cloth.

As always I believe it's a builders choice. My 20th is on the forms, and it will get seal coated.

On the negative side Dust particles WILL stick and need to be SCRAPED before adding cloth. The dust will lift the cloth away from the hull if you don't !

Good Luck !

Jim