center of gravity?

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
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heater17
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center of gravity?

Post by heater17 »

Im about to build my motor stand and i have been using the search feature to try to find right distance for the prop and transom and i keep finding the beer can method. But my question is about the center of gravity compared to prop location, if the weight of the motor is slightly lower or higher will that make the boat handle differently? In my mind the lower the weight the better so the boat wont be top heavy. but will an extra few inches of prop hanging down in the hull rob me of power or performance?



I have an open glass hull with a car motor and gear box.

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Junker
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Re: center of gravity?

Post by Junker »

As I understand it.........

The air is collected at the prop tips and channeled toward the center of the prop where your thrust is created.

6-8" inside the hull is about normal.
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kfowler
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Re: center of gravity?

Post by kfowler »

I just burn gas, i'm no boat builder by any means but I think I've heard beer can from bottom and beer can from transom.

I know my prop goes well below my transom and was built by a reputable builder.

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JAMES
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Re: center of gravity?

Post by JAMES »

heater17 wrote:Im about to build my motor stand and i have been using the search feature to try to find right distance for the prop and transom and i keep finding the beer can method. But my question is about the center of gravity compared to prop location, if the weight of the motor is slightly lower or higher will that make the boat handle differently? In my mind the lower the weight the better so the boat wont be top heavy. but will an extra few inches of prop hanging down in the hull rob me of power or performance?



I have an open glass hull with a car motor and gear box.
yes the lower the less top heavy and no it will not hurt performance taking it low .. mine is low as all hell just for the fact i like to experiment my prop is 81" and maybe 4" off the bottom ........... the soda can method is good for dd and ac motor jmo 7" or so is fine now if u have a 30" deep hull and your prop is on the bottom i assume u may loose a lil thrust but i doubt your transom is 30" :wink:
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heater17
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Re: center of gravity?

Post by heater17 »

As long as I don't loose performance I wanted to keep everything fairly low. prop is 80 in 3 blade R. I don't like having the motor and all that rigging way up high like that. my seats will be low as well.


James, how low from the top of the transom is yours?

fannman
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Re: center of gravity?

Post by fannman »

drop it down in there I have ran over ten inches of prop below the transom with no problems,if you look behind the prop on most airboats its dirty air there anyway the radiator is a big air killer plus I think they run better the lower you run em.
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JAMES
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Re: center of gravity?

Post by JAMES »

heater17 wrote:As long as I don't loose performance I wanted to keep everything fairly low. prop is 80 in 3 blade R. I don't like having the motor and all that rigging way up high like that. my seats will be low as well.


James, how low from the top of the transom is yours?
i have a slanted transom 8-9" from level off transom dwn got the idea from waterthunder and dan the airboat man to who no their shyt
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farmboy
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Re: center of gravity?

Post by farmboy »

I was told with a "R" you can up about 10inches inside the boat. My last boats prop was about 9inches in the boat and it ran great.
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HAMMERHEAD
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Re: center of gravity?

Post by HAMMERHEAD »

Junker wrote:As I understand it.........

The air is collected at the prop tips and channeled toward the center of the prop where your thrust is created.

6-8" inside the hull is about normal.
GOOD ADVICE! I BELIEVE THE PROP BEING DOWN INSIDE THE BOAT HELPS BAIL THE AIR OUT OF IT MAKING IT MORE ARROW DYNAMIC.

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AntiqueFarmEquipment
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Re: center of gravity?

Post by AntiqueFarmEquipment »

Hey H...get you boat running damn it!

I have triangular braces that go from my stringer to the transom but my prop is as low as it can be +or- a few inches off the brace if that makes sense. I'd say you could come look at while we're out hunting Monday and running around but than you'd have a working airboat :P
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heater17
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Re: center of gravity?

Post by heater17 »

Thanks for the info, I am going to run it about 8in down there and have the driver seat about even with the motor.

Hey L, I still got my old boat where and what you huntin?

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