Hard data.Â* That what this site needs more of.Â* Thanks, Mark.

On 9/21/2019 7:06 AM, wrote:
The main reason motorgliders like the Arcus see such a large decrease in performance with the mast up is that the engine bay doors remain open, and they are about six feet long. That's a huge amount of drag. When we installed jet engines in the Tst-14 and four Arcuses, we had the main doors close over the engine bay and two small "sub-doors" open around the engine mount. With the engine extended, we measured the L/D of the Arcus J (jet) at 38:1. The Arcus M gets 13:1 with engine extended.

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Dan, 5J