about airboats

 
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What is an Airboat ?

A buoyant, self-propelled, multi-terrain vehicle that depends primarily on air thrust for propulsion.

By this definition, simply attaching a fan to any old boat does not turn it into an airboat. There are watercraft being sold as airboats that are not ATVs.

Airboats do not use a submerged water screw and do not churn up the water. Thus, airboats are very eco-friendly.

The airboat differs from the hovercraft with respect to the amount of air cushion: An airboat may route some air from a supercharger to a cavity beneath the hull to reduce surface friction. The air cushion, however, is infinitesimal compared to a hover craft which often routes half of its power to the task of generating an air cushion.

Most airboats are about 16 feet (4.9 m) in length but they have been built as short as 6 ft. (1.8 m) and as long as 30 ft (9.1 m). A comfortable width is about 8 ft (2.4 m), which allows for a stable platform and easy trailering and trucking. There are drilling platforms and ferries, essentially air-propeller powered barges, much bigger than 8×30 ft (2.4 x 9.1 m).

The term “airboat” is not found in most abridged dictionaries.

use

What are Airboats used for?

18 seater tour boat

18 passenger tour boat with counter-rotator propeller 10 x 24 foot / 3 x 7.3 m

Airboats are used in a wide variety of applications where access (just getting there and getting back) is a problem. If the place you need to get to is in wetlands, shallow water, obstructed waterways, bogs or swamps, there are few other choices, and none more cost-effective than an airboat.

Airboats can carry heavy payloads across a variety of terrains without leaving scars on the land or polluting the waterways.

Applications include eco-tourism, search & rescue, conservation, fishing, leisure, geometrics, law enforcement and transport.

Industrial uses extend to drilling, dredging, and ferries, and some specialized adaptations are made for ice and snow in polar environments.

Read more…

seats

How many people can an Airboat carry?

30 seater tour boat

30 seater tour boat

That is a question of purpose and design. Airboat Afrika’s airboats are custom built and often range from 2 seaters for fishing (8 x 18 ft / 2.4 x 5.5 m) to large tour boats for up to 18 guests (8 x 24ft / 2.4 x 7.3 m).

Almost anything is possible however, as long as the physics work out and road transport remains viable. You wouldn’t want to have an airlift by helicopter, really.

The maximum weight load is a function of displacement (size and transom height).

The actual number of passengers depends on the seating arrangement – and the individual comfort level.

For lodge operators, we recommend a simple rule: follow the same arrangement and comfort level you provide in your open vehicle safaris. Your guests will have a consistent experience throughout their entire stay in your establishment.

A comfortable and economically reasonable size for tour boats is 8 to 12 guests, with double seated rear operators – one for the captain, one for the ranger.

An 8 ft. / 2.4 m wide bench can hold a maximum of 6 people. However, that is tight. Truly comfortable seating, leaving space for walkabouts, is 4 guests per bench. You may also consider individual seats.

A row of seats will take at least 3 ft / 0.9 m in length, and we do not recommend exceeding 3 rows in addition to the operators in the back. That way, your guests will enjoy good visibility, and your airboat will retain its speed and maneuverability.

engines

What kind of motor is used?

Early airboats used rebuilt aircraft engines. The flat 6 cylinder Lycoming was a popular power plant in the past.

So what about aircraft engines now?

Before 1980, 90% of the airboats were built with aircraft engines. 90% of airboats built since 1990 are built with automotive engines. The primary reason for this is ease of maintenance. Almost any mechanic can work on a Chevy V-8 and parts are readily available.

This is not the case with aircraft engines. To match the high torque and low rpm performance of an aircraft engine, an automotive engine must have a new cam installed or use a reduction drive.

marinized

Do Airboats use marine engines?

Some do but the only marine part actually needed is a marine air filtration system. Automotive filters do not hold up in a marine environment.

Airboat Afrika routinely replaces exposed parts with more corrosion resistant ones. Everything else is standard with the automotive industry. This means that if a fuel pump goes out, you can pick one up at the local auto parts store. (Not so easy with an aircraft engine).

The marine designation on an engine mostly refers to the cooling system which must be modified if it is to circulate salt water. This includes replacing the engine block drain plug with a corrosion resistant one. Airboats have a closed cooling system, exactly like a car, so there is no need for fully modified marine engines. Airboats typically use a high efficiency racing type aluminium radiator to reduce weight and increase corrosion resistance.

brakes

Do Airboats have brakes?

The Brakes

airboat applying water brake

Brakes are not included on a standard airboat. They are more common on airboats used on ice and consist of a hinged metal plate on the transom that flips down to increase drag. In the water, an airboat slows down rather fast when you back off the power and drop off plane.

all terrain

Are all Airboats ATV’s? [All Terrain Vehicles]

twin engine ferry, 14 x 30 foot / 4.3 x 9.1 m

twin engine ferry, 14 x 30 foot / 4.3 x 9.1 m

No, not necessarily. It’s a question of purpose and therefore, design.

Most enthusiasts believe airboats should be ATVs as the all terrain capability is their main advantage compared to alternative modes of transport. It is this versatility which gives airboats their wide range of use: eco-tourism, search & rescue, conservation, fishing, leisure, geometrics, law enforcement and transport.

Airboats which do not have to rely on ATV capacity are used in industrial operations such as drilling and dredging, and as ferries.

dry ground

Can all Airboats go over dry ground?

Even though the basic hull design may provide enough stability, many airboats are under-powered or use mismatched engine – propeller combinations resulting in poor performance on land.

There is more surface friction out of the water so additional power (torque/thrust) is required. This is achieved in four ways.

  1. use a reduction drive
  2. improve the engine’s low end performance (higher torque at lower rpms)
  3. use a propeller designed to deliver high thrust at low rpm
  4. use a properly designed engine-propeller combination

running over dry ground - up

running over dry ground - over

running over dry ground - down

running over dry ground - back in the water

reliability

How reliable is an Airboat?

Very. If asked “How reliable is your car?” you’re probably going to answer “It’s a ….. !” (Mercedes, Toyota, Landrover, … fill in the blank).

It all boils down to… the use of superior materials, better designs, superior technology, qualified mechanics, and intelligent quality control.

Airboat Afrika performs extensive quality and performance checks before delivery. Should a failure occur, it will become apparent in the first couple of hours of operation. A full day is scheduled to water test and check out each airboat. The aluminium hull is built for rugged african conditions, and all components are verified and adjusted for fine tuning.

Airboats using big block automotive engines are as reliable as their ongoing maintenance. Eventually, something wears out, but is no more difficult to repair than a car or truck engine.

In contrast to cars and 4×4’s, there are no suspensions, axles, gear boxes or differentials – there simply isn’t that much to break on an airboat. Good news, hey ?

Other than engine-prop systems, the only other moving parts are the air rudders. We haven’t come across anyone who has broken those yet.

operations

Where can an Airboat be used?

game conservation boat

game conservation boat 16 x 8 foot / 4.9 x 2.4 m twin rear operator adjustable seating + 2 double front passenger seating

Airboats are (or should be) all terrain vehicles or ATVs. They can traverse water, tall grass, marsh, mud, tundra, dry ground, log jams, small boulders, dirt roads, snow, and ice. While airboats have been used as dive platforms for underwater exploration, they are not a submersible.

Airboats have been run through grass lands, dense brush, ice jams, and over dam walls. Highly abrasive surfaces such as cement roads can be traversed but not without some wear and tear on the hull. The more abrasive the operating environment, the more polymer is added to the bottom of the hull. UHMW Polymer provides a friction-reducing surface similar to the teflon coating of your frying pan. Airboat hulls are typically clad in polymer 0.25 in. to 0.5 in. thick (6.35 to 12.7 mm).

Ice boats add polymer to the sides. The size of obstacles that can be surmounted depends primarily on the power of the engine.

sound

How can you manage the sound made by an Airboat ?

Airboat sound may come from distinct 3 sources: the engine, the hull and the propeller.

Engine sound depends on the type of engine – petrol or diesel – and its installation. Of course, the faster you go, the louder it gets. However, you don’t run your car on full power all the time either, do you ? Also, many airboats (and most aircraft) have no mufflers. Adding a muffler will reduce the engine sound considerably.

Audiogram of Airboat Sounds

Hull sounds are caused by resonance from either the engine or the propeller. The trick is to reduce reverberations as part of design and material choices. How do we do that ? We’re not going to tell you. You’ll have to buy one of our boats to find out.

Propeller sound is directly related to propeller design and speed. The primary sources of tone noise depend on the rotor tip speed and the flow conditions in which the propeller is operating. If you enjoyed physics in school, read more…

If not, read on: The most effective solution to reduce propeller sound is to reduce the rotations (rpms) the propeller needs to provide sufficient thrust. This can be done in several ways. The lighter weight composite propellers deliver more power at lower rpm and are much quieter than conventional, wooden aircraft propellers. Propeller technology has been the key improvement over the last years.

An essential part of Airboat Afrika’s customer service is to assess the operational environment your airboat will have to function in. In combination with boat size and total weight, we will design the engine-propeller combination most suitable to your needs. In some cases, it’s a good idea to install trolling motors. These are small electrical motors, installed onto the transom, operated by a hydraulic lever system. On the push of a button, they are  lowered into the water. This makes for silent approach for fishing or game viewing, provides excellent maneuverability in tight spaces, and is the only option for a reverse gear on an airboat.

(OK, that’s not entirely true. You can also push the boat – or use a large barge pole. It’s much simpler. And cheaper. Really.)

transmission

Do Airboats have transmissions?

Some people ask this question wondering if an airboat has a reverse gear. Others confuse the reduction drive with a gear box.

V8 572 cu. in. Chevrolet powering a 4-blade Whirlwind prop on a belt drive

V8 572 cu. in. Chevrolet powering a 4-blade Whirlwind prop on a belt drive

V8 engine, gear drive, counter-rotator propellers

V8 engine, gear drive, counter-rotator warp drive

An airboat has no way to change gears. Therefore, there is no reverse gear. The propeller, however, is not always bolted directly to the crank shaft. Most modern airboats have reduction drives to achieve something close to a 2 to 1 reduction. The reduction drive essentially functions the same way that the 2nd gear does in your car.

Aircraft engines are designed to produce high torque at very low rpms because prop tips break the sound barrier at about 3000 rpm. Once supersonic, the propeller loses efficiency and becomes quite noisy.

Automotive engines produce their peak power at rather high rpms (about 4000+ rpms). Airboats do not have transmissions but they can have reduction drives so you can run in the automotive equivalent of 2nd gear. To reduce the sound, a reduction gear is used to lower propeller rotations compared to the crank shaft. The most efficient prop speed is around 2,500 rpm.

speed

How fast do Airboats go?

airboat racers

airboat racers

Stripped down racing airboats can reach speeds over 135 miles per hour (217 km/h) on smooth, shallow water and accelerate in 4 seconds (1/8 mile / 200 m), according to an article in Airboating Magazine.

Speeds over 60 mph (96.6 km/h) in any watercraft are risky and not recommended. The same is true for automobiles. The differences are: (1) Roads are much more uniform (and better lit) than waterways. (2) Unlike cars, most watercraft do not have brakes.

The key feature of an airboat is its all terrain capability, not its top speed. 45 mph (72.4 km/h) on land, 60 mph (96.6 km/h) on water, and 70 mph (112.7 km/h) on ice is fast enough.