I am making final dimples and counter sinks on all center section parts. I carefully read the posts here and in the instructions especially in regard to countersinking the F-904A which calls for double counter sinks for five double flush rivets on either edge of the bottom panel and the other four C/S rivets specified. I elected to C/S that entire line as suggested by the common questions section. This 904A forward half of the 904 wing spar then does not require dimpling.
My question is then what to do for the bottom skin attachment to the 904B rear half of the wing spar. I am assuming that the skin is dimpled and this section of the wing spar is countersunk all the way across. The "skin" is actually two overlapping layers of aluminum just as with the 904A. This would require dimpling both skin surfaces, followed by the C/S of the bulkhead flange.
This is probably obvious to you guys, but I have made enough stupid mistakes that I thought it prudent to check first! I saw nothing mentioned in the instructions or here in the forum.
HOLD THE PHONE! Maybe the better way is to dimple both the skins AND the 904B here. The flange is not that heavy in this area. Maybe easier and even stronger? What do you think?
OR.......I could do the same as with the 904A attachment and C/S the skins completely and not touch the spar flanges.
Thanks for any help.
My question is then what to do for the bottom skin attachment to the 904B rear half of the wing spar. I am assuming that the skin is dimpled and this section of the wing spar is countersunk all the way across. The "skin" is actually two overlapping layers of aluminum just as with the 904A. This would require dimpling both skin surfaces, followed by the C/S of the bulkhead flange.
This is probably obvious to you guys, but I have made enough stupid mistakes that I thought it prudent to check first! I saw nothing mentioned in the instructions or here in the forum.
HOLD THE PHONE! Maybe the better way is to dimple both the skins AND the 904B here. The flange is not that heavy in this area. Maybe easier and even stronger? What do you think?
OR.......I could do the same as with the 904A attachment and C/S the skins completely and not touch the spar flanges.
Thanks for any help.
Last edited: