Planking progress stalled by need to encapsulate stem

As January keeps winding on, it seems as though I’ve had a million things to juggle or deal with that keep interfering with my boatbuilding progress.

I am making progress, however.

I’ve gotten the forward starboard plank screwed into position. It is not epoxied on yet, however. The simple reason is the fact that I have not yet encapsulated the stem, which is still bare plywood all the way around. Once the planking is on, it will be very difficult to reach certain parts of the stem in order to coat it with epoxy, (or “encapsulate” it), as protection against moisture. So, I need to encapsulate the stem before I permanently attach the planking.

The forward plank on the starboard side is screwed into position.

Detail view at the stem

In this detail view, you can see the how the added chine strips got blended into the shape of the forward bend in the chine.

Unfortunately, I don’t have on-hand the proper type of epoxy for encapsulation. What I have on-hand is System Three Silvertip Gel Magic. VERY viscous stuff that is great to work with to glue parts together. However, I need something much thinner for encapsulation. I liked the Gel Magic enough that I decided I’d try another System Three product, so I ordered the regular Silvertip epoxy. It should be here early this week.

In the meantime, I have fitted, glued and screwed the butt block into position on the port side of the boat. 

Fitting the butt joint on the port side. Without the butt block in place, the forward plank does not match the curvature of the aft plank.

By comparison, here is the butt joint on the starboard side. The butt block allows the forward planking to match the curvature of the aft planking.

The port side butt block, before being epoxied into place.

The butt block epoxied into position against the aft planking on the port side.

The next step will be to encapsulate the stem & a few other parts with 2 or 3 layers of the Silvertip epoxy. Then, I can permanently attach the starboard planking. After that, the rest of the port side planking.

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Preparing the stem for encapsulation

I should have encapsulated the stem a long time ago, before I ever attached it to the keel. Im not sure why I didnt. Nonetheless, I did not. I wont repeat that mistake on the Zip.

In any case, it needs to be done now before the planking goes on. In preparation for encapsulating the stem, I need to sand away several dried globs of epoxy that have been stuck on it since earlier stages in construction. The worst of these are directly behind the chines, where they are attached to the stem.

I worked on that a little earlier this morning. As this is the middle of the week, and free time is quite limited, Im expecting several more days of small, incremental progress in this task.

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The Utility part 3 Stem and floor battens

The Utility’s stem, as with the Squirt, Zip, and I assume several other Glen-L designs, is made of 2 laminations of 3/4” plywood. Fortunately, I had enough 3/4” marine-grade Douglas Fir plywood left over from Lusitania 13’s second transom to build both the transom and the stem for the Utility. 

The laminations are glued together with marine epoxy, (I used Poxy-Shield thickened with #2 silica), and bronze screws. The breasthook is basically made the same way, although the mating pieces are shaped differently: The top piece fits over the stem, and the bottom supporting piece fits around the stem. The breasthook is then epoxied onto the stem. I clearly marked all my centerlines, and tried to make the pieces fit as precisely as possible.

With the centerline on the keel clearly marked, I clamped the Utility’s stem/breasthook assembly into position. Next, using twine and a plumb bob, I worked carefully to make sure the whole assembly was aligned with the centerline of the keel. As a one-person job, this is rather tricky. If you have someone to help, it should be much easier.

With the assembly clamped into position, I drilled two 1/4” holes vertically through the forward part of the keel and aft section of the stem, countersinking the carriage bolts. After applying copious amounts of thickened epoxy, I bolted the stem to the keel with 5” long, 1/4” bronze carriage bolts. After tightening them, I filled the extra space from the countersunk carriage bolts with thickened epoxy.

Stem clamped and bolted onto forward end of keel.

Stem-to-keel joint after epoxy. Glue blocks added for reinforcement.

Having now learned my lesson from having to build up the keel thickness, I turned to the floor battens. As I mentioned before, the frame notches for these were cut to 1” deep. “1-inch” lumber off-the-shelf is typically only 3/4” thick. So, for the floor battens, I purchased an 8-foot, “5/4” mahogany board. (After they plane 1/4” off it at the lumber yard, you’re left with an actual 1-inch thick board.) The cuts for the floor battens were straight cuts, producing four 2” wide battens. Cutting the battens produces a lot, I mean a lot, of red sawdust. I decided to sweep up & collect most of it to use as wood flour to thicken epoxy later on. This turned out to work quite well.

The floor battens had to be fitted into the transom frame notches the same as the keel. The battens were fastened on with thickened epoxy and 2” bronze screws.

Transom knees attached to keel & transom. I put these on before adding the floor battens.

A note about bronze screws

Bronze screw heads are rather soft, and will strip out on you easily. This is particularly true when using a power drill as a screwdriver. Below is the method I used to remove a stripped screw during the fitting process for the floor battens:

Totally stripped-out bronze screw head.

I cut a slot in it with my Dremel.

Removal was then easy with a flat-head screwdriver.

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Zip stem construction

Todays blog post is about assembling the stem for my Glen-L Zip. The Zips stem, as with many Glen-L designs, is made from two identically shaped pieces of 3/4" marine-grade plywood, laminated together with marine epoxy and fastened with silicon bronze screws.

This is now the third stem Ive built; the other two being for a Squirt and a Utility. Learning from previous experience, I did a few things differently this time.

First, I spent much more time and care in shaping the pieces beforehand. I feel very comfortable this time around with the shape being correct.

Second, I used less epoxy. The other two times, I globbed a bunch of thickened epoxy on, just to make certain there was enough. In reality, that just creates more of a mess, because the majority of it squeezes out.

Third, I kept a putty knife ready to scrape away the epoxy that squeezed out from between the two layers of plywood. This makes for much less sanding afterwards.

Also, having learned a tip from a fellow boatbuilder, I used an awl to quickly align the pre-drilled holes before driving the screws back in. This proved to be a great time-saver, since it can be a little tricky to mate the holes back together with epoxy spread over the wood, (particularly while wearing latex gloves, goggles, and a respirator).

For the epoxy, I used Glen-L Poxy Shield, thickened slightly with #2 silica. Poxy-shield is mixed in a 5:1 ratio, using 5 parts resin to 1 part hardener. It can be hard to find very small mixing cups in order to measure small batches of epoxy, so Ive used my own method. I take a regular off-the-shelf mixing cup, and measure the distance between the pre-printed volume marks. So far, all the cups Ive used had a distance of 8mm between the 4oz and 8oz markings. So, I add marks every 2mm between them to show the 5oz, 6oz and 7oz lines. That way, I can pour in 5oz of resin, then add hardener until the mixture reaches the 6oz line. There are, no doubt, more accurate ways to go about this. However, this way is quick, simple, cheap, and effective.

Perhaps not the most scientific method, but it works.

After mixing and thickening the epoxy, I spread it out on the mating surfaces of each stem piece, making sure the whole area was covered. Then, I put the pieces together & aligned a couple of holes with the awl. I dipped the silicon bronze screws in a little epoxy, then drove them down into the holes. Then, I clamped the pieces together solidly, driving the screws in further as needed. Afterwards, I scraped away the epoxy that had squeezed out from between the layers before the epoxy became unworkable. Then I left it alone to let the epoxy cure overnight.

Everything ready to go: Stem parts, Poxy-Shield resin and hardener, #2 silica, mixing cups, mixing stick, chip brush, awl, screwdriver, extra screws (just in case), clamps, and putty knife.

Glued, screwed, clamped and scraped with the epoxy curing.

On a final note, I also worked on the Utility over the weekend... still fairing. It seems like a never-ending process, but its getting there.

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