Here's how a PDQ owner replied to a general question about power catamarans on Trawlers & Trawlering List: > Anybody have any experience/opinions about power catamarans? The Admiral and I own a PDQ 34 power catamaran trawler and absolutely love it. (Technically our 80 foot sidewheel paddleboat/retirement home is a power catamaran, but not particularly applicable here). We were the first PDQ power cat owner on the west coast, and have cruised our boat across the Great Lakes (delivering it from the factory near Toronto Canada), round and about the Columbia River system plus coastal runs up around Washington into Puget Sound and the Canadian waters around Vancouver Island. > My wife and > I live aboard our 54 ft trawler - but friends are strongly considering a > cat of about the same size. You didn't mention them living aboard full time -vs- extended cruising where your regular household goods stay ashore. I'll assume the long cruising mode, based on your next statement. As liveaboards you doubtless understand already that it is a whopper of an adjustment to get rid of all the treasured stuff we accumulate, which causes folks making that transition to full time live-aboard for the first time to get into rather larger boats. There are a good number of power catamarans capable of the west coast long cruise in considerably less than 54 foot lengths. If you meant space equivalent to a typical 54 foot monohull trawler, you would be talking about typical catamarans around 40 foot lengths. By virtue of their shorter, squarer overall layout, they allow more roomy accomodations to be nearer each other, with great light and visibility for the stuff on the bridge deck, compared with monohull designs which force every functioning space to more or less line up on a single axis and be relatively low to the water. >They are interested in cruising and fishing > from Baja to the Northwest. I'll further assume that you and your friends are familiar with the weather, sea conditions, harsh coastlines and both the scarcity and the dangerous entrances to the harbors of refuge that distinguish our Pacific coast boating from most other places. My point is that nearshore and offshore west coast boats need to be a lot more hardy and have much longer ranges than most others. Please caution your friends that not every power catamaran design meets these needs well. >High speed is not important - plan to cruise > in the 10 - 12 knot range I dissagree, to the extent that I feel that the option of high speed can be a lifesaver. Speeds of twenty knots and sometimes considerably more are readilly available in power cats, and offer a broad choice in going fast at reasonable fuel cost or going slow at amazing fuel economy. The ability to outrun nasty sea and weather conditions, and the power and maneuverability needed to safely thread some of our more 'adventerous' harbor and river bar entrances is essential hereabouts. >but is considering some higher speed cats with > the plan of cruising slower (single engine op possible ???) Yes, and despite the props on my boat being 12 feet apart, the single engine handling is quite reasonable (probably due to having two slender 34 foot hulls acting as keels). Just a little 'windward helm' and it works fine. I don't do that because with my slender hull design, I can get down to around 1 gallon per hour with both engines on at maybe six knots, transitioning smoothly (virtually non-planing) to a fast cruise of four gallons per hour near sixteen knots (in peacefull water), and I have kissed twenty two knots a couple of times ('downhill', at damn the torpedos fuel economy). Weather and waves make a huge difference. Example; my boat carries 115 gal. in the main and 70 in the forward/generator tank. Downriver from Portland to Astoria in a leisurely day, just over 100 miles, topped off tanks around 25 gallons. Next day, over the bar and slugging up the Washington coast to Neah Bay, about 100 miles again, and a tough 12 hour transit; but with fifteen knot winds and a knot or so of current on the nose and seas/swells running from six feet at the south to upwards of fifteen feet at the north end. Again in a day; fuel burn 125 gallons. > for fuel > economy and having the higher speed avail for shorter runs or >emergencies. Yeah, but I value very highly a huge fuel capacity so I have the option of going fast/hard and thirsty or slow and thrifty depending only on my whim and wallet, and avoid the temptation of counting on extending the range too far and risk not having a safe fuel reserve for some emergency. > > I have applied Keith's Formula to an excell SS. Any thoughts on the > validity of Keith's to a powercat? Coefficients? I am unfamiliar with this formula, and I generally suspect that catamaran hulls are different enough from monohulls that great modifications would need to be made to it to get realistic predictions. Two related formulae -- or relationships seem pertinant to me. One is the familiar 'hull speed -- wave trap computation that dominates monohull design. Wave trap speed in knots equals one point three four times the square root of the hull length in feet. Here you calculate the speed where the trough behind the bow wake crest and the trough ahead of the stern wake crest appear to move along the side of the hull toward each other as the speed increases; up to the 'hull speed' where the two troughs merge and reinforce each other. Thereafter increasing power only seems to dig a deeper hole in the water. The bow wake crest is literally all the water that had to be shoved aside to accomodate the hull as it progresses. The attendant trough is the result of the inertia of the water sloshing outward away from the hull and then sloshing back to form a second crest, etc. in a harmonic pendulum like way. The size of the crest, and therefore of the trough is dependent on how much water had to be shoved aside: the frontal cross sectional area of the immersed portion of the hull -- and the speed with which it was shoved aside. The shorter, wider and deeper the hull, the more water must be shoved out of the way. The faster you go, the more energy you invest in moving this water. When the bow wave system and the stern wave system troughs get close to each other, they link up and reinforce each other, where a strictly non planing hull is caught in it's wave trap. Planing hulls of course use lots of power and a plenty of lift from the flat shape of the bottom (working kinda like a water ski) to climb up and over the bow wake crest and then fly at speed 'on the plane' that is with very little displacement and all lift. This works great, although it takes several times more power, depends on a suitably flat bottom, and it's performance is only acceptable at certain speeds, well below the planing threshhold and well above it. If the frontal area could be dramatically diminished (for the same length), the depth of the resultant wave trap would also shrink. A sufficiently powerful long slender hull, still in displacement mode could power it's way up to and over the top of the bow crest. This is sometimes called 'slender ship theory' and it works quite well. Think of the WWI 'four stack' destroyers, 430 feet long and maybe 25 feet beam. With tiny displacement and lotsa coal fired steam power and they would go into the high thirty knot speeds, maybe even the forties (I count on my naval history expert listmates to correct any of those recollected but unconfirmed details)! Catamarans can by virtue of having two hulls to support the displacement load have much less beam of each hull (the portion actually in the water). Catamarans can also employ planing hull shapes and more powerful engines, and these are often called tunnel hull cats, with what appears to be a regular planing hull split down the middle with a relatively narrow tunnel. There is a wide selection of approaches, although all designs utilize both schemes to some extent. Many of the power cats around today lean toward the planing tunnel hull approach, with wide individual hulls and total power aboard well over 300 hp. They have fine high speeds and behave much like any other planing hull with some refinement in boat motion, mostly underway. The PDQ power cats (check out the brand new 42 footer at their website: pdqyachts.com!), the hull designs of Malcolm Tennant, Moretti and Melvin, and a few others (as well as virtually all sailing catamarans -- naturally low powered) lean heavilly toward the slender, non-planing hulls with low power and therefore thrifty operation. There are an increasing number of really intermediary designs, with hull length to hull beam ratios appearing to be in the 5:1 to maybe 8:1. These seem to still cling to the large engines and fast planing speeds, but the lower power and slimmer hull design seems to me to be a slow trend here. My PDQ 34 has a beam for each 34 foot hull of about 34 inches. Powered by a pair of 75 hp engines, there is no regular wave trap or step like planing behavior, and speeds can be selected anywhere up to top speed with an attendantly smooth power and fuel economy curves, topping at around five gallons per hour at wide open throttle speeds around 19 kts (in relatively flat water and without wind). There is some planing shape to the aft half of the hulls, added to remedy the stern drop you get when the merged 'wave trap' trough reaches the stern around twice hull speed. The net result is that my boat's bow raises about five degrees at full speed, so I never have to leave my comfy lower helm station to see over the bow, and need no trim tabs. Fine weather and fancy docking alone tempt me to the flying bridge. With two hulls weighing four tons each seventeen feet apart there can be no pendular roll (the only roll happens when a swell raises one hull before getting to the other (very mild, slow and graceful); so no need for stabilizers or paravanes underway or stationary. The props are twelve feet apart so the boat can even pivot around a center about even with the lower helm; no great need for bow or stern thrusters. Clearly I really love these boats and could go on swooning about mine for days, but will instead close by suggesting that your friends consider chartering a PDQ 34 from Sunsail in Vancouver Canada, or if they like they are welcome to visit me in Portland for extended discussions and boatrides. They are also welcome to call as well, email me offline for address and phone numbers. PDQ has also arranged for Swiftsure Yachts in Victoria BC to be a stocking dealer, so anyone interested could reach them there as well. I have no financial interest in this beyond being a very happy and gregarious owner. Gary Bell Stray Cat, a PDQ 34 power catamaran trawler, hull 012 home port is McCuddy's Marina on Multnomah Channel, Scappoose Oregon (near Portland) We also own a custom 80 foot sidewheel paddleboat who's hull happens to have a four foot wide tunnel down the middle so it too is a power catamaran.

I enjoyed your post, Gary. We are planning on owning our first Cat in 5 years, when we cruise to Alaska. In 10 years, the Great Loop. For now, we are "settling" on our 3rd/final 25 footer. Our Regal 2465 is being delivered upstream from you at Rocky Point next week. We will likely be on a weekend cruise the weekend of Nov. 10th. If you're out that weekend or around Thanksgiving, please advise. I'd love to hear about your adventures and see your boat. -Greg Ps....Is your paddleboat docked at Goble? > > Gary Bell > Stray Cat, a PDQ 34 power catamaran trawler, hull 012 > home port is McCuddy's Marina on Multnomah Channel, Scappoose Oregon (near > Portland) > > We also own a custom 80 foot sidewheel paddleboat who's hull happens to > have a four foot wide tunnel down the middle so it too is a power > catamaran. > _______________________________________________ > Power-Catamaran Mailing List