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Making Petrel Play: Scraping and Sanding - Episode 7


Transcript

Hello, I’m Nick Schade the owner, designer and builder at Guillemot Kayaks. We are up to episode 7 of my series on building the Petrel Play. I am making this kayak using the strip built method.

In the last episode we finished up fitting the strips on the deck. In this episode we will scrape, sand, and fair the wood to prepare the kayak for fiberglassing.

After the stripping is completed, the surface has facets or flat bits on the face of every strip. Since the cross section of the kayak is curved, there is a ridge at the joint between the strips. The primary goal of fairing is to eliminate this ridge, creating a smooth fair surface.

The first step is using a heavy duty paint scraper. The scraper removes glue drips, but it also shaves off the ridge. I scrape the whole boat, concentrating my efforts on the ridges.

The paint scraper is sharp. I actually hone it on my diamond stone to get it wicked sharp. It should produce nice curls of shaved wood. Woodworkers may call it a shave hook, but I bought a paint scraper, so that’s what I’m calling it.

I hold the handle low with a firm grip and pull quickly and smoothly along the grain. The other hand lightly holds the blade to damp out chatter.

The scraper quickly and efficiently removes glue and evens out any irregularities between the strips.

I want to keep the feature line sharp and distinct so I am careful to not wreck it. I scrape on one side than the other, being careful to keep the blade flat against the surface.

Fairing is the process of smoothing out the surface to eliminate sudden changes in curvature. As such you want to work on long sections at a time. On average the strips should be pretty fair before you do anything. Long strokes of the scraper will maintain the fair curve while slicing off high bits.

I don’t want to dig into a small spot just because I see a smear of glue or something. Any glue left behind by the scraping is probably there because it is in a low spot.

The only way to eliminate a low spot is to reduce the height of the high spots surrounding it. By blending this in from some distance around the spot, the surface will stay fair while becoming smooth.

All this work popped the little bits of glue holding the deck to the forms. A couple staples secure it back in place.

Scraping eliminates most of the high spots but still leaves a rough exterior. We want to level out the ridges and blend them into a smooth, rounded surface. This is done with sanding. We want to quickly knock down the high spots by continuously moving a sander with a moderately firm pad, over the strips.

I use coarse sandpaper, like 40 or 60 grit, moving systematically over the surface of the boat, leveling each area completely before moving on to the next. Using finer grit with a soft pad would tend to conform into to the unevenness, abrading into the low spots while trying to leveling off the higher spots.

Watching the staple holes as a reference, I work on a one-foot section at a time, moving the sander back and forth from centerline to sheer followed by up and down from one side of the section to the other.

Being systematic this way, I know that the whole surface is getting sanded equally. I don’t want to stall out in one spot, trying to fix some issue I see, only to end up with a dip in the surface. I’ll go over the whole thing once fairly quickly, but trying to level it out completely. If I find that this first pass leaves areas still in need of more, I can come back over the whole thing again.

Consistent, systematic sanding, one way than the other while overlapping the sander about 50% each move helps assure a uniform amount of material is removed. If I were to try to correct apparent issues, or only sanding where it looks like it needs it, I would run the risk of dishing out some regions while leaving lumps in others.

Again, I want to leave the feature lines crisp, sharp and distinct. With a firm pad I can work right up to the edge without the pad drooping or flopping over the line. The coarse grit cuts quickly and efficiently, without a lot of pressure required. You can see the unsanded shiny spots quickly blend away into a uniform, level and smooth surface.

When I’ve completed below the feature line I lift the tool and place it back down above the line.

This Festool Rotex sander has a gear driven motion that ensures a consistent orbital spin. Some sanders will change speed as you change pressure. With some you may want to shut the tool off whenever you lift the sander off the surface to keep it from spinning up uncontrollably. This high speed spin up can dig a horseshoe depression into your cedar as you touch down.

For now I’m just doing the quick first pass on the deck. I have more work to do before I’m done with it, so I’ll do the finish sanding after I’ve completed it.

Until then, I’ll get the hull ready for glassing. Like the deck that starts with pulling all the staples.

Also like the deck, on the hull, I use the staple holes as a reference guide as I work systematically down one side and up the other.

Some of you were wondering what the holes were for. Now you know. I’ll use them again when it comes time to varnish.

People complain about how much sanding there is with strip-built boats. It’s true you do need to sand, but with the right sandpaper and a good random orbital sander it doesn’t need to take forever. For reference, the scraping and this first sanding took about half an hour.

I’ve actually stopped sanding at 60 grit and the boat easily passed the 5-foot-back inspection. But we’ll take it a little farther today.

The random orbital does a very nice job, but it can leave some cross grain scratches, and if you aren’t careful, you may end up with some subtle hills and valleys that are impossible to see at this point but become visible when the boat has a been finished in glossy varnish. A wavy surface under high gloss creates wavy reflections, and by then its too late to fix.

The long board I am using here bridges over low spots while grinding down high spots. The result is an extremely fair and smooth surface, while at the same time scrubbing out any cross grain scratches.

Wetting down the cedar raises the grain and can help highlight glue spots I may have somehow missed. This is your first chance to see the full glory of the wood grain on the boat.

I used 80 grit sandpaper on the long board. Now, I go over the whole boat again with 80 grit using a finer finish sander, the goal is to complete eliminate all the 60 grit scratches. Like the prior sanding I am systematic, using the staple holes as a guide as I work my way around the kayak.

I change the disk early and often. Dull sandpaper results in a lower quality finish.

I then hand sand with 80 grit working along the grain to reduce cross grain scratches and maintain the fair surface.

The final sanding is with 120 grit using the random orbital with soft contour pad and then by hand.

The best way to inspect your work is to run you hand over it. Your fingers can feel irregularities smaller than a human hair. If it feels good it is good.

With the hull all sanded out it is ready to be fiberglassed. But before I do that I will fit the cockpit recess into the deck. That will be the next episode.

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See you next time, thanks for watching and happy paddling.

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