RE: DA-85 Question
Update on this : Last weekend I flew with a "balsa box" and it seemed to make no difference at all. Pics show the backplate I ordered from DA which has the nipple and the box.
I put a coat of dope on the box and now I think maybe that was a mistake (it should breathe "slowly" to allow changes in weather and heat so as to not form pressure I think). I went to about 800 feet high, rolled inverted, dropped to idle and held full down elevator for about 8 seconds. Then I gunned it and it abruptly quit.
Anyway, I need to try the baffle idea next. This box was easier for the time being as I needed to do maintenance on the muffler and smoke system anyway.
BTW, a friend with the same problem tried using a small 2 oz header tank with the same sort of arrangement and he said his motor wouldn't run with the line connected. I think maybe he did have a pressure build up but I can't prove it other than his ran "normally" when he disconnected the line. With the line on the header tank to the diaphram nipple, his engine sounded rich to him.