A few weeks ago, I made a post to ask how I could get a little more umph behind my RTF Avistar w/ O.S. 40LA engine, aside from replacing the engine.

I followed suggestion, and removed the baffle from the muffler, and threw on an 11x5 prop instead of the 10x6 that came with it.

I was able to give it a test-flight yesterday, and wow was I impressed! First off, we did a tach on it, and had it running at 13,000 rpm. The 11x5 prop really gave me alot of power in the climbs... about double what I was used to. I was able to fly the thing straight up, and was actually doing newbie hovers (very shaky, and way the heck up there).

Only downside that I see, is that it's a bit faster than I've grown accustomed to... but it sure made it more fun and exciting. I used to fly at full throttle to overcome wind, and to add excitement to the flying experience. Yesterday I was flying at 1/2-3/4 throttle and still moving very quickly.

Is there any downside to removing the baffling? Noise isn't really a concern, as it wasn't too much louder than normal, and still quieter than most planes that fly out there.

Nope, no downside to removing the baffle other than the noise increase.

In theory, the drop in backpressure might reduce the pressure to the tank, but that's going to be minor, and shouldn't affect the engine running at all. Removing the baffle from OS mufflers is a common mod. Many engine makes don't have baffles in the muffler at all.

I have had an RTF Avistar for about a year now. It's my first RC plane and I had progressed to the point where I was really wanting more power, especially for vertical. So, even though I had a TT 46 available I decided to try a mousse can muffler on a Mac's header. I had read raves about this setup in the Fun Fly forum and I like to tweek things in general so I built one according to the info found on the FF forum. The result blew me away! Much, much more power all around and a very different beast to fly. One good reason to go with the LA is that it is quite a bit lighter than the TT46 or OS 46fx and the Avistar seems to need a lot of tail weight to balance out.

Here's my setup:

1. Mac's header (the one made for a OS 40 FSR). The shape of the exhaust port in the header has to be opened up with a Dremel and metal file to match the shape of the exhaust port on the engine but the bolt pattern is a perfect match. Cut the header length to 3.5" according to the instructions on the Mac's website. This is longer than the length rcommended for the 40fx but the LA is a lower rpm engine (that's my logic). Use the piece you cut off to make the inlet pipe on the mousse can muffler. I also had to stick the header in a vise and bend the pipe down and out a little to clear the wing. I stuck a deep 7/16" socket inside the pipe during this bending to keep from kinking it.

2. APC 10X5 prop although I think a 11X5 is definitely worth trying.

3. 15% nitro fuel

Good luck,

Big Mike

I have an avistar w/ a .40la and i also have a macs pipe for it but should i put it on? I have only had about 10 flights, but i am very good. Would the mac pipe help w/ speed at all.
I am not good at slowing down for landing, would the 11x5 make it slow down more?

Why are you guys putting header pipes on motors that are stuck in trainers?? If your to the point of putting on a header pipe to get more speed then its time to upgrade to a better airplane.

Yeap, Speed can be addictive. Just remember you are flying a trainer, not designed for a lot of speed. I suggest you guys reinforce the wings before they clap in the air.

I put fiberglass tape on mine and i couldnt snap it if i tried, i suggest and glass your wing even if your not planning on going fast, its only a couple of bux and sum epoxy.

NMTR13

Don't trust the Avistar. My wings were glassed and straightened out. I had an TT 46 on it. Doing spins coming down, which i had done previously, and my wing snapped on the left side, not where it was glassed. One second I see this square piece of wood(left wing) just floating in the sky and this spinning rocket at about 150 mph coming down near the runway, the scare of a lifetime. I would suggest u get an aerobatic before trying lots of stuff with trainers. The avistar is supposed tobe an aerobatic trainer, but its not that great for stunts. So just my 2 cents if u wanna keep ur plane up, and everyone at the field safe.

~Victor~