NorthernRV4

NorthernRV4

Well Known Member
I need some advice on planning out the rivet spacing on the Horizontal stab ribs, specifically where the mid and root ribs intersect with the forward spar channel. Both of these ribs have a joggle on the flange to allow it to fit inside the channel of the forward spar. In order to plan out my fluting locations I needed to lay out the rivet locations. Drawing 3a indicates 1.25" nominal spacing (can be closer but never further apart) but this places a rivet directly in this intersection area. It doesn't look like I can skip over this area without breaking the 1.25" rule and to put a rivet here will barely catch the area of the rib flange inside the spar channel and certainly not meet minimum edge distance of .25"

Mid Rib


RV-4 HS stab by jim_soutar, on Flickr


Untitled by jim_soutar, on Flickr

Root Rib


RV-4 HS stab by jim_soutar, on Flickr


Untitled by jim_soutar, on Flickr

Should I simply remove more of the flange so that the rivet will only pass thru the skin and the spar channel?

Should I not put a rivet here at all and rely on the rivet line along the forward spar (skin attachment)?

Thanks all.
 
AC43-13

If you don't have ED for the rivet hole, do not put a rivet there.

While you are at it, you might want to extend the .063 plate in the center of the fwd spar outboard a few inches on each side...

Carry on!
Mark
 
Adjust your spacing to insure you have the edge distances where you can along the main flange. Rivet spacing is really a maximum. A rivet fan somes in handy, but if you need to adjust one to 1" or something on the end of a line, it doesn't look bad.
In regard to the flange overlap where the joggle is, this is classic RV3,4,6 problem and really no fix short of rebuilding the entire flange or scabbing in a repair.
If you look at the pictures in the SB thread, you will see some very good examples of how most have handled this.....they put a rivet in there as best they could to average the edge distance on both parts, probably not meeting the minimum on either one.
Build on.....http://www.vansairforce.com/community/showthread.php?t=109360&page=61
 
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...and another quick note, I would be putting in the SB parts right now. It does not look like you are doing that.
 
Rivet spacing (pitch)

If you have a rivet fan spacer just use it to get a good even spacing as long as you don't exceed 1.25" or less than 3 times the rivet diameter. That's how I would do it.
 
Thanks fellas. On the mid rib location I am able to alter the spacing a bit but with the root rib I can't move them any closer together without getting into the joggle area and would definitely not maintain proper ED on the flangle/joggle area. Really not sure what to do here. I can leave that one rivet out and try to space the line that runs along the flange of the spar channel in such a way that the nearest rivet might be around 1.25" away but off to one side of the intersection area.

As for the SB 14-01-31, currently I understand it to only apply to the forward spar area on the -6/7/8. The SB that applies to the -4 only pertains to the elevator spar. TBO, this does not make sense to me because I thought the -6 empennage to be the same as the -4 but I don't have a set of plans for a -6. I did wonder how this might affect my -4 in the future though. I've also seen some Rocket builders put a .040" spar doubler on the aft side of the spar and I've seriously considered this mod even before the AD was issued.

http://www.vx-aviation.com/sprocket/empennage.htm

This builder seems to have skipped over the area that I am wondering about so maybe this isn't a huge issue after all. As a new builder I have an underlying fear that one faulty rivet will cause the whole thing to fail.
 
a very good example

http://www.vx-aviation.com/sprocket/empennage.htm

Very nice work indeed. Yep - that's exactly what I meant as a mod to the fwd spar. No need for compliance to the SB if you build it this way.

On the F1, we used a .125 doubler (!!!). No spar SBs for us!

FYI I am the person referred to in the mod description.

As for the rivet spacing conundrum, think 'tractor' and not 'space shuttle'. I repeat again: do not put a rivet where it will not have proper ED.

Carry on!
Mark
 
JonJay said:
...and another quick note, I would be putting in the SB parts right now. It does not look like you are doing that.
Click to expand...

There is no SB for the horizontal on an RV-4. It is not like the 6, 7 or 8.

As for the OP. Make sure you maintain edge hole distance on the spar. If the rib ends up being right on the edge then just cut it off so it won't develop a crack. I had the same question for Vans and that's what the engineer told me.
 
Sid Lambert said:
As for the OP. Make sure you maintain edge hole distance on the spar. If the rib ends up being right on the edge then just cut it off so it won't develop a crack. I had the same question for Vans and that's what the engineer told me.
Click to expand...

Not exactly sure what you mean Sid. Do you mean that if a rib flange ends up being on the edge of a rivet hole to cut off the flange to clear the rivet?

In the end I think I'll end up building it like vx-aviation did and add the aft spar doubler to the front spar.
 
I've laid this out a few different ways now and I think this method gives the best compromise of consistent spacing and maximum distance.

Root Rib


Final rivet spacing HS by jim_soutar, on Flickr

The last two rivets aft of the spar are 1" apart and the next rivet is 1.75" but with the first rivet on the spar line there is about 1.125" max distance at a slight diagonal.

Mid Rib


Final rivet spacing HS by jim_soutar, on Flickr

Similar to the root rib this layout puts the max distance between the spar rivet and the next one directly aft at 1.25" at a slight angle.

Someone correct me if this is not ideal please!! Thanks all for your help with such a simple question.
 
think about riveting when locating holes

I think your spacing on the center rib will give you a headache when you try to rivet the skin on. I would consider cutting the flange back on the rib and putting a hole thru the spar flange and the skin only. That way the rivet on the outboard side of the rib will be as far as possible from the rib web to make bucking this rivet as easy as possible. Since the foward spar is swept aft, the angle between the rib and spar flange is less than 90 degrees. That really adds to the "fun" when bucking those rivets to close out the skin. As said many times here, "ask me how I know."
 
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