Hi im putting a Hellcat ARF together and want to hide the exhaust for my os 120fs engine does anyone have some suggestions for a silent muffler for the 4stroke engine a want to place it inside the fuselage with some flex tube.and guide the exhaust below the fuselage.

http://www.giantscaleplanes.com/Hellcat_70.htm

Try Slimline inverted Pitts muffler like the one I have in my Hellcat:

Hi,
Richard has one good solution, and here is another:Tower (and elsewhere) sells an angled header for your OS 120FS. Also, they sell the flex exhaust tube. Screw the header into your muffler port, connect the flex tubing, locate where you wish to mount your silencer(muffler), screw the muffler into the bottom end of the flex tubing, and firmly support your silencer body--voila, you have what you desired. BUT---be sure to support the flex tube around its mid-point, else it will break due to vibration!! I use this method on my Great Planes PT-19.
I am building the same Hellcat from the Giant Scale kit. I will side mount a YS 91FZ with the Pitts Slimline muffler. I would enjoy occasional messages with you wrt progress and such.
I am [email protected]
Best wishes,
Jim