Building Phil Bolger's Cartopper
Page 1
Lane Kendall

Updated 3/10/2010
I am new to boat building. In March of 2008 I started my first project, a Puddle Duck Racer. The PDRacer is designed by Shorty Penn but based on Phil Bolger's "Brick" It was the simplest boat I could find to build. It is basically a straight sided plywood box and the design is open to almost any modification you can think of. All the materials can be purchased at any building supply or hardware store. There is no fiberglass or resin used, only AC grade exterior plywood and construction adhesive. The paint is Wal-Mart Porch and Floor paint. The sail is a white Poly-Tarp that I bought on eBay. The "Duckster" (hull number 234) turned out pretty well, even if I do say so myself. It actually performs quite well for a wooden box.

Click on Pictures to Enlarge
For my second project I wanted something a bit more complicated but still fairly simple to build. I started my research by reading a couple of boat building books. I found an excellent description of how to build Phil Bolger's Cartopper in a book named Instant Boat Building by Dynamite Payson.

Payson has written several books describing how to build Phil Bolger designs. He stresses simplicity and low cost materials. I chose the design for several reasons. Cartopper is  a good looking boat with very traditional lines. It has a reputation for being a fair sailor although it would probably excel as a rowboat. In North Carolina a sailboat under 15 feet in length does not have to be registered. Cartopper, if built correctly,  is light enough to be carried on a car's luggage rack. The most important reason is the excellent blow by blow description in Payson's book. For my first "real" boat I needed all the help I could get.
My first challenge was to create a place to work. My basement is a suitable size but much too cluttered. I hauled 5 pickup truck loads of accumulated junk to the dump. After cleaning up I built a new workbench and a tool caddy. Of course, since you can never have too many tools, I picked up a few had tools and replaced my "too small" table saw with a used Delta that I found on Craig's List. My basement is not heated but it is mostly underground so it maintains a fairly steady temperature of about 60 degrees unless it is really cold outside. 60 degrees is just a bit cool even if you are moving around. I solved the problem with a new convection propane heater. The good news is, it works great. It can raise the temperature of my work area by 10 degrees in about an hour. The bad news is, it burns propane like crazy. 
Working in a small space enclosed within a dwelling can cause problems. When I was building the PDRacer I got in big trouble when I cranked up the sander and created massive clouds of dust in the basement. Of course as soon as the forced air heating system started I was sharing my dust with my wife who did not appreciate it at all. After that episode I had to take the boat outside each time a major sanding was required. Painting was also done outside as well as several other tasks. Moving an eight foot boat (the Puddle Duck Racer) outside was hard enough and I figured Cartopper's nearly 12 foot length would be even more difficult to manage. My friend Charles had given me 4 pneumatic wheels and tires that I used to build a "boat trolley". The two wheel assemblies have axles and "fifth wheels". The handle can be attached to either end so it can be steered going outside and coming back inside. The best feature is that it can be reconfigured to work for boats of different lengths. I used drywall screws exclusively because they hold better and can be removed without ruining the lumber.
I have read volumes about the different kinds of plywood and the virtues of using marine plywood as opposed to regular lumber yard grade. I have read about boil / freeze tests and how you should never spend time on a project using inferior materials. Surprisingly, I have read books and study plans from at least three popular designer / builders (including Payson) who do not agree with this assessment. In his book, Payson says that he has never lost a boat due to using lesser quality plywood. I chose a lumber yard 1/4" underlayment made with exterior glue. If this project goes well I may consider a better grade of ply for the next project. If it does not there will be a much less expensive bonfire in my driveway. I am using southern yellow pine for the dimensional lumber because I can get it locally and it is less expensive than something more exotic. I followed the same logic when choosing epoxy for the project. I chose MarinEpoxy brand simply because it was the least expensive I could find. This project is more of an excercise in boatbuilding and less in building a boat. 
The underlayment looks really good except for the nailing marks that are printed on one side. I think it will work as well as my meager skills will allow. In his book Payson says "If you can saw a line, you can build these boats". I almost gave up when I read his statement because I have never been any good at cutting wood with a saw. I have developed a work around that seems to work for me. When I cut the long top planks for the boat I lofted the first one as directed by Payson. I first tried a circular saw with a fine blade. I has set the blade very shallow so it would make the gradual curves but it did not go well. There was so much smoke my wife thought the house was on fire. I finished with a saber saw. It was slow but not as smoky. I cut up to the pencil line on the first side then flipped it over to mark and cut a mirror image for the other side. I used  drywall screws to fasten them together. I took them outside and used a 6 inch 40 grit sanding disk on my electric drill to sand down to the original line with the two sides fastened together. I can't guarantee that they are lofted or cut properly but they are practically identical.
The next step was to make the frames, transom and stem. Payson says you can double the thickness of the frames if you want. Since the underlayment is not quite quarter inch it seemed like a good idea. I didn't double the entire frame, only the lower parts that will not be removed later. My sawing skills were again put to the test again partially cutting the frames while leaving tabs that will be cut out later. My saber saw was really making a mess of the veneer on the top of the plywood. I read on the Internet that if you put clear packing tape on the wood before you cut there would be less splintering. It actually worked quite well. I was concerned about building the stem but it turned out better than expected. I built it as close to Bolger's spec as I could including the angle that does change slightly from the top to bottom. One of the new tools I bought was an electric hand planer. It worked great removing lots of wood quickly.

In his book, Payson describes placing frames B and C on legs for hull assembly. I made shorter legs that sit on the rails of the trolley. The boat's "legs" are not actually attached to the trolley so they can be easily moved and adjusted as the side and bottom panels are fastened.
To this point the building process, was a simple matter of following the directions and making individual parts. Assembling the hull was a different story. I did not follow Payson's instructions to the letter. When I built the PDRacer, I made extensive use of drywall screws. When placing the hull panels I used small finish nails driven directly into the frames. I could do this because the frames are nearly 1/2" thick as opposed the the 1/4" called for in the plans. I placed the side and bottom panels first and when I got them placed where they needed to be I used drywall screws to fasten the parts to the temporary cleats. The advantage to drywall screws is they can be removed and replaced multiple times without stripping out. I cut the edges of the frames to the angle indicated by the plans but I did not bevel the cleats. It worked well because I put the cleats on the long side of the bevel so they did not interfere with how the panels lay on the frames. When I fastened the panels with drywall screws I did not screw them down all the way because doing so actually changes the shape of the boat. Drywall screws do not need to be tight in order to hold the panels securely in place.

Payson says that fastening the bilge panels is the most difficult part of building the boat. I found this to be true. The thing to keep in mind is that the bilge panel must bend in two directions at once where it bears on frame A. I fit the bilge panels on the hull and fastened them temporarily with finish nails. There was some overlap in several areas. This was expected. I climbed under the boat and marked the inside of the panels then removed them and eliminated the overlap with a saber saw. I got a good fit but the seams looked more like gashes. I assembled the entire hull without glue. I used screws and steel wire to align the panels. I had some fairly large gaps between panels at places.

The bilge and top panels had a serious gap between frame A and the stem. I used several short pieces of plywood inside the hull with screws to pull them together. I guess this could be done with wire but with the screws I could fine tune the alignment with a screwdriver.

When the hull was completely assembled I removed the screws from the stem and transom and began the gluing process. I decided early on to use epoxy throughout the building process. I unscrewed the transom and the stem and painted all the surfaces to be glued with unthickened epoxy. Then I mixed another batch using silica thickener. I was able to place the transom and stem back in their original positions by aligning the original screw holes with a piece of stiff wire.

I went under the boat and covered all the seams with 1" masking to keep the epoxy from dropping through the gaps. Using unthickened epoxy I painted the seams to seal the bare wood to receive the thickened epoxy. It was a simple matter to use a putty knife to fill the seams.
Payson says that 1/4" gap between panels is acceptable but some of mine were a bit bigger. I learned that you should not try to close a gap while "stitching" the panels together because this can alter the shape of the boat. The best bet is to leave the gaps and let the epoxy span them. I probably used too much epoxy trying to correct the gaps. I don't know whether it will make much difference after the outside of the hull is covered with fiberglass.

After the epoxy cured, I removed the wires without a lot of grief. I had to use a propane torch on a few of them but not many. I learned that you want to use the smallest wire possible because the less surface area the easier they are to remove. Also steel wire seems to work well and is probably stronger than copper or some softer metal.
With the epoxy cured and the wires removed it was time to sand the excess thickened epoxy and prepare for taping the long hull seams. The trolley came in handy for easily moving the boat outdoors for sanding. I put the tongue on the trolley at the bow of the boat, removed the 5th wheel pin and pulled the boat outside for sanding. I left the dust and shavings outside instead of in the house. No matter how many lights you have in your shop, outdoor lighting is always better. When the sanding was done, I put attached the tongue to the trolley at the stern of the boat so I didn't have to back the trolley on the return trip.
After the first sanding I went over the seams again to build them up and improve the shape where gaps were present. I used a lot of thickened epoxy on the front edge of the stem. I was surprised that it came out very well. I used a 4" piece of fiberglass to cover the stem. I'm not sure what weight it is but I am sure it was much heavier than recommended. It turned out very well. 
When applying the fiberglass tape to the long seams, I followed Payson's instructions by first painting the area with epoxy to saturate the wood before the glass was applied. Then I used a three inch roller to apply the epoxy and it really worked quite well. I am sure I would need another coat of epoxy to completely fill the weave of the cloth but I did not get a lot of drips and runs. 
After the taped seams cured, I went under the boat and removed the "feet" from the frames. I was surprised at how light weight the hull is. I turned the boat over and sat it on a couple of light cross members. I think the height will be about right for working on the boat's interior.