Fiberglassing the Mast

It's been an unbelievably long time since I finished building the mast and last posted about it here in (October 2007). Things do get in the way, despite best intentions when undertaking a project like this! Anyway, the mast has been hanging from the rafters all this time, covered in the dust of building and fairing the hulls. I lowered it down last week and pulled it out enough to get to the masthead end and begin the tedious task of sheathing it in fiberglass:

Round objects are not the easiest things to fiberglass, but it's not as bad as it would seem if you plan in advance and use the masking tape method to avoid epoxy runs and ragged fiberglass cloth overlaps. As seen above, the masthead section has the additional complication of the shroud hounds to go around, as well as the mast cap and crane.

The other sections, as shown below, are simply round and are best done in by going around half of the circumference at time. After the epoxy cures, the tape is cut away, a weave-filling second coat is applied, and the mast is rotated 180 degrees to complete the other side. I'm working in 4-foot sections, as the roll of 6-oz. glass cloth I have on hand is 48 inches wide.

There are specially-made fiberglass sleeves that fit on like a sock that some people use for processes like sheathing round masts, but with the hounds and mast step protruding from each end of the spar, it seemed to me like this might be difficult to get on. In addition, these sleeves are much more expensive than ordinary glass cloth. At any rate, by using the taping method, this is a straightforward operation and will result in neatly-sheathed spar when it's all complete and the cloth has been filled, faired and sanded. The mast will be painted the same Off-White as the decks.

Below, the top 12 feet or so is now sheathed. The short PVC pipes protruding from the masthead are the wiring conduits, which will be cut shorter and capped off with PVC elbows to keep rain out once the wiring is run.

Making it Round

The mast is now finished, except for the final epoxy coating and sanding in preparation for paint.

It was fairly simple to take it from the square box-section after glue-up to the final round shape. I would have been done much sooner but had a lot of interruptions last week.


The first step in rounding the mast was to cut it down to 8 even sides. I did this by first laying out straight lines to divide it equally for the entire length of the mast. I then cut just outside the lines with a 7 1/4" circular saw set to a 45-degree angle. The final cut down to the 8-sided lines was done with a handheld power planer and then smoothed with a belt sander. The 8-sided spar is shown below:

After cutting the 8-sides, I first made and fitted the 4 hardwood rigging cleats, or "mast hounds" at the top of the mast. Then additional lines were drawn, laying out 16 even sides which were cut down the lines with the power plane. After this operation, the remaining 16 corners were flattened with the plane to 32 even sides, and from this stage the mast could be rounded by working these sides to round with a belt sander and the 6-inch orbital sander. I did all this on the bench where the mast was laminated, spending about a half a day on the shaping. The tools used are shown below: Power plane, belt sander, 6-inch random orbital sander, 5-inch random orbital sander, and block plane and sureform tool for areas where I couldn't use the power tools.


At the base of the mast I decided to leave the part where the mast is solid 8-sided. I like the way it transitions into round, and it will make it easier to install such hardware as the halyard rope clutches. The wiring conduit is shown where it exits the sidewall. There is one on each side.


Today I moved the finished mast out in the open and applied the first sealing coat of epoxy. The workbench is now free and I have the keel for the second hull scarfed and clamped on it now. When that cures, I will begin the process of wiring the second hull together, then suspend it from the rafters while I tear out the bench to make room for cradles to lower the hull in so I can begin construction.

Mast Assembly Details

I just completed the assembly of the mast this afternoon when I glued on the final side wall to close up the hollow box. I counted a total of 43 separate pieces of wood in the mast assembly, counting the scarf sections for the long pieces. It's definately not the work of a weekend or couple of evenings, but it went reasonably fast and everything went together smoothly. The photos below show a few of the details and the assembly sequence and methods I used.

The mast head has a built-in crane for the main halyards and internal wooden sheaves for the jib halyards, separated by a central divider. I built this assembly as a separate unit, so I could insure that all the exposed areas around the sheaves were well-coated with epoxy. In addition, the bearing surfaces of the sheaves, which are made of mahogany, are glassed over and then coated with an epoxy and graphite compound for a smooth, durable surface. You can see the black graphite epoxy coating in the photo below:


The masthead also has solid blocking around the crane area. To get a wiring conduit through this area I built the blocking with a channel just wide enough for it to pass through in the center. The conduit is flexible plastic irrigation pipe, with an I.D. of 1/2 inch. One of these in each mast half should give me enough space for a VHF coax, 12-volt circuits for a masthead tri-color and anchor light, and a cable for a Sea Me active radar reflector.

At the foot of the mast the conduit exits the side walls just above the solid wood packing above the mast heel. This wood packing at the foot is to allow for long screws to mount halyard clutches and blocks. I routed the wiring out the side walls since the aft side of the mast is occupied with the clutches and the forward side is taken up by the mainsail downhaul.

To keep the conduit out of the way during the final assembly, I epoxied in these tiny slats of 6mm ply. These weigh next to nothing and were simple to make. I ripped a couple of strips of the ply to the right width with 45 degree angles on both sides, then chopped them up into 3/8" wide pieces. They fit perfectly, the ends dipped in epoxy and simply laid in place to dry.

The slats also make it easy to pack aluminum foil into the mast halves by tucking it under them so it too does not move when the pieces are put together for lamination. The foil inside is supposed to be a passive radar reflector. I don't know how effective it will be, but it can't hurt anything and it was certainly cheap.

Here is the final assembly. I now have a straight, hollow box section mast. When the epoxy cures it will be ready to cut down to eight sides, then sixteen, and finally round. But that will be a job for next week.

Keeping it Straight

No matter how carefully you select the wood, with eight separate staves more than 26 feet in length, there is bound to be some tendency for some of them to bow or spring out of true, due to natural crown or grain patterns. The only way to insure that you get a straight mast is to laminate the sections with a form that is dead level and absolutely straight. I had already glued the triangular wood fillets to the two mast halves using the straight edge of my workbench. This worked fine, but one of the halves still had a bit of crown in it after removing the screws used to glue in the fillets. It's a simple matter to get it back in line, as long as you have a straight form to clamp it too. I built a lot of straight and curved forms recently while working on the pergola project in Florida, so I figured it would work fine for my mast as well.

The first step was to screw down a platform of 2 x 4s to the work bench, to elevate the mast sections clear of the bench so that bar clamp jaws can fit under them. The bench was already level, but after screwing down the platform boards I checked them all with a spirit level and with a taunt line. The ends were also aligned with the taunt line so that when upright blocks were screwed on at a right angle they were all dead in line. This form allows clamping in two directions, vertically and horizontally, which is necessary when glueing the mast laminates together to be sure all joints are closed up with no voids in the glue line.



In the plans for the Tiki 26 mast the method of assembly is to use rope lashings to pull all the parts together. This is assuming most first-time boatbuilders won't have enough clamps of a sufficient size to assemble the mast. The rope method works, and I used it on my Hitia 17 mast, but with the weather as hot as it is here, limiting the working time of the epoxy, I didn't want the stress of trying to assemble all four parts of a 26-foot mast at one time. In addition, this mast will have wiring conduit inside, as well as aluminum foil for a radar reflector - more stuff to worry about keeping in line while trying to hold and wrap four long, springy pieces of wood. Since the mast diameter is only 5 inches, relatively inexpensive 6-inch bar clamps work just fine for all the assembly steps. I used 40 of them, and this was plenty adequate for close enough spacing to close up the parts. Instead of assembling all four parts at once, I started by glueing one side wall to the aft wall, using the form to keep it all in line. This worked out perfectly, and when the clamps were removed this morning, this half of the mast was rigid and straight with no tendency to bow.

Mast Building

The Tiki 26 laminated hollow mast is well-designed and simple to build compared to most wooden mast building techniques. There are a lot of parts to cut and assemble, but each step is straightforward. The construction begins with preparing the wood by ripping it to width and then scarfing it to the required length. All scarf joints are cut with a minimum 12:1 ratio for strength. Below are the scarfs for the two main half panels. These are 3/4" thick, as that is the required wall thickness of the finished spar.


Inside the mast are triangular fillets of solid wood that hold the four outer plates together and provide enough wood inside to maintain the wall thickness when the mast is cut down to the round section. These fillets are cut on a 45 degree angle from two-by fir stock that was first scarfed to full length.

To establish a straight line and compensate for any natural crown in the mast lumber, I first clamped the halves to the bench and lined them up with the straight edge of the top surface, double checking with a taunt line. The first fillet is glued in place, and when this joint cures the laminate helps hold the plank in line.

All of the fillets are now glued in place on both halves, and everything came out straight and true. The next step is to make and install the many parts that make up the masthead and the mast foot.

Below at left is the mast heel that fits inside the spar at the foot and pivots on the mast step that will be laminated into the top of the mast beam. The step and heel are made of laminated mahogany. To the right are the ply parts that make up the mast crane.

Mast and Beams

I've decided to go back to my original plan of laminating the mast before I remove my 26' long workbench that is in the way of assembling the second hull. Although I am anxious to get the second hull built, it will be more efficient to make use of the workspace I have to glue up the mast. The finished stick can then be hung from the rafters out of the way until the hulls are completed. Hopefully, I won't need a long, flat bench again for any other parts of the boat. All of the stringers are made for the second hull, and I finished assembling the topside panels with their stringers installed last week. The mast is a fairly big project, because of the many components. The first step is to cut the stock to the required widths, then scarf the pieces to get the length. The rough stock shown below is 16' lengths of Doug fir, in 1x6 and 2x6. The 2x6 pieces have already been ripped to 2" widths. These will be cut on a 45-degree angle to make the interior fillets after first scarfing them to full length.


Before the mast lumber arrived I finished assembling the topside panels for the second hull. Shown below is the last one, the upper stringer being glued on by clamping it between the panel and the flat bench. These panels can also be hung out of the way while working on the lower hull assembly.

Back at the garage workshop this weekend, I'm making steady progress on assembling the crossbeam components. First the stringers that stiffen the vertical webs, and then the floor panels, to which the webs are laminated. Like the mast, these beams have many parts and just getting the all put together will take many glueing operations. It's good to be able to do this in another location so these parts are not in the way of building the hulls.