NEW INFO on an old QUIET Plane !

A discussion on ways to reduce it.
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Whitebear
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NEW INFO on an old QUIET Plane !

Postby Whitebear » Sun Jan 16, 2011 1:08 pm

Image

Don't know much about this, just thought it was a cool picture!
Update: It's a Lockheed YO-3 'Quiet Star'. Designed for night battlefield observation during the Vietnam war. It was a very quiet plane, and can fly as low as 200 ft over the enemy without being heard. Thanks to Charlie Baumann for the ID!
Christian Jacobsen had this to add about this plane: "One of the programs I saw while I was at NASA was a project for developing quieter helicopter rotors (or for downtown VTOL public airports). They would mount microphones on the wings of the YO-3 and follow our helicopters around to do real-world testing of the various rotor designs. (A Blackhawk, an Apache, and a Little Bird.) Because it could fly slowly, silently, and close to the helicopters, it was the perfect platform for the audio testing aspect of the project."
"Every aspect of the plane was developed to be as quiet as possible... which was part of the reason it had that odd looking wooden propeller. Apparently it was the quietest prop ever made!"
Got the following from Kurt Olney, who was a crew chief on a YO-3A in Vietnam, and was helping out at Edwards with the plane: "The elements that made the plane ulltra quiet--some might say silent when it flies 800-1000 feet overhead--were the following 1. Slow turning prop 700 rpm (minimizes tip noise.) 2. An exhaust system that runs the length of one side of the airplane, 3. IO-360 continental engine enclosed in acoustic deadening cowling and silicone in the rocker box covers 4. 12 v-belts--reduction drive- (we use to call them rubber bands) that eleminate gear noise. 5. A streamlined plane. (plane is based on a Schweizer 2-32 glider but greatly modified.) 6. Duct tape. Before planes went on a mission, they would fly about 300 feet over the maintenance shack. If we heard whistles, rattles etc, we would bring her in put some tape on her. After a while we pretty much knew where the problems were likely to be so we taped her before she went up."

Taken from photo and caption found at:
http://home.comcast.net/~bzee1a/Edwards ... rds09.html
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Re: NEW INFO on an old QUIET Plane !

Postby Ruagatr » Sun Jan 16, 2011 1:29 pm

Very cool...never saw that before..thanks Scotty.

Charles

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grant
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Re: NEW INFO on an old QUIET Plane !

Postby grant » Sun Jan 16, 2011 1:37 pm

Cool find!

Got all the right things going for it....A/C motor, wood prop and duct tape! :D :D
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Re: NEW INFO on an old QUIET Plane !

Postby 4 pistons and a Prop » Sun Jan 16, 2011 2:16 pm

Being as its 40 year old technology, sensenich or whirl whind or any propeller manufacturer ought to inquire on the airfoil for that prop and develop a carbon fiber adjustable blade version, and maybe even develop a gear reduction box for standard 4 cylinder lycomings/continentals, and 6 cylinder motors for the cause, with the size of their business they could absorb the upfront costs testing and re tooling, while the rest of us continue to plug away at the exhaust issues, which is a smaller component of airboat noise. Right now if you want top thrust/power out of a 4 cyl A/C motor you need a warp drive or other loud composite prop with high tip speeds.

That prop looks alot like the big wide slow spinning car reduction props out there today- imagine that. There is a need for this technology in the A/C world bring it on, so we can truly make a difference in airboat noise. JMO.
when in doubt power out.

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Re: NEW INFO on an old QUIET Plane !

Postby Whitebear » Sun Jan 16, 2011 4:29 pm

They gave away the biggest tip so far for engine sound reduction in that LONG exhaust. Plus the rocker boxes coated with silicone.

Nearly every thing they mentioned that they did all those years ago back in the Vietnam era, has been experimented with during the quiet airboat competition. I remember more than one mentioning the long exhaust pipes.

During that era I don't think there were any gear reductions available. I'm not certain WHEN the Franklin Belt Drives came on the market. From what I hear however, some of the new gear drives are every bit as quiet as the belt drives. Or so they claim.

Its has long been known that reduction of sound is mostly by getting the tip speed way down. In their case around 700 RPM. However blade profile is the secret to performance WITH sound reduction.

To my way of thinking when quiet is the main concern then top thrust is secondary to quiet.

Its just fascinating to me to see these big boys had it pretty much down back int he 60s. Before we ever thought of quiet as something desirable.
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Re: NEW INFO on an old QUIET Plane !

Postby cntry141iq » Sun Jan 16, 2011 6:46 pm

yep known about it for years ... nobody wants to hear about it ... slow prop speeds .. v belt reduction ... great exhaust system .. sound proof cowlings .. all adds up to money and work plus it doesn't sound like a hotrod so why run it .. LOL it aint our heritage or right to be quiet on an airboat ... runem loud ... runem proud until after we have made em be banned then its oh we can get em quiet .. sorry too late we done banned them ... it is quiet now ...
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Re: NEW INFO on an old QUIET Plane !

Postby 4 pistons and a Prop » Sun Jan 16, 2011 8:06 pm

Number one noise issue was the prop not exhaust- they geared it to .2 mach, and designed an airfoil to provide adequate thrust.

Number two noise issue was the gearbox not exhaust-they used V-Belts: Beyond slowing the prop and shaft, it decoupled and insulated them from engine torque - pulse vibrations.

Number three noise issue was exhaust- they used two buick automobile mufflers and 26 feet of double wall silenced piping- good luck putting that on a boat.

Number four noise issue was the engines rotating assy.- a highly sealed and insulated shroud was built (I belive CHT's would go through the roof on an airboat), and a highly modified IO 360 continental A/C engine.

Number five noise issue was the fuselage, in which large amounts of duct tape were used.

The project was initiated to locate specific locations of enemy hideouts, without being discovered- DARPA, Dod, CNO, et al, and other government agencies spent 10 Million in research and tried countless prop configurations and 12 gearbox designs before getting a quiet enough plane. The prop and gearbox were the primary noise issues per the 6th Triennial Vietnam Symposium a Texas Tech University in Lubbock, TX on 3/15/08.

Good reading though and not a simple fix to our issues, but a decent starting point.
when in doubt power out.

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Re: NEW INFO on an old QUIET Plane !

Postby WOOD » Mon Jan 24, 2011 8:22 am

WELL SAID COUNTRY------THE NUMBER 1 COMPLAINT ABOUT AIRBOATS IS NOISE. THIS STATE IS GETTING MORE POPULATED EVERY DAY, I DON'T LIKE IT BUT THERE IS NOT ANYTHING ANY OF US CAN DO ABOUT IT. I HAVE OWNED AN AIRBOAT SINCE 1964 AND I WOULD LIKE FOR MY CHILDREN AND GRANDCHILDREN TO CONTINUE TO ENJOY WHAT I HAVE FOR MANY YEARS. IF THE AIRBOAT COMMUNITY DOES NOT ADAPT TO THE CHANGING OF TIMES AIRBOATS WILL BE HISTORY IN MANY AREAS OF FLORIDA.

cntry141iq
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Re: NEW INFO on an old QUIET Plane !

Postby cntry141iq » Mon Jan 24, 2011 5:24 pm

Everybody who has been on here for very long know's how I feel about a quiet airboat ... and it can be done. Yes it costs money and takes work and no it is not perfect but it helps. 6" long hollow pipes that are called mufflers are not gonna get it much longer. Loud props are not gonna get it much longer and no manufacturer is gonna swap new props for old props. The easiest way to quiet airboats is to simply ban them plain and simple it is a 100% effective method to reduce noise. More and more places are gonna use that tactic one little area at a time so as not to draw too much attention .. lawsuits are expensive and even if FAA wants too they are not going to be able to sue everyone of the municipalities that go that route.

So that leaves it up to us doesn't it. What are we going to do about it .. puff all up and yell and cuss act like a bad arse LOL yeah that will work. Or just maybe we ought to give some thought to a/c gear boxes and slower turning props and full exhaust systems and drivin more courteous around houses ... ya think. Yep all that stuff costs money but if your gonna play your gonna pay .. you can't go run your race car if you don't build a roll cage in it, many tracks make you run mufflers of some sort even at the drag strips .. many tracks have curfews ... ata certain time the race is over no matter what ... so who knows .. I just know nothing stays the same .. ask the dinosaurs .. if you can find one LOL
Don't waste your time ... it is the only thing you can't get more of
.. if it accidentally looks like I gave advice please ignore it .. and notify me immediately


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