Educated at Stanford and UC Davis, Dave Culp began professionally designing kite powered boats in 1978 at the age of 24. Culp-designed kite boats were entered at the Johnny Walker Speed Weeks in 1978--1981 and the Schmirnoff Speed Weeks in 1986--1988 in Weymouth, England. Culp also co-designed and built a rigid winged 28 foot hydrofoil, a dozen kite powered craft between 14-30 feet and the OutLeader Brand rule-legal spinnaker replacement kites for America's Cup Class and other yachts.

Author/co-author of 7 monographs on kite sailing for yachts and commercial vessels published between 1989 and 2002 by AIAA, SNAME, AYRS, ASES and ISES. Since co-forming KiteShip in 1996, Culp has specialized in large vessel systems.

Culp has expertise in both inshore and blue water sailing, kite and vessel design, systems design, marine mechanics and project management, as well as boatbuilding in wood, steel and composites.

You've built a reputation for yourself in the speed sailing world. What aspect of this racing niche gets your blood moving? Is it the raw speed? The engineering development? The camaraderie? Can you see a day when there will be a kite boat class?

DC
Kite boats are already allowed in speed sailing. A world record was set and held for 7 years by a kite powered Tornado, back in the early 1980's (http://www.cobrakite.com/jaclad.html ) Last week (April 19-24) Pascal Maka hosted a kite board-only WSSRC-sanctioned 500 meter speed event during the Mondal duVent in Leucate.

Sailcraft design, and especially speed sailing design, is a wonderful mix of art and science. I can still say "my boat can clean yours' clock" and I just might be right. There is no convergence of design in the speed sailing field at all. 5' kite boards sail at an even pace with 125' super maxi cats-and also with hydrofoils, planning triscaths and simple windsurfers. It's an exciting design space to work in.

It seems that to break a soft water speed sailing record, one must either employ a hard wing sail, twin rigs, canting rig or a kite? What are the strengths and weaknesses of these approaches?

DC
There are 2 fundamental requirements for high speed sailing-really large amounts of power and low drag. Kite boats and boards-even more so than wind surfers or maxi cats-have an ability to generate and to harness enormous amounts of power relative to their weight and size-and the wind they can sail in. Solid wing boats, on the other hand, can have extremely high overall L/D, through drag reduction. One approach is brute power-often in very high winds; the other is finesse; Yellow Pages Endeavour set her current record while sailing at nearly three times the wind speed. Both approaches are valid; perhaps next week we will see a flip-flop of regimes.

In your opinion, what speeds are realistically obtainable in soft water speed sailing under the current rules? Does a one week format not provide enough opportunity for the proper conditions to develop? When is Speed Week?

DC
With suitable budget and current technology, 100-120 kph (55-65 kts) is achievable, in my opinion. Above that is also possible, but will require some fundamental advances in design philosophy. Changes that are already proposed, almost surely, but not yet tried. Kite power can likely achieve these speeds, though other approaches can as well.

A one-week fixed event is not the likeliest opportunity to set a world record, but it is an extremely cost effective way to have a good chance of doing so. In the past 5 years or so, the Weymouth event has delivered 4-6 world-class weather days for potential records; actually quite a good ratio. The best likelihood for records remains the custom event, where one or several boards or boats wait on the beach, sometimes for many weeks with all crew, timers and officials paid to do nothing while waiting for weather.

In the meantime, Speed Week remains useful and a great deal of fun. I'd say it is more the available budget of boats and boards that attend rather than the venue that has prevented a new record being set there, although revolutionary boats and concepts continue to try to prove me wrong. The organizers put on a very professional event and it is cheap to attend, considering. Weymouth Speed Week is 4-10 October, 2003. See http://www.speedsailing.com/

Kites seem to come in different designs. Flatter blade style kites, more common on boards, to larger rounded belly kites more along the lines of what you developed for Oracle/BMW racing. What are the primary differences and benefits between these configurations?

DC
There are 5 major kite types used for traction. Inflatable tube kitesurf kites, all of which are derivatives of a single kite, are powerful and readily relaunchable after a crash. However, ram air foils and rigid framed kites are faster (up to 70 kts) and can have a higher L/D although they are not as convenient to launch and recover. As kite boarding matures from the current focus on tricks and jumps towards serious racing, expect more and more innovation, as opposed to the current knock-off scene. There is a newer kite from New Zealand, which looks like a cross between inflatable tube and ram air foils which shows considerable promise. Very high L/D, relaunchability and a large range of depower make it a potentially hot ticket, for both boards and boats.

KiteShip's OutLeader kite is a new type of kite entirely. Because of the requirement to keep it legal as a spinnaker, and the need only to beat conventional spinnakers' performance, we developed a kite like no other. We know of no other controllable traction kite which simultaneously has only 3 lines, no bridles, no inflatable chambers, no battens or spars, no ram air or double surfaces, no stiffeners or padding and no discontinuous surfaces, which is why we have applied for a patent for it. The OutLeader has a high lift coefficient and a relatively low L/D-both similar to conventional spinnakers. In addition, it is as easy to fly as a spinnaker; another parameter we felt was needed to penetrate this market. (Remember, a kite is flying in 3 dimensions, with 3 axes of control to screw up.)

The OutLeader takes advantage of smoother, stronger winds aloft-I find many sailors are fundamentally unaware of the dirtiness and turbulence of the wind they sail in. We take it for granted. Flying your rig for the first time above the soup you've spent you life fighting is an epiphanic moment. Add to that the ability to "work" the kite, flying it faster than the boat-and your competition's spinnaker-is sailing and you have an unbeatable combination.

The world took notice when Oracle/BMW launched their kite in the Hauraki Gulf. Some thought it was Psychological warfare, others thought it had real potential. Why didn't Oracle/BMW Racing employ the technology in actual racing?

DC
It was a straight psy-ops stir-up in the end. The project was terminated several months earlier. Though we finally met every parameter Oracle set for the kite's performance, it was decided at a high level that there was not enough time left to build a stable of kites and to train the crew in flying and especially in tactics. It was too bad, really, since they had budgeted money for the ramp-up and we provided the technology, but time did us in. Time is the ultimate currency in America's Cup racing and even Oracle had a finite amount of it. In their press release, one of their head designers said, "If we'd had more time we would have been able to use the kite in the LV Cup."

Via two-boat testing we demonstrated fairly conclusively that the combination of higher winds aloft and the power multiplying maneuvering of the kite-we coined the term "dynamic sheeting" a number of years ago-really does deliver more speed to the boat, even in highly restricted classes. With practice and quality crew work, it is likely to be much faster.

You had once mentioned to me that launching, jibing and retrieval were not complicated with a (kite) rig. Can you go through each exercise and explain the basics of how the boat is rigged along with techniques for each discipline??

DC
Launching and retrieval are straightforward. There is a video on our website which shows several views of a launch. See: www.KiteShip.com. We often use a fourth line-the spinnaker retrieval line-to both launch and retrieve the kite. It is attached near the leading edge of the kite and taken to the masthead. On hoisting-typically without yarning-the 3 sheets are trimmed and the kite fills, flying up and slackening the retrieval line. At this point, we keep that line slack and just fly from the 3 lines-the retrieval line is not allowed to carry any sailing load. The kite begins flying close to the boat-sheets perhaps half a boat length long. We then ease all 3 lines, moving the kite out to 3-5 boat lengths and go for it. Retrieval is similar; the retrieval line is trimmed smartly, which pulls the shape out of the kite, de-powering it, and slackens the 3 sheets. If the kite is close enough to the boat at the time, that's all that is done. The retrieval line takes the head of the kite up the mast and the crew bags the sail tail-first. If the kite is on long lines when retrieval is started, skillfully following with the sheets will keep the kite lifting slightly, allowing retrieval from unlimited long lines. In addition, we have an "abort" technique that deposers the kite 100%, allowing retrieval even under water. Knock on wood-we have yet to damage a kite trawling with it.

Since retrieval happens at minimal load and well outside the working sail, we believe there may be merit in dousing very late, even after the mark. We can also launch the kite without the mast or a halyard at all, but with more difficulty-we are happy to use the boat's equipment as long as it is there.

Gybing is a neat trick, as we need to leave both the stick and forestay in the boat. Frankly, I'd rather remove both-it makes life much easier. In the end, it is not too difficult to work with both, using either lazy sheets or tweakers to effectively move the kite's attachment points around the boat-and around the forestay.

Unlike a symmetric spin which is partially depowered during a gybe-or an asymmetric, which is fully depowered, a kite is powered up during the maneuver. You fly the kite through the gybe-it actually moves faster during the gybe than during sailing-meaning it is delivering more power at this time than it normally does. Gybing is a technique long used by kite powered vehicles to accelerate the craft. Gives a new meaning to "gybing duel" eh?

We use the same line tweaking method to balance the yacht-we can move the effective attachment point anywhere along the boat's length, balancing the helm under any condition of course or rig power. Since all lines run from the deck, not the masthead, roundups and spinouts are a thing of the past. When a kite powered boat gets really powered up, it just goes faster.

I can't see kites ever becoming mainstream in buoy course racing due to the amount of room needed between yachts and the area needed to get the full effect of the kite. On the other hand, it seems kites would produce a huge advantage in distance ocean racing such as the Transpac, Trans Atlantic crossings, Marblehead to Halifax, etc. Do kites comply with the rules in regards to sails being used in these races?

DC
We went to great lengths to build a legal spinnaker under both ISAF and IACC rules. Though the acid test-surviving a protest-was never taken, Oracle kept the AC measurers in close contact throughout the development-much like TNZ did with their hula-and received a final "go" from their offices. We assume that any class based on these regimens will find the kite allowable. However, it would be ridiculously easy to outlaw kites, either straight up or through subterfuge in rule writing. Classes are going to have to want to use them; they are not meant to be rule cheaters.

As to buoy racing-and match racing for that matter-I believe kites are a bit misunderstood. It is common in kite land sailing to enter dozens of kite buggies in a single race without significant mishaps -see http://home.tiscali.be/kitebuggy/hardelot.html . These buggies are sailing at 20-50 kts only a few feet from each other, yet mark roundings are no more hectic than similarly crowded roundings in sailboat races. All the kite lines are parallel to each other. The kites are very maneuverable; even high speed passes and crosses rarely result in trouble. There are a few three-dimensional right of way rules added, and racers do make mistakes, but it is nothing like the fustercluck many imagine it to be.

There are significant tactical advantages to flying kites instead of spinnakers. The obvious, relating to when a yacht has crossed a finish line or reached the two boat length circle at a mark, probably needs to be rethought. Think hull position, not rig. I've been asked what happens when the kite boat is burdened, must stay clear of her competition, and is "attacked" by the burdening yacht. First, the kite can be flown up to about 65 degrees, requiring a very close pass to foul it. Second, I mentioned that the kite attachment point can be tweaked to anywhere on the boat. I failed to point out that this could be back up the mast itself when needed. At the other end of things, when the kite boat is the burdening boat, it has the ability to fly its kite down very low, easily low enough to touch the burdened boat with kite or lines, forcing a foul. Also, the yacht can gybe the kite without gybing the hull or mainsail-in fact it is probably possible to barberhaul the main and sail far alee, extending the meaning of "starboard" to new realms. When the kite is taken across the wind window in a low pass it exhibits great power-and leaves a huge wake in its path; related to the wind energy extracted, not to the size of the kite. So, not only can an upwind kite boat shadow a downwind yacht far away from its "normal" shadow, the shadow can be hugely powerful and far reaching. Oh, and of course a downwind kite boat can't be shadowed at all-even if the upwind boat has a kite, it is not possible to keep the moving target in shadow.

After visiting your web site, www.kiteship.com you seem very focused on Commercial marine applications for kite use. How will kite use benefit the Commercial Marine Industry?

DC
In studying attempts to bring back commercial sailing ships in the 1980's, it struck me that they were doomed to fail for the same reasons commercial sail failed in the 19th century. The cost of the equipment, expressed as a rate of amortization, was far higher than powered vessels, even including their fuel. Second, the fundamental inability to schedule wind power plays havoc with effectively utilizing expensive ships. Motor sailing was and is possible to fix this, but requires parallel systems on the boat-wind plus diesel-at even higher total cost.

Kites, on the other hand, can be added to existing ships. They take up no deck space, require minimal retro-fitting, need no ballast, fit under bridges and can be taken in out of the weather when not in use. They can be taken off the boat for maintenance and even used on a second boat when/if adverse or no wind is expected aboard the first. These factors dramatically decrease the capital cost of the sailing rig, thus the amortization rate. If added to existing vessels, especially if the vessels are partially depreciated already, it becomes very cost effective to fit a single ship with both power (which it has) and kites (which are cheap). It can then pure sail, motor sail or straight motor, as conditions dictate. I wrote a paper on the subject, http://www.dcss.org/kitetugs.html in which I suggested such an arrangement might become cost effective when diesel fuel hits about $1/gal.

KiteShip has just signed a Letter of Intent with the cruise ship company Adventure Spa Cruises (www.adventurespacruise.com) to design and build an 8000 sq ft kite and to use it to pull a 200' commercial cruise ship. The intent is to showcase environmentally friendly fuel saving technology, further develop kites and control systems for ever larger applications, and to demonstrate to Adventure Spa Cruise customers a proactive stance regarding potential near-term fuel price spikes and shortages. We are excited about the prospects for this technology and look forward to a joint venture with Adventure Spa Cruises.

What does the future hold for kite technology?

DC
Thanks for the softball! The future holds huge potential. Kites might add significant advantage to both casual buoys and to match racing, offering both greater speed and more complex tactical duels for existing boats in existing classes. They are safer than spins and their gear is often cheaper, never more expensive. Without candor, I think they are as revolutionary as spinnakers themselves, and have the power to fundamentally alter yacht racing in a similar way.

Big kites are exciting to watch and highly photogenic, something the new America's Cup protocol seems to want. Kites on offshore yachts will very likely raise the bar on all ocean records-in my view kites are inevitable for this reason alone. Imagine a Maiden 2 or a PlayStation with a 15,000 sf kite in the Southern Ocean.

In the commercial vessel area, kites hold the potential to change the way we move goods across oceans. They are eco-friendly and sufficiently cost effective to herald a return to sail that the Earth's finite petroleum supplies mandate. They can-and will-be computer controlled and auto-piloted; it is KiteShip's core business to lead the world's shipping in this direction.

Thanks Dave!!

Thanks for the interview.

John Zisa

 05/11/2003