Hybrid Workboat

Discussion in 'Boat Design' started by saeble, Dec 20, 2005.

  1. saeble
    Joined: Mar 2005
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    Location: Australia

    saeble Junior Member


    I'm hoping to build a workboat. Primarily as a floating light steel fabrication platform for making frames for synthetic reef structures. it will also support both independent tank and hookah divers. You'll find details about how the process I use, works, on this site :


    take special note of the bio-rock process.

    The brief : (loosely written)

    I need a very flexible, very long ranged, fast, (if possible), stable, positive bouyancy, very independent, tough and serious little vessel. It will be working in both inshore and blue water, open ocean conditions. Key words/phrases are, simplicity, multipile redundancies, high survival options.

    Steel, Catamaran hull.

    Length : 6 metres
    Beam : 3 Metres(I'm not that fussed about trailerable size)
    Draft : As shallow as is possible.

    Inboard power from two V6 Holden (chev), marinised petrol engines, delivering around 180 hp each (360hp total). They weigh in at about 600 kilos apiece. I like these engines, they are tough, locally plentiful and cheap as shirt. I can get these powerplants for under $7500 USD for the pair, basically ready to go.

    I like the idea of Kort nozzles for towing stuff. I havent much info or thoughts on control surfaces, rudders etc.

    I want to use steel because I will have steel welding and fabrication equipment onboard, hence if I hole her, I can beach her and fix her on the spot in Faroffganistan without being even slightly phased by the experience.

    I'm all in favour of sealed cells, or cells with positive sealing systems. Ones which I could blow out like a submarine does ballast cells if I manage to flood one of them. Having a dive compressor onboard means I can attach an airline to a cell and pump the sucker out. I'd like to have more than one way to get my hull 'dry' again. Im a big fan of humungus bilge pumps to keep pace with the flooding of a huge hole..:)

    I'm looking at getting pingpong balls by the cubic arseload to fill voids and cavities... so I can remove them for inspections without spend 40 years scraping out spray foams. I think a very light smear of silicone on each one will stop my boat sounding like a lottery draw on each wave strike..:)

    I have little sorted out for the above deck superstructures. I imagine I will spend a good deal of my time in the tropics.

    I like the idea of semi-hydrofoil systems to get my hull up out of the water and onto the plane 'early'.

    I want to fit a kitesail control system so I can use one both as energy saving and emergency mobility system. I do not want a traditional mast. I have a very bad allergy to blue blazers. :p


    With all that in mind, can anyone offer me some kernels of advice ?

    I will post some basic layout diagrams if it seems like I'll get some meaningful feeedback.

    My thanks in anticipation :)
  2. Robjl
    Joined: Nov 2005
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    Location: Adelaide

    Robjl Senior Member

    check the weight and ???

    saeble, I suggest you confirm the weight of your motors, I don't think they can weight 600kg each!
    My "kernel of advice" as you put it would be to start your design brief again.
    Start by working out the space you need for all the gear you intend to carry and the weight of it all; you need to be fairly accurate if you are serious...
    Steel is tough...but it is heavy.
    "I want to use steel because I will have steel welding and fabrication equipment onboard,"
    So what will you have;
    Welding = Arc, oxy-acetylene..
    Fabrication= vice and a hammer or will you have some sort of bending gear, bench shears, plate rolling gear, press???
    And of course all this gear implies the need to carry a stock of assorted metals.. more weight.
    I think your ping pong ball solution to bouyancy is.....different.:confused:you may have watched too many episodes of Myth Busters.
    In my view unless you can arrange enough positive bouyancy to support the entire vessel with load and crew there is no point. Stick to watertight compartments. They work.
    Also don't forget fuel.. 360Hp takes a lot of feeding.
    Work out your desired range...then you can estimate tankage required.
    I assume you will also want to liveaboard...that also implies a lot of extra gear.
    The weight of all this is adding up..
    From what I am reading in your proposal the boat simply isn't big enough and your choice of power in innapropriate...use diesels they are much better and you don't have the highly flammable fuel problem.
    Also you need to be aware the if this is a "workboat" you may be wise to build to "commercial standards" (the USL code)...talk to your state Dept of Transport/Marine & Harbors or whatever they call themselves...they can advise with a phone enquiry.
    You may not like some of the advice you get....some of the surveyors wear "Blue Blazers".
    Hope this isn't too meaningful for you.
    Keep us posted.
  3. saeble
    Joined: Mar 2005
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    Location: Australia

    saeble Junior Member

    now dont you go getting all 'Engineer' on me mate..:)

    Im having some fun here, all those cold hard factors you're throwing in... :p


    Diesels ? No thanks. Heavy, stinky, expensive and very non sexy. I've seen the sorts of tolerances at which they run. I know what happens to diesel with only a few moments of oil starvation, dilution or pollution. They die and die VERY hard.

    Put it this way, there is an all but never ending supply of V6 Holden powerplants out there. You try finding a marine powerplant offering around 180hp for $750 USD... TOTAL. If I blow one up, a trip to the car wreckers and I'm back in business. You simply cannot compete with that sort of pricepoint. No even the veritable chevy small block V8 comes close. I'll live with my volatile fuel for that kind of price.

    I'll see what I can do about getting one on some scales. My guesstimate is probably out, but theres no harm in an over-estimation of weight in this case.

    My welding fabrication consists mostly of rebar and mesh frames. Think very well built concrete reinforcement, minus the concrete and you get the idea. My chief tools of trade are MIG and ARC welders, grinders and the like. You can get some beautiful little light Inverter ARC welders which are about the size and weight of a four slice toaster. I love mine. It is perfect for the kind of work I do. Steel is awfully forgiving stuff. Aluminium does not like to be bent too many times before it fails. Steel you can use and abuse for alot longer.

    As far as carrying steel stock goes, no. My intention is to pick up whats needed in a local port and head out to the site, dump onshore, and use it as needed. Most of the time I wont need to use her as a packhorse when I'm working. By the very nature of my work, its a coastal sort of pursuit. I only mentioned the blue water capability because I do want to cover some pretty wide expanses of water, not Atlantic crossings by any means, but quite sizeable journeys none the less.

    As far as the 'live on' part goes... I'm not one for creature comforts. You'd be suprised just how little one needs to be happy. My 'living on board' would be more akin to 'camping' on board.

    I guess the recurrent theme here is that if I build this boat the way I want it to... it will not be a prissy little device. I tend to build things to take an absolute pounding. Put it this way the fenders on the dockside are to protect the dock from my boat, not my boat from the dock. I will build far in excess of most standards. The ones that make sense that is.

    Dont chortle too loudly about the ping-pong balls. I've seen it done. It's merely insurance if the hull is ruptured. I cant think of anything worse than a partially seawater saturated foam core... with the ping pong balls... no problems, flick em out, fix your problem, seal it up again and off you go. They are insurance only, they go inside sealed cells, preventing total flooding of a compartment.

    Having said all of the above, you may have a point about size. Playing with placement of various important bits I want to put in, I'm running out of hull for them, and cutting into my own self enforced limits of saftey. I think I'll have to give up on even getting this vessel under the normal 'wide load' diemensions for road travel. (My build site is well away from the coast.) I guess I'll need a flat bed and got to a 10mX5m basic form factor. Then of course I'm going to run out of power... :)

    Four V6's ?? :p ( now Im just stirring the pot )

    Oh.. and I might need to get close to the Straits of Malacca, so if you can suggest which turret/gun combination is good for pirates, please let me know :p
  4. Chris Ostlind

    Chris Ostlind Previous Member

    Time wasting


    I get more than a feeling that this is like one of those exercises that teenagers engage in to amuse themselves with how ruggedly cool they can be about what they consider to be technology.

    Let me get this right... you are advocating a highy explosive fuel source within the very same enclosed environment (the whole boat is an enclosed environment, mate) as you are welding equipment? Let me know your first port of call and I'll write the obituary for you ahead of time.

    I think you're wasting our time by tossing this nutso idea on the table. If you think differently, I challenge you to build this amazing boat you have so foolishly outlined and get it out on the water where the only damage you will likely do is to yourself.

    Come on, mate... it's time to sack-up with your cheapo gas engine theory.

  5. saeble
    Joined: Mar 2005
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    Location: Australia

    saeble Junior Member


    What an awful attitude.

    Next you'll tell me that there is no such thing as a welding rig on the back of a truck...

    What kind of tool do you think I am ? I DO NOT intend to weld or work right next to my fuel tank, nor will any fuel tank breather be anywhere near my welding area. In fact my filler neck is likely to vent into a compartment I can seal whilst welding. Oh... damn... I will also have little gas engines powering my welder... crap... oh well, obviously that will blow up too.

    You obviously haven't enjoyed your inner pyromaniac too often and know how petrol and its vapours burn. Granted its more volatile than diesel, but its a long way from the 'sweaty dynamite/nitro glycerine' kind of BS you seem to be suggesting.

    Dude... I weld in the open most of the time, under a galvanised iron roof. No walls at all. I do not suffer the privations of a cold/wet climate. On my boat I will do much the same.

    I hope to see you on the water at some point.... as I go flying past you I'll make sure to remind you how much it didnt cost me...

    My only suggestion to you my friend is to try jumping to only one conclusion every day, that way you will only make one mistake every day, (hopefully).


    Let go of the Diesel side of the Force...:p
  6. Chris Ostlind

    Chris Ostlind Previous Member


    It's not my conclusion.... Dude... it's the overwhelming conclusion of the entire commmercial boating world. Gas engines are a sure sign of trouble aboard a working boat.

    Now, you don't have to believe me, or anyone else who may write to this discussion, but take just a moment or two from your turgid, frenzied, gas sniffing induced state and do some research before you install one of these high HP engines of which you speak.

    Virtually any marinized diesel engine is going to have way more torque than will your gas engine. It will run at lower rpm's and save huge amounts of fuel cost. Lower fuel needs mean less tankage. Less tankage means less displacement requirement, means more efficient forms. The diesel will have enormously lower amounts of friction wear due to the lower operating speeds and it will run for years beyond anything a gas engine has ever done aboard a boat.

    Gas generator for your welder??? Bubba are you loose upstairs or what? When you have a high torque engine on board for propulsion, is there any real need to install yet another for the on-going electrical needs. Put the transmission in neutral, engage the genset and stop huffing those nearby exhaust fumes. You must think that a 6 meter cat has unlimited room and displacement potential for all these appliances you intend to install.

    Go back and read the drivel you wrote in your first message and take a hard look at the design criteria as Robjl suggested. If you have anything more than a death wish, you'll be quick to revise your apparent limited ability to grasp the complexities of your vapor induced state of mind.

    I think you're a troll and you'l get no more from me.

    Ping-Pong balls... That's rich.

  7. Deering
    Joined: Feb 2005
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    Location: Juneau, Alaska

    Deering Senior Member

    Ignore the naysayers Saeble. Your idea is brilliant! Don't change a thing. But make sure the steel hull is thick enough to weld on - I'd say 1/4 inch should be adequate.
  8. saeble
    Joined: Mar 2005
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    Location: Australia

    saeble Junior Member

    Deering - dont worry mate I'm used to it. These sorts of guys like to grind others under the heels of tradition and like nothing better than to stifle a new idea, for fear it may change thier lives in some small way.

    CHris - you my friend, started this and for once, I will partake of the rich tradition of Australia, in that I will not start a war... but I will damned well finish it...

    Diesels are F#%$ing expensive. Methinks that once we strip you of your armour of well thought reason we'll find resentment. "How dare this little punk find a way thats vastly cheaper than what I've had to pay in the past."

    Ettore Bugatti said at one point “every admiration for Monsieur Bentley, because - after all - he does build the fastest trucks in the world....”

    In other words W.O. Bentley didn't bother with the prescribed rules about what a fast car should be, and went on to great success. Big 4 cylinder motors and buggy cart springs, were the height of crudeness and 'poor form', but they cheerfully won many times.

    So... for better or worse, you my friend, can jam your silly diesels up your bottom, provided of course you can get it past your hyper retentive sphincter.

    As far as my crude petrol cheapos... I know they are not perfect for a marine application. Atleast the V6's configuration offers a fair chunk of torque and by running as twins, I dont really have too many problems. Alot can be compensated for with props which are actually suited to the engines concerned. I can also re-map the ECU's fairly easily. In a nutshell, lots of tweaks can be had.

    I need a portable welder for onshore applications occasionally. I need the flexibility. I go to some locations where the local power supply is either entirely absent or very poor.

    more later....
  9. Cheesecutter
    Joined: Dec 2006
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    Location: burnett Heads. Qld. Aust

    Cheesecutter Junior Member

    Goodness what are you smoking
  10. grumpygrady
    Joined: Oct 2006
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    Location: florida

    grumpygrady landlubber

    to bad that when someone has an idea it gets bombed
    funny thing is i see gas powered work boats here all the time
    yes some are even inboards
    oh and by the way deisel fuel in liquid form is more flammable than gasoline
    but not by vapour
  11. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Well, Saeble, you have some interesting ideas. Some are good, some are OK, some need more thought, and some are dangerous.

    Firstly, the concept. The reef restoration thing is an interesting and worthy project, and you're right that you'll need something good and solid to work from to do it. For a welder's boat, a hefty steel-hulled cat is probably a good choice.

    As to the dimensions. In the waters you appear to be planning to run in, 6 m by 3 m simply won't be big enough for what you want to do. To do a good job with welding, you need a stable, dry platform with plenty of space. The boat you've described is only a metre wider, and the same length, as a typical cottage runabout in Northern Ontario; it'll take spray over the rails, it'll rock around a lot, etc, etc. It's also too short to have any kind of speed in displacement mode, so you'll have to be on plane all the time- in big choppy seas, that gets really difficult really quickly. Go to at least 8 metres; I'd also suggest you consider using thin displacement-mode hulls instead of trying to get it to plane; the same speeds could be achieved with less pounding and less energy wasted, and it would also be more stable. As described, your boat would be way too heavy to plane well anyway.

    Since this is a workboat, operating in the open sea with welding gear and other dangerous stuff on board, you had better be building to the appropriate commercial standards. On everything. No exceptions.

    Now as for power. I know you love your cheap Chevy sixes. (The 3.8s I presume?) But in marine use, they are not going to last long- and by that I mean more than a couple hundred hours- if you run them at WOT pushing that short, fat, heavy planing hull you describe. They'd have to be detuned a lot, to get any sort of reliability in that boat. And as for the fuel- sorry mate, but gasoline and welders simply do not mix. I have never, ever seen a welding boat with gasoline on board, it just isn't done- because it is a hell of a lot more dangerous than you seem to think. Gasoline's behaviour in the bilge of a boat is completely different from its behaviour in a car, building or any other environment. So you're welding on deck, not the bilge? Sure.... but your welder itself has to be in the dry, or else it'll short out, and just about every dry place in such a boat has the ability to collect over-LEL concentrations of fuel vapours. In short, go diesel; you'll steam and fume now when you pay for them, but you will thank yourself later. (And there are good, cheap, used diesels around as well, they just don't come from the same junkyards as your Holdens.)
  12. Gilbert
    Joined: Aug 2004
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    Location: Cathlamet, WA

    Gilbert Senior Member

    My father was a commercial fisherman from the time he was quite young up to the age of 77. He never owned a diesel engine. He never had a fire or an explosion on any of his boats. There are thousands of other commercial vessel operators who have had the same miraculous experience.:) There are probably many times that many pleasure craft operators who have had the same result. It is just not correct to suggest that if you have a gasoline engine on whatever kind of vessel you will die in an inferno.
  13. gary1
    Joined: May 2006
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    Location: australia

    gary1 Senior Member

    Hey Saeble,
    MATE quite a few years ago I worked for a while for this fella
    Engwirda Marine Salvage & Construction
    5 Kara Crs Whitsunday QLD 4802
    ph: 0417 481 964 The actuall guy I worked for was Joe Engwirda he would be fairly old by now if he is still alive at all He had a barge type set up which I'm pretty sure he built himself it was a hell of a rig, stable, crew accomdation, big working area made out of steel sounds like the sort of thing you are looking at building. If I remember correctly though his was pushed along by diesel engines though. Still he would be worth while contacting and having a yarn with as you really can't beat getting advice from someone who has been there and done that.
    Stay Safe
  14. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    I don't recall anyone saying that all gasoline powered vessels are dangerously volatile bombs. My own boat is gas powered and I am quite comfortable with that.
    What Chris and I have tried to point out is that where there is welding gear, there are sparks. In an environment where sparks are common, gasoline is not a good choice, because it is so volatile that there are always fuel vapours around. Fuel vapours have a tendency to ignite. It is much, much harder to get enough diesel vapour in the air for it to ignite at ambient pressure, than it is to do the same with gasoline. Gas engines are not inherently unsafe, provided they're installed properly, but they're not a good choice for this application where they and their fuel must share limited, confined space with welding gear.

  15. Gilbert
    Joined: Aug 2004
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    Gilbert Senior Member

    Go back and read Chris Ostlind's first post and then tell me again what he was trying to point out.
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