Cruising Log of the Murrelet

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#3 - A FAST SAILBOAT CAN NOT ALSO MOTOR FAST.

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This myth has been blown away with the introduction of the Mac26x in 1996. But it is a prevailing notion among the uninitiated and is a popular notion in well respected British publications like Practical Boat Owner. This myth has been propagated by the scaling down of large displacement hull vessels for recreational use. When a displacement hull is reduced to less than 40 feet at the waterline, the result while motoring is less than satisfactory, both in speed and stability, unless other design changes are made to compensate. Outside the restriction of displacement hull design, however, there is no physical law preventing "hybrids" that sail and motor well. By my way of thinking, pure power boats, like pure sail boats are "half breeds", capable of doing only half of the work desirable for recreational boating.

Boats can be split into two categories: the ones that dig holes in the water and the ones that travel on top. Race boats, runabouts, fast cruisers, sport fisherman and military patrol craft are part of the planing fraternaty. A few racing sailboats and wind surfers fall into the same cult...

Ralph Naranjo
Ocean Navigator
pg 22 November/December 2006

Sailing Anarchy

Rowing looks gentle, like sailing, but there is a certain violence and a definite acceleration involved at the start of a race. The shells are tippy vessels with the lowest of freeboard and yet on any morning that a pleasure boat might make way through the cut, they will. Stability is gained by balance. The balance of the extended oars and attention to the details of catching, driving, feathering and recovery. These vessels rocket. A sailboat built for high performance sailing is similar. The form presented to the water when under sail will be thin and shell-like or as is sometimes stated racing-canoe like. That is a simlar shape presented by the Mac26x when heeled at ~17 degrees.

The Mac26x doesn't have oars for balance, instead she has water ballast tanks as far from the centerline as possible, which provides stability like extended oars would and maximum hull speed is reached with wind that is normal when heeled between 15 and 20 degrees. A sailboat that is sailed at an angle of heel greater than 25 degrees has to much sail up or needs more ballast. There is a physical law that limits maximum speed in displacement hull vessels. The law dictates that the smaller the length of the vessel at the water line, the slower the maximum possible speed. It has to do with the inability of a displacement hull vessel to climb its own bow wake. The Mac26x hull design is displacement like in the bow but is a planing hull further aft. Hence by moving crew aft and reducing heel to 10 to 15 degrees it is possible to break out of displacement mode and reach planing speeds.

This allows Murrelet to power or sail over her own bow wake thereby both motoring and sailing at fast speeds. To reach planing speeds under sail live ballast (passengers) are moved aft so that the planing part of the hull can do its work in climbing the bow wave and then forward to pop the boat over the top. Mac26x cruisers plane when they have exceeded their displacement hull speed which is calculated fairly accurately IMO through the following applet:

The Mac26x, unlike the Mac26m, also has a "powerboat underbelly" which comes into play while turning at Wide Open Throttle (WOT). As the cruiser turns, to retrieve a water skier for example, the belly provides bouyancy preventing the boat from flipping. Most Mac26x captains, especially those who have mounted 70 hp motors, will reduce speed before turning just as the CLAMS and smart ski boat operators will. Editors of the February 15 through March 15 2006 Nor'westing conclude "The MacGregor 26 remains a popular and appropriate choice for boaters anxious to enjoy a single vessel that can be a very good sailboat as well as a very good powerboat. Enthusiastic MacGregor owners probably wonder why other boaters would ever settle for a boat that is only a powerboat or only a sailboat."

Competing Hull Forms

Sailing Speed

http://www.eskimo.com/~mighetto/p11.htm is one of many calculators available on the web that are used as the basis of marketing claims regarding sailboats. This one defaults to values for the X. If you plug in values for the M you can state that by the math the M has a slightly higher potential for speed under sail when not planing. Her Sail Area to Displacement ratio is 19.067 and the X SA/D is 18.677. Most of that potential is owing to sail area, however, and in practice crew competency and sea conditions will determine which vessel wins any race. The hull speed for the M of 6.437 is not enough of a difference from the X which is 6.426 for it to be otherwise. Couple that with the finding that the X actually sails faster when reefed in many conditions, and one can conclude that both vessels are dissimilar in regards to powering by sail.

The math shows that both vessels are capable of breaking from displacement speed and reaching a true plane. This is indicated by the displacement/length ratio being under 150. The X is significantly better at planing; her D/L is 137.59 vs the M's at 145.61. It probably will take abnormally strong wind (20 knots perhaps) for the M to plane fully ballasted where that potential in the X is evident in 12 knot winds, perhaps less depending on the point of sail. The X has a planing Dribbly style hull form. The M has more of a traditional rounded River sailboat form. The marketing material cover picture for the X (left side) shows her on plane; no wave form is visible on her length. The M, (right side) while cooking in good wind, is at displacement speeds as indicated by the wave form on her length. She is also being sailed at a noticable heel, more like a traditional displacement sailboat. These two pictures portray a vast difference between the sailing styles advanced in the two at-first-glance similar powersailers.

Rendezvous 2005: Huzzah, La Perla Noir!

On Thursday June 16th three Mac26x cruisers (the triple X fleet) joined the 2005 MacGregor Rendezvous. We were unable to catch the Elliot Bay MacGregor fleet but were able to Meet the Pearl with them during the dog watch at Port Orchard.

The Rendezvous Not Quite Race was held on Saturday June 19th. Two of the triple X boats were honored with wine glasses for their fast times around the marks but neither would challenge the Pearl when she hoisted sail to join the fun. Instead the cameras started clicking. Huzzah, La Perla Noir! For God, Country and the prize Juvinal Navitee. Her skipper Tripp Gal is the one with the morbid fascination.

There were almost as many positive flotation power sailers at the rendezvous and race as there were at the J24 Nationals, where several capsized in 20 knot winds and one sank. No compromise on safety with a MacGregor yacht.

BZBWY: US Navy Code for Well done Blue Water Yachts.

"Treading the line between power and sail, the Macgregor is the definition of NO compromise and unlikely to appeal to purists on either side. But if trailerability, exceptionally roomy accommodations and powerboat speeds are high on your list of wants you ought to take a look at the MaCregor 26M."

Small Craft Advisor
Page 59

The word NO has been added to the above quote. But does it really change the meaning? For years boaters have been trained to accept the notion that you must compromise power for sail and visa versa. When Jack London set out for the South Seas he built a sailing vessel with a 70 hp gasoline engine. He ensured that his 43 foot sloop had enough engine power to take on any river rapid or storm surge. That was 80 years ago. Today it is very rare for a manufacturer to recommend a replacement engine for cruising sailboat that is as inadequate as the 30 hp Diesel engines common in the past. That would compromise on safety. SCA on page 52 (as in TP52 supporters caused 26x production to halt temporarily) that owners are installing larger than 70 hp motors. The following was reported to me prior to the rendezvous.

Motoring Speed

In October of 2005 I found myself unwilling to spend any additional money on a 6 year old motor and opened up my wallet for a replacement. BoatWorks magazine www.boatworksmagazine.com came out with its review of the Mac26x and strongly recommended 4 stroke engines for them. I had been following the new 2 stroke machines and it took an intervention by my dealer and crew members to get me to mount the Susuki 50 four stroke on Murrelet.

Yacht Designers will teach students to size a sailboat motor by a heuristic (rule of thumb). It is this training that prevents boat buyers, owners and novice yacht designers from realy considering large engines on sailboats. And there is the myth that inboard power plants are preferable, this myth coming perhaps from the notion that an outboard is more susceptible to being swamped out of action by a heavy sea.

Todays outboards are at least as reliable if not more reliable than an inboard in heavy seas and the advantages involving internal space, maintenance and replacement of an outboard over an inboard are undeniable. There is also the advantage of not compromising the hull design to accommodate the shaft and propeller of an inboard.

Inboard motors typically can not be tilted more than 10 degrees, this owing to the oil pan. Hence the aft portion of the hull of a sailboat is usually lifted to accommodate the propeller shaft and propeller, this harming greatly planing and surfing potential.

There are two motor heuristics currently holding back the future of sailboat design. The first sizes the auxiliary by sail area and the second by boat weight. Both ignore planing potential, which became possible with modern materials such as fiberglass. FYI these rules are, 1 hp per square foot of sail and 3 to 5 hp per ton respectively. Both rules of thumb make the mater of auxiliary power in a sailing yacht more complicated that it really is.

There is very little difference in cost between a 70 hp or 90 hp motor and a 50 hp motor. There is also little difference in weight and when the boat is designed to be buoyant where the motor is to be placed, as the X is, why not? The operator can always run at low RPM, this being good for the life of the motor and making the motor run quietly and there is comfort in knowing that should the reserve power be necessary, say during the perfect storm, that it is available. A larger auxiliary motor also means more sail can be carried because the motor can be used to override overloaded sails.

Date: Wed, 25 May 2005 17:54:54 -0600
From: Bill Barnett
To: mighetto@eskimo.com, dbarnett@Champ.usu.edu
Cc: BarnettG@central.edu
Subject: rpm and mph for 26 M with 90 hp E-Tec at higher elevations

Frank,

My boat is a 2005 MacGregor 26M. We live in Utah and at this time trailer to lakes in the rocky mountain area. Most of our destination lakes vary in elevation from 4500 ft to 7,000 ft. The power output of outboards at these elevations is considerably different than at sea level. So, while some may debate my choice in size of motor, I will just provide some data from the tests I have conducted in my search for appropriate prop size. I had a 2005 90 hp Evinrude E-Tec Saltwater Edition installed by our local factory authorized Evinrude dealer. The motor is clean, quiet, high tech, no mixing of oil and no problems meeting any state's emission standards. While it has power trim tilt and electric start, it can also be rope started. Weight is 318 pounds. The owners manual suggests selecting a prop that allows engine to attain 4500 to 5500 rpm at wide open throttle (WOT). My dealer would like to see over 5000 rpm and preferably towards the 5500. The redline is not indicated on the gauges or in the minimal owners manual, but I believe my dealer said 6000 to 6200 rpm. The props I have tried have all been 13.75 inch diameter and I believe the first prop I tried was a 15 inch pitch. I did not have my GPS at the time for measuring speed, but the prop was inappropriate as it would only turn a bit over 4000 rpm WOT (tested at 4700 ft elevation). I will provide no further data on that prop, which I returned. I then evaluated two props at 4680 ft and 5932 ft elevations. In both instances the boat has typical gear in it, carrying 12 to 16 gallons fuel and myself. I collected data with ballast full and empty. The props were a standard format prop 13.75 x 13 (diameter x pitch) and a high thrust (HT) 11 inch pitch prop that my dealer liked for pontoon boat applications. I did not care for the 11 inch high thrust prop. The speeds were down from the 13 inch prop and there was some cavitation with it, while there was no cavitation with the standard prop.

At 5932 ft with the 13 inch prop WOT rpm was 4800 rpm and speed was 23 mph with ballast tanks empty. At 4680 ft the WOT data were 5000 rpm and 25 mph, while with tanks full wot was 4650 and top speed was 21 mph at 4680 ft elevation. With the 11 inch diameter pontoon boat style prop the rpm were a bit higher and the speeds quite a bit lower. The 4680 ft elevation performance data are shown below.

I have yet to evaluate a prop that allows the motor to operate through the optimum rpm range, but I liked the performance with the standard configuration 13.75 x 13 prop and I will keep it since it will probably also do well if we drop down a bit in elevation. At the elevation I use the boat, the 90 hp motor seems a suitable match. I liked cruising at 4000 rpm and nearly 19 mph while the engine was not straining at all. Feel free to share this information. I would enjoy participating in the big BWY regatta you described.

...Bill

Table 1. MacGregor 26M with 90 hp Evinrude E-Tec. Data collected at 4680 ft elevation, air temp 65 F. Ballast empty or full.
RPM	13.75x	13.75x	3 7/8 x 11	3 7/8 x 11
	13 empty	13 full	HT empty	HT full
1000	4.4	4.3		3.4
1500	6.5	6.2		5.4
2000	8.0	7.8	6.8	6.7
2500	9.3	9.0	7.7	7.6
3000	12.4	10.8	8.8	8.5
3500	15.5	14.5	11.4	9.8
4000	18.7	17.0	13.5	12.5
4500	22.3		16.5	15.5
4650		21.00
4800	23.0
5000	25.0		18.5	18.2
5150				18.6
5250				20.0

BWY sells a Tohatsu 70 hp that is the same weight as the Tohatsu 90 hp. The Pearl sports the 70 hp motor. BWY boats are oriented to sea level operation and it is believed the 90 hp overpowering. However, Bill's data indicates that the 90 hp may be desirable at higher altitudes. Because insurance companies have no objections to owners placing 100 HP motors on Mac26x and m cruisers, there has always been preasure on the manufacturer to support them. In the X brouchure is the statement.

We limited the engine size to 50 hp for a number of reasons: An electric start 50 hp motor provides lots of speed, yet it is light enough so that sailing performance is not compromised. It is about the largest engine that can be started by hand, a nice feature if your battery goes dead. It is also about the largest engine you can pick up and move around. Try getting a 100 hp engine off the boat and to a repair shop. Also, the heavier, higher horsepower engines really eat up gas.

Different Sailing Styles

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The X is meant to be sailed flat, with stability and ballance coming from the flexible (also called soft) rigging as well as centerboard positioning. She gets most of her power from the head sail. The M uses a roached and powerful main and has a harder rig. The headsail is far from a source of power. The M mast rotatates to take advantage of the power in the mainsail while pointing. The X's centerboard jibes to windward to provide better pointing. The M uses a wide daggerboard foil rather than a high aspect ratio swinging centerboard foil. These are very different pocket cruisers requiring very different sailing styles for reaching speed potential.

The very different sailing styles are reflected below decks on the early models. The M table is smaller and hinged so that it can be dropped and kept level. Seats are backed to the hull sides rather than forward and aft as they are on the X. This is because while sailing the greater heel of the M boat makes the use of an unhinged table impossible and sitting facing forward uncomfortable.

Compare this with the more multi-hull or powerboat below deck accomodations on the X. The dinette table and forward seat are ment to be used as navigation stations. At slow speeds, in foul weather and on cold nights, I have crew pilot Murrelet from the navigation station using GPS and radar and the autopilot remote, all which are positioned so the table can function in that manner. The M galley and head block the view, so this mode of operation is less acceptable in checking out obstructions identified by radar and gps and totally unacceptable for single handed sailing. Besides the table isn't large enough to hold a chart properly. The official web comparison for the 26x to 26m doesn't refer to the navigation station needs of cruising. Instead is the statement:

"A centerboard trunk presents a 16" high problem from the mast almost back to the steps. Unfortunately, this ridge dominates the interior plan, and made it essential to bring the seating structure on one side out beyond the centerline. This forces a dinette type of configuration, which makes it more difficult to have a good conversational type seating for a bunch of crew members. It also reduced the interior floor space (and thus moving around space) by a significant margin. The daggerboard trunk, which is partially hidden by the galley, eliminated these problems."

Nonetheless, by the math, both vessels are ocean passage sailboats. There is no significant difference in the capsize risk ratio (X = 1.94 vs M = 1.91). Both are solidly under 2 which is the cut off point defining an ocean worthy cruiser and the ratios only improve when the boat is loaded for passage making. The M does not have as good a ballast/displacement ratio (M= .3615; X = .3722) meaning that the X is slightly more stable than the M when unloaded. I was informed by a factory representative that a swim platform for the M is being planned and that when this is engineered there is a strong likelihood that it will work for the X as well.

The X hull form appears to be similar to the Tasars which are the advanced form of the Dribbly hull. If the X hull is also the Tasar/Dribbly hull then there are characteristics known to apply. These include sailing faster than river hulls (like the M) in the chop of a harbour or around a crouded racing bouy. It also puts X vessels into a traditional hull form from 100 years ago as well as the truely modern Tasar form. See

http://www.cs.stir.ac.uk/~kjt/sailing/tasar/tasar.html

and http://www.macgregor26.com/drawings.htm

The first is the current form of the Dribbly hull and the second is the Mac26x cruisers. Frank Bethwaite in High Performance Sailing page 248 states...The fourth (Dribbly) hull was designed in 1969 by Mark Bethwaite, and was the beginning of the truly modern stream.. he designed a boat with a long fine entry forward, and a long flat run between wider and almost parallel chines aft. When I watched it take shape I reflected that there is little new in this world. I recalled the 'cod's head and mackerel tail' that English Bristol Channel pilot cutters developed through the nineteenth century, which had the same asymmetric 'deepest forward and widest aft' general shape (fig 20.2). The Bristol Channel is discussed on the next tab.