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Old 09-21-2013, 09:42 AM   #261
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If a boat is light for it's length, it will be efficient in operation, no matter what the operating speed or hull form. Ray Hunt's earliest planing deep-vees were rather efficient, throughout the speed range, because they were very light. They had the hard chine above the at rest waterline, unfortunately this also meant they were tippy at rest, so he added a free flooding ballast tank that self-dumped under way. Their waterlines were very fine and the boats could slip along almost as efficiently as any displacement hull at "Hull speed". Not quite as efficiently, but the difference is so small it can only accurately be measured in a test tank with finely calibrated instruments.

No wide and heavy semi-displacement or planing hull would ever be considered efficient in operation, but it may well be very efficient in other ways. As the operating cost increases the market appeal decreases, thus the boat may become a better buy (more boat for the dollar). Especially if you are looking at something with 30 year old V8 or V12-71's....replace those with a nice pair of JD's and have a 12 knot cruiser at reasonable cost.
Somewhat similar to the conclusions I was reaching,...that weight is a very important factor in ANY vessel that wants to plan off, or semi-plan. In some cases even more important than little subtities in hull shape.

It makes me wonder about the claims for much better performance by the Gerr hull shape, the SRD hull shape, the box-keel shapes etc. Are these more exagerated hull forms really that much more speed capable??

Passagemaker Magazine - May/June 2013

SRD is a better hull shape, fast, fuel efficient, stable
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Old 09-21-2013, 10:44 AM   #262
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I hate to be left out and since everyone on TF is "mooning" each other with their bottoms...... take this!

Properly categorized in nautical terms, this hull type is generally referred to as bizarre.

Note: The barnacles are for ballast to reduce roll.

Yo Capt K - What are the handling qualities on boat with that bottom... in various conditions? Sure is an unusual/interesting/unique bottom design for a fairly large boat... I like the entry profile and question closeness of the twin screw. I'd like to see reports from a test tank. Also, are the picts’ shapes at all altered compared to the view if seen by naked eye?
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Old 09-21-2013, 11:40 AM   #263
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Art, Your quite right, it is a bit of an optical illusion. The hull actually flattens significantly as it tapers in and rises toward the transom. Essentially it has a beer belly, the widest, deepest point on the hull is approx midships. It would appear as slow as a slug but unbelievably it topped out at 19 knots during survey.

I have no idea yet how it will handle in rough seas but in 6ft of chop in the Gulf it had the stability of a cement dock, cut nicely and gave a dry ride. It does roll more than I'm used to, but not uncomfortably so.

Regarding the closeness of the screws, it may also be a bit of an illusion. While they may in fact be closer than normal it does not appear unusual when viewed from the stern.

Rough specs are 38 ton, 4'6" draft, 17'6" beam, 50ft, power 750hp
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Old 09-21-2013, 11:43 AM   #264
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Art, Your quite right, it is a bit of an optical illusion. The hull actually flattens significantly as it tapers in and rises toward the transom. Essentially it has a beer belly, the widest, deepest point on the hull is approx midships. It would appear as slow as a slug but unbelievably it topped out at 19 knots during survey.

I have no idea yet how it will handle in rough seas but in 6ft of chop in the Gulf it had the stability of a cement dock, cut nicely and gave a dry ride. It does roll more than I'm used to, but not uncomfortably so.

Regarding the closeness of the screws, it may also be a bit of an illusion. While they may in fact be closer than normal it does not appear unusual when viewed from the stern.

Rough specs are 38 ton, 4'6" draft, 17'6" beam, 50ft, power 750hp
Cool!! - Keep us up to date. TY, Art
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Old 09-21-2013, 11:45 AM   #265
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Re Marks post 259 it can clearly be seen that the transom is completely out of the water.
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Old 09-21-2013, 05:47 PM   #266
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Originally Posted by brian eiland View Post
Somewhat similar to the conclusions I was reaching,...that weight is a very important factor in ANY vessel that wants to plan off, or semi-plan. In some cases even more important than little subtities in hull shape.

It makes me wonder about the claims for much better performance by the Gerr hull shape, the SRD hull shape, the box-keel shapes etc. Are these more exagerated hull forms really that much more speed capable??

Passagemaker Magazine - May/June 2013

SRD is a better hull shape, fast, fuel efficient, stable
Weight and length (waterline) are by far the most important factors in any hulls performance. Much smaller issues are the sectional shape, entry and exit shapes, CP and volume distribution, propulsion effectiveness, appendage drag, etc......

In general claimed superior performance is not real, or may only apply in very limited circumstances. Boatbuilders have been claiming technical advances in search of sales for ever.

I've already stated that the numbers in that Passagemaker article don't make any sense. Perhaps they did back in the time of wishful thinking before Summer Kyle was built. The original published numbers had her displacement at 16000 pounds and top speed 16 knots with 170 HP. In reality she comes in at 22,000 pounds and manages 11+ knots with 220 HP. But it will take more like 90 HP to achieve 11 knots, and not the 60HP that 3 gal/hr indicates. If she will get to 11 knots with 90HP and only tops out at 11.5 (with 220HP), I would suggest this hull would never reach 16 knots even with 500 HP.....Unhappy at speed.

Walter Schulz (SRD) is very cagy about giving out any hard and accurate numbers. He claims the SRD is "the most efficient powerboat on the market at speeds over 10 knots." but of course no numbers are available for comparison with other boats. I did some comparison years ago from numbers published in a magazine review of the SRD38. It was obvious there was no advantage to the form and I could see a standard round-bottom Lobster hull (semi-displacement) of the same length and weight would be as or more efficient.
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Old 09-21-2013, 07:11 PM   #267
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I seem to recall an article in PMM about the SRD and was very taken by it all but never thought of it as being ultra efficient. Level riding, Low wake, probably a very nice ride punching through 3' waves and perhaps level riding at slower speeds too.
Of course it's so far out of my money range even if it did say something about efficiency I probably promptly forgot about it. Besides people that have enough money to buy something like that don't care about fuel burn.
I still think it's a very good design for a medium speed boat as very few venture into that speed range.
I do see it as something far superior to a lobsterboat w a huge following wake and the power lost making it.
Even a FD boat will benefit greatly from weight reduction. As in 25% weight loss = 25% power requirement reduction. So if you can get your GB to weigh half as much it will burn half as much fuel ... and probably be a much drier boat too. That would be nice to watch. A 36GB weighing 17Klbs making 15 knots riding high and proud.
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Old 09-21-2013, 07:34 PM   #268
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The October, 2013 Power and Motoryacht has a short interview with Walter Schultz in regard to the new Shannon "Defiance 46". LOA 45'11'', weight @36,000. The magazine says there will be a complete test in an upcoming issue. The boat has a single Cummins @ 600 HP (or twin 330s) for high speed cruise...plus a 200 HP Cummins driving twin sail drives for low speed. Schultz says the hull is a combination of four hull shapes with reverse deadrise in the aftermost 10 feet. Cruise is advertised as 8-12 knots with top of 17.9.
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Old 09-21-2013, 10:47 PM   #269
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Old 09-21-2013, 11:06 PM   #270
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Those pontoons used as "ballast blow tanks" when the skipper decides to do some submarine action??

Kidding aside... What is the speed and fuel use stats on that monster and how does she handle with those pontoons in some really rough, conflicting seas? I mean 30 to 35 foot close duration seas with wind driven breakers atop... not just some 6 to 8 foot white cap chop atop lazy long duration rollers!
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Old 09-22-2013, 12:48 AM   #271
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Haven’t been in 30/35 foot sea with this boat, but I am ok in 20/25 feet of very confused china sea slop. I have also spent some big sea time at sea anchor which went very well. Loaded with a ton of fuel and a few tons of school books I can run 17 knots at >1 liter/nm. I have lots of data in this 400 mile a day range. At fast Idle the speed is 8 to 10 kts. My floscan is not very accurate at this speed but it’s just sips - it’s hard to get good data off the dip stick and I just haven’t taken the time to set up a proper test. I do know that with the get home (9.9hp outboard) in ideal conditions (light boat flat sea) I can get 6+ knots. I know this type of boat is not for everyone but it fits my needs. I have worked with Chuck Neville on this and other projects and we coined the term “Adventure Platform” for this type of boat. No head room but great air con.

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Old 09-22-2013, 01:33 AM   #272
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Haven’t been in 30/35 foot sea with this boat, but I am ok in 20/25 feet of very confused china sea slop. I have also spent some big sea time at sea anchor which went very well. Loaded with a ton of fuel and a few tons of school books I can run 17 knots at >1 liter/nm. I have lots of data in this 400 mile a day range. At fast Idle the speed is 8 to 10 kts. My floscan is not very accurate at this speed but it’s just sips - it’s hard to get good data off the dip stick and I just haven’t taken the time to set up a proper test. I do know that with the get home (9.9hp outboard) in ideal conditions (light boat flat sea) I can get 6+ knots. I know this type of boat is not for everyone but it fits my needs. I have worked with Chuck Neville on this and other projects and we coined the term “Adventure Platform” for this type of boat. No head room but great air con.
Boatgm

Wow! Thanks for the quick info.

Sounds like you have a robust design that can take some weather while being very fuel efficient. Maybe I missed it on some thread, but, do you have marine architect plans available for review? Any photos underway or at other junctures? Marine magazine article available?

Again, Thanks! – Art

PS: Please forgive me for my light hearted submarine context at beginning of previous thread. I know how dear a personal design can become to her originator! Want cha ta know I was just funnen!
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Old 09-22-2013, 05:46 AM   #273
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I hate to be left out and since everyone on TF is "mooning" each other with their bottoms...... take this!

Properly categorized in nautical terms, this hull type is generally referred to as bizarre.

Note: The barnacles are for ballast to reduce roll.
Never saw a bottom configuration quite like that. I she full displacement, semi-displacement, or planing? She looks like she would be tender up on step.

Never thought of barnacles as ballast, but why not?
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Old 09-22-2013, 07:09 AM   #274
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I know this type of boat is not for everyone but it fits my needs. I have worked with Chuck Neville on this and other projects and we coined the term “Adventure Platform” for this type of boat. No head room but great air con.
Our friend is being exceedingly modest. Check out this link, then tip your hat his way, as I do;

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Old 09-22-2013, 08:40 AM   #275
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Our friend is being exceedingly modest. Check out this link, then tip your hat his way, as I do;

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Amazing boat put to amazingly good use. Thanks for starting my day on a high note.
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Old 09-22-2013, 10:38 AM   #276
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Sherpa has a full displacement hull. I bought her because it is rare to find a FD pocket trawler.
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Old 09-22-2013, 11:41 AM   #277
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Boatgm - Via link provided in other posts... My questions on your truly forward thinking and process inventive boat design have been answered. Congrats... and keep up the good design work!
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Old 09-22-2013, 11:42 AM   #278
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Don, I wouldn't have a clue what you would call the hull, surveyor didn't either. I am however very knowledgeable about barnacles...... the nice thing about barnacle ballast is the minimal effort required to coax the little blighters to stick to the hull. In sufficient quantity they are also useful for giving the diesels a good workout for any given speed.

I join the others in a tip of the hat to Boatgm, it is nice to know there are still such caring selfless people in the world.
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Old 09-22-2013, 02:14 PM   #279
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The October, 2013 Power and Motoryacht has a short interview with Walter Schultz in regard to the new Shannon "Defiance 46". LOA 45'11'', weight @36,000. The magazine says there will be a complete test in an upcoming issue. The boat has a single Cummins @ 600 HP (or twin 330s) for high speed cruise...plus a 200 HP Cummins driving twin sail drives for low speed. Schultz says the hull is a combination of four hull shapes with reverse deadrise in the aftermost 10 feet. Cruise is advertised as 8-12 knots with top of 17.9.
Well if you can't sell a simple boat let's make it really complex and see how that does! Gee this kind of stuff is just silly. Two or three engines and three or four drive systems, and the saildrives run hydraulically? Throw out all that extra crap (expensive crap too) and the boat will be far more efficient at every speed.
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Old 09-22-2013, 04:46 PM   #280
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I join the others in a tip of the hat to Boatgm, it is nice to know there are still such caring selfless people in the world.
I couldn't agree more. I've corresponded with Boatgm off the board and he is definitely ahead of the curve in fuel efficiency and very generous with his time. That reminds me of something I've neglected to do to this point as well, Boatgm please check for a PM from me with my updated email information. There was a change recently and just realized I neglected to inform you of it.
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