Page 1 of 3 12 ... LastLast
Results 1 to 35 of 102

Thread: A neat fuel efficient launch

  1. #1
    Join Date
    Dec 2001
    Location
    Northern NSW Australia
    Posts
    71,330

    Default A neat fuel efficient launch

    Well open fishing boat . Greta by Nigel Irens .

    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  2. #2
    Join Date
    Dec 2001
    Location
    Northern NSW Australia
    Posts
    71,330

    Default Re: A neat fuel efficient launch

    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  3. #3
    Join Date
    Mar 2011
    Location
    Mukilteo, WA
    Posts
    1,722

    Default Re: A neat fuel efficient launch

    Wow that second vid is something! I enjoyed the article, but seeing the video really does it justice.

  4. #4
    Join Date
    Oct 2000
    Location
    Padanaram, MA USA
    Posts
    9,409

    Default Re: A neat fuel efficient launch

    Numbers please!
    LWL, Beam, Displacement, HP, speed?

  5. #5
    Join Date
    Jan 2010
    Location
    Northern Europe
    Posts
    9,076

    Default Re: A neat fuel efficient launch

    I think this got its first heads up in the Low horsepower planing boat thread......

    long...thin...light....Beta 14hp....

  6. #6
    Join Date
    Dec 2001
    Location
    Northern NSW Australia
    Posts
    71,330

    Default Re: A neat fuel efficient launch

    Quote Originally Posted by JimConlin View Post
    Numbers please!
    LWL, Beam, Displacement, HP, speed?
    Jim, I couldn't find any but I've been told it's in a recent WB, one i haven't seen here in the boonies yet.

    A friend who is occasionally involved in workboat design / construction for a group of isolated pacific islands drew my attention to it. He feels it might be a good and cheap to run substitute for an outboard power craft .... if it could be modified so the owners could just run it up onto the sand .

    Discussion moved to tunnel props and Recue Minor , that might work.
    Last edited by PeterSibley; 01-13-2015 at 09:29 PM.
    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  7. #7
    Join Date
    Apr 2009
    Location
    Mountain lakes of Vermont
    Posts
    10,670

    Default Re: A neat fuel efficient launch

    Quote Originally Posted by JimConlin View Post
    Numbers please!
    LWL, Beam, Displacement, HP, speed?
    In the latest issue of WBM. 26' LWL, 7' beam, doesn't mention displacement, 13.5 HP, close to 14 knots speed.

    Ugly looking thing, though..
    I was born on a wooden boat that I built myself.

  8. #8
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
    Posts
    44,971

    Default Re: A neat fuel efficient launch

    Notice how the bow and stern waves cancel. I don't know if that really shows anything about efficiency but it's sure pleasant for the rest of us.

  9. #9
    Join Date
    Apr 2009
    Location
    Mountain lakes of Vermont
    Posts
    10,670

    Default Re: A neat fuel efficient launch

    Quote Originally Posted by Ian McColgin View Post
    Notice how the bow and stern waves cancel. I don't know if that really shows anything about efficiency but it's sure pleasant for the rest of us.
    The guy really works wonders with the design. It's a displacement boat, but somehow gets twice the theoretical hull speed.
    I was born on a wooden boat that I built myself.

  10. #10
    Join Date
    Mar 2007
    Location
    East Quogue,NY
    Posts
    15,381

    Default Re: A neat fuel efficient launch


    Built of lightweight 9mm epoxy ply, Greta is an easily driven motorboat from Nigel Irens – best known for his world-beating trimarans. On a trip to Fowey from the Dart, we noted: “Against foul tide, it took 5h 40m averaging 9 knots, using 13Lt of fuel.” What more could you ask of a mobo?
    LOA 26ft (8m) BEAM 6ft 6in (2m) DRAUGHT 1ft 10in (0.6m)

    Google it

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  11. #11
    Join Date
    Nov 2007
    Posts
    4,992

    Default Re: A neat fuel efficient launch

    The relatiive speed a hull can go is broadly determined by its length to displacement ratio or slenderness ratio. My 20ft lwl sail and oar boat i'm working on has a predicted 'hull speed of 15 knots theoretically if it could be pushed that hard, and might do 9.5 knots with the added weight of a Honda 2.3.

    I'm not an expert, but primarily its because the hull is light, the LWL long and bwl narrow that its efficient. Building it Occume plywood gets the weight lower than if it was GRP and its cheaper to procure as a one off. Foam carbon vacuum epoxy would be even lighter but unduly more expensive in materials and labour. No doubt he's picked the optimum prismatic to help it at "hull speed", entry angle etc also, got the engine at the lcb and calculated the right props etc. He's probably got the speeds the stern wave is getting attenuated by the bow wave to know when his wave resistance is a little less also writen on the back of his hand. If that ties in with an efficient diesel rpm then so much the better.

    The only thing I'd have done different would be to rake the stem forward so that you maintain the same sharp fast entry angle but also gives flare for a drier ride. With a straight stem and sharp entry carried to the gunwale you can't have flare and get a wetter boat. He's the expert though and that's west country style where its kept.

    There was an article on this boat in Watercraft a while back for anyone interested. Irens had a local shipright build it, for himself. Knowing the actual weight of the finished boat probably gives him a good data point for future development.

    Compared to a sailing boat hull, Greta is free from sail carrying stability restrictions: her bwl can be narrower and she's not carrying the extra water displacement of any keel weight or drag.

    As a hobby line fishing boat it would be great, as a commercial fishing boat, you would lose the starting speed and efficiency if you anticipated loading it right up. Just some thoughts.

    NA's played this game a hundred years ago to get speed when engine power was very limited. We then went through a phase of much more power availability which could mask any ineffeciency and now are going back to that point to limit environmental impact. The availability of light materials and techniques should mean we can build even lighter launches for a given length and couple them to more fuel efficient powerplants so they are even better performing than they were 100 years ago. Of course every third world boater wisely never stopped playing this game either.


    Ed
    Last edited by keyhavenpotterer; 01-14-2015 at 05:33 AM.

  12. #12
    Join Date
    Dec 2001
    Location
    Northern NSW Australia
    Posts
    71,330

    Default Re: A neat fuel efficient launch

    Quote Originally Posted by PeterSibley View Post
    Jim, I couldn't find any but I've been told it's in a recent WB, one i haven't seen here in the boonies yet.

    A friend who is occasionally involved in workboat design / construction for a group of isolated pacific islands drew my attention to it. He feels it might be a good and cheap to run substitute for an outboard power craft .... if it could be modified so the owners could just run it up onto the sand .

    Discussion moved to tunnel props and Recue Minor , that might work.
    What do you think of it for this use Ed, fishing and transport ?The fuel efficiency of a decent hull, a small diesel versus an aluminium skiff and a 20 hp outboard could work out well. Fuel is expensive in Kirabati ... the old Gilbert Islands .
    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  13. #13
    Join Date
    Oct 2006
    Location
    Livin' in Oz
    Posts
    56,024

    Default Re: A neat fuel efficient launch

    It is of similar dimensions to the banana boats that I've seen up in PNG. They are frozen snot up there, powered with outboards, but they scoot along nicely. Random pics from the web



    "Travel is fatal to prejudice, bigotry and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome and charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime" Mark Twain... so... Carpe the living sh!t out of the Diem

  14. #14
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
    Posts
    44,971

    Default Re: A neat fuel efficient launch

    They are similar to the extent that they are both long and narrow. Southeast Asian boats indeed have a superficial resemblence to Irens' shape but a glance at the wakes, even when the banana boats are running light, shows the profound differences. The banana boat shape is a long planing hull. Iren's shape does not try to get up on a step. The banana boat sticks her bow in the air with speed. Irens' hulls don't.

  15. #15
    Join Date
    Jan 2000
    Location
    Cushing, Maine
    Posts
    3,358

    Default Re: A neat fuel efficient launch

    When you look at pics of older lobsterboats running at speed they look pretty much what Nigel is doing. The boats that ran with one lungers had weight and horsepower problems, but once you got to auto conversions, you got good power to weight ratios. Early 1960s boats were still slim; once the trap count got up above a couple of hundred things changed.
    Ben Fuller
    Ran Tan, Liten Kuhling, Tipsy, Tippy, Josef W., Merry Mouth, Imp, Macavity, Look Far, Flash and a quiver of other 'yaks.
    "Bound fast is boatless man."

  16. #16
    Join Date
    Oct 2001
    Location
    Flattop Islands
    Posts
    2,217

    Default Re: A neat fuel efficient launch

    Greta's full load displacement is somewhere around 1600 pounds. A displacement/length ratio of about 40. That length and light weight is where her performance comes from. This reminds me of Robb White's Rescue Minor, people seemed to think the odd bottom shape somehow imparted magical performance when actually it added drag. The real secret is ultralight weight and then the bottom shape almost does not matter. But one has to give up most comforts we expect in boats to achieve and maintain that weight target.
    ___________________________________
    Tad
    cogge ketch Blackfish
    cat ketch Ratty
    http://www.tadroberts.ca
    http://blog.tadroberts.ca/
    http://www.passagemakerlite.com

  17. #17
    Join Date
    Dec 2008
    Location
    Maitland, Nova Scotia,
    Posts
    451

    Default Re: A neat fuel efficient launch

    How fast and efficient is it when you put a load on it, say 12 people? I'm guessing you don't see 14 knots and the same fuel burn.

  18. #18
    Join Date
    Nov 2007
    Posts
    4,992

    Default Re: A neat fuel efficient launch

    Flicr photo set here of Greta on her trailer so you can see the hull form in much more detail

    https://www.flickr.com/photos/charli...7644351975853/





  19. #19

    Default Re: A neat fuel efficient launch

    Quote Originally Posted by TR View Post
    .... But one has to give up most comforts we expect in boats to achieve and maintain that weight target.
    Thanks Tad for this statement.
    Nigel Irens work in honor... good performing boat. Just a bit puristic.
    I'll throw in a dutch counterpart at this point. Not lightweight and not so efficient for sure - but therefore with all the nice and comfortable widgets on board.
    And believe me: these boats cut through a chop like knives.



  20. #20
    Join Date
    Apr 1999
    Location
    Hyannis, MA, USA
    Posts
    44,971

    Default Re: A neat fuel efficient launch

    All depends on what you want. Granuaile had such a slippery narrow hull that her 15KW Deutz could move her 20 tons (average load for a month) at about 6 knots burning maybe 2/5ths per hour. You can burn lots more either upping the power to push 9 knots, or going to a planing hull but the point is that there are only so many ways to defeat "hull speed" and the two biggest after you make a skinny hull are more power or less weight.

    As some of the larger boats of this general model show, you can make a terrific cruising power boat with all the amenities one could use within the constraints of the weight restrictions. Just read the WoodenBoat Magazine article, especially the part about a rough passage over to Ireland.

  21. #21
    Join Date
    Nov 2007
    Posts
    4,992

    Default Re: A neat fuel efficient launch

    Nigel Irens has been working in this area of low drag efficient power boats for quite a while. I think Greta was a development opportunity.

    see the wonderful short video of Molly Ban here http://www.nigelirens.com/boats/power-boats/molly-ban

    and his latest radical 43' design here http://www.nigelirens.com/2014/ocean...-cmn-cherbourg

  22. #22
    Join Date
    Nov 2007
    Posts
    4,992

    Default Re: A neat fuel efficient launch

    I wouldn't sully efficient with extreme. She's built of wood has good freeboard and cheap diesel engine and a nice look. She's even fitted out with tanks and flooring etc.

    She's not at the apex of efficiency either if you don't mind the mooring fees...

    If she's 800 kg designed displacement, with a single helm aboard we have a boat weight of 715kg. Her optimum length if we wish to run at semi displacement speeds and have minimal hump, is 36'7" with a beam WL of 5'2.5". She'd have a DL ratio of 14.7 and an SL ratio of 3.58. If we gave her a < 2 degree quarter beam buttock angle to match that SL ratio we could expect or predict speeds of 21.7 knots. To get this speed she should get it with the three cylinder low vibration Vetus 27hp triple. The engine weighs 134 kg, so everything else will have to be built to weigh 666kg to sit at optimum. You can go narrower limited by human scale, practicality and stability for its function but resistance doesn't increase provided you don't go bwl wider.

    You can work it all backwards from a starting point of weight or length. It comes down to achievable construction weights fundamentally. There is optimum lcb and prismatic for the hump region but at lower and higher speeds they matter less, and the longer and lighter you make it the less resistance increases if they aren't perfect.


    Ed
    Last edited by keyhavenpotterer; 01-14-2015 at 05:01 PM.

  23. #23
    Join Date
    Jan 2010
    Location
    Northern Europe
    Posts
    9,076

    Default Re: A neat fuel efficient launch

    Nice post of the Greta on the trailer pics, thanks. I had been wondering about her underwater shape since i first saw her.

  24. #24
    Join Date
    Mar 2007
    Location
    East Quogue,NY
    Posts
    15,381

    Default

    I've had a number of experiences to run similar/ same model boats -- one infused or bagged ; the other conventional FRP layup ( heavier )

    The lighter boats were good seaboats but not as good as the heavier boats. They heaved too fast and were corky. Efficiency and speed superior .

    Hear what I said : the light boats were good seaboats and more efficient. The heavier boats are better seaboats-- hard to put a price on that once you've experienced it.

    Kevin

    Sent from my iPhone using Forum Runner

    edited
    Last edited by Breakaway; 01-15-2015 at 01:23 PM. Reason: typo
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  25. #25
    Join Date
    Nov 2007
    Posts
    4,992

    Default Re: A neat fuel efficient launch

    I agree entirely Kevin: two boats the same length and shape then the inertia of the heavier boat will make it more comfortable.

    Motion comfort can come from displacement, but it also can come from length and form: a 36ft 800kg boat will be more comfortable than a 20ft 800kg boat running through inshore chop: it will have much more pitch damping. It's immediately apparent in a long double ender compared to a shorter boat of the same weight, as the sail and oar crowd find.

    Given that a wave and wind condition we want to run in, is a mathmatical constant, we would simply need to understand the adaquate displacement that provides sufficient inertia to reduce heave for that condition, then build it long and lean in proportion as we can to reduce pitching, and control its form to assist us, for instance less asymetrical reserve buoyancy fore and aft.

    Alternatively if we know that length gives us an added motion comfort, then we can reduce displacement by an equivalent factor and have the same motion comfort, as shorter heavier boat, and have a cheaper boat in material weight.

    Its mooring fees, haulout fees and mooring space for longer boats that has prevented naval architecture going in this direction in the western world I think.

    Its all self imposed, not imposed by the sea: so its arguable that the resulting shapes and proportions are unnatural. Africa, Asia and South America are more free to build em long and lean.

    If payments were reformed to displacement and not length LOA the direction of NA would change in a switch but if we all had longer boats, there would be less space to store them all, so there would have to be fewer boats on a given river or harbour space. So for the same revenue the fees would have to be higher per boat...so by default if us peasants want to go boating maybe we have to accept short and fat boats come with population density?

    Edward
    Last edited by keyhavenpotterer; 01-15-2015 at 08:34 AM.

  26. #26
    Join Date
    Dec 1999
    Location
    Oriental, NC USA
    Posts
    4,624

    Default Re: A neat fuel efficient launch

    Quote Originally Posted by TR View Post
    Greta's full load displacement is somewhere around 1600 pounds. A displacement/length ratio of about 40. That length and light weight is where her performance comes from. This reminds me of Robb White's Rescue Minor, people seemed to think the odd bottom shape somehow imparted magical performance when actually it added drag. The real secret is ultralight weight and then the bottom shape almost does not matter. But one has to give up most comforts we expect in boats to achieve and maintain that weight target.
    People looking for magic in either this boat or Rescue Minor should read this over and over until it registers.
    Tom L

  27. #27
    Join Date
    Nov 2007
    Posts
    4,992

    Default Re: A neat fuel efficient launch

    Quote Originally Posted by PeterSibley View Post
    What do you think of it for this use Ed, fishing and transport ?The fuel efficiency of a decent hull, a small diesel versus an aluminium skiff and a 20 hp outboard could work out well. Fuel is expensive in Kirabati ... the old Gilbert Islands .
    Peter, from what I understand and can calculate if her designed displacent is 800kg, and you built her the same, there is 245kg extra weight further to that you can add before her hydrodynamic resistance starts to rise exponentially: at this point the Slenderness Ratio drops below 7. If she could be built to her optimum length of 36'7" on that weight, you could add 364kg before you start losing hydrodynamic efficiency more quickly due to disproportionate increasing wave resistance for the boats displacement.

    Exactly what the empty boat weighs excluding passengers I don't know, but effectively you could expect to overload Greta with 3 extra people in addition to the number of passengers Irens designed into the estimate of 800 kg designed displacement and not lose much efficiency. Beyond this weight her speed will decrease progressively until she becomes sufficiently heavy for her length (when she displaces 1.8 tons) to become 'trapped' at 'hull speed' (6.9 knots) and with an incorrect prop.

    Greta's form is thus ideal for carrying a small group of people, let's say a water taxi or commuter, over a considerable distance (when a displacement boat would take too long) in conditions to rough for a planing boat.

    Edward
    Last edited by keyhavenpotterer; 01-15-2015 at 04:20 PM.

  28. #28
    Join Date
    Dec 1999
    Location
    Oriental, NC USA
    Posts
    4,624

    Default Re: A neat fuel efficient launch

    Quote Originally Posted by keyhavenpotterer View Post
    Greta's form is thus ideal for carrying a small group of people, let's say a water taxi or commuter, over a considerable distance (when a displacement boat would take too long) in conditions to rough for a planing boat.

    Edward
    Built this light and with the same hull form, would she pass the USCG stability requirements for a water taxi?
    Tom L

  29. #29

    Default Re: A neat fuel efficient launch

    Now that's what I'd call a market niche ;-)

  30. #30
    Join Date
    Aug 2011
    Posts
    913

    Default Re: A neat fuel efficient launch

    I don't know but build one here and if anyone asks if rcd compliant just mention the designers name and they will walk away without asking any more questions!!
    james

  31. #31
    Join Date
    Nov 2007
    Posts
    4,992

    Default Re: A neat fuel efficient launch

    As we've all pointed out, the efficiency comes from the lwl length to displacement ratio and beam to length ratio that allows progression into semi displacement speeds. People on Kirabati would lose the efficiency if they treat her as a ferry and with all that length load her up with an extra 12 people, when she would perform like a displacement boat. But with no more than 25-45% overload dependent on length she can be built to, she will still perform for them. In some way that's analagous to many sailboats that generally 25% of displacement people work to.

    It's for that reason that I said she would work best moving a group, say 6 people around and a water taxi does that. I was actually thinking of private use rather than commerical: a family with a superyacht that can't anchor in and need to get around from outside the breakwater. Ribs can be wet and exposed in the winter: not so great when your dressed for dinner.

    UK motorboaters that want to get there moneys worth and use there boat year round seem to gravitate to a semi displacement powerboats after having a displacement boat and find it a bit slow once they've explored the local area and a planing boat that can lose efficiency when they have to slow down in rough weather. Companies like Arvor make these now with enclosed wheelhouses and are mainstream, replacing the displacement launches that used to be built.

    The other approach, still working to primary principle of length to displacement ratio then beam to length is to split the hull buoyancy and have a catamaran. The commercial market has gone this way for the extra deck space it gives. Cat hulls are broadly doing the same thing as Greta, which is why a multihull designer like Irens would naturally go this route for himself.

    Ed

  32. #32
    Join Date
    Dec 1999
    Location
    Oriental, NC USA
    Posts
    4,624

    Default Re: A neat fuel efficient launch

    Quote Originally Posted by keyhavenpotterer View Post
    As we've all pointed out, the efficiency comes from the lwl length to displacement ratio and beam to length ratio that allows progression into semi displacement speeds. People on Kirabati would lose the efficiency if they treat her as a ferry and with all that length load her up with an extra 12 people, when she would perform like a displacement boat. But with no more than 25-45% overload dependent on length she can be built to, she will still perform for them. In some way that's analagous to many sailboats that generally 25% of displacement people work to.

    It's for that reason that I said she would work best moving a group, say 6 people around and a water taxi does that. I was actually thinking of private use rather than commerical: a family with a superyacht that can't anchor in and need to get around from outside the breakwater. Ribs can be wet and exposed in the winter: not so great when your dressed for dinner.

    UK motorboaters that want to get there moneys worth and use there boat year round seem to gravitate to a semi displacement powerboats after having a displacement boat and find it a bit slow once they've explored the local area and a planing boat that can lose efficiency when they have to slow down in rough weather. Companies like Arvor make these now with enclosed wheelhouses and are mainstream, replacing the displacement launches that used to be built.

    The other approach, still working to primary principle of length to displacement ratio then beam to length is to split the hull buoyancy and have a catamaran. The commercial market has gone this way for the extra deck space it gives. Cat hulls are broadly doing the same thing as Greta, which is why a multihull designer like Irens would naturally go this route for himself.

    Ed
    Agree with almost all you say except the superyacht tender bit. People with a superyacht are not going to be interested in a fuel efficient tender. The main USCG regulation that I was concerned with would be tenderness. The CG looks at a tour boat or taxi stability limitation when all the passengers move to one side to look at something or other when in the waters the boat is licensed to operate. No monohull designed like this one is likely to meet both max efficiency and a high level of stability. The most fuel efficient launch I know of is Weston Farmer's old Coyote ll. I wonder how it compares to Irens boat in results? When it comes to boats like this, I suppose there is very little that is new under the sun.

    I am not knocking Gretel in any way, but just trying to keep it in perspective.
    Tom L

  33. #33
    Join Date
    Feb 2004
    Location
    St. Michaels Maryland
    Posts
    559

    Default Re: A neat fuel efficient launch

    Watercraft Magazine ran a full length story about Greta about 2 years ago.
    I was born at a very young age. As I grew up, I got older.

  34. #34

    Default Re: A neat fuel efficient launch

    I remember, when you took a walk through any marina on the mediterranean some 30 years ago, a 32ft Trawler was on the upper end of the scale there and people were quite astonished how a private person can own something like that. Today a 32ft craft nearly disappears in between and you will see a mass of plastic bowls with twin 800 hp diesels, most of them quite ugly and with a design that looks old after just two years. Nigel Irens Rangeboat Series also claimed to be efficient. But were they commercially successfull? I doubt. The contracting builder went out ouf business some 2 years ago, as far as I know.

    The laws of the markets sometimes follow weird principles. And in times when fuel prices go down again, efficiency is becoming even a less important argument. Sad but true.

  35. #35
    Join Date
    Jul 2000
    Location
    N.E. Connecticut.
    Posts
    5,904

    Default Re: A neat fuel efficient launch

    Pretty! Looks sort of like what's new was once old (though a much lighter construction).



    New Jersey 1930's

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •