Making Petrel Play: Glassing the Hull Interior - Episode 12


Hi, I'm Nick Schade of Guillemot Kayaks. Welcome to Episode 12 of my series on making the strip built Petrel Play kayak.

In the last episode I made the coaming of the kayak. In this episode I'll be scraping and sanding the interior of the hull before applying a layer of fiberglass, wetting it out with epoxy and then adding a light fill coat.

Back in episode 9 I glassed the exterior of the hull, and then Episode 10 I removed the hull from the forms so I could glass the deck. Now with the exteriors of both the hull and deck reinforced with fiberglass, I no longer need the forms. 

I remove the spacers and slide the forms off the strongback so I can put everything away until I want to build another.

Cleaning up the interior is where the scrapers really come into their own. The concave sections make heavy sanding with a random orbital sander awkward, but a contoured paint scraper can quickly and efficient get into small spaces to clean out glue and shave away any imperfections.

It is important to remember that we are fairing, or trying to make the surface more smooth. That means we are working on large areas, not small ones. So when I see a glue spot, I take a long pull, beyond, through and past, that spot. If I were to try scrubbing out just the spot, with short back and forth motions over the glue, I would end up chewing an undesired low area instead of creating a smooth fair surface.

The blade only cuts on the pulls stroke, so I put my effort into pulling. By lifting the blade on the return I protect the tool from getting dull doing something that doesn't help move progress forward.

I sharpen my scrapers before each use to make sure they make a smooth clean cut. A quick pull with light pressure should shave off a thin curl of wood. If you get a pile of small, dusty chips, you probably need to sharpen it more.

A sharp scraper quickly makes gratifyingly large pile of shaving, but it is not really removing a large amount of material. By selecting a scraper shape that matches the sectional shape, it is really just blending the flat faces of each strip into a smooth, continuous curve. 

A soft contour pad on a random orbital sander wants to conform to the existing surface and is inefficient shaping the facets formed by the strips into a hollow, rounded surface. By having a selection of different shape blades it is possible to very quickly prepare the interior so less time is needed with sanding.

When the shavings are no longer coming off the blade in clean curls, I'll touch of the edge with a diamond stone.

I had previously done a rough trim of the fiberglass with a utility knife. In preparation for adding an accent strip, I want to clean the top edge of the sheer line with a block plane, creating a smooth, flat, fair edge.

The accent strip is a 1/16 inch thick strip of maple glued directly to the top edge of the hull sheer. I could have installed this way back in Episode 3 when I started stripping by gluing it to the sheer strip, but I was thinking I might stain the hull. Adding the accent strip now would have avoided staining it to maximize the contrast. 

With a thin bead of glue on the top edge, I press the accent strip down and hold it with masking tape. 

I start with widely spaced bits of tape to get the alignment right. The tape can be pulled quite tight to assure good clamping pressure.

Once the strip is in place, I come back with more tape to fill in the gaps for a tight fit down the full length.

The same process on the other side.

With a tight fit, the carpenters glue is tacked up sufficiently in less than half an hour and all the tape can come off.

After scraping, the interior is in pretty good shape. At this point sanding will even out the texture and remove the tool marks. I add a soft foam contour pad to the sander to help it conform.

Using 60 grit paper on the 5 inch sander I can work on the wide, flattish bottom of the kayak, between the chines. The chines are too hard to sand across, and above the chines is too narrow for this sander. But I can sand farther through the softer chines near the bow.

An initial sanding will reveal any spots that would benefit from a bit more scraping.

Your hands are the best tool for detecting surface irregularities. If you feel any ledges or overhangs in the strips, a quick hit with a sharp scraper will easily remove it.

There are places the power sander is too big or imprecise to work effectively. Some coarse sandpaper wrapped around a block of foam does a very good job cleaning up in the chines, sides and ends.

With sanding complete, I thoroughly clean the interior in preparation for fiberglassing.

I don't want drips of epoxy running down the side of the hull that I'll have to remove later. Some tape along the outside edge should catch most of the mess.

The Petrel Play has a hard chine behind the cockpit. This is potential stress point in the finished boat. To distribute the load across the chine, I want to add a fillet and some reinforcement.

The fillet is epoxy thickened with wood flour, to make what I call Dookie Schmutz. Using a cake decorating bag, I dispense a worm of schmutz into the corner of the chine.

While I'm at it I add a fillet in the stems to ease the wrapping of the glass in the ends.

The fillet is shaped using scrap wood with a rounded end.

The next bit of chine reinforcement is a strip of bias-cut fiberglass crossing over the chine to cover the fillet.

I lay the strip directly on to the still wet dookie schmutz and then wet it out with epoxy.

Bias-cut strips are susceptible to pulls and distortion, so I first tack it down with gentle dabs before working it harder with the brush.

While working alone, the roll of fiberglass is easier to handle across the boat than lengthwise, and it is also more efficient with the cloth. I don't do this on the outside because I don't want to create stepped seams that need to be sanded out. On the inside, the overlaps are less noticeable and can be aligned with bulkheads.

I overlap each piece of cloth at least an inch to create a strong seam.

At this point, I'm just loosely draping the cloth, leaving enough overhang that there will be enough to fit down into the hull.

I want the overlaps to be directed towards the ends, so when I pull resin from the middle towards the stems, I won't snag the loose edge of the next overlapping piece.

Being careful not to snag the delicate cloth on any sharp bits along the sheer, I gently let the cloth drape down into the hull.

Eventually, I'll need to trim the ends to fit into the stems to prevent the glass from bunching up. For now, I just fold the end back a bit. 

Again, I work carefully to not snag the edges. Before pushing the cloth down, I'll lift the edge off the side so it doesn't scrape as it nestles in place.

Some little snags and distortions in the cloth aren't the end of the world, but I try to keep it neat.

With the cloth nestled into the hull, I trim off the excess glass at the edges. The weight of the cloth hanging over the edge can create bubbles along the sheer later on. Since I haven't finished the fit all the way to stems yet, I leave extra at the ends.

Proceeding directly to wetting out the cloth. I want to get the epoxy out of the large mass in the mixing tub as quickly as possible to slow down the cure giving me as much working time as possible.

From a long puddle poured down the middle of the boat, I quickly pull a bit of resin all the way up the sides. I'm not initially interested in making it look perfect. Instead I want to get the epoxy spread out and distributed.

Spread out epoxy cures more slowly than epoxy in a large mixing pot. Working quickly initially allows me more time to get a neat final finish.

After I've pulled that first puddle up the side, I start moving any remaining excess lengthwise. I want to move in a consistent front down the length of the boat.

I don't need to scrape all the excess away, but do I want to use the epoxy efficiently, so I try to spread it as far as I can without getting obsessive about it.

If you find yourself doing something and it doesn't make any difference, stop doing it.

About a minute twenty seconds after I poured that first puddle, it is spread out. Time to mix some more epoxy and move on.

With my sticky gloves I didn't get a camera on the trimming the glass in the stem area, but I cut a slit down the middle to the base of the stem and trimmed the glass so that it overlapped about an inch on either side.

After the first section I wet out has had a chance to soak in for a while, I come back and scrape off the excess resin.

When you first experience this it will drive you batty. Those bubbles are what I call bridging. As I press the squeegee into the cloth and pull from the keel to the sheer, it pulls the glass tight causing it to lift out of the chine.

Don't panic. It is going to happen again and its easy to fix.

The bridge appears because there is not enough fabric to fit in to the concave surface. You fix it by feeding a little more cloth.

I'm scraping the excess resin in to a slit paper grunge cup in the same way I did in episodes 10 and 11. When I was glassing the convex exterior surface it stretched the cloth tight against the exterior. With the concave interior you will get bridging. Learning to accept this and understand it will help your sanity.

If you realize that bridging will happen when you pull cloth out of a concave surface you will understand you don't need to struggle to fix it every time it happens. Do your work, then come back and deal with the bridging later.

You don't want to pour a huge puddle of epoxy down into the ends of the boat where it will be hard to dig out. Instead use a brush to apply resin to the surface and then use your squeegee to spread it around.

The stems can use a little reinforcing to cover any gaps made while trimming the cloth to fit into the ends. A strip of bias-cut cloth applied along the keel and up into the ends does the trick.

Again, bias cut cloth distorts easily, so a gentle touch as you coax it into place will keep it from getting away from you.

Carefully press the strip into place with the brush until it is centered and stuck down before completing the wet-out.

After the stem strips were installed, I let the epoxy set up for a couple hours before adding more resin for a thin fill coat.

I mixed up a small batch of epoxy and poured all into the bottom of the boat. I then spread it around the whole interior with a squeegee before scraping off the excess into a grunge cup.

In the next episode I'll be wrapping fiberglass around the coaming and glassing the interior of the deck.

I hope you found this video informative. If you have any questions about the operations shown in this episode please post them to the comments. 

Until the next episode, happy paddling and thanks for watching.

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