Hi All- I also did a semi circle in fibreglass. It weighs 11kg so same as steel isogrid. It deflects 0.23mm so is ahead of the isogrid but not as good as the steel semicircle. The FG section is 20mm thick. If I went to CF then it would be lighter and as good as the steel semicircle but 20mm of CF is costly. Easy enough to make the section bigger to get to the required deflection but then loose apples to apples on envelope.
Meant this for the other thread!!