Building a Boat at the Ithaca Generator

For my winter project last year, I built a Standup Paddleboard at the Generator. I chose the 14 foot Kaholo kit from Chesapeake Light Craft. As boats go, this is one of the smallest and easiest to build kits, typically taking a new builder about 60 hours. I made a few modifications and chatted with other Generator members while I was working on it, so I probably spent more like 80 hours.

My son Ezra on the finished Paddleboard. The paddleboard is hollow, made of thin plywood glued, covered in fiberglass, and painted and varnished.

Below are photos and description of the construction.

Preliminaries


After unpacking the box and setting up a work table in the Generator, I scarfed the nearly 8′ plywood sections together needed to get the 14′ length of the hull.  Technically it’s a puzzle joint, not a scarf joint which is a lot easier to work with and really pretty as well.

I applied a layer of fiberglass and epoxy glue to the bottom of the deck to stiffen it.For the entire boat I used about 1 1/4 gallons of epoxy.

After this, the deck gets set aside until the hull is finished.


The first step of building the hull is to glue the sheer clamps to the rails. Sheer clamps are there to provide a gluing surface for the deck.

 I made clamps with 4″ PVC sewer pipe. They worked really well.

Stitching and Glueing

I stitched the sides to the bulkheads using thin copper wire.

 

Next I “stitched” the bottom on. It was a bit of fiddly work to get all the edges to join flush — After wiring them together, I spent a lot of time loosening, moving the panels, and retightening.

Later, I learned later that if I rounded over the mating surfaces a bit, they would stay where I put them better.

 

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Where the wood was being bent more tightly, the “stitches” had to be much closer together. I don’t show it, but once it’s all stitched together, I used a syringe (without a needle) to apply glue between the stitches.

This picture was taken after the glue had hardened. You can see some of the glue leaked out from the inside where it was applied. Right after this picture, I took out the stitches.

 

Filleting and Coating the Inside

The next step is to create a “fillet” between all the joints. These fillets create a larger gluing surface and ensure the joints will be waterproof. I mixed thickening agent (flour, very fine sawdust, or special lightweight “micro balloons”) and piped the mixture into the joints using the cut off corner of a ziplock bag. I used a rounded end of a tongue depressor to fare the surface.

I experimented with the mixture a bit and found a 50/50 mix of wood flour and microballoons worked well. Next time I’ll buy more microballoons. They were easier to work with and produced a smoother finished surface and sanded more easily.

 

Once it’s all filleted it was time to waterproof the inside. Water will get inside the boat and I didn’t want it to rot the wood or leach through to mar the finish on the outside.

I applied two coats to ensure waterproofness. Many people apply only one coat but, being my first boat, I was being careful.

 

Faring and Gluing the Deck

I’m getting ready to glue the deck on. I used a plane and a straight edge to get the tops of the sheer clamps perfectly flat and flush.

I don’t have a photo of applying the deck, but that was the next step. I prepared a thick mixture of epoxy and applied it to the top of the bulkheads and the shear clamps. I had several people help me drop the deck very precisely on the hull. I used tape and a few staples to hold the deck down while the glue hardened.

The deck is larger than the hull, so I used a router laminate bit to cut off the extra width of the deck.

 

I decided to create an eye catching tail block. I used strips of walnut and spruce to create this chevron pattern. I used carpenters glue to hold it all together. It’s not waterproof, but it’s easy to use and it will be encased in epoxy and fiberglass. All told it took a couple of hours. Time well spent in my eyes.

 

Here’s what it looks like with the deck and tail block applied.

 

It doesn’t look like much, but applying the round over to the deck and all the other joints took a lot of elbow grease.

A round-over bit in the router did only part of the job. I probably spent 3 or 4 hours with a plane, getting all the edges fair and rounded over. Most people use a power sander for this step and don’t create as much of a round over. Now I know why!

After creating the round overs, I spent 3 or 4 more hours finish sanding the whole boat to about a 120 grit. I did sand the tail block and other places that were very visible to a finer grit. I wanted to be careful though since too fine a grit decreases epoxy adhesion slightly.

After sanding late into the night several nights in a row, I could barely lift my arms so I took a few weeks off to recover.

 

Coating with Fiberglass

Here’s the bottom coated in one layer of fiberglass and epoxy. When the epoxy became rubbery, I used a knife to cut off the extra cloth.

After that I rolled on three more layers of epoxy to fill the weave in the cloth.

 

Here, I’m mocking up  the finished layout of the deck to decide where to put the decorative fabric. I had the fabric printed for me by spoonflower.com.

You can see the excellent manual on the left along with an article about how to build the boat from Wooden Boat Magazine. There are also lots of youtube videos about building this type of boat.

 

I’m applying some epoxy below where I’m going to apply the decorative fabric. Unlike fiberglass, the weave of the cloth is fine enough that it’s hard to force the epoxy through it so this makes it easier.

 

Here’s the fabric and covered by the fiberglass. I applied the fabric and fiberglass in one operation. I had to move quickly and mix several batches of epoxy to keep it from jelling before I could finish.

The layer on the deck overlaps the layer on the sides from the hull. This requires a LOT of sanding to get smooth.

 

Sanding, Sanding, and More Sanding!

I have a power sander, but I found this auto-body sanding block with 80 grit paper worked really well.

Between the finish sanding of the wood before applying the fiberglass and the more arduous sanding of the fiberglass, I spent 20-30 hours sanding in 3 or 4 hour chunks.

I delayed sanding the fiberglass for a couple of weeks. This meant I didn’t have as much of an issue of loading up the sandpaper with the partially hardened plastic. This was a mixed blessing though, since the plastic was harder and there was a little more dust. I used about half the sandpaper I would have if I hadn’t delayed.

 

By the time I was done, that roll of 80 grit sandpaper in the foreground was almost completely used up, along with several boxes of sanding disks for the power sander. I went up to 220 grit in preparation for the paint and varnish.

 

The sanding just goes on and on. I’m still working with 80 grit sand paper knocking down the high spots.

The lack of bright spots indicates that the bottom side of the hull is ready to go to a finer grit. Most of the effort was spent knocking down high spots with 80 grit. The finer grits went much more quickly.

 

Paint and Varnish

The weather was turning nice, and I really wanted to finish up so I don’t have many photos of varnishing the deck or painting the hull. In reality it was a tiny fraction of the total time. In this photo, I’ve masked for painting. I used “Fine Line” masking tape and backed it up with wider tape.

You can see a bubble in the fiberglass that I cut out and filled before painting. It was a fortunate spot since I could cover it with paint.

I rolled the paint on with a thin foam roller and tipped it with a cheap foam brush. It’s not as nice as a good spray finish, but it’s close and a lot easier.

 

Done!

Here’s another picture of Ezra on the completed paddleboard. I’m very happy with the board. It’s a good board that behaves well in waves and is fast enough that I’ve placed with it in races.

All in, it cost about half of a comparable fiberglass board and weighs about 40 pounds, somewhat less than twice as much.

It was a great first boat and I suspect I’ll be building more wooden boats in the future.