Looks like the plane is too heavy. It took off OK on the first try, but I couldn’t get it to lift on five goes past that. The first flight was probably due to the little bit of extra voltage a freshly charged battery has.

I did some measurements and the plane with autopilot is 1130 g, which is 255 g / 30 % higher than the design flying weight of 875 g. 110 g of that is in the MDF plate and 50 g is in my usual higher capacity batteries.

Next step is to redo the plate in polystyrene. I’m tempted to follow Z-8’s instructions and change the prop to a APC 10×7 E and upgrade the motor to a Super Tigre .10. The Super Tigre has a higher constant power (320 W vs 210 W), is a drop in replacement, and as a bonus saves 50 g.

Edit: annnd I crashed it 🙂 I fitted a 10×7 prop and new receiver and got the elevator direction wrong. The good news is the 10×7 makes the plane leap away. The bad news is it lept away into the ground…