I’ve never been a big fan of the Kaos design because of its thick airfoil, preferring the thinner wing Kwik Fli taper wing, but years ago when Tower was still selling their Kaos in kit form I bought one and stored it away for a future build. In May of 2004 I completed the build and used an OS 46 for power. The fuselage was narrowed as much as possible and the nose section molded into the spinner to improve the aerodynamics. Although I used the wood provided in the kit the flying weight came out to 5lb 3oz.

To be continued…..

The OS ran really strong but it didn’t pull the Kaos around at super ballistic speed like I prefer. Within a month of flying I pulled out the OS and replaced it with a more powerful Irvine 53 ABC. It really came alive with the 53 and has been much fun to fly. Here is a You Tube clip http://www.youtube.com/watch?v=9Zkt6pXu0rk&feature=plcp with Irvine 53 power. At that point I reconsidered what I thought about the Kaos 40 and found another kit for backup on the auction site.

To be continued…..

After all these years of flying the Irvine started fading and rather than replacing it with one of my NIB 53 backups I decided to give the OS 55ax a try.

Out with the old 53!

To be continued…..

Installing the 55.

To be continued…..

I removed the internal muffler baffle and drilled out the exit pipe on the muffler as large as possible without making the pipe wall too thin.

To be continued…..

Ready to go! Flight report next.

To be continued…..

I have a tower kaos arf with OS55 AX APC 10 / 8 and Mac's tuned pipe its a real missile , you'll not be dissapointed with this engine.

You've gotta be real careful with that. If you wind up with the hole in your exhaust tip plus the size hole you now have in the 'baffle' and you compute the total area, vs. the total area of your exhaust port and they are larger than the exhaust port ( the actual engines exhaust port) you will have screwed up the reflective 'wave' that keeps too much of the the incoming fuel/air charge from spewing out the exhaust oon the way up to the combustion chamber. You will have an engine that has a lousy low end and mid-range transition, with a too touchy needle, the top end always wanting to go lean...not good..
A tach reading with a completely stock OS muffler and the modiified one will surprise you, seriously.
The tuned pipe, or a Jett type pipe arer a much better idea.The idea behind the tuned pipe like alcarafa is running is not about 'decreasing backpressure" or "opening 'er up". It's about optimizing that reflective wave.His motor rips, your's will be a diog ,and I'm not dogging you .
I'd think over this one a little. Doug

Doug,

Thanks for the input and your thoughts on the muffler. There is some debate on the net about modifying the muffler (both positive and negative) so we will see. The exit pipe size enlargement is pretty limited by the recessed ring that is around the outside tip so the size cannot be increased very much.

one of my tricks for good muffler performance is it to use the sf 46 muffler on the newer os engines its well optimized for max power, and is no too loud. has excellent throttle transition and mid throttle performance as well. i do prefer using a jett or nelson type for the simplest high output, the tower 46 muffler is loud and has very poor fuel consumption, it over scavenges badly.

Thanks, it looks like the mufflers for my OS 50SXs and OS 46FXs are the same as the OS 46SF.

8178,

Did you ever get the Kaos back in the air with the .55?

Yes and still flying it. The 55 pulls it very well. Converted the radio system from a Futaba 12FG to a FrSky Horus X12S telemetry system.

Mike

If you were going to do it again would you drill out the exit pipe on the muffler? I have a Tower Kaos (ARF) with a OS-55 on it too but with the stock muffler. Just curious what the advantages are?

I never ran the stock muffler so I have noting for comparison.

Mike