Mufflers and Exhaust

[micaheli]

This post is regarding noise versus performance.

Lets say I run my boat in a private lake and want to keep nitro noise down to a minimum. Could I fasion a muffler for my boat? I want my boat to hum like modern vehicles do. Would this amount of backpressure kill the engine? I have yet to experiment with this. Going to bench test this with a couple make-shift exhaust pipes.

I suppose my questions are: Has anybody experimented with this? What happened? What kind of performance loss is there.

My boats specs:
Dumas Big Swamp Buggy
OS 91 Four-Stroke Surpass w/3 blade prop (I can afford the power loss obviously)

This thing screams - WAY too fast anyways.. a muffler might be the thing it needs to keep it under control.. Ooh Ooh. I know.. a catalytic converter... gotta keep those emissions down. hehe. anyways. Am I being a retard? or are these concerns that everyone has.... I'm leaning toward retard.

[RickE]

Don't put yourself down-anybody who cares to quiet-down a R/C boat is a good guy! If you can, checkout the June 2002 issue of R/C Boat Modeler Magazine-there's an article on making cheap and easy mufflers that you might apply to your hull. If that idea seems unsuitable, you might add a muffler like the one Prather sells via a silicone hose made to connect a pipe to a header.

Hope this helps,
RickE

[Twmaster]

He needs an airplane muffler. Dumas Swamp Buggy is an airboat. Prolly best to ask your LHS or ask in the airplane forums. Does it have a muffler now? I have seen some very quiet stock OS muffler setup on planes.

And I too applaud you for making the effort to quite the thing down.

Cheer's,

Mike N
Twmaster

[micaheli]

Okay. Well, the first post rang an interest.. the second one didn't make any sense. As long as it fits in the boat, it shouldn't matter what kind of muffler it is. An engine is an engine. The only difference should be the RPM at which the engine is spinning and even then I don't think its that big of a difference. Anyways, I'm going to try a couple things and try to get ahold of that issue of boat modeler. Because I think a muffled (moreso than stock) 91 surpass would sound SWEET in an airboat. I'm also working on a metal tube frame propeller shroud as a decent workaround for the pile of crap shroud Dumas gives you to work with. Mine came broken in the box. :) Which doesn't surprise me as its the most flimsy piece of wood in the box.

Anyways, thanks for the replies! I'll give this a whack and see what I come up with! Any MORE replies are welcome.

--Micah Morton

[Twmaster]

Originally posted by micaheli
... the second one didn't make any sense. As long as it fits in the boat, it shouldn't matter what kind of muffler it is. An engine is an engine.

Well I suppose I should have been more clear. My point is that there are lots of good quality mufflers available off the shelf for your motor. Since it is an airboat it just seems logical to put an AIRCRAFT muffler on it. Why re-invent the wheel?

Mike N
Twmaster

[micaheli]

Because the wheel sucks -- Why roll when you can fly, or teleport, or bring your destination to you. :) In my mind, everything and anything can be improved by innovation. So off I go to innovate. :) I got myself some 1/2inch copper pipe to start off with.. figure I'll get clever somewhere down the line. going to start my modifications this week.. lets see where this takes me. :)

--Micah

[ak_boater]

OK, Don't slaughter me if this is totally dumb. But I'm thinking you might try running a tube off the end of your exhaust (muffler or whatever) down into the water. This is how "real" boat exhausts work and it keeps things very quiet at idle and slow speeds when the hose is submerged. Of course when you really get going the hose isn't underwater anymore usually so things get a bit louder.

[micaheli]

I was thinking something like that.. just enough so that when the boat is dead-float, full tank, the pipe is just barely under. then when you get going, its not under anymore, but still directing the sound waves to the water. My only concern is backpressure.. I wonder how much is too much for a 91 surpass. :) Suppose we'll find out. hehe

--Micah