All....Match drilled the bottom skin to the center section of the fuselage. My question is about the F-904 bulkhead. Except for the four holes on the forward section of the F-904 that the drawings specifically say to countersink it is assumed the other holes are dimpled....my assumption. So the question is should the F-904 bulkheads be dimpled or countersunk to accept the bottom skin. It will actually have the forward bottom skin and the middle skin riveted to the F-904 bulkheads. Thanks guys and gals.
Van's Air Force
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Fuselage Center Section Question
- Thread starter RVdreamin
- Start date
Just found the answer on the internet so its gotta be true 
....see paste below.
The most common RV-7/7A and RV-9/9A fuselage construction question?
Reference drawing #28: In all of the following text the part references are for an
RV-7/7A. The parts F-772, F-776, and F-704 should be F-972, F-976, and F-904
if you are building an RV-9/9A.
Regions of interest on drawing: Skins F-772, F-776, F-704 spar carry through
(A-9 and A-10), and NOTE #1 (G-6 and G-7).
The drawing indicates three different rivet situations for the two forward rows of
rivets where the spar flange of F-704 and the skin F-776 are "over lapped" by the
skin F-772.
The first situation involves the tricycle gear ?A? model kits only. The construction
plans state that the ?outboard? 5 rivets on both the left and right side of the plane
(most forward row in F-776) need to be installed ?double flush?. Having the
rivet?s shop heads on the inside of the plane flush with the interior surface of the
F-704 allows the tricycle gear leg socket to fully nest into position. To achieve
this, the builder will have to machine countersink the F-704 on the inside (top
surface of the flange of the F-704 if the plane is upright) so that the rivet, when
driven, will end up flush with that surface. On the exterior, the F-772 will be
dimpled and the F-776 and F-704 flange will be machine countersunk to accept
the F-772 dimple. Obviously the F-776 is too thin for a machine countersink and
the result will be an ?over countersinking? of that skin and a slight countersinking
of the F-704 flange underneath. This is standard practice.
The second situation involves the intersection points of the four forward floor
stiffeners with the F-704/F-772/F-776 flange and skins. It is denoted on the plans
with arrows and the comment ?SEE NOTE #1?. In this case, the key point is that
the builder should not for any reason dimple the flange of the F-704, as it would
complicate the fit of the floor stiffeners. In this case the same exterior process
should be used as in the first situation above. Dimple the F-772, machine
countersink the combination of F-776 and the flange of F-704.
The third situation involves all of the remaining rivets (the non-special case
rivets). You have two options. One is to dimple all three surfaces. The builder
will find the F-704 a bit thick to take a good dimple so if the dimple is found
insufficient, lightly machine countersinking the initial dimple will improve the fit
(nesting) of the dimples of the F-776/F-772 skins. The second method is simply
to continue the process used for the four floor stiffener locations. Thus machine
countersink the combination of the F-776 skin and F-704 spar flange sufficiently
to accept the dimple of the F-772. This will work fine.
....see paste below.The most common RV-7/7A and RV-9/9A fuselage construction question?
Reference drawing #28: In all of the following text the part references are for an
RV-7/7A. The parts F-772, F-776, and F-704 should be F-972, F-976, and F-904
if you are building an RV-9/9A.
Regions of interest on drawing: Skins F-772, F-776, F-704 spar carry through
(A-9 and A-10), and NOTE #1 (G-6 and G-7).
The drawing indicates three different rivet situations for the two forward rows of
rivets where the spar flange of F-704 and the skin F-776 are "over lapped" by the
skin F-772.
The first situation involves the tricycle gear ?A? model kits only. The construction
plans state that the ?outboard? 5 rivets on both the left and right side of the plane
(most forward row in F-776) need to be installed ?double flush?. Having the
rivet?s shop heads on the inside of the plane flush with the interior surface of the
F-704 allows the tricycle gear leg socket to fully nest into position. To achieve
this, the builder will have to machine countersink the F-704 on the inside (top
surface of the flange of the F-704 if the plane is upright) so that the rivet, when
driven, will end up flush with that surface. On the exterior, the F-772 will be
dimpled and the F-776 and F-704 flange will be machine countersunk to accept
the F-772 dimple. Obviously the F-776 is too thin for a machine countersink and
the result will be an ?over countersinking? of that skin and a slight countersinking
of the F-704 flange underneath. This is standard practice.
The second situation involves the intersection points of the four forward floor
stiffeners with the F-704/F-772/F-776 flange and skins. It is denoted on the plans
with arrows and the comment ?SEE NOTE #1?. In this case, the key point is that
the builder should not for any reason dimple the flange of the F-704, as it would
complicate the fit of the floor stiffeners. In this case the same exterior process
should be used as in the first situation above. Dimple the F-772, machine
countersink the combination of F-776 and the flange of F-704.
The third situation involves all of the remaining rivets (the non-special case
rivets). You have two options. One is to dimple all three surfaces. The builder
will find the F-704 a bit thick to take a good dimple so if the dimple is found
insufficient, lightly machine countersinking the initial dimple will improve the fit
(nesting) of the dimples of the F-776/F-772 skins. The second method is simply
to continue the process used for the four floor stiffener locations. Thus machine
countersink the combination of the F-776 skin and F-704 spar flange sufficiently
to accept the dimple of the F-772. This will work fine.
I'm at the same spot with my 7A build. I have a 2 stage squeezer that supposedly can squeeze 6000 lbs, so I dimpled the ones that don't have to be flush on both sides. Dimple shape seems to be good, but have not started riveting yet. If need be I'll touch it up with a slight countersink to make a flush fit with the skin.
