Hi everyone, it's my first post here and I thought I'd kick it off by sharing my thoughts about my first ride on a viper F16. I was fortunate enough to spend last Sunday sailing on a Viper F16 with Greg Goodall, designer and builder of the Viper F16.

First off, I'd like to make a disclaimer. In recent years, all my cat sailing experience has been on a Taipan 4.9 and an Boyer A class Mk4, so my review of the Viper is in relation to these 2 boats.

Layout- The layout of the Viper is very much like race ready F18. The components are all extremely high quality, Ronstan fittings and spectra lines. One of the features I loved the best was the external downhaul which runs under the trampoline. The spinnaker setup was a single line to a cleat on the mast. The layout of the system made it very easy to raise and lower from a starboard tack making it very ideal for windward leeward courses. There's no doubt the layout is really intended for course racing.

The centreboards, compared to the Taipan, are much narrower and longer, and my impressions under sail was that the boat generated a tremendous amount of lift (IMO more so than the Taipan) going upwind.

On the water- The Viper has a lot of freeboard. Coming off an A class, I felt like I was sitting really really high off the water. The hull shape of this boat makes it sit on the water rather than in the water. This may surprise many, but I actually found it a little easier to get and keep the Viper moving in light airs compared to my A, which has the older hull design and tends to sit in the water. This hull shape also means that the Viper felt faster and easier to tack than the Taipan

Tracking- The helm on the boat was extremely neutral, maybe a little more so than for my taste, but it felt extremely light to steer.

Invariably, everyone is going to ask about the weight, did it matter? Did that extra 18kgs matter, especially in light airs? For myself, no I did not feel like it mattered at all. In fact I did like the extra weight in the light airs as the momentum kept the boat moving through small chop which is normally a little more challenging to get through on an A.

The other reason I am ok with the weight is because a large chunk of it comes from using F18 beams (it's really surprising how big the beams are on the Viper), and the overall feeling was that the viper is very very stiff. More so than the Taipan 4.9.

The F16 mainsail seemed a little harder to trim accurately compared to my A, but perhaps this had to do with the fact that the sail was practically brand new and perhaps not broken in yet. But on a practical basis, trimming the sails, setting up rotation etc, is pretty much like the Taipan F16, which uses the same rig. The prebend settings, mast rake, spreader angles are pretty much like the Taipan F16.

Downwind with the kite up, the boat was a real joy the sail. The hull shape meant we had to sit further forward than I was used to as the bow didn't dig in as much or as quickly as a Taipan under spinnaker. My impression is that the Viper will really shine in heavy airs both upwind and downwind.

However, one thing that does concern me regarding the Viper is that this boat really shines as a 2 man racing machine due to high high volume hulls. For a smaller, lighter person like myself who wants to sail this boat one-up, it might be harder to manage the hull volume compared to a sailing a Taipan F16 one up ie, keep the bow pressed down and going through the waves upwind in choppier conditions

In conclusion, would I get one? yes, in a heartbeat. But it's a lot of money for a boat (fair enough, since it's a real racing machine, like buying a Ferrari), especially because of the strong Australian dollar, but certainly on the F16 racing circuit, it would be a very capable 2 up racing platform IMO.

The external downhaul running under the tramp... please describe it in more detail.

Same as seen on the Capricorn. Basically, rather than the downhaul cascading system going into the mast, it does through the tramp and sits underneath. Rather neat and out of the way. Don't have a pic or a link to one. Sure someone else can provide that.

Take a look at the Capricorn Owner's Manual - page 18 and 24 have pics showing where the downhual runs through the tramp.

http://www.ahpc.com.au/p_techsupport.htm

The cleats are outboard next to the front beam - red line. Under the tramp, the lines pass back and forth through microblocks to provide additional purchase.

This is a pretty good system - as mentioned, very clean and low-profile with the tails sucked up into the front beam by bungee. I have found that the line is prone to chafe where is contacts the gooseneck and have replaced that section of line three times in two years of pretty hard racing. Also, you must pay close attention to resetting the system between races or you risk having all the downhual pulled out one side or the other - there's a good bit of line in the system and in the front beam, so it might take two or three races, but you'll eventually have one of the microblocks under the tramp dead-end against the fixed cheek block.

always seems to happen that way doesn't it? always end up maxed out on one side then you go to get some more and nothing...
that and the rotator

There is a lot to be said for keeping it simple and easy to see when it comes to systems.

We had the internal downhaul system on the super taipan but on Sunday we broke the intrnal rope and had no way to fix it on the water... so now we are changing it to the Tornado style, simple, external and easy to maintain.

Its easy to make the cunningham and jib sheet endless to avoid the problem of getting all the rope on one side.

I think any boat is prone to this since line tails started getting hid away. I've just made it part of my between-race routine to even everything out - jib sheet, downhual, rotation - in preparation for the next sequence. My skippers hear me call it "housekeeping." The AHPC downhual is particularly sneaky because you don't just run out of line - the blocks bottom out where you don't see them. <img src="http://www.catsailor.com/forums/images/graemlins/tongue.gif" alt="" />

With the Tornado style system (same as Nacra infusion and Hobie Tiger) you can easily make the downhaul endless so you never run out of rope and its also easy to adjust the pre-tension on the system to take any slack out of the system depending on the wind strength.

Endless Jib sheets and rotation are really cool, even if you leave the leeward side uncleated you can simply pull the windward tail and cleat the leeward side.

Exactly, my taipan and A cat downhaul drives me crazy when i need to replace the rope internally. What should normally be a 10 minute job becomes and hour and a half job with drilling and riveting.

The Aussie Blade F16 is fitted with a very similar externally cascaded system as well. The VWM Blade F16's in standard setup has also a external cascaded setup but that one lays along the mast.

This setup is getting pretty common on designs. However I personally still prefer the internal system alot. Mostly because I keep my boat on the beach in all weather, salt and sand. External lines become hard and abbrasive very quickly under those conditions. And that makes downhauling very hard. The internal downhaul system does not sure from that.




I have indeed opened up my mast to get to the internal downhaul system ones, but didn't spend so much effort and time on it as it made out to be here. There are several tricks to avoid drilling and rivetting or spend lots of time on it. Shouldn't take more then 20 minutes all taken together.



Basically, I unstep the mast but leave all stays attached. I lay the mast next to the boat. Then I unhook the diamond wires from the spreader arms; the diamond stays go slack. The unscrew to two retainer screws from the mast bottom and the whole mast base plate comes undone. I take it off and let it hang off the mast by the diamond wires.

I then pull the first stage line and the first stage block drops out of the mast. I untie it from the second stage line and stitch a long "helper" line to the end of the second stage line. I then pull on the third stage line (last stage that comes out of the mast) and the whole internal block system and all lines drop out of the mast. That includes the wholly internal the second stage line as that one terminates at the floating block and not at the mast bar or something. The only exception are the two blocks that are fitted to the internal bar but I glued those shackles tight so they will never come undone; I also carefully selected those blocks and shackles so it will take decades before they wear through.

Basically everything is now out of the mast ready for inspection/repair/replacement. Gettting the stuff back in is the same procedure in reverse direction.

Doing the whole job take about 15 to 20 minutes if you don't waste time yacking to interested passers-by.

Last time I did it all internal lines looked as new (1.5 years of sailing and leaving the boat out on the beach in weather and sand).

The first stage line itself (the one you are holding) can be replaced very easily without doing stuff like taking mast off the boat. Just stitch the new line to the old line and pull the setup with a little care throught the blocks and out the other end. I do this every winter because I want to wash my downhaul line clear or salt and sand that has accumulated in it over the sailing season.


But I guess you have to think systems like these through before making them and repairing them. I did when I designed and implemented this 3-stage cascading system. It is both more powerful and runs smoother then the standard AHPC internal system and more easily repaired.

Wouter

ckuang,

Thanks for the report !

Was the Viper actually measued at 125 kg ?

I also seem to recall that Greg redesigned the Viper beams and stopped using the Capricorn beams for it. But I have no written proof of that. Can you confirm or deny that ?

Wouter

No scales to measure the weight in Singapore, so still speculation as to whether it is 125kg, or above/below that.

Beams do look like the Capricorn beams, big and chunky and making the boat look a lot bigger than 16 feet. Not sure where they manufacture those though.

Though to add my observations on the seeing the Viper on the water, crew weight on the Viper needed to be moved a long way forward to compared to other catamarans. Upwind in the light stuff needed the crew on the front beam (or forward if possible) as the bows tend to ride high and you want to get them down to water level.

And downwind in 10 knots it is really strange seeing how far forward the crew and skipper are. Almost upwind mode really. I was going wild and sitting towards the back beam on the A and the Viper guys were near the front beam. Would be interesting to see this boat in 20 knots, but that tends to be a rare occasion in Singapore.

For me if choosing this boat, would look at what crew weight you would be sailing with. If on the heavy side (145 kgs plus for 2-up) then this is a better choice compared to other platforms. But if you are sailing at those weights you are really getting to ideal F18 crew weights.

Hi Wouter, with regards to the weight issue, no we did not measure it on scales. I spoke to Greg regarding the weight issue and he said the first few boats, which we got in Singapore, were a little heavier than 125kgs ie around 132kgs because of shared components ie rudder casing as the F18. These F18 components on current production boats have since been switched out and now the boat is around 125 kgs. Unscientifically, having pulled Nacras around the boatyard for years, I am guessing the weigh in of 125kgs is about right.

But as far as beams go, the beams are still the F18 beams, which I really prefer over the smaller taipan beams especially since the Viper is wider than the current taipan. One can really tell the difference in stiffness on the water . The way the boat powers up and moves makes it feel much more like an 18ft platform than a 16ft platform.

And yes, TaipanFC is right, the boat really likes having the crew sitting way forward upwind and downwind in light airs. According to Greg, the Viper was designed with the intention of being a boat that is really fast and easy to sail in strong winds and high wave conditions without giving away too much performance in light airs. He was saying one of the problems with the F16 modified Taipans that were extended to the 2.5m width was that in really strong winds, with the new big head sails, spinnaker, etc, the hulls tended to submarine easily. According to Greg, the original T4.9 was designed to be sailed best in 12-15knts and the new F16 sails were really pushing the limits of the hulls in a breeze. The viper hulls was designed to rectify that problem.

It was great sailing with the designer and learning what the viper was really designed to do.

Thank you for the post! You write very well, I am envious!

Please return often.

I seem to recall in discussion a few months back that the opposite was suggested - i.e. it may be better suited to a lighter crew, since the boat itself has the extra weight.

I think you need the extra crew weight to be able to maximise the hull length in light breezes. With the hulls riding up under normal weight distribution, the extra weight helps push the boat into the water. Just my view from the weekend. The Viper that went well was more aggressive in moving crew weight around.

Why would you want to maximize hull length in light breezes ?

Waterline length is only important for the top speed of a sail craft (F16's : 12-20 knots range), something you will not encounter in a light breeze anyway.

In light winds you actually want to decrease wetted surface area and one way of doing that is by shortening the waterline ! Many monohull yachts have specially curved sterns to do exactly that : Shorten waterline length when the craft heels over less (= sailing in light winds)

Wouter

Forgot to add one interesting feature I noticed about the Viper. The stern section, unlike the taipan and A class flyer, has a very square profile, resulting in a very flat stern section.

In the light air, Greg had me sit far forward, in front of the front beam, to get this flat stern section out of the water. I'm not much of a naval architect or boat designer, so I'm not joining in the debate about longer waterline vs reduced wet surface area as i know nothing about either.

Feeling curious, I asked him why the Viper had such a flat stern section. I had the impression that perhaps the flat section was there to allow the cat to plane. His response was surprising.

According to Greg, he feels one of the flaws of current cat design is that current U shaped sterns makes it increasingly harder to sink the stern the more weight one puts on it (to get his exact views you might want to email him). This u shaped stern design seemed a little counter productive in strong winds as one would normally step further back to sink the stern and keep the bows up. So in effect the U shaped stern that is hard to submerge is working against the crew in a breeze.

In contrast, the squarish stern (with a tear drop profile) is at first difficult to press down, but once past a certain point, it gets progressively easier to sink the stern, making it easier to keep the nose up in a blow. I thought that was a brilliant idea, the only drawback being that the squarish stern does create more drag than u shaped sterns in lighter airs and the drag needs to be minimized by moving crew weight further forward.

I had to ask "Why not just make a narrow V stern so it's easy to sink in a blow?" Greg explained by having a narrow V stern, every time the boat hit a wave and raised it's bow, with a narrow stern, the boat would simply hobby horse. By having a square shape stern with a higher initial resistance to sinking, it helped to prevent hobby horsing.

How this relates to wetted surface area vs waterline length, I have no idea, but thought it was a really interesting design feature of the boat. Apologies for forgetting to mention this in my original post.

Here's a photo of the stern section, it also shows the big volume hulls and bigger section rear beam.

Well to add my opinions on the Viper. Finally got on one for near an hour over the weekend in 5 to 8 knots of breeze.

Though I should disclaim that I had been on the A-Cat for 2 hrs training so could have distorted my opinions a little. And I have done an Aussie nationals on a Capricorn so know a bit about its heritage.

Firstly, the weight is ridiculous. Yes the platform is extremely stiff, but the beams, hull volume and the rudders are over-engineered. For me the whole F16 concept from the original days was to have a 16ft boat designed for crews who want a hi-performance boat but don't want the size and weight of an F18, and also are below the 150kg total crew weight for 2-ups so don't need to worry about correctors. I don't think the Viper fits into this concept.

Systems and set-up - taken directly from the Capricorn and tried and proven. It is well set out and all works very well. Of all the F16s, it sets the benchmark here. Only grumble is the new Ronstan ratchets for the mainsheet. Don't like the rope attachments and feel a shackle is better, that is my preference for mainsheet systems. (This is from someone who took their own mainsheet to the A-Cat worlds rather than using the charter one so I would feel comfortable with what I was using).

On the water - tracks in a straight line quite nicely. But if you are this heavy, wouldn't you? Really had to push/pull on the steering, but fortunately it is quite docile. Compared to the Capricorn, it doesn't sit high in the water. Maybe that is a factor of length. But Capricorn felt like it was on top of the water, the Viper feels like it sits in. Due to the excess weight, doesn't really jump forward/accelerate in the gusts.

So overall the design is promising, but to me there are some big question marks and it is all down to 1 thing, weight! I know that this was debated previously in other threads, but compared to a Taipan and the other F16 designs, I would still choose the Taipan and optimise it with good systems similar to the Viper set up.