Allow me to add some verified numbers to this discussion :




Currently the Capricorn F18 and Viper F16 rudder stocks are solid cast aluminium. This is not a lightweight or indeed strong construction at all unless AHPC heat treats the stocks after casting which is doubtfull in my opinion. AHPC, Falcon marine and Stealth Marine have all offered carbon rudder stocks while Blade Europe offers (standard) stocks made from bend high grade (heat treated) square aluminium tube. All these come in at around 0.500 kg when fully assembled (excl. the rudder boards). The F16 rudderboards are typically around 1.0 kg making the combined package 1.5 kg per side. Indeed, measuring different brands of F16 didn't show much variation here. Note how the F18 class rules state ;"The minimum weight of each complete rudder assembly comprising blade, stock and tiller is fixed at 3 kg." That means that a standard F16 build already saves AT MINIMUM 3 kg in total on the rudder assembly. Please note that breakage of stocks and rudderoards is not at all common in the F16 class, so these standard lightweight setups appears to be up to the job.

Sailfast quotes his Capricorn set of daggers and ruddersetup to be 12.63 kg. At GC 2007 we measured the Viper set at almost 15 kg on total. Either way the Viper daggers appear to be at minimum 12.63 - 6.0 kg = 6.63 kg per pair. Standard lightweight F16 daggers (high aspect) are below 2.0 kg a piece. I think we measured these at GC 2007 to be between 1.6 and 2.0 kg; with the Stealth daggers and newest Blade daggers being lightest at 1.6 kg. Only mine and I think the prototype Aussie Blade daggers were at 2.0 kg (please correct me Marcus if I'm wrong), none were over 2.0 kg. Most others were at 1.8 kg. That suggests that another 6.0 - 2*1.8 = 2.4 kg can be won on the daggers.

Combined this comes out at an minmal estimate of 5.4 kg gains simply by not using (overweight) F18 technology. Basically, in the F18 you are trying to get UP to weight instead of getting DOWN to it. Note however, that the only measurement I have of a full Viper set (GC 2007) is 15 kg compared to my own "back of the pack" 7.2 kg. That is not a difference of 5.4 kg but rather of 7.8 kg !




I actually don't see much data to suggest that. At least the Viper daggers I held were pretty much in the same weight range of the F18 boards I helped carry. I think it perfectly reasonable to expect the exact same layup to be used for both the Viper and Capricorn boards. That would be economically smart. Do you have measurements that contradict this ? How much do the "new Viper daggers" weight ?




We have done platform stiffness measurements on the F16's and interestingly enough ; all new builds are stiffer then the Tiger F18's and Nacra F18's ever were, even when compensated for the different platform weights. There is a point were platform stiffnes is enough. One can always go stiffer still, but it is doubtful whether that improves handling or performance by any significant measure. By laying up the bare platform on the sterns and lifting one hulls one can measure the height distance between both bows. My homebuild Taipan with relatively flexible beams show a height difference of 62 mm. The home build Blades with 80x2 mm beams display about 43 mm and the newer F16's (with custom beams or 90x2 mm) are around 25 mm if I remember correctly. The Tiger and Nacra F18's were measured at 95 mm. Please note that the F16 platform weight (65 kg) is exactly half the platform weight of an F18 (130 kg). This means that the homebuild (timber/epoxy/80x2) Blades were already on a par with competitive F18's and the newer F16's are better. I don't think anybody marks a 2002 Tiger as an uncompetitive F18.

I'm quite sure that the Viper F16's are somewhere around 15 mm flexing in platform stiffness. However the relatively weak 80x2 alu tubes are already enough. The 80x2 beams weight 3.5 kg a piece. What do the Capricorn beams weight; If I have to guess I would say twice as much. However does anybody have a measurement of these ? The newer F16's like the Aussie Blade and Falcons use a custom designed aluminium beam setup (Phill and I designed it together). These are a little heavier then the 80x2 beams, from memory 4.5 kg a piece, but have the same stiffness as 90x2 beams (40% better then 80x2) while presenting a more practical overall shape (straight top, bottom and back sides) and having an integrated trampoline track. Of course a custom die had to be made to produce these beams, but that was only a minor portion of the total price it would have costed to produce a single batch of 80x2 or 90x2 round beams. What I'm trying to say here is that it is not expensive to make custom aluminium beams for a F16. Any builder who doesn't have a F18 in its program will go down this route over using standardized 80x2 or 90x2 round tubes. And indeed small builders (compared to AHPC) like Australian Formula Catamarans (FCA) and Falcon Marine have gone down this route. F18 builders on the other hand will take another route as they are trying to get UP to weight. They will make one heavy and stiff beam design with an integrated trampoline track and an integrated traveller track. The latter adds another 1.25 kg to the beam. As weight is not an issue they use the same beam both at the front and back. Some builders are also foolish enough to place the trampoline track in the centre plane of the beam where it does add weight but hardly any stiffness.

It is indeed a far cry to claim that such F18 beams are a benchmark. One now also understands why F16's don't use beams with integrated traveller tracks. A seperate track of 2 mtr length riveted to the rearbeam weights 1 kg while an integrated track to both beams (2 * 2.50 mtr where 2.50 mtr track = 1.25kg) adds 2.5 kg weight to the whole platform. That is an easy 1.5 kg to save. So someone has to fit the traveller track to an F16 beam; that is some additional labour cost, but won't run up in 1000's of additional dollars. Maybe 50 bucks extra ? I would call that cheap weightsaving.

All these little weight increases do add up (to a 180 kg F18 !) and I dare say there is ample evidence that the beams, daggers and ruddersetup alone already add 10 kg at minimum to the Viper overall weight, probably a little more. Note that the lightweight F16's do not report troubles with their beams. In fact, the VWM Blades came with 90x1.6 kg rearbeams (0.5 kg lighter then 80x2 and 15% stiffer) and I believe there was only single one report of malfunction there, thus suggesting an extrusion error rather then a design error.

Wrapping up this particular point. MUCH lighter beams could have been used for the Viper F16 while maintaining sufficient platform stiffness; at least at such a level as to be on a par or better then a competive F18 design.




Actually, this is only said by the people closely associated to the Viper F16 design. In fact, even mr Gooddall himself admits to the fact that the basic Taipan F16 (4.9 with a spi) is right at the minimum class weight (without ANY use of exotic materials like carbon). And one more then one occasion he mentioned to me that he feels that it is still a surprisingly competitive craft especially in 1-up mode. Now, he has a point in saying that the newer 2-up F16's have become significantly bigger boats, but that still doesn't negate the fact that going up from 107 kg to 130 kg is one major increase in overall weight. After all, the only items that needed to be beefed up were the beams and hulls; one doesn't need 23 kg to do that. Note that a 10% increase in hull crosssection dimensions (weight) already incurrs a 21% increase in hull volume. The Taipan hulls come in at 23.5 kg. Basically, this means that a 26 kg hull that is build with Taipan 4.9 technology can have 25% more hull volume for only 2 * 2.5 = 5 kg more ready to sail weight; and 25% additional volume is a major increase (think boat+crew = 107+135kg going up to 112+190kg).

Upgrading from 80x2 to 10x2 beam (or equivalent stiffness beams) will cost an additional 1.7 kg per set = say 2.0 kg or less for an increase of 95% increase in beam stiffness = say doubling the beam stiffness.

Now the readers will also understand why the competition (who also makes economical decisions in constructing these F16's) are able to produce wide bodied and stiff glass/vinylester/alu boats that in their basic standard 2-up fit-out weight in the range of 110-115 kg. (This is confirmed by actual GC measurements). So yes, the claims are correct in principle, just not in the actual amount of weight that needs to be added.

Now imagine placing a (3800 USD / 3000 Euro) carbon mast on such a standard boat (typically 16.000 USD / 15.000 Euro); this will already lower the ready-to-sail weight to the range 106-111 kg and put the cost price on a par with a modern competitive F18. Also note that the all carbon Stealth F16 is priced some 2000 Euro below that figure. Additionally, the reduced weight of the rig will lower the demands placed on the bow volume again, thus allow smaller hull volumes to be used again.

Can anyone imagine sailing such a standard Falcon or Aussie Blade F16 with a carbon mast ? I think it would be a dream to sail and be THE benchmark against which all other designs will be compared. I think some Stealth owners are one step ahead of us in that respect.





Actually, the claim of costing more then a N20 carbon is rediculous itself. Indeed, EU en US customers can already buy a close to minimum weight carbon masted F16 for the same price as they can buy an alu masted F18 like the Capricorn for (under 20.000 USD / under 18.000 Euro's). Hell the last quote for a carbon masted Inter-17 was significantly higher then that, not to mention the cost associated with the new Hobie iCat. The Hobie FX-one with an alu mast and no jib or spinnaker will set you back 14.500 Euro's. Even the sloop+spi alu masted 149 kg heavy Cirrus Evolution will cost 15.000 Euro's. http://www.boulogneconceptionmarine.com/fr/catamarans-fiche.asp?IdProduit=3

It is a strange world indeed when a 110-115 kg STANDARD F16 is ACTUALLY both cheaper and faster then its 130-150 kg competition. Additionally, it also has a much more developped international class stucture.



I'm sure somebody will some day construct an all carbon fibre F16, possibly with diamonds inlays on the deck. Some desert Sjeik may find that attractive. However, it will not gain more then 4 kg on a 20.000 USD/18.000 Euro carbon masted F16 that is available of the shelf today (most likely less then that). It will not gain much platform stiffness as he is NOT allowed the glue the carbon beams to the hulls and therefor has to use the old bolt and nuts fastenings that negate much of the stiffness gains. As a result he will not be faster at all then the above mentioned cheap F16 and he will look like a right fool when Robbie Daniels passes him on a standard all glass/alu/130kg Viper.

I feel we must give the customer and class member some credit here. They will know perfectly well what an acceptable ratio is between cost and performance and will rightly ignore over expensive F16's that may look good on paper but not live up to the promise. I don't think any customer is in the slightest attracted to a 30.000 US/25.000 Euro F16 when it promises to only improve weight by a mere 4 kg and platform stiffness by a mere 10 mm ( modern A-cat 15 mm; modern standard F16 25 mm). He or she will know that that is just wasted money.

And why do I think that ? Because the Viper design is selling at the moment (just as the other F16 designs are) implying that its customers are not too worried about its 15-20 kg additional weight. If so then why do we expect them to worry about a mere 4 kg ? They don't and they won't.

With kind regards,

Wouter