Home Made Carbon Masts

Various home builders have asked for help building their own masts. Obviously, there is a wide range of techniques the professional mast builders use and for the budget builder the costs and the risks need to be carefully thought out indeed. Insurance of your finished boat is a topic in itself. Assuming that you have covered all the bases and want to do it yourself then you need to cover the basics. Here are some rough rules of thumb given in good faith with no warranty of any kind. Find an alloy mast extrusion which you know is safe and conservative and recommended by the yacht designer. This establishes a section size and wall thickness. Your carbon mast will be the same size and same wall thickness! It should be a tad stiffer made in carbon and it should be a lot lighter too. This is a very simple approach to avoid [evade?] doing the job professionally. Next step is a laminate, normally 1000gsm of carbon will laminate up to be about 1mm thick. So, if your mast is 3mm thick in alloy, then you need 3000 gsm of carbon. Carbon normally comes as 300gsm unidirectional, 200 gsm woven cloth 0/90 degrees, and double bias which is 400 gsm plus and minus 45 degrees. In general, the rule of thumb is that you use 60% of the laminate as a zero degree fibre, 30% 45's, and 10% at 90 degrees. Next you need to have it balanced so that inside and outside plies are the same as each other, Next you need to try to distribute the 45 and 90 plies through the laminate. Generally, you start and finish with a 200gsm woven cloth because it is easier to drill and cut holes in the mast afterward if this is the ply on the surface. Given that you use the plain weave inside and out then you add the others as you need them to get near to 60/30/10 mark whilst keeping the laminate balanced and evenly distributed as possible. The double bias 45 is normally quite expensive if available at all. it is possible to make the mast entirely from unidirectional and this is often done. But keeping the outside and inside plies in plain weave cloth is recommended even if you use glass plainweave in order to save money and you don't included the glass in your percentage figures. If the mast needs stiffening in some areas, you can add extra unidirectional locally to go up to 80% unidirectional. Conversely, if you have a lot of holes at deck/spreaders/stays then you might be wise to wrap the finished mast in some triaxial to really boost the off axis content in those areas, in addition to adding compensation patches to make up for the holes themselves. Masts that have long swept spreaders will sometimes need more 45 fibres (plus/minus) since alloy masts are in general far stiffer in torsion than carbon ones. Hopefully I have not confused you. There are some other issues to be wary off, and I hesitate to try to write a full design manual, but in particular local buckling can happen if the wall is thin/flat, but if the alloy mast extrusion you are targetting is NOT extreme, then all should be fine. Obviously if your mast is small the costs and risks are low and if it breaks you can stick it back together and add more carbon next time too. If on the other hand the boat is big the costs are large, the risks are large and the relative cost of professional engineering from AES or any of the other design professionals is relatively low by comparison to the cost of getting it badly wrong. Yes, I know the Titanic was designed by professionals, but a number of people have misjudged the work involved in building a carbon mast and with hindsight have wished they had thought it out better. So, research the whole thing thoroughly from every angle before you start and then it will either go very well or you wont attempt it at all. Both of those two outcomes are fine if they result in many years of trouble free sailing where everyone has a great time.

Finally, a confession, I don't strictly practise all that I preach, it takes a little interpretation. I sail a Farr 3.7 and my current boat has rather an old carbon mast homebuilt by one of the former owners, at least three owners prior to me. The entire boat cost NZD 2000 (bottom of the range and good for a learner). The mast is made from several windsurfer masts in the 80's era. This mast has clearly broken before I owned it, to date it has broken three times in my tenure, not solely due to operator error; but mostly. The mast has never broken at the same place twice (so far) and is developing a patchwork-quilt look... Having sleeved and joined it back together three times, including coving on a whole new bolt rope groove once, it has to be said that repairing a carbon mast is much easier than repairing a broken aluminium mast and I am getting quite good at it. I race once a fortnight and it takes one week of lunch-times to effect a repair to a big break. Working for AC teams (mostly NZ) various masts have broken, thankfully mostly in training mishaps. In each case the teams have not had insurance (it is not realistic for this kind of operation) and in each case the mast was repaired with almost zero weight increase or change in performance characteristics. A lot of prattle is spoken over the yacht club bars of the world about this sort of thing. The truth is that it is cheaper, faster and better to repair a broken mast nine times out of ten, assuming the mast was basically fit for its purpose. Owners and insurance assessors tend bring along a lot of baggage when negotiating over this kind of problem. All that said, my own dinghy mast is a bit of a poor example, and should be put out of its misery; I only keep repairing that one out of interest: a bit like a 'cat playing with a mouse'. If you enjoy your sailing and you enjoy experimenting with your rig, go for it. Best advice I can give you is to choose a boat/class where the costs are within your 'leisure budget', that is to say, DO NOT buy a boat that you can't afford to actually have fun with because you paid so much for it that you daren't spend any more on it or because you are afraid to break it. Buy a boat that costs only half of what you wanted to spend, and don't spend the other half unless you can make a genuine case for its improvement.

Cathedral Rigs

The Whitbread 60 rules included a strange rule regarding the top mast stays. Our office was working for the Swedish Match Team and developed the so-called cathedral rig to get around the (rather silly) rule requirements trying to enforce jumpers. This cathedral rig configuration was then IMMEDIATELY adopted by all the big teams re-rigging their new masts regardless of the expense (Merit/Dalton) being the first to see it were the first to change. The Volvo then followed this..

Lattice booms

The AC booms (circa 2000) were reasonably deep and the shear requirements for the side walls are quite low compared to the lightest weights of uni you can buy and this needs careful use of core even then, to make it work right. So, the lattice booms developed by us for the 2003 Team NZ campaign made a weight saving by eliminating the core, glue film to attach the core and by eliminating much of the excess side wall laminate weight too. The downside was that we had a few break while we figured it out, and the pipes need fittings made at the corners, the upside was that they were really really cheap using high quality pipes made by Kilwell and not forgetting the drive and professionalism of Nev, Taro and the 2003 shore team to put them together. In the 2007 campaign almost every team had copied this innovation to some degree and some with considerable style as well. Imitation being the most sincere form of flattery, we were stoked.

One day I should write about twin rigging, triangular poles, X rigs and pushers and maybe even the simplest engineering structure on the boat.

Rules like the AC Rule

These rulemakers and measurers 'we' have keep writing rules in the mis-guided attempts to keep the costs of the AC (or volvo or whatever you want to enter here). The truth is that the fundraisers raise as much money as they can, the "expense" of the Class is used as a lever to obtain more money and the real costs are in getting around the rules to spend it. So, having raised as much money as one can, then one spends it the best way (one can) to get the fastest boat. Making the keel/hull out of cheap lead/carbon instead of expensive lead/carbon or some other such rule will simply leave more of the money for figuring out how to make a lead/carbon right on the edge of the rule. Thus the endlessly growing complexity of the rules is GREAT for engineers (innovators) because we're kept fully employed looking for ways forwards in a highly constrained albeit contrived design space. It also keeps the rule makers and measurers fully employed, and guess what, they need paying too. Nobody ever has explained to me how a 1992 AC boat was cheaper than a 12 metre. I suspect that 90 footers wont be cheaper either. By bringing in various other rules (window dressing) we are told this saves money. Does this mean that money is then returned to sponsors such as emirates or BMW? I don't think so. Does this mean that total campaign budgets will drop and that teams will ask for less money? I doubt it. Well how, exactly, is it saved then? Does it get donated to charities, maybe a tiny bit did (out of the PR budget), but that happened regardless. The cost of a campaign is certainly enormous and the smaller teams without the big bucks have been shown to be inadequate. But the teams that manage to raise the big money will always be fastest, have the best design and sailing talent and WHATEVER is the rule they will move heaven and earth to beat it (and we will be doing a great job of helping). Unless you can find a way of limiting the dollars with a budget cap (various sports try to do this) you just aren't going to get there with the rules. Generally the team with the most money and the most control of the rules is the team that just won it. So, don't expect them to throw away this advantage. Does this technology trickle down to mainstream yachting? Well, thanks to the totally distorted rules that outlaw any sensible improvement and create weird stuff instead, the amount of trickle down is a tiny fraction of what it should be, because it is impossible to apply to a normal boat. If the rule was 70 feet long, with a monohull and some practical limits on beam and draft then it is hard to say where it would all end up. It would certainly be very frightening, to begin with. The only AC team I have ever worked with on this basis was the 1988 big boat challenge (90 foot waterline 21' draft etc). This boat was very much in the spirit of the Cup. I personally liked and admired the Connor catamaran, but I would never have entered a catamaran in that event based on what I think the event stands for. I think a 70 foot version of 'limits' in the same style as the 1988 K boat would be the way to go. I am sure all the measurers are really very knowledgable yacht designers and could in fact find other useful employment as such. Instead of the negative rule beating approach, we could develop a postive make it faster approach. The current owners of the cup are going to create a new rule with Tom Schackenberg in charge (at time of writing), it has to be pointed out he too was a major player in the K Boat design for Michael Fay in 1988.