Finishing a Boat – Prep (Part 1 of 2)

I had a conversation with a friend yesterday.  It went something like this;

Friend:  How is the kayak coming?

Me:  Great.  I am just finishing it.

Friend:  Oh yeah?  When do you think it will be done?

Me:  I dunno.  Maybe a month.

Friend:  I thought you said that you were just finishing it?

For those of you out there that have built a boat before, you know where I am going with this.  Finishing a boat does not mean that you are close to complete.  Finishing the boat is really just beginning the final stage.  Depending on the boat and how nice you want it to look, the finishing steps can take you longer than the steps where you actually put the boat together.  I wanted to go through the process I use to “finish” my boats.

Once the hull is all assembled and put together as much as it can be, it is time to cover the wood or epoxy/fiberglass with a paint or varnish.  Fiberglass alone is plenty durable all by itself, but it has no resistance to UV rays.  Therefore, the layer of epoxy must be covered with paint or varnish.  I am typically a bit more meticulous prepping a surface for varnish than one for paint, but not by much.  Maybe a couple less wet sanding sessions with the 400-grit paper, but that’s it.  Often, paint can reveal just as many flaws as varnish, so I try to prep each surface just about the same.

  1. Once the hull is all glued up and solid and I have let it sit for a couple of days to make sure everything has cured thoroughly, I will start with a quick cleaning.  I vaccuum all of the dust with my trusty Rigid Shopvac with a brush head.  I then give it a wash down with denatured alcohol.  Keep in mind if you have used a blushing epoxy such as West Systems, you should wash and scrub the epoxy with a Scotchbrite pad after the vaccuum.
  2. Then, provided it is not a complete disaster that needs a facelift, I use my DeWalt Random Orbital Sander with 120-grit sandpaper.  This s a very toxic dust, so hook up your tool to a vacuum and where a mask.  I will sand patiently until the surface is flat with no shiny spots.  At this point, you may sand through the epoxy in some places and expose some of the fiberglass fiber.  You have options.
    1. You can ignore it and continue, but know that those fibers will probably show through any finish you apply.
    2. If you are painting, you can apply a high-build primer such as Interlux Brightside Pre-Kote and sand it smooth
    3. Otherwise, if you are finishing bright and trying to make this boat the most beautiful boat at the show, apply another coat of epoxy and start the sanding process over again
  3. I will then vacuum and wash in alcohol again and go through the same process with 220 grit sandpaper on the sander.
  4. Again with the vacuuming and washing, I will put away the power sander.  It is time for some manual labor.  I use the 3M line of Stikit sanding blocks to wet sand the boat with 400 grit paper.  On the spots that are particularly curvy or tight, I will just use some paper in my hand paying close attention that I do not put too much pressure on one finger or the other.
  5. Wet sanding makes a bit of a mess, so I will wipe all of the wet dust of the boat with a cloth and then wash it clean with another denatured alcohol rub down.
  6. We are getting close now and I want to be sure everything is as close to perfect as I am comfortable getting.  I will give the whole boat a once over eyeballing all of the corners, curves, flats, nooks, and crannies.  What I usually find at this point are swirls from the random orbital sander and scratches from the hand sanding.  For these, I will use my Bahco carbide scraper.  It is one of my favorite tools and favorite steps in the process, but be careful.  Carbide is very hard and takes down layers of epoxy fairly quickly.  Use light to moderate pressure and make sure the blade stays flat.
  7. Finally, another wet sand with 400-grit to smooth out any marks left by the scraper.  Another cleaning and denatured alcohol rub and you are ready to paint.
  8. Painting/varnishing is the easy part when compared to the prep work, but you still need to prep one more thing…the shop.  The day before you plan on putting brush to boat. Vacuum the entire area to remove as much dust as you can.  Be meticulous.  One little kicked up pile of wood dust can wreak havoc on your finish.  That is enough for the first couple of coats, but for the final coat, I like to mop the floor with a wet mop to just be sure I won’t be kicking up any dust particles.
  9. Continued in Finishing a Boat Part 2

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