Countersunk the F-704H center section side plates.
These plates are countersunk for all the #40 holes. the #30 holes at the bottom do not need countersinking as they get AN470AD4 rivets
Using a setup with backing block of wood with pre-drilled holes to make sure the pilot of the countersink stays centered.
Both F-4704H finished. These are already primed so ready for final installation.
Deburred and dimpeled top line of the tailcone to receive the longerons.
I dimpled these using the pneumatic squeezer.
The last two holes are a problem to dimple. I rivetted too hight on the F-712 bulkhead and can't peel the skin back far enough to get the dimple dies in.
Will probable have to drill out one or two rivets here but will do that later on. So don't do this if you are rivetting the tailcone.
Next started countersinking the left longeron F-718L.
These will accept 0.032" #40 dimples for the sides. There are hundreds of them and the work is really dull.
On the top side for the canopy deck, the skin on top is 0.040" for #40.
In the rear section there are the rivets between rivets. All three are also countersunk.
The way I countersink the longeron is by claming it between the jaws of my vise. This can be done safely on the top side (because the bottom or side flange is not bent).
However be carefull if you clamp the top line of holes for the F-721B canopy deck. If you clamp here, you will straighten the bend in the longeron and undo your previous work.
you can countersink all the holes for F-721B but you can not rivet the last five holes aft yet at the F-757-S plate for the sliding canopy. (Detail A - DWG25)
I used a small woodblock to clamp at just one small surface for these as you can see in the image below.
Longeron completely countersunk and deburred.
I also deburred and dimpeled the F-721B-L. After that, installed it to verify the fit with the longeron and all came out great.
