Kayak Building Part 7 – Power-Sanding the Hull

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This is part 7 of a multipart blog . . . Read Part One here,  Part Two herePart Three herePart Four herePart Five herePart Six here.

Now that I finally finished hand scraping and shaving all of the epoxy drips from the panels, smoothing out the extra epoxy on the bow and stern ends and flattening out the seams, I was ready to sand with a power sander.  Before getting started, I checked in with Andrew Bondi – Woodcraft’s power tool expert. I wanted to know which sander to use and how to use it.

Andrew suggested I use the Festool Rotex RO90 along with the Festool Dust Extractor. We met in the shop, and Andrew took me through the features of the sander and how to change out the different sanding heads. Here’s the video of the Festool Rotex RO90 instruction.

That lesson actually took place in May.  I thought I’d be using the power sander a long time ago. That night in May when I showed up at the shop with the Festool sander and dust collector, Dan laughed and said it would be awhile until we would need that. In fact, it was about 16 hours of work before I needed it. So finally, a month later, it was time to break out the power tools and go to town!


Day 29 6/13/12 3.75 hours

Dan and I met at the lockmaster’s house and carried the three sawhorses outside onto the sidewalk. Then we carried out the boat and set it on the horses. I was skeptical because I really didn’t think we’d fit the 17 ‘ long boat through the door frames and out the front door, but we made it without a scratch!  Next we were able to plug the sander right into the dust collector and set it to the tool activated mode. That was super convenient – the dust extractor would turn on and off with the switch on the sander.

I showed Dan the new Rotex RO90 and the two settings – one that is more aggressive than the other. I also showed him the dial so that you can control the speed of the sander. He took the tool and showed me how to sand the panels. He suggested feathering the sander a bit by putting a bit of an angle on it and sanding with the top part of the sanding disc. We used 220-grit sandpaper.

When he started to sand the seams, I noticed many small holes in the epoxy. With all of that epoxy I had in the seams, I couldn’t believe there were any holes. Evidently it’s common and happens to most people. Dan said I would have to fill the holes with clear epoxy when I was done sanding and before fiberglassing. That was THE LAST thing I wanted to do, add more epoxy once I finally sanded it all off. He said if I didn’t fill them, then it would cause air pockets in the fiberglass. I didn’t need to fill the holes from the wiring, because they went clear through the panel. I just had to touch up the holes in the seams and add more wood filled epoxy to smooth out the bow and stern ends.

In addition to the power sander and dust collector, I was also equipped with SAS Hearing Protectors and a dust mask. The sanding was loud, but not as loud as I thought. I was ready to ditch the hearing protectors, but Dan suggested it was much easier to stay focused while wearing the protectors, and that it could do more damage than you realize. So – hearing protectors it was.

Dan went inside to help Gary with his boat, and I started sanding in the middle of the boat and moved to the end. Dan and Gary worked an hour and both left. I asked Dan if he would come back to help put the boat back in. He said it was light, and I could handle it.

When sanding, I ended up using the more aggressive setting with the 220-grit paper. I also dialed up the speed. At that speed, it was harder for me to control the tool, so I focused on keeping solid footing and held the sander in front of me. Earlier Dan was concerned that the design of the sander had a different handle than most sanders and that I would tire easily. I liked the design of the tool and didn’t tire out too fast. I also went through a lot of sandpaper – now I know why the paper comes in a pack of 100 discs!

I completed sanding the entire boat before it got dark. Then I easily carried the boat back inside. Dan was right, it was very light and easy to handle. I just set it up on the layout table, so I didn’t have to negotiate the door frames.

The boat looked beautiful (for now) ! I still had to return to touch up the seams.


Day 30  6/15/12  1 hour

Although I hated to add more epoxy to the hull, I had to touch up the holes.  I mixed the epoxy and filled the syringe with the smaller hole. (Earlier we cut the tip off one of the syringes for the thicker epoxy-wood flour mixture.)  I was applying the epoxy very slowly and really trying to control the syringe.  Occasionally the tip would thicken up, and a larger amount would come out.  Drats – more epoxy to remove later!

Also, when the epoxy is squeezed through the narrow tip, it sets up faster.  Because I was being so cautious, it started to set up in the syringe, which complicated the process.  I wrapped up quickly at that point and had to spend some time getting the hardened epoxy out of the syringe.  Fortunately I was able to remove it and save the syringe.

Day 31   6/16/12  1 hour

I showed up early on a Saturday morning to scrape the seams before the Woodcraft company picnic.  I was in charge of the volleyball tournament, so I had to arrive on time!  In any case, this time it was very easy to remove the excess epoxy.  Besides the fact that there was just a small amount, the epoxy was still “green” and wasn’t as hard as it would get.  Also – I had my sharp cabinet scrapers.  Unrealistically (again) I thought I could complete in an hour.  Not the case.  I had to run out at 10 and still had a few spots left.


Day 32   6/17/12  1 hour

I ran back to the lockmaster’s house for a bit of work before the Father’s Day picnic we were having nearby.  I completed scraping and sanding the remaining seams and then vacuumed the dust off the boat with a regular canister sweeper.  Now I was ready for the first layer of epoxy.  Fortunately Dan was also at the house and instructed me to mix up the epoxy using three parts of the hardener and resin.  When mixing more than one batch, it’s important to keep alternating as you fill the mixing container.

I used a 3″ paint roller with a special foam cover.  I purchased at least 10 foam covers at West Marine – they have a very thin (1/8″) layer of yellow foam.   We cut the foam covers in half to use with the 3″ roller.  This type of roller does not come with the kit, but is essential in the process. I also used a smaller paint tray for easier handling.  After rolling the epoxy, Dan showed me how to use a 3″ disposable foam brush to lightly smooth out any air bubbles caused by the roller.  The boat looked beautiful once that initial layer of epoxy was applied!  The deep color of the wood popped right out!

Next step . . . Fiberglassng the Hull – FINALLY!  Stay Tuned!


Read Part 8 here!  Fiberglassing the Hull

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