Breakthru Hull Design...

Eric,

I gave this thread a bump to the top because this is an interesting topic and a very unique hull design. I might be able to add a little on this topic ( ), but I'd really like to get others involved here.

I think the idea of making a hull shape for a certain cruising speed is the good news. The shape itself is seen before, more or less, even a waverider I had was with that concave surface in the back.
Many hulls today carries too much weight, compensated by too much power, which makes them both less seaworthy and less economical.
The rising fuel prices will probably make us develope better hulls, especially hulls that perform well at a given cruising speed.
The Beachboat is a good example.

There was never any form of PWC or jet-ski using a concave hull. It would not work with a jet pump. You may be thinking of a cathedral hull used on Kawasakis, such as the 440, 550, 650 or X-2. This had longitudinal concave sections at each chine, which were designed to add grip in a banking turn.

The Beachboat features a reverse deadrise hull toward the transom. This is actually a unique design. It could effectively produce displacement-hull fuel efficiency, but still have the ability to achieve plane. At displacement speeds, it should offer more stability than a traditional trawler hull form, due to the broad aft planing surface at the rear. At planing speeds, the shallow round section of the forward hull should not displace water outwards enough to negate the ability of the concave section to encapsulate water and channel it under the rear of the hull. Theoretically, the rear of the hull could benefit from the surge created by the bow, adding lift and trim. I think this shape actually works quite well with the natural flow of water.

My only concern would be... I believe this design may be subject to broaching in a following sea. Other than that... it's a design worthy of development.

Theoretically, the Beachboat could have some surface effect properties toward the transom, IF... this is an encapsulated area (hard to tell from the renderings). Surface Effect Vessels are shallow draft hull designs, that are capable of carrying heavy loads by encapsulating and forcing air to travel under the hull. It essentially creates an air-cushion. There is great merit to this design and has been the subject of much research by the Department of the Navy, but it's rough water capability (at speed) is questionable.

The hull looks like a barge, but how the hull interacts with water at planing speeds is quite different from a barge. Air is allowed to pass under the hull and become compressed between the hull and the water's surface, eventually being forced to pass under the submerged sections of hull and exit at the rear. This creates an air cushion and a dramatic reduction in drag. Somewhat similiar to a hovercraft.

Here's an example of a Surface Effect Ship...

Generally speaking, if the hull is not loaded down with excess weight, i.e., built like a tank to sustain enemy fire (see pic above), the hull really shouldn't require all that much power to achieve plane. An airboat would be a good example, except the hull would be inverted (reverse deadrise) to enable compression properties. At idle speeds however, it's got the hydrodynamic drag co-efficient of a barge... and I'm not figuratively speaking.

Again, surface effect has value depending on the application. I don't expect we'll see one leading the field in an offshore powerboat race.

Since I am not familiar with all of these expressions, what would you call the effect an offshore race catamaran is using? Isn´t that a surface effect as well, since it wouldn´t work if it was an airlift effect, I mean vacuum over the wing profile as a plane?

In essence, any kind of high speed cat or tunnel could be referred to as a surface effect vehicle. You could also call a cat a reverse deadrise hull, but in reality (with offshore cats) it's more or less a deep-v, cut in half, creating "sponsons" that are connected by a lifting section. You might refer to this section as a wing, but it doesn't really have the same properties as airplane wing which developes lift by positive pressure under the wing and negative pressure above.

A more appropriate term for the type of craft we're discussing would be a "compression & aeration hull". That being said... most high speed cats work on the same principles! The volumetric area within the tunnel decreases towards the rear of the hull, creating a "compression", thus developing lift. As for the "aeration" part of this combo, it takes place due to ventilation steps on the bottom of the sponsons. This helps break surface tension, thus reducing drag. Essentially, we're discussing different types of surface effect vehicles.

There is a point at which a catamaran coming on-plane acts exactly like the surface effect vehicles were referring to. It's called "tunnel sneeze". This is when the air in the tunnel is being forced back (as speed increases), but the sponsons have not fully developed hydrodynamic lift yet. The result is, the air is compressing and has no where to go, (it can't escape out the rear yet) so pressure builds and finally releases forward and over the bow. It's generally a fine mist of spray that requires cleaning your goggles. It's a major pain with cats.

Carl

It's nice to see our virtual and theoretical thoughts... confirmed. The Beachboat works! The turning (or cornering) ability of this hull was no surprise. With a broad planing surface toward the transom, it can effectively pivot around the deeper, keel section of the hull when turning.

Add jet pumps (or vectored thrust) and hold on!!!

Ocke Mannerfelt Design

I thought I might contribute to this thread. I have been a fan of Ocke Mannerfelt for quite some time now...having even built some of his V-24 and B-28 batboats under the name Armada. But this boat pictured is my absolute favorite design of his...as you can see it is very advanced and state-of-the-art. Ocke is from Stockholm, Sweden...where gas prices are insanely high compaired to here in the US so even his raceboats are designed with fuel economy in mind.

One of our B-28 batboats equipped with a Volvo Penta HP525DPX-HP (engine built by Innovation Marine with 525 horsepower) would run 86 miles per hour (not completely dialed in might I add) and was achieving 3.3 mpg at WOT...three times the industry average...now, not only is that fast and very economical but the boat can run those speeds in 6' + seas with no problem and very safely.

I would love to own this boat featured below, it is a one-off design of Ocke's that I don't have a lot of information on. Looking closely you can see it is a stepped hull design with all the strakes running straight into the bow instead of turning into the keep toward the front...I believe this design makes far more sense than the other as it helps the boat follow into a turn and also creates additional lift through their shape. The steps help to introduce air under the hull which reduces the wetted surface...the boat actually rides on millions of air bubbles like ball bearings making the running surface much more efficient. Too much air detracts from handling and can make a boat dangerous...not enough air and the benefits aren't realized. You really need to understand the running surface and what's going on between the hull and the water.

In addition to hydrodynamics you will see on Ockes website (address listed below) that he has invested significant time in the study of aerodynamics...something that is often overlooked on boats during their design but equally as important. Slipping through the air with as little drag as possible will result in increased fuel economy and range.

When I did testing at the famous but now closed Lake X that was run by Mercury Racing they were extremely surprised that I would venture our prop slip to be under 10%...they thought it would be closer to 12-13 % if everything were running well. It turned out we had a slip factor of less than 7%, which even to me was mind boggling. This I attributed to the extremely aerodynamic benefits of the design...it was a lower slip factor than they had seen on bass boats that they tested which run with very little hull in the water...I explained that I didn't think bass boats were all that aerodynamic and they agreed. This testing was done on the V-24 raceboat which is an enclosed canopy design.

Most of Ocke's boats were designed with the Volvo Penta duo prop in mind...a great outdrive propulsion system with integrated hydraulic steering rams. Testing at Lake X was all done with Mercury drives (in this case the Bravo One) with various lab finished propellers and different X dimensions that were adjusted utilizing a one-off "shortie" outdrive and spacers to make changes to prop height in relation to the transom.

The V-24 was eqipped with a 377 Scorpion which is a small block stroker motor that puts out 350 horsepower...the boat ran an honest 96mph the first week of dialing it in...absolutely incredible by any standards with stock power in a 24' boat. We could have easily reached the century mark (100 mph) with an investment of more time and money...but this was already much faster than were interested in the boats traveling as our One Design Racing Series would include many rookie racers. We eventually dialed our boats into the 82-83 mph range in ideal conditions. What is even more incredible is that our hand layed fiberglass and Divinycell core lamination schedule resulted in boats that all weighed within 30 lbs of each other WET and completely race ready!

I really enjoyed my time building these boats, dialing them in and setting up the racing circuit...selling them was difficult because of their exotic design and single purpose of racing (though a few dot commers had to have them). I lost my BUTT royal in the marine industry, but that's behind me now...I can sit and enjoy from the sidelines and live my lessons already learned!

If you would like to learn more about Ocke Mannerfelt and his other designs including the famous batboats check out www.ocke.se/ I am certain you will be impressed with his designs...from canoes to full blown commercial vessels and everything in between.

Sorry doesn't appear as though my images are uploading...you can see the boats on Ockes site however.

As we are talking about surface effect or in-ground effect vehicles, it is very appropriate to include Ocke Mannerfelt in this thread. While the "Bat Boats" are purpose-built race boats, there is much than can be learned from some of Ocke's revolutionary hydrodynamic development.

If I remember correctly (it's been a few years), Ocke was originally an engineer for Volvo-Penta, before starting his own design bureau. Among his other notable inventions were "Speed Rails", which were aftermarket appendages that could be added to strakes, essentially creating a reversed strake concept. Their purpose was to capture water being displaced outwards and channel it backwards, thus increasing lift... and ultimately speed. THIS is *applied* hydrodynamics.

However, Ocke gives equal consideration to aerodynamics, as evidenced by his B-28 & 24... "winged wonders", as we affectionately referred to them. These designs are another example of surface effect (in aviation, this is referred to as "In-Ground Effect"). With Ocke's Bat Boat's, the line is blurred... are they surface effect or ground effect? Ultimately, it makes no difference. It's the same concept... on different surfaces (water or ground).

The Bat Boats take advantage of the useful aspects of ground effect. The wings not only generate aerodynamic lift, they also add lateral stability at high speed. Stability is accomplished by pressure differentials on each side of the boat, or wings in this case. The wings are creating lift (at sufficient speed ofcourse) that increases or decreases as the wings move closer or further away from the surface (laterally). The result is a dramatic decrease in chine-walking for a v-hull at high speed.

Better explained... if the hull chinewalks, or encounters a lateral oscillation, the falling wing (or side of the boat) encounters greater lift do to the compression of ground effect, while the rising wing receives less pressure. They effectively balance each other out.

The Bat Boat's have great merit in a high speed, v-hull design, but they have one major draw back... how to dock the darn things! Quite simply, they don't mate-up well to docks, but of course they are easily suspended between pilings.

The ride on a Boat Boat is similar to a cat at higher speeds... you truly feel the lift and cushion effect. In certain offshore conditions, it is a better ride, as would be expected with a v-hull. Still... stability favors the catamaran hull. But when it comes to a TRUE drivers boat... I doubt anything can compare. This hull reacts VERY appropriately to trim, throttle and steering (unlike a cat!). If I had my choice for an offshore wavejumping playboat... I would choose one that is challenging to drive and forgiving at the same time. Ocke's B-28 would top my list! Seriously fun boat!!

I've included a couple of images of the B-24 & B-28's for reference purposes. The first image is the B-24 (24 feet) at idle. The next image best conveys the content of this thread... surface effect! The last image shows the wings in greater detail.

Your explanation is correct in how the wings create exceptional "balance" when running at speed and helping to keep the stability of the boat. As stated earlier they were specifically designed with the Volvo Penta duoprop in mind...when things get a little crazy you can simply "wiggle" the steering wheel back and forth slightly and the drive will help to recover any "loose" conditions...aiding the wings.

What you didnt' mention that I find amazing is that when out running hard in offshore conditions...you will always find that rogue wave or "ghost wave" as I like to call them...they typically launch a V-hull boat to the moon dropping the transom as the bow goes to the sky. What's great about the batboats is that they have very little frontal area (they're skinny up front) and don't catch a lot of air...the rear is wide and tends to hold the air well...so they fly extremely level...even off of steep ghost waves.

During testing at the Naval Amphibious Base in Norfolk, VA I was fortunate enough to demonstrate the boats amazing handling with different government branches during the 1999 MACC (Multi-Agency Craft Conference) including countless Navy Seals who were "blown" away at the performance so incredibly I don't think they realized what they had just experienced. I was even fortunate in getting to take a Navy Captain on a test drive and none other than Reggie Fountain of Fountain Powerboats. It was an amazing weekend filled with a rough water playground.

Of all my ventures in the batboats one of the most amazing had to be running out of San Francisco Bay into the Pacific Ocean with Jim Contzen (owner of Hydrostream Powerboats)...we were running in relatively predictable 3-4 footers when suddenly...I mean out of nowhere we were into extremely large swells spaced what felt like 20 yards (this is an exageration of course)...I wasn't certain of what to do and simply remembered Ocke showing me how to run the boat and explaining that when in doubt throttle the boat and trust the design...it will get you out of trouble everytime. That advice has never failed me and since that day I have had quite a few bouts with big water...expected and unexpected. We launched long and hard...just reaching the peak of the next swell and getting back into the throttle just long enough for the DPX to hook up and give us enough power to reach the next...and the next...and the next. I didn't think we would have the speed to carry the last swell but we did...it was mind boggling.

What most people don't realize is that the V-24 is just 4' 9" wide at the waterline on the transom...and stretches to a full 8' 9" wing to wing. Quite a balancing act in a boat that actually only measures 22' on the running surface (the additional 2' are beyond the transom and support the vertical fin). You can throw the boat into any seas and know you're going to get out safely. I have completely submerged a V-24 in the Gulf of Mexico in following seas and lost complete site of any light (by the way the canopy isn't water tight so we took a nice shower) but we emerged running and running strong (over 45mph) What is also notable is that you can go 7' back from the tip of the bow grab the lifeline rail down the center of the top of the deck and reach down around the side and touch the keel...again showing that there is little frontal area which makes it not only aerodynamic when running above the water but also pretty hydrodynamic when piercing waves.

I have always wondered what the boat would do with a surface drive or a semi surface drive like the now gone Black Hawk drive from Mercury. Even Mercury wanted to test the boat with it at Lake X but I wasn't about the foot the bill to test a drive that was no longer available...though it would have been interesting.

You're absolutely right about the wings inducing trim into the hull. The B-28 *does* fly straight and level off waves. The narrow bow, coupled with an abundant surface area under the wings quickly negates bow rise when launching off waves, by adding lift at the transom. The narrow hull (needle-nose) form of the bow offers very little resistence to wind velocity in comparison to the aft section, as the angle of the hull increases relative to the waterline. However, this was one aspect of the design that was not as appealing to me and therefore I didn't elaborate on it. Let me explain...

In a worst case scenario, this is one of the few V-hull craft that "could" be prone to a high speed stuff. It's very simple math. Increased lift at the transom coupled with a lack of displacement/girth at the bow can result in an unwanted catamaran-like characteristic. Newer style cats, with increased sponson girth don't suffer the same effects to the magnitude of older cats, such as the 24' Skater back in the 1980's, which lacked sufficient bouyancy at the forward sponsons to offset wave penetration.

In the case of the B-28, the trim induced by the wings is quite pronounced, as it keeps the boat very level. A little too level for my taste (this is personal). It is remeniscent of Harry Schoell's Duo Delta Conical Hull (or DDC), which utilizes a single step, located at midship, to create a wave surge at the transom. This design is VERY effective at inducing negative trim into the bow. However this hull will never completely "air-out" and runs with a fair amount of wetted surface. (no matter what Pat's propoganda is for Active Thunder powerboats!) The hull simply does not work well for offshore conditions and it is even worse on smooth water.

Ultimately, the Bat Boat needs one appendage to make it the perfect V-hull... an active canard located at the bow. You guys will have to take this up with the APBA!

By active canard, do you mean the "anti-stuffing" wing that is seen on some of the Fabio Buzzi boats (run by the Nemschoffs in the APBA)? I think they would be a nice addition, however in my testing I have found that they may hinder the boats ability to quickly pierce the water and continue through. In the enclosed canopy V-24 you are relatively safe in these conditions, as long as the boat is built correctly and won't hydrolock if water were to enter the front section of the hull (not likely with the "bi-lateral unitized constructioin" a term I coined during our construction where we actually bond the deck and hull together while both parts are still in there molds...we used a product called Plexus which cross links the two fiberglass components and then glassed the inside and outside seam 360 degrees around the perimeter of the boat...giving it an almost bulletproof hull.

In the B-28 you are a little more at the mercy of the forces of the water during the stuff...water rushes over the deck and if you're lucky your crew thoroughly bolted the windscreen on with adequate hardware, something I learned was crucial after my first experience stuffing the boat. Once we even bent the aluminum tubing and shattered an acrylic windshield (purchasing agent made a mistake bringing in the acrylic rather than the polycarbonate). Nothing too serious but nonetheless was an intense incident. Another time during testing on Government Cut in Miami during the Miami Int'l Boat Show a slower speed stuff (approximately 40mph) resulted in the polycarbonate windshield (this was a half canopy design like you images of the B-28 running) flexing inward and allowing water to get under the canopy roof (permanent mount) and ripped it off the boat.

We later made removeable canopies that were actually attached better than the permanent windshields which were also better supported and made of a thicker material. We learned that we needed to use a pressed polished polycarbonate in lieu of standard polycarbonate as it didn't show the roller markings in the polycarbonate from the extrusion process when the polycarbonate was laid back at a severe angle....this took some research to learn and made visibility out of both boats (the V-24 and the B-28 far better).

I personally preferred the B-28 with a windscreen in lieu of the half canopy or the inline racing configuration...we built the inline hulls too but simply shipped them unrigged to Europe for UIM racing. The B-28 was banned from APBA racing due to it's dominance during it's first year racing...right along with the Buzzi RIB.

As for the boat flying level, I felt this was an extreme advantage, particularly in the V-24 which had limited visibility in the full canopy boat to begin with. But the B-28 flew extremely level in almost all conditions and simply wasn't prone to "tripping up" when it hit the top of the next wave or swell...I'm sure it could happen but it was very uncommon.

It was really different to run hard, hit big water and each time the boat launched you never lost vision of the horizon...this too meant that the boat, in flying level, was not scrubbing off the speed that the "moon shot" conventional V-Hulls were when they hit transom first and then slapped the rest of the hull down later...particularly with the older boats like the Apache's and Cigarette's that were heavy to begin with and had the majority of their weight in the engine compartments with the big horsepower engines (read: unreliable and expensive) that were required to propel these boats to just average speeds by todays standards.

If any of you ever get the chance to run in a batboat I would suggest you take full advantage of it as it will be something that not only won't you forget but more than likely will not believe once your feet are back on the dock.

Ahhh... Plexus! NASA's JB Weld!! I don't know what's more hazardous... the vapors from that stuff or dating in the 90's.

On the active canard, it's a small wing on each side of the forward section of an airplane fuselage, usually found on rear wing pushers, such as the homebuilt LongEasy airplanes (Rutan design). These are control surfaces that can be activated via a high speed servo and piezo (or similar) gyro. Basically... fly-by-wire technology. Ohh!! I just remembered, Lars added some canards to the rendering on this thread. Look closely at the forward section of the 2nd rendering...

http://www.yachtforums.com/forums/showthread.php?t=1975

I can relate to being a test dummy and the laughter that follows. Been there... not much wiser from the same. It seems we've travelled the same waters, but never crossed wakes. If you ever got down to the land of heat & humidity, I'll buy the first round.

Carl Camper

I'll be down for Bike Week in March, but not as far south as Lauderdale. We're displaying some product (aluminum trailers) at the speedway.

My worst test dummy experience was out of Lake X on a very hot and humid day. We were testing the V-24 for the first time with a Bravo One drive and the Scorpion Motor. Well, as it turned out, to dial in the X dimension and the right propeller they asked me to run the boat, watch the GPS and monitor a handheld scan tool that was telling me precise RPM. The boat turned out to be more than a handful at WOT (set up the way it was she was running in the mid 80's) The boat would just get wild right at top speed...violently kicking from side to side...the narrow beam really made it feel like it was worse than it was...but I was thinking I was bouncing the wings off of the water from side to side. You couldn't just chop the throttle as I felt like it might flip on me, so I had to ease off the the throttle until it settled down. I went right back in and they decided to try a four blade prop (in lieu of the three blade) and see if this would set her up better. Same thing happened, and although I was ready for it to happen this time, it still scared the **** out of me. After going back and forth with a few different props and no fix to the problem we were talking with Dennis Cavanaugh (who has since passed away) the prop guru at Mercury...he suggested raising the X dimension by removing the spacer in the shortie drive...I was thinking this would free the boat up and make it more likely to repeat but with a more tragic outcome. Well...I was as wrong as could be...the higher we raised it the faster she got (which I expected) but she also handled better and the violent bucking left the boat. Even turns at high speed were extremely predictable...not like with the Volvo Penta Duoprop (which was like running on rails) but it was a lot of fun. In the end while I enjoyed both setups (the Merc and the Volvo) I preferred the Volvo setup...the Bravo was more demanding and not as forgiving, definitely a drivers boat...but the Volvo was like put the throttle forward and run off the rev limiter...she could handle it all and any small mistake didn't get amplified into a major mistake.

On the flip side I can tell you that Mercury's customer service was second to none while Volvo Penta of North America was a complete and total joke...no service, no technical help...nothing...especially if you were having problems. The only exception to this and it must be noted was Ed Szylagi...he was fantastic, knew his stuff and was always glad to assist...he had a special interest in the batboat and I think he was excited to see Volvo show at least some interest in the high performance program.

You should have seen the faces on the Volvo execs when they came into our booth at the IMTEC Show in Orlando and we had a Bravo One hanging off the transom with Mercury Racing decals all over the boat...they flipped out and were actually yelling at us. But when it came time to pony up for the racing they just didn't have any interest and they lost their chance...worse they were dethroned by Mercury as our exclusive choice of power. I don't think they actually thought we would convert but we had just invested a large sum of money in the program on a single purpose raceboat...so either they were with us or not. It was their choice...we even offered to pay the entire homologation fee that the APBA was demanding from us to allow a One Design Series. It was a no lose, no investment program for them but they were simply too dense to see it.

Oh well...that ran from test dummy to dealing with dummy's...I should write a book on my adventures, who knows I might sell ten copies!

OMD

I was finally able to get my program running where I can resize some images so they fit on the server...here's the Ocke Mannerfelt Design I was talking about, I think this is one of the best looking boats I've seen...if the performance and handling are anything like I expect this would be one amazing boat. Flying the American flag, I wonder if it was built for an American owner, I would love to see this boat in person and possibly drive it.