Sound and props!!!!

[FlyguyXII]

I couldnt cheat even if i tried i can only pull 25% throttle before i break 98db. I think the muffler could get changed out for a slimline. The supersonic is loud but it has a radiusd port for increased exhaust flow. get a few extra rpm anyway. but I dont really have to do anything for the sound its just one individual who cant fly big airplanes and doesnt like gas engines that is complaining. Since i am 1 of only 3 gas guys at this field and the only one running a DA its hard to find somebody to borrow props from. The other 2 guys are running brison 3.2's Im taking it on my own accord to quiet it down so the 3 of us dont loose our flying privliges even thought the club pres says we are fine. I do like the sound of the prop ripping on some planes mine isnt that loud unlike some but i do need to do something for IMAC.

What is the best three blade mej for the 50? I primarily fly precision with the occasional 3D. Ill keep the nx for the 3d stuff and use a 3 blade for the prescion part of it

[Dangerous Dan]

	Quote: Originally Posted by FlyguyXII
	I couldnt cheat even if i tried i can only pull 25% throttle before i break 98db.

I would request a second DB meter. You would have to do everything wrong to be that loud on a DA 50

[Bunky F. Knuckle]

Try a Mejzlik 23x8 or 23x10. That should get you quieter.

Going from a regular muffler to a canister set up, you are looking to gain in the area of 12 to 16 oz!! You could try a tuned pipe set up, but will require more $$$. But the power gains will highly offset the weight penalty.

[FlyguyXII]

Cant put a can or turned setup in the aircraft. would like to but would require major redesign

[FLYNYAK]

I hope I dont get in trouble for this post . But I have a Mejzlik 22x10 and a Biela 23x8 on e-bay $30 each . Thay will help your sound problem.

[Mithrandir]

Rotax puts a muffler on the Carb of their 2 strokes

[FlyguyXII]

just ordered a 20x10 mej 3blade ill try this and see what it does

[FlyguyXII]

ill post back with the results of the sound test

[GremlinX]

	Quote: Originally Posted by Mithrandir
	Rotax puts a muffler on the Carb of their 2 strokes

And I have a few prototypes for some of our engines... intake mufflers that is...

[crhammond]

Rob,

I'm with Russ... at least here in Western Canada noise costs us fields even in the middle of nowhere.

My (now sold) DA50 in H9 260 was set up with a Slimline muffler and a 20x12 3-blade Mejzlik. You had to manage the throttle as it is a very fast flyin prop. The performance was not quite like a 23x8 Mej - but it was good once I adjusted my flying style to it. Even in that configuration it would be iffy to pass an IMAC sound test. It was not loud int he air - bu ont he ground it sure was. 103db is REALLY loud.

Al at JTec has made me some great wrap around pitts mufflers that really work. They are 2.5" cans with long stacks. They are not canisters but they work well. He also make snufflers that would work but are heavy. Even a ZDZ80 can pass the sound test with Al's big mufflers - you lose less power too.

Best idea would be to modify the fuse to take a canister.

Since I moved to canisters I won't fly anything without them. The noise is cool until you lose your field. Yes I am a noise cop at our field... but only because I had the loudest planes and ended up spending lots of time testing. The last time we had to find a new field it was not a fun experience.

Quite a few fields up here have a 92db @ 25ft rule... you can make it with cans and a 3-blade on almost any sized engine.

[AHP]

I ran an MSC 23x8 on my DA 50 with a Slimline Pitts and it was VERY quiet. The NX props are very loud in my experience. I flew an NX 22x8 for a short while and it when it would rip it screamed! The 23x8 isn't as bad, but still loud. The PT 23x8 is another very quiet prop.

[zippy]

Hello, I'm the guy that hillmanr2 is talking about with the exhaust stacks. I got the idea from a friend of mine that owns an RV7 with straight pipes and these tips.

Mine are made of 1" aluminum tubing from Home Depot, and fit nicely on the 3/4" down tubes of my Slimline pitts muffler secured with hose clamps. The pinched ends are not closed but rather form about a 1/8-3/16" slot at the bottom. These took all the high pitch bark out of the exhasut note, and will not reduce exhaust flow.

They are a Wick's aircraft supply product:




EXHAUST MUFFLER TUBE 1-3/4''

Mounting these "piccolo" tubes on the ends of the aircraft exhaust pipes will substantially lower exhaust noise. Tests on an RV-6 showed a 3 db drop in noise power, or 3 times less than previously measured. Each can be quickly and easily installed by slipping them over the end of standard 1-3/4" exhaust pipes and tightening down the attached screw clamp. Made of stainless steel. Installed length 6". Weight 6-3/4 oz. Sold individually.