Mini-Brig Project: Hull Construction - Step 4

Assembling and Fitting the Daggerboard Trunk Casing

Make sure that prior to placing the daggerboard trunk into the boat you have it assembled and have fully sealed the daggerboard trunk casing with the appropriate resins, reinforcing the seams with fibreglass tape.

There are two different plans/methods for the daggerboard trunk. One daggerboard trunk option is slightly wider and involves cutting through the mid-seat frame. The other design, is simply placed between the two frames.  The advantage of placing the daggerboard slightly forward, is it allows for better upwind handling. The larger width, also means it is possible to slightly reduce the aspect, and therefore draw less water. The second option is easier to install, and allows for more forward legspace. 

The downside to installing the trunk through the midseat frame is that it can be tricky, as it involves cutting out a small section out of the frame already in the hull for the trunk to pass through. In addition, it also takes up more room and leg space, although it can make a convienent forward seat

Both plans are included in the zip files - The first step in either option is to assemble the casing. However, before assembling and installing the daggerboard casing in either case is to select a resin system, and fibreglass cloth.

Choosing Your Resin

Industrial Plastics & PaintsThe first thing you need to do is decide what type of resin/taping method you want to use on your hull. The good folks at Industrial Paint and Plastics were great in providing sound advice. These guys really provide great customer service and help, and have been instrumental in helping with previous projects over the years including a restoration of a 'Stratford style' Dory and a wooden Sabot.

There are several epoxy and resin systems on the market. The best and most expensive system is a true epoxy resin and the least expensive is a general purpose orthopthalic polyester resin. There are many discussions about resins on the internet and it is a great debate amongst boat builders and hobbyists as to what is the best. However, there are some common methods and popular resins. In order to keep the costs down, we chose to use the lesser expensive polyester resin, and then coated it with a good quality paint.

West Systems Expoxy Picture
West System resins make one of the finest epoxies on the market. WEST SYSTEM epoxy is a high-quality, two-part epoxy formulated and manufactured by Gougeon Brothers, Inc. It bonds to fiberglass, wood, metal, fabrics, and other composite materials and is easily modified for a wide range of coating and adhesive applications. It is used for construction and repairs requiring superior moisture resistance and high-strength, and is especially suited for marine applications. If you want the best, and can afford it, get yourself about a gallon of this stuff!

51 Cure Epoxy

Industrial Formulators', 51Cure is an epoxy system for people who are looking for the performance of popular epoxy systems that mix at 5 parts resin to one part hardener and want epoxy performance at a lower cost.

Industrial Formulators Inc. is one of the major suppliers of epoxies for industries like construction, electronics, marine, automotive, sporting goods, and hobbies. Their formulations have been used to solve problems and are used regularly in pulp mills, submarines, dams, museums, railroads, and research labs, along with more conventional uses like boat building.


There are several basic polyester resins on the market. While not as strong or as durable as epoxy it is considerably less expensive. Fibreglass resin generally comes in two types, waxed and un-waxed. We used the "unwaxed" variety for greater paint adherence. We used Industrial Paint and Plastics IP140 General Purpose resins which exhibits a moderate exotherm temperature and cure to allow for thicker laminate applications. 



Choosing Your Cloth

The next thing you need to do is choose a fiberglass cloth and/or tape. You could buy larger sheets of fiberglass and then "strip" it into 4" or 6" width lengths to be applied as tape. We chose to buy fiberglass "tape" which ran about $1.50/CDN per yard to save the labour on stripping a larger sheet. It took about 18-20 yards to complete the project. There are basically two types of cloth available, chopped strand mat and woven. Chopped strand/surface mat is a material comprised of chopped fiberglass of various lengths randomly dispersed to provide equal distributions in all directions, held together by a resin soluble binder. Chopped strand is commonly used in laminates due to ease of wet out, the good bond provided between layers of woven cloth is comparatively low in cost. It can be hard to fit around corners, but does provide a smooth appearance as the fibres "melt" into the resin. This is commonly used for "all fibreglass" projects as a fiberglass laminate or as a reinforcement in-between layers of gelcoat. I find chopped strand hard to work with, as the "strands" are generally held together by the resin, and can pull apart if you try to "stretch" it across a surface. Chopped strand is generally categorized by "weight per square foot". It is commonly available in a 1oz x 4" Tape or 1 oz x 6" tape.

The other type of cloth is a woven cloth such as E-Glass or woven roving. In this project we used E-Glass cloth. E-Glass is woven from fine yarns of twist and ply construction with the actual glass being a lime-alumina borosilicate glass of low alkali content. This glass composition offers excellent flexural and tensile strengths, high chemical stability and high moisture resistance. The cloth weave allows it to conform to curved surfaces with minimum fitting and because of the woven nature it won't pull apart when stretched. An E-glass cloth tape with finished edges is available. E-Glass cloth is usually categorized by "weight per square yard". We used a 6oz x 4" cloth tape for all our seams.

Assembling the Daggerboard Case

Regardless of the epoxy/tape system your chose, you will need to make sure that your case is well assembled. It is a simple matter of cutting the two sides of the case and then using ample resin, wood screws and glue to hold it together.  A little fibreglass tape on the outside of the seams, will also help to seal and give it strength. Basically a 1" x 1" piece of lumber separates the two halves of the daggerboard.

Daggerboard Trunk Assembly
Basic Daggerboard Trunk Assembly

Make sure that prior to placing the daggerboard trunk into the boat you have it assembled and fully sealed. There are two different plans for the size and location daggerboard trunk.

Cutting the Daggerboard Slot

Method #1: Fitting the Daggerboard Trunk Through the Mid-Seat Frame

The trick to the daggerboard slot is to make sure that you place the daggerboard trunk in the boat, and check your fit before you cut through the bottom of the hull. If you plan to cut through the midseat frame using method 1, then measure the middle of the midseat frame and draw a line from the top to the bottom of the hull. Then measure the case, and draw a line on the end of the case from top to bottom along the middle. Match the middle of the case to the middle of the midseat and draw an outline of the daggerboard case, from the bottom of the hull upwards onto the midseat frame. Use a small handsaw to cut out the portion of the frame required to fit the case. You may need to cut along the bottom of the frame, and sand or file any excess material from the bottom of the frame, in a method so as to have a nice clean opening for the daggerboard trunk to sit. Periodically check the daggerboard trunk to the hull, and make sure it makes a flush fit with no gaps. 

METHOD 1: Cutting through the midframe

Where to Cut Midseat Frame

Daggerboard Trunk Placement
Method 1: Mounting the daggerboard case through the midseat frame.
Make sure before the case is permanately attached to the hull, that you cut a slot.



METHOD #2: Placing the Daggerboard Trunk Between the Frames.
In this method, we simply place the daggerboard in the middle between the seat frames. This daggerboard trunk is slightly narrower, but the daggerboard can be made longer to compensate for any adverse sailing effects. This method also eliminates the forward seat, which in useful in some cases. But the added leg-room in the bow can also be a benefit for larger-sized adults.
Daggerboard Trunk Position #2
Alternate Daggerboard Trunk position. 
This method places the trunk between the two frames.

Cutting the slot - for both daggerboard methods

The next step is to cut the slot for the daggerboard to pass through the hull. The easiest method for cutting the slot, is to trace around the daggerboard trunk, and then make an inner slot based on a 1" gap between the halves. You do this by marking a measurement on both sides that is 1/2" distance from the outer diameter, and on each end, marking a measure measurement that is 1" from the outer diamter. Then you link the measuresments together by tracing a retangular slot onto the bottom of the the hull.   After the daggerboard slot is cut, you will want to fair it up with a flat file and some sandpaper.

We attached the daggerboard trunk to the boat, by using epoxy and small brass screws to cinch it into place. They key to the daggerboard trunk is that it makes a good connection to the bottom of the hull. This is an area where water can seep through, so you want to be generous with caulking and make sure it is well sealed. It pays to let the caulikng dry and then go over the seams and find any potential gaps. In addition, you can reinforce the seams by turning the hull over and placing small strips of fibreglass tape through the slot opening.
At this point, you will want to wait until the caulking has cured for at least 24 Hours, and then sand/file any excess caulking. It really pays to make sure it is faily flush. You will also want to double check your trunk fit, looking again for any gaps etc. Once you are satisified, you need to tape all your seams, the easiest way is to take a paintbrush and spread some resin into the area of the seam, and then stick the tape to the resin. As you tack the tape into place, use the brush to thoroughly saturate the cloth. 
Another method is to take the cloth and soak it in a batch of resing, and squeeze out the excess and apply it to the seam. You can use a  small rubber roller to press the tape and squeeze the resin and air bubbles out.  We find the first method simpler and less apt for a large mess, and the brush is usually adequate for removing any trapped air bubbles.
Taping and Applying Resin to All the Inside Seams
First, grind down and sand all the caulked seams. Once the seams have been adequately sanded, and excess caulking removed, then apply resin and glass tape to all of the inside seams. We used 4" E-Glass fibreglass cloth tape along the seams, and applied polyeurethane resin.
Apply Resin and Tape To All The Inside Seams
Apply resin and tape to all of the inside seams
After allowing the resin to cure. The next step is to apply a second coat of resin over all the inside seams. It is important to note that we applied resin to the entire floor area behind the daggerboard trunk and in the stern seat. These areas will be filled with an expanding "liquid foam" which will provide positive flotation. We not only applied several layers of polyeurethane resin, but also covered it with a thick oil based paint. We will be putting "seat covers" on these areas once everything is in place. With the seats and positive flotation in place, the finish of the wood will not be seen. You can decide how you want to treat these areas, or if you prefer to hinge the seats for storage.
You may also want to "subdivide" the rear seat. In the Liberte we added port and starboard storage lockers. It is a simple matter of adding plywood dividers. The middle of the rear seat section is filled with foam chips. You may have other ideas for your seats, but it is always a good idea to include positive flotation in case of an emergency.
Liberte's Rear Seat Dividers
The rear seat dividers in the Liberte - Notice the 1x1" frame reinforcements 

Another shot of the rear seat dividers -
The middle chamber will be filled with flotation
After the resin has had a chance to cure, flip the boat over and applied resin and tape to all of the outside hull seams and especially the seam where the daggerboard trunk meets the hull inside the daggerboard slot.