Hi Andy,
you can get a result by producing one leg 7.5 rad & the second leg 7.49 rad then boolean union.
Then produce the inner with 5 rad & the second leg 4.99 rad then boolean union.
Boolean subtract inner from outer.
Now boolean subtract a 45 degree segment as shown in the photo.
You can now mirror a few times to get the complete manifold that can be boolean union to give a solid.
Cheers
Barry