New 14'-16' Daysailer/Weekender Design: Raison d'etre

Looks like a really slow and expensive catamaran, that wont be able to get close to a beach.

 

yeah that too.

 

This had been done by Wojtek Wierzbowski. His Viper 550 proved to sail very well, at least on lakes.

regards

krzys

 

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Thanks for that! Any sailing pictures or more info?

 

Modern hull model for comparsion. In parentheses data for two bows hull:

LOA -6,5 (6,5) m;
BOA -2,5 (2,5) m;
Displacement -750 (750) kg;
BWL -1,83 (1,94) m;
Wetted surface -7,96 (9,01) sq.m;
Transverse metacentric radius -2,08 (3,34!) m.

20 deg. heeling:

BWL -1,46 (1,18) m;
Wetted surface -5,99 (5,67) sq.m;
Bow heeling - 1,5 deg. (0 deg.)

 

I have seen this concept suggested so many times it amazes me that there are so few good examples. I think that since they are prohibited from racing as monohulls most designers just lift the center out of the water to cut surface area drag -yet another cat with low deck height.

All I could find about this design is translated below. The interesting thing is that it sounds like he went with a planing hull aft which makes some sense -planing would lift the bow enough to avoid pounding.

This article seams to be about a proposed 9.3M version.

"Positive test boat Viper 550 (Sails 1/2004, 2 O 3/2007), user reputation and their own impressions of the swimming prompted me to design a boat Viper 930 with unprecedented properties. Uncompromising shape optimization method maximizes performance and comfort at a relatively low cost. Flat bottom boat close to a rectangular outline, allows for free, shaping interior and deck. Berth cabin is positioned laterally moved up to the front. This gives the place a huge mess of unprecedented dimensions on much larger yachts. In the middle of the mess is building a string of free communication. Inside, there is the daggerboard case. Capacity and convenience allows you to use the Viper 930 for the conference, cruise, integration, training, etc.. The interior volume is comparable with conventional boats with a length of 12-13 m

Uncompromising is the hydrodynamics of the boat. On even keel, using the tunnel effect ease of planing, virtually creating a wave without losing energy to "dispersion". Wide, concave stern is similar to a paraglider canopy, making maximum use of the drive energy to lift the boat and achieve high speeds. The tunnel bow and carries forward the pre-charter and "lubricates" the part of the underwater air bubbles, further reducing friction. The inclination of the Viper is a "catamaran flowing on one float" with narrow, symmetrical plane and a great moment straightening. It is so fast boat and a fast, safe sailing yacht depending on the needs and whims of users. The unit uses water ballast, taken to sail the strongest winds, and cast itself (after opening the valve) to swim in the slip and transport (solution used for many years in the Mac Gregorach).

Vipers design is combining the advantages of monohulls and multihulls: compactness of shape, courage, simplicity, security, samowstawalności, habitability for the former and speed, large righting moment for others. At the same time leave their flaws "genetic" other constructions. All components are in compliance with the rules. A large number of full-size bunk is not made at the expense of comfort and space communications.

Viper hulls are made in molds negatives in sandwich foam HEREX and GRP. This gives a rigid, lightweight, thermally and acoustically insulated, unsinkable hull."

"Specifications:

Hull length 9.30 m
Waterline length 8.8 m
Width 2.48 m
Draft 0,28 / 1,1 m
Weight 2600 kg
area. jib sail / blade / gemaker 34 m2 of
ballast water to 650 kg
80 hp outboard motor
service - min. of one
number of berths solid 12
lizba double cabins 2
Number of bathrooms 2
number of seats in the cabin 30
max speed. 45 in."

translated from http://www.port21.pl/2007/07/dwa-dzioby-vipera-930/

 

Thanks,Cacker! Good stuff.....

 

How does the performance compare to a catamaran of the same cost?

Note that I'm not a multihull fanatic at all. It just seems to me that past a certain point it is simply stupid to try to keep pretending that a severely mutated monohulll isn't trying to be a catamaran, and you might as well do the job properly instead of making a half-arsed beast that only incorporates the worst of both monos and multis.

 

Its explanations like this that make me wonder if these guys understand what they are talking about. Yes ALL hulls entrain some foamed water under the hull (that's why the plumb bowed Riptide 35 had such problems with its water ballast system at speed)

But the notion that a tunnel like that is anything but an energy sucking wave slapper, or that it generates "tunnel effect" Is just nonsense. and the "wide concave stern" is hardly what drives lift for planning. If that were the case you would see surfboards and waterskis designed with wide fat stern shapes

and at one time you actually had them. But they turned out to

1. be slower
2. not turn as well
3. and not plane any sooner

than pintailed boards

 

Once again it is translated from polish. He claims success in the smaller 5.5M but I found nothing on the webb about the performance. I think the planing claim is for motoring. I thought the size, power and sail area numbers were interesting.

 

Well an 80hp motor on a 30'er suggests a pretty inefficient hull. Olson 30s can get away with a 4 horse and typically run a 10 horse and both get them to hull speed (though the 4 horse wont if bucking more than 12 knots of wind)

so if he is putting an 80hp on there, this is a powerboat more than a sailboat

 

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I'm don't particularly care for the scow shape modified to have "normal" bows, but the tunnel hull scow is a proven design allowing less wetted surface and a higher L/B ratio(on the lee side when heeled) as illustrated in Cackers previous post. A scow -including a tunnel hulled scow- is sailed at an angle of heel up to 30 degrees upwind and nearly flat downwind(10 degree angle of heel max) in planing conditions.
There are a couple of Inland Lake scows that have proven the tunnel hull concept, the M20 being one of them.
Using the tunnel hull scow design in a daysailer/weekender will create a boat with more interior room than any boat it's length as well as give a probability of greater performance than current daysailer /weekenders that offer some interior accommodations.

 

Sketch of tunnel sharpie 60`s. It was the racing dinghy.

 

Doug - where has this design been "proven"? We have lots of evidence of that design being a "wave slapper" particularly from the less well designed cruising catamarans. And I know of no successful "tunnel hulled scow" sailboats. Could you please provide a reference?

 

Note that this sort of hull shape has been used by a littoral attack craft http://gizmodo.com/americas-largest-carbon-fiber-ship-is-a-seafaring-spee-1468513351 But it uses massive amounts of horsepower to cause the "channeling"