Trent's RV14 Build: 7-10,11: Riveting Rudder Skeleton / Fixing Rudder Skin dings

Rudder Dings

When i got the rudder down to Pete's place, i flipped it over on his bench and was completely dismayed to discover that there were some very small 'outie' dints in the skin. It was all i could do but to cry! It seems that when i riveted the rudder stiffners / shear clips together, the hand riveter had banged into the rudder skin and left some dints. I did a test on some 0.016 scrap (same thickness as the rudder skins) and it is remarkably easy to dint this skin. Pete recommended that i lay down some rubber next time: good advice. It turns out that the rivet gun i have is rubbish and really takes a lot of force to snap off the mandrels - meaning the gun really bucks around when the mandrel snaps. So i think i will buy a better quality rivet gun - probably this one.

Pete told me not to dispair however, as i could fix the dints by rubbing them out with the back of a spoon and some grease or vaseline for lubrication. So i got a practice piece of 0.016" and dinted it purposefully with the rivet gun so i could practice getting the dints out. This seemed to work ok, so i moved on the rudder itself. The only word of caution i will give here is DO NOT EVER EVER EVER hit the skin EVEN LIGHTLY with a hammer!!!!.... I was working out the fist dint, and i decided it may go quicker if i just very lightly hit the dint with a soft faced hammer... well this was a BAD IDEA! It resulted in about a 10c piece sized gently 'innie' dint in the skin - much worse than the original dint every was. I was thankfully able to gently massage this out with the back of a spoon from inside the rudder. Overall i was able to work out all the dints in the rudder skin (about 10 of them) and i am now happy.

Below are some photos of the rudder dints after working them out - i don't have any before shots, as they were very hard to get in camera.

7-10: Rudder Skeleton Riveting

Page 7-10 has you insert the rudder skeleton into the skin assembly then begin riveting. It calls for the riveting of the left hand side rudder fairing attach strip aft 8 holes only. You then rivet in the horn brace, and finally finish up riveting the holes common to the skin, bottom rib and attach strip.

There is one rivet that is located aft of the left hand side attach strip, which joins only the R-00904A-1 bottom rib to the left hand skin (with no attach strip). The plans actually never call to rivet this any any stage in the plans i can see, so i went ahead and riveted it at this time. I was able to get in there using the brand new low profile yoke from Cleveland, and by peeling the trailing edge slightly apart.

I made an error here when riveting this attach strip, and actually riveted the whole line of rivets (not just the aft 8 ones). I looked ahead and figured this wouldn't be a problem - but it was (see below).

I then used LP4-3 rivets to attach the 2 bottom ribs together. These went ok, but i found that some of the rivet mandrels were breaking off half way up the mandrel. I am pretty sure this was happening as i was not holding the rivet gun perpendicular to the workpiece (as the thickness of the gun head was interfering). Once i worked this out, and ground the head of the gun down, the rest of the rivet mandrels were ok. I very very carefully used a dremel to cut the mandrels off the rivet heads. I didn't punch the mandrels through, as i believe they are structural in shear for these rivets.

7-10 Step 4 and 5

Moving on, it was time to install the horn brace (and here is where my troubles started!). Because i had mistakenly riveted all the rivets on the attach strip, the forward most rivet interfered with the horn brace and i could not get it installed. No problem, i am good at drilling out rivets... however not in this case! One of the rivets i was able to drill out the head ok, but when i tried to punch it out, it simply would not budge. I think it had expanded between the attach strip and the rib below it. A lesson was learned here - for the aft rivet in any line, you really need to clamp the parts together as there is nothing stopping the end of the part from lifting. An alternative would be to use a bit of small rubber fuel tube to help keep the parts together - must remember to do this!

In any case, i needed to get this rivet out. So i tried using a #41 drill bit to drill the shank out, but did a terrible job of it and elongated the hole!! doh!!! No problem i thought, it was time to get out the oops rivets.

Given the whole point of drilling these out was to get the horn brace in, i then cleco'd the horn brace in and used the LP4-3 rivets to attach it to the bottom rib. At this point, before i riveted the brace in any further, i figured i better get the 2 rivets back into the rudder attach strip / lower rib on each side. And here is were more troubles began!!

I found that there was simply no way to rivet these last rivets successfully with the horn brace in place, as the horn brace did not give enough room for either a bucking bar, not a squeezer set! The oops rivet was so bad that when i shot it, the bucking bar was only half on the rivet - what a mess!!

So catch 22 - i can't seem to get the horn brace in with the last 2 rivets on the attach strips installed, and yet i can't seem to rivet those last 2 rivets with the horn brace installed!! What a pickle.

So what to do?

In the end i really didn't want to use MK319 pull rivets on the lower rivet line if i can avoid it (especially one in the middle of the line!) - so i drilled out the LP4-3 that held the horn brace onto the lower ribs and removed the horn brace. I then riveted the last rivet of the attach strip with a normal AD3 rivet on one side, and an oops rivet on the other side (due to the enlarged hole). This all came out ok. Now, how to get the horn brace in?

It turned out, all i really needed to have done in the very first instance, was to man-handle the horn brace into location. At the end of the day, when i realised my mistake of riveting the whole line of rivets, and had the initial issue of the horn brace not fitting, i drilled out the last 2 rivets in a hurry, with false confidence and not fully thinking it through. This resulted in hours of unnecessary work, and the elongation of a hole needing an oops rivet. If i had have just slowed down and thought things through, i may not have had the issue. Lots of lessons today!

Here you can see the OOPS rivet installed, and the slight paint scratches from man handling the horn brace into position. The silver ring is from where the initial oops rivet was bent over when i tried to rivet it with the horn brace in place. This rivet is set nicely even though the picture looks different. I will just touch these bit up with a brush next time i have a batch of primer mixed.

Riveting the remaining rivets on the horn brace was no issue with the squeezer and the longeron yoke, however i really could not reach the forward most skin / brace rivet on each side, and didn't own a bucking bar that reached into that space. So i decided not to be a hero, and updrilled to #33 and used a MK319-BS rivet here.

MK319-BS rivet installed in the forward most hole. Can always fill these later on.

Step 7-11: Riveting the counterbalance rib, spar and top rib

Next up was page 7-11, riveting the counterbalance rib to the skins. This was done with the swivel head mushroom set and the tungsten bucking bar. This all went well, except in the middle of the rivet line on one side i let the mushroom set wander and bent the very edge of the skin around the curve of the edge of the underlying rib - thankfully no damage to the rib itself. I was able to straighten this with a wide chisel without any issues.

The very small bend on the edge of the skin

Once this was done it was time to relieve the edges of the counterweight where it contacted the rivets. I realised that i had forgotten to prep and prime the R00001 plate which holds the 2 nutplates, so i deburred this, cleaned and just used some white etch primer on it. I forgot to countersink for the nutplates before priming, but did this afterward and installed the nutplates. The counterweight could then be installed in the final position. I used NAS1097 AD3-3.5 rivets on the nutplates instead of the called out AD3-3.5 rivets. These have a smaller head, and you can therefore countersink more easily - i could have countersunk for the AD3 rivets here as the plate was thick enough, but wanted to try out the NAS1097 oops rivets for this application, as there are other places in the kit where i will be doing this. The theory is that a nutplate rivet only needs to be strong in shear (to stop the nutplate rotating), so you can use a smaller head size rivet with no problems.

Counterweight installed - i used the orange stuff more as a test because i had never used it before.

Once the counterweight was in, i then used the squeezer to rivet the line of AD3-3.5 rivets along the spar / skin. I had a lot of trouble with these rivets - they looked ok then i was squeezing them, but when i flipped the rudder over, many of them had been bent over! In the end i had to drill out around 40 rivets out of the 100 on the two sides. Pete mentioned that a lot of the time, when this is occuring it is due to the river being too long. So i placed a -3.5 rivet into a hole and used my gauge - the rivet was very slightly longer than needed. I then put a -3 rivet into the hole, and it was very slightly shorter. So i ended up using the AD3-3 rivets in the 40 locations, and these squeezed much better.

Next up i riveted the top rib into place using the squeezer - and also finished the final rivets where the 2 skins overlap. MK319-BS rivets were used in the last 3 holes on each side of the top rib, as the gap is just too small to fit a bar in.