EF 110 Yak Having built several EF birds Ill skip the std wing, stab and rudder stuff and get to the core of my build. The motor, air box, pipe and install details that can chew up a lot of time and effort. I built this bird using the DA 85 and the K&S 1090 pipe. The DA 85 (in my experience) needs to have a pressure tape going back into the fuse. In addition the fus needs to be a pressure neutral environment. As a result I built a second removable firewall into the motor box in order to eliminate any pressure build up. Final results have proven to be very satisfactory in both my AW Yak and the new EF 110 Yak. First the motor box. I continue to use the 1 inch hardwood blocks and then glue 1/8 ply to the four sides. Very light, extremely strong and minimizes any potential vibration due to unsupported stand offs. It is a easy process. I cut the blocks on a chop saw, drill them out and then lightly bolt the engine to the firewall. At that point it is easy to glue the 1/8 ply to the top and bottom. After a few hours and the epoxy sets I do the side plates. Note in the pictures that there is a small hole in the side for hi/lo needle access and a plate to help hold the guide straws in place. It has worked extremely well and makes adjusting the needles much easier.