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How Fast Do
Airboats Go?
Stripped down racing Airboats can reach
speeds over 135 miles per hour on smooth,
shallow water and can reach this speed in 4
seconds (1/8 mile), according to an article
in U.S. Airboat magazine. Speeds over 60 mph
in any watercraft is can be risky and is 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.
Stan Floyd, the president of the American
Airboats Corporation, holds the official
land speed record of 47.76 m.p.h. which was
set in a standard American Air-Ranger at the
Houston, International Dragway in September,
1995.
Forty-eight m.p.h. and an elapsed quarter
mile time of 21.26 sec. doesn't sound that
fast until you consider that it was set in a
standard 300 h.p. 3-seat airboat not a
stripped down hot-rod. The record was also
set on asphalt. Going across a grassy
meadow, this airboat could easily top 55
mph. |
Can
Airboats go across land?
All Air Rangers can but many airboats are
under-powered or use mismatched engine-prop
combinations resulting in poor performance
on land. There is more surface friction on
land so additional power (torque/thrust) is
required. This is achieved four ways. |
Are all
airboats atv's? (all terrain vehicles)
No! We at American Airboats believe that
they should be and design our boats
accordingly. The ability to hit 45 mph on
dry land is one of the design parameters for
an AirRanger. |
Do
Airboats Have Brakes?
Brakes 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. |
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. American Airboats
routinely replaces exposed parts with more
corrosion resistant ones but this is more
cosmetic than absolutely necessary.
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
beefed up if it is to circulate salt water.
Beefing up 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 engine.
Airboats typically use a high efficiency
racing type aluminum radiator to reduce
weight and increase corrosion resistance.
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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.
An airboat has no way to change gears. The
propeller, however, is not always bolted
directly to the crank shaft.
Some airboats have reduction drives (usually
belt drives) to achieve something close to a
2 to 1 reduction. The drive functions the
same way that 2nd gear does in a car.
Automotive engines must turn high
revolutions (rpms) to achieve their peak
horsepower. Aircraft engines achieve peak
horsepower at low revolutions (about 2500
rpm).
Cars running in second gear will accelerate
quicker and climb steeper hills. The same is
true for an airboat with a reduction drive.
The reason that people do not cruise in
second gear is because it burns more gas and
produces more noise. This is not necessarily
true in an airboat application - it depends
on the prop that is used. An engine with a
reduction drive will swing a bigger prop (or
a prop with more blades).
Most of the noise created by an airboat
comes from spinning the prop over 3000 rpms.
It is prop noise not engine noise. A bigger
prop turning lower rpms will produce the
same thrust as a small prop at high rpms and
produce less noise. |
How do you
get high torque (thrust) at low propeller
RPMs?
There are four ways:
- Use a
reduction drive, {usually a 2:1 belt-drive
reduction}
- Install a
cam that improves the engines low end
performance
(higher torque at lower rpms)
- Use a
propeller designed to deliver high thrust
at low rpm
- Use an
engine designed to turn a propeller.
(aircraft engine)
The most
economical solution is to install a new cam
in an automotive engine. The best solution
is to use a high performance automotive
engine with a reduction drive in combination
with a high output adjustable pitch
propeller.
Aircraft engines are great because they
produce high torque at low revolutions (peak
power at around 2800 rpm) but they can be
very expensive to purchase and even more
expensive to maintain. Any mechanic can fix
a Chevy 454. An aircraft engine usually
requires an aircraft mechanic. |
Why is
the prop in the rear?
Today, almost all airboats are rear prop
pushers but it was not always the case.
Rumor has it that the first airboats had the
prop mounted in the front which quickly led
to the invention of goggles and ear plugs.
For many reasons using a rear mounted engine
and prop to push the craft worked much
better the other designs. |
Do all
Airboats use aircraft engines?
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.
Most American Airboats are fitted with
either small small block 350 cu. in. or big
block 454 cu. in. Chevy engines. Horsepower
depends on performance options. |
How many
people can an Airboat carry?
An 8 ft. x 20 ft. tour boats are typically
designed to carry 12 people. IT has two 8
ft. bench seats which can hold about 6
people (or 4 with 2ft beams). In addition
there are two jump seats on either side of
the pilot.
The maximum load is a function of
displacement (size and transom height). The
number of passengers depends on size and
seating arrangement. Some airboats can carry
loads of 6,000 lbs. or more.
A Minnesota hunting and fishing guide
requested a boat that would carry 6
passengers and 1000 lbs. of gear over water
and obstacles at 45 mph for 800 miles. He
made this request after tearing up his third
water screw on an expedition 100 miles from
the nearest phone. This type of accident
would never happen in an airboat |
How reliable
is an Airboat?
Airboats (using Chevy V-8 engines) are about
as reliable as a Chevy truck. Eventually
something breaks down but it is not that
much of a hassle to repair. About the only
problem that we have had that required the
assistance of a rescue boat was a fuel pump
failure. We now carry a spare fuel pump on
all trips over 100 miles.
American Airboats have an edge on
reliability due to the use of superior
materials, better designs, superior welders
and mechanics, and better quality control.
Each boat receives and extensive quality and
performance check before delivery. Most
failures occur in the first couple of hours
of operation so we take a day to water test
and fully check out each boat.
The American aluminum hull is the industry
standard for rugged reliability. Most of the
other parts are purchased from suppliers.
They can be purchased by any boat builders.
Other than the hull, the difference between
manufacturers is primarily a matter of
vendor selection, buying the best
components, correct assembly (which is
related to the expertise of their workers
and quality control), and fine tuning.
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Who
Built the First Airboat?
Alexander Graham Bell, who carried out many
experiments with aircraft and water craft
after the success of his telephone, built an
airboat in 1905 in Nova Scotia. The craft he
and his engineers built was dubbed the "Ugly
Duckling". The craft was primarily used to
test aircraft engines and props. Some Cajuns
in southern Louisiana claim their granddads
built airboats using Model T engines and
hand crafted props. |
Where can an
Airboat be used?
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 (as the cartoon indicates) a
submersible.
They have been run through grass lands,
dense brush, ice jams, and over dikes.
Highly abrasive surfaces such as cement
roads can be traversed but not without some
wear and tear on the hull. The more abrasive
the surface, the more polymer that is added
to the bottom of the hull. UHMW Polymer
provides a "teflon" like friction reducing
surface. Airboat hulls are typically clad in
polymer 1/4 in. to 1/2 in. thick. Ice boats
add polymer to the sides.
The size of obstacle that can be surmounted
depends primarily on the power of the
engine. 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 very 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 rather
than 4th gear. So, one can decide to run in
4th gear or 2nd gear. To increase the
effective power, a reduction gear is used so
the prop spins at a lower speed than the
crank shaft. An automotive engine often
produces its peak horsepower at 5000 rpm.
The most efficient prop speed is around
2,500 rpm. |
What is
the definition of "Airboat"?
A buoyant self propelled multi terrain
vehicle that depends primarily on air thrust
for propulsion. Does attaching a fan on a
jon boat turn it into an airboat? Not by
this definition. 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. Except for
the noise, airboats are very eco-friendly.
The airboat differs from the hover craft
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 in length
but they have been built as short as 6 ft.
and as long as 30 ft. There are drilling
platforms, which are essentially air-screw
powered barges, that are much bigger than
8x30. The 8 ft. width is about the maximum
width for easy trailering and trucking.
The term "airboat" is not found in most
abridged dictionaries. |
What are
Airboats used for?
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,
swamps, or in a pantanal, 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. |
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. Today, the
most popular power plant is a Chevy 350 cu.
in. V-8. For overland use, a 454 cu in.
Chevy or Ford is the most popular choice.
Just about any engine can be used but they
should be adapted to a marine environment.
When an automotive power plant is used, it
can be easily serviced by most any mechanic.
Parts are also readily available. |
How can you
reduce the noise that an Airboat makes?
Noise is generally related to prop speed.
One way to reduce prop noise is to reduce
the spin rate or rpms that the prop turns to
provide the needed thrust. This can be done
several ways.
The lighter weight composite props deliver
more power at lower rpm and produce less
noise. This has been the key improvement in
the last 5 years.
Many airboats (and most aircraft) have no
mufflers. Adding a muffler will reduce the
engine noise.
Many of the ways to reduce the amount of
vibration and noise transmitted to the
aluminum hull are proprietary. Some hull
coatings will reduce noise. |
How many
Airboats are in use around the world?
We are working on this one. American
Airboats are used in over 15 countries but
we do not have an industry total. |
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