Piercing The Surface

by Bob Brown
Featured in Powerboat Magazine October 1980

Following the trauma of the most recent energy crisis, the marine industry was again rudely awakened to the fact that the need for greater propulsion efficiency was never more acute, Present recreational hull, engine and drive configurations suddenly became out of synch with an environment destitute for an adequate supply of energy. In response, a predictable trend toward boats with reduced overall weight and smaller, less fuel-hungry engines immediately appeared.

However, amidst this upheaval, the marine industry was still perplexed on how to significantly improve its existing propulsion systems: the outboard, stern drive, straight inboard and jet. Each system has become well refined over many years of consumer use attaining nearly peak performance potential. The likelihood of a major efficiency breakthrough in present form seemed remote.

The obvious answer was the development of anew propulsion concept, something that would satisfy an almost impossible list of design and efficiency criteria. The system would have to: create less drag, therefore generate greater speed with equal or less power and demand less fuel; be lighter weight; have equal or better mechanical dependability; have greater design simplicity; require less frequent and easier maintenance. It must also be simple to install in a variety of hull forms; not waste valuable interior hull space; be easily adapted to a wide variation of powerplants; have power trim control over the propeller shaft t angle; and be offered at a price competitive to existing propulsion products. Sounds a bit like Nirvana doesn't it?

Well, maybe it's a little too soon and somewhat premature to proclaim the Arneson Surface Piercing Drive the marine propulsion Messiah for the remainder of the twentieth century, but it certainly has all the earmarks as the most innovative and potentially important discovery in the last 20 years. Although it is not yet available to the general boating public as of printing, it may be by the time you read this article. It's very close to becoming a genuine production item and not just an artist's conception of a display mock-up.

For those mildly acquainted with the term "surface piercing propeller," forget the old concepts that include fixed propeller shafts and cumbersome outboard mounted rudders for steering. The Arneson drive has made these parts obsolete. Essentially the Arneson Drive appears to be such a simple and straight forward answer to the various age-old propulsion problems, it is absolutely remarkable.

In essence, Arneson surface piercing concept involves the notion that propellers do net have to run completely submerged to be efficient and that reducing the amount of mechanical hardware dragging through the water will improve performance. By incorporating the elements of adjustable trim to the propeller shaft, unit swivel steering in place of a separate outboard rudder, propeller placement far aft behind tire stem and operating at the surface of the water, initial tests indicate that the Arneson drive fulfills virtually all the criteria was intended for.

When first inspecting the Arneson Drive, Powerboat vas amazed at its simplicity of design. What happened to all those gears, shafts and brackets we are so attuned to seeing? The external drive unit looks a little like an arrow with aft stabilizing fins and the tap and bottom and a very slender mid-section which houses the propeller shaft. This mid-section fits into a cylindrical base attached to the transom with a precision machine ball socket between. This provides complete 360 rotational movement to the drive unit.

Since a rigid sleet shaft can't bend car flex, a universal joint is used at the ball socket swivel paint to accommodate the transfer of power even when the drive unit as propelling an angle. The transom base contains a fixed shaft which passes through the transom via a small hole. Inside the hull, this shaft is filled with a coupling flange which is reedy far attachment to whatever type of engine/ transmission combination you care to utilize.

Installation of this entire assembly should be a snap since a simple positioning pattern is available to locate the proper height of the mounting base in relation to the bottom of the boat. The base itself needs only for bolts far secure attachment to the transom in addition to the drilling of a hole for the drive shaft. Only two additional holes are needed higher up on the transom to mount the single hydraulic ram cylinder which actuates the trim control.

On the Arneson Drive there are four fins plus one cavitation plate. As already mentioned, two are large vertical stabilizing fins located above rend below the aft portion of the mid-section. The other two are small anti-spray fins positioned forward and horizontally on each side of the upper part of the mid-section These fins divert the water away from the topside mounting flanges for the power trim anti steering arm. Above the propeller, batted to the upper vertical stabilizing fin, a cavitation plate is used primarily far protection of the trop when backing up.

Internally, the Arneson Drive is as simple as its exterior suggests. It consists of two heavy-duty shafts linked together by a universal joint at the ball socket. Both shafts run in a small oil reservoir for lubrication and a series of roller bearings, needle bearings, nylon bushings and stainless steel snap-rings hold everything neatly in place. Remarkably, there is virtually no power loss from engine to prop. Most stern drives create a 15 to 17 per cent loss of efficiency because of their complicated gear composition. The Arneson Drive, however, avoids this and only about one percent loss is created by minimal bearing friction.

In its present configuration, the Arneson Drive is capable of handling engines in excess of 1000 horsepower. Later, a somewhat smaller unit, will be offered which will easily accommodate engines in the lower horsepower range. However, this 1000 hp plus capacity drive weighs only a mere 75 pounds in cast aluminum construction. This is approximately a 300 pound savings over a competitive racing stern drive unit designed to accommodate considerably less power. For those who may wonder about prolonged use in salt water conditions, Arneson is also prepared to build magnesium bronze or stainless steel versions for maximum corrosion resistance.

As for power trim and steering, it is a highly uncomplicated affair. The single hydraulic ram cylinder, which Arneson manufactures, simply attaches to the upper portion of the transom and to the mid-point of the drive unit just in front of the top stabilizing fin. Inside the hull is the common Prestolite hydraulic motor and pump mechanism which connects to the external cylinder with two small hoses. The approximate total extent of the trim is 30 degrees. Because the unit is mounted so high, a separate lift function is not necessary for trailering clearance. Steering hook-up requires a standard hydraulic system such as a Hynautic or Teleflex. Only a single cylinder system is required and it attaches to the side of the drive unit at the flange boss.

Because of Arneson's desire to keep the unit as streamlined as possible end to maximize reverse gear control, exhaust routing is done through the hull as it would be on a conventional inboard instead of under water via the propeller.

Inside the boat, the Arneson Drive allows the engine to sit low in the hull. In its present form, however, it will cause the engine to locate a few inches more forward than a traditional stern drive. It does offer many more installation possibilities since the drive could be mated with a vee-drive, chain or off-center engines if desired.

Its most widely utilized application is sure to be a conventional marine transmission bolted directly to the engine and then to the drive unit. Versatility again becomes a major consideration since transmission, and gearing opportunities appear limitless. High speed race boats could conceivably use overdrive gear boxes or automotive three-speed transmissions, while large motor cruisers may choose to underdrive for greater efficiency.

Now that you have a better idea of what the Arneson Surface Piercing Propeller concept is all about, here are some first-hand performance impressions of our recent ride on San Francisco Bay in Arneson's test boat. The hull is a standard 18 foot vee-bottom Arena Craft family runabout. Its power comes from a stock 350 cubic inch Chevrolet V-8 marinized by Crusader Marine and is rated at approximately 260 hp. A Borg Warner Velvet Drive transmission provides forward, neutral and reverse gear selection. The hull is also fitted with an electrically controlled adjustable cavitation plate. Propeller selection for the run was a virtually out-of-the-box three blade 14" x 16" Federal Ni-bral brass prop made by Michigan Wheel. Although we were expecting to see some sort of space age propeller configuration, Arneson reported that even though this conventional submerged propeller type was far from optimum for a surface piercing application, it dramatically proved how forgiving his propulsion concept was. Arneson also pointed out that any kind of propeller shaft spline or taper can be provided in order to accommodate a multitude of propeller styles and makes.

Immediately noted at low speed was predictable direction tracking with no tendency for the boat to wander as is the case with some stern drives. At idle, the propeller was just barely covered by water, however no unusual wake or froth behind the boat was created. Steering control was responsive. Maneuverability, both forward and reverse, was outstanding, almost like a jet which will pivot round in its own length. Slow speed turning was noticeably tighter than with a stern drive or outboard.

Getting up on plane was smooth and effortless with very little bow rise. Because of the propeller's close proximity to the surface, the engine tends to rev higher than with a submerged unit. However, this should riot be confused with "runaway" propeller ventilation since the surface piercing prop was efficiently biting water and moving the boat forward. As we eased on the throttle, the tachometer indicated about 3000 rpm as the boat slowly gained speed up to a clean plane.

Giving it more power on take-off brought the rpms up close to 4000 during this brief transition mode and acceleration was rapid. Actually, the ability to have the engine rev easily from an idle is an advantage, especially under a load condition since it allows the engine to enter a more favorable horsepower and torque range. Once on plane and holding a steady throttle setting, rpms decreased as the propeller came into its efficient surfacing condition. Minimum rpm to maintain a comfortable plane was 2400 to 2500.

The most impressive part of the demonstration, however, was its upper end performance. Acceleration from a speed of 25 mph was instantaneous. Utilizing a straight 1:1 ratio, and an inboard cruiser type three-blade brass prop, top speed ranged between 65 to 70 mph depending on trim position of the unit at 4700 rpm. At speed, the boat was capable of hands-off steering and no unpleasant ride characteristics such as chine-walking or poising were experienced.

Water conditions varied from smooth to considerable wind chop and small swells. During that time, the prop never once broke free of the water, a condition which many people falsely suspect as a drawback to the surface piercing concept. The same is true for high speed turns which were performed without a hint of ventilation.

Operation of the trim control is essentially the same as on a stern drive or outboard powered boat. However, from our brief evaluation, it appears that trimming the Arneson Drive causes a less significant change in trim attitude of the hull than more conventional propulsion sources. For general purposes, the Arneson Drive unit could be located at one position and left there for both planing and high speed running. However it would be noted that a full down-angle of the surface piercing drives virtually eliminates the large flowing roostertail which is characteristic of this system. In the down position, recreational water skiers should not experience any interference from the spray off the propeller.

Needless to say, this short demonstration was a rare performance treat. Our preconceived objections to the surface piercing concept were dispelled and all of the anticipated advantages were a reality. As Arneson indicated, propeller development will be a key ingredient in realizing the full efficiency potential of the system which is being worked on by Phil Rolla of Record Propellers, Michigan Wheel and Gary Johnson of OJ Propellers With less unit weight, reduced drag and virtually no mechanical power loss, the Arneson Drive is truly a propulsion breakthrough.

As one might expect, Howard Arneson has recently become a very popular man among the upper echelon executives of the major propulsion companies. In fact most have already sent their top engineering personnel out to inspect his invention which is well protected by patents.

Whether the Arneson Drive is manufactured and marketed by a division of his own company, Arneson Engineering, or it becomes more financially beneficial to join forces with one of the existing marine

propulsion companies, only time will tell. Presently, Betty Cook's Kaama Engineering is assisting in the initial phase of marketing and sales plus providing valuable developmental input. Arneson himself is no amateur in this game since he presently holds eight different design patents and is the creator of the world's most successful automatic pool cleaning device, The Pool Sweep.

Surprisingly, Howard Arneson's educational background is not commemorated with advanced engineering degrees. Instead, Arneson is a true visualizer of mechanical concepts, then proceeds with a direct trial and error approach. He credits many of his invention triumphs to the fact that he doesn't know that something isn't suppose to be done.

Although the development of pool cleaning devices is a far cry from inventing a new marine propulsion system, Arneson's long interest in high-performance power boat racing naturally stimulated his creative thinking. Several years ago, Arneson debuted an open Class l offshore race boat named Sea Sweep. This hull was equipped with what Arneson now considers an obsolete surface drive propeller concept. However, the information gathered from this experiment directly enabled him to ultimately finalize on his new drive system.

To subscribe to this fine magazine follow this link: