When 521/522 have dried, glue 521/522 and 518, 519 and 520 together on a flat surface. (top side down) As soon as everything is assembled, and before the glue sets, put the whole assembly back in the fuselage (don’t forge the cling-film). Parts 518 and 523 must be exactly aligned with formers 504 and 506. Cut-out to cut-out and contour to contour must match! Once the assembly sits properly, you can add bearers 523 and 524. Leave everything overnight to dry!
Next step is to add the corner reinforcements 527. If you worked carefully, you should be able to push the wood through the cut-outs in the formers along the sides.
Don’t worry about small!! deformations in the balsa surface. The 2 bottom longerons in the fuse have to be glued together with filler piece 528 to fuse-bottom 514. The bottom longeron run as far as the sides. Because all 4 longerons are fitted to the firewall, they must protrude at least 6 mm, to allow fitting the firewall later. When it all fits, remove them again and glue them in permanently. Wipe off any access glue.
Now we go back to the centrepiece. We can add the outer ribs 529 and 530 with the bracing support 531 (I think we are talking about the flying/landing wire supports, need to see the drawing to make sense of it!)
We first glue 529 and 530 together. Make sure the cut-outs for wingtube and spars stay free of glue, otherwise it will be a big job later to remove the hard glue. (When you use aliphatic glue, simply wipe the excess away with a damp cloth.)
The Turn-buckles have a left and a right thread. Do make sure that the eye with the LEFT thread is mounted on the brass support. (You are able to add an ordinary nut on the RIGHT hand thread, you use that during assembly to prevent the turnbuckle loosening itself. (good idea to leave those nuts on now!)
Bevel the edges of 531 at the ends, so that it sits flush against inner and outer ribs. Don’t remove too much wood, since considerable (flying) forces have to be transferred to the adjoining ribs and 518. When both 531 parts fit, you can glue the 4 blind nuts in with epoxy. I (Peter) always glue a a piece of lite ply on the back of the nuts, so that they don’t come loose in time. (Kees: If you tell me the size of the nuts, I’ll cut a bunch. He basically makes a washer with an inner hole, large enough for the blindnut to go through, and caps that off with another washer, with a smaller hole, large enough for the bolt to go through. It’s like a pocket. )
When the glue has set, trial fit the 4 turn-buckles 533 with brass part 534 (enlarge the 2 largest holes in the brass part to 4 mm!) and screws 535 and 536 and nuts 537. First mount the turn-buckles to the brass. Once the screw is tight, use a pair of sidecutters to gently destroy (NOT CUT) the protruding threads of the screw. This prevents it from ever coming loose. Of course you could use loctite or a lock nut. (I would !)
With the brass part and turn-buckles fitted square(!) on 531, it is time to trial fit this assembly into the slots of 518. Also add the 539/530 ribs. The 531 assembly should be square to part 518. To allow you to remove the turn-buckles easy, it is now time to make some cut-outs in the ribs at the location of the turn-buckles.