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Thread: Perhaps, a new engine is required for our needs. New engine designed specifically...

  1. #1

    Perhaps, a new engine is required for our needs. New engine designed specifically...

    If some tool and die firm connected with a foundery in the USA could make an aluminum/magnesium alloy engine casing designed to house a crank (E4340 forged steel of course) with a 4.00 inch stroke, having 1 inch wide bearings, a mechanical oil pump, a high lift/long duration cam with pressed timing gear, and using a magneto ignition (EI and EFI optional), we would have the beginnings of the type of engine the LSA/air boat folks need, and a new, completely different power plant designed to support this sport industry, made in America. I think a two cylinder air cooled version could meet the 100 lbs requirement; a four cylinder version could range between a 140 lbs. to 160 lbs. weight requirment. Both would have 4.00 inch cylinders, for a rating of 55 h.p. (3 gph) and 110 h.p. (6 gph) @ 3200 rpm power output respectively. No reduction drives required.
    Last edited by djmsgstride; 12-30-2010 at 12:57 AM.

  2. #2
    There is a good motor out there near what you are describing..... it will be next summer before I have my hands on it.... stay tuned

  3. #3
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Quote Originally Posted by djmsgstride View Post
    If some tool and die firm connected with a foundery in the USA could make an aluminum/magnesium alloy engine casing designed to house a crank (E4340 forged steel of course) with a 4.00 inch stroke, having 1 inch wide bearings, a mechanical oil pump, a high lift/long duration cam with pressed timing gear, and using a magneto ignition (EI and EFI optional), we would have the beginnings of the type of engine the LSA/air boat folks need, and a new, completely different power plant designed to support this sport industry, made in America. I think a two cylinder air cooled version could meet the 100 lbs requirement; a four cylinder version could range between a 140 lbs. to 160 lbs. weight requirment. Both would have 4.00 inch cylinders, for a rating of 55 h.p. (3 gph) and 110 h.p. (6 gph) @ 3200 rpm power output respectively. No reduction drives required.
    djmsgstride,

    I don't know you, so I sure don't want to be disrespectful. You MAY know what you are talking about, but then again, you MAY not. You may be just blowing hot air, or you may be able to contribute. I just don't know.

    The first post that I saw of yours had a significant error... It was off by a magnitude of 10. Honestly, that could have been a simple typo error. Or, it could have been total BS.

    Since I do not KNOW, I will try to stay open minded.

    Now, let's be realistic.

    The 4A084 is an obsolete military generator engine. Yeah, it works O.K. as a Mini Airboat engine, but they do NOT make them any more, and have not for a very long time.

    So, don't be expecting any company to spend high dollars developing new cams, or cylinders, or whatever for them. It just ain't gonna' happen.

    On the other hand, Briggs or Kohler may have plans that we don't know about. But in this economy, I doubt it.

    Respectfully,

    Duane






    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  4. #4
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    Sorry for the dumb question, but what does gph stand for? Gallons Per Hour?

  5. #5
    yes gph = gal/hr

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    Wow.... 6 GPH! If I was wishing, it would be for less than that.

  7. #7
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Quote Originally Posted by Stuck Fish View Post
    Wow.... 6 GPH! If I was wishing, it would be for less than that.
    Stuck Fish,

    Calm down !

    GPH figures are "usually" for an engine that is running at near 100 %.

    Once you get it up and moving, you probably won't be pushing it that hard.

    "Wax on - wax off"

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  8. #8
    stay tuned.... 130-150HP only burning 3-4gph..... it wont be till mid next year but working on getting it on the boat...

  9. #9
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    Quote Originally Posted by brlcla View Post
    stay tuned.... 130-150HP only burning 3-4gph..... it wont be till mid next year but working on getting it on the boat...
    Is this a top secret project? How much does it weigh? Not sure I can wait 2012 for this. lol

  10. #10
    not top secret but I don't want to give anything away b/c I want to be the first with it on a boat.... just say its a 4 stroke, 46 cu in, 2 cyl motor making 140HP and weights less than 200# dry.... it may be 2012 before it is complete b/c I need the funds to get the motor first....

  11. #11
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    Sound's like a BMW motorcycle engine
    Steve

  12. #12
    Administrator Papee's Avatar
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    I went all through that modifying a smaller engine to make more power before I switched to the 084. The more you modify an engine the less reliable it becomes. I have some things in the works also after running my setup for a while. In my opinion the 084 is the best otion we have right now for a mini. It's already close to the hp needed to be an efficient combination.

    We can only go so far or expect so much from these boats. You can't expect them to perform like the big boats. My goal is to be able to haul two people and gear reliably for a good day of riding or fishing. My boat works fine with two people but I do have to push it little harder than I would like.

    My idea/plan is to build a boat with a matched setup between hull and motor. We all know that drag on a hull will slow a boat down, determining the amount of surface area these engines can push efficiently is key in my opinion. I've watched people build boats with a lot of combinations and watch their results taking in information. Designing a boat that is made to compliment it's powerplant is very important.

    Specifically with the 084 we have a good idea how the engine works and what rpm range is best for this engine. I run a direct drive setup and it's very close to being enough for this application. My plan is to go just a bit wider with my hull, my bottom being at 5ft 6inches. My bottom now is 5 foot. I will also be changing to a redrive but just enough to run a slightly larger prop both in width and length. I feel that using engines that are available and modifying them slightly for or use is the better choice.

    I've always suggested how important the hull is in this application. Using a hull designed for a full size application is like putting the cart before the horse. Putting together a package that is solely designed to work together is the key in my opinion. Of course not everyone wants an 084 but my idea will apply to anyone considering a mini build. I think that these hulls being used just have to much drag for these motors being used. Bigger is not always better.

    I've already had over two years of relatively problem free use of my boat and I think I have a combination that is very close. I've also been known to march to the beat of a different drummer. I really enjoy the different ideas about this newer version of the airboat. As always our boats will be as different as our opinions of how they should be made. If we're having fun that's what it's all about.

    Edit: Don't get me wrong, small engines still have a place in mini airboats. They are what minis are built around. We just can't expect the smaller motors to haul all the weight or get the performance some of us want to achieve.
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  13. #13
    it is stock 140HP... no modifications...

    i also am through dealing with modified small engines... don't get me wrong the Generac I have now seems like a strong little motor considering its turning a WW 3-blade prop... spinning 4000rpm on a 2:1 reduction with over 8deg of pitch...

  14. #14
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    I would think the calculations for actual thrust from various combinations of blade area and pitch, rpm, LFM/CFM, etc, to compare to actual drag figures for the potential hull configurations....would help.

    Maybe, as a starting point, we could simply drag a potential boat behind at various speeds with a scale on the tow rope to measure the drag, and maybe produce a graph showing the projected drag increase as speed is increased?

    I think HVAC type calculators can be converted to project different fan/engine options and their projected thrust.

    It seems to me that the point of a mini is to burn less fuel, and save money.

    If we soup up engines, etc...we spend money on modifications that might defeat the overall objective....if the money for the mods has too long a payback period, etc.

    My initial thought is that frontal area and draft are the prime boggies on the hull drag, and that a shallow draft would require a broader beam to spread the weight out, which would increase frontal drag, etc....

    ...so, perhaps, a longer boat, but with narrower beam, to displace the same weight of water, but with less frontal drag, might work better with a smaller lighter engined mini?

    Where are we, as a group, in terms of this type of thing? (I'm new here, and, assuming you will teach me things)


  15. #15
    KWAZY old Southerner... Duane Scarborough's Avatar
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    TEEJ,

    Welcome to the forum.

    You made some very good points. It gives us all something to think about.


    Traditionally, airboat hulls are "about" half as wide as they are long. I think that this because of the typical operating conditions. A wide, short hull will be much more maneuverable than a long narrow hull.

    A long, narrow hull would be perfect, IF you never wanted to turn. It'd be fast, because of the low frontal area, but the first time you tried to do a quick turn, you'd be in trouble. It all depends on what you want.

    Any souping up of an engine has got to reduce its reliability. If you want a race boat, that's fine. But if you want to build a boat that you can depend on, it's different.

    An example would be my Chevy Colorado. I could replace its factory 3.7 I5 engine with a souped up 383 with nitrous. It'd be fast as heck on the drag strip, but I could never depend on it for a long trip. Or for that matter, I couldn't depend on it to take me back and forth to work every day. In every thing mechanical, there is a trade off.

    I prefer utility and dependability. Others want speed. It all depends on what you want.

    Thanks,

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  16. #16
    Administrator Papee's Avatar
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    Now that's a first post! Keep in mind that when we are talking about drag the area is only about 1/3 of the hull. When a boat is on plane it is only running on the back part of the hull. It is this area that determines the drag. A wider boat operates on about the same percentage of the hull but has more surface area. If you are too narrow the boat rides lower in the water and will also slow down the boat.

    The shape of the hull in that area also adds to the complexity of the figures. For example my hull bottom is 5ft wide and slightly rounded in this area, I am running a direct drive setup. Others are using the same motor with a reduction drive to enable them to run a bigger prop creating more thrust but I see the same speeds or faster than some of these boats. This is all relative to the conditions of course, current, water depth,wind, etc.

    It just the nature of us tinkerers to modify our rides. I set out to build a bare bones boat keeping everything as stock as possible to keep costs down while keeping the reliability of the engine intact. Others choose a different level of mods making simple modifications while others go full on redesigning the motor. This experimentation is good for our hobby.
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    http://stratus2000.homestead.com/fil...81descript.htm

    http://stratus2000.homestead.com/fil.../ea81specs.htm

    They are made for light planes, and Hovercraft guys use these sometimes, looks like it might be closer to what the OP was hoping for?
    Last edited by TEEJ; 01-05-2011 at 08:51 PM. Reason: slow typer....

  18. #18
    subaru engines are nice.... but can get pricey

    http://www.ramengines.com/index.html
    Last edited by brlcla; 01-06-2011 at 08:20 PM.

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