Rigging & Sails: Step 1 - Making the Spars
Step 1: Choosing Your Materials
There is alot to be said about choosing the type of materials to be used for both the sails and masts. In deciding on what products to use, it is helpful to consider cost, availability and durability. The main consideration is strength and weight. You want as low a weight as possible while still maintaining a high strength. Due to the small size of the masts - wood or aluminum make great choices, and is our preferred material. However, for serveral years, the Adventure had simple ABS masts, that worked quite well.
In the most traditional sense, wood makes a good material for masts, but it does have some drawbacks. Firstly, spar varnish oftens wears easily and doesn't hold up to weather, for example UV rays break down even the best varnishes and typically if the boat is stored outdoors, it will require constant refinishing (usually once a year). If you paint the wood, with a good marine enamel, this may withstand weathering a little better, but has the drawback of losing some of the aesthitic appeal. Also, of primary importance is weight aloft, the mini-brigantines do not have much ballast below the waterline, and as a result a heavy mast aloft could create trouble! Try to keep it light!
There are different types of wood that can be used, and each has it owns characteristics. The general consensus is that white or Norway pine, Sitka spruce and Douglas fir are the best candidates for spars.
In choosing wood for spars, a greater amount of consideration is given to the weight of the wood, assuming that it is strong enough for the anticipated loads. In the case of the mini-brigantines the "sail load" is very light, and with adequate rigging in place almost any wood would be able to handle reasonable loads. So it is best to find as light as wood as you can. The reason for this is the effect upon the stability of the vessel of topside weights located above the theoretical center of gravity - the more weight and the higher up it is placed in relation to the center of gravity for the entire hull, the more adverse is the effect on transverse stability. Sitka spruce is particularly desirable for spars due to its relative light weight as well as its considerable strength. Though many species are much stronger, a properly crafted mast of quality spruce timber, and supported with adequate stays and shrouds, is amply strong enough for the job, yet lighter than many other species that are equally strong enough. Before the days of carbon fiber and composites, hollow masts were being fashioned of laminated strips of Sitka spruce. This was known as a "birdsmouth mast", where a small notch was cut in each strip to allow it to come together in and 8 or 12 sided polygonal mast. It was then shaved and rounded through planing and sanding. This technique added strength while reducing topside weights at the same time and was probably considered a high-tech method in its time. There is a good article on birdsmouth mast design here: http://www.duckworksmagazine.com/04/s/articles/birdsmouth/
You can also view the birdsmouth mast making process here: http://www.christinedemerchant.com/mast.html
In comparison to Sitka Spruce, Douglas Fir is around 24% stiffer and is 20% stronger than spruce when a spar is bent to the the breaking point. But, it's also 20% heavier. However, you can reduce the diameter of a Douglas Fir spar to the point where it's just as strong as spruce and no more heavy.
In any event, in the case of a small boat you don't necessarily need any "special grade" boat lumber for creating masts and spars. The mini-brigs have relatively short masts (less than 12 feet) and small diameters. The easiest solution we have found to masts, is to find a good quality 2" dia and 8Ft long "Tree Post/Stake" at Lowe's or Home Depot that has been treated. Look for a good straight section that is free of knots or large splits.
Cut the last two foot spike off, only 6ft required for the main part of the mast. Be careful if you decide to sand the rough mast smooth - with treated wood, it is toxic to inhale the sawdust (use of a good particle mask is required). Once smooth, it is possible to fill in the "cracks" with a good epoxy or glue and sand again, and coat with a good quality varnish or shellac. The advantage of pressure treating is that it will not degrade and is less likely to split when wet - the masts have really held up well.
However, if you have the money and prefer a traditional spruce or fir spar, you can contact:
Queen Charlotte Island Boat Lumber
PO Box 293
Port Clements BC V0T 1R0
McClananhan Lumber, Inc. Larry McClananhan
P.O. Box 1483, Forks, WA 98331
Phone: (360) 374-5887 Fax: (360) 374-5800
Pacific Western Timbers
8000 Imperial Way, Port Orchard, WA
However, you would probably do just as well to shop around your local hardware store, look for a good quality piece of timber with as few knots (hopefully none) as possible. You should be be able to find Douglas Fir or Spruce. The finished result can look quite nice and is very durable. begin by laminating 2x3's or 2x4s together, then rip one side on a table saw to get it down to 2x2, and then round the edges.
Our masts are in two sections, a top mast, which is 4ft long and 1 1/2" wide, and the main lower mast whichis 6' by 2" in diameter. For our top masts we used a hardwood. We could not find any spruce or fir in our diameter so we used hemlock, which is also a nice strong wood. The wood is 1 1/2" thick in diameter.
Wooden Main & Top Masts for the Liberte
Cutting the wood to shape - we have (2 ) 1 1/2" x 4' top masts & (2) 2" x 6' main masts.
The next step is to make a platform for the riggingplatform /fighting top to secure to. This is as easy as cutting a 3 1/2 x 3 1/2 piece of 1" x 4" lumber.
We cut a 2" diameter tight fitting hole so they main mast will fit through just fine. It then is caulked/epoxied into place, about 4" from the top of the main mast.
Liberte Main Mast with the 3 1/2" stopper plate
The next step is to cut out the platform/fighting-top. This will also go over the top of the mast, and forms the base for top-mast. We will also make a little simplified maststep for the topmast to slip into, kind of like a socket. Essentially we join the two masts by epoxing and gluing them together.
1) First create the fighting top base from the plans. Cut a 2" diameter hole in the centre. Glue the top-mast step onto the fighting top with epoxy or tightbond III and clamp into place.
2) Glue the top-mast into place by inserting it into the mast step. Place thickened epoxy or caulking between the main-mast and the top mast to help hold it in place
3) Cut out a second wood platform, both holes for the top mast and the main mast and glue into place over the main-mast.
4) Coat the masts in glue and/or epoxy and whip and 1/8" chord around both masts to help secure in place. Liberally apply expoxy and/or glue and let it soak into the chording.
Wooden Main & Top Masts Assembled
We will give it a final once over with about a 60-80 grit sand paper to remove any final imperfections. We will give a light coat of varnish, at this point we dont want to get to heavy with the varnish.
Aluminum masts in dinghies were first seen after the Second World War. They were tried in the development of class dinghies such as the International Moth and the International 14. There was a relatively cheap supply of aluminum standard foil sections from the aerospace industry, which were tried out in these development classes.
At present aluminum masts are the most common for most cruisers and a large number of racing classes. aluminum was used in the 30's for large yachts, such as the J-class "Shamrock V".
The size of the mast that needs to be constructed will largely determine the manufacturing method employed. For simple dinghy masts and small cruisers a standard extruded mast section is commonly employed, these are made by extruding aluminum through a mould. The mast is then chopped to its desired length and the fittings are attached. This is the cheapest form of aluminum mast since it does not require the use of expensive machinery and moulds. The design and manufacturing methods used to make extruded aluminum masts has changed little since the 70's however it is still by far the most popular type of mast that is in use today.
For higher performance and larger masts the same system can be employed, Only that a triangle is cut out of the top of the mast ant the space is bent and welded together. The resulting shape has a tapered top enabling the mast to bend more.
The latest development in aluminum masts is the use of Alustartm. This is an aluminum alloy developed for the marine industry. With a 20% increase in the strength of the alloy over other marine grades the plate thickness used can be reduced, therefore reducing the weight of the mast. It keeps its corrosion resistance, bend ability and weld ability of other aluminum alloys in its group. This alloy is available in plate form with which aluminum plate masts are constructed. These masts are said to be stronger and lighter than extruded aluminum masts, although as yet no comparisons of strength have been found.
You can purchase a custom aluminum mast or look through classifieds and want ads for a used one and then cut the mast to specifications. In this case, we thought the aluminum mast too expensive so we opted for a different method. A good source for aluminum masts may be the used market, for example: older windsurfers. and dinghy's whose hulls have rotted away or suffered damage. The big advantage to aluminum is that it has a strong corrosion resistance, and weathers well.
Carbon Fibre Masts
Carbon masts began to be used in the early 90's, initially in the America's cup and Admirals cup yachts. In the decade since their first use carbon fibre is still not as widely used as one might think.
Using the very latest technology, carbon fibre spars manufacturers bring to the dinghy and yachting world spars that herald a new dawn in the design of production CF rigs. Through the use of carbon fibre a mast can be manufactured which is lighter and stiffer than an aluminum mast. This can significantly improve the performance of the rig. There are 2 main manufacturing methods employed in the construction of a carbon mast. The first is to use a standard section mould to produce a uniform section throughout the length of the mast. This is the cheapest type of carbon mast as the moulds used to make the standard section can be used more than once. They can be built as "one-offs" for a particular yacht. This type is more expensive since a mould has to be constructed to the specifications of the mast, this mould can usually only be used once. The main problem with carbon is the additional cost of the materials and the increased labour involved. A typical carbon mast will be approximately 7 times the cost of an aluminum mast.
Through the use of modern computer technology, such as CFD (computational fluid dynamics) and FEA (Finite element analysis) the precise loads on the mast can be calculated. Therefore a carbon mast can be built with increased strength in the direction of the principle loads. For optimum sail shape the bend of the mast is very important, it flattens the sail, since a carbon mast can be manufactured with precisely controlled orientation of fibres it is possible to create a mast which has the correct bending characteristics. This is an important advance in technology, complement this with new sail technology and they form a superior aerodynamic shape that could ever be achieved with an aluminum mast and polyester sails. The use of CFD can also determine the flow around the mast and on the more powerful programs the interaction of the sails and the standing rigging can also be taken into account.
Carbon fibre is an extremely well suited material for the manufacture of masts. It offers high strength with low weight, complex shapes can be produced and they have also proven to be reliable. There have been problems with carbon masts recently. The development of carbon masts for IACC yachts have shown that when a carbon mast fails (usually due to under engineering the mast or failure of another rig component leading to the failure of the mast) splinters of carbon fibre are produced and can cause harm to the crew or the boat.
The best and least expensive source of carbon fibre masts are ones taken from broken windsurfers and the like. These sections in coastal areas can often be had inexpensively at swap meets.
If you have enough experience you might try making your own:
Similar to the carbon fibre, epoxy and e-glass cloth are layered up on a mold. These are less expensive than the carbon masts but do not have the same strength quality. For our purpose, in the D4 brig, this is suitable enough, again the used market would be a good place to start.
PVC/ABS/Cold Moulded Masts:
This is a method that is not generally endorsed by the boat building community because of the flexibility of PVC and ABS. However, we decided to experiment with this method because of the ease of use and the ability for PVC to fit in the fittings in the boat. It is also inexpensive, and seemed to meet our minimal sail loads just fine.
COLD MOULDING WITH PVC AND LAMINATIONS:
By David N. Goodchild
I was until recently, a crew member of the oldest and largest, wooden, square rigged vessel still sailing on a regular basis in the world today. This is the Gazela of Philadelphia, previously known as the Gazela Primiero. She is a Barkentine of 177' overall, carrying a course, lower topsail, upper topsail and t'gallent on her foremast.
I was already thinking about TOAD in 1988 when we were down-rigging the vessel for the winter, and, while bringing down the yards, (some of which weighed over a ton), and carrying them with many willing hands to their storage yard, it occurred to me that a much lighter and even stronger spar could be built by cold-moulding veneers over an X-frame. Needless to say, the Philadelphia Ship Preservation Guild was not interested in replacing Gazela's spars with cold-moulded versions, and this idea would lay dormant until it came time to think carefully about the rig for TOAD.
I started out with the original idea. I laminated up a 24' long X-member from 1/4" plywood, with the idea of tapering it to the original boat's pole mast dimensions. I first ripped enough yellow pine to make a 24' long 1" square center core. This I dadoed to take the ply. I inserted the 1/4" ply pieces into this dado, cutting the mating ends at an angle to spread the stresses. I let it set up for a couple of days, and then was ready to taper it prior to laminating the veneers.
Here's where I started to become disenchanted with this method. Understand, I am not disenchanted with the method in general, and for another boat it should prove very useful, but I had subsequently decided that I wanted to be able to reef the topmast to reduce the overall mast height to just below 20' in order to pass under most bridges. In addition, it was clear that tapering the X-member was going to prove troublesome.
Something else was needed!
We had recently re-zoned the house to both improve the heating output and reduce oil consumption. In the process, we had re-routed some waste lines and there was some PVC left over and lying around.
If I used the PVC, I could reef the topmast by telescoping it down into the main mast! This I certainly couldn't do with the X-member in place, since it would be in the way. The mast wouldn't be tapered, but I could live with that, especially since I would be able to devise a simple tackle to lower the topmast down into the main mast easily and quickly. Besides, for gaff rig, a non-tapered mast would provide better bearing aloft for the gaff saddle.
I knew that Schedule 40 PVC was strong, since I had used it for the rudder tube, and in testing, it was very clear that the material was tough indeed. It was strong, but in long lengths it was as limp and whippy as a tired Casanova! How to fix that?
Referring back to the rudder tube construction in Part 5, (Building Toad Hall: A 12-Part Series in Messing About in Boats) it will be remembered that I steamed Maple veneer and glued it to the tube with contact cement, since this is the only glue which will adhere to PVC. I planned to use the same method to stiffen up the mast and spars. I knew that after I had laminated several layers of veneer over this first contact-cemented layer, and epoxied it all together I would have a very stiff and strong spar. And this is what developed.
I went to my plumbing supply store and bought a 10 foot length of 1 1/4" Schedule 40 PVC. When I got it home I set up the steam-box. The steam-box is needed, because the 1/16" veneer needs to be steamed first to achieve a close approximation to the diameter of the pipe in the small diameters used for the bowsprit, boom, etc. After it achieves this curve, it is then easy to coat with the cement or epoxy and roll it on to the PVC.
I had previously ordered 500 square feet (their minimum order) of 1/16" Douglas Fir veneers from the Dean Company in Gresham, Oregon. I could have used 1/16" Sitka Spruce, but they only offer short lengths of this and the 1/8" Spruce was a little too thick for easy bending to tight radii. The Fir veneers were beautiful! Absolutely clear with a fine grain and a Douglas Fir mast is certainly traditional!
Building the spars was easy.
It is first necessary to steam the veneers and for this I built a simple steam box out of plywood and 2 X 4's, some 3" smoke pipe and a turkey roaster set over our kitchen gas stove. It is necessary to clamp the steamed veneer around a "mandrel" to allow it to dry to a tight radius and for this I used ABS pipe of the same dimension as the PVC core I planned to use. (Don't use PVC for this; the steam will turn it into a noodle!). After about 20 minutes in the steam box I slid out the veneer a foot or so at a time and clamped it around the mandrel with hose clamps. This I let dry over night. After steaming, clamping and drying a bunch of veneers I was ready for spar building!
I started with the Mizzen Mast. After contact-cementing the first layer, I laminated up the additional layers with epoxy. I used 4 laminations of 1/16" veneer for a total thickness to the mast wall of 7/16". This is consistent with established scantlings for "built" masts of approximately 1/5 of the mast diameter as given in such diverse references as Kinney's Skene's Elements of Yacht Design, Nicholson's Boat Data Book and Buehler's Backyard Boatbuilding. One quarter inch of this mast wall is the veneer and the other 3/16" is the Schedule 40 PVC. This resulted in a mast diameter of 2 1/4". (The dimension of the PVC pipe is I.D., so a 1 1/4" pipe measures 1 5/8" OD, plus an additional 1/4" wall thickness of veneer for a total of 2 1/4 inches OD.). When I had finished the laminations of the mast, it was stiffer than my dinghy mast which was of equivalent dimension but built up in the conventional manner.
I had previously tested out the stiffness of the smaller diameter PVC/veneer combination with excellent results. Even the 1 1/4" PVC could support my weight with just two veneers applied. It bent certainly, but the comparison with the unstiffened PVC was dramatic. Also, the spars were very light, much lighter (and, I think much stronger) than their original solid counterparts.
The photograph above shows the construction, with the four veneers wrapped around the PVC core. I had originally thought that I would have to insert a piece of metal pipe into the PVC in order to stiffen up the flexible pipe so that it would be straight enough to apply the veneers. I found however, that the act of clamping and gluing a cylinder of a single 1/16" veneer around the pipe straightened it up immediately. When finished, the mast was absolutely straight.
The Mizzen Mast is not tapered since the Main Mast is not tapered.
I found another real advantage to this method of spar building; the elimination of the need for so many clamps. In fact, I built the Mizzen mast with one hose clamp (not counting the steam mandrel operation) and a roll of fiberglass-reinforced shipping tape. Here's how:
After the first layer of veneer has been contact cemented to the PVC, the second layer can be epoxied on. Spread your epoxy on either the mast or the curved veneer. (I use a slightly thickened mixture to eliminate too much soaking in to the veneer). Put on a hose clamp at one end about 6" in. Not too tight, just enough to snug the veneer to the underlying layer. (Remember, epoxy loves a gap, hates to be too tight). Wrap a piece of tape around the mast at the end. Move the clamp down further. Put on more tape (about every 6" along the spar). Keep moving the clamp and putting on tape until you get to the other end. Don't worry about the tape sticking to the veneer with the epoxy. It's a polethylene tape and the epoxy will not adhere it. There is a minor bond but it pulls right off. Sand down the epoxy squeeze out (if any) and you are ready for the next layer.
I am very enthusiastic about this method of mast construction. The naked PVC can be bent to 90 degrees without damage, the pipe walls can be compressed in a vise until they touch without damage, and the walls can be repeatedly hammered with a heavy sledge without damage. I know this because I have conducted all of these tests. I very much like the idea of this very tough flexible core living inside a stiff, strong and beautiful outer shell. While I am not an engineer, I feel very strongly that this combination creates a very effective spar. Should the worst happen, it is reassuring to know that there is a mast which, even if the outer veneers are fractured, has a second line of defense in the PVC. It might be whippy, but it will be there!
I had also been concerned about just how I was going to be able to get a good seam upon wrapping the veneers. This also proved simple. By wrapping the veneers around the mast, squeezing it together and marking it, one can run a small block plane down the edge until the edges just meet upon being squeezed around the spar.
TAPERING A MAST
While I chose not to taper this mast because I wanted to telescope the topmast and step the mainmast inside the stub mast tube, it is easy to do and I will do this with the course yard. In fact there are three ways that these cold-moulded masts can be tapered.
One simple means of tapering a spar would be to apply the veneers in ever-shortening lengths. The first layer of veneer, is applied from the heel to the truck. The second layer is applied from the heel to a distance below the truck. Additional layers are applied from the heel to an equal distance below the previous layers. This is simple, but probably not acceptable. A modification of this is to simply sand the ridges where the veneers end. This softens the transitions and this is the procedure I used to make the bolster for the Hounds Band on the Mizzen Mast. I applied three layers of veneer and sanded them to a soft transition as shown in the photograph:
The third method is the one I will use for the Course Yard. Once these first layers are on, (and there would be enough to build up the bunt and the yardarm to their respective design dimensions for the taper), then an additional covering layer is epoxied from the bunt to the yardarm using a thickened epoxy glue for the adhesive. This will result in a nicely tapered yard with a very smooth outer skin. This is shown in the exagerrated drawing.
2nd Method: Creating a PVC/ABS Mast
The other method is to fill the ABS mast with liquid expanding foam. This can be considerably more expnesive than simple wood, but it is a method works very well, and provides lots of stiffness to the ABS and a lightweight mast.
We used ABS masts in the Adventure for several years, before converting to wood.
For the Adventure, we used black ABS, and placed all of our fittings first and then filled it with the foam. The procedure is quick and easy.
Foam (yes, the pour in, two part stuff) or buy several of the cans. You probably will find it more economical to use the two part variety. Once set, it will make the PVC/ABS pipe very rigid, keep it light and permit it to float. The foam will prevent the column from deforming under bending loads. It will work for the same reasons foam core structures are so strong. The walls of the pipe actually change shape while a bending load is applied. This is pretty slight, but a measurable ovalish shape must be made for the pipe to bend. The foam will prevent this from happening.This will also allow you to pass through eletrical cables/wires should you wish to add anchor/spot lights for special effects etc.
Next, after letting the foam dry, we used a good rustoleum paint on the outside to inhibit the breakdown of the plastic by UV rays.
The mast is built in two sections, the first is a 6ft piece of 2" PVC/ABS. At the top of the course mast we placed a 2"- 1 1/2" reducer so we could easily insert the next section, which serves at the top mast. At the reducer, we placed a strong 1/2"-3/4" thick platform of plywood (fighting top/crow's nest), reinforced with 1"x1" crosstrees that run on each side of the mast underneath.
Before gluing the reducer onto the mast, we placed all of the fittings on the main mast and top mast. The reducer is then glued using ABS glue or PVC glue depending on the materials used, and the top mast inserted into the reducer. A hose clamp is placed on the outside for reinforcement. The whole thing is then filled with foam. To date, we have not added EMT but may do so next summer for stiffness. We found that with the stays in place our masts could easily withstand and sail up to 30 knot winds. It is important not to mix and match materials and used the right glue for the job. We used PL Premium adhesive to help secure the "fighting tops" to the mast.
Another method to stiffen the ABS masts:
This last method seems to also work well and it involves cutting two lengths of spruce 2"x2" of 3 1/2 feet and 5 1/2 feet wood respectively. You will need to slightly plane the corners until the wood beam can slide into the PVC sleeve. Simply take the 2"x2" lumber and insert it into the center of the core of the the mast. You will need to do very little planing with the bottom portion of the mast, but the top portion may take some effort.
Then, once the lumber is place in the mast you can secure it with a little bit of epoxy or Lepage's Bulldog grip. Also, you will need to drill through the mast for your fittings and these bolts will also help to hold the lumber in place. This combination PVC/Wood mast seems to work very very well and is our best suggestion if you want to try an easy PVC style of mast.
Use a good rustoleum paint on the outside to inhibit the breakdown of the plastic by UV rays. We have found these masts to be bother vey stiff, inexpensive and light.
The fighting top junction.
The whole mast in place
The yard arms are made from only a slightly thinner diameter timber than the top masts. We use 1 1/4" diameter wood for the yard arms. It is best to use something fairly strong such as oak or hemlock.We have used and seen different methods of attaching the yards to the mast/haliyards depending on the mast construction, and rigging but the basic premise remains the same for most types of masts.
The lower/course yard is fixed, eg.it cannot go up or down. It can however turn leeward or windward. The upper yard is not fixed, that is the topsail yard can move up and down. The first step is to cut the yards to length, the main course is 49" - if you happen to have a piece that is only 48" that is fine.
The Yard pivots on an axle. The axle is comprised of an upside down fence gate hinge, namely the kind used for a wire fence. Normally, this world be clamped around a gatepost. Since the gate is galavnized metal and zinc, it will hold up well to the elements in the boat. The only real modification needed is a small hole so we can put a lynch pin through to hold the yard onto the pin.
This is essentially a pintle and gudgeon system, with the gate hinge serving as our pintle. We place our pintle about 6 inches from the bottom of the fighting top.
The lower yard arm pintle
A piece of metal strapping, made into a gudgeon to attacht the yard. |
A simpler system is to use a small u-bolt.
The yard itsefl then has a gudgeon. We have tried different methods, it seems the best seems to be the use of a small 1/2inch u-bolt that passes through the yard and is capped with brass nuts. Another method is to clamp, a small piece of copper tubing, that serves a bushing for the yard to turn. We found this method to be not as durable as the u-bolt.
The top-mast yardarm is simply attached to the mast by the use of a large u-bolt which wraps around the mast. The ley to the attachment is not to bolt the nuts too tight - you don't need it cinched to the mast. The mast is pulled up via the use of a haylard wich attaches to an eyebolt, that is inserted into the middle of the yard.