Cody,

I was going by the engine only weights shown on the Wren, Jet Central, and Jetcat websites. I assume that you are looking at the chart that is published in RCJI. I'm sure that there are some inconsistancies from manufacturer to manufacturer and perhaps on Tom Wilkinson's chart that make direct comparisons difficult. I can tell you that my Wren SS with mount, TC, and wiring harness weighs 2lbs. 4 oz. My comparably equipped Artes Bee on the same scale weighs 2 lbs. 0 oz.

I'd be carefull about comparing installed weights because Wilkinson's chart includes the weight of 5 minutes worth of fuel in that number. The SS installed weight looks quite favorable because it comes with miniature valves and a lipo battery, which means you'll need more nose weight. Some of the engines he reviewed two years ago have updated their equipment in the meantime.

The engine is mounted behind the CG and all of the other turbine equipment is in front of the CG with either mounting scheme. There aren't a lot of options on where to mount some of the equipment in the F-16. So it's primarily the engine weight that matters when you're trying to decide where to mount a particular engine. If you remove the 13 oz. tailpipe and move a 2 lbs.+ engine from 4 inches behind the CG to 2 feet further rearward you'll need a lot more nose weight. I allowed for the weight of the plywood mounts and even tailpipe insulation and in the case of my Wren SS the plane would come out slightly heavier if the engine were mounted in the tailcone. My guess is that if the engine were 4 oz. lighter (like a P-60 or Bee) then the plane would be slightly lighter.

Once you get your plane and all your equipment it's not hard for you to weigh everything, figure out placement of all the components for each mounting scheme, measure distances from the recommended CG, calculate the bending moments, and determine the extra nose weight required for balance. Based on my analysis it doesn't appear that there is a significant weight advantage, so where you mount the engine comes down to personal preference. If we were talking about larger heavier engines then they obviously should be conventionally mounted.

Joe