airborne2.4

It's really quiet

I stumbled upon this http://www.youtube.com/watch?feature...&v=5aHn7uMxCnM

MTK

I have one of them too on U Tube

http://www.youtube.com/watch?v=iAd8d...ature=youtu.be

In addition to the pipe andnoise suppressing APC 20x10.5 prop, the engine is rubber iso mounted. The combination of prop, pipe and soft mount produces an very low noise footprint. BTW, I tried a 3 bladed prop, a Mejzlik 18x10 carbon, and it was not any quieter. It needs a higher pitch than 10".....I wish APC or Mezjlik made an 18x12 3 blader for this engine

I am just about a week away from the maiden on my new Pattern design, Delta, which has a DLE55 in it. It is also piped and rubber iso mounted and turns a Mezjlik 20x12 3 blader. The extra pitch really tones things down a lot. This combination was wrung out in an Extra a couple years ago and it truly is electric like quiet. We'll be making a video of this combo at some point

airborne2.4

That's really quiet MTK. Nice maneuvers in the air too.

MTK

Thank you!! Gas engines do not have to sound likechain sawsto be effective

Hone1er

I got to tach my engine today and i was getting 7250RPM with the Vess 20B.

airborne2.4

Lol

BarracudaHockey

My Feedback: (11)

Plane Bender pipes/cannisters = Pro Flow

www.planebenderproducts.com

Hone1er

Just curious if anyone has any numbers on the stock muffler with a Vess 20B? Or any other 20'' prop on the stock muffler? I just want it as a reference for what i'm getting now on the pipe.

coronabob

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Notes on mine show:



OS GT33: Xoar 20x8 6500 on 3rd flight, Falcon 20x8 6850 on 4th flt, Falcon 19x10 6600 about 10th flt

DLE30: Falcon 19x10 6300 well broken in. This was the same prop that I pulled off the OS.



Both engines were running their factory mufflers.

MTK

I'm running APC props. Same diameter, 10.5" pitch, piped,7400 on aviation gas and 7800 on premium auto gas. I don't run mufflers only pipes.

I don't believe the pipe is increasing rpm that much (1000+ is way too much of a difference). So it has to be the prop efficiency. APC props use slightly narrower but much thinner blades thanany of the wood props. Have you guys considered modifying the woodies a bit to get the engine to unload more? Running the engine at 6400-6600 is possibly very close to it's lower limit of the powerband

coronabob

My Feedback: (10)

Hi Matt,

I am getting APC 19x10.5 for a good reason - $10 discount off $50 order from Tower. I agree with you since my OS never quite unloads. As you can see, the Falcon unloads it 350 rpm more than the Xoar.

From the way it sounds I know there's more to be gained. Just did not know how and besides I am not a big fan of APC props just because it's not wood, which in my opinion is safer.

MTK

Hi Bob,

The piped engine was broken in on 19x11 APC pattern prop.

Don't be alarmed about the APC's....these guys have been at it for 25 years and know what they are doing. There was a lot of FEA analysis early on as much for the strength aspect as thrust generation and noise abatement. After a few flights you will know what I'm talking about

The current props in this size were developed for the YS175 4 stroke engine. The OS on muffler is not quite as powerfull as the YS.

The biggest thing to worry about is the razor sharp TE. I use a thick walled piece of silicone 1" in diameter to turn them.

dobro

My Feedback: (3)

Hi again MTK, You were right about my first attempt to soft mount the GT 33. This is my home made soft mount that a good friend taught me how to make. I've had several flights on it and it works great. Right now I had to go to the stock muffler because my coupler set up will not take the heat. I saw in a post you have a coupler that you make. I'm very interested in one. Could you give me the info in a pm if you like? I think I will have to get another tuned pipe also due to the fact that my CF pipe now was for a glow engine. You can definitely tell the difference in power when flying with the stock muffler and tuned pipe. Will the hotter heat break down the lamination in a glow CF Pipe over time ? This GT 33 makes my Black Magic really scoot. Plenty of power. Thanks Matt.

MTK

Heeeyyyy great stuff!!

Yes I have some of the coupler on hand. I'll Pm you with the price and you can give me your address. I've had mine in service for going on 300 flights and still like new....

On the carbon pipe, it depends on how old it is and whose pipe it is. If it's an ES Composites pipe, chances are very good it was made using high temp epoxy so it will take the heat fine. But if itis a Bolly or somebody else's, I can't be sure what epoxy was used. You may want to try it and see.

Don't worry too much about a glow vs gas pipe. Yes, the glow version has the reflector baffle at around 14" in from the stem where the gas has it around 17", but the reflector is identical. If the pipe is glow, just add a length of extra tube. You will need a length to go with the Hatori header anyway so just make it long enough. You want a length of around 26 1/2"-27" from the exhaust flange to the reflector, following around the header. An old aluminum wing tube is the perfect size; I've also used a piece from an old broom handle which also works fine.

dobro

My Feedback: (3)

Great info MTK. Thank you. Talk with you soon

Hone1er

Just to update you guys....my OS 33GT died on me in the air. When i tried starting it again i had lost most compression.

DHFlyer

I bought a 71 inch slick with this motor on it. What do you use for a spacer for xoar and vess props with a 10mm hole to make them fit the 5/16 shaft? I looked through the thread and tried a search but couldn't find this info.
Thanks

choihjin

My Feedback: (1)

Hi!
I have almost same experience on my third OS GT 33 recently. My engine was also about 2 month old, but it was perfectly tuned.
It was good condition on a Extra 330 until Saturday, but during the 1st flight in Sunday I felt it was losing power, landed and checked, it seems lean running with hot. After several starting and running engine, it lost compression.
I found sands on the filter in carburetor, which might block flow of fuel, caused not enough fuel fed into cylinder. I believe the sands got through rear carburetor, which is relatively close to back fire wall of the plane. I was running the engine on dry soil field.
Were noticed some scratches on the piston and loosened ring and also some scratches on crank shaft around front bearing. Now the engine is running fine with new ring and piston. The parts were ordered from rcjapan.net.

Hone1er

You can get some spacers from Craig at Customstandoffs.com

2 for $10

BarracudaHockey

My Feedback: (11)

www.mcmastercarr.com

Hone1er

I fly mine off of a hard surface which is why i am really surprised that this was my issue. I would just like to have my engine back at this point. It was running perfect prior to this incident.

Anyone put a filter on the rear carb to prevent this from happening? Maybe something like they run on RC cars.I can't afford to be replacing parts every few months.

DHFlyer

Thanks for the info Hone1er and Barracuda, appreciate it

Hone1er

When i get my engine back at the end of this month or beginning of next month should i just bolt it back on and hope i don't get any debris in it again or is there something i can do to prevent it?

flyva

If room permits, you could add a velocity stack and then stretch panty hose over the velocity stack and secure with the proper size O ring. Caution...some velocity stacks have razor sharp edges and vibration would cut through the panty hose in time. Depending on the hose it may take more than a single layer to give you a good filter.

Hone1er

Thanks. I might try that if i ever get my engine back!