August/September 2018

August 14.

The rough sanding of the hull has commenced.  This is going to be a bigger job than I thought.  The idea is to rough sand the seams and high spots, fill in the low spots and ripples before applying the 3 or 4 covering coats of epoxy.  These covering coats will fill the weave and create a smooth finish.  They will also allow enough epoxy over the glass to perform a final sanding before paint application.

I  settled on a very powerful 6" angle grinder (Milwaukee) with a very rough grit (24) to take down the areas where there is overlap in the thick mat glass.  My belt sander is not up to this task but will be used to clean up and smooth out the work from the angle grinder.  This is a grinder I typically use for heavy steel grinding and concrete cutting.  I have a soft flexible sanding pad which keeps the pressure to a minimum.  It works well with some skill.  You can cause a lot of damage very quickly with one of these.  I did make a few mistakes (one which will require a little re-glassing in one small spot) before I got the technique down.

One of the tricks is to start the grinder/sander with the disk resting lightly on where you want sand at about a 25-30 degree angle to the work.  This will keep the sanding disk from digging into your work.  Apply light even pressure at an angle sufficient to bend the sanding disk and keep the grinder moving along the work.  Your only sanding with about 30% of the disk at any time.  If your angle gets shallower, you will loose control and dig the center nut into your work.  Too steep and the disk will cut into your work.  It is a careful balance to keep things smooth and requires skill.  Check the work often by running your hand over the job.  I was surprised to find that normal visual cues to how well the job is progressing are misleading when sanding the encapsulated glass.  The glass is translucent and the texture of the wood can be seen through it.  This makes an optical illusion of sorts that distorts depth perception making it difficult to judge the surface.  Look for sharp edges along the seam that show abrupt transitions but stop often to run your hand over the work.  Don't try to take the whole high spot/seam down with the angle grinder.  This tool is way too crude for that.  The belt sander will finish the work up nicely.

On the right is the 6 inch angle grinder.  It is a beast and you should use lots of caution when using this machine.  On the right is my new 4" belt sander.  It has a very powerful motor that will take what you can give it.  In the rear is the old belt sander that just isn't up to the task.  Both the angle grinder and the new belt sander are very heavy and require quite a bit of endurance to use.  Take breaks often.  When your tired is when you make the worst mistakes.

I'm using the belt sander to clean up the work performed by the angle grinder.  My old Bosch belt sander was just not up to the task.  I did a little research and purchased a Makita 4" 11 amp belt sander.  I've been very happy with it although it does weigh nearly 12 pounds.   The belt sander is more forgiving and requires less skill.  It is important to start the sander with the belt on the work with light even pressure.  Once the belt is up to speed you can increase pressure but keep the sanding belt parallel to the work.  The edge of the belt will dig in quickly.  I do modify where I place pressure on the belt in order to modify the surface I'm sanding just don't let an edge lift off the surface.  On a horizontal surface, you can let the weight of the machine do most of the work, on vertical surfaces you will tire quickly so take a lot of breaks.  The belt sander is far more forgiving than the angle grinder but less aggressive.  It is possible to do the entire job with the belt sander if you have a good one.  It will just take more time.  I highly recommend forgoing the angle grinder if you do not have sufficient experience with one.

The dust is a killer though and requires a high quality dust mask or respirator.  I've chosen the high quality dusk mask and it works well.  The dust will also cause some serious irritation to your skin.  I'm still working out my protective clothing.  I tried to wing it and suffered dearly.  I'm now going with coveralls that have elastic at the legs and arms.  I use baby powder on my neck and face before I work to keep the glass dust out of my pours.  Protective clothing is a must.  I think you become more sensitive to these fine particles over time and this can lead to dermatitis.

You can see one of the seams that was sanded running down the hull.  You also need to sand high spots on the rest of the hull with the belt sander.  This works pretty quickly.  If you look to the lower left corner of the picture you will see a place where the grinder dug through to the wood.  At first I thought this was due to a too stiff sanding pad.  Although the sanding pad was too stiff, the root cause of the sand through was bad penetration of the epoxy at that point of the seam.  There was another small area where this happened and I took note.  These are easily fixed so don't panic.  

Yes, this part of the build is miserable.  The temperature outside is 95 F (35 C) and your wearing long pants, long sleeve shirts and your mouth is covered by a thick dust mask.  The dust is itchy and the machines are heavy.

September 9,

I spent 7 hours sanding on the boat today.  I'm tired, hot and miserable but I got quite a bit done.  Most of the really rough sanding is complete (for this phase) and much of the belt work is done.  The new Makita belt sander has a nice dusk pick-up bag.  It probably picks up 1/3 to 1/2 of the dust it produces.   I started saving this dust to use later as a thickener for the epoxy.  I'm not sure how well this will work so I'll make a few tests.  This should be high quality filler since it is composed of fiberglass and cured epoxy.  So far I've managed to save a few pounds and expect a few pounds more.  I can only save what I sand with the belt sander, the grinder has no dust collection.

I'll need to purchase some more hardener and start filling in some of the low spots.

September 18,

West system hardener arrived yesterday.  This morning I prepared the transom.  I feathered the edges of the glass around the transom and hung the mat and woven cloth using all my new found skills.

The light is not good but you can see that the glass is dry laid on the transom.  I've overlapped the sides about 1.5 - 2 inches (5 cm).  I plan to tape the overlap around the edge of the transom.  That way, it will lay down nicely when I epoxy the edge.  Remember that I rounded the transom edge so this should help things lay nicely. 

I feather edged the cured glass around the corner of the transom.  The transom glass is taped around the curved edge so it  makes a smooth transition.

I've completed the application of the epoxy on the transom.  The tape worked fairly well.  I had to unstick about 1/3 of the tape and tighten the glass up a bit.  I wish I would have put tabs on the tape in anticipation of this.  When your gloves are slick with epoxy, pulling tape up is difficult.  That is a good lesson learned.  Also, at the bottom of the image you can see a curved black line along the transom,  This is the actual cut line for the transom.  I darkened the line with a black marker hoping that the line would be seen as the glass became transparent.  As a precaution, I also marked a few points on the woven cloth in case the original line was obscured.  It wasn't. 

I'll need to wash this section down and a few places I filled along the hull that needed it.  Working a small area like this you can really make sure that everything is smooth and your seams will need minimal sanding in the end.  I look forward to cleaning this section up.