Pond Skipper. The engine in the Scalpel was a Mangusta DR 049 with a Delrin plastic rear rotary valve. It was built by Tim Wiltse years ago. It wasn't spinning to well in that video. Later on, I was able to get it singing nicely with a different prop or glow head if I recall. Once it was sorted out, it flew the Scalpel with good authority. Unfortunately, the custom machined crankshaft broke at SMALL 2015. That was the end of what was probably the only flying Mangusta DR 049 in the world. I was never able to contact Tim to see if he might have any more of those cranks. I plan to install a TD on the plane soon so I can fly it again.