On Sep 8, 11:23*am, wrote:
On Sep 8, 10:37*am, wrote:





On Sep 7, 10:41 pm, wrote:

On Sep 7, 10:12 pm, wrote:

On Sep 7, 10:07 pm, hk wrote:

wrote:
I was at the springs at the head of he Wacissa River this afternoon
cooling down on a hot Sept afternoon. *From far away you could hear it
coming upriver, another airboat. *I hate the damn things. *I dont hate
em for going places, I hate the noise. *So, is it the prop or engine
that makes all the noise? *Could you maybe make an effective prop that
would be less noisy?

Get a noise ordinance passed and get it enforced. That's what we did
where I lived in Florida. No airboats before or after certain hours of
the day. We also made a stink about the damned things cruising over and
cutting swaths through the wetlands.

I think they like the noise. Same sort of guys as the ones who remove
the mufflers on their motorcycles and put straight pipes on the little
Japanese cars. Big noise, small dick.

You may be right about them liking the noise. *Maybe this is a techno-
opportunity to find a way around the noise generation. *A little
searching shows that major noise is from the prop although many boats
have unmuffled engines too. I wonder if putting a cowling around the
prop would work, somebody must tried this.

Found a DTIC report (that I do not want to pay for) saying that a
cowling and redesigned multiblade prop will reduce prop noise.
Another report from the nature Conservancy discusses noise and finds
that muffling always helps some. *They also say that noise is worst at
high prop tip speeds so it is best to go with a multiblade prop.
Worst noise whn one is attempting to get underway from land or sandbar
or to get unstuck.
So, is this an opportunity for someone to make composite airboat props
with multiple blades to replace all the old ones with two blades?

I cannot jump on these airboat ppl too much for being ignorant
rednecks, partly because I ma probably related to em and partly
because airboats do have good uses. *The Wacissa is a place for em as
the water is often so shallow and covered with hydrilla. *It would
really make people like them if the noise could be significantly
reduced. *They seem to have enough power to be able to reduce noise
somehow. *Maybe radically re-think the whole concept. *At very least
put cowlings around the blades so the noise goes up or back rather
than be emitted in all directions.- Hide quoted text -

- Show quoted text -

WTF? Can't they put a muffler system on them, or is it the blades that
make the most noise?- Hide quoted text -

- Show quoted text -

Normal IC aircraft engines aren't muffled, and the back pressure has
an affect on them if you try to.
I took an airboat ride once. Stopped at a bar in South Florida that
was right on the swamp. Several airboats at the docks. Never been on
one, so I asked the barkeep who in there might give me a ride. Big old
swampbilly says "buy me a beer, I'll take ya". Off we go! I've gone
fast all of my life and he still managed to scare me some! When we
turned around he just hammered that thing and hit a small hammock
(little islands in the swamp) going like a bat out of hell!

On Mon, 8 Sep 2008 08:31:27 -0700 (PDT), wrote:

Normal IC aircraft engines aren't muffled, and the back pressure has
an affect on them if you try to.

Most, maybe all, of the planes I have experience with have had
mufflers. Includes radial engines from the thirties, and the usual
Piper, Beech, and Cessna planes in use from the forties on. Still
loud, every one of them.

Casady

On Sep 8, 1:33*pm, (Richard Casady) wrote:
On Mon, 8 Sep 2008 08:31:27 -0700 (PDT), wrote:
Normal IC aircraft engines aren't muffled, and the back pressure has
an affect on them if you try to.

Most, maybe all, of the planes I have experience with have had
mufflers. Includes radial engines from the thirties, and the usual
Piper, Beech, and Cessna planes in use from the forties on. Still
loud, every one of them.

Casady

From what loogie suggests, the engines may not run if muffled too
much. Is there ways to do it? Could these boats be made to be somewhat
sane? I know that with our bikes there are trick pipes that are very
loud, but several private tracks we frequent won't allow them. Guys
have to change pipes and rejet to ride there, but it can be done... I
don't think there is a lot of reason for a pleasure boat to be so
loud, although I do not have problems with loud vehicles in sanctioned
races, with proper permits and such...

On Mon, 8 Sep 2008 10:53:44 -0700 (PDT),
wrote:

On Sep 8, 1:33*pm, (Richard Casady) wrote:
On Mon, 8 Sep 2008 08:31:27 -0700 (PDT), wrote:
Normal IC aircraft engines aren't muffled, and the back pressure has
an affect on them if you try to.

Most, maybe all, of the planes I have experience with have had
mufflers. Includes radial engines from the thirties, and the usual
Piper, Beech, and Cessna planes in use from the forties on. Still
loud, every one of them.

Casady

From what loogie suggests, the engines may not run if muffled too
much. Is there ways to do it? Could these boats be made to be somewhat
sane? I know that with our bikes there are trick pipes that are very
loud, but several private tracks we frequent won't allow them. Guys
have to change pipes and rejet to ride there, but it can be done... I
don't think there is a lot of reason for a pleasure boat to be so
loud, although I do not have problems with loud vehicles in sanctioned
races, with proper permits and such...

They require mufflers on sprint cars at many tracks.

Casady

On Sep 8, 2:14*pm, (Richard Casady) wrote:
On Mon, 8 Sep 2008 10:53:44 -0700 (PDT),





wrote:
On Sep 8, 1:33*pm, (Richard Casady) wrote:
On Mon, 8 Sep 2008 08:31:27 -0700 (PDT), wrote:
Normal IC aircraft engines aren't muffled, and the back pressure has
an affect on them if you try to.

Most, maybe all, of the planes I have experience with have had
mufflers. Includes radial engines from the thirties, and the usual
Piper, Beech, and Cessna planes in use from the forties on. Still
loud, every one of them.

Casady

From what loogie suggests, the engines may not run if muffled too
much. Is there ways to do it? Could these boats be made to be somewhat
sane? I know that with our bikes there are trick pipes that are very
loud, but several private tracks we frequent won't allow them. Guys
have to change pipes and rejet to ride there, but it can be done... I
don't think there is a lot of reason for a pleasure boat to be so
loud, although I do not have problems with loud vehicles in sanctioned
races, with proper permits and such...

They require mufflers on sprint cars at many tracks.

Casady- Hide quoted text -

- Show quoted text -

Same with MX racing with N.E.M.A.. they have a sound check before
races but the levels are high. It is some of the private tracks where
they are more strict. Like I said, the NEMA races are sanctioned and
within the zoning and other guidelines as agreed with the local
communities.. But they do have limits.. My question is, is it possible
for these airboats to run at all within tolerable noise levels, or do
the engines just make that impossible? If so, maybe they need to find
an alternative power source, or a more suited tool.. Just because
something works, doesn't mean it's the best tool for the job. Who
hasn't used a screwdriver as a prybar

On Mon, 8 Sep 2008 11:25:07 -0700 (PDT),
wrote:

On Sep 8, 2:14*pm, (Richard Casady) wrote:
On Mon, 8 Sep 2008 10:53:44 -0700 (PDT),





wrote:
On Sep 8, 1:33*pm, (Richard Casady) wrote:
On Mon, 8 Sep 2008 08:31:27 -0700 (PDT), wrote:
Normal IC aircraft engines aren't muffled, and the back pressure has
an affect on them if you try to.

Most, maybe all, of the planes I have experience with have had
mufflers. Includes radial engines from the thirties, and the usual
Piper, Beech, and Cessna planes in use from the forties on. Still
loud, every one of them.

Casady

From what loogie suggests, the engines may not run if muffled too
much. Is there ways to do it? Could these boats be made to be somewhat
sane? I know that with our bikes there are trick pipes that are very
loud, but several private tracks we frequent won't allow them. Guys
have to change pipes and rejet to ride there, but it can be done... I
don't think there is a lot of reason for a pleasure boat to be so
loud, although I do not have problems with loud vehicles in sanctioned
races, with proper permits and such...

They require mufflers on sprint cars at many tracks.

Casady- Hide quoted text -

- Show quoted text -

Same with MX racing with N.E.M.A.. they have a sound check before
races but the levels are high. It is some of the private tracks where
they are more strict. Like I said, the NEMA races are sanctioned and
within the zoning and other guidelines as agreed with the local
communities.. But they do have limits.. My question is, is it possible
for these airboats to run at all within tolerable noise levels, or do
the engines just make that impossible? If so, maybe they need to find
an alternative power source, or a more suited tool.. Just because
something works, doesn't mean it's the best tool for the job. Who
hasn't used a screwdriver as a prybar

As soon as you start enlarging the airframe to accommodate large
effective mufflers, they will starting impacting speed and range.
They will have weight regardless of any drag penalty. Earplugs or
radio headsets are much cheaper. During the SEA war games, the CIA
had a powered sailplane with effective mufflers and a zillion blade
low speed prop and which was nearly silent.

Casady

On Sep 8, 1:33*pm, (Richard Casady) wrote:
On Mon, 8 Sep 2008 08:31:27 -0700 (PDT), wrote:
Normal IC aircraft engines aren't muffled, and the back pressure has
an affect on them if you try to.

Most, maybe all, of the planes I have experience with have had
mufflers. Includes radial engines from the thirties, and the usual
Piper, Beech, and Cessna planes in use from the forties on. Still
loud, every one of them.

Casady

Expansion chambers.

They aren't really mufflers, but are designed to make some
backpressure in normally aspirated engines. My uncle was an aviation
machinist. Been around small IC engined aircraft a lot!

On Sep 8, 2:29*pm, wrote:
On Sep 8, 1:33*pm, (Richard Casady) wrote:

On Mon, 8 Sep 2008 08:31:27 -0700 (PDT), wrote:
Normal IC aircraft engines aren't muffled, and the back pressure has
an affect on them if you try to.

Most, maybe all, of the planes I have experience with have had
mufflers. Includes radial engines from the thirties, and the usual
Piper, Beech, and Cessna planes in use from the forties on. Still
loud, every one of them.

Casady

Expansion chambers.

They aren't really mufflers, but are designed to make some
backpressure in normally aspirated engines. My uncle was an aviation
machinist. Been around small IC engined aircraft a lot!

AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!
COULD THEY MAKE THEM QUIETER IF THEY WANTED TO?????????

Please answer me..... I gotta' know... sniff

On Sep 8, 2:35*pm, wrote:
On Sep 8, 2:29*pm, wrote:





On Sep 8, 1:33*pm, (Richard Casady) wrote:

On Mon, 8 Sep 2008 08:31:27 -0700 (PDT), wrote:
Normal IC aircraft engines aren't muffled, and the back pressure has
an affect on them if you try to.

Most, maybe all, of the planes I have experience with have had
mufflers. Includes radial engines from the thirties, and the usual
Piper, Beech, and Cessna planes in use from the forties on. Still
loud, every one of them.

Casady

Expansion chambers.

They aren't really mufflers, but are designed to make some
backpressure in normally aspirated engines. My uncle was an aviation
machinist. Been around small IC engined aircraft a lot!

AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!
COULD THEY MAKE THEM QUIETER IF THEY WANTED TO?????????

Please answer me..... * I gotta' know... sniff * - Hide quoted text -

- Show quoted text -

There is not really any reason they could not have mufflers on the
engine. It would probably take a few mph off the top end. But much
of the noise is from the prop. Many simply bolt the prop to the
engine output so there is not a lot you can do with prop redesign.
More blades may allow you to run a smaller diameter but probably not a
lot smaller. So the prop tip speeds are still going to be pretty
high.

On Mon, 8 Sep 2008 11:56:46 -0700 (PDT), wrote:

On Sep 8, 2:35*pm, wrote:
On Sep 8, 2:29*pm, wrote:





On Sep 8, 1:33*pm, (Richard Casady) wrote:

On Mon, 8 Sep 2008 08:31:27 -0700 (PDT), wrote:
Normal IC aircraft engines aren't muffled, and the back pressure has
an affect on them if you try to.

Most, maybe all, of the planes I have experience with have had
mufflers. Includes radial engines from the thirties, and the usual
Piper, Beech, and Cessna planes in use from the forties on. Still
loud, every one of them.

Casady

Expansion chambers.

They aren't really mufflers, but are designed to make some
backpressure in normally aspirated engines. My uncle was an aviation
machinist. Been around small IC engined aircraft a lot!

AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!
COULD THEY MAKE THEM QUIETER IF THEY WANTED TO?????????

Please answer me..... * I gotta' know... sniff * - Hide quoted text -

- Show quoted text -

There is not really any reason they could not have mufflers on the
engine. It would probably take a few mph off the top end. But much
of the noise is from the prop. Many simply bolt the prop to the
engine output so there is not a lot you can do with prop redesign.
More blades may allow you to run a smaller diameter but probably not a
lot smaller. So the prop tip speeds are still going to be pretty
high.

I just spoke with a young man in Orlando. He's at Don George
Aircraft Engines & Parts
Orlando, Florida 32805
407.422.0188

I remembered that the airboat I rode on had a Lycoming engine, which gave
me a starting place. According to the guy I spoke with, the law in Florida
requires mufflers on *all* airboat engines. The loudness comes from the
propellor. Problem solved.