Interesting that you all talk about 'what to do' based on being caught in cloud on an unplanned basis. I fly with an A/H and am happy to thermal in cloud using that. However, I always worry about what to do if the A/H fails. My glider has no backup blind flying instrumentation (unlike most GA aircraft which have an electric turn coordinator as well as a vacuum horizon - and which are more speed stable than gliders).

My plan, tested in clear and admittedly smooth air, has been to open the air brakes and take hands and feet off if either the A/H shows obvious signs of failing or the airspeed increases over a certain level (I plan on 75 knots). A misleading A/H would be far worse than an obviously failed one, because you would be in worse shape before taking this action. However I recently talked to someone who had the A/H in his LX computer fail while in cloud.. He kept things steady while rebooting the LX and all was well. I think I would stick to the open the air brakes plan.