Spar Bolt to Seat Rib Interference

[WingsOnWheels]

Per the plans, the center seat ribs are placed with the web 2" off centerline (going from memory). My pre-drilled spar also has one of the big spar bolts dead center 2" off centerline.

How have other folks delt with this interference? I have a newer fuselage kit that came with the lightening holes in the seat ribs already cut out so making the hole smaller is not an option.

The ribs came from the factory already notched to clear the splice plate leaving about 1/2" of web material between the notch and the lightening hole.

This is only a problem on the upper splice plate since there is ample material at the lower splice plate to increase the size of the notch.

Pictures would be appriciated.

Here is a picture of the removeable rib, you can see the upper notch I am talking about. Other than this rib being split, this is pretty much how it came from the factory. The fixed sister rib on the other side of centerline has the same notches.

 

[WingsOnWheels]

Nothing?

I spoke to Ken at Vans and he said that this is a common problem and to just cut back the material for clearance. To clear the bolt it would probably leave 1/8" of material behind which doesn't seem good. I might be better off cutting that section out completely rather than leave that tiny bit of material.

 

[ChiefPilot]

Nothing?

I spoke to Ken at Vans and he said that this is a common problem and to just cut back the material for clearance. To clear the bolt it would probably leave 1/8" of material behind which doesn't seem good. I might be better off cutting that section out completely rather than leave that tiny bit of material.

I had the same problem on mine last year when I put the wings on. I ground most of the rib away in that portion, so much so that what was left wasn't really useful and I took that out as well. After the spar bolts were in place, I riveted a doubler of sorts to the seat rib, replacing much of the metal removed earlier.

 

[WingsOnWheels]

That's a great idea, it is not like I am going to be taking the wings off on a regular basis anyway.

 

[az_gila]

I had the same problem on mine last year when I put the wings on. I ground most of the rib away in that portion, so much so that what was left wasn't really useful and I took that out as well. After the spar bolts were in place, I riveted a doubler of sorts to the seat rib, replacing much of the metal removed earlier.

When you were all done, how many of the three screws that go into the spar bulkhead did you use?

Or are you saying that you didn't use any of the "upper" rib?

 

[ChiefPilot]

When you were all done, how many of the three screws that go into the spar bulkhead did you use?

Or are you saying that you didn't use any of the "upper" rib?

Perhaps my memory is failing me, but I don't recall any screws going into F-604. This was not the rib with the removable portion, but rather it's neighbor on the other side of the control column.

Picture the seat rib where it joins F-604. On my kit, the rib lined up exactly with one of the top spar attach bolt locations, almost dead center. Removing enough material to get the washer and nut along with some space for a thread or two of the bolt to fit left very little material there, so I took that out as well. After securing the wing mounting hardware, I installed a doubler made from .032 on the rib, replacing the lost material and extending slightly into the lightening hole. It's riveted to the seat rib above and below.

Again, I don't recall any screws associated with this rib (other than those holding the seat pan in place).

 

[WingsOnWheels]

When you were all done, how many of the three screws that go into the spar bulkhead did you use?

Or are you saying that you didn't use any of the "upper" rib?

Gil,

Did you have any interference issue on your 6A? If so, how did you handle it?

To clarify what brad said. As I understand, he cutout the material where the splice plate passes through and then later added a doubler. This would not effect the screw placement. See Picture Below, cutout area in red.

 

[az_gila]

Gil,

Did you have any interference issue on your 6A? If so, how did you handle it?

To clarify what brad said. As I understand, he cutout the material where the splice plate passes through and then later added a doubler. This would not effect the screw placement. See Picture Below, cutout area in red.

Only got the wood spar and steel strap mounted, but I have a 7/16 "slot" to the spar bulkhead - plans call for 1/2 inch.

I think 7/16 should be OK for the 1/4 inch steel spar connect strap and the bolt head/thin washer.
Note : the 1/4 steel strap thickness is from memory, I'll measure it tomorrow...

I think that bolt wll be installed from the rear.

 

[WingsOnWheels]

Only got the wood spar and steel strap mounted, but I have a 7/16 "slot" to the spar bulkhead - plans call for 1/2 inch.

I think 7/16 should be OK for the 1/4 inch steel spar connect strap and the bolt head/thin washer.
Note : the 1/4 steel strap thickness is from memory, I'll measure it tomorrow...

I think that bolt wll be installed from the rear.

I did a quick measurement: The AN365-624 nut plus AN960-616 washer stack up to about 1/2". Add that to the 1/4" splice plate and you are well over the 1/2" notch called out in the plans. The factory notch in my seat ribs is about 3/8" so I will have to make some room for sure. With the seat rib web centered on the bolt hole, there is no good way to install the bolt from the rear so I will just have to make clearance for the nut on the aft side of F-604.

 

[az_gila]

I did a quick measurement: The AN365-624 nut plus AN960-616 washer stack up to about 1/2". Add that to the 1/4" splice plate and you are well over the 1/2" notch called out in the plans. The factory notch in my seat ribs is about 3/8" so I will have to make some room for sure. With the seat rib web centered on the bolt hole, there is no good way to install the bolt from the rear so I will just have to make clearance for the nut on the aft side of F-604.

On mine, a bolt install from the rear at the top location looks like it should work. With the partial rib out there is more room that direction for installation...

The lower bolt has more clearance on the aft side as the picture in the first post shows so it should be able to go in either direction.

Added

I just checked a NAS 1306 bolt specification.

The head is 0.123 thick (max) so with the 0.250 plate and a thin washer of 0.032 = 0.453

The 7/16 I measured is 0.4375, so I will need just a little more trimmed off to make the notch deeper, but still no need to remove that rib section.


Note that the seat rib does not have to be installed when the wing bolts are installed - so I don't quite understand your comment "With the seat rib web centered on the bolt hole, there is no good way to install the bolt from the rear"

 

[WingsOnWheels]

On mine, a bolt install from the rear at the top location looks like it should work. With the partial rib out there is more room that direction for installation...

The lower bolt has more clearance on the aft side as the picture in the first post shows so it should be able to go in either direction.

Added

I just checked a NAS 1306 bolt specification.

The head is 0.123 thick (max) so with the 0.250 plate and a thin washer of 0.032 = 0.453

The 7/16 I measured is 0.4375, so I will need just a little more trimmed off to make the notch deeper, but still no need to remove that rib section.


Note that the seat rib does not have to be installed when the wing bolts are installed - so I don't quite understand your comment "With the seat rib web centered on the bolt hole, there is no good way to install the bolt from the rear"

I am not refering to the removeable rib, there is no issue there. The sister rib on the opposite side of the centerline is riveted in place so is not removeable. As an option, you can split both these ribs to make installing the controls a bit easier, but the 'standard' is to split just the one rib.

I used the picture of the split rib since it was the only good picture I had of the notch. However, the issue isn't with the removeable rib. I should have used a different picture for clarity. If you split both ribs then there is no problem with installing the bolts facing forward. I didn't split both so I can't put the bolt in that direction.

 

[az_gila]

I am not refering to the removeable rib, there is no issue there. The sister rib on the opposite side of the centerline is riveted in place so is not removeable. As an option, you can split both these ribs to make installing the controls a bit easier, but the 'standard' is to split just the one rib.

I used the picture of the split rib since it was the only good picture I had of the notch. However, the issue isn't with the removeable rib. I should have used a different picture for clarity. If you split both ribs then there is no problem with installing the bolts facing forward. I didn't split both so I can't put the bolt in that direction.

OK, if it's the fixed rib - the second one out from the center - then my spar holes do not exactly line up with those ribs.

That makes the second rib is outside most of the main 1/4 spar plate reach.

The spar plate is 6.125 inches out from the center line... the second rib center line is 4.875 + 0.6875 inches from the fus. center = 5.5625 inches.

The second rib flanger faces inwards so the actual rib is another 5/16 outwards.

This gives the actual second rib at 5.875 inches out.

The spar plate only "pokes through" this rib for it's last 3/8 of an inch - no bolt heads should be involved. The notch only needs to be 1/4 for the spar plate thickness.

Is it possible that you mounted the second seat rib facing the wrong direction - i.e., swapped left and right ribs? See plans sheet #31.

 

[WingsOnWheels]

OK, if it's the fixed rib - the second one out from the center - then my spar holes do not exactly line up with those ribs.

That makes the second rib is outside most of the main 1/4 spar plate reach.

The spar plate is 6.125 inches out from the center line... the second rib center line is 4.875 + 0.6875 inches from the fus. center = 5.5625 inches.

The second rib flanger faces inwards so the actual rib is another 5/16 outwards.

This gives the actual second rib at 5.875 inches out.

The spar plate only "pokes through" this rib for it's last 3/8 of an inch - no bolt heads should be involved. The notch only needs to be 1/4 for the spar plate thickness.

Is it possible that you mounted the second seat rib facing the wrong direction - i.e., swapped left and right ribs? See plans sheet #31.

Not the second rib out. There are two ribs each 2" off centerline. Per plans, one rib is split and the other is not. Splitting the second rib is an option, but not required. I am refering to F-619R which is not split. F-619L is split and as such has no interference issue. F-619R is not split and has the web centered over the spar bolt hole.

 

[az_gila]

Not the second rib out. There are two ribs each 2" off centerline. Per plans, one rib is split and the other is not. Splitting the second rib is an option, but not required. I am refering to F-619R which is not split. F-619L is split and as such has no interference issue. F-619R is not split and has the web centered over the spar bolt hole.
<pic snip>

Ahh... a new RV-6 plans "funny".

Rev 1 on plans sheet 31 shows the nutplate mounting for both of those center ribs to be split. That's what I did when I made that bulkhead.

I didn't know splitting only one one was an option - installation of the controls would be much harder with one one being removeable, having just done that in the last couple of days.

For that rib, you are certainly correct that the bolt is in line with the rib...

If you have the nutplate mounts in the main spar bulkhead you could still split the other rib with a cutting wheel on a Dremel. Just mount the 0.063 plate, drill it for the rivets and bolts while the rib is intact, remove it, split the rib and then rivet it.

 

[WingsOnWheels]

Well, That explains or communication issues for sure...haha. I think that section is shown differently on the two drawings. In my manual, it says it is an option, but who knows if that is true on all revs of the manual.

From the manual for reference

I am going to do a test-fit of the controls when I get home to make sure I can get them in place with the one split rib.

 

[RViter]

My reinforced rib solution

Colin - This is the pic I emailed you and the reinforcement should be visible on the split rib. Have not split the other rib or trimmed back for the nut to clear it. So it will probably need to be done.