Thursday, August 8, 2013

My Own Private Hell

I knew after the success of the previous days epoxy job would come more sandinsanity. The fabric edges would have to be feathered out and the bottom/sides would have to be roughed up for the next and last layer of fiberglass.

I started out going gangbusters at 08:00 and clipped along for a couple of hours getting about 1/3 of the way down one side. After the first break things kinda slowed down as the temperature shot up in the shed. At one point it was 85 F and climbing. I scrambled the fans to get some air moving.

Probably the best $40 I've ever spent at Lowes. "Big BJ" can move a lot of air. I'm half contemplating getting another next time I cross the river.

My new air sander hasn't quite got the guts the old one had. That and having to use 60 grit instead of 40 slows the process down quite a bit. I've got to get the binder threads down flat and it takes a bit of doing with both the air sander and the block sander. The block sander is very efficient and removes a lot of material.

So after 6 hours of sandinsanity I made it all the way down one side about 2/3's of the way up the bottom panel. I'll have to climb on top to do the rest. Putting that off for a cooler day. It's at least 5 to 10 degs warmer up there!

One of my friends on Facebook asked me why I sand so much. Well that's pretty simple. This thing is too big for one person to be able to work wet on wet (chemical bond before 24 hrs) and I have to let the epoxy cure between layers. The fabric leaves a hard edge that has to be feathered out so I don't end up with voids when the new layer bridges the hard edge and the fiberglass has to be sanded after 24 hrs to give the new epoxy something to grab onto (mechanical bond). It also helps to eliminate any small imperfections that might print through.

The downside is you end up sanding off a lot of expensive material you just put on. Most of it ends up like this.

If you look closely you can see the binder threads holding the warp and weft (tows) of fiberglass together. This fabric is not knitted like a conventional fabric. The bundles of fiberglass (tows) are laid in a straight line and cross at 90 degs to one another. The binder thread holds all the bundles in place. These binder threads don't add anything to the structure of the fiberglass and stand up (proud) of the surface. Sanding them down allows the next layer to get in closer contact with the previous layer which is important for structural reasons. It also avoids small bubbles that can develop within the cells left by the binder threads.

I did take a few video's with the GoPro camera. I'll see if there's anything there worthy of publishing on here later.

Today's Boat Shed Tune: My Own Private Hell by Alice in Chains

*Sigh* So endeth the lesson for today. I'm pooched and in desperate need of a shower.