Classic Tutorial...hidden exhaust system!!

An often over-looked, area of a precision aerobatic model is sound control or muffler system. Most spend enormous amounts of time and money on selecting the engine. What about the parts that direct the exhaust? How many flights can you fly without maintenance? Is your engine/motor system quiet or hidden? If not read on!

Exhaust systems for engines- Many of todays engines offer some combination of unique subject, value or time from box to model. The top brands have a wide selction of after market components. The following is how I UPGRADE the YS exhaust system. Please understand that these ideas are mine, have worked for me and can be consistently executed with my skills, tools and time availability...they may NOT work for you!

Subject: Great Planes Zlin 526

The Great Planes Zlin was designed by Great Planes R&D airplane designer Mark Hampe and builder/writer Steve Beros with George Rodriguez as the product manager. This same team developed the "Sequence", which I have flown extensively, written about on a RCU thread in the electric pattern section and just think is incredible!

Integrating a modern 4-cycle into an ARF or (?)- The neat thing about 4-strokes other than the torque, the large props, the low idle speed, reliability...they typically require a small muffler system. YS produces a very powerful motor called the YS-63. It is an excellent direct replacement for a .45 - .50 2 cycle. Hatori of Japan produces a gorgeous header and muffler that makes the whole combination virtually "silent" in the air. When I am at my local flying field with at least one other glow model...I cannot hear the set-up discussed here.

The Zlin challenge- The sleek nose of the Zlin 526 just doesn't need a stubby 4-stroke muffler sticking out...how about a completely enclosed header/can muffler?

Solution- The Zlin has enough room for the entire muffler "can" to be inside the cowl but the stinger or exhaust would need to go through the wing. Strength is not an issue due to the aluminum wing tube. I could put a hole in the leading edge of the wing...but then there is the silly knob hanging down.

I decided to rotate the muffler 90 degrees and by using a Hobbico silicone exhaust deflector the exhaust exits on the scale side of the model, is almost hidden, adds no meaningful degradation of performance and here is how I did it.

Photo series- Photos basically speak for themselves. Central Hobbies sells the header and can muffler...about $110+ for the combo and includes the shock absorbing mount. The mounts sit on 1/8: plywood plates CA'd to the engine frame work. All of the joints were re-CA'd (one should do this for EVERY ARF you want to keep) and Zap epoxy finishing resin coated every where.

The red stuff is high temperature silicone added in the gap between fuselage former and can. The exhaust deflector was attached with the same silicone and a couple of tie-wraps. A little 1/16" scrap balsa dam was added as an emergency barrier if the exhaust deflector fails, falls off or ? The hole in the fuselage lined up perfectly with a lightening hole in the plywood doubler.

The last photo shows the large exit on the bottom of the cowl. Remember you need a 2 to 3 times larger exit hole than entry hole for proper air flow.

This set-up can work with any number of models with a little imagination!

The landing gear has received a number of (PM)...Ha!

Rusty Dose
Team Futaba
Team YS Parts and Service
SPA #213