Had a go at casting some lead ballast for the Stinger yesterday, this will be carried in the wing joiner and the rear wing pockets.
Eventually I decided to make the moulds out of MDF strip screwed down to a scrap piece of softwood. The problem with the MDF is that it tends to crack very easily when tightening up the screws, so next time I'll probably use something else. I had to decide on a compromise between either an open or closed mould. In the end an open mould was chosen for simplicity and ease of removing the lead slugs, the problem being is controlling the amount of lead during pouring and subsequent bubbles during the cooling, but in the end the final product is fit for purpose although it looks pretty rough.
The wing joiner slugs range in weight between 180 - 160g (the two moulds are slightly different) with the wing pocket slugs at 120g, total wing ballast comes to approximately 1300g plus 580g of fuse ballast equals approximately 1900g of total ballast, giving an all up weight of 4.2Kg.
The next problem is getting it to fit nicely in the wing joiner, the inside of the joiner is quite rough and will need some sanding and filing to get it to fit nicely so that it doesn't get stuck in the heat of competition.