Wooden Masts and Spars

Doug sanding the mast

Making masts and spars in timber isn’t as difficult as many would imagine, but it does require a reasonable level of confidence and woodworking skill and a few basic tools. Planes (smoothing and jack), spokeshaves, chisels and gouges are the hand tools needed, along with a few drills and bits. If using power tools, an electric drill, electric plane and orbital sander are very useful, as possibly is a router on some types of mast.

Wooden masts can be solid or hollow depending on the type of boat and rig that will be suspended on them. In its simplest form a solid mast made from one piece of timber is quite quick and easy to make. The main criteria is the quality of the timber which must be very carefully chosen, it should be the right timber for the job, straight grained fir and knot free with no curve.

The next step up would be a solid mast made from a piece of timber that has been ‘spilt and reversed’ this means cut in half down the entire length, one half reversed end for end then the two pieces glued back together to form a straight solid piece, essentially a very simple form of laminate. This takes the stress and any curve out of the timber and is very common practice when longer masts are made.

A more sophisticated mast would be made in a similar manner to the ‘split and reversed’ mast but the centre core is hollowed out for lightness with solid or thicker walled sections where fittings would go e.g. crosstrees etc and of course the base and top of the mast would have solid sections for the tabernacle or mast step and to take the standing rigging fittings etc. Hollow masts often have a sail track formed in the wood to take a luff rope, or perhaps a recessed or flush mounted mast track screwed in place. There are also mast shapes that are more complex to construct, but for the purposes of this article I will restrict it to simple constructions.


Doug shaping masttop

The method of shaping a basic solid round mast, typical of the type seen on most Drascombes is quite straight forward. Firstly you need to select a good quality piece of timber. Columbian Pine or Douglas Fir are good timbers to use, straight grained, very resinous and durable, fairly easily obtained in longish lengths knot free. It’s also quite a good timber to resist knocks and wear. Sitka spruce and Silver Spruce are also very good timbers to use, especially where top weight is a factor, they are both lighter in weight than Columbian Pine or Douglas Fir but also more susceptible to bruising and wear.

Having chosen the variety of timber, you need to begin by selecting and obtaining a good straight grained knot free square section, use a good timber merchant who will advise you and help with the selection if you are not confident enough yourself. A planed surface is ideal rather than a rough sawn surface, but not essential because a hand plane can easily remove saw cuts to provide a smooth enough surface to mark out and plan your shaping on.

The method of shaping begins with converting the square section to octagonal, to do this you need to use the ‘rule of 12’ this give the correct markings to end up with an accurate markings for octagonal section.(see drawing) The markings are your guide for the first cut. At this stage it would be advisable to make some ‘V’ blocks from scrap timber to support the mast on a long workbench or trestles; a piece of foam rubber in the ‘V’ blocks will help prevent marking the wood when working on it. Before progressing further, it’s probably the best time to cut slots for sheaves and drill the holes for tabernacle bolts etc, it’s much easier to cut or drill them square through the mast from a flat surface rather than wait until it’s a round section.

With the preparation done, you can move on to the first stages of removing the waste timber on the corners to form an octagonal section. An electric plane makes light work of this task, but isn’t essential. Elbow grease and manual tools work just as well, it’s just a lot harder and slower to do. When the octagon has been arrived at, it’s simply a question of progressing to remove the 8 ‘corners’ then the resulting 19 ‘corners’ then the 32 ‘corners’ etc using a jack plane or smoothing plane until you have a rough planed round length of timber. A spokeshave now comes into play to fine finish the shaping before following up with sandpaper. A typical Drascombe main mast is only around 3 in / 75mm diameter, so it’s quite easy to progress from the 8 corners onwards by eye rather than measurement, if the mast is a very big diameter you will need to resort to measurements for the ‘corner’ removals.

To sand a mast from the fine planed finish is very easy, you need to cramp the mast in place resting in the ‘V’blocks using a short piece of wood and a cramp on each ‘V’ block. Select a 4ft length of 60g or 80g sandpaper, uses good quality roll of sandpaper, wrap the sandpaper over the mast and with a backwards and forward motion around the diameter of the mast gradually progress from one end of the mast to the other. Release the cramps and turn the mast approximately 1/3 of a turn, tighten the cramps and repeat the sanding process, then the same again, repeating it until the mast is sanded smooth and round end to end. The next thing to do is sand again with a finer grade of sandpaper 150g to 240g. I wouldn’t advise using any finer grade because you could loose the mechanical adhesion that helps the varnish stay in place. Most other spars can also be made using the same methods as when making the mast, only the dimensions will be different

The easiest way to varnish a mast is to hang some strong string from a garage joist or somewhere similar, with washers tied securely to the lower end. Put a nail or screw in each end of the mast and suspend the mast by placing the nails or screws through the washers. This allows the mast to be rotated easily when varnishing and only leaves a very small hole either end to be filled and touched over with varnish to seal it, the same holes can be re-used when the mast is re-varnished at a later date.

Doug Elliott