Air boat for flood emergency

Discussion in 'Propulsion' started by rivergybsy, Jan 28, 2023.

  1. rivergybsy
    Joined: Mar 2015
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    Location: Australia

    rivergybsy Junior Member

    I am in the early stages to build an air boat with wheels. The intentional use is flood emergency. The punt hull should also have steerable wheels. The idea is that the boat could be used on flooded roads and as the water level is often very shallow could continue on wheels and float again as the water is deeper. An air propeller would be a simple solution even though not very efficient.
    Speed is not a consideration and 5-6 knots would be more than adequate. However, weight could be an issue. Hull should be around 4 meters. My concern is the motor. A 60hp two stroke, like Rotax 582, would give a good weight to hp ratio, but would it be enough? I also realise that air proportion is not ideal for low speed. However, this boat would be used in flood situations only and therefore cost is also a consideration.
    I very much would appreciate the input, from people with experience in this area
  2. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    I think that it will be very complicated (ie read expensive) to try to incorporate wheels as well into your airboat design.
    You would have to have a means of retracting the wheels somehow when in airboat mode, as the boat is not going to plane on the water surface with 4 wheels sticking out below the hull bottom.
    And 5 or 6 knots is probably already in planing mode for a boat that is only 4 metres long.

    Lots of info online, and impressive photos if you google 'air boats'.

    Re how speed is not an issue, it might be easier to simply push (or 'punt') the boat along using a pole (I think they call this a 'quant' in England) - you could perhaps also have a small outboard motor with a typical 'flats' design where the propeller is in a tunnel so nothing is actually sticking out below the hull bottom.
    You might even be able to get a small motor with a water jet drive, rather than a propeller? Or have a shroud around the propeller?
  3. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    Air boats were extremely popular up here especially with my parents generation. Rode all over the place in them, across Mudd flats, peat bogs, shallow water, river shoals that dried up to exposed sand banks.

    All were overcome and compensated with power. Most were heavy wall aluminum thickness plate with riveted on uhmw plate on the bottom. Driven by whatever big block was preferred by the owner. There were several bell housing adapter gear cases that converted to a propeller hub.

    One fellow had a flatbed he would push-up on and roll to his house behind an atv. (Village had most houses near the beach) Grandad said he used to push up the grass and spin around and park in the little front yard as the grass was low enough friction to get a start. Well one morning the ground was a bit frozen and throttling up to break free and start the slide down to the beach ripped the siding off the house and cracked some kitchen windows. On return the wife decided it would be trailered from that point forward..

    Mini jet boats seem to be the toy of the current generation, but my parents age there are a few guys who still have them. One fellow built a decent sized one with an ls1 he converted and built during covid.

    Guess thats the meandering way of saying horse power and uhmw can do what your wanting wheels to do. Or at least for the relatively short jaunts across wet dirt between shallow water.
    DogCavalry and bajansailor like this.

  4. portacruise
    Joined: Jun 2009
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    Location: USA

    portacruise Senior Member

    I have built water wheels into a few boats, but nothing bigger than a very lightweight two-man. The main issue from my experience over several years was that the underwater rolling surface was completely unpredictable and rarely smooth enough for rolling in the shallow water part. Also, the shallow underwater visibility was often poor. So it was easy to hang up on submerged holes, rocks, Barbed wire, tree branches, etc. In my case it was usually easy to get out and lift / push out of a stuck situation because of the lightweight construction. Using pivoting/ Swing up Wheels was helpful, especially with the speed on water part. But if you have good smooth roads with good underwater visibility ( no mud deposits) without washed out sections, and the flood waters don't deposit floating or other obstacles in the roadways, fixed underwater Wheels might work.
    Last edited: Jan 30, 2023
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