Hello all
I thought that it would be interresting to get som ideas of how people are able to pass the sound-measurement (without cheating !) when using the newest and most powerful engines. This year I have been flying mostly with batteries, but I have played around a little bit with the OS FS-200S FI. Last year when I flew with the OS 140RX-FI and 18x10 prop I measured very close to the 94db limit. The OS 200FI spins the same prop at around 1000 RPMS more, no way that can pass the test. We did measure it with 17x12 over grass, and it was close to 94db' there (limit is 92 on grass). The YS160DZ powered Genesis of a friend of mine, spinning the same 18x10 was measured to more than 98db (that is more than twice the energy than the 94db limit)!

The question is really this ; How do you do it, here is a couple of alternatives :

1 : Cheating with less servo travel during noise test
2 : Never measured, and i do not bother
3 : Struggling by running a small diameter high pitch prop that makes the model hard to keep at slow nice speed.
4 : Three (or more) bladed prop of type X, size Y
5 : Are not using the short mufflers from Hatory, they are too noisy
6 : Another new and brilliant solution

I'm really looking forward to get som valuable inputs on this one !

Regards
Ola Fremming

What soft mount are you using? That could be an important factor. Check the new Hyde mounts in K-Factor.

Regards,

Vicente "Vince" Bortone

Vince
For sure we are using Hyde- mounts, My friend with the Genesis/YS160DZ has the recommended one from Hyde together with the YS nose-ring. On my Oxalys with OS200 i have made a Hyde-type of mount myself, this is softer and reduces vibration and noise a bit better, but with the disadvantage of slightly more engine-movement.

If your curious, take a look at home.online.no/~ofremmi

I think the question is : does anybody care to even measure ?

Probably you need to check different props to lower the top RPM. The 4 blade prop is the option. QQ was using one in his biplane at the USA-Nats and he passed the sound test. I know that is APC but don't know the size.

Good luck,

Vicente "Vince" Bortone

For certain especially the DZs will be all over the sound check if you let them howl.

As mentioned by Vince, I have been working with Merle on some new mounts specifically designed to address this issue. The first result was the AR80, a universal mount with a VERY smooth and quiet run. This mount alone is worth 3 decibels as tested. It also has the added benefit of reducing current drain close to that of an electric! This of course depends on a number of factors, including the method of mounting the pipe/muffler and the fit and security of the nose ring.

The down side to these very soft mounts is that if a YS kicks, it will move more. And if you have a narrow composite chin cowl, kiss it goodbye. This is a VERY real issue with some of the current designs so be aware that you need a lot of clearance. The engine doesn't hammer and shake on the low end as bad, and movement at idle is no worse than a much stiffer mount. The difference is in the kick back, and only in the kickback.

Since then we are testing a crapload of new mount configurations (we're having a lot of fun with this!) Currently I'm playing with an AR70, an AR75, and an MR85 (VERY light and soft!) I should have some real test data soon in direct comparisons with the AR80, standard ARA, and ARIA.

Some other things you can do to reduce noise:

-make sure nothing is rattling. Loose wires, worn wheels/axles, canopy fit, you name it. If it can move, it's making noise.
-Use a restrictor. This is the little velocity stack. it really smooths out the bottom end and is good for 1-2 decibels. it does reduce top end power though.
-try an exhaust diverter. Glen Watson (AMA Masters national champ) had one on his twister/YS set up, and it does some really cool things. I would guess it's good for around one decibel, but it also cleans up the exhaust trail especially in rolling manuevers. I was so impressed with it that I want one!
-try some foam around the engine inside of the chin/cowl area. Especially beside the head. This also helps cooling, and a cooler engine is more quiet. (Don't ask me about this one because I can't quote the math/formulas)
-PROPS

In the end your #1 noise maker is the prop. if you pay careful attention to all of the above, you can get away with a lot more prop and hence, available power. Once you get everything else taken care of, you should be able to run the APC 18.1x10 regular on the YS160, and the 18.1x10W on the 170 and make noise. If not, assuming your plane is around 10 lbs or less, yo ucan simply ATV the throttle back because you probably don't need all that top end anyway.

But if that doesn't work, the LAST option I would personally use is a multi bladed prop. The reason is simple, they have a different torque effect on the plane. This is most noticable over the top of a tall humpty where you've expended a lot of energy in rolls up and you're hard in the power and low on airspeed. It will make you have to trim and mix the plane differently. As a test, tri ma plane out with a 2 bladed prop and get used to it. now without touching anything else, change to a 3 or 4 bladed prop and fly it. I would bet money you have to use more mix....depending on the plane, sometimes a LOT more. But some planes are more sensitive to this than others, so you just have to try it yourself and see what works.

-Mike

Hi
I doubt it will be possible to make the 94 dB limit with a prop like the 18x10 on a YS 160. It sings out loud ! The good news is that we all, are going to be measured to the level of 94 dB OVER ALL SURFACES ( So it is, as I recall from the latest CIAM meeting ).

We have measured some of the YS 160's in my club and none makes the 92dB, but they make the 94 dB limit. That is, with 17X12 or 16½x13W or 16½x12w APC's. And the latters make the noise limit but they are, as Ola says, a little difficult to handle.

On another note :
But actually we are facing a silly old rule ...We are not going to go full speed very often, or very long anymore, with the power we have at hand .....so why not start measuring the noise according to revolutions on the motor ? Since we know it is not good to go full speed all the time as the pattern will suffer from this, the right thing would be to measure the noise from an aeroplane going exactly say 8000 rpm and then score it from 0 to 10. That would be something new...

MIKE !!
I have a deverter you can have.
shoot me a e-mail
I`m sure Ola is aware of most things discussed
he has been around for a long time and flys International events

Here is one thing I learned from Earl Haury

Expanded foam in the Spinner will get rid of the Bell Effect ring, it works

and the most important thing is, the Nose ring .

Experimenting with nose ring/limiters will give you different noises. and levels of noise
I might add if you have to adjust the Motor at all with the nose ring IE force it to fit the Fuse
from firewall missalighnments
you will have motor transfer noises at different rpms mostly mids and highs
more so with composite airplanes.
Apc has a 18+11 med. width blade that they made for a while But no longer distribute
I have a few of these the one inch pich more is a bunch quieter
we might be able to twist there arms alittle to redistribute them
I also have extended and modified many Apc Props with good results pitch , widths and extensions ,
just don`t strike the ground because the tips are more flagile than the rest of the prop
hope this helps
Bryan

Attached to the end of the stingers are Pics of exhaust diffuser Mike is referencing produced by Karl Mueller mounted on my Integral and Twister. Karl can be contacted @ [email protected].

Foam in spinner + Hyde mount with CH nose ring + APC 15X11 4 blade @ 8700rpms + CH intake filter in addition to no rattling airframe parts = 92 db measured on hard surface at this year's NATS

I agree with Bryan....the current trend to 10 inch pitch isn't doing us much of a favor in the noise department. The 18.1x10 is quite noisy on step even with a 140 RX up front. An 11" or even 12" pitch will help reduce noise substantially.

Ola, you may want to twist the 18.1x10 to a bit higher pitch. Dave Lockhart has written a straight forward detail regarding twisting the 3 blades, and as resourceful as you are you can do the same on the 2 blade, I am sure. Or contact Dave

Bryan, I'd love to get my hands on an 18x11. The 18.1x10 isn't nearly enough load for the Webra. I've extended one to 19x10 with better results but it's still noisy and clearance is more of an issue on my grass field. Haven't gotten around to twisting one yet but that's probably next.

On the nose ring misallignment concern...folks may want to try making a nose ring completely from rubber sheet. I use 3/16" polyurethane from McMaster Carr.

Matt Kebabjian

and I thought that i was under the limit!
so the long pipe's\mufflers for the YS is that mush quitere that can do the limit ?
I have tha same setup as Ola's freind exept for the the plane is wooden.

I have a question...
Has anyone used gas???
Like the ZDZ f3A 40cc engine??
this could be piped and have a good chance in passing db testing.
The weight is that of a 26cc gas engine..... or 2lbs 11 oz.
at 930G of the ys 170 that weighs 2lbs so it is 11 oz more.
If you used a CF pipe to boot, it would not take uch more weight...

Does anyone run a zdz f3a that you know of?

I do, and have started a separate thread about building a soft mount for the engine. It's around here somewhere. I have little experience with small gassies....I have much more experience with larger gassers.

I am also developing a technique that will add a nose ring to the engine, and not interfere with the spark sensor. When I start getting results with it, I will post on that thread

MattK

I did help a friend 2 years ago to put together the Abbra with the ZDZ 40 (non F3A). The plane was a little over 11 lbs. I am sure that could be below 11lbs by re-working some areas or just using the f3a version. Just replacing the 3 blade prop with wood prop will do it. We flew it first without soft mount and flutter in one aileron almost destroy the plane. After that we installed a soft mount and worked great. I think the noise level was comparable with the glow engines. We were using the gas carbon pipe. Check the attached pictures. Unfortunetely, my friend stop flying and sold the plane. I flew it few times and I feel that power was a little less that you get flying glow (Master Schedule). However, we didn't try different props and I think the 3 blade prop was too much load. I think the 26cc will work only for lower classes. It is a shame that we didn't have chance to fly it more.

Two more pictures of the Abbra with ZDZ 40.

Vicente "Vince" Bortone

APC has an 18.1-11 available as well as a new 18.1-12. I ran the 11 all last year and is very quiet along with some changes for the better in flight performance and feel compared to the 18.1-10. I am currently evaluating the 12 pitch. The engine has plenty of power to turn this prop also. I requested the blade be narrowed slightly so the engine would not load on the uplines since the pitch was increased. Only have 4 flights on the prop so more testing is needed before I can say for sure. Running a YS 170.

Bill Cunningham

Bill,

Do you get those props from APC directly, or does Central stock them?

Ryan,
I requested these props to be made so Fred sent them to me directly. Central might not even know about them so try APC, they sell direct also.

Bill

Ryan:

Central Hobbies has the 18.1x11, I received 2 a couple of weeks ago. They probably don't have the 12 pitch if Bill is still evaluating a prototype.

We were playing with Adrian Wong's DZ 170 in his ProLine last week - using a 17x12 we got it to measure 93db running on the rich side. Meaning that he only turned about 7900 rpm on the motor but still had more than enough power to fly through the P/F sequence. At one point we actually had him around 7500 rpm (91db) and he still had power to spare.

Derek

Was that the Akiba ProLine or the BVM?

Tim

Matt Kebabjian wrote
Ola, you may want to twist the 18.1x10 to a bit higher pitch. Dave Lockhart has written a straight forward detail regarding twisting the 3 blades, and as resourceful as you are you can do the same on the 2 blade, I am sure. Or contact Dave .

Can anyone give me a link to Dave's article?

I found this after a search here on Rc Universe.
Heatgun and steady pressure. I experimented on a junk prop for the first one. I took a piece of 1X4 and screwed it to the side of the bench leaving a 1/4inch slot. then I made a measuring device to measure the angle of the prop and measured a target prop . (16-11 in this case) then I put the prop into the slot and applied a twisting motion to the blade in the direction I wanted to go, (less pitch in this case 13.5 to 11) and then slowly applied the heatgun to both sides of the blade in question, once the blade Relaxed and moved I applied heat for a little while longer and then let it cool while holding it slightly past the target. when I released it it sprang back a little.

I then measured the blade in a predetermined spot (so all the blade would be the same, I drew some marks on the prop and the bench)
and saw if I was there yet. once I was satisfied I set the other two blades to the same pitch while also measuring the tip hight.

DISCLAIMER_____ I DO NOT RECOMMEND THIS PROCEDURE IF THERE ARE PROP S AVAILABLE IN THIS PITCH.
APC says NOT to do this. I know Dave Lockheart sells the repitched 3 blades. and alot of the folks in the pattern community do this.
Your mileage may very etc etc....

The key is to not overheat the blade while doing this. if you get a white spot on the prop too much heat. you want to apply slow even heat to the blade.

Regards Rod

It's the Akiba version, and I'm using a 17x12w. If the engine's set up correctly, 7,400 to 7,600 rpm is all you need. However, you need to know how to set up a throttle curve correctly to get a very linear power delivery.

That was the Akiba ProLine.

Rod,
If you are using dry heat to soften the nylon, make sure you hydrate the plastic after you are done. Stick it in a pan with warm water overnite. It also tends to stress relieve so the original twist should be just a bit more than the final you want.

You may also use a pan of boiling water to get the prop hot up and then use the heat gun to direct the higher heat exactly where you want it.

The best solution appears to have been found by Bill C....apc will probably start selling these props soon. The 18.1x12 looks real good for my Webra 160. The 18.1x10 is a bit noisy for my taste and when it was re-worked to a 19x10, it didn't really lose any noisy components. But sure has brakes!! The 12 pitch should have the best noise/brakes/speed envelope.

MattK

Ola, I've read a couple of engine reviews in German "Modell" magazine where they've used a plastic tube from the carb intake to the inside of the firewall so that the engine sucks air from inside the fuse. Remember the intake mufflers from the early 80's? Same thing only easier to make and supposedly quite effective.

How come this is such a problem now, YS 1.60s have been around for some time so how did people pass noise tests at previous EC's and WC's? Option 1 is the obvious answer but still...