Rear Cowl Braces

You won't find this in the Rotorway construction material because it's not needed if you build the kit like RotorWay intended you to.

What causes this to be needed is when you don't cut the opening in the lower panels. Since we installed a cog belt drive in our ship we felt we no longer needed to cut the opening in the side panels of our ship.

The vacuum caused from the fan striving to grasp air and shove it through the radiator for cooling makes such a strong vacuum that along with the heat of the engine literally sucks the sides of the ship in toward the engine. We had two options. One was to add this extra bracing to counteract this problem or two, cut the holes into lower panels to relieve the vacuum.

We decided to not cut in the holes for 2 reasons, one being aesthetics and the second, airflow.

Looks wise we never did like the look of the holes exposing the ships innerds. Airflow wise looking at the way the ships air intake vents are configured, if you allowed the airflow to come from behind the engine it seemed to us there wouldn't be much air passing across the engine from the belly vent on the bottom of the tub. We even thought of closing off the vents on the upper side panels so the ship would have only two air entrances, the belly scoop and the top of the doghouse which there isn't a way of closing up.

Aesthetically the side intake vents look great, function wise they are made entirely wrong. With the forward part of the air vents recessed it makes them loose about 99% of their efficiency just like the one in the tub. I'm no aerodynamics guy by any means but from information I gathered and the sources it came from I'm pretty sure I'm right.

Purely by accident we discovered something about cooling.
When we got our ship finished and began hovering it RotorWay said to hover with the panels off because the ship will get more airflow into and through the radiator allowing it to run cooler.
When we did this we had slightly raised engine temps and very high oil temps.

 
It wasn't until we began going into forward flight after Phase II that we discovered with the
panels on we got slightly cooler engine temps and alot lower engine oil temps.

All was not well when we had the panels installed.  Flying, especially on hot days the side panels were sucking in until they bottomed out against the fuel tanks.

The cure was to add additional bracing inside the upper and lower panels. We still have a small amount of distortion in our panels from not having the braces installed.  My advice is to install these panels up front in the building process. That would make it alot easier to apply them because you could glass them in when the ship is hollow instead of after the ship is totally assembled like we had to do. There are a couple of ways you can do this. We chose to glass some aluminum tubes the same size and type as Rotorway did into the rear of the tub. You can also just glass some fiberglass angle pieces to do them similarly to the ones Rotorway provides you with for mounting the FADEC readout unit to the instrument panel with. That would be lighter for sure but we didn't know exactly what would happen when the panels got hot so we opted for the tubing. Be sure not to use pressure when you clamp them to the panels or you'll see their impression on the outside. The fiberglass resin softens the surface a bit and allows this to happen so no pressure at all is to much.

END