160 DZ noise

[Troy A. Newman]

Tom,

What I do is limit servo travel to a certain RPM. If you are turning a 16.5" 
prop over about 8300 it will be too loud. The 17" props the limit is about 
8000-8100.

So what I do is get to the contest location, and start the motor up with a 
tach in hand. I then dial the motor back to the needed RPM. I try to fly on 
this RPM all the time. The result is I always have about the same power 
regardless of elevation or air density. This doesn't always work perfectly 
but it will make the noise limit and has plenty of power for performance at 
the top.

This is not a cheater switch or dual rate on the throttle. It is just a 
throttle barrel that is can't open 100%.  The real noise comes in the last 
little bit of throttle as the motor starts to bark. If you take this hollow 
growl out the result is the power is almost the same and the model is much 
quieter.

I learned this little trick from one of your local boys, Peter Goldsmith. 
Basically you just need to go out with a noise meter and play with some 
props at different RPMS. I make the change in prop and dial in what RPMS 
will make noise and go fly it and see what the results are.

I find that the 17-12W and 17-12 can turn up around 8000-8100 and it meets 
noise, and the power is as good and in some cases better than anything out 
there. If you are not on the noise meter then you can just run it at 100% 
ATV and have more pull than any other setup even the Flower powered models.

Another prop that really reduces noise but absorbs horsepower is the 15.5-12 
4B....This prop is very very quiet at 8600 as the tip speeds are down. The 
problem is on really windy conditions I feel its not quite the best setup 
for wind. But in dead calm and thick air its pretty cool and a good Flower 
power equivalent as far as speed control and sound both on the meter and in 
the air.

Troy
----- Original Message ----- 
From: "Koenig, Tom" <Tom.Koenig at actewagl.com.au>
To: "Discussion" <discussion at nsrca.org>
Sent: Monday, October 03, 2005 5:17 PM
Subject: 160 DZ noise



Gents,

Just shooting for prop combinations.

On the weekend we were doing some ( disturbing) noise tests. We are also 
about to run our annual comp and team trials for CAOCC and our Bi-annual 
Trans Tasman punch up with the new Zealander's, where we will be noise 
testing. so I thought I'd better be prepared.

Anyway- my 160 DZ, Hattori 698, CD header on 29 % Nitro Coolpower 'blue' 
oil, Hyde style soft mount, APC 16.5 x 12 W and Synergy airframe produced 99 
DB at 3 meters @ 8600 rpm!!!!!!!!

This thing is making a RACKETT!!!!!

Next day I went down to 25% Nitro and 15.5 x 12.5 W and reduced this to 95 
DB.

Now I am not running that different a set-up to most people, but it confirms 
my suspicion that most of those that I compete against are WAY over the 
noise limit.

Since I have heaps of power I am about to try a 20% nitro mix and see if I 
can get the thing to shut some more. I am also considering trying a 15.5 
four blade.

Those of you who HAVE noise tested your set ups.....what are you using 
successfully???

Thanks for any recommendations.

Tom

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