RCGF 26cc to 80 dB

[Reno Racer]

Dear all,

 

My RC model petrol engine experience is fairly limited, I've owned an Sv17cc (which was way underpowered for the weight) and an excellent RCGF 15cc. I have rebuilt and tuned classic car (full size) engines; my limitations comes with trying to reduce noise of RC aeroplane engines to meet legislation.

 

Flying here in the US, its not really an issue (certainly in rural Oklahoma), however, looks like i'm posted to Germany next, so need to ensure i'm at the 80 dB level.

 

Firstly, the engine I'm taking about is a RCGF 26cc (rear carb) petrol. Currently has the standard dustbin type exhaust. Engine is fitted to a 1/4 scale Nieuport 11 from Balsa USA, so that might limit the use of more exotic cannister exhausts?

 

I'm not sure what the current dB is of this engine, not yet got a sound meter. Does anyone else have this engine and know what the sound output is??

 

If it is over 80 dB, what options do I realistically have. I'm aware of sound deadening measures for engine mounting, and props - although a WW1 warbird won't look right with a carbon prop - I want to try and stay with my 18x6 or 18x8 wood Xoar WW1 style props, if I can.

 

I don't have enough spare dosh to start throwing it around of 'gucci' exhausts, if they don't get me to the 80 dB level.

 

Finally, before someone post, I cannot bring myself to convert it to electric - sacreligious in a WW1 Figher (although I do have the little 900mm span electrifly Nieuport 11)

 

Suggestions, pleaaaaaase

Edited By Christian Ackroyd on 11/02/2012 14:29:27

Edited By Christian Ackroyd on 11/02/2012 14:29:57

Edited By Christian Ackroyd on 11/02/2012 14:31:03

[Spice Cat]

Good luck with the posting to Germany. I do miss my occasional visits to the Fatherland.

As for toning down, there have been a number of very good articles on the subject and if you e mail Mr Winch with a specific enquiry, he will always reply.

 

Rgeards.

 

[Alan Cantwell]

manifold into the fuzz, and fit a canister, they are not just for high performance aircraft, rather that fit a high pitch prop, try a lagre diameter one, with a pitch n more than a 6,

 

or take advantage of the lerge cowl, and make 2 silencers, exhaust one into the other,

[Turbycat]

I had a crrc 26 cc petrol. I managed to get that fairly quiet with a 17 x 10 prop. I had that on a Nieuport 28. Performance wasn't great. Just about flyable. I've recently re-engined it with an Evolution 26 GT witha BCM inverted muffler and an 18 x 6 prop. It makes a little more noise than the crrc but not much. I haven't got figure for it but the club chairman is happy!

[Reno Racer]

Well I'm going to give this a try before looking to more expensive cannisters.

 

DLE30 fits RCGF 26cc Exhaust.

[Engine Doctor]

Hello Chris . a real solution to the noise is to fit a Krushnied ( i think thats how its spelt) exhaust . I have one fitted on a Moki (McKay) 30cc. the engine is mounted sidewinder and the silencer exhausts from below . It really does lower the noise , is well made and I think its made in germany so you may be able to pick one up while your over there. Failing that Stuart McKay sells them . Cost is about £79/80 ish ,but they do work and fit in cowl. other silencing tip is to prop it so as to load it up a bit . Also having the Carb inside a cowl helps a lot or fit an air filter as the carb noise can almost equal the exhaust.

[Martin Harris - Moderator]

Where in Germany? The club at Porz (near Cologne) which ours has a connection with ours allows mightily noisy beasts...

 

Might not seem overly impressive until you notice the distance the noise is measured at...

 

(check out the "Flight times of measurement" noise link under Operations)

Edited By Martin Harris on 15/02/2012 15:34:29

[Reno Racer]

Martin,

 

Good to know. I'll try and check with the clubs in the area i'll be in - Bad Fallingbostel, lower saxony.

 

Everyone else. Thanks V Much. Some useful nuggets. I have 6 months to 'fiddle', before getting to Germany, so will start off with the minimal expense options first before spending on a expensive cannister.

 

My Carb will be inside the airframe, though a hole in the firewall (engine is 6" long to prop mount and cowl requirements is 5", so i'll be using shorter stand off mounts and placing the carb inside, which might readuce some of the noise. Its a rear carb engine.

 

I've also covered the exhaust with that rescue tape that appeared in an RCME article about a year ago, this i believe should 'insulate' against the tinny sound without affecting the exhaust temperature. I'll also fit this TBM silencer thing with the silicone tube.

 

I can also use the largest Dia prop (and relatively small pitch), since its a WW1 fighter.

 

I should be able to test all of the above in a week and measure the results. Hopefully, it will be promising. My only worry is that the Nieuport is, of course, an open structure built airframe (almost like a flying drum!!), so hopefully that doesn't resonate too much.