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Study Guide

For Pilothouse And Trawlers Construction


These plans are divided into six parts.

Chapter 1 General Information
Chapter 2 Boat Finish
Chapter 3 Cabin/House From Scratch
Chapter 4 Costs
Chapter 5 Photo Gallery
Chapter 6 Summary

General Information

This set of study plans will explain pilothouse and trawler modifications that can be made to most small cabin sailboats. Small sailboats up to 24 feet make great projects for home construction. The main reason we use sailboats to do this type of modification is because they have keels and ballast. Of course, we have to have both in a pilothouse modification to sail. A trawler doesnít, but the trawler will be a better trawler with both features. The reason we build a house on a sailboat is because the shelter will extend our time on the water and as we age, we need to avoid the harmful affects of the sun. They also look pretty cool if done well.

One thing we found out after building several different models is little boats can get busy fast. Keep it simple might be a good design rule. All boats have an outside and an inside and both need to be functional. Both the pilothouse and trawler require good side decks to go forward and work ground tackle and dock the boat. Our normal procedure is to build the outside first and make it look good and then do the inside. Of course, you will have some idea of the inside features and where it all goes as you build the boat. These study plans will help you with your wish list of ideas.

Just about any medium to smaller cabin sailboat will work. I did a computer drawing of a Hermann Cat that I owned and decided it wouldn't do. It was too ugly. The boatís original cabin had too many large vertical surfaces to make an attached house look good to my eye. A computer graphic of your modified boat will let you know what it might look like before you start building. I use cut and paste and the Windowís Paint Program to look at my modifications on a computer. I also make changes on the fly if I think Iím going to like the modification.

We currently build two different houses. Both use some of the same components. The two front windows and house panels are common to both models. The house panels for a larger boat are longer and wider at the aft end and the side windows are also longer. Both designs use the sailboatís bridge deck as an adjustment point to make a production house fit several different boats. Most sailboats have a bridge decks between the cockpit and the cabin. This feature allows the same house to fit a Com-Pac 23 and a Catalina 22. Both boats have similar deck layouts and size. The forward part of the house normally starts just behind the mast step and ends on the bridge deck. The same procedure is used for the small boats. The small house can be used on the Com-Pac 16, an OíDay Mariner and most other small cabin sailboats.

Start Construction

We will look at the way we build boats at The Sailboat Company and then will talk about alternatives to those procedures in Chapter Three.

The roofs of the trawlers/pilothouse boats are called top/tops around here. We lay them up in molds as a solid glass and resin laminate. We make the laminate light enough to be handled by individuals during the building process and not heavy enough to be stood on by heavy individuals when installed. We want strong and light up high. We donít bother using gel-coat as the finish surface during lay-up because the houseís surfaces need to be finished and the top/top can be done at the same time. This finish is going to match the boatís finish in most cases. We cut our vertical panels using patterns as a guide and consider how they will be finished. We use Ĺ inch COOSA for our vertical surfaces. COOSA panels are made from foam and fiberglass and they have a semi-rough surface. Making the panels smooth will be necessary for a good-looking finish. We have laid a thin surfboard fiberglass cloth over the panels to make the surface smooth. We have also sprayed a heavy coat of gel-coat on the panels as filler. Both work and maybe gel-coat is the easiest to do.

At this point, we turn the top/top upside down and put the panelís tops down inside the top/top. You are looking for a smooth fit on the curved surfaces. The aft panel needs to fit the top/topís curved edge across the rear and the front panels need to do the same thing across the front. The gap between the panels and the top/top along the outer side edges and the back should be about Ĺ inch. We use screws to hold the panel in place. They can be removed after glassing inside. The fit of the panels when they are put together is not critical. The one in the center between the two front windows is important. It is difficult to remove an error at that point after they are glassed together. When you are satisfied with the fit, use resin and fiberglass tape to glass the inside joints. The picture on the left shows a small upside down house being put together. The outside joints will be glassed and finished after the house is connected to the boat. We normally put paper down inside the top/top to avoid resin drips during the taping process. The vertical side panels will be rigid at this point and the whole house excluding the top/top can be put on top of the boat. This is the time to do adjustments to the bottom of the panels for a good fit. Most cabin sailboats have flat horizontal cabin tops. This matches our base line panel line under the windows. The shape of the house and headroom under the top/top is important. This is the time to add or remove panel material to give your house a good-looking shape. A higher roof at the cockpit entrance will make getting in and out better. If you are happy with the looks and the fit, use the inside of the panels to mark a cut line on the top of the boatís cabin with a black magic marker.

You designed the panelís bottom edge to fit the top of the sailboat. The panels started at a point behind mast and they continued into the cockpit. The side panels need to fit the boatís cabin where it joints the cockpit. They also need to fit and sit on top of the bridge deck. When all this looks good, use a magic marker again to continue the cut line. We normally remove the bridge deck thatís inside the house. If you plan on using the bridge deck as a seat, you will want to make a different cut. A good jigsaw will cut the cabin top. After you do your cut to the black line, you can remove the cutout cabin top. Be careful because they can be heavy. You will be attaching the vertical panels to the cabin top with epoxy. If Iím not in a hurry, I like to sit the house on the boat and think about my furniture placement and the entrance at this time. Bigger is better when it comes to an entrance.

We use West System Epoxy in a tube to attach the vertical sizes. Sand the boatís matching surfaces, squeeze on the epoxy and clean up the excess. It will cure by the next day. The picture on the left shows cutout tops for small and large boats. The picture of the large house on the right shows the panels with the windows cutout. Make the initial connection using epoxy with two more planned later. Now itís time to finish the outer panel vertical joints. We shape the outer edges of the panels with a sander. Work at making the edges consistent and straight from top to bottom. Fill any gaps with filler and then cover the whole joint with a fine fiberglass tape. The panels need to be finished and we are going to do this with gel-coat. We could have done the gel-coat filler process before we put them together. Spraying gel-coat with a special gun puts lots of gel-coat on the surface. It will make a good finished surface after it has been sanded smooth. The joint between the house and the boat is made with filler. Apply the filler to the joint and then shape it with a tool. A finger or a tongue depressor works well. This joint makes the modification look like it is one piece and very professional. Flaws are easy to see under a few coats of paint. Many coats of paint are required for a modification to look perfect. If you are going finish the house in gel-coat, doing the final finish will be less time consuming. Painted hulls that are flat and undamaged are easy to paint. Flaws donít show in that type of painted surface. Joined or repaired surfaces will show flaws under painted surfaces because the paint is transparent in some light conditions. Dull gel-coat that matches the boatís dull gel-coat hides flaws.

A second connection method between the house and the boat is right angled aluminum/teak inside the boat I use epoxy again to secure an "L" piece under each big window. You don't normally need a third method, but screws and brackets could be used.

A window company in CA builds windows for our boats. We use the windows as a pattern for the cutout in the panels. The windows are sealed with caulking and I like the extra dark option for the Plexiglas. The top/top is secured to the house panels using handles. A stringer is located front to back and glassed into place. The handles are bolted through the top/top and the stringer for a good strong connection. At this point, we have a finished boat on the outside. We will still have to finish the inside and make a canvas cover for the entrance. When you get your canvas cover made and installed, you will have a dry boat and your boat can go outside. A great way to check for leaks is after a day of rain.

Outside Construction Review

We started with an existing laminate called the top/top. We cut our house side panels from our existing patterns. We started building the house upside down by positing the panels inside the top/top. When the panels have been glassed together, the house panels become rigid and can be lifted and positioned on the boat. We cut a hole in the boat using the rigid panels as a pattern. We connect the panels to the boat using epoxy. We cut the holes for the windows; install the windows, the top/top and the canvas. The finish work is next and that takes a long time. If you do a good job on the finish details, the boat will look like it was made by a professional.

Inside Construction Details

General design features for the inside include standing headroom, inside steering, bunks for sleeping and a head. Standing headroom will depend on the boatís size. A 16-foot boat will look odd with standing headroom in the house. The basic rule for a good-looking boat is the six to one rule. The rule is six times long to one time high. Most people including me break this rule when we build a trawler or pilothouse. Sometimes you can do this well and the boat will still look good. Standing headroom on a 23-foot boat is easy to do and the boat can have great lines. Inside steering should be located back towards the rear of the house for several reasons. You are going get a better ride in this position and the helm located close to the entrance will aid sail control in the pilothouse model. The helm seat on one side and the first mateís on the other will help you control sails on a pilothouse. Remember, we all get skin cancer from the sun. Sailing from an inside position with lots of fresh air and no sun may be a good solution for skin cancer. A boat with ballast will handle the imbalance problem caused by the helmsperson being on one side. A boat without ballast should keep everything in the middle of the boat.

Larger boats in the 23-foot size range will use the forward cabin for sleeping. If you are building a trawler, you donít need a compression post and you can remove it for more room. If the compression post is a bulkhead, the bulkhead can be removed and the boat gets bigger on the inside. Most boats will use a portable head. It needs to go under something and be pulled out for use when needed. You need to think about this as you build. Most sleeping bunks use cushions and the helm seats are marine pedestal seats or they can be office seats purchased from your local office supply store. The bunks can also use an indoor/outdoor rug material instead of cushions. You get more room in the bunk area if you use a rug material. New cushions can be expensive and sleeping in a sleeping bag or on a piece of foam should fit most people's needs. The rug makes the boat look good when the sleeping bags are stored. The reason we might use office furniture for helm seats is because they are cheap to buy, they go up and down, turn 360 degrees and they will lean back. In a marine seat, all of these features cost money.

The helmís control pedestal is built using teak plywood. You can get fancy with this piece of furniture. It will hold the wheel, engine controls and any other instruments the boat may need. It has to be comfortable to use while you are at the helm. Anyone that travels will put lots of hours behind the wheel. The helm and the control pedestal need to be comfortable. The pedestal seats have to be small enough to allow a passageway between two seats to go forward. A moveable table should be positioned in front of the port side pedestal seat on larger boats. The table is used for meals and as a chart table. Most cooking is done in the cockpit on a portable gas stove and dishes are washed at the same location in a plastic pan. You can have two or three people in the cockpit and two people in the cabin and they are all at the same level for talking and eating meals. Removing the canvas curtain between the cabin and the cockpit makes these boats great for a social outing.

Most of the inside construction details can be obtained from our pictures. In all of our models, we build the main cabin seat and control pedestals on the boatís original bunk platform. That puts people seated in the pedestal seats at the correct level to see out the windows. We use as much of the original inside furniture as possible. If you have a boat that has an old and ugly inside, Formica will cover most surfaces and making the inside white will brighten up the boat.

Boat Finish

You have a boat and you have a house and the whole thing looks good from a distance. If it's going to be worth more than what you put into the whole thing, the outside finish has to look good. Let say the boat is a 1980s something that has white gel-coat for a finish. Not many boats have a white finish. Most have an off white finish and that makes a big difference. The idea is that top/top needs to match the rest of the boat. Most 1980 boats have a dull finish and they look their age when buffed and waxed. That's not that bad because gel-coat when applied to boats outside of a mold will also be dull. Some people take forever buffing and waxing a new gel-coat repair to match a new boat's finish. It's not easy. Gel-coat can be purchased in quarts and gallons. You need to match your gel-coat by adding a little of this and then a little of that. Once you get the right color match, it can be applied many different ways. We like to spray with what we call a "Blunderbuss". After getting the gel-coat on the house, you are going to fine sand the gel-coat finish and then buff and polish. The gel-coat needs to be smooth. You don't have worry about a non-skid surface on your house unless you want to do the extra work. I would say that an acceptable finish is one that looks like other boats of the same age.

You might consider a painted finish if you are doing more than just the house. Paint will shine more than gel-coat and may do better in the sun over a long period of time. Paint is a more difficult method of applying a finish. The Internet is full of people that have painted boats and were successful. I just painted one and it looks pretty good. The finish work gets a lot larger if you need to finish the whole boat. On some boats, I do a mix and match method. There are some paints and gel-coats that are the same color. Sometimes a top/top will look better painted than gel-coated, while the vertical panels and the joint between the house and the boat look better with gel-coat.

Com-Pac and other builders still make inside components for most of their boats and they can help you finish your inside. Com-Pac sells a material that covers inside of the top\top around the windows. In tan in color, doesn't mildew and it's easy to install. Most other building materials can be found at Home Depot and Lowes.

I think the house needs to look like it is part of the boat. We did try something last time that we may use again. The joint between the house and the boat takes time to finish. We avoided this job on one boat by cutting strips of COOSA and routing the outer upper edge half round. We screwed these strips to the boat and to the house. We filled a few voids and we were finished. As long as your color match is good between the house and the boat, the strips will disappear and they are easier to do.

Cabin/House From Scratch

You can build your first boat like we built our first boat. It takes a 4X8 sheet of bathroom tile from Lowes and some time on your knees. You lay the tile face up on a flat floor. We waxed ours with a good paste wax. We purchased a can of resin and enough glass roving to make a large size even layer of cured glass cloth. At about 1/8 inch, the cloth is still flexible when it pulled off the bathroom tile. We then made a frame that would hold the glass cloth in the shape that we were looking for. We were on our way to making our first top/top. With the flexible cloth laid in the frame, we added more cloth and resin until the laminate became rigid. It had a smooth surface on the outside, was rigid and keep it shape from side to side and front to back.

You can see where we are going with this procedure. We started at the top and worked our way down. We added some 1/2-inch foam blocks around the edges so we could glass an edge molding. We knew that the area above the windows would be flat and we made our frame produce that shape. It wasn't easy, but we only did this job one time. We are still using the same shape today. There is some guessing when you do a "first" anytime and this procedure is no exception. When the top/top is completed, cutting plywood panels is the next step. We used glassed plywood for our first boat with good results. Start with 1/4 inch Luan and the rest of the panel thickness will be glass and resin.

Photo Gallery


Building a house on a sailboat is easy. After some experience, building a good-looking functional boat can be rewarding. The idea is to have fun building your boat, enjoy it on the water and then make money when you sell. My next adventure will be using one of my custom trawlers on the St. John River in FL. Use the "Ask Question" link on our Primary Web site to get the answers you need to build a great boat. Good luck.