You heard it here first: Low Profile "Hidden" outboards coming soon.

Discussion in 'Boat Design' started by Squidly-Diddly, Jun 25, 2013.

  1. Squidly-Diddly
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    Squidly-Diddly Senior Member

    I get a feeling that fairly soon (5years?) someone will come out with a 'game changer' of an outboard whose main feature will be that everything except a snorkel and fuel and control lines will be in a single 'blob' more or less "snug" up against the transom, with a pivoting "kick-up" sort of like a stern drive.

    Maybe a "boxer" style engine.

    Main advantages will be:

    1) much improved center of gravity, as center mass of outboard will be under(or at least much lower) water line at rest

    2) free up space at transom, and maybe have a 'step' on the motor housing for easy boarding (with motor off, other safety features like auto prop-stop similar to chainsaw auto-stop, of course).

    The design "challenges" will of course be keeping it all nice and sealed, and making it reliable enough that you don't need to 'tinker' with it out of the water, and/or design whatever access is needed so it can be serviced "in place" and even if it does get water it wont be fatal.

    The "biggee" will be making it as reliable as typical new normal outboard, because it will be at least "odd" to work on. For example: Not sure how you might test run it as you see guys doing with big steel drum water tanks.


    I just think that with ever improving CAD/CAM that doing stuff like this will become cheap and practical, and these days things like outboards (and motorcycles) are all but maintenance free.
     
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  2. gonzo
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    gonzo Senior Member

    CAD/CAM is not going to improve technology. It is not better than a pencil at thinking. What you are describing is basically an I/O.
     
  3. messabout
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    messabout Senior Member

    Boxer outboards were common in the 1930s through the 50s. Both two and four cylinder layouts. Evinrude had a four cylinder 5.4 Hp engine called the Zephyr. and at the other end of the scale was "big four" with a claimed 50 HP. In the middle was "Light four" which it was not. The middle power engine at a claimed 22 HP was a twin boxer called "Speeditwin", which it was not. Johnson made a mid sized boxer twin to compete with the Speeditwin. It was inelegantly called a PO. Johson also made a racing type boxer twin similar to the PO but it had an external rotary valve and was the engine of choice for the C hydro class. If I recall correctly its designation was PR65

    An engine firmly attached to the transom implies that the lower unit housing must rotate independently of the engine. That was done about 1917 on ancient Evinrude one lungers. The torque reaction transferred into the tiller was most strenuous and uncomfortable but it did work after a fashion.

    It is conceivable that we may eventually have compact propulsion units that will be attached low and inconspicuously on the transom. They will probably be electric.
     
  4. keysdisease
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    keysdisease Senior Member

  5. Manie B
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    Manie B Senior Member

    I work and use both daily.
    I draw my own parts for machines in CAD and my suppliers gets my DXF files to cut and machine.

    What you are describing is unlikely, modern outboards are very cheap to manufacture, light mass - and light on fuel and minimal maintenance.
    Its like new cars, just more gizmoss like TV in headrests
     
  6. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Respones......

    Yes, Gonzo, pretty much an I/O but completely Outboard, so can be slapped on(or off) any outboard-ready transome. I agree CAD isn't smarter than pencil, sort of. Its main problem is can CAD first adds so much more thinking to use. But it is really good at scaling and stress/thermo simulation, which means designs CAN be reliable the first time they are built and fired up. That would be important on a project like this were customers would demand same or better reliability from a new, harder to service product. I saw a CAD demonstration 'simple' folding chair/desk design and they used CAD to scale it from 6'6" person size down several steps down to 3' person size, and each time they did 'allowable stress' and all that volume/mass/cubed VS surface/cross/squared stuff came into play. Would have taken a human months and they would've made mistakes. You were supposed to ask what size range of outboards I was thinking about, and I'd say "with CAD/CAM it would be much easier to scale and manufacture a range of different sizes"....but I was thinking of 10hp and over.


    Messabout....now I'm trying to figure out why the torque would be a problem with the 1917 design but not on regular outboard, but I think it would be easy to isolate any torque feedback with friction/stickion(tiller doesn't need to be as light and 'loose' as bicycle steering) at the tiller or consul controls. Electrics tend to have the motor down low as part of the prop anyways, for the sizes they have come in. I think lowering ICE outboards gravity and 'profile' is the challenge.

    Keysdisease....No, a completely different "animal" but you can see how SeaRay and Pursuit are sort of addressing the same issues and trying to design their boats to mimic what I'm talking about. I gotta wonder why those high end 'luxury' boats don't have I/O as that seems the more elegant 'out of sight, out of mind' solution. I guess with outboard you have certain advantages of being able to complete swap motors easily, or drop off just the motor at the shop. My idea would keep most of those advantages(when someone works out new procedure to mounting/dismounting the new funny shaped "low-board" motors....I guess they should come with lifting loop attachment point at nice balance point). I guess if the bottom profile of the "lump" was a "vee" then it would work on flat bottom(bottom of motor center flush with boat bottom), center mounted on vee hull, or twins on a vee (one side of vee flush with boat hull).


    Yes, I'm aware an "all outboard" I/0 would move the center of gravity even further back(a bit), which is already a problem on light boats with short tillers with single operator.
     
  7. BPL
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    BPL Senior Member

  8. messabout
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    messabout Senior Member

    SD; The drive shaft torque was transmitted as a reaction through the tiller. Something had to counteract the rotating force of the vertical shaft. It was you, the skipper. The skipper had to counter that torque with muscle. Not a lot of muscle because those old engines did not make much power. Still it was tiring and you could not let go of the tiller.

    The modern outboard has the lower unit housing firmly attached to the power head. So the only reaction that has to be countered is prop walk which is only a small fraction of the reaction of the ill conceived independent component design.

    I know about the old motor because I restored one of them at one time in the past. It did run and it did make the boat move. Starting it was an adventure because the starting drill meant that you'd grab the knob on the exposed flywheel and give it a determined twist. That starting gadgetry had the descriptive name; Knucklebuster. Those old engines would sometimes start in reverse rotation. It was a three port, or piston port design, so the thing would run in either direction. The crankcase was brass, the cylinder and piston were cast iron, the lower unit, propeller, and drive shaft housing was all bronze. The beast weighed probably 75 pounds for an output on a good day of one and a half HP. Great fun it was.
     
  9. gonzo
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    gonzo Senior Member

    I think CAD does the opposite. Because each part doesn't have to be drawn manually, a draftsman with little knowledge can produce pretty pictures that won't work.
     
  10. Jeremy Harris
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    Jeremy Harris Senior Member

    One idea I've had mulling around for a fair while now is to build a hybrid outboard. Outboards are pretty inefficient anyway, and the extra losses from using a hybrid approach might be outweighed by the advantages.

    What I was thinking of was to have a quiet and compact genset that could be fitted or stowed in a vented locker somewhere and an electric pod type submersed motor, like a big version of a trolling motor.

    The advantages would be similar to this suggestion, low C of G, more compact outboard installation, probably quieter overall, plus there would be power from the genset that could be used for house loads.

    The disadvantages would be two units with a combined weight that was probably a bit more than an outboard, the need for space somewhere for the genset and the reduced efficiency.

    For some lower powered applications it might well be a viable solution though, and would probably be a bit cleaner and quieter than an outboard, as gensets run at a constant rpm and tend to be optimised for fuel efficiency at that rpm.

    Probably a niche market thing, though.
     
  11. Squidly-Diddly
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    Squidly-Diddly Senior Member

    BPL, yes a VERY 'miniaturized' version of the Armstrong.

    Something 'miniaturized' by Honda.

    Armstrong didn't even seem to try and compact the design, almost like they felt "bigger is better" and adds seaworthiness.

    Plus, they were using an existing engine that normally sits in an engine room.

    I'm talking about same VOLUME and close to same weight as existing outboards, just adding some water-proofing and changing the shape.

    I see a problem with a very low design kicking up as a single unit, because on a normal outboard with a longer shaft the shaft has leverage on rotating the heavy power-head, but with a very low compact design it would not only not have leverage, but would need to lift, not just rotate, the power-head mass.....which is why I'm thinking a I/O type kick up is needed.
     
  12. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Jeremy, I've always thought that could work and the gen-set could be stored in the bow, since generally the bow is the least desirable living space in the boat, but the gen-set shouldn't mind the pitching action.

    Like all electric cars, it frees up design.

    Not sure what to do with exhaust. Bow mounted underwater discharge? Pipe running to stern? Either way it means specially designed boat.

    I do remember a buddy with a Scanoe w/battery and SMALL portable generator. He motor out and run down the battery THEN set the generator running when he got out and left the boat on some distant shore for a few hours to recharge. Seem to work OK and provided peace of mind.
     
  13. tom28571
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    tom28571 Senior Member

    Outboards are inefficient? How so? When an outboard is properly matched to a boat, it is at least as efficient as an inboard. Today, I see multiple outboards used where an inboard would be much more efficient but that is a fault of the application, not the motor. Besides, there are several ways to look at efficiency and fuel use is only one of them.

    "Hidden" outboards have been in use for a long time. What is different in the OP's proposal?
     
  14. Skyak
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    Skyak Senior Member

    Gonzo,
    I think you are way off in your understanding of what CAD/CAM does and enables. Draftsmen don't make pretty pictures of things that don't work. The profession that is pissing you off is 'industrial design' and they don't even work on CAD they use 'shapeware' like Rhino and they take pride in producing 'new' things.

    If you are using CAD/CAM right, there are no draftsmen -production and quality are driven directly by the part files. The parts are all designed in the assemblies and much of their function is tested virtually before the first part is made.

    I can't say that everyone who ever produced a CAD file knows what they are doing, but I can say with certainty that no mater how much you know about the function of an outboard engine, you would have absolutely no chance of producing a competitive product without CAD/CAM.
     

  15. Jeremy Harris
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    Jeremy Harris Senior Member

    Outboards almost always use a prop that is too small in diameter and poorly matched to the actual hulls resistance/speed curve. Sure, you can improve on the stock "one size fits all" by spending time matching the prop to the hull resistance curve, but in practice few owners bother doing this, they just accept poor efficiency.

    The second problem is that the majority of outboards use a small gearbox (for practical reasons) with a numerical lower gearbox ratio, leading to the use of faster turning, smaller diameter props, which are always going to be less efficient than a bigger, slower turning, prop. A look at any high power outboard demonstrates this well, they all use very wide blade chord props with a high solidity and a very poor overall efficiency (at best they might get to 50 to 60%).
     
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