Help With Economical Semi-Planing Designs

Discussion in 'Powerboats' started by SAQuestor, Apr 5, 2007.

  1. Pericles
    Joined: Sep 2006
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    Location: Heights of High Wycombe, not far from River Thames

    Pericles Senior Member

    Leo,

    That's the point. Keep it for 5 years after completion. The boat is worth much more with the RCD, especially as it's being fitted with VSD. It is to be sold. http://www.yellowfin.com/media_coverage.asp

    The LB26 is just the first step to a big liveaboard that will incorporate many of my ideas for comfortable living. Of course, if money were no object this is what I'd go for. http://www.vicemyacht.com/v52/gallery.php

    Pericles
     
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  2. u4ea32
    Joined: Nov 2005
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    u4ea32 Senior Member

    Size limits for trailering in USA is actually rather inconsistent.

    However, the absolute limits are beam and height: 8.5 feet wide and 12 feet high. Sure, there are ways to exceed these, generally requiring an inexpensive permit, but the limitations are onorous, including simply not being able to get into most launch ramps if the beam is exceeded (you can't get through the gates where you pay to launch). While the typical legal height limit is 14 feet, if you go that high, you'll be breaking overhanging tree branches with the boat -- a very, very expensive way for you to do tree trimming on public roads.

    The length limit is far more fuzzy. Obviously, to cruise you want the maximum length you can get away with. 35 feet is better than 32, and 40 is better than 35, etc. You can easily get away with a hull length of 40 feet anywhere in the USA. Outboards and pulpits don't count: these are considered "ecoutrements" and are not measured as long as they obviously don't cause a problem. Yes, that's a judgement call.

    In most practical cases, the limit is actually 65 feet overall including the tow vehicle. A big pickup is 20 feet long, so that leaves 45 for boat and trailer.

    If the tow vehicle has a commercial plate, then the US universal highway access law says the maximum length of the trailer that must be acceptable in all juristictions is 53 feet x 14 x 8.5 feet, to allow the use of 53 foot long containers.

    So you can build a really big trailerable boat for the US.

    The weight then becomes in issue, but the weight must be addressed for the goal of this entire thread: efficiency requires light weight, extreme efficiency like people are looking for here requires extremely light displacement.

    If the weight of the fully laden boat on trailer, including fuel, water, stores, gear, etc., is less than 10000 lbs, very many common trucks can tow. 8500 lbs is even better: that gets to nearly every full size pickup truck. 6600 lbs starts to include full sized SUVs.
     
  3. SAQuestor
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    SAQuestor Senior Member

    Cool! :cool: How much does that little ol' drive cost nowadays?

    Nice boat. Lotto's up to 44 million on Saturday. Maybe I'll spend a dollar and take the chance. ;)

    Leo
     
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  4. SAQuestor
    Joined: Sep 2003
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    SAQuestor Senior Member

    David,

    I snipped all that I completely agree with.

    The two points above do not fit with my research.

    Individual states trailering regulations do vary. But federal highways all have the same requirements and as long as you're on an federal interstate highway the legal height limit is 13'6" and legal max width is 8'6" .

    That's why I quoted a max height of <3500mm (~11'5") of the boat from keel to PH roof. That allows ~24" of road clearance for bumps and hollows in the road surface.

    As for width - the boat I want is not one that you'd take to the local lake for a Sunday picnic. So with permits, it could actually be up to 10' wide (in most states) before a pilot car would be needed. Some states go to 10'6" before a pilot car is required.

    Regardless, a max beam of less than 9'6" will allow one to travel most anywhere in the USA with minimal hassles.

    And many modern 3/4 and 1 ton pickups have towing capacities to 16,000 pounds. I chatted with a fellow towing a 5th wheel travel trailer behind a Dodge diesel dually who told me that all up his trailer weight was just shy of 17,000 pounds. Not something that I'm personally comfortable with - but he was and he is not alone.

    Best,

    Leo
     
  5. SAQuestor
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    SAQuestor Senior Member

    A New Member's Boat

    Seems that a new member to boatdesign.net is actually building a semi-planing design.

    Take a look at his photo gallery.

    Best,

    Leo
     

    Attached Files:

  6. Pericles
    Joined: Sep 2006
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    Location: Heights of High Wycombe, not far from River Thames

    Pericles Senior Member

    Leo,

    The Yellowfin option is a complete package, engines, VSDs and controls for straightforward installation in a boat designed for the task. It is not retrofit.

    However, the benefits are smaller engines, because of the efficiency of the VSDs, no bowthruster, no rudders. Thus, if a major manufacturer were to invest in side by side comparisons with two of their hulls, one completed conventionally and the other with Yellowfin VSDs, they will see many savings over the conventionally powered boat.

    You do not have to take my word for this. Page 28 of the August edition of Motor Boats Monthly has a report by Simon Collis. The subject is the latest generation of Volvo IPS technology, but the rationale is valid. The new engines are the IPS750 and IPS850, but as with other IPS units the numbers refer to the HP of an equivalent shaft drive. Thus the IPS600 uses the 435 HP D6.

    The Lazzara LSX-75 is fitted with four IPS600s. This installation weighs 2.5 tonnes less than the equivalent shaftdrive setup As the engines are mounted right aft there is more internal space. Lazzara claim the fuel economy is twice as good as the shaftdrive boat. I welcome the arrival.

    Pericles

    The Southampton Boat Show will see the latest Volvo IPS UK prices revealed. When Yellowfin come to market is not yet announced, but their system will offer another option for enjoying boating without embarrassment (when docking).:(
     
  7. kengrome
    Joined: Jul 2006
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    kengrome Senior Member

    I keep trying to reply but get pulled away every time before I click the Submit button ... :(

    Leo, thanks for the dimensions, they help me to understand some of the features required in the boat you want. I think your numbers would work well for a boat designed to cruise the Great Loop with no more than 2-3 people aboard. I'm hoping to design such a boat with similar parameters to yours.

    Most of my recent design work has been tunnel-stern Seabright skiffs because I really love the way they combine so many features I like into a single boat ... but this new boat is a departure from the tunnel-stern concept:

    [​IMG]

    Here's a link to the full sized image if you want more detail:

    http://www.bagacayboatworks.com/linkfiles/landingcraft31large.jpg

    This boat is 31 feet long and 9 feet 6 inches wide. It still has a Seabright skiff bottom, but it is missing the tunnel-stern portion. That's because my goal here is to create lots of capacity in an easily driven displacement (not semi-displacement) hull while also offering safety when beaching through the surf, sitting stable and upright when landed, and easy loading and unloading via a bow transom that opens downward to become a loading ramp.

    These are special requirements for a special boat -- a commercial mini-ferry with capacity to transport 20+ people and their stuff from one beach to another between the islands. The ability to avoid commercial piers and docking facilities by using local beaches offers a much broader range of transport options than currently available ... and since it wil be built by local shops I want it to be very easy to build thus the reason for the front-rear symmetry.

    As I was creating this design (it is not yet finished) I was constantly thinking of how a similar boat might be optimized for cruising the Great Loop, and whether or not Americans can accept a displacement cruiser for an excursion like the Great Loop. Would you be satisfied to run at displacement speeds while cruising the Great Loop with your mother?

    Jim Michalak says a boat needs one HP per 500 pounds of displacement to move at its calculated hull speed. If this boat weighed 8000 pounds that means only 16 HP would do it. A 16-20 HP diesel inboard is relatively economical to run, but I don't know what the true hull speed might be in a boat like this. I suspect that it will be better than the calculated hull speed due to the boat's fine entry and slim lines ... but does anyone here think this boat would move at 10 mph? Probably not, but it would be nice if it did.

    The two waterlines on the drawings are 12 and 18 inches. The 12 inch waterline is 4600 pounds displacement and the water is not touching the chines yet, so it should still be very efficient at this light loading. At 8000 pounds and 18 inches draft the water is just above the chines in the boat's mid-section, so a bit of efficiency would be lost at this displacement unless the hull were modified -- easy to do at this stage of the game.

    At first I was concerned that this boat's width might be a problem since it is in fact 9.5 feet wide. But if you're correct that it's really no big of a deal to trailer a wide boat like this once in a while, then I don't think this boat's width would bother too many people. It's not like this is a weekend boat so it won't be moved all that often over the highways anyways, assuming it is ever built in the USA ... and if they are ever built here in the Philippines they will never be trailered, that's for sure.

    :)
     
  8. SAQuestor
    Joined: Sep 2003
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    SAQuestor Senior Member

    Mother's ashes are fertilizing the grass at the family cemetery.

    Momma, on the other hand - Nana to the grand kids, and to me SWMBO - Momma - Admiral - Significant Other - is off on her annual summer visit to her mother in NJ.

    Just to clarify that point Ken. :D

    Leo
     
  9. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Much of the loop is 10 Klic speed limit , so most boats putter at 6K , which is economical for almost anything with a bunk.
    Were now at Manatoulin Island , and still only clocking 8statute mph , at about 2 - 2.5 gph.
    Those old detroits siup fuel at 1100rpm, so fuel cost EVEN at $1.25 a liter in Canada isnt a horror.

    FF
     
  10. kengrome
    Joined: Jul 2006
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    kengrome Senior Member

    I don't know what "10 Klic" means, but if you're suggesting that most of the loop is run at displacement speeds, this means my displacement hull is a good starting point for a specialized Great Loop boat. That's good. I'm going to continue developing the above design then. I really like the way the bow transom converts to a loading ramp. For people who like to pull up to a beach frequently, this is a great feature. I will probably convert the stern to a traditional wide transom with an Atkin inspired tunnel too ... so it can be driven a bit faster on occasion.

    Leo, thanks for the info about Momma, you had me confused until I read your explanation of how you use the word.

    Fred, thanks for this too, I think you're "right on" with this conclusion which is why I intend to continue to focus on the tunnel-stern Seabright concept for designing efficient low-speed hulls:

     
  11. SAQuestor
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    SAQuestor Senior Member

    Or I could be like this chap - win the lottery twice in one drawing.

    :D

    Leo
     
  12. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    "Maybe I'll spend a dollar and take the chance. "

    At a dollar a DREAM its pretty cheap ,

    even if the odds are 1,000,000,000 to 1!



    FF
     
  13. SAQuestor
    Joined: Sep 2003
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    SAQuestor Senior Member

    Actually here in Texas the odds are only about 47 million to one in Lotto Texas.

    There was a guy in the NEWS that has been struck twice by lightening, 47 years apart. Lived both times. But I can't find the article right now. Now he beat the odds.

    Best,

    Leo
     
  14. SAQuestor
    Joined: Sep 2003
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    SAQuestor Senior Member

    I >>>hate<<< to post a link to that 'other place' - but in this case I think it is warranted.

    Pictures of an Atkins tunnel stern design for your perusal.

    Best,

    Leo
     

  15. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    AS far as size goes I think the minor loss of interior to get just UNDER 8ft , to fit in Da Box is worth the 8 inches.

    Yes' I know its 8 inches out of a narrow item to start with , but the length of 38ft, if needed, can be pretty comfortable .

    Sitting dead flat, any trailer , not some specialized "Boat Transport" rig could be used.

    A commercial trailer is 40 inches from the ground , so staying inder 13ft 6 inches while loaded wold be not much harder than the 9 ft to fit inside Da Box.

    Biggest hassle I face now is getting used to a propulsion system with lousey reliability. With a std old diesel, once its started you're home free. With the electric crap, you're on the end of a long string , battery ,alternator and some unreliable un-fixable electric box.

    The concept of marinizing a truck engine sounds better and better as spare electric boxes are at the recycle yard ,with not nearly as much markup as at the Marine Pirates.

    FF
     
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