On Sunday, August 23, 2015 at 10:47:29 PM UTC+1, wrote:
I reviewed this news group, Buttler/Nixon/Murray vent and DG's page on Mandl air extractor. Could not find a suitable reference for and extractor for a sustainer or motor glider. I did note that the open tails of DG and LS gliders apparently did not do a good job of extracting air, hence the Mandl, which according to comments on this news group does not good avery effective job either. Anyone come up with a good method of extracting air from a glider with a fuel tank in the baggage compartment?

Look at the Jonker Sailplanes website for one example