Running Quiet is Possible!

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Blackout

Blackout

Well-Known Member
Joined
Sep 10, 2008
Messages
1,610
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I modified a NR 46 muffled pipe by welding on a 7" long tube with baffles spaced 1 1/4" apart. It's a straight through design similar to a Maxim firearm silencer. The engine seems to make good power still and was running at 78 dbA this weekend. I added 4 muffling chambers with this design. This is quieter than my water injected CMB Quiet pipe and seems to work better for the NR 46 engine. Tube O.D. is 1.25" with a .035" wall thickness. Baffle hole diameter is .375". The baffles are cut from .040" aluminum sheet using a 1 3/8" bi-metal hole saw. I then turned them down slightly on a drill press with a file.
 
Craig's boat showed no loss of power/speed with the modified pipe on his 45 NR JAE. Will be asking him to modify our pipes for next year.

btw - thanks Craig for all your help yesterday with our boats. Hopefully the water won't freeze and we'll have another warm weekend in upstate NY for testing.

Tom & Cindy
 
Randy Rapedius said:
What was the recorded speed?
Click to expand...
No speeds were recorded as my GPS does not fit in this boat too well, but the boat felt no slower than before. Should have taped the GPS to the tub top, but forgot. I was having too much fun doing laps, knowing that snow will be coming soon.....
 
Do you care to show more pics of the pipe. I would like to do something similar. What the diameter of the silenced section.
 
craig , two thumbs up on your quite pipe , ....how do you attach the internal baffles to the walls of the pipe ?....are they welded in place ?....bob
 
Blackout said:
Randy Rapedius said:
What was the recorded speed?
Click to expand...
No speeds were recorded as my GPS does not fit in this boat too well, but the boat felt no slower than before. Should have taped the GPS to the tub top, but forgot. I was having too much fun doing laps, knowing that snow will be coming soon.....
Click to expand...
One more reason to run gas boats. Lol.

Lots of room for GPS' :)

Glad to hear your design works.
 
Samuel Hagan JR said:
Do you care to show more pics of the pipe. I would like to do something similar. What the diameter of the silenced section.
Click to expand...
I forgot to take pictures before having my friend TIG weld it. The o.d. of the muffled section is 1.25" aluminum with a .035" wall thickness. I bought the material from www.onlinemetals.com.
 
bob miller said:
craig , two thumbs up on your quite pipe , ....how do you attach the internal baffles to the walls of the pipe ?....are they welded in place ?....bob
Click to expand...
Hi Bob,

Yes, the baffles are TIG spot welded. Where the spot welds are, I drilled small holes in the 1.25" silencer tube. The baffles were sized to be a press fit and I positioned them at the drilled holes. Hopefully the 4 tack welds per baffle will keep them in place. The baffles are .040" thick, but next time I might go to .063" so there is more surface area for the spot weld to bite to.

I will be designing a tuned muffler for my NR .21 outboard this winter. It will not use these baffles, but use a tube with drilled holes similar to the NR Quiet pipe. Going to do it that way so there will be more effective volume in the muffler as it will also be doing the job of a pipe. Unlike the K&B and O.S. mufflers, I will be able to change the length to tune the engine. I'll post when I have the prototype done, but testing won't be till spring.

I won't be holding any of Pete's NY series races next year at my pond. I still need more time to get quieter and get my ducks in a row. The town's sound ordinance is crazy low for agricultural land and no point in taking a test if I know I will fail..... But, 2015 is always a possibility. With that being said, I plan to hold a couple one-day races in 2014 that will run under a 82dbA rule. I held one this fall and it worked out pretty good.
 
stan simpson iv said:
Have you tried running the pipe on the right hand side of the boat? For handling purposes...
Click to expand...
No, but the aluminum adds very little weight, and it's still somewhat close to center, but would be something to consider. With that being said, this boat handles very well so far. :)
 
Blackout said:
I won't be holding any of Pete's NY series races next year at my pond. I still need more time to get quieter and get my ducks in a row. The town's sound ordinance is crazy low for agricultural land and no point in taking a test if I know I will fail..... But, 2015 is always a possibility. With that being said, I plan to hold a couple one-day races in 2014 that will run under a 82dbA rule. I held one this fall and it worked out pretty good.
Click to expand...
Maybe it's time the club started to seriously look into finding another site to hold a race at?

D1 could use another race and like I said before you have a great group of people to help put it on.

Tim
 
Your not the only one working on quieting his boat down for next year. B)

2013-11-18 17.03.39.jpg
 
Last edited by a moderator:
Tim Kish said:
Blackout said:
I won't be holding any of Pete's NY series races next year at my pond. I still need more time to get quieter and get my ducks in a row. The town's sound ordinance is crazy low for agricultural land and no point in taking a test if I know I will fail..... But, 2015 is always a possibility. With that being said, I plan to hold a couple one-day races in 2014 that will run under a 82dbA rule. I held one this fall and it worked out pretty good.
Click to expand...
Maybe it's time the club started to seriously look into finding another site to hold a race at?

D1 could use another race and like I said before you have a great group of people to help put it on.

Tim
Click to expand...
I know of another pond. A club member talked to me about it this past weekend. I have not discussed it with the rest of the club yet. It would be a good site to hold a big race once a year. I am pretty sure that even though the owner says noise is not an issue, it will become an issue if many events are held there.
 
Blackout said:
Tim Kish said:
Blackout said:
I won't be holding any of Pete's NY series races next year at my pond. I still need more time to get quieter and get my ducks in a row. The town's sound ordinance is crazy low for agricultural land and no point in taking a test if I know I will fail..... But, 2015 is always a possibility. With that being said, I plan to hold a couple one-day races in 2014 that will run under a 82dbA rule. I held one this fall and it worked out pretty good.
Click to expand...
Maybe it's time the club started to seriously look into finding another site to hold a race at?D1 could use another race and like I said before you have a great group of people to help put it on.

Tim
Click to expand...
Awesome Craig, keep us posted.

I know of another pond. A club member talked to me about it this past weekend. I have not discussed it with the rest of the club yet. It would be a good site to hold a big race once a year. I am pretty sure that even though the owner says noise is not an issue, it will become an issue if many events are held there.
Click to expand...
 
I was watching RC boats race in the late 80's with muffle tuned pipes....Fast boats. Quiet has been possible for a long time.
 

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