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01-27-2007 07:53 PM  10 years agoPost 1
dogg5306

rrVeteran

Brussels, Belgium

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Hello guys,

What do you think about those "acoustic absorber sheets" from K&S... is it really useful

OK I do agree with the fact that the heli won't become silent after application on the inside of the canopy... but hey what's your feeling about that

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01-27-2007 10:21 PM  10 years agoPost 2
hlager

rrNovice

Sweden

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Hi! Why do you want to absorbe the fantastic sound of an Heli??

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01-27-2007 10:46 PM  10 years agoPost 3
dogg5306

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Brussels, Belgium

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I'm not against it
I'm just trying to keep the sound level which is allowed in my club to maximum 80dB... the lower, the better...

That's the reason why using OS50 engines at +2000rpm with a MP2 isn't advised here

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01-28-2007 02:14 PM  10 years agoPost 4
Futurac

rrKey Veteran

Belgium , Europe

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Noise

Only way to keep the noise lower then its now is to use Zimmermann mufflers.

No way Alu muffler will absorb noise to the needed level, its due the Material itself.

Most mufflers made for thick alu, i even seen 1.5mm wall thickness, and its still not enough.

external material will not do the work.it will suppress noise( if at all) by taking resources from others. Trust me, i already seen many nice Rubber add ons, and nothing was properly done.

In 3 major European countries the Model association requested most of known Muffler models for testing, and only Zimmermann passed the Noise level test.

All other mufflers failed in this test.

In EU, and recentrly in Japan they put a lot of attention to the noise level. Clubs shut down because of the noise and if you want to keep flying, Zimmermann is the answer.

Alex (Formerly Known as RCMarket )

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01-28-2007 02:42 PM  10 years agoPost 5
dogg5306

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Brussels, Belgium

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Just waiting for mine
I'll be able to compare its performance against MP5 and Hatori 938 mufflers very soon and not only on the sound level side...

That said provided that I'm below the limit... I can fly whatever I want and I'm already pretty sure that it will be the case... just looking for the little thing that is at the cutting edge...

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01-28-2007 05:23 PM  10 years agoPost 6
Jarno

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Finland

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Alex is very right about the muffler thing. By changing to a righ type of muffler you can actually reduce the noise level significantly.

But to be honest this noise damping material works too. It will not have much affect on reducing the exhaust sound, but it sure will dampen down the noise of the mechanics like main gear noise etc. I have done testing with this type of stuff as I'm a F3C pilot and we also do have the noise limit in this contest class. By adding some sound damping material inside the canopy I was able to get the noise level down with few decibels. By changing from the Mille II/Dyna-X ver2. canopy to a Dyna-X ver1. canopy I was able to bring the noise level even more down.

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01-28-2007 09:22 PM  10 years agoPost 7
Dr Lodge

rrElite Veteran

Guildford, Surrey - UK

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Vario do some very good noise dampening foam sheets, normally used on the inside of scale fuselages.

Vibe 90, Vibe 50, Vigor CS x2,
Dyna-x, Knight 503D, Logo 10,
TRex 500, Furion, Gaui EP200

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01-28-2007 09:43 PM  10 years agoPost 8
nivlek

rrProfessor

Norfolk England

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I've seen (in my LHS) some rubber sleaves that are designed to fit around your muffler . I believe that they are made by K&S , and are claimed to reduce noise , but I've never known anyone to use them .

At the end of the day , it gets dark .

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01-28-2007 09:46 PM  10 years agoPost 9
Futurac

rrKey Veteran

Belgium , Europe

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every think which is connected to the muffler and reducing noise, doing it by using power resources, e.g reducing power of the engine.
No magic over there, it is related

Alex (Formerly Known as RCMarket )

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01-28-2007 09:49 PM  10 years agoPost 10
nivlek

rrProfessor

Norfolk England

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No , the sleaves fit over the main section of the muffler , they don't interfere with any gas flow , so I can't see how they could reduce power , although they may stop the muffler form disipating some heat .

At the end of the day , it gets dark .

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01-29-2007 12:49 AM  10 years agoPost 11
Barney

rrKey Veteran

Inverness Scotland

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Dogg..If it's for your Dyna you have to be carefull with the fan shroud that its not rubbing/resonating anywhere.

If you can save a little with an good exhast , a little from sound deadning material, eliminate any resonance. That adds up to one big saving overall

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01-29-2007 01:09 AM  10 years agoPost 12
Qrrambero

rrKey Veteran

San Francisco / Bay Area

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Get an Electric Helicopter.
JOker
Ion
TRex 600
Raptor 620E
To name a few.

Ae

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01-29-2007 05:52 PM  10 years agoPost 13
Bruce Naylor

rrApprentice

Swindon, Wiltshire, UK

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I have invested in some PC case sound-proofing packs after I found out that the material appears to be fuel-tollerant - I put a sample in a jar of 30% cool power for a week, and it doesn't appear worse for wear. It's 8mm thick and quite light.

No idea how it will help noise-wise in a fuselage yet - but I'll post the results.

I've also invested in a FunTech exhaust - it seemed the quietest in the hover out in Spain at the Worlds 05, and from my limmited attendance at the Euro 06 in the UK. Again no data yet, but I'll pose results.

"If you know what you're doing, you're not learning much"

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01-30-2007 11:45 PM  10 years agoPost 14
dogg5306

rrVeteran

Brussels, Belgium

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Thank you for your input guys... It seems to work

I did apply the noise absorber sheet within one canopy and left the other one empty... then to test it here's the most reliable methodology...

Try to put your head into the canopy and YELL very loudly, do the same thing on the empty one... your hears will immediately point you to the one where the noise absorber sheet has been applied

Most reliable methodology... I should put a patent on it

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