building a sailboat mast

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How to Build a Wooden Mast

A tapered, oval new york 32 spar from the original plans.

ISLA, New York 32 No.10 (of a total of 20), was thoroughly rebuilt last year by Buzzards Bay Yacht Services of Mattapoisett, Massachusetts. The job included a new mast, whose construction is detailed on the following pages.

W hen my company was hired to restore New York 32 No. 10, ISLA, in 2008, the boat had been out of service for over 25 years. The 20-boat New York 32 fleet was designed by Sparkman & Stephens in 1935 and built over the winter of 1935–36 by Henry B. Nevins of City Island, New York. When we found her, ISLA was a virtual time capsule, with an intact original interior and a complete set of original hardware. But the hull and deck were tired, to say the least, and the spars were beyond repair. So, included in the work list were a new mast and boom.

The New York 32 carries a hollow, oval mast measuring 63′ 5″. The owners were committed to maintaining ISLA’s originality, so we acquired the original spar drawings from the S&S plan collection at Mystic Seaport. These included ample detail: spreaders, tangs, boom, and masthead, along with the overall mast plan. The following steps describe how we turned those drawings into a new mast for ISLA.

Ordering and Preparing Lumber ISLA’s mast is built of Sitka spruce, which has long been prized by sparmakers for its long, clear lengths, light weight, and impressive strength for that weight. From the plans we developed a lumber list for the mast, boom, and spreaders. While it is still possible to acquire excellent-quality Sitka spruce, it takes some searching and a keen eye for defects. We required at least 12/4 stock to fashion the forward and after staves.

For spars, it’s imperative that the wood be dry (below 15 percent moisture content) and free of defects. The grain must be vertical. Our first attempt to procure lumber for this mast resulted in us receiving a batch of 12/4 Sitka spruce that was case-hardened. It was dry to both the touch and to the moisture meter, but once milled and its center exposed, its moisture content went off the scale. When we tried to rip it on the tablesaw, it pinched the saw’s blade and stopped the saw. We replaced that batch of wood with properly dried material, and learned a lesson in the process.

We ran the rough-sawn boards we had purchased through the thickness planer to take “fur” off of each one, allowing for a better inspection of the surface of the wood. When doing so, we kept in mind the minimum thickness of the staves, so we wouldn’t carelessly plane off too much. With this done, we examined each board, measuring its usable portion, marking visible defects, and labeling each piece for its intended location in the mast. A board with tight grain is slightly denser and thus heavier than one with wider ring spacing; we strived to locate these heavier pieces toward the bottom of the spar. If another board had slight grain runout, we’d consider using it in the mast’s heel where it is under less stress and is backed by solid blocking. It’s also important to keep in mind the locations of the scarfs when selecting the lengths of stock that will compose each stave, for the scarfs must be staggered.

Utilizing the Drawing

The drawing shown here is an illustration of the original Sparkman & Stephens mast plan for the New York 32, whose vertical scale was compressed in order to fit the mast’s dimensions onto a single sheet of paper. From the drawing we created a table of offsets for the mast. To do this we drew a series of stations, 5′ apart, perpendicular to the mast’s centerline. We did this for both the side and forward views of the mast.

The drawing shown here is an illustration of the original Sparkman & Stephens mast plan for the New York 32

For the forward and after staves, we recorded the overall thickness of the stave (that is, its thickness before hollowing) and its half width. For the side staves, we recorded the thickness and width at each station. We converted the mast plan drawing from 32nds of an inch to decimal units, which I find best when working to close tolerances using digital calipers. We then made up 10″ × 10″ lauan templates on which to draw the sectional shape of the mast at each station. Since the forward and after profiles are arcs of a circle, we transferred these shapes from the drawing to the lauan with the aid of a compass. After each shape was transferred we cut out these lauan templates with a bandsaw. On each template, we also recorded the sidewall thickness, forward and after wall thicknesses, and distance from the heel of the mast. Building this New York 32 mast as was done originally requires hollowing out the thick forward and after staves in order to lighten their weight. So, once again using the mast plan, we made templates for the mast’s inside shape at each section.

The Spar Bench

The first step in building the mast is to construct a spar bench. We wanted a sturdy bench that was straight and set at a good working height. Typically, a spar bench comprises a series of sturdy sawhorses spaced 5′ apart and fastened securely to the shop floor. Identical wooden sawhorses work well for this; once they were secured to the floor, a mason’s string was run to assure that the tops were all in the same plane; the tops were then shimmed as needed to achieve this. The 2 × 10 plank seen here being screwed to the sawhorses is to support the staves during the scarfing operation, and will later be removed.

Gluing Up Full-Length Staves

On our nice, solid bench, we laid out the wood for each of the mast’s four staves end-to-end and developed a final scarf plan. We planed the stock to the maximum designed thickness for the forward and after staves (2.875″) and for the side staves (1.25″). Then we scarfed the stock together to create the full-length staves. Careful layout and labeling were required for this step. We examined the stock and put the most visually pleasing sides facing out, and we spread out the scarf locations to avoid clustering them. Scarfs were cut to a slope of 12 to 1, with their lines drawn onto the edges of each piece. They were rough-cut on the bandsaw, and then finished with a jig and a router. With the scarfs cut, we assembled the pieces dry and ran a string down each of their centerlines to confirm that each of the four full-length staves, once glued, would be straight.

When we were certain that the staves would be straight and true, we screwed blocks to the spar bench to chock them in place. The individual pieces could then be removed from the bench, turned over for gluing, and placed back in their precise positions. The final step in preparing the scarf for epoxy glue was to rough up the surface of the glue joint. Eighty-grit sandpaper backed by a long block works well for this, as does the technique we used: a Japanese pull saw drawn across the grain so its teeth combed the surface. (This process is for epoxy gluing only; resorcinol and other glues rely on smooth mating surfaces.)

Once the surface was roughed up, we vacuumed both faces of the joint and then wiped them with a clean rag and denatured alcohol until the rags came up clean. We then wet out both gluing surfaces with straight epoxy and allowed that to stand for several minutes while it penetrated the wood. Dry spots were wetted a second time. We then applied epoxy thickened with colloidal silica to one face of the joint. Using large bar clamps and modest pressure, we clamped the joints, making sure we had a nice, even glue squeeze-out.

Tapering the Staves

Once the staves were glued full-length, we selected the aft stave, blocked it straight on the spar bench, and snapped a centerline. Then, using the information from the lauan templates and the offset table, the points representing the stave’s profile were laid out and connected with a long, limber batten. One of the side staves was marked similarly.

We rough-cut the profiles with a worm-drive circular saw being careful to leave the lines intact. We then cut closer with a power plane, and then shaved precisely to the lines with an appropriate hand plane, making sure that the edges stayed perfectly square. With one stave of each profile now complete, we used each as a template for its mirroring stave, making the final cuts with a router and bearing bit to complete the second pair of staves.

To minimize weight aloft, the wall thickness diminishes as we progress up the mast. Once again we turned to the lauan templates on which we’d recorded the wall thickness at each station. Using digital calipers, we recorded on both edges of each stave the wall thickness at each station and connected the dots with our long batten.

This line, yet to be cut, is shown in the drawing. The stock was removed from the outside faces of the staves, the bulk of it with a power plane. The final cleanup was completed with a bench plane.

Rabbeting the Forward and After Staves

Hollowing the Forward and After Stave

The final step before gluing the staves together was to hollow out the forward and after staves. On the lauan templates we referred to the inside profile shapes we had recorded from the mast drawing. Dividing the inside profile into 1⁄4″ sections, we measured and recorded the depth at each section. We did this at each station. The inside face of the stave was thus lined off in 1⁄4″ increments.

Then, using a circular saw set at the depth indicated by the lauan template, we cut kerfs in the inside face of the stave. With each pass of the saw, we reduced the depth of the cut as we moved toward the masthead and farther from the center of the stave. With the kerfs completed, we used a gouge to scoop out the waste. We arrived at the final shape by using a backing-out plane followed by 80-grit sandpaper on a round sanding block.

With the staves cut to their profiles and tapered in thickness, and the forward and after staves rabbeted and hollowed, we double checked that the spar bench was still straight. The next step was to lay the after stave on the bench, sail-track side down, and hold it straight with blocks screwed to the bench so the spar could not move. We then did a final dry-fit of the three remaining staves to make sure all joints were tight.

When satisfied with the bench and the joints, we began mixing glue. A large spar such as this takes about four people to glue up; any fewer, and panic would certainly ensue. The glue-up seems to work best as a two-step process. The first step was to glue the side staves to the after stave, using the forward stave as a dry-fitted guide to ensure that the side staves remained parallel. We clamped the spar in 1′ increments, checking that it remained square along its entire length. Using the two-step process allows ample time to fit and install the solid blocking at the head and heel of the mast. The drawing calls for blocking in the bottom 11′ of the spar and in the top 2′ 6″.

The blocking is solid until about the final foot, where it tapers to a feather edge on either side of the spar, forming a swallow-tail shape to avoid a hard spot. This heel blocking has a drain hole, in case of water intrusion. There is no blocking at the spreaders; instead, the spreaders have an external bracket and blocking system that transfers the load evenly to the spar.

We coated all interior surfaces with epoxy. At this stage, we also ran all of the wires inside the mast, securing them with large cable clamps. (Conduit fastened securely along the interior of the spar—and through the blocking—works well for this, too.) When everything was satisfactory inside the mast, the forward stave was glued to the side staves to cap the assembly. Several varieties of clamps can be used when gluing up a spar: spar clamps, bar clamps, C-clamps, or a banding tool. We used a combination of clamps and a banding tool supplemented with wedges to further tension the plastic band.

With the glue cured and the clamps off, it was time to begin the shaping process. The first step was to plane off the excess glue. With that done, we again turned to our handy lauan templates and began the process of eight-siding the spar. Using the exterior cross-section drawn on each template, we found where a 45-degree line would be tangent to the mast’s outside surface at each station. We transferred these points to the spar, and with the long batten connected them with fair lines.

We then set our circular saw to 45 degrees and made a cut, just leaving the line. Repeating this on all four sides of the mast, and then fairing up the saw cuts with a power plane followed by a hand plane, yielded an eight-sided spar. We then lined the spar off again to 16 sides, but this time we omitted the circular saw and removed the waste with only a power plane. When we had the spar 16-sided, we finished the rounding and fairing with hand planes and a custom-built concave fairing board. Once again our lauan templates came into play, as we used them to confirm the correct shape at each station. Two other details that had to be considered at this stage were the shape of the heel of the spar, and the masthead detail.

With the mast now shaped and sanded, we broke out the varnish and applied 10 coats before installing the track and hardware. We were fortunate to have all of the original tangs and other fittings for this spar, because fabricating them would have required quite a bit more work. With the spar varnished the hardware was installed, carefully bedded in soft compound. We were very careful in fastening into the Sitka spruce, as it is quite soft. We chose machine screws rather than wood screws for mounting the winches and the boom gooseneck track—after testing these fastenings on offcuts to find the best pilot-hole diameters.

This article was originally published in  WoodenBoat No. 214, May/June 2010.

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15' Wooden Mast for a Sailboat

Introduction: 15' Wooden Mast for a Sailboat

In the event that you wake up one day and think, "Gosh, I could really use a fifteen-foot mast," I'm going to teach you exactly how to make one yourself, starting from scratch.

Actually, this tutorial is informative not only for aspiring boatbuilders, but for any application where you need to turn square stock into round stock.

The materials are easy to acquire, but you will need access to basic woodworking machinery.

• Hardwood stock - Sitka Spruce or Douglas Fir are traditional materials
• Wood glue - Titebond III is waterproof, affordable, and readily available
• Two Bic pens
• Two copper roofing nails
• Thickness planer
• Lots of clamps
• Drawknife or power planer
• Hand plane (#3 or #4 Stanley)

Step 1: Buy Lumber

Hit Up Home Depot

Assuming a fifteen foot mast, your finished dimensions will be 15' x 2.5" x 2.5". Depending on your geographic location, you should be able to find Sitka Spruce or Douglas Fir at your local box store or lumber yard.

If the lumber does not come in 15' lengths, buy enough lumber to splice two shorter sections together. If your lumber is less than 2.5" thick (likely) you will need to glue up two pieces for thickness.

Take the time to pick through the pile, looking for stock with tight grain.

Step 2: Mill and Dimension

Back at the shop, mill your stock square and parallel. If needed, glue up stock to get 2.5" thickness. Clamp and leave 24 hours.

Be sure to use waterproof glue. Titebond III is appropriate for outdoor applications, and readily available at hardware stores.

When clamping, remember that clamping pressure radiates at 45deg from the clamp heads. Use enough clamps to apply consistent pressure over the length of your stock.

If splicing, cut a 1:12 slope at the ends of your stock and glue up to get the required length.

Step 3: Square and Taper

Using a hand plane or cabinet scraper, remove any excess glue. Joint and square one set of adjacent faces, then square the stock with a thickness planer. Cut to length. Your stock should now be 2.5" x 2.5" x 15.'

If you are making a mast, you will want to taper the pole. Rather than apply a consistent taper, boatmakers like to use a gentle arc. Think of a blade of grass bending in a breeze. This provides strength when the sail is tugging on the mast.

Draw a center line in pencil on your stock. Your mast will taper from 2.5" at the bottom (0') to to 2" at a point near the top (13') and finally reaching 1.5" at the very top (15'). Mark these dimensions.

The profile of your taper will be drawn with the help of a batten - a flexible piece of wood which ensures a "fair" curve free of bumps. Any thin cutoff will do, so long as it is sufficiently flexible and of consistent thickness. Use clamps or lead weights to hold the batten in place, making sure it touches the three marks you just made. Trace the line.

Repeat on the other side.

With a drawknife or power planer, take the thickness down to your line, on both sides.

Repeat the process of marking the remaining two sides with the batten and shaping them with the drawknife or power planer.

Clean up the faces with a hand plane. You should now have a tapered rectangular pole.

Step 4: Octagonize

Making a Spar Gauge

This is my favorite step, a feat of ratios. It also involves a made-up word: octagonize.

The first step to rounding a four-sided spar is to make it an octagon. Once you have eight sides, it's easy to move to sixteen sides, and finally to the round.

Making your own spar gauge is surprisingly simple. Any scrap of hardwood will work, so long as the edges are square. Break two Bic pens and retrieve the inkwell reservoir. You can discard the rest of the pen. Insert two copper nails as fences at a distance slightly wider than your spar, and insert the inkwells between them spaced at a ratio of 1 : 1.4 : 1. You'll want to tap holes with a drill press or power drill first, and use the correct bit to ensure that your inkwells fit snugly.

A spar gauge will allow you to draw the edges of an octagon on any square stock as you drag it along, even as it tapers, thanks to the magic of ratios.

Use the spar gauge to mark a set of opposite faces, then work down to your line with a draw knife or power planer. Clean up the surface with a hand plane. Repeat for the remaining two faces.

Step 5: Sixteen to Round

From Eight to Sixteen

Every foot or so, draw a straight pencil line around the circumference of the mast. Using a hand plane, take passes along the length of the mast until the remaining line and the flats in between are of equal length.

From Sixteen to Round

At this point, you can almost taste sweet victory. Using a hand plane, take the corners off the sixteen sides. You will be close enough to round to sand your way to the finish line.

Sweep up your shavings. Find the nearest taco truck and reward yourself.

Step 6: Finishing

Two options for finishing spars for marine use are:

• Marine varnish, such as Le Tonkinois, which dries amber and glossy and needs retouching every season
• "Boat soup," a combination of boiled linseed oil, turpentine, and pine tar, a much lower maintenance "workboat" style finish

Be sure to use gloves and apply in a well-ventilated area.

Step 7: Go Sailing

Don't forget your life jackets!

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Wooden Mast and Spar Building

A mast or spar made from wood not only looks and feels good but it also takes advantage of the naturally ability that trees have developed over the centuries for creating a tall, strong, flexible pole.

Those tall straight pine and fir trees are able to grow to such heights and survive in wind storms because their natural elasticity absorbs the shock loads caused by gusting winds.

Structural Considerations

Solid/grown spars, rounding the square.

• Built Spars
• Your comments and suggestions

There are several reasons why soft woods are the chosen type of timber used in the making of masts and spars.

The first and most obvious is that so any soft wood trees grow exceedingly tall and straight.

And because they have grown so tall and straight they have developed the ‘elasticity’ to withstand all that the elements can throw at them.

Soft woods are also more likely to be lighter in weight.

Sitka Spruce (Silver, Tideland or Menzies Spruce) has long been the top choice for mast builders.

However many other spars have been built using whatever light, straight-grained wood was available, such as those shown below.

• Douglas fir (British Columbian, Oregon, Idaho, Red, pine also known as Red or Yellow fir)
• Scots pine (European redwood, Northern pine, Red pine, Redwood, Scots fir, Norway fir, Swedish fir, Finish fir)
• Port Orford cedar (Oregon cedar, White cedar, Ginger pine, Lawson’s cypress)

When choosing a timber look for one that is as light and straight grained as possible with, hopefully few knots.

However, a few small ones knots can be acceptable.

The timber should ideally be seasoned, especially if you are building a hollow spar.

I have heard of solid masts being made from green poles.

But green timber is more likely to develop shakes and will be less able to absorb any preservative, oil, varnish or whatever you use as a finish.

A mast/spar needs both strength and stiffness and be able to resist fatigue.

Sometimes these characteristics can be conflicting.

Strength or resistance to breaking in wood involves its elasticity which allows the wood to bend to absorb stresses.

Whereas stiffness is the resistance to bending.

All spars need to be able to absorb the shock of a gust which the wood absorbs by bending but too much bend will spoil the sail shape so a happy compromise is needed.

And stresses will differ depending on the types of rig and whether the mast keel stepped, deck stepped or in a tabernacle.

Another consideration is weight aloft.

Keeping weight within reasonable bounds is just one of the reasons for using soft woods.

It is also one reason for building a hollow mast.

However, most spars taper towards the top, as the diameter becomes smaller so the weight becomes less.

For the average cruising yacht the weight differences between a solid and a hollow spar are hardly significant.

The other advantage of the hollow, built spar is that it can be made from easily available timber sizes, and with a minimum of waste.

The simplest, easiest and least wasteful spars are produced from ‘grown’ timbers.

I theory it should be possible to acquire a trunk which has the length and taper needed for your spar.

In practice you will have to do some shaping, tapering and rounding.

While traditionally masts and spars were spherical, they don’t have to be.

However, in my opinion a spherical mast will produce the least turbulence to the air passing over the rig.

It is possible to make a spherical spar from one piece of square cross-section timber.

However, it will be much easier to source timers of smaller cross-section and then build the spar up from them.

And the advantage is that the grain can then be arranged in a radial fashion.

Building a spar from separate parts does require very careful attention to the gluing surfaces, they must be closely mating and the actual gluing must be precise.

If you are confident in your carpentry and gluing skills, short lengths can be scarffed  to produce the required length.

Scarf joints are best at least ten times the thickness of the piece and when the various pieces are assembled the joints should be staggered.

And remember to never ever cut a piece of wood to its exact length until you absolutely have to.

First determine the required diameter of your spar and then where you want your it to taper and by how much.

This will depend on the design of you rig.

You may want the spar to have no taper for some of its length/height, to just above the partners, then have a slight taper, perhaps as far as the spreaders,  then a bit more of a taper up to the truck.

Always best to start with the wood a little wider, thicker, and longer than the finished dimensions.

Plane one surface flat and level with your longest plane, preferably a jointer.

Then mark the center line on this planed face.

Use a string stretched between tacks in the middle of each end, use this to make several center marks on the timber.

Then join the marks using a long, straight batten.

Repeat on the opposite face.

Now use the centreline as the datum from which to mark the width of your mast at intervals along its length.

Then back to the batten to connect these marks.

You can now cut the outline of your mast to this drawn profile but cut it oversized as you still need to plane the timer square.

Now plane these two sawn, tapered faces flat and square to the original planed surface.

Repeat the steps for marking the center line and profile on these two new faces.

Cut this outline and plane these sides flat and square to their adjacent sides.

You now have a spar tapered to your requirement but it is still square in cross-section.

Now you need to start rounding the square.

So now you’ve got a nicely tapered, planed but square, four sided spar.

Next job is to plane off the four corners to give you an eight sided spar.

Then plane off those eight corners to give you a sixteen sided spar, which can then easily be rounded using sandpaper.

But before you start taking off the corners you need to mark the depth of the bevels.

The simple way is to draw a circle on the face of the timber with a compass.

The center of the circle will be on the centreline and the edge of the circle right on the edge of the face.

Then draw a line from the center of the circle, at 45 degree to the centreline and mark where it crosses the circle.

This mark is the edge of the bevel.

Do this for every transition point and as many points in between as possible, the more the merrier and do it foe both sides of the circle.

These marks can then be joined using your batten.

One you have planed the spar down to eight sides you can use the same method to mark it up for reducing it to sixteen sides.

But now the line from the center of the circle to the circumference needs to be 67 ½ degrees.

Now unless you are building a massive spar getting from 16 sides to 32 sides using the above measuring technique is going to become fiddly.

At this stage it is quicker to use your eye and your judgment to plane off the remaining corners.

Then the final rounding can be done by sanding.

Start with 60 or 80 grit paper for the initial shaping, then work the grits for finishing.

Use long strips of sandpaper wrapped around the spar and pull it backwards and forwards in a long, spiralling motion.

Occasionally sand along the length of the mast to help fair out any uneven spots.

Here is an easy way to mark out a tapered octagon using only one setting of your compass.

Building a spar is obviously much more difficult than simply shaping a solid pole.

However, if a pole of the required dimensions is not available building the spar might be the only option.

Built spars can be either solid or hollow.

But if you are building one it is relatively simple to make it hollow and thus save weight aloft and create a central channel for masthead wiring.

Building a simple cylindrical spar as those shown above from ‘square’ timbers does require wasting quite a lot of that expensive wood when 'rounding the square'.

One can build an almost waste free hollow spar which would suit a conventional bermudan rig.

However, a ‘square’ section with rounded corners such as this would be unsuitable for any rig which uses mast hoops or parrel beads or a lug rig where the spar turns against the mast.

The next problem when creating a hollow spar is that unlike the solid mast the taper cannot be created afterwards.

Any taper to the finished spar needs to be cut from the staves before they are assembled.

There have been several configurations used to increase the gluing areas across the width of built staves.

And several configurations which attempt to reduce wastage and at the same time produce large gluing surfaces.

Unfortunately while they will produce superb, strong spars they call for increasingly complex carpentry.

The ‘Birdsmouth’ technique developed by Nobles of Bristol UK is perhaps one of the most successful of these techniques.

However, it is a technique which really requires access to woodworking machinery, such as profiling and planing machines.

Setting up your standing rigging can be greatly simplified by using ‘Spectra’.

‘Spectra’ is virtually stretch free and can be tied off without much weakening.

It offers a real alternative to expensive swaged fittings, can be easily maintained and it is corrosion-free.

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A brief description of and how to tie some of the most useful boating knots. Including some that every boater should know.

Blocks and Tackle lines and sheaves.

How Blocks and Tackle work to give mechanical advantage and how best to rig them.

Handy Billy a traditional rope and sheave rig.

A Handy Billy made with two blocks and tackle can be used to give mechanical advantage wherever needed.

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Steps in Building a SCAMP sailboat

Links to all my scamp building pages.

My SCAMP build, Making a Mast

Cutting lots of strips for mast staves..

I'm getting ready to cut the mast staves and at the same time I'll cut the support strips. Scamp seams are built using a combination of stitch and glue and strips of wood that give a point of attachment to the thin plywood. Not quite chine logs but a framework of strips that add rigidity and increased gluing surface.

It took a bit of time to clear the table saw, set up an out table, make sure the blade was perfectly square and set up the feather boards and stop blocks.

Because I'm cutting 2x4 lumber down to thinner strips some wood will certainly warp as I cut and there is a real danger of binding and kick back. The feather board and stop blocks make the process much safer. I also cut in 2 swipes, this helps release the tensions.

I spent a couple of hours of quality time with my table saw and ended up with a large pile of strips. I've rough cut only the thickness of the strips, the width I'll do later. The support strips which will be used to support various parts of the sailboat such as the seat, are 20mm plus a bit for shrinkage and planing, the mast staves are 17 mm plus some for cleaning up and I have some extra planks of various ends at about 15 mm that I can glue up if I need more strips.

I'm using 8 feet lumber select grade. There are lots of small solid knots. I'll have to remove any large knot and scarf pieces together for the mast, time consuming but it works well. That's what I did for my Skerry mast and it has been rock solid. I used old knotty pine shelving. It was a sort of patchwork mast.

NOTE IN HINDSIGHT: It took quite a lot of time to glue the pieces together and IF you consider time it would have been cheaper to buy better wood. I just did not have easy access to it. In terms of strength the seams are good so I don't think I've compromised strength.

This lumber is mostly spruce. I can see that there is the odd board of other wood thrown in.

I've cut lots of extra so I can pick the better pieces and use the rest in other projects. I always seem to need bits of wood.

I'll plane them after a day so that they will have had a chance to warp if they plan to.

Cutting the pieces for the mast.

After planing the long strips, I set up the table saw to cut the notches. I don't bother cutting the width of the board because when I cut the notch the width will automatically be right

Instead of using the fence I clamped a board. It is easier to feed and some of my boards have slight warps and this makes it easier to cut.

The blade is at 45 degrees. I've checked and measured the width.

I'm using 2x4 x 8 feet and the mast is to be 16 feet so I will have quite a number of smaller pieces that will need to be joined. I don't want to have to set up to cut really long strips, everything gets complicated and I have to feed to the outside because I don't have 32 + feet. That's why I have a garage door in the shop. It's winter and it's cold so I'm using a comfortable 8 feet.

I cut a couple of test pieces and assembled them. I'm finding that the plans's 30 mm long gives me a slightly too large diameter. I guess that there is a bit of extra for sanding and finishing.

I set this up to cut the scarf joints. I will need many joints to get the full length and to cut out the bigger knots or flaws. I did this for my Skerry mast and it has held up beautifully even though it was made of softer pine. My boards are spruce for the most part.

The blade is at a slight angle and the jig holds the piece to be cut between 3 guide boards. The little clamp holds it while I slide the whole thing through the blade. It fits on top of the table saw fence.

The blade is as hight as it will go and this gives me a 6 to 1 scarf, or a bit more. This is not ideal but I used an even smaller scarf on the Skerry and got away with it so I'm confident this will work. The joints end up looking like curved lines in the round mast and actually look like wood grain so it blends in well.

There are many ways to cut a scarf joint but this will be very easy, safe and fast.

The joints should be staggered so that they do not weaken an area. It looks better too. I'm not sure that a joint like this weakens the board because the filled epoxy glue is stronger than the wood and I will be coating the mast with epoxy as well. I don't think the mast is expected to bend very much

I did a quick check to make sure the pieces fit and they are nice and flat and well cut.

Joining some of she shorter pieces. Since the mast is to be about 16 feet and I'm using 8 feet lumber, there are at least 3pieces for each stave. I've cut out any of the larger knots and that means many more joints.

This allows me to use lesser quality wood at the expense of having to take much time building the mast. There are no handy lumber yards near here so it's not easy to go shopping for nice wood either.

Now that all the cutting out of bad knots is done the putting together will go quickly. For a while I had stuff everywhere and not a surface to work on. I've spent some time and cleared sawdust and extra wood away.

Once I have all the staves cut out and lined up so there is no join at the same level, I will plane them so that the mast tapers when it is put together.

Detail of one of the joints. I've checked the ones I've done so far and they are all sound. I'm sure the joints are more sturdy than the wood. I don't think this mast is intended to bend so having stiffer joints is not an issue.

8 pieces 17 plus feet long ready to be slightly tapered. I'll probably use the belt sander. There are too many small knots and joints to use the bench plane.

After measuring the staves and cutting them even, I realized that I had mis-measured. I will be about 10mm short. Dang and Poot!

I clamped the bundle together and using the belt sander thinned out the staves to create the taper on the mast. It worked very well.

Now I'm bracing myself, a nerve wracking marathon glue session to put it all together.

I plan to put 3 pieces of wood inside the mast at vulnerable spots, the base, the top and where the mast touches the top of the cabin.

The core was cut from a piece of a pallet. I had to experiment to figure out the size for the top of the mast but I got it.

I made a glue spreader from a plastic bottle. I used one when I made the Skerry mast and it works really well. By leaning it you can control how much glue is left and the sides keeps the glue from going to the sides of the wood.

I measured out several glasses of epoxy what I could mix quickly as required. In the end I under-estimated how much I would need and had to measure some more.

I like to use a gram scale to measure the epoxy. It's fast and more accurate than I can measure by making marks on containers. The pumps are not as accurate I think. At least not the ones I had. I don't think it really makes much of a difference. In this case I'm using MAS epoxy and the hardener and resin are almost the same weight so there is not a significant difference if it is measured 2:1 by weight. How do I know, I tried both ways.

I put plastic under the mast parts, got my gloves, epoxy, thickeners, drill with bit, clamps, plastic ties, paint brush, baggies, scissors, tongue depressors, put some wood on the fire, chose some music, and finally took a deep breath.

The first part is easy, coat the V and the inside face with epoxy so it does not suck up the glue and starve the joints. No problem if that starts to kick off.

The next 2 hours are fast paced and insanely stressful, at least for me. I mixed epoxy, thickened it with silica and wood flour, squeezed in the V, spread it as best I could, and repeated this until I had all 8 strips, all 16 feet of them, done. I would change my gloves regularly.

NOTE: In Hindsight I would have been better to forget about my little spreader and line up the 8 strips V side up, and paint on the thickened epoxy into the 8 together, maybe clamping them temporarily side by side. There would have been more squeeze out when I assembled them but it would have taken less time.

Even though I'm using slow hardener, and the shop is not warm, I only have about 45 minutes of open time. I was getting close to this and had not even put the mast together yet, let alone clamped it.

Sorry I have no photos, I was working too fast and everything was sticky.

Some pipe clamps and many zip ties secure the mast.

When I made the mast for the Skerry I had a lot of trouble getting everything together. This time I was wiser. I had put bar clamps with the end making a fence sticking up and stopping the staves from falling off the table so I did not have to worry about both ends at once. I took the photo after removing the clamps and taking the sticky gloves off the workbench.

When I made the spars I actually made a few semicircular stands that help position the staves. That worked well too. My Page on making the yard for the SCAMP

I went to the top of the mast, and forced the staves in position. I did not worry about anything except getting the very end lined up. This was quite easy to do. I slipped in the core which I had covered with thickened epoxy all ready to go. I then slipped on a round of cut off plastic pipe to roughly clamp the end and put a pipe clamp on. I then went down to about half way and manhandled the staves till they were in position, slipped on a clamp and went to the spot where I had marked the position for the core piece at roof level and put in the core and put a clamp. The end was pretty much in position so I put in the bottom core and put on another clamp. I used the drill with a driving bit to tighten the pipe clamps

Now my time is getting short, my epoxy is just starting to get thicker and it's harder to get it to squeeze out, YIKES. It took a lot more force than it would have 15 minutes earlier. I eventually got the mast clamped. I used pipe clamps and plastic ties. I had not expected to need a lot of pipe clamps so I had to tighten with the pipe clamp, put on a couple of plastic ties and remove the pipe clamp and go tighten further down. I had a couple of spots that did not want to squeeze in and I used a bar clamp to push in the resisting stave. Once pushed in I could add a plastic tie or 2 and move on. Once in position the staves did not come back out so the plastic ties were enough to hold the mast in postion. I had prepared plastic wrap but that was not enough force.

I spent some time going up and down the mast, tightening the clamps, adding plastic ties and removing some of the squeezed out glue.

By this time everything is gummy, the screwdriver and drill are covered with epoxy and some sawdust, I am covered with goo and I'm a basket case. There are used gloves everywhere and my glue mixing table is a mess. The good news is that the Scamp mast is together. It is also quite straight with no significant bend.

The Bird mouth method of mastmaking is very forgiving and for the most part a mast will be fairly straight unless it was clamped very crooked.

I spend the next while checking that the mast is straight and that there is no obvious problems. I checked the level of the supporting table and various bits I had set up to support the mast and wedged in anything not quite right. I had lots of little wedges from the joints I had cut so that worked out well. I put a log on the fire so that the shop would be warm to set the epoxy and went back to the house with my drill hoping to get some of the goop off. I used vinegar, not great but it got some of it.

The next morning I took off the clamps and snipped the plastic ties. The epoxy has set and there is no obvious flaw. It seems quite straight too.

Using my smoothing plane I have started rounding the mast. I plan to gradually work around the the mast rounding it. There are a few small gaps where the epoxy did not squeeze out. I'll drip some epoxy and hope it fills any gap. I don't think there are many though.

This is what the mast looks after my first pass. I'm not being particularly careful at this point since I'm still roughing off the extra corner.After going around the mast once my plane is already starting to feel dull. Silica thickener is rough on a plane edge. I sharpened it and am ready to get back to rounding the mast.

I've been rounding the mast gradually using my smoothing plane. The shop is warm, I have nice music on and I'm just gradually rounding the mast. I'm up to my ankles in shavings. I'll collect these, they are good to start the fire.

By the end of the afternoon I have a roundish mast. I'll need to sand some more but it's not bad. I had some tear-out in a couple of spots while I was planing so the sanding should take care of that.

I've checked the diameter of the scamp mast and it's about 2mm over. I'm hoping that will come off when I sand.

It's a bit heavier than I had hoped. I'm not finished shaping it so it will lose some weight, and I can handle it.

I spent most of the day sanding the mast and getting the flats out. It is now as round as I can get it. I need to finalize the size. The mast turned out about 3 mm too thick in most parts.

I checked the weight and I'm just short of 17 pounds.

Today I will finalize the size. I checked and rechecked the diameter and took my newly sharpened plane and took off a very thin shaving all around. After a couple of hours of careful planing and sanding I'm very close to exact size and that's good enough for me. The mast now weight just under 15 pounds. It will put on a bit of weight with epoxy and varnish but I don't think I'll be much over 15 pounds completed. Compare that to my carbon fibre mast which is just under 4 pounds for a 15 foot mast.

The top of the mast is tapered slightly less than the plans call for. My wood is not high quality and I'm not happy thinning it too much. It's only a couple of mm larger than the plan. There is a core for about 8 inches. I like the end to be full to support any screw or attachment that goes on the top.

I used the drill press to make a half inch hole in the top of the mast. It's useful to have a spot to quickly tie things to.

I used files and sandpaper to smooth the hole opening so that it will not damage lines tied to it.

After trimming the bottom of the mast I sanded everything with a fine paper, vacuumed it really well and wiped any dust off. I paid particular attention to a couple of spots that did not have enough epoxy between staves.

I made up a thickened epoxy and filled any gap and a couple of tear out spots. I then coated the mast with a coat of un-thickened epoxy. I plan to put 2 or 3 light coats of epoxy.

Fast forward a couple of weeks. I've been making the centreboard but I've almost run out of epoxy so I have to wait till tomorrow. Noah has promised delivery. I had put a couple layers of epoxy on the mast but it took some time to harden because of the cold. It's nice and set and is not clogging sandpaper anymore.

It's difficult to make sanding look interesting. We all agree that it's important but not much happens. Maybe I'll make little piles of sawdust and measure how high they become.

Anyway, I'm getting ready to add a final coat of epoxy on the mast. This will be the third. I had a couple of drips and various imperfections. I put on some music and sanded away while Edit Piaf sang to me. I'm not doing a perfect sand job. This will happen after the last of the epoxy has set. I'll put a coat on tomorrow and then get the scamp mast ready for varnish. I've been warming the last of the Mas epoxy because it was starting to crystallize. All epoxy will crystallize in cold weather, I've had the same problem with East System epoxy. After warming up the epoxy is fine.

I've put 3 coats of epoxy on the mast and let it sit for a couple of months. I'm now back at it sanding the epoxy in order to start varnishing. Because epoxy is sensitive to UV it must be protected.

I'll be using Epiphane varnish but with a small amount of stain added to help blend in the various colours of the many strips.

I've moved on to making the spars.

emails: Christine

This web site reflects my personal ideas and doesn't represent anyone else's point of view.

If you decide to build a boat be careful. These tools can be dangerous. If you don't know how to safely handle something find out. There are lots of forums out there.

On the Newstand and Digital Library Now - November/December Issue No. 301 Preview

Hollow Wooden Masts

By reuel parker.

For many millennia, sailboat masts have been made from trees. Trees are an obvious choice, as they are essentially ready-made masts, as if designed and grown for that purpose, which indeed they are, right down to the correct taper. Dry them out, strip the bark off, seal the wood, lash on hardware and rigging and off you go!

Of the tens of thousands of years that this has worked for us, it has only been in the last one hundred and fifty years or so that anything has changed. I think the introduction of the “yacht” had a lot to do with this. As man’s world changed to allow the creation of “leisure” and “sport,” he began to invent boats that could be used for pleasure and recreation instead of fishing and transportation (to say nothing of war).

Lighter, faster, more responsive sailboat hulls correspondingly required taller, lighter, more exotic rigs. Using tall, small-diameter trees for these rigs did not provide satisfactory results: the weight and flexibility of solid masts required too much rigging to support them, and overall weight became an increasing liability. Lighter woods were sought, such as Sitka spruce, but it soon became obvious that what was needed were hollow masts.

An early method of making hollow masts from large stock.

Early attempts at making hollow masts included burning out the heartwood (not a raging success); drilling out the center (practical only for short lengths); splitting the mast in half, hollowing out each half, and gluing the halves back together (requiring good glue); and making masts from plank stock. The problem came down to finding glue that was both strong and water resistant. Mast halves could be joined using mechanical fasteners (awkward) or binding (vulnerable), and interlocking joinery might be helpful—but ultimately glue was the weak link.

With the invention of “Resorcinol” and “plastic-resin-glues,” new possibilities became available, and with the advent of epoxy, everything changed. The above drawing shows a mast section made from two halves (or four quarters). The V-cut through the center provides a raceway for wires, lightens the mast weight, strengthens it and de-stresses the glue joints by allowing some uneven expansion/contraction. It is preferable to expose “vertical” grain on all exterior surfaces for stability and durability. Because nearly all the strength of a spar is on or near the surface (tension & compression), material beneath the surface adds weight and inertia, thereby weakening the mast. Hence the hollow portion shown may be considerably larger, within reason, depending on whether the mast is stayed or free-standing. The hollow center should decrease in size with mast taper, and be sealed or terminated below the masthead. This method is also excellent for booms and gaffs where some weight is desirable.

Box section spar, hollow-center, 3 ½″ x 5″

I have used the above method extensively for many years for masts, booms, yards and gaffs with only one failure, which was caused by a poorly placed knot and gale-force winds. My preferred wood for all spars has been Douglas fir, air-dried. For solid spars or two-part laminations (as above), I use #2 material. I often search through lumber yard construction-grade stock, deliberately choosing old, checked, slightly twisted or warped timbers (large material), which I am frequently able to purchase “at cost.” I re-saw and re-surface the timber to straighten it, and to obtain vertical-grain (quarter-sawn) exposed surfaces. There is often substantial waste, which I use for blocking and stack laminations (like deadwood keels).

A very popular lamination technique for sailboat masts and booms employs the “box” section shown to the right. Many yachts employed this method throughout the early and middle years of the 20th century. Such spars were laid up on long “spar benches”, using dozens of clamps to hold pressure on the resin-type glues available at the time. Many of these spars were made from Sitka spruce, and some are still around. With meticulous maintenance, they can be very durable, but they usually failed where metal hardware was attached to them. I sometimes build booms for marconi-rigged boats using this method, as the flat surfaces are convenient for attaching bee-rails, tracks, cleats and cheek blocks. With epoxy glue, very few clamps are required, and I often use a nylon “spiral-wrap” to clamp the spar during curing. By inserting PVC or Nylon tubes (with epoxy) through the wood where hardware is through-bolted, the rot problem is eliminated. You can also use marine plywood in lieu of the solid-wood sides, saving weight and making the box section even stronger and stiffer.

Hexagonal mast section from 2x6 stock; 7 ½″ diameter.

For larger spars in vessels over 35 feet, I borrowed a mast-lamination method from multihull designer Chris White. Chris made a pair of free-standing masts for his big trimaran JUNIPER, leaving them shaped hexagonally with gently rounded corners for sleeved sails. While Chris used splines for his glue joints, I made my spars from thicker segments, eliminated the splines, and rounded the masts instead of leaving them faceted. We made many masts, booms, yards and gaffs with this method, both free-standing and stayed, and had excellent success with them. They are all still in service, some since 1985. The drawback with the hexagonal section is that the mast panels must be fairly thick to achieve good gluing surfaces, adding unnecessary weight. Hence when I was made aware of the “bird’s mouth” method, I switched.

Octagonal/round mast using the bird’s mouth method.

I believe Nathanael Greene Herreshoff may have invented the “bird’s mouth” method of joining eight full-length mast panels together using interlocking joints. By cutting a 45-degree V in one edge of each mast panel, the opposing square edge locks into the V forming an excellent mechanical joint as well as increasing the gluing surface. Note that in all laminated masts, the segments that make up each panel must be long-scarfed (8:1) together prior to mast lay-up, and that the scarfs should be staggered between adjacent panels by at least 24.″

When possible, I use air-dried, clear, heart, vertical-grain Douglas fir plank stock in my hollow laminated masts. I have, at times used kiln-dried Douglas fir, but panel-thickness is limited to 1 ½,″ and the cells are damaged by the intense heat. A friend made a mast from kiln-dried Engelmann spruce, which is still in service after 25 years. The key is to saturate the wood, inside and out, with penetrating epoxy. It is best to epoxy prime and polyurethane paint the mast exterior for low maintenance and longevity.

In a future blog, I will describe making masts using the bird’s mouth method. I will also describe making rotating wing masts.

Appleton, Maine, 11/18/2013

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