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Quietening a Saito 180 in a Capiche 140

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Capiche 140

Peter Jenkins07/05/2011 21:02:13
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Has anyone got a Capiche 140 (the Weston ARTF one) with a Saito 180 installed? Mine registered 89 db during the noise test today and I wanted to know what others had done to make the 82 db. I'm using an 18 x 6 Graupnic G-Sonic prop which the Saito is turning at just over 10,000 revs.
 
As I see it, I could go up in diameter or pitch or both. Before I start experimenting (spending money!) I thought I'd gather any experiences that there are out there.
Martin Harris07/05/2011 21:54:21
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I'd try going up on pitch which will drop the rpm, hence prop tip speed which will reduce both prop and exhaust noise.
 
A twin chamber silencer might help - possibly something Just Engines may be able to provide - or you or a clubmate might be able to modify yours.
 
To get an ASP 180 through our noise test I made a larger volume twin chamber silencer (didn't try with the standard one so can't confirm how much difference it made but I needed a twin chamber one for a 120 I replaced in the model with the 180) and used an 18 x 10 G-Sonic prop. A silicon deflector can also make quite a difference.

Edited By Martin Harris on 07/05/2011 22:21:24

Peter Jenkins08/05/2011 01:04:58
1640 forum posts
305 photos
Thanks Martin. I hadn't thought of doubling up on the Saito silencer front - might be an option. However, the Capiche also has a pipe tunnel so that might also be an option but I suspect that the biggest culprit is the prop and I might try an 18 x 10 or 19 x 10.
Djay09/05/2011 10:07:08
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445 photos
My saito runs a 18x10 prop in my TF Mentor, and is very quite with tremendous pulling power. I use Byron 20/20 YS mix fuel, these engines like high nitro.
Starts with the smallest of tap on the prop as well after priming, a lovely engine.
 
Darryl
Peter Jenkins09/05/2011 21:28:45
1640 forum posts
305 photos
Darryl, thanks for the info. Dave Wilshere of Motors & Rotors has suggested an 18 x 8 but I've found a Xoar 18x 10 in my collection. Dave thinks that might be too much load but yours seems to be OK so I'll continue with that plan. I've also bought a Just Engines super quiet silencer specially made for the Saito 180 but as they are out of stock at present it might be a couple of weeks before it arrives. As for ease of starting, I agree with you - this Saito is one of the easiest starting engines I've ever had.
 
Martin, I tried a silicone tube on the end of the Saito silencer and retained it with two tywraps done up really tights. When I got the Capiche down the silicone pipe was missing! As I stated above, I'll now wait for the new JEN silencer and use an 18 x 10 prop. Let you know how I get on.
 
 
Peter Jenkins13/05/2011 21:12:16
1640 forum posts
305 photos
Well, in the end, I bought a G-Sonic 18x8 and an 18x10. Fitted the 18x10 on for the noise test and that failed with 84db with the mike facing the prop. I shall wait for the Just Engines silencer, which Weston tell me they make for JE!
Martin Harris13/05/2011 22:18:44
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It's worth making sure you aren't near any noise reflectors (buildings, hedges and even bystanders can make a big difference. Make sure that the tester holds the noise meter well away from his body. Also, hard dry ground gives an increase so it's as well to test over reasonably lush grass and dampish ground. I'm told that humidity has a very big effect, according to a paper that a clubmate gave me recently, and it's best to test between 10 and 40 percent RH although I'm not convinced that it makes all that much difference at 7 Metres.
 
Another thing that adds unneccessary noise can be loose wheels (or other items) vibrating.
 
Also, some silencers (Lasers particularly) can direct the exhaust into the propwash causing noise from the interaction - a piece of tubing to direct the flow in the same direction as the propwash can work miracles.
 
I use thin copper wire to hold silicon extensions on to typical 4 stroke silencers - or turn a groove into the stub for the cable tie to grip.
colin watson13/05/2011 22:27:08
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try wrapping the silencer in rescue tape or the silicon sealant and glass cloth i have used the rescue tape to great success on both nitro and petrol engines along with prop change try even using silicon sealant along inside of the cowling. we have a 80db noise restriction so these methods work and the rescue tape is a cheap £3 fix i lost 6db alone by using it.
Martin Harris13/05/2011 22:35:06
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Colin - 2 stroke, 4 stroke or petrol?
 
4 stroke exhausts get pretty hot - I'd be interested to know how it stands up to the temperature...
colin watson13/05/2011 22:44:29
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2 strokes and petrol even run my petrol in with it no problem and if you are worried coat it in red silicon sealant and wrap with glass cloth. only thing is it retains heat in the exhaust a little longer after being run. so let it cool between flights

Edited By colin watson on 13/05/2011 22:45:56

Peter Jenkins13/05/2011 23:06:02
1640 forum posts
305 photos
Martin
 
The test was conducted on our flying field with cars parked approx 50 ft away - could have had a bearing I suppose. The field is pretty open so other than the cars there are no other reflective surfaces. The ground is grass but it is rock hard at the moment - RH - not sure what it was but it was threatening rain so probably quite high. I did have a silicone tube tywrapped to the silencer but it blew off when the aircraft was in flight - I did not have a groove machined in the silencer but that sounds a good fix. I will look closely at any other airframe generated noise before the next test.
 
Colin - thanks for your suggestion of using Rescue Tape. When I searched Google I could only find a US supplier who wanted a huge amount for shipping. However, this evening I found a whole lot of UK suppliers so I will try and get hold of some and use it on all my silencers. Putting silicone sealant onto the cowl inside is an interesting thought. How thick does it have be spread and how clean does the cowl have to be?
 
Peter Jenkins22/05/2011 01:26:05
1640 forum posts
305 photos
Martin and Colin - I fitted a Weston pipe made for the Saito 180 and we noise tested with just the pipe. Also leaned out the engine so that it was just a little bit rich - which pushed up the rpm significantly on an 18x8 prop. Highest recording was 92 db so a fail. Then wrapped the large cylindrical silencer in rescue tape and restarted the engine. After warming up the engine we noticed that the rescue tape had split and peeled off! Guess the 4 stroke exhaust temp was too high! Shame as it would have been good to get a second noise reading to gauge the effectiveness of rescue tape.
 
I am now going down the route of smaller diameter larger pitch props and I'll let you know how I get on.
Lee Smalley22/05/2011 11:32:35
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2125 forum posts
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2 articles
18x 8 does seem a tad small, i have a moki 180 running an 18x8 on a running in period and it will go to an 18x10 when ran in, surly 4st should be higher!!
Peter Jenkins22/05/2011 23:01:46
1640 forum posts
305 photos
Lee, you are right. Saito recommend a 14x13.5, 14x14 and 15x12 for aerobatics so I am going to try them and see if that helps. An 18x10 does seem to overload the engine although it is only just run in so things might improve with a bit more use.

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