Dimple or countersink for floors?

[apatti]

For those of you that installed your floors with #8 screws...

I am assuming you countersunk the floor ribs. They are too thick to dimple. However, I am afraid countersinking for a #8 screw is going to go too deep. I guess this is the same issue as with countersinking the main wing spar for the fuel tanks. Comments (reassurance)??

While I am at it let me ask another question or two...

Did you use a #8 screw in every hole in the floor skin or every other hole? Are you happy with the results. There are some holes in corner areas that look like they will be real difficult to reach and I am thinking (wishfully, perhaps) I can get away without a screw there.

Thanks in advance!

[RVbySDI]

Originally Posted by apatti

For those of you that installed your floors with #8 screws...

I am assuming you countersunk the floor ribs. They are too thick to dimple. However, I am afraid countersinking for a #8 screw is going to go too deep. I guess this is the same issue as with countersinking the main wing spar for the fuel tanks. Comments (reassurance)??

While I am at it let me ask another question or two...

Did you use a #8 screw in every hole in the floor skin or every other hole? Are you happy with the results. There are some holes in corner areas that look like they will be real difficult to reach and I am thinking (wishfully, perhaps) I can get away without a screw there.

Thanks in advance!

I am assuming you are talking about dimpling for the 426 3-3.5 rivets for the nutplates on the floor ribs. Those ribs will dimple just fine. No need to countersink them. I am using all #8 screws in all the designated locations. You can tap these nutplates out to 8-32 if you feel they will be a problem to get to. I have not done that yet but may later on if I find it difficult to get to those screws.

[Rick6a]

It is not the same issue as the fuel tanks because in a nutshell, the fuel tank screw holes are machine countersunk through a relatively thick stackup of material...specifically the spar flange and the technique calls for using the previously installed nutplate as a guide for the countersink pilot.

Because I have some accessories installed underneath the baggage area floor I made the floors removeable. The floor stiffeners are thin enough to dimple and install K1100-08 nutplates. Use what the production guys use.....NAS1097AD3-3 or -3.5 rivets to attach the nutplates. Doing so will assure that you will not to produce a knife edge. Some corner areas are difficult or impossible to reach with a common "C" squeezer....yet another reason why I almost always prefer using an alligator squeezer, but that is the subject of another thread. Short of using an alligator, you can always dimple hard to reach holes with Avery's 8-32 close quarters screw dimpler.
Since my 6A was not prepunched, I had to lay out a suitable hole pattern so I cannot comment on the hole spacing issue.

[sf3543]

In my case, I did not countersink the screws for all of the floor panels. I just used pan head #8 SS screws. I countersunk for the nut plates and used oops rivets to rivet them on. Once the interior is in place, the only screws visible are the ones along the fuselage edge, and a few around the foot wells, and the round heads look just fine. I also used them in the baggage compartment and they are working fine for me. I used all of the prepunched holes and need an angle rachet screw driver to get at the ones in the corners, but I think you could leave them out with no problem.
I have seen countersunk floor screws and they do look nice, but too much work for me.