Okay, call me argumentative (what I am) but I just love to react to this :
We have found over several years that carbon masts are the equal, or in most ways superior, to aluminium.
Shouldn't this read "Can be superior" over "are superior" ?
I've seen my share of carbon duds. The fact that a certain technology has the potential to be better doesn't mean that it actually is better in its implementation.
One great example are the Taipans. There was a test platform of a Taipan 4.9 in 2000 with a Saarberg Carbon mast and a Goodall mainsail. This combo proved to be way inferiour then the old alu mast and mainsail. Mast was way to stiff for the sail while the old combo (alu) had over 10 years of development on it done.
Like with every new technology; it needs a good time of development (trail and error) to realize its theoretical potential. I personally see carbon masts in F16 as in their initial stages while the alu mast rig has now seen over 15 years of development by some very skilled sailmakers. You are not going to beat that alu development with the first series of carbon masts. In the future you may; but not straight away.
The UV that is often talked about is a “non event” as all carbon masts are coated with clear polyurethane before use (or should be) this totally eliminates any possibility of UV damage.
Were I am we keep the boats on the beach for 6 months. A couple of spring/autum sandstorms can do wonders with this protection layer. Once it is gone it is downhill. Correct me if I'm wrong but I think carbon mast owners overhere do repaint/recoat their masts every so and so period. In theory Darryll is correct but in practice some other happenings may well impact on it.
The “strength” of a carbon mast is in all ways better in practice, than aluminium, other than direct impact. Though in a direct impact situation a carbon mast can “break” whereas given the same impact on an aluminium mast, it will most times “bend” to the point that there is a fold or crimp on one wall, which generally leaves that mast beyond satisfactory repair.
For one thing the alu superwing mast is one the most resistant masts I have ever seen. See other posts. It think carbon replacements need first proof that they can be better then that. I'm unwilling to conclude that they are just by looking at a single material property number. In addition, carbon much stonger than aluminium in a direct sense. It is alot stiffer and lighter by direct comparison and this means that carbon layup can by alot stronger PER GIVEN WEIGHT and stiffer. Most most equate this "stronger per given weigth" to just "stronger", but this is incorrect and can even be deceiving. The stiffness is not all together an advantage either.
For a mast sail combo to be trimmable, a big necessity on catamarans, the bending of the mast is needed to flatten the mainsail or to have the top bend away. With the stiffness of carbon this is directly impeded. The solution is to make carbon masts with a smaller cross section and thinner walls. The direct side effect of this is that the mast is intentionally put under higher stresses to result in more bending and thus the mast as a whole will be weaker then it could be when looking at the material properties themselfs.
In addition stiff materials really do not like sudden changes in loads. Many will call this impact. For a while there A-cat carbon masts would break when capsizing the boat at anything but very low speeds. The stiffness of the carbon prevented the mast from bending with the shock load like aluminium and taking the real punch out of the blow.
In my experience, and I really shocked a few alu masts in my past, The alu mast will takes any load, capsize or general shock load without bending. The elasticity of the superwind masts is such that they can bend really really far before permanently bend themselfs.
I have repaired an alu mast myself that was dented after a storm blew my over and it hit a gate with its upper part. It took out a big dent and afterwards tried to take out some small remaining curve in the top. Let me tell you we started out really gentle but quickly we had two adults bobbing up and down one the end of the mast with their full weight to get it to deform. The mast was bending by nearly 30 degrees downward, which is ALOT when you see it. So I really don't agree with "it will most times “bend”"
A broken carbon mast can be re joined without any major dramas, if you are familiar with the correct procedures.
That is true, with aluminium you buy a new one. The fact that an Alu superwing mast can be had for less then 1000 Euro's will make this still cheaper then repairing a carbon mast that costed 3000 Euro's whne it was new. In fact I can break 3 alu masts before even arriving at the price that it would have costed me to get the first carbon mast. I'm still on my first alu mast though and in 9 years of sailing/racing catamarans I haven't broken a single alu mast.
An aluminium mast will “corroded” quite badly in any area where there are concentrations of alkali’s and/or acids in the atmosphere (even if the aluminium has been anodised to 35 microns, and not to mention “electrolysis”)
Like I said my Prindle 16 had a 30 year old alu mast and race halve the time in 15 + knots winds.
whereas the carbon is unaffected, and there is the obvious advantage of the carbon, by being a “stronger” material, it can be made appreciably lighter than the same profile mast in aluminium.
This is not a durability issue. Also carbon mast NEEDS to be lighter as otherwise the mast will be FAR too stiff or the crosssection will be far to small.
As a “moulded” or “spun” profile, the carbon can be strengthened or lightened wherever it is desired (personally tailored), an advantage that is extremely difficult to accomplish in aluminium.
This propertie is as good as impossible with aluminium. However this is also not a durability issue. In addition it takes quite well developped engineering skills to realize this potential into reality. I refer again to the case of the carbon masted taipan 4.9. The fact that this can be done doesn't mean that it will be done in reality. As far as I know even A-cat masts are only offered in three categories : flexible, medium and stiff. Correct me if I'm wrong but it is either too expensive or impractical to offer more variations. Get the wrong one for your crew and you are worse off or you'll have to have you mainsail recut to correct for it. Naturally, the last action can also be taken to correct a standard alu mast to your crew weight. With this the question becomes ; how much additional effect can be expected from a carbon mast, and is that worse an additional 2000 Euro's to you ?
To our way of thinking the improvement of a carbon mast over an aluminium one is about the same as the improvement of an aluminium mast over a timber one. Its simply, new technology versus old.
Great one-liner but I'm sorry to say that I can't underline this statement. The major difference between timber and alu was that more general shapes and improved shapes were possible with alu then with the old techniques used for timber. This difference is not really present in the comparison with alu to carbon and so the difference between the latter two is alot smaller then the first two. In addition glue techniques have allowed timber masts to catch up again, something many are forgetting. Right now it is possible to make shaped and hollow timber masts using strips or plancks and glue. These are then routed into shape. They are quite lightweight and the bending characteritics can be engineered to quite a decent level.
Biggest advantage of aluminium was of course the costeffectiveness of production. A anodised extruded section can be had for such a small amount of money that the labour intensive timber mast production was simply not viable anymore. We musn't allow ourselfs to think that everything is driven by advances in performance.
Wouter
