Do I need another coat of epoxy?

Builder's Forum
1

Hi folks, I have been sanding and sanding.  Unfortunately I don't think back when I epoxied the first time I did a very good job of it, and there are some really big bumps where the deck fiberglass overlaid the hull fiberglass.  i recall (and believe it or not, this was 7 years ago when I started...life gets in the way sometimes) that I wasn't happy with how the fiberglass shredded at the edge...  anyway, it left bumps that were tough to sand out.  I think I did the job, the hull is silky smooth...at least to the touch, but I still need to sand with 120 and 200 grit.

 So here is my problem.  I can SEE the pattern of the fiberglass beneath the epoxy.  I can't feel it, and except a few very small places, I don't think I actually nicked the glass.  But it shows as a light hashmark pattern in many spots on the hull and on the deck.  I have a few spots where there is a pepper spray pattern of unsanded glass (little tiny tiny pockets peppered on the deck).  So I KNOW I need to sand more...but I'm worried about those hashmark patterns.  

Here are the photos: ( i tried to upload photos, but was not able to get it.  Hopefully these flickr links work.)

 Photo 1:  Never mind the swirls.  I know I have to sand more with a finer grit.  This was from 80 grit paper.  

http://www.flickr.com/photos/slowduck/3577657604/in/set-72157618984530694/

 

Photo 2: Another view of the hashmark pattern.

 http://www.flickr.com/photos/slowduck/3577658362/in/set-72157618984530694/

 

Photo 3: The deck with hashmark pattern and pinpoint high spots

http://www.flickr.com/photos/slowduck/3576854985/in/set-72157618984530694/

 

Photo 4: Uhg, the pattern keeps rearing its ugly head.

http://www.flickr.com/photos/slowduck/3577659474/in/set-72157618984530694/ 

 

My questions are:  Is this an indication that I've sanded too much epoxy away?  Is it an indication that I'm ABOUT to sand through the fiberglass?  If so, do I need another coat of epoxy and then repeat all the sanding I have already done?  I'm hoping that isn't the case, but I suspect that it is.  

I thank you in advance for any help you can provide today/tomorrow since I actually have time to either sand or apply epoxy tomorrow afternoon.

 

Bill  

 
 
2

Hey Bill,

First off, I'm assuming that you're going for a bright finish? Try running a wet rag over the patterned area. That'll show you what it would look like if you varnished right now. If you still see the pattern when it's wet, you're stuck with it and may want to consider paint. Extra epoxy won't cover it if you can see it while it's wet. But from your picture, it looks as if you're fine.

In the meantime, from what you said and the pictures, it sounds to me that it's time for another coat of epoxy and to switch to a finer grade of paper. On my boats, when I start seeing the weave pattern and still have the glossy dots, I go to #220 paper.

When you put on the next coat, try this:

1. Only mix up 3 ounces of epoxy/hardener

2. Apply it with a short nap roller, like the yellow ones CLC sells

3. Tip out the coat with a foam brush to get rid of the bubbles

This will give you a very thin coat, so thin that new runs will be impossible. 3 ounces may not sound like much, but it's enough to entirely cover  a CH16LT hull at your stage of construction. Put on 1 or 2 coats, sand with #220 and repeat until the glossy dots have gone away.

Good luck,

Laszlo

 

3

Hi Laszlo,

 Thanks for the fast response.  I think this is probably a good scenario for me.  Ideally, I'd love to finish the kayak 'Bright', Although I have considered painting the hull and varnishing the deck.  I go back and forth because there are some blemishes (where I sanded to hard with a bad sander and burned the wood at the scarfs for example), but often I look at those and think they add real character and beauty to the hull. 

For the most part, that pattern doesn't show when the boat is wet.  It really looks beautiful.  I wish there was simply a way to keep it wet all the time!  What makes that pattern?  Why does it show through that way? 

 I'll throw on another thin coat, very thin coat! like you said.  Drips are my nemesis, so it will be interesting to see just how thin I can make it.  While this adds a day or three to my project I"m not sure how much that matters after 7 years! 

 

Bill 

4

Laslo,

Bill seems to be happy with your reply, but I'm confused. First you say he is probably fine, and then you tell him to put on another coat of epoxy. What is the reason of the additional coat? I always get areas where the weave is visible when dry, but passes the wet test. Once varnished, the bright finished areas look OK.

Jim

5

Jim,

He's fine in regards to not having sanded through the glass. The extra coat is for filling the low spots, the ones that are making the glossy patches.

Bill,

Yeah, what's another couple of days? I'm in the process of finishing a dinghy that I started 7 years ago. Since I started it, I changed jobs twice, started and completed 3 other boats and spent lots of prime building weather paddling. What's the hurry, right? As long as it takes less than a year per foot :-)

As far as what makes the pattern, as long as you haven't sanded through it's just the difference in the index of refraction between the epoxy and the glass. Adding a thicker layer of a transparent substance (epoxy, water, varnish, etc.) makes the transition less abrupt. Purist opticians, I know that's simplified a lot, but this is a boatbuilding forum.

Laszlo