The Eighth Deadly Sin

March 7, 2015  Hours spent building to date:  786

Saturday Faired

As I was adding the fill coats to the Xynole, layer after layer, there was always a spot on the third panel from the bow on the starboard side that I didn’t trust.  It was sort of greasy, a couple times I thought I saw a bubble coming up.  As the rest of the boat got harder and harder with a reassuring “thwack” to the knuckles, this area was more of a “thunk.”

So before I started final sanding of this area, I decided to simply grind it out and see what was happening.  There was no way I was going to fair and paint an area to which the final surfacing might not adhere.  I thought it was about a 5-inch square weak spot.

About three seconds into the grinding, I knew I had a bad, bad problem.  The cloth shed away, and I could see shiny resin — uncured resin — underneath.  I took a chisel to the area, and the glass started peeling away over a two-by-three foot area — not easily, but in a way that showed Ray and I had committed the Eight Deadly Sin — wetting out glass using a batch of epoxy with no hardener.

Here’s what happened:  I was up on the boat wetting out the cloth, but got down for some reason to clean up a spreader, or move the staging or something.  While I was down, I grabbed a cup of epoxy from the mixing area.  “Hey Ray,”  I asked, “Is this mixed?”  He was busy doing something else and said, “Yes.”  I thought about it a second, and forged ahead.  That was the real Sin — if there’s even the slightest shadow of a doubt about a batch of epoxy, you put it aside.

In 15 years of amateur boatbuilding, I remember this happening three times — twice the epoxy had been carefully mixed, and when it hardened it was simply a throwaway.  Once it turned out that it had no hardener, but no harm done.   This time there was no hardener and despite everything I know about epoxy, it went on the boat.  So the odds of a disaster from this sin are about 50% — not in the area of Wrath or Lust, but certainly in the vicinity of Gluttony and Sloth.

The penance is not hard, but long:

1)  Totally remove any suspect glass.  Grind down edges to absolutely adhered material.

2)  Paint out affected area with hardener-rich epoxy to get a totally clean and hard area to work in.

3)  Sand again and cut patches. Wet out patches. Let dry and sand.

4)  Fill with epoxy-microballoon mixture.  Sand.

5)  Fill all edges that are not covered with glass with what I call “strength filler”  — a mix very heavy on microfibers and colloidal silica, with some low density filler so it will sand.

6)  Sand and fill with epoxy until patch is level with surface.

7)  Apply fairing compound to voids to smooth surface.  Sand again — seventh time.

The area won’t look great until after the final fairing, but it is smooth and strong.  The one positive I got from this was that the filled, unadhered Xynole I peeled off was as tough as Kevlar body armor.

In other news, I have been sanding the hull and fairing for the past six days minus a day off for the weekly blizzard.  The boat is looking really good, and in another week will be ready for paint.

 

First look at the problem.

First look at the problem.

Patches on.  Smaller areas are where I had touched up with resin-only.  They were almost adhered, but I didn't trust them.

Patches on. Smaller areas are where I had touched up with resin-only. They were almost adhered, but I didn’t trust them.

"Strength filler" is on the edges

“Strength filler” is on the edges

First coat of fairing

First coat of fairing

Patches are sanded and ready for final fairing

Patches are sanded and ready for final fairing

 

 

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One comment on “The Eighth Deadly Sin

  1. Denny
    March 9, 2015 at 5:52 pm #

    That sucks!

    Could have been worse though, could have been on the side where all patches would have to be much more carefully faired.

    Could have been really worse and the epoxy failure gone unnoticed.

    Like

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