Cowling 10/8-2007 The Cowl usally comes with the kit, however, since we have decided to go with a wankel instead of a Lycoming, the standard cowl dosn't fit. Being the first to get the engine and the first (to my knowledge) to use it in a 10, we have to do the cowl ourselves. No big deal, just add's to the homebuilding feeling. Unfortunately we have been forced to wait for a long time to get the engine, but the setbacks Mistral encountered along the way, has been fixed and the light at the end of the tunnel shines brightly. We recieved the mockup engine about a month ago, and have been busy making the cowl. We started the process of making the cowl, by strapping the engine on the airframe. The second step was to figure out, how much clearance we needed around the engine. We also had to bear in mind that we didn't have a prop on it, and we also needed to take into account that it was a "dry" engine. Mistral provided the information we needed and we strapped some weights on it, to simulate the weight of the missing items. The difference with and without these items, was 5milimeters. When everything was sorted, we put distancepieces on the engine. We installed thin pieces of wood along them to give a rough outline. We put some stainless mesh on top of that to make a base of the final mould. The airintake was shaped using foam Heated clay is smeared around the mesh. Don't use ordenary clay, the clay that we use are specifically designed for this kind of work. It get's hard as it cools and is great for shaping moulds. When the entire cowl is covered in cla, the shaping begins. It's a long process if you want to do it right. The clay was covered in fibreglas, when it had the shape we were looking for. The cowl is done in two parts, top and bottom. When the fibreglas is cured, you remove it from the clay. The final cowl is then done in glas and epoxy inside the firbreglas mould. We can do as many as we want inside it, incase someone else want's to use the same engine for the RV10. The cowl is constructed, in a special kind of epoxy able to withstand the high temperatures from the engine. The first thing to do, is to lay up a few layers of glas/epoxy in the mould. What you are looking fore, is a sandwich construktion. Which is stronger than "pure" epoxy/glas. This is done, by putting a core of foam, in between the layers of epoxy. fast imellem glaslagene. The cowl needs to cure, when it is donee. Epoxy is rather slow at that, the curing time a room temperature is around 24hrs. It is, however, nescessary to heat it to 55 degrees celsius to "outgas" it. If you don't, you risk that it will do it just by standing in the sun. This would lead to cracks in the paint. We built a box, containing an oven, a thermostat and a small blower. This enabled us to keep a constant tmeperature of 55 degrees for 12 hrs. That sorted, we "just" need to fill and paint the thing.