I compiled the questions concerning the Viper from this forum and forwarded them to AHPC. Here is Gregg's comments. The questions are listed and Gregg's answers follow each question. Some interesting reading (IMO). I just thought the questions deserved an answer .

Bob Klein
Taipan 262


Q: Now that they're in production, how much does the viper weigh?
A: The Viper weighs all up 125kg. This is with an alloy mast. The Viper is a much bigger boat than either the Taipan or the Blade. A sloop Taipan with spinnaker weighs in at about 110kg. At the Global Challenge the average weight of the Blades, sloop with spin was 118kg. The lightest was, I believe, 112kg.
--The Viper is designed to be 125kg with a crew weight of 120 – 140 kg. The hull buoyancy and shape is designed around this.
--The Viper is designed to carry the crew on trapeze with spinnaker. The Taipan and Blade struggle to do this in anything over moderate conditions.
--The Viper does not appear to suffer from the extra few kilos even in light winds as the hull buoyancy is designed to carry the weight. If the boat was underpowered either up wind or down wind then there would be a problem. The F16 has power to burn; it is more of a problem of being able to harness the power and in particular how hard the boat can be pushed down wind. The Viper can be pushed a lot harder than any other F16 currently available.

Q: I notice the spin trimming blocks on the hulls are well inboard. Must be running a much flatter spinnaker. Is this correct?
A: The spinnaker is a flatter than earlier Taipan spinnakers and is fractionally flatter than our F18 spinnakers. The spin blocks are on the inner gunwale, the same as on all F18’s and the Tornado. Sheeting to the side stay is simply too wide for best performance.

Q: Any inside scoop on how much help the extra hull volume offers in higher wind strengths?
A: The Viper has about 50% more hull volume of the Taipan and about 20% more than the Blade. Does it make a difference? - heaps

Q: Have all the "pieces" been optimized to the F16 (alluding to the F18 parts used at the GC that were intended to be re-made for F16)?
A: Yes, The list of optimized things where we have saved some weight since the 1st boat at the GC are;
--Hulls now 26kg (-4kg)
--Front beam assembly -1.3kg
--Centerboards -1.2kg each
--Rudders -.2kg each
--Mainsheet system. -.6 kg
---Total 12.7kg
This has reduced the weight from 137kg to 125kg

Q: Any delivery dates for US buyers?
A: First boat into the US will arrive early December.

Q: where are the spin sheets led? Is that the yellow line I take it? Why so inboard with the sheeting? (if those are them, but there are no other blocks around)
A: Spin sheets go to ratchet blocks on the inner gunwale - then to turning blocks on the front beam. The turning blocks are positioned so that the crew on trapeze at the back of the boat can easily sheet past the skippers head. It also gives more angle of the sheet around the ratchet blocks.

Q: I'm also curious about volume distribution along the length of the hulls. Hard to get a clear idea from the photos but it seems as if there might be comparatively more volume further aft compared to the Blade.
A: In fact the buoyancy distribution is possibly a little further forward than the Blade but I have not really compared them. The transom on the Viper is smaller than the Blade and helps considerably with the downwind performance of the Viper. With the little bit of racing that we have done with the Viper it is proving to be every bit as good as hoped.

Hope this helps,

Regards,
Greg

Greg Goodall
Managing Director
Australian High Performance Catamarans

There must be some correction on one answer. The average weight of the Blades measured during the Global Challenge is not 118 kg but 114.3 kg.

The lightest boat was carrying a carbon mast and weight 105.8 kg and the lightest one with alu mast was 109.8 kg.

All latest models Blades (2007) are around ( +/- 1 kg ) around 110 kg.

Regards,
Hans

I also believe John A was twin stringing down wind at the GC, how does the Viper compare to the Stealth F16 which must (I assume) have the best "manners" down hill with T fouls ?

Very interesting answers Bob. It would also be interesting to know (not that I expect you'd get this from Greg) how the 15kg difference between the Blade and Viper is distributed between hulls, beams etc. And it will be great if we can get both (or better, all) of the designs racing each other regularly. Really quite a step forward in the development of the class.

Interesting weight zone, it seems to be in no mans land, most blokes I know are with sailing trim around the 75 -85 kilos which then means that only your son or daughter is really optimum crew. With the extra bouyancy and modern hull design I guess its not really going to matter but I think as a single hander it maybe a bit porky in the lighter stuff, I guess one shouldn't make assumptions just yet

Good comment (especially since I'm feeling a little porky myself right now :-)). Does this suggest that the Blade may be a little better suited to a heavier crew, essentially trading some of the Viper's boat weight?

I suspect targeting that crew weight is intended to try to differentiate the boat clearly from the Capricorn rather than risk cannibalizing his existing market.

That seems counter intuitive as the Viper has so much more volume in the hulls. I'm also wondering is the Viper more difficult to right?

Personally I like the AHPC Viper F16. I would have written "really like" if it had been lighter.

Bob has send me some more pictures of the Viper and I will post these shortly.

I think it is a very clean looking boat and I think it has the right amount of bow height for very challenging conditions.

The thing that I don't like very much is how somebody consistantly misremembers some important specifications and averages. Hans has already responded to that, as have several others over the past year. I also don't appreciate it very much when Greg says that the Viper is a much bigger boat then the others, because it isn't. The Aussie Blade is the same size (volume) and that boat was measured at 111.7 kg if I remember correctly. And we must note that this Aussie Blade was a prototype as well ! That 137-112 = 25 kg wasn't therefor so much the result being "bigger" but more of different design choices.

When Greg wasn't looking we, the GC participants, had some fun with the electronic scales and various Viper components. Two daggerboards, 2 rudders and rudderstocks on the Viper were already 8+ kg heavier then the same package on the other boats. Certainly, the parts were said to be off the F18. But still.




Notice how this leads to the following situation :

boat weight + max crew = 125 + 140 kg = 265 kg

Were the other F16's will have :

110 + 155 kg = 265 kg

Basically what AHPC has done was to take out any excess weight of the Viper itself from the maximal competitive crew weight. The final overall weight remained the same.




Personally I believe both the Taipan and Blade struggle a whole lot more when you don't send the crew on the wire when sailing under spinnaker in challenging conditions. I found that having the crew sit next to the skipper puts to much weight forward on the boat.

It does appear however that the taller bows improve the downwind ride.





Well yes. That and the fact that the competitive crew weight range has been corrected to arrive back at the same overall weight. With that being exactly the same together with having exactly the same rig then yes, light wind performance would indeed be expected to be identical.





This is simply not true. Both the Stealth and the Aussie Blade has at least the same quality as the Viper, were I believe that the Stealth is still the undisputed winner with its T-foils.





Most of this volume is above the waterline and in a place where it can not be used effectively. This is because it is largely the result of having a taller hull all over and for example the additional volume between the beams will not be doing anything no matter how rought the conditions.

More important then overall volume is for example that the bows are taller.





It will be interesting to note here that the Blade hulls are now about 23 kg. The Taipan hulls were 23.5 kg. The home build Timber blade hulls come out at 25-26 kg. This shows that most of the difference in ready to sail weight (= 125-107 kg = 18 kg) is not coming from the hulls (total 6 kg) But from other components. Again this confirms the earlier claim that weight differences are not the reasult of the Viper "being bigger" but of having made different design choices.

The daggerboards at the GC were measured at 8.0 kg per pair exactly. With the savings as mentioned by Greg we now have 5.6 kg per pair. The pair of Stealth daggerboards were 3.6 kg, the 2007 VWM Blade pair are 3.8 kg, mine Taipan set is 4.1 kg and I seem to remember that the Aussie Blade pair was 4.8 kg. The latter was a prototype set and Marcus was adament that they would be lighter in the production version.

With respect to rudders. We measured them at just over 7 kg at the GC. With the weight savings we now have 6.6 kg. My own AHPC rudder setup (2 rudders and 2 carbon rudder stocks) weights in at 3.1 kg. It is true that the Viper uses aluminium rudders stocks and therefor we can't compare them directly to the my carbon stocks. Both rudder boards do use carbon cloth as stiffening however. Still, the European Blades are fitted with aluminiun stocks as well, made from bend alu tubes, and this are surprisingly light. I haven't measured them but when I held them I could not feel any difference in weight. I'm told that the stocks from bend alu tubing weight almost the same as the carbon stocks I have and it sure felt that way. I'm also certain that I would have noticed any difference over 0.5 kg, mostly because board+stock only weight 1.55 kg and then 0.5 kg different is quite alot.

I don't think the current run of F16 boards and rudders (stocks) are considered anything other but up to the job. So the added weight is not to prevent any breakages as none are occuring now. Looking just at the rudders (stocks) and daggerboards we see that already another 5 kg can be won.

I'm sure the beams themselves are combined at least 6-8 kg heavier as well. Maybe even more. That results in an extremely stiff platform but it does cost a bundle in the weight department.

And that shows my earlier point about making different design choices.


Now I reiterate that I really do like the Viper F16. And I agree with Greg that the performance difference between a 110 kg F16 and the 125 kg Viper F16 will not be much at all. Even Texel only predicts a 59 second difference after an hour of racing because of it (assume both are raced with 150 kg crews). When the Viper crew is 15 kg lighter then the other crew then the difference will be less still.

Personally I feel that the Viper F16 has everything done right except the overall weight. But that is still very acceptable. I do understand the reasons why AHPC choose the go this route, using the same beams for the F18 and the F16 is economically attractive. What I don't understand is their choice to have different boards and rudders for the F16 and then still have them at F18 weight. Again AHPC has been making much superior boards and rudders for nearly 20 years now, surely they can get the result they're after by being only 1 kg overweight instead of 3 kg ? With the lighter boards and rudders the Viper F16 will come out at 120 kg is just under it and then, indeed, it will become an attractive F16.

That is the way I feel about it.

Wouter

Wouter, did you know that the Viper from the GC is sitting at my club? (Muiderzand).
I've seen them take it out at least once, you could probably even take it for a spin if you asked real nicely.

I may just do that !

I will ask nicely of course, but I will not make any deals regarding my review.

They must accept that I will give my honest appreciation of it, where ever that may lead. That is paramount.

I do expect however to be positive about the Viper however. I've sailed some of the other F16's while heavily overweight (3 persons on boards or two heavy weights) and these boat never failed to surprise me about about how well they keep going. My record for the Taipan is 210 kg (crew), with my own homebuild F16 being 121.8 kg that puts my personal overall weight record at 330+ kg.

Thanks Tony,

Wouter

Thanks Wouter. This is exactly the kind of extra info I was hoping we might get.

[img]http://www.catsailor.com/bb_files/122373-Viper_F16_AHPC_spi_power%5B1%5D.JPG[/img]


[img]http://www.catsailor.com/bb_files/122373-Viper_F16_AHPC_spinn_pull_1%5B1%5D.JPG[/img]

I think we have a Viper coming our way. I'll keep you posted on the head to head. Of course, if Robbie Daniel is sailing it we know what the outcome is going to be.

My understanding is that the first USA Viper is heading to the gulf coast of Florida and will come with a carbon mast. It is reported to weigh 120 kg.

If I have this correct, emphasis has been placed on the rigidity of the Viper. Hence, the beams are central to this and will bring some extra weight. But I believe the logic is that the Viper will be a very stiff boat and the extra weight will not be a performance factor.

I am just relaying information that has been directed my way from AHPC. I am not an engineer.

Cheers
Bob

If I have it right, the boat is coming to GYC and will be sailed by a father/son team. I think it is replacing an N-17.

So will this open the pandora box of carbon sticks in the f16 group? I am limited on my knowledge of what is out there, but has anyone placed a carbon stick on an F16 platform yet? And since the blades and stealths seem to be around min weight already, if they do go carbon, where would you add the weight?

About 25% of all the F16's sailing in the world have a carbon mast. Mostly Stealths, but a few one-offs and now a few Blades are sporting them as well. They have been part of the F16 class from the very beginning.




Somewhere ! <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Part of it at the top of the mast to get at the minimal required F16 mast tip weight.

Wouter

My boat should be about on Minimum all up weight single handed(104kg), but I have carbon beams.

did any of the F16 at the GC have carbon sticks? Wondering how the ones with the carbon do against the noncarbon ones.
Is the viper coming only with carbon or is that an option?

I think 3 boats at the GC had carbon masts. They were all over the spectrum. The Viper comes standard with an alu mast, actually the same mast that the Blade has. Getting a carbon mast for the Viper is very much a custom order and I'm sure it took some pressure from the customer to get one.

Wouter