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my new prop...

Ah, OK, sorry ..... I thought you had discounted that idea.

My thinking on a tractor is that you have to deal with the sound of the prop anyway, but that if you can mask the sound of the engine behind it you should substantially reduce the sound level (apparent) for the passengers. I'm not saying that it will go away .... just that you can hide it behind the prop. And the cooling would be a big plus for an A/C boat.
 
Along a similar line....but on a slightly different trail. Many years ago when dirt was young and I was working through college, I got a job building jet engine test sound reducing baffles for a company in Tampa.

The concept was pretty simple. They had their engine on a stand and around the rear portion of the stand was a shroud. The shroud had welded wire bands that were separated and we stuffed fiberglass sheets into fiberglass cloth constructed bags. The bags were then threaded into the shrouds between the layers of welded wire. Walla....a sound absorbing baffle that worked quite well at reducing turbine whine.

Since most all airboats already have a prop cage with structural strength, would it not be possible to double layer the prop band wire and put a sound absorbing layer between the two layers of cage wire?
 
Sound reducing shrouds are easy to make BD just like you said. I put that silly band around mine sorta like a 56 crown victoria LOL, and it worked. i didnt think it worked because the sound was louder on the boat because it bounced off the bottom of the inside hull. I only blocked the tip vortices from going to the side and they went down instead after moving around the shroud.

If someone wants to get quieter by a shroud, simply put it on you can be several inches from the prop tips and it will do its job of quieting down the tip sound. The engines do not move enough to cause any damage. If you don't make it a complete circle the sound will bounce up at you from the hull but it will only be louder to you any one else will be amazed at the level of quiet you have.

Performance shrouds are a whole new ball game fellas. Sound is easy to control and cheap and not risky at all and not heavy, the one I made weighed about 5 pounds maybe 10 with the layer of felt paper I used to absorb the sound waves. I put it on my cage with zip ties, there are picture of it on here somewhere and Jim commented on it, said my boat went silent when I turned it sideways to him, I beleive it was in the salt springs run thread. There you go 20 bucks and it is a done deal, wallla quieter boat.
 
By far the best idea I have heard about this is from Norman at innovative accessories. He came up with an awesome concept for keeping a tight tolerance near the prop just like an impeller on a jet ski. The tighter the tolerance the more thrust can be generated. His idea is awesome and will work but he has came up with hundreds of other innovative ideas like this and has learned that airboaters are not willing to pay for technology like this.
 
I remember that shroud Cntry. I've been lookin at the sheet styrofoam that they insulate walls with. It would be waterproof and if it came loose I don't think it would hurt your prop.

Thunders right about the money ..... we got guys squawkin over a $250 exhaust system. I don't see many coughin up 2 Grand for a prop duct.

olf
 
I hope you can all do it, good luck. After all the people who refuse to run mufflers I believe even only a $1,000 for a shroud will be way to much for 99% of the airboaters. I must tell you even now I still have some very mad and confrontational meetings with air boaters who say (so your the @$$ hole with the quite boat thanks now the rest of have to do the same) no thanks you guy's can chase the shroud and maybe even take some heat off my back. I will continue to chase the most efficient best performing motor for an airboat that I can build.
 
Lateral sounds are mainly what we are fighting with lakefront property owners. Any reduction of appearant sound is a GOOD THING.

If a sound absorbing layer can effectively be attached to existing prop cage wire - or, if an additional layer of prop cage wire can be installed to sandwich an effective prop tip baffle on existing airboats; then it might be worth another look.
 
Right on, BD. Every little bit helps, and the kind of add-on we're talking about here will reduce 'apparent' sound ..... it's that sound that the complaints come from in my view.

olf
 
Aint that the truth Thunder LOL I used to get that same crap all the time ... and will probably again ... now that I am running again. Time will tell I guess.

The cost of the shroud like I made is about 20 bucks and it worked, the loudest area is to the side at about a 45 degree angle, it is not as loud in front or directly behind the boat. This is because of the tip vortex. the air from the prop screws up the sound waves which are just vibrations once they get twisted around they don't travel very far.

The problem with my stupid looking shroud was it was stupid looking to me. it also adds to the tracking problems in higher crosswinds.

Norman is very very very smart, he and I discussed the shroud for performance, it can be done. You are right most airboaters will not spend the type of money it would cost. the biggest cost once past the design stage would be for the product liability insurance and for the lawsuits resulting from folks modifying or copying it with bad results.

Ya'll do the shroud I'll watch
 
INCOMING leo LOL now cmon man you seen everyone fussin on here about 50 dollar mufflers you really think anyone is gonna spend 2 or 3 thousand on a shroud and add all that wieght to the boat and have to leave a cooler at home.

And should you build one and run it and it works you will be blasted for being rich and arrogant and for ruining airboating for everyone you inconsiderate so and so LOL done heard it myself man.

Remember no good deed ever goes unpunished so if your masochistic or however you spell it git-r-dun
 
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