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The magazine for those working in design, construction, and repair

NUMBER 62DECEMBER/JANUARY2000$5.95

DESIGNER ADRIAN THOMPSONFIRE PROTECTION IN MARINE COMPOSITES

MERRITT'S BOAT AND ENGINE WORKSWESTPORT SHIPYARD

A drum Thompson's designs alwaysappear both aesthetically and

technically remarkable. Even know-ledgeable observers wonder beforeeach hits the water, "Will it reallywork?" That's just what many are nowasking about his latest effort, the 120'catamaran Goss Challenger, whichveteran singlehander Pete Goss willenter in The Race—a nonstop globalcircumnavigation under sail scheduledto begin at the end of next year.Incorporating 50 million miles of car-bon fiber filaments in her structure(and still under construction as of thiswriting), Goss Challenger may be themost radical offshore racing sailboatever created. And with some luck, she

may just round the world in recordtime.

Unlike those who cling to provenformulas for popular consumption.Thompson seems instead addictedto rare design missions that seek ex-treme goals and novel solutions. Heprefers to approach each problem witha blank slate, letting logic, not tra-dition, determine his angle of attack.Fellow designer and friend Nigel Irensremarked, "If the logical solution doesn'tlead to something rad ica l , Adr i anwouldn't be interested." Thompsondoesn't argue the point.

Still , for all the apparent uniquenessof a Thompson powertoat or sailboat—monohull, multihull, or hydrofoil—you

can still find l inks to the notable workof other designers. One could evenargue that few, if any, of Thompson'sdesign concepts are absolutely origi-nal. Nevertheless, he has an uncannyabili ty to meld the fu ture with thepast and the experimental with thepractical.

Unti l the early 1980s, Thompsonwas a successful Scottish farmer

and only recreational sailor. "But," he-says, "with a few grand burning a holein my pocket, I thought, 'Might aswell build a boat.'"

That boat was a cold-molded 30-footer called Alice's Mirror, Thompson'sinitial step down the path of minimiz-

46 PROFESSIONAL BOATBUILDER

A farmer/furniture maker turned boat builder/designer Adrian Thompson's first major com-mission was the 60' trimaran Paragon (above),built about 15 years ago. A distinctive andsuccessful raceboat, she displays a number ofbold departures for multihulls of the period: aminimal main bull, large amas (outer hulls).recurred akas (crossbeams), a broad beam(45'). and advanced-composite construction.Facing page—Photographed in his studio notlong ago, Thompson continues to show remark-able intuitive skills: the rendering on the desk isof his Goss Challenger, currently under con-stmction in England. (For more views of theChallenger, see pages 55 through 57.)

ing drag first, then optimizing power.With a displacement-to-length (D/L)ratio of roughly 80, she more thanqualified as an ultralight displacementboat (ULDB), hut her generous beamand water ballast made her muchstiffer than the slimmer California-style ULDBs from designers such asBil l Lee. Al though Eric Tabarly 'sSinglehanded Transpacific Race win-ner, Pen Duick V, first employedwater ballast in 1969, it wasn't untilthe late '70s and early '80s thatdesigners of singlehanded racingmachines began to embrace it. ToThompson it seemed the obviouschoice for a beamy hull, because itincreased the boat's stiffness at low

angles of heel, whereas adding massiveamounts of weight to the keel—thoughlowering the center of gravity—onlystiffened the boat as it heeled. Widerboats sailed better when kept upright,sails remained more efficient, and inlight airs when you didn't need thewater ballast you could lighten shipby simply dumping the ballast. Rightout of the box, Alice's Mirror planedat 14 to 15 knots in flat water, loggedday's runs of up to 250 miles, andhandily won her class in the presti-gious and tough Round Britain Racein 1982, beating an impressive arrayof much larger boats in the process.

Staying with construction for awhile, Thompson helped build ad-

vanced boats like the Kevlar-Nomexmaxi Whitbread racer Drum (which,despite major problems, eventuallyfinished the 1985-86 Whitbread Racethird on elapsed time), and the One-Tonner Jade, "which was brilliant butcrazy," acknowledges Thompson."That was before there were any rulesabout construction. Four of us couldpick up the hull quite comfortably. Itwas a completely lunatic boat, but wedid win the One-Ton Cup."

Then Thompson captured a designcommission—for a 60' trimaran. Thatboat, Paragon, would become animportant vessel in the evolution ofracing-multihull design. "She startedout as a cruising boat, actually," says

DECEMBER/JANUARY 2000 47

Though most closelyassociated with multi-hulls. Thompson is alsoadept at monohulldesign and construction.The inverted hull in hisshop is Drum (aerialview, below), whichcompeted in the1985-86 WhithreadRace. The boat goingtogether in the shop fore-ground was designed bythe late Lars Bergstrom;it is Hunter's Child, oneof a series of solo race-boats made famous byHunter Marine's WarrenLiihrs. His Child serieswas the cover story inProfessional BoatBuilderNo. 53.

CHRISTIAN FEVRIER

Thompson. "The owner wanted some-tiling fast. But when he came down tolook at the hull, he wondered whereall the berths were going to he. 1 toldhim, 'Well, there's not going to be alot of room.' And he replied, 'Well,might as well make it into a racingboat.' So we cut the sheer down a bitand went off from there." Indeed.Thompson pared the slim main hu l lto a minimum, enlarged the amas, or

outer hulls, with notably more volumethan anyone else's (200% of total boatdisplacement), spread out the plat-form with a massive (for the period)45' beam, and t i ed i t a l l togetherwith eye-popping recurved akas. orcrossbeams.

In addition, Paragon's Kevlar-carbonstructure was highly sophisticated forits time. The boat was laid up wet,using a fabric impregnator developed

by Thompson and his crew; it closelycontrolled the amount of resin thatwent into the reinforcement. Paragondominated the first three legs of the85 Round Britain Race before struc-t u r a l problems in her complexlyloaded beams stopped her. "We hadenough ma te r i a l in the beams,"Thompson said recently, "but it wasn'tall oriented properly at the ends." Thefollowing year Paragon upset the rul-ing French multihulls with an easywin of the Trophee des Multicoques.

Not u n t i l Ph i l Steggall askedThompson to design Sebago for the1988 singlehanded transatlantic racedid Thompson begin to truly distancehimself from the pack. Whereas hiscolleagues cont inued to optimizepower by increasing beam, ama vol-ume, and sail area, Thompson decidedto concentrate on minimizing drag byreducing weight and controlling pitch-ing—a part icular problem for l ightmul t ihul l s , with significant weightsspread out in their akas and rigs. Asmultis bounced all over the sea, theakas bashed through waves, and sailslurched forward and aft, thus destroy-ing the laminar flow of the quicklychanging apparent wind over them.

In the early 1980s, Boston Whaler's 17'and 20' Supercats and later, offshoreboats such as Paul Lindenberg's Fury(which briefly led the 1984 single-handed transatlantic race), had dem-onstrated the value of hulls havingrounded decks and sharp noses withno flare. These forms more effectivelysliced through smaller chop, dampen-ing the boat's pitching. If the h u l lstuffed into a wave, then its narrow,strongly cambered deck shed watereasily and tended to re-emerge, ratherthan trip the boat into a cartwheel orpitchpole. Thompson took the logicalmeasure of lengthening and sharp-ening his bows—in the extreme—making them truly wave piercing.

At the same time, Thompson seizedupon hydrofoil and composites develop-ments. Designer Marc Lombard andothers had reduced the parasitic dragfrom complex foils by reverting toelegantly simple invertecl-T or -Y foils.When pressed, the foils supportedamas, minimizing drag and preventingthe amas from adding to pitch energy.The shorter, lighter amas and singlebeam to cany them also helped con-centrate weight amidships to easepitching and lighten ship. Thompsonbuilt Sebago in carbon fiber, greatly

48 PROFESSIONAL BOATBUILDER

improving her light-air performanceover other foil-equipped boats, manyof which were a l u m i n u m . A l ight-weight, easily driven boat, Sebagorequired less sail, thereby reducing rigsize and weight, which also reducedboth heeling and pitching forces. Withless drag, the boat required a smaller,easier-to-handle sail plan that couldbe hung from a highly efficient car-bon wing mast.

Sebago was 60' long and wide yetweighed just 7,000 Ibs—virtually halfthe weight of her major rivals. Herneedlelike main hull (with a beam ofonly 4.5') and streamlined amas couldspear right through a serious chopwithout causing the boat to leap allover the ocean. "It was a really nice b o a tto sail ," says Thompson. "Paragonhad been a big, full-blown multihullwith 200% buoyancy floats and deckgear for Africa on it—chunky winchesand so on. Going upwind, you reallydid feel the loads. She was absolutelydone up like a bowstring. Sebago wasquite the opposite: playing the main-sheet, you'd kind of waft along at 18or 20 knots." Despite shearing off afo i l on f lo tsam ear ly in the race,severely handicapping her, Sebago

managed a very close fourth placeand set an American singlehandedrecord for an east-to-west crossingthat still stands. But she did not win;as Steggall h imself pointed out.Sebago was not only quick to acceler-ate, she was also quick to decelerate.demanding constant attention fromthe lone skipper if he was to sail herclose to her potential.

This problem would be irrelevantin a powerboat, and in 1990 Nick

Keig, a well-known mul t ihul l builder/racer, asked Thompson to create awave-piercing 30-footer to blast acrossthe bumpy Irish Sea to the Isle ofMan, where both Keig and Thompson

Phil Steggall's racing tri Sebago repre-sented further experimentation forThompson, who designed and built her.Lightweight (7.000 Ibs) and very beamy(60'. same as her length), Sebago sportsa needlelike main hull. Note the wave-piercing amas with foils beneath.

DECEMBER/JANUARY 2000 49

lived. The 50- to 60-knot Very SlenderVessel, patented and trademarked asthe "VSV," is likely to keep Thompsonand his now-partner Keig in chipsand grog for the foreseeable future.

True, there's nothing new about askinny powerboat; the revolutionary,34-knot, steam-turbine-driven Turbiniadesigned by Sir Charles Parsons anddebuted in 1897, had a length-to-beam (L/B) ratio of 11.4, whereas theL/Bs of VSVs may be as low as 6. Still,most powerboats are intended to rideover waves, so their hulls usually flarefrom their narrow waterlines out towide decks. By contrast, Thompson'sVSVs feature Sebago-like streamlinednoses that are expected to disappearup to 16'below the waves and yet re-emerge easily. Thompson hasretained a planable wide and flattishshape aft but has also incorporatedhighly flared, semi-tunnel chines thatrun from deck level at the bow to thelower edges of the stern. These pro-vide dynamic lift at speed, control theheeling angle into tight turns, andhelp dampen rolling at rest.

The military was quick to exploit theVSV concept for fast patrol boats andlong-distance transports for specialoperations. To intervene in a crisis—aterrorist attack on an offshore oil rig,for example—"the military have beenusing deep-V hulls," says Thompson."But when it's blowing 15 to 20 knots

50 PROFESSIONAL BOATBUILDER

Seen from above, Sebago resembles a huge water spider. Left—Thompson aloft onSebago Is wing mast, designed by Barry Noble. The boat set the American single-handed record for an east-to-west transatlantic crossing that still stands.

and the sea state is 3 or 4 and you'redoing 50 knots in a deep-V, the G-forces are going to be around 15 to20. You can't stand up. You spend allyour time hanging on. Four hundredmiles of that reduces your ability tofunc t ion . On a VSV, we get onlyabout three or four Gs." All this whileusing approximately 20% less fuelthan a conventional V-bottomed hull.Also, the VSV's low-slung form,rounded shapes, and composite struc-ture make it less visible to both eyeand radar than other craft.

Although Thompson admires themultihull wave-piercing powerboatsdrawn by designers Nigel Irens, RogerHatfield, and Morelli & Melvin—notingthat their even slimmer hulls may pro-vide the ultimate in pitch dampeningand fuel efficiency—Thompson pointsout that multihull wave-piercers havetoo much wetted sur face for thespeeds he needs to achieve. More-over, he says, "they can't fit into anairplane for rapid, long-distancedeployment. And, I don't think youcould turn them in three times theirlengths at 50 knots at which we pullfive Gs; our boats have to be able tobank into that kind of maneuver."

Licensed builders have so far builtabout 20 VSVs. It 's hard to te l lwhether the conservative yachtingestablishment will ever embrace theVSV, but to date at least one client has

commissioned Thompson to design aJames Bond-like 36m (118') motor-yacht with accommodations for 10.

Despite Thompson's VSV success,sailing still called. Five years ago

Peter Goss, a skilled and daring sailor,asked Thompson to design a mono-hull for the Vendee Globe, a single-handed nonstop race around the-world. The result ing boat, AquaQuorum, can be considered a big sis-ter to Alice's Mirror: "You know whatwe designers are like," Thompsonsays. "We get a drawing we're partialto and we just put it through thecopier." But he notes tha t AquaQuorum was hardly a carbon copy.The race rules stipulated that all mov-able ballast could not heel the boat atrest by more than 10 degrees. NeitherThompson nor other open-classdesigners were brain dead: "If youhave a rule that limits the ballast ratioof the boat, then obviously people aregoing to draw wider and widerboats." Although Aqua Quorum dis-played greater beam t h a n Alice'sMirror, Thompson kept her midriffmore moderate than the extremeFrench "aircraft carriers" of this period,to gain a bit more upwind capability.

Thompson also traded water ballastfor a swinging keel. More than aquar ter century ago, the late L.Francis Herreshoff had proposed a

DECEMBER/JANUARY 2000 51

In the context of his other work, Thompson's patented Very Slender Vessel hullform is less surprising bill no less stunning. The fast,wave-piercing, elliptical-sectioned canoe body with a planing surface aft allows reduced fuel consumption and increased rangewith modest power requirements. It also corners like a rabbit, provides a soft ride, and presents a low profile—-features not lost onthe navies of the world. The upper right and lower left photos are of a 50' demonstrator. The lower right photo shows a 30'proto-type, used to test different drive systems. The rendering at upper left is a proposed 50m (164') yacht version of the VSV, withaccommodations for 10.

swinging keel in his seminal hook.The Common Sense of Yacht Design.And Dave Hubbard had created RedHerring, an actual swinger, hack in1980. Both boats were narrow; inHerreshoffs case, because in thosedays narrow boats carried the deepestfins that would he most effectivewhen swung. The actual performanceof Red Herring, however, indicatedthat a narrow boat with little form sta-bility still heels dramatically, and herlifted keel often rode nearly parallelto the sea's surface, m a k i n g i t apoor device for resisting leeway.Thompson and a few others foresawthat the swinging keel would provemuch more effect ive on a s t i f fe r ,beamier boat. Even so, he acceptedthat the keel would serve primarily asa righting-moment mechanism ratherthan a hydrodynamic-lift device.

To combat leeway. Thompsonchose twin, high-lift, low-drag asym-metrical daggerhoards (reminiscent ofthe "bilgeboarders" designed by

Bruce King in the 1970s, which wereso effective their type was soon handi-capped out of existence). Becauseeach board needed to work only onone tack, when set in a trunk angledoutboard from the deck it wou ldremain perpendicular to the sea's sur-face. Although movable-ballast sys-tems above water might prove moreefficient than a swinging keel drag-ging through the water, they wereprohibited by the rules. Therefore,says Thompson, "you make the keelas slippery as you can," adding, "1like the canting keel a lot better thanwater bal las t—especia l ly goingupwind. On any boat that's optimizedfor righting moment with a deep-draftbulb keel, when you're going up-wind, that awfu l pendulum wangsaround with three or four tons oflead on the end of it . The pitchingmoments become frightful in certainseaways. But if you hitch a swing-keelup to windward , then the keel ispretty much horizontal and the pitch

axis of the boat is going through thecenter of the bulb's mass, which isgreat. On Aqua Quorum, we fixed thekeel in a 'normal' keel position andplaced a bunch of people out on therail to mimic water ballast. The ride ofthe boat was just totally different; with thekeel canted and no one on the rail,the motion was miles better."

Racing right after her launch, AquaQuorum finished second in class inthe 1996 singlehanded transatlantic,logging daily runs of up to 314 miles.She was not only fast but tough: skip-per Goss, deep in the Southern Oceanon the Vendee Globe Race later thatyear, turned Aqua Quorum into a 65-knot gale and bashed dead upwind160 miles to rescue fellow competitorRaphael Dinelli. Goss completed theVendee in fifth place in the smallest—and only new—boat to finish.

So it was no surprise that Gossreturned to Thompson for what isundoubtedly the most daring exploitfor both yet. The Goss Challenger was

52 PROFESSIONAL BOATBUILDER

psmail

Racer Pete Goss commissionedThompson to design Aqua Quorum forthe 1996 Vendee Globe, a singlehandednonstop race around the world. In agale in the Southern Ocean, Goss madea daring rescue of fellow competitorRaphael Dinelli (lower left). AquaQuorum's interesting collection ofappendages includes a swinging ballastkeel, twin rudders, and twin high-lift,asymmetrical daggerhoards.

born from a simple directive: create-the fastest boat capable of sailingnonstop around the world. Becausethe current record stands at 71 claysand change (faster than the power-boat record), breaking it requires anaverage speed in the mid-teens. Gossplans an initial circumnavigation as awarmup for The Race, which beginsin Barcelona, Spain, on December 31,2000. A fleet of the most extreme rac-ers ever built wil l scurry round theworld nonstop seeking a new record.

"It's pretty scary, actually," confessesThompson of his newest design. "It'salmost impossible lor any designer toput himself clown in the SouthernOcean with 6()-knot winds and 40-foot seas and come up with a designthat works reasonably well and, moreimportantly, that will survive and lookafter the crew. We're phony designers,really: not many of us venture on our

boats around the world. If I wentdown to the Southern Ocean. I thinkI'd probably not design another boat.When Pete [Goss] was beating backon Aqua Quorum to pick upRaphael...well, you don't in all hon-esty design scantlings, fittings, andreserve factors with that sort ofmaneuver in mind. Structure is not anabsolute science, because a boat is aninterface vehicle that bashes aroundon the surface, and nobody knows atwhat speed it takes off from a waveor at what angle it will land. So if youdesign something radical and sendyour mates down in the SouthernOcean on it, those are the kinds ofworries you have to live with."

Aid living with it he seems to be.Goss' new 120' catamaran is big

enough to span center court atWimbledon. When launched in

January, she will be the largest com-posite structure in Europe, yet herempty weight should fall well shy of50,000 Ibs. Even big conventional catswith high freeboards have stuffedtheir bows in heavy seas, dramaticallyslowing, and in a few cases nearlypitchpoling. Thompson hopes theGoss Challenger's very slender hulls—featuring only 4.5' of beam and 9' ofdepth—will spear through the seasand keep going, though no one reallyknows just how deep she'll dive orhow her 70'-wide platform will han-dle extreme conditions as it spanscomplex wave t ra ins . U n l i k e thet r imaran Sehago, which would l i f tits m a i n h u l l when pressed, theChallenger's leeward bow may rou-tinely dive 16'or more under water.

For all her size, though, the GossChallenger appears delicate comparedto Steve Fossett's PlayStation, a huge

54 PROFESSIONAL BOATBUILDER

"conventional" catamaran with fu l l -volume hu l l s and a skyscrapingrig. "I've always looked at the minimalway to accomplish any job," saysThompson. "That's what gives me mykicks. If you're trying to break theround-the-world powerboat record,you could build a really massive ves-sel, pack it full of engines, and blitz. it.But that's not clever, really; it's just asledgehammer approach. A far moreelegant way to achieve that record isto use technology and design exper-tise to create the smallest possibleboat with the smallest possible engine.That's what we're trying to do withPete's boat."

The Goss Challenger is hardly under-powered, but Thompson knows thatradical is cool only if it finishes, andthat pragmatics often rule at sea—especially in the unforgiving SouthernOcean. "We're t ry ing to create aboat that is safe to sail and handle,"Thompson insists. "Everything has tobe done with muscle power—it's allyou've got, and how quickly you candeal with a problem is critical to safety."Accordingly, Thompson has stressed

simplicity, streamlining, and the re-duction of drag and loads.

"What's driven the whole design,"he says, "is this: How do we handlethe sails in Southern Ocean conditionsdownwind? In a SO-knot squall, youcan't round up because you'll justchase your apparent wind forwardand over you go. So you've got to beable to put a reef in on the run. On aconventional boat, a big-roach sailwith battens is going to bear on thespreaders and shrouds. The crew hasto drag it down. I think that's a bigproblem. The question is, how do weget rid of the sails when we don'twant them? We've chosen unstayedrigs designed to rotate a ful l 360degrees. You can weathercock themand luff them no matter where thewind is. We have long mainsheets,and in the cockpit we'll keep a cou-ple of chopping boards and an axe. Ifthings get really hairy we'll just chopthe mainsheets and let them go."

Without headsails to tend, the crewcan remain relatively safe in the cock-pit, and with no headstays to support.Thompson can eliminate the forward

beam and even "foredeck" netting.Because rig height is then indepen-dent of aka height, the designer canalso afford to highly arc the akas andlift the 5()'-long crew-accommodationscocoon and cockpit, reducing the fre-quency with which the beams andpod will slam into waves. Unstayedwing masts also promise a 30%greater efficiency over stayed rigs, atleast theoretically. And even if thewings get stuck in a blow and areunable to feather. Thompson notesthat in that worst possible condition,the capsize windspeed is about 85knots.

Critics have wondered if the GossChallenger's, theoretical design con-cepts will prove as advantageous inpractice. Large mast loads might ex-cessively twist the very narrow hulls,for instance. But Thompson arguesotherwise. "I don't think the engineer-ing is as bad as for a conventionalcat," he says, "because the loads are alot easier to analyze." A trimaran'smain hull can absorb enormous rig-ging loads, but a conventional catmust somehow absorb them using a

56 PROFESSIONAL BOATBUILDER

complex truss s t ructure suspendedbetween the hulls.

Thompson suggests Playstation asa yardstick. A stayed mast on a boatthat size might produce 100 tons ofcompression, so PlayStation's mainbeam is about 30% deeper in sectionthan the Challenger's, and a lot heav-ier. Additionally, a conventional rig's

forestay would tie to a hefty forward-beam truss that must also withstandloads to about 30 tons, and much ofthis load would be transferred aft tothe main beam via a sizable compres-sion tube. Moreover, mainsheet loadson the middle of the rear beam mightreach 40 tons. F ina l ly , the normalarrangement of staying a mast would

Goss' newest racing machine—a 120'catamaran designed by Thompson forThe Race 2000, a no-holds-barred non-stop sailboat sprint around the world—is taking shape in Devon, England.The low-slung structure extending intothe foreground is an oven for cookingthe all-carbon boat. Hull tooling isseen at right.

lead the cap shrouds well aft on thehulls, so any wracking in the hullsfeeds back into the rig. PlayStation'sdesigners (Morrelli & Melvin, NewportBeach, California) assume that eventheir s t i f f s t ruc ture wi l l allow thebows to routinely flex enough to varyby a height of 8' or more, whichThompson says, "sounds about right"for his boat as well. So trracking canbecome critical.

"These considerable problems havebeen solved at small scale, but areincreasingly problematic with increas-ing size," says Thompson. "All right,we have some crazy masts stuck inthe hulls, but no parts of the structurerely on stays. Although the loads are

DECEMBER/JANUARY 2000 57

The simulated action-figures in this rendering of the Goss Challenger underscore thespaceship-like quality of the big boat. Her helm is protected by a pod for the crew.Note the rig change: Thompson and his team recently switched from an AeroRig(left) to a wishbone setup (right). Each mast rises 137' above deck.

pretty high—a hundred tons of sideload on the mast bearings—the mastsare buried into the biggest element inthe boat and picked up between twobeams, so it's actually quite a niceclean thing to engineer. To counteractthe side loads, we use a carbon fiberstrap that's only 1 square inch in crosssectional area. It's not that much." Thet2-plus-inch-diameter bearings willlikely be composed of high-densitycomposites and run in a l u m i n u mraces.

Overall, Thompson is comfortablewith Goss Challenger's structure. Hisengineers are among the world's mostexperienced. Although Thompsondoes all of what he refers to as the"conceptual stuff—how we're goingto stick it all together," for f ini teelement analysis (FEA) and number-crunching he relies upon SP Tech-nologies (Isle of Wight, England). SPis satisfied the Goss boat will handlethree-G loads with all the weight sup-ported by the corners, and will alsohandle sympathetic frequencies thatcan allow vibrations in structures tobuild in resonance with the condi-tions until the structures eventuallyshake themselves to bits. Goss hasrented a shed and hired an experi-enced crew to build the Challenger.The boat is constructed entirely ofpre-preg carbon, with Nomex honey-comb in the hulls and foam core in

the pod. The masts contain a bulk-head-stringer framework to handlehigh shear stresses.

Each mast carries 400 sq ft of wingarea plus about 3,300 sq ft of sail,creating a tad more upwind sail areathan PlayStation. Each mast rises 137'from the deck, about the same asPlayStation's rig. Critics have specu-lated that the heavy unstayed rigsmay aggravate pitching and detractfrom stability. Thompson admits theunstayed masts will be heavier, "butwe're not sure exactly how much. Be-sides, you have to look at it a little moreglobally," he insists. "A stayed mast isroughly the same size from top tobottom because it's a compressionstrut, so the CG [center of gravity] isgenerally at 50% of its height." TheGoss Challenger's, masts taper from2m (6.5') of chord at their base to .5mat their tips, so the CG's only 30%from the base. "If you do your sums—the weight of the rig times the CGheight—you'll find our pitch inertia alittle bit lower, which is quite nice,"he concludes. Finally, notes Thompson,"You also have to put into the equa-tion associated gear with a stayedmast, like the heavy forward beam."

Stil l , the Challenger's design teamhas had to confront troublesome

details required for their concepts towork. Obviously, the cantilevered spars

will bend—possibly up to 9'at the tip.though Thompson confesses it mightreach 16'—but the bend dynamics arenot obvious. When the design team an-alyzed the bend three-dimensionally,they realized that 15 tons of leech tensionwill curve the sticks one way, whileheeling loads bend them another. Atested scale model has helped refinethe design and allowed the sailmakers(Halsey Liclgard of Southampton, Eng-land) to rewrite their programs toaccount for the complex dynamics.Even the sail track got tricky, becausethe aft side of each mast shortensby 8" due to compressive bending,requiring expansion joints in the track.Details regarding the latter item areundisclosed.

The Goss Challenger's boom arrange-ment, too, has markedly evolved. Thefirst AeroRig sail plan showed thehallmark "ballestron" boom that pro-jects forward of the mast to carry asmall j ib, but Thompson eventuallydecided against it. "Probably I'mwrong, but to get enough tension onthe headsail to make it pay its way, Ithought the mainsail shape would suf-fer, because you get this backbend inthe mast. Also, it was quite a lot heav-ier." Again the design team deep-sixed complexity in favor of a fresher,simpler direction. The Challenger crewcan set l ight-air drifters from theunstayed unarigs that still provideenough power to begin flying a hullin 12 to 14 knots of true wind.

Thompson's team more recentlyexamined their first wishbone-boomdesign within which the large-chordwings need to rotate. With enough

58 PROFESSIONAL BOATBUILDER

DECEMBER/JANUARY 2000 59

curvature to hoop the rotated stick,and enough strength to handle 35-toncompression loads, each wishbonebecame a ha l f - ton monster. Thedesigners then realized they could slotthe wishbone between the sail trackand the structure of the mast, reduc-ing the camber to contend only withthe curve of the sails, increasing theircompressive capabilities and therebyreducing their weight by half. Evenso, Thompson notes that the wish-

bone size can "pretty well encompassAqua Quorum.''

The most fundamental compromiseof the Cross Challenger's design, how-ever, is that the leeward rig must sit inthe turbulent lee of the windward onewhen the apparent wind is about onthe beam. Because of the large shift inapparent wind, this will be when thetrue wind is fairly well aft. Only seatrials will tell how much of a handi-cap that may be. Otherwise,

Thompson and his team seem toalways remain a step ahead of thedoubters. They're even providing pro-tective pods around the leading edgeof each mast for crew working there.And, should something go wrong wayout on the end of an eased leewardwishbone, then anyone unluckyenough to have to crawl out that farwill at least be contained by a nettingsock beneath the wishbone.

The Goss Challenger team has noillusions of warp-speecl potential.

"I don't think she's going to be fasterthan any 60' multihull on flat water,"says Thompson, who recognizes youcan't fight the law of similitude. "Ifyou take a 60' multihull that weighsfive tons, make it twice as big, andkeep the same proportions of rig,then the sail area increases fourtimes—a squared factor—but the dis-placement of the boat will increaseeight times—a cubed factor. You'redealing with that rule the whole time,and it's cast in stone. Our boat can't carrythe same sail-area-to-displacementratio as a hot Open 60 trimaran likePrimagaz. Nor. for that matter, canPlayStation. The only reason a biggermultihull is faster overall is becauseit's less affected by waves and theweight of all the gear and storesrequired to sail around the worldnonstop."

None of the above means theseboats will be slow. On the contrary.Thompson f igures the GossChallenger will sail in the 20- to 30-knot range most of the time. "More tothe point," he says, "I hope the boatwill slip along at 28 to 30 knots with-out it feeling too dramat ic . Someboats at 28 knots feel a little alarming.We hope that the low-drag hulls onChallenger wil l move along at thatspeed, and any seas will easily clearthe beams."

Similitude can also prove to be anally. Challenger's twin mainsails weigh160 kilos (352 Ibs) each, compared toPlayStation's 800-kilo (1,760-lb) main,making the Challenger's sails easier tohandle.

Presuming Challenger wil l be lesslabor-intensive than her competitors,and because her crew can operatemostly from the cockpit using onlyfour winches, skipper Goss figureshe might even be able to sail hisChallenger around the world with asfew as five crew. But Thompson is

60 PROFESSIONAL BOATBUILDER

less certain. "I ' l l probably get shot forsaying this, but I think that all theseboats will be very physical to sail andevery task will take more people thanyou th ink it wi l l . " He believes theGoss Challenger will eventually sailwith about 10 crew. Regardless, she'llinevitably be able to sail with at leasttwo to four fewer crew than her rivals,and considering food and gear, willsave a half ton for each person thatcan be left on the dock. Remember,two tons equals 10% of boat weight.

If Thompson's design proves suc-cessful, then it might just lead to anew style of cruising multihull honedfor comfort of motion and ease ofsailing. Thompson already has oneclient thinking of it. Goss Challenger'srig, too, promises a simpler life forcruising sailors and may finally allowunstayed spars to closely competewi th stayed ones. "I think there'squite a future for unstayed masts,"says Thompson. "Mult ihulls are notbrill iant performers when they haveto drag all that rigging upwind, espe-cially in light airs, because you comeup against a brick wall when your liftequals your drag. Just cleaning up thedesigns and mak ing th ings moreorganic—I think there's a future inthat."

A; for Thompson's own future, "Itend to hop in big steps, which

has high risk attached," he says. "It'squite stressful designing boats, espe-cially at the sharp end, if you can callit tha t . You lose your appetite forsticking your neck out after a while.I'll hate it when they launch this boat[Goss Challenger]. Trials are nerve-racking. Everyone's aspirations arerunning so high. In their minds, theboat's already sailing 40 knots and isbrilliant in every way, and you knowit's not going to be like that, really.No, designing these kinds of boats isa young person's business."

So at the ripe old age of 52, AdrianThompson dreams of throttling back,returning to making furniture, maybeeven building a nice, slow, conven-tional cruising monohull. A what!?"Well, yeah, absolutely, as a reactionto what we do normally." he says. "Itwould probably be wood, like Alice'sMirror, which I enjoyed building. I'vedone so many composite boats—it'sreally like a chemical process. Woodis just nicer to work with."

It's hard to picture Adrian Thomp-

son lolling about on a t rad i t iona lBritish cruiser. Or carving a Chippen-dale chair. But who knows? The manloves to surprise.

About the Author—A multihull sailorwith many offshore passages to hiscredit. Stere Callahan has designed andbuilt a number of these boats. He wrotea short text on multihull design whileworking at the Yacht Design Institute 20years ago.

As this article was goingto press, we learned thatPete Goss has a new titlesponsor and therefore, hisboat has a new name. Itwill now be called TeamPhillips, thanks to RoyalPhilips Electronics. —Ed.

DECEMBER/JANUARY 2000 61

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