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| Outboard drive used to drive an amphi... |
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Paul Minnicks
| | Posted on Wednesday, August 14, 2002 - 07:20 pm: | 
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> The plans for my home built (NOT FAA CERTIFIED) Coot-A amphibian I am
> building call for the engine to be installed on top of a pylon. I want
> to move the center of gravity down and therefore make it more stable in
> flight and on the water. I am now in the process of investigating ways
> of accomplishing this. One idea I have is to install the engine in the
> haul and drive the propeller with an up side down boat out board drive.
> I know just about everything there is to know about aircraft and very
> little about water crafts. That is why I am contacting you. The engine I
> am going to use is a water cooled, 230 hp, fuel injected, Subaru car
> engine. It will have to incorporate a gear reduction drive get the
> aircraft propeller tip speed under supersonic. Boats with high rpm V/8
> car engines, must also have reduction drives incorporated in their out
> drives . But, gear lubrication when upside down and the shear weight of
> an outboard installed in an aircraft could be problems. To lighten it
> up, I would be able to cut away some of the drive case housing and still
> have enough strength to push a light aircraft. May be what I need are
> blueprints of existing out boards and drives. or a very knowledgeable
> mechanic. I just don't know at this point.
>
> Anyway, if you would help me or turn me in the right direction to get
> information on this subject I would really appreciate it.
>
> Paul Minnicks, A&P, IA, Commercial Pilot (and novice seaman) |
miro
| | Posted on Wednesday, August 14, 2002 - 10:52 pm: |
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Seems to me that you'll still have a C of G challenge plus a whole lot of rotating parts which will almost certainly be difficlt to get balanced. The outdrives for marine applications are purpose designed and built and while I suspect that with enough time and resources you'd be able to get the thing to work, I'm not sure that it would work all that well. I'm also not sure that the drive shaft and bearings could handle and aircraft prop. Props driven by long shafts inevitably lead to major design issue with the bearings.
Just this past weekend I watched as an amphibian aircraft struggled to take off - seems to be a very large wetted area on the hull causing much friction and drag. He eventuially DID take off after seven ( yes seven) attempts. But it convinced me that conventional float aircraft are the way to go.
My 2 cents worth
miro |
Joe
| | Posted on Thursday, August 15, 2002 - 01:37 am: |
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Your engine will produce 230 hp. That is the same output as a Cessna 180 which have a Continental O-470....and run two bladed props that are 86 to 88 inch diameter. These are variable pitch of course. You would be better off to belt drive the prop shaft and then you can run any diameter prop you want. |
captainbill
| | Posted on Sunday, August 25, 2002 - 04:44 am: |
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Paul, look up the Guys at "Great Plains Aircraft Supply". They are experienced in both aircraft & prop-driven air boats. Now selling a belt drive 2.06:1 reduction drive for a Kohler 25hp as well as VW/aircraft conversion kits.Bill |
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