Stepped Hulls

[Ryon Macey]

I am currently building an inboard runabout with a stepped hull, and I am in need of some engineering information. Can anyone recommend any texts on the subject of stepped hulls. Thank you in advance for any information.

[Jeff]

There was a discussion on step design in the boat design forum a while back that you might find interesting:
See http://boatdesign.net/forums/showthread.php?s=&threadid=31

This is a subject that it seems a lot of people (myself included) want to learn more about, but unfortunately there just doesn't seem to be a lot of accessible information. In the coming months I hope to present some articles on BoatDesign.Net on the subject, but I haven't had a chance to follow up on a couple of good leads yet.

One of which is that the Florida Atlantic University holds a collection of articles by the late Bob Hobbs on the subject.

22
Robert W. Hobbs
Model Test Results for a Two-Step High-Speed Power Boat Hull Form
R (17)

1
Eugene P. Clement, James D. Pope
Stepless and Stepped Planing Hulls-Graphs for Performance Prediction and Design
W (1)

18
A. M. Lippisch, R. E. Ablton
Stepped Planing Boats, Some Full Scale Test Results
Society of Naval Architects and Marine Engineers, May 1970
R (13)

16
John Teale
Testing Stepped Hulls in America
Motor Boat and Yachting, 12 August 1966
R (11)

17
John Teale
A Step Forward
Motor Boat and Yachting, 15 September 1967
R (12)

10
Robert W. Hobbs
Model Test Results for a Two-Step High-Speed Power Boat Hull From
DD (3)

See http://duedall.fit.edu/zborowski/oe_na_library.htm

[Stephen Ditmore]

In addition to the above and the links in the previous discussion, you might take a look at
http://www.boattest.com/pg-rdrct-script.asp?ID=213
It's largely marketing, but you might be able to glean a useful thing or two.

[Jeff]

For some reason that boattest.com link doesn't work in my browser - it appears the pg-rdrct asp script is only working if I come from http://www.boattest.com/general-info.asp?ID=213 (which doesn't make sense but seems to be the case - though it might just be my browser too.)

I like the fact that Regal (http://www.regalboats.com/) is focusing on technology - a few years ago I thought they had a nice look but didn't really have anything to set them apart - I think they've gained some ground. Nice marketing graphics too at http://www.regalboats.com/fastrac_flash.html (except for the bubbling water which might need a little work :) )

[Stephen Ditmore]

Sorry, it should have been http://www.regalboats.com/rd_fastrac.cfm

Is Regal using a Harry Schoell step or is this their own similar version?

I also found this interesting:

[7] LAMINAR FLOW INTERRUPTERS (LFI'S) Created to provide smoother, safer and more efficient turns, LFI's work just like miniature steps. While the boat is turning, they aerate the bow portion of the hull, reducing drag and bounce. You get superior handling and tracking ability during mid- and high-speed cornering.

I had always thought that steps and aeration were the enemies of good cornering as you wanted the hull to keep a tight grip on the water, not be loose and slide?

[Jeff]

Is Regal using a Harry Schoell step or is this their own similar version?To me Regal's Fastrac hull looks very simiar to Schoell's trademark step design - in fact I was surprised to not see mention of Schoell when describing the step. I did some digging and it looks like there was a lawsuit starting in 1997 over this, and the outcome was in Regal's favor because of the wording of the original Schoell patent revolving around whether a 12 degree hull was "generally flat" or not. There is a note that the Schoell patent was revised to include additional claims and if this is the case I wonder if Regal's Fastrac hull design is grandfathered in... In any case, somewhat interesting reading.

http://www.ll.georgetown.edu/Fed-Ct/Circuit/fed/opinions/99-1511.html

United States Court of Appeals for the Federal Circuit

99-1511

HARRY SCHOELL,

Plaintiff‑Appellant,
v.

REGAL MARINE INDUSTRIES, INC. and EMERALD CITY HARBOR, INC.,

Defendants‑Appellees.

Ernie L. Brooks, Brooks & Kushman P.C., of Southfield, Michigan, argued for plaintiff-appellant. With him on the brief were John E. Nemazi, Frank A. Angileri, and William G. Abbatt.

Brian R. Gilchrist, Allen, Dyer, Doppelt, Milbrath & Gilchrist, of Orlando, Florida, argued for defendants-appellees.

Appealed from: United States District Court for the Middle District of Florida

Judge Patricia C. Fawsett

__________________________

DECIDED: April 17, 2001
_________________________

Before NEWMAN, Circuit Judge, PLAGER, Senior Circuit Judge,* and SCHALL, Circuit Judge.

PLAGER, Senior Circuit Judge.

Harry Schoell is the inventor of a particular boat hull for a planing boat, patented under U.S. Patent No. 5,456,202 (the “’202 patent”). Schoell brought a patent infringement suit against boat manufacturer Regal Marine Industries, Inc. and one of its dealers, Emerald City Harbor, Inc. (collectively “Regal”). On Regal’s motion for summary judgment, the United States District Court for the Middle District of Florida ruled that Regal had not infringed the ’202 patent, either literally or under the doctrine of equivalents. We affirm the judgment of the district court.

BACKGROUND

The ’202 patent relates to boat hulls found in powerboats. Though there are numerous gradations between, boat hulls are divided into two broad categories: displacement and planing. Planing hulls obtain dynamic lift from a combination of hull shape and the speed at which they move through the water. A planing hull is designed so that, at speed, hydrodynamic forces are used to lift a planing hull almost out of the water, thus greatly reducing drag and wave-making resistance, allowing relatively high speeds. Displacement hulls, typically seen on cruising sailboats and large, low-speed powerboats (such as trawlers), get all of their support from buoyancy. They are designed in such a way that, even at speed, they do not rise out of and to the top of the water surface. Once attaining hull speed, a function of waterline length, no reasonable amount of increased power results in any efficient increase in speed. A semi-displacement hull combines round or V-shaped sections forward and flat-bottom sections in the aft run; pushed above hull speed, this design operates partially as a planing hull, but at the expense of increased fuel consumption.

To reduce pounding when a boat is driven at high speeds through rough water, a problem accentuated by the broad, flat sections required of an efficient planing hull, the V-hull has been widely adopted. Boats with such hulls, combining the V-shape forward and flat sections aft, perform well when planing but become much more difficult to maneuver at slow speeds, i.e., at below planing speeds. The ’202 patent describes a planing hull that has a stepped offset between the forward and aft portions of the hull, and a substantially flat or concave aft keel, rather than a V-shaped keel. This configuration purports to provide both stability and maneuverability, both of which are desirable.

The configuration of the boat hull disclosed in the ’202 patent is shown in Figures 1, 3, 4, and 6, reproduced below from Schoell’s opening brief.[1]

As shown in Figures 1 and 3, a stepped offset separates the forward hull section from the aft hull section. The forward hull section has a conventional V-shaped keel, as shown in the profile view in Figure 6. The aft hull section has a substantially flat keel, as shown in the profile view in Figure 4, or a slightly concave keel. The width of the aft keel in the disclosed embodiment is approximately ten percent of the boat’s beam. Substantially flat planing portions extend outward from both the forward and aft keels.

According to the written description of the ’202 patent, the bow (forward) portion of the hull creates a bow wave as the hull speed increases. The wave surges under the hull, causing the stern (aft) portion to ride on the bow wave. The substantially flat or concave aft keel rides on the surface of the water, much like a surfboard or water ski, thereby enhancing maneuverability and efficiency at high speeds.

The ’202 patent has two independent claims, 1 and 17, both of which include a stepped offset between the forward and aft hull sections, a V-shaped forward keel, and “generally flat aft keel.”[2] Claim 1 is representative and reads (key phrases highlighted):

A planing boat hull for planing upon a water surface, the boat hull comprising:

an upper hull, a lower hull, and a pair of laterally spaced chine portions connecting therebetween;

the lower hull including a forward hull and an aft hull and a stepped offset extending transversely therebetween;

the forward hull including an arcuate bow, a V-shaped keel extending from the bow to the stepped offset, and two generally planar forward planing portions extending symmetrically outboard from the V-shaped keel of the forward hull toward the respective chine portions and extending aftward from an apex adjacent the arcuate bow to the stepped offset; and

the aft hull including a stern and a generally flat aft keel extending from the offset to the stern and a pair of generally planar aft planing portions extending symmetrically outboard from the aft keel toward the chine portions and aftward from the offset to the stern;

the stepped offset connecting the forward planing portions to the aft keel and the aft planing portions;

wherein during planing of the hull, the hull planes on the water surface upon the forward planing portions and the aft keel and aft planing portions.

The aft keel limitation in claim 17 is identical to that in claim 1. The forward keel limitation is similar: “the forward hull including an arcuate bow . . . and a V-shaped forward keel trailing therefrom.”

Regal manufactures a boat with a stepped hull design, referred to as the “FasTrac” design. The aft hull of the Regal boat contains a V-shaped aft keel at a twelve degree dead rise angle, i.e., the slope of the bottom sections where they join makes a twelve degree angle with the horizontal, typically measured at the transom. The forward hull of the Regal boat also has a V-shaped keel. Just forward of the step, the forward keel has a twelve degree dead rise V-shape, which angle increases as the keel extends toward the bow.

On September 19, 1997, Schoell filed suit in the United States District Court for the Eastern District of Michigan, alleging that Regal infringed the ’202 patent. After the case was transferred to the United States District Court for the Middle District of Florida, Regal filed a motion for summary judgment of noninfringement. The case was referred to a magistrate judge, who heard oral argument on the motion. In his report and recommendation, the magistrate judge construed the claim limitation “generally flat aft keel” to call for an aft keel that is mostly horizontal. Based on this claim construction, the magistrate judge recommended granting summary judgment with respect to literal infringement. The magistrate judge also concluded that summary judgment of noninfringement under the doctrine of equivalents was appropriate because the only evidence of equivalence submitted was Schoell’s own affidavit stating that he believed there was equivalence based on his tests of hulls allegedly similar to the Regal FasTrac hull. The district judge adopted the magistrate judge’s recommendation in its entirety. Schoell v. Regal Marine Indus., Inc., No. 98-411-CIV-ORL-19B (M.D. Fla. Mar. 30, 1999).

DISCUSSION

In reviewing a district court's grant of summary judgment, we must make an independent determination as to whether the standards for summary judgment have been met. Conroy v. Reebok Int'l, Ltd., 14 F.3d 1570, 1575, 29 USPQ2d 1373, 1377 (Fed. Cir. 1994). We view the evidence in a light most favorable to the non-movant, and draw all reasonable inferences in its favor. Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 255 (1986); SRI Int'l v. Matsushita Elec. Corp., 775 F.2d 1107, 1116, 227 USPQ 577, 581 (Fed. Cir. 1985) (en banc). A motion for summary judgment is properly granted if there is no genuine issue as to any material fact and the moving party is entitled to judgment as a matter of law. Fed. R. Civ. P. 56(c). Summary judgment must be entered against a party “who fails to make a showing sufficient to establish the existence of an element essential to that party’s case, and on which that party will bear the burden of proof at trial.” Celotex Corp. v. Catrett, 477 U.S. 317, 322-23 (1986); see also Fed. R. Civ. P. 56(c), (e).

An infringement analysis requires two steps: claim construction to determine the scope and meaning of the asserted claims, and a comparison of the properly construed claims with the allegedly infringing device or method to determine whether the device or method embodies every limitation of the claims. Cybor Corp. v. FAS Techs., Inc., 138 F.3d 1448, 1454, 46 USPQ2d 1169, 1172 (Fed. Cir. 1998) (en banc). Claim construction is a matter of law over which we exercise independent review. See id. at 1456, 46 USPQ2d at 1174. Whether an accused device or method infringes a claim either literally or under the doctrine of equivalents is a question of fact. Tanabe Seiyaku Co. v. United States Int’l Trade Comm’n, 109 F.3d 726, 731, 41 USPQ2d 1976, 1981 (Fed. Cir. 1997). Thus, on appeal from a grant of summary judgment of noninfringement, we must determine whether, after resolving reasonable factual inferences in favor of the patentee, the district court correctly concluded that no reasonable jury could find infringement. IMS Tech., Inc. v. Haas Automation, Inc., 206 F.3d 1422, 1429, 54 USPQ2d 1129, 1133 (Fed. Cir. 2000).

1.

The principal question in this case is whether the term “generally flat aft keel,” properly construed, encompasses a twelve degree V-shaped aft keel such as the one found in Regal’s FasTrac hull design. The district court construed “generally flat” to mean “mostly horizontal.” Schoell argued that, although deeper V-shapes may not be flat, a twelve degree V-shape was sufficiently shallow to be “generally flat.” Rejecting Schoell’s position, the court noted that Schoell’s written description distinguished between flat-bottomed hulls and V-shaped hulls. The court concluded that, although “generally flat” need not mean “dead flat,” a V-shaped keel could not be considered “generally flat” in light of the distinctions made by Schoell.

On appeal to this court, Schoell argues that the trial court erred by interpreting the term “generally flat” too narrowly. Schoell contends that the trial court did not recognize that the claim language, written description, and prosecution history show that “generally flat” embraces configurations that are not perfectly flat. Schoell further argues that Regal has admitted, in a sales training videotape referring to the aft keel as “flatter” than the adjacent planing portions, that “flat” is a relative, not absolute, term.

Contrary to Schoell’s contentions on appeal, the trial court’s interpretation of “generally flat” was not limited to completely flat surfaces. As the trial court recognized, the word “generally” modifies “flat” and, in this context, means “mostly.” This definition is supported by the written description, which in one instance describes the aft keel as “substantially flat or concaved.” The trial court acknowledged that a “slightly concave” aft keel, as claimed in dependent claim 10, is not completely flat and is within the scope of the independent claims requiring a “generally flat” aft keel.

The trial court also interpreted “flat” to mean “horizontal.” Although that interpretation might not apply in some cases, since, for example, a vertical surface may be flat but not horizontal, we think it is understood that flat and horizontal are synonymous as applied to the keel of a boat in an upright, stationary position. Also, the court’s reference to other reported decisions construing the term “flat” in other contexts is at most harmless error since the court relied on the ordinary meaning and not on any special meaning given to the term in the patents at issue in those cases. In any event, we find the phrase “mostly horizontal” to provide little more guidance than “generally flat” in determining whether a twelve degree V-shaped keel is within the scope of the claims. Thus, we must look further into the record to resolve that question.

Throughout the claims, written description, and prosecution history of the ’202 patent, Schoell distinguished between V-shaped keels and generally or substantially flat keels. In describing his boat hull in the written description portion of the patent, Schoell carefully differentiated between the V-shape of the forward keel and the substantially flat surface area of the aft keel. In the claims of the ’202 patent, Schoell required a V-shaped forward keel and a generally flat aft keel. Furthermore, during prosecution of his application, Schoell responded to the examiner’s rejection of his initially filed claims as obvious over an earlier Schoell patent, U.S. Patent No. 4,193,370 (the “’370 patent”), asserting that “Schoell shows no stepped offset and shows no generally flat aft keel.” Joint App. at 339. The ’370 patent, however, describes a V-shaped aft keel with a dead rise angle between twelve and eighteen degrees. Thus, not only did Schoell differentiate between a V-shaped keel and a generally flat keel, he essentially conceded that a twelve degree V-shaped keel cannot be a generally flat keel as claimed in the ’202 patent.

For our purposes, we need not decide whether a shallow V-shaped keel can meet the “generally flat” claim limitation, or, if so, how shallow it must be. Regal’s aft keel has a twelve degree dead rise V-shape, but a portion of its forward keel also has a twelve degree V-shape. Because Schoell so clearly distinguished between the two keel shapes, a twelve degree V-shape cannot be both V-shaped and generally flat. If Regal’s forward keel satisfies the “V-shaped forward keel” limitation, Regal’s aft keel cannot satisfy the “generally flat aft keel” limitation. Conversely, if Regal’s aft keel satisfies Schoell’s aft keel limitation, Regal’s forward keel cannot satisfy Schoell’s forward keel limitation. Thus, it is impossible for Regal’s FasTrac hull to literally infringe the claims of the ’202 patent.

Schoell’s response to this conclusion is that the claims do not require the forward keel to be V-shaped the entire length from the bow to the stepped offset. According to Schoell, Regal’s twelve degree V-shaped aft keel can satisfy the “generally flat” limitation, and the portion of the forward keel with a deeper V-shape, the portion closest to the bow, can satisfy the “V-shaped” limitation. The claim language itself belies this theory. Claim 1 unequivocally requires a “forward hull including . . . a V-shaped keel extending from the bow to the stepped offset.” The language of claim 17—“the forward hull including an arcuate bow . . . and a V-shaped forward keel trailing therefrom”—is not as explicit, but the application of the adjective “V-shaped” to the forward keel rather than to a portion of the forward keel suggests that the entire forward keel must be V-shaped.

Schoell finally argues in his reply brief that, because Figure 2a of the ’202 patent depicts a forward hull similar to Regal’s with a V-shape that is deeper at the bow and flattens as it approaches the step, Regal’s forward hull must meet the V-shaped claim limitation. This argument, however, ignores the clear distinction between the V-shape of the forward keel and the flat surface of the aft keel in the ’202 patent. Regal does not dispute that its forward keel is V-shaped, but Schoell overlooks the other half of Regal’s position—if Regal’s forward keel is V-shaped, its aft keel cannot be generally flat.

Lastly, we find no merit in Schoell’s argument that “flat” is a relative term and that an aft keel that is flatter than the adjacent hull sections qualifies as “generally flat.” The genesis of Schoell’s argument is a sales training videotape produced by Regal that describes the allegedly infringing Regal hull:

As you can notice, we [have] got the 24 degree dead rise here at the bottom of the hull and more notably right at the keel we’ve a little flatter sectional surface. That is the step-pad. It’s approximately again 12 degrees [and] it provides for lift as the boat wants to come out of the water and at the same time giving stability at high end speeds.

Joint App. at 670 (emphasis added). Nothing in the ’202 patent or its prosecution history, however, indicates that “generally flat” is to be measured relative to adjoining areas. It is undisputed that Regal’s aft keel is flatter than the adjacent planing portions of the hull, but by no means does this lead to the conclusion that Regal’s aft keel is “generally flat” within the meaning of the claims.

For the above reasons, we affirm the district court’s grant of Regal’s motion for summary judgment with respect to literal infringement.

2.

Even if an accused product does not literally infringe the asserted claims of a patent, the product may infringe under the doctrine of equivalents if the differences between the element of the accused product at issue in the product and the claim limitation at issue are insubstantial. Dawn Equip. Co. v. Kentucky Farms, Inc., 140 F.3d 1009, 1015-16, 46 USPQ2d 1109, 1113 (Fed. Cir. 1998). One test used to determine whether differences are insubstantial is to determine whether the element performs substantially the same function in substantially the same way to obtain substantially the same result as the claim limitation. Id. at 1016, 46 USPQ2d at 1113.

Schoell has proffered the following evidence in response to Regal’s motion for summary judgment of noninfringement under the doctrine of equivalents: Regal’s own advertising and sales training videotape touting the stability, handling, and efficiency of the Regal boats; a letter, allegedly evidence of copying, from Regal’s president to Schoell indicating Schoell had shared design ideas with Regal; and Schoell’s own affidavit stating that testing he performed on designs similar to those of Regal’s FasTrac hull “confirms [his] belief that Regal’s boats perform substantially the same function in substantially the same way to achieve substantially the same results” as the claimed invention.

This evidence is wholly insufficient to support Schoell’s claim. At most, Schoell’s evidence may tend to show that the Regal boats achieve performance results similar to the results disclosed by Schoell in the ’202 patent. From the similarity of results, Schoell infers that the boats, particularly the aft keels, must perform the same function in the same way. This is not enough; Schoell has not set forth specific facts showing that there is a genuine issue for trial whether the Regal twelve degree V-shaped aft keel is insubstantially different from the claimed “generally flat” aft keel. See Fed. R. Civ. P. 56(e) (“When a motion for summary judgment is made and supported . . . , an adverse party . . . must set forth specific facts showing that there is a genuine issue for trial.”). Because Schoell bears the burden of proving equivalence at trial, summary judgment against Schoell is appropriate. See Celotex, 477 U.S. at 322-23 (“[T]he plain language of Rule 56(c) mandates the entry of summary judgment . . . against a party who fails to make a showing sufficient to establish the existence of an element essential to that party’s case, and on which that party will bear the burden of proof at trial.”).

The doctrine of equivalents is not a talisman that entitles a patentee to a jury trial on the basis of suspicion; it is a limited remedy available in special circumstances, the evidence for which is the responsibility of the proponent. See Zelinski v. Brunswick Corp., 185 F.3d 1311, 1317, 51 USPQ2d 1590, 1594 (Fed. Cir. 1999) (affirming the district court’s grant of Brunswick’s motion for summary judgment of noninfringement under the doctrine of equivalents because the only evidence submitted by patentee was a conclusory statement by a patent law expert). Accordingly, we affirm the district court’s grant of Regal’s motion for summary judgment of noninfringement under the doctrine of equivalents.

CONCLUSION

The decision of the district court granting summary judgment in Regal’s favor is

AFFIRMED.

--------------------------------------------------------------------------------

* Judge Plager assumed senior status on November 30, 2000.

[1] These figures, taken directly from Schoell’s opening brief, are modified versions of the drawings in the ’202 patent, with extraneous section lines and reference numerals removed and labels added for clarity.

[2] We note that since oral argument was heard in this case, the ’202 patent has reissued as U.S. Patent No. Re36,879. The reissue patent contains twenty-two additional claims. The issues of claim construction and infringement with respect to the added claims were not before either the district court or this court on appeal.

http://www.ll.georgetown.edu/Fed-Ct/Circuit/fed/opinions/99-1511.html

http://www.rbbi.com/folders/pat/regal/regal.htm

[Jeff]

In thinking about it, I'm wondering if I should have posted that since it was a delicate situation and I can see both sides of the case to some extent. In one sense, how broad of an idea should be patentable, and in the other, should semantics get in the way of protecting real intellectual property. But I do find this very interesting, both in terms of step design and also in terms of the protection of design ideas, so I think I'll leave it and hope I don't offend anyone.

[Jeff]

Another thread on design patents (not related to step design)
http://boatdesign.net/forums/showthread.php?threadid=385

[micael]

Hi !

You can look at the design of Ocke Mannerfelt.

I think he has a good design on stepped hull ( he has a design patent on the hull but it can give you some ideers i hope)

you can see it on www.ocke.se


Br
Micke

[Ole]

Hi

I'm a 5.th year student at the Norwegian University of Science and Technology were I study hydrodynamics.

I'm going to design a multistepped (2 or 3 steps) 30 ft. hull and looking for information to deside the length of the surface between the steps, and the "hight" of the step itself.

I guess it depends on the speed of the boat. My boat will operate in the area of 50 - 70 knots.

I'm also interested in different shapes of the step. Does the shape really matter?

Thanks

Ole

[Stephen Ditmore]

I'd advocate a single step forward of the LCG sized so that the planing surfaces are at a 4 deg. angle of incidence at the target speed. After towing models in the canals of Ft. Lauderdale Harry Schoell settled on a step that is radiused looking up at it, like a radiused transom.

Here's a longer explanation:

Like wings, most planing boats tend to generate their best lift/drag numbers at about a 4 degree angle of incidence, and tend to generate most of that lift along the leading edge of the whetted surface area. The problem is that, once into the planing regime, the faster one goes the more the boat lifts out of the water and the farther aft this leading edge moves, altering the trim. A boat without a step relies mostly on the LCG (defined as the distance of the center of gravity forward of the transom) augmented perhaps by trim tabs or a trimmable outdrive unit, to maintain its proper planing angle. For every hull shape and speed there's an optimum LCG, but as speed increases the optimum LCG moves aft.

Stepped hulls have two advantages - they can maintain near optimum trim across a wider planing speed envelope, and the amount of whetted area that is not near the leading edge, and is therefore not producing lift efficiently, is reduced. Boats with a step or two aft of the LCG are achieving this by effectively moving the transom forward as speed increases. The type that Schoell, Morley Smith (fifth "Power Boat Symposium," Southeast Section SNAME, 1993) and I prefer has a single step forward of the LCG, so the running trim is more dependent on the size of the step than on the exact location of the LCG. As Smith points out in his paper, these hulls are at their best in combination with a surface drive, and do not work well with a jet drive since the intake would tend to ventilate.

I think the important issue is optimization of the running trim over a range of planing speeds, and in my experience a single step forward of the LCG works better than multiple steps.

[tom28571]

Stephen,

It's true that a trim angle of about 4 degrees has been found to minimize the combination of wave and friction drag forces. A single step can indeed give a fairly constant trim angle depending on the height and location of the step. That is the good news. The bad news is the same thing. The single step makes the longitudinal stability so high that the boat can not respond to wave action and forces its way through waves. This makes for a bone jarring ride. That is why so few try to build a single step boat for offshore conditions.

I'd also argue that efficiency of the step hull does not depend primarily on maintainiing the optimum trim angle since some other boats can do that pretty well also and are not as fast as the step hull. The single step creates two leading surfaces contacting the water where hydrodynamic lift is at its optimum and makes it possible to use a higher bottom loading factor (lbs per sq ft of bottom contact area) with less surface area creating fricton drag.

I suspect that the use of multiple steps is an attempt to get some of the benefits of the step hull and minimize the increase in longitudinal stability (metacentric radius) which will make the hull more sea kindly.:)

[Stephen Ditmore]

Thanks, Tom. Though I stick by my preference, I think your remarks are an important contribution to the discussion. I differ in that I haven't been convinced that encouraging pitching is the right approach to absorbing wave energy. I would instead favor increasing deadrise. (note: I generally favor a flat "pad" along the centerline, so I'm talking about the deadrise on either side of such a flat.)

[tom28571]

Stephen,

I came to be interested in powerboat design after retiring from a career as an electrical engineer so I'm still very much in the learning stage. From what I see in the literature though, there seems to be very little agreement on planing hull design among the various designers and builders.

For instance, the relationship between keel pads, planing strakes and chine flats. These all seem to have some common goals but which is best and when? Why do you choose pads over chine flats? I think I see some reasons for some circumstances but would like to hear your point of view. I understand your interest in the deep V for its ability to ease the ride in waves while maintaining a fairly high degree of longitudinal stability but this comes at the price of weight, power efficiency, cost and loss of low speed performance. I guess these issues will remain points of discussion and argument for a long time.

Steps are very interesting but seem to be useful only at high speed and suffer terribly at low speed. In waves the side air entry can be blocked and cause lateral accelerations that are uncomfortable at best and dangerous at worst. Some try what they call ram air ducts and some have tried powered air inlets to create a kind of surface effect vehicle.

As far as pure performance at speed in waves goes, I think none of our design preferences can better the powercat in waves.

[Stephen Ditmore]

I'm going to relate what I understand to be Harry Schoell's view in response to your questions, Tom. The purpose of the curved planform of his steps is most likely to bring the step at the chine forward enough that it's immersion is unlikely. It is particularly unlikely if the hull is both high deadrise and on the wide side, so it carries its chine high. Beyond this, he felt (as of 6 years ago) that additional ventilation was unnecessary, based on measuring air flow through small tubes in his models as he towed them to measure bottom pressure.

Harry felt the trim angle should decrease a little at high speeds, and for this reason he uses a centerline flat aft of the chine, but not forward of it. The data I've seen suggests that 4 deg is near optimum at most speeds, however.

Harry also believes that most control problems occur because curvature is immersed forward, and addresses it with his "delta-conic" bottom surface, which puts the straight ruling lines of the developable bottom shape approximately along the flow/spray path.

Harry's typically used spray strakes, but believes that they are far less important than getting the bottom shape right, and I think a number of other experienced designers would agree with him there. Mostly what they do is reduce the bottom area whetted by spray.

My reason for favoring a narrow flat along the centerline is that I think it improves lift and prop flow with a minimal impact on ride (as long as it is not too wide). "Pads" near the stern have become quite common. I favor carrying the flat farther forward.

The issue with cats is getting them to lean into turns. Any thoughts on that?

[tom28571]

Originally posted by Stephen Ditmore


The issue with cats is getting them to lean into turns. Any thoughts on that? [/B]

I don't know much about power cats. Perhaps using the same logic that works with monohulls may help. In a turn with a V bottom monohull, the lateral movement causes the inside half of the hull to stall and lose lift while the outside half creates added lift due to the steep angle of attack. How about making the cat hulls an asymmetric V with the outside part wider and the inside of the V just wide enough to avoid having the hull on the inside of the turn dig in too much.

Multihulls, even more than other boats having very high length/beam ratios, don't turn very well no matter what.

[tom28571]

On second thought, lateral asymmetry of the hull bottoms may not be a good thing on cats. It could cause extra stress on the hull connection by an off vertical force due to the lift of the two sides not being equal. It could also make for steering problems in waves when the hulls receive different lift vectors and there are lateral accelerations because of this.

Another thought that occured is that trim tabs geared to the rudders could add lift to the outside hull and down force to the inside one in a turn. This might result in a twisting moment on the hull and that could be bad . :(

At any rate what is needed is some way to make the outer hull lift more than the inside one, but of course you already knew that.:D

[tom28571]

In the latest Professional Boatbuilder that came today, there is an excellent article on powercats. There is mention of asymmetrical hulls to help the boat bank inward while turning so I guess I was not far off. They don't mention any of the possible negatives that I was concerned about but I'd still be interested to know if such problems exist.

[FRANKIEFRANKIE]

DID YOU KNOW THAT HARRY HAS DONE TWO CATS WITH A SINGLE STEP? ONE IN NEW ZELAND AND ONE IN THE STATES.

[FRANKIEFRANKIE]

I THINK THAT THE REASON FOR MORE THAN ONE STEP IS THAT IF YOU GET A SINGLE STEP THAT WORKS THEN YOU WOULD BE INFRIGEMENT TO THE HARRY SCHOELL PATENT. I AM SURE THEY WILL ALL HAVE ONE STEP WHEN HIS PATENT IS OVER.

DOES ANYONE ALSO KNOW THAT HE HAD THE PATENT ON STRAKES OR LONGITUDINAL STEPS?

[Jeff]

DID YOU KNOW THAT HARRY HAS DONE TWO CATS WITH A SINGLE STEP? ONE IN NEW ZELAND AND ONE IN THE STATES.
If you happen to remember the builders or have a link to their web sites I would love to have a look.

And welcome to the forums!

[FRANKIEFRANKIE]

Thank you.

The one in the US was Caiman Cats. Awesome in the Great Lakes, the turning at that cat at speed (40mph). Do not know if they have a web site, do know that a major boat mfg. was looking to buy the molds for there line.

The other one was in New Zealand in conjunction with Wright-Lavarnos design team for a boat builder named Haines Signature out of Austrialla is promoting that boat. They are also doing a larger one in design now with Harry. They are in the process of building the first one and in design on the second.

Frankie

[Timm]

The earlier comments on strakes and chines reminded me of some things I have been told over the years. When I worked for Bertram in the late 80's, Lee Dana told me they had done some tank tests of their hulls and determined that on large, heavy boats, the strakes provided no benefit. Thus the reason why Bertrams developed during that period had smaller strakes on each new boat. Why were they there at all? Because they were Bertrams and the sales department thought that the customers would have a negative reaction to Bertrams without strakes. We finally did do away with them on the 72, but later design teams (owners?) brought them back. Ask ten designers a question, get ten answers!

Later I worked for Pro-Line and was told By Dan Attwood, the founder of Pro-Line, that when he and his father worked for Glastron in the sixties, they had also tested boats with and without starkes and found little difference. I was designing a twenty footer then and we built it without strakes to make production simpler (a popular saying at Pro-Line was "I saved you ten minutes with that change!"). Such is life at 50 boats a week. I haven't heard any complaints about that hull and in fact it has been modified and used on a number of their models, no strakes have been added.

I personally don't think they add much lift on slower boats, although high performance boats probably benefit due to their reduced wetted surface at speed. I generally use them for spray control nowadays.

[FRANKIEFRANKIE]

Yes You would use them as spray rails and the other purpose is to reduce frontal area. Water will stick and continue to run up a surface until there is something to break it off. This will continue along the entire boat through the different stages. Of course the ones further to the bottom would not do as much on a slow boat as it never gets that far out of the water. And you are right the faster boats will benefit more from this.

Love this.

[FRANKIEFRANKIE]

There is going to be a forum at IBEX-2003, on Stepped Hulls, of which Harry Schoell and two others will be moderators. You might try to make it. Also, a boat with the DDC will be available at the Marriott for a ride.

PM me if you would like a ride.

[FRANKIEFRANKIE]

http://www.bfca.com


Go to the above site click on Publications and look under advisories and click on It's Hard enough to Make Boats.

Makes for some interesting reading.

[Timm]

Interesting reading. The thing that always makes me wonder is how someone can get a patent for something that has been in common existence for many years. Stepped hulls have been around since the early part of this century, had anyone built a single step hull before Harry Schoell? I don't know, but I would guess someone had. This isn't to take away from Mr. Schoell as I find his designs and construction techniques more interesting than most. My understanding is that A.E. Luders designed the first Deep-Vee around 1905, he just didn't have an engine with the required horsepower:weight ratio to get it on plane. This reminds me a little of the current Hinckley Picnic Boat nonsense where they have taken ownership of sweeping sheerlines, tumblehome and C-shaped aft sides of houses. All these things have been common on SF boats for decades, yet somehow they are now claiming to have the rights to these things when used together. We surely have way too many lawyers in our midst!

[FRANKIEFRANKIE]

Yes step boats have been seen as far back as 1905. But the handling charatristics were very bad. It took Harry 20 years towing models to come up with the right geomotry for this step boat to have the best handling charateristics and most efficent plus he can go from drawing board to mold to boat without testing as he did this already in his R&D for the patent. There have been other boat companies trying to do the step but not have the right formula and have to drop the design and just put vents in the chine (ie Wellcraft). I do not see anything wrong with someone getting paid for their R&D to make something better. How about the guy at GM that invented rocker arms? The engine was already built and running but he made it better.

Thanks for the opportunity to discuss these issues.

Harry's patent is a Mechanical Patent and not his only in this field.

[fishboat]

I haven't looked into the step hull patent or history that you're discussing, though I am somewhat familiar with the Hinckley deal.

What I am more fluent in is patents themselves as I've collected a few over the years. Design patents are known to be the easiest to obtain. I'm told all you need is a drawing..not even a working model.

There are three questions that must be answered to even open the discussion on whether to seek patent protection. Is it obvious to those skilled in the art? Is it novel to the art? and Is it useful for something?

I'm guessing you think the step hull or Hinckley deal is obvious and it may well be, but apparently the patent examiner at the USPTO (US Patent & Trademark Office) didn't think so. Any patent can be contested in court, the problem is that it's pricey to do so. Only people/corporations with a big chunk of money at stake will take up the fight. The problem with the obvious clause is that during the patent application examination there is no push-back from people that would claim obviousness(the examination procedure is confidential in the US...not so in EU where applications are published prior to granting the patent)...there is only the patent applicant(attorney) and the patent examiner. Patent examiners are paid by the number of cases they complete....

Is it novel to those skilled in the art? This is a bit tricky in that you can take 5 "things" that are well known & have existed for years and combine them in a new way...if you can make the case that the combination is new (and useful & not obvious), then you've met the criteria & you move forward. Part of the novelty clause is that whatever the new combination that is claimed is, it can't physically exist in the public domain or be discussed in the literature. If you can pull up an old hull or a journal/magazine article discussing the combination then the issued patent may be invalid. If you feel that you have a solid case (seek a patent attorney's advice) you can, & people/corporations do, knowingly "infringe" on the patent with the knowledge that if they are taken to court they have a better then even chance of invalidating the patent. If they aren't pursued for infringement then they carry on. The down side can be that if they are taken to court..and they lose...the costs you'll see will be brutal. You may have to pay all profits you've gained through the infringement to the holder of the patent.

Is it useful for something? This one is easy to meet, usually.

There are strategies of offensive & defensive patents, but that is another whole discussion.

Be advised I'm not an attorney & I'm not suggesting you break any laws..I've just dealt with these issues as a part of what I do for a living.

[Timm]

The Hinckley fiasco is interesting because they haven't patented anything. They are claiming these things are part of their "trade dress" and therefore off limits to anyone else. I have been wondering about their new center console design, which obviously benefits from the years of development the builders of these boats have put into its development. Aren't they infringing on the trade dress of the numerous builders of center console boats? I guess only if these builders have attorneys on staff with nothing better to do with their time. The reason people may be building boats similar to the Picnic Boat is because Hinckley seems to be incapable of producing enough of them at a fair price to supply the market. I am not saying people should copy others designs, but the Picnic Boat is a gussied up lobsterboat, not a unique, new design.

[fishboat]

This sounds like they are trying to differentiate themselves from their competition by trademarking some of the design attributes that make up their boats. The chance of patenting the design is probably zero as the "look" has been around & in the public domain for a long time. A trademark battle may be all they have left in trying to separate themselves from the pack. I'm not a naval architect, but the Hinckleys look quite a bit like many other lobster yacht types. I'm surprised they are winning the argument so far. I can see trademarking a name like "picnic boat", but, as you say, it's a gussied up lobster/cape island hull.

As for the 'trade dress' of other center console mfgs...I'd guess that no one else has been concerned enough to attempt a center console trade dress battle. They may be more willing to slug it out the old fashion way...by offering a good product at a fair price and backing it up with customer service..novel approach.

I hope Hinckley loses their battle...all I see is a willingness to spend money to buy legal protection from their competitors rather than a real design infringement...if their products really are the best or unique, let the market decide.

[gonzo]

The original stepped hulls were designed in the early 20's. They were also quickly banned from racing because they beat anything in the water. The idea was dropped for a long time because of that. They were called "shingle bottoms" then. Some of the old literature is very interesting.

[FRANKIEFRANKIE]

Apparently you have never ridden in a DDC HULL IN ROUGH SEAS OR A DDC HULL on a cat. Go to IBEX in 2003, stepped hulls and go to Schoell Marine.com next week.

[plymouth]

What will you guys be showing at ibex? (if you can say yet)

[FRANKIEFRANKIE]

Harry Schoell will be in an open Forum on the IBEX schedule on stepped hulls.

There could be rides on this hull design for those who book in advance.

Will also be in a booth.

Other than that, I can't say.

[yipster]

http://www.sprucegoose.org/images/fus640-1.jpg

[FRANKIEFRANKIE]

It works.

[trouty]

Re Getting cats to lean into a corner.

Maybe this novel approach is the answer to your quest for a cat that leans into corners.

I'm led to believe this is a 32 ft alloy Fincat - Hysucat foil fitted cat, which has the two outboards mounted tilted (canted) outward each side.

Apparently - this thrust vectoring and the hull design / foil allow the cat to lean into corners like a conventional hull...

Like I said - so I'm led to believe - I may yet be corrected if anyone knows any different.

Cheers!

Very interesting trouty, and awesome pictures of the stern of that boat!

[trouty]

She's a very interesting vessel indeed.

Heres a couple pics of the interior.

http://www.fishingworks.com/Users/UserFolders/trouty/PhotoImages/32%20Alloy%20Fincat3.jpg

http://www.fishingworks.com/Users/UserFolders/trouty/PhotoImages/32%20alloy%20Fincat2.jpg

To my eye at least she's as pretty as most Glass boats of her ilk i've seen.

With her light weigh, and unique foil setup, as well as the canted outboards - I'd be REALLY interested to here figures (speed / fuel) for what she runs with those twin 225 HP's.

My only "possible reservation" with the foil setup - is the chance in waters which have a large lobster fishing industry - of wrapping the double floats of lobster traps around the centre of the foil...

That appears to be the ONLY possible negative I can find and I conceed that in most waters that wouldn't be a consideration most likely.

Affording one might be the only other drawback - I don't know what price they run.

Cheers!

[Tom Lathrop]

Trouty,

Now there are some interesting appendages. I wonder just how they all work. The vertical fin looks like it is only to provide support for the forward foil, and what is that for?

Tom

[trouty]

Take a look at this link,

http://www.hydrospeed.co.za/index2.html

Theres a lot of articles about the foil system and how it works as well as lots of photo's of larger Cat Ferrys employing the technology around the world.

Seems like a winner to all intents and purposes.

Cheers!

[Tom Lathrop]

Yes, I can see how the foils work. About 35 years ago a friend had a pontoon boat that liked to ship water over the bow when in waves. I made a wooden "foil" and placed it transversely under the hulls forward. It did help to lift the bow but there was no instrumentation to tell if the speed was actually increased and insufficient power go very fast anyway. My original question was whether the aft foils were actively adjustable in incidence angle.

Like many other patented inventions, I wonder just how much of this one is actually novel. I expect that past literature holds some references to at least partially similar systems. It is an intrigueing system and from the test data, is very effective.

[trouty]

what I've read Tom, with the Hysucat system, the rear foil 'tabs' are fixed.

I'd imagine having them variable as in a set of trim tabs would be the "ultimate" but maybe a little expensive?.

The foil is placed just forward of the for / aft balance point of the vessel LCG (Longitudinal Centre of Gravity).

The idea being that as the foil rises up thru the water column like an air craft wing, it raises each of the pontoons upward which reduces wetted surface area giving increased speed & / or, reduced fuel consumption.

It's important to cant the OB's to generate a lean INTO the corners, because IF the vessel leaned outward, the inclined foil would have to be "dragged" around the corner against the water direction it wanted to go, rather than being "pushed" around the corner in the direction it does wan't to go.

Think of riding a towed surfboard behind a boat - it's planing on top of the water - when you wan't to turn you lean into the corner, and the water pressure helps to push you around due to the lean...

Now imagine trying to turn that same direction while leaning outward.

When you lean that board outward - it wants to go that direction, this is the "method wakeboarders use to steer their boards first one way then the other, to jump boatwake. I'd imagine we DON'T want our boat doing this - when we steer the helm one way - we wwan't the boat to lean into the turn (not out) and go the way we pointed it.

So - I believe the canted OB's are the reason this foil system turns well - without it I'd imagine it might be a beast to control.

Course this is ALL conjecture on my behalf. Again I'm quite happy to be corrected if someone knows different.

Now to my question...

Could two SMALL foils be fitted between the outside sponsons and central hull of a trihull vortex design to achieve the same results with the consequently reduced risk of fouling ropes and floats, while still gaining the reduced wetted area - fuel speed gains?

Cheers!

[trouty]

Could two SMALL foils be fitted between the outside sponsons and central hull of a trihull vortex design to achieve the same results with the consequently reduced risk of fouling ropes and floats, while still gaining the reduced wetted area - fuel speed gains?

And in addition - would it still heel into corners if you can't the outboards?

C'mon - someone out there must know!!!
:)
Cheers!

[Tom Lathrop]

Ya got me Trouty. I'm still a bit amazed at the speed increase claims for the retrofitted foils. Sure, they can reduce wetted surface some, but can they make that much difference? In addition, the foils will be heavily loaded and generate more drag per unit area than the hull bottom. I guess I'm skeptical.

[yipster]

hydrofoil supported catamaran

someone out there must know
I am sure of that, but not many, and only hope to see more reactions, for -like stepped hulls- this is the better powerboaters stuff.

here my 2 cents of thoughts:

I take it that you mean 2 smaller (shorter?) one side mounted foils bended more backwards to slide trough debris? Guess smaller foils may result in other profiles and surface dimensions, giving other lift and drag sums. The vertical reinforcement struth in the pictured hysucat also explains that shorter and one sided framed foils would need more strenght and support as Tom said.

Seperate smaller foils mounted on the same location may ventilate, miss the deeper going centerpart and -even with the canted outboards i like- may not give good heeling?
The pictured hysufoil is allready so shallow it made me wonder about remaining wave and wsa on the hull versus performance gain.

Autowing (working demo) program at http://www.argo-group.de/service/downloads.php that can be used for foil lift calculations.

:) yipster
some more foil info at: http://www.aae.uiuc.edu/cetan/hydrofoils.html
http://lancet.mit.edu/decavitator/Basics.html

[yipster]

furthermore i remember the wings you could bolt on the drives ventilation plates... no good, they break all said but somehow that way you would get trimmable stern foils.

[yipster]

in PBB magazine #88 an article on the john plum series of stable and efficient stepped hulls.
page 94 shows a design from the author on a V hydrofoil stern stabiliser.
interesting!

[FRANKIEFRANKIE]

Wetted Surface is means nothing in stability. The first thing to look at is angle of attack. Foils are an unnecessary appendage with the right engineered bottom. We just went through this with a customer that was convienced his cat needed foils to increase speed. It did nothing. Why do we keep adding to a problem instead of fixing what we have? Engineer your hull by an engineer with expertise in your boat type. Do not go to a sail boat designer to build a speed boat. Go to people who have tested all hulls and appendages via towing models. Ask them questions. One day these people will be gone and we will think that all that information we have to program computors with came from the computor.

Just my two cents.

Happy boating, Frankie

[Davor]

Try KAFALI method for stepped and stepless hulls.

rgds

Davor

[FRANKIEFRANKIE]

Not familiar with the term but if you mean constant section and straight you are right.

[Frans X L]

My colleque and I have done a few boats using Dr Hoppe's foil system and they definitely work.
You do have to do a costing as to what is cheaper. ie designing and installing a foil system or simply buying bigger outboard engines.

here is Dr Hoppe's own web site:

http://www.hydrofoildesign.com/Default.asp?Page=Home