Today started off simple enough. When I countersunk the trailing edge wedge in the rudder a while back it worked very well on one side, but since the hole was enlarged by the first countersink the countersink cutter ‘chattered’ a lot when I was countersinking the other side. The result was the really rough holes you can see in the picture below.
I cleaned up these holes using a hole deburring tool and some elbow grease. Next my wife and I got everything set up to bond the trailing edge of the rudder together. The plans point out that a straight trailing edges on the control surfaces is very important and can affect the feel of the airplane if they aren’t straight. They suggest bonding the trailing edges together before you rivet them using either fuel tank sealant (which is an old method but still used by a lot of builders) or really sticky double sided tape. I decided to try the sealant this time since it is still a very popular method, and I hoped it would provide a strong enough bond to hide some of the dents I put in the trailing edge of one skin a couple weeks ago.
The basic process when working with the sealant is after you mix the two components together, you apply a thin layer to the trailing edges of the skins and then cleco them and the wedge together. You start at one end and roll on skin onto the other. While you work your way from one end to the other you rivet, using blind rivets, the stiffeners and the shear clips on the rudder skins together.
My wife and I went over the plan a few times to make sure we knew what we were going to do, but despite that we still ran into problems. It’s amazing how thick and sticky the sealant is. This makes spreading a thin layer on the trailing edge very difficult. You really want a thin layer because if it is too think then it can apparently prevent the two edges from coming together nicely. Oh, one more thing, the sealant has a working time of 30 minutes, and it took me about 20 minutes to get the sealant mixed and applied to the entire trailing edge wedge (the plans say to apply the sealant to the trailing edge but I chose to put it on the wedge so that it would be exactly where I needed it). So this meant we really had to hurry to get the rest of the process done, which resulted in some riveting errors.
When I set the first blind rivet the two stiffeners were not as close together as I thought which caused the rivet to expand a little between stiffeners. So now the two pieces are being held slightly apart from each other by the rivet. It’s tough to see but at the center of the picture, where the parts form the sideways ‘V’, is where the two parts are being help apart.
A little bit later I wasn’t paying attention to the position of the stiffener in relation to the shear clip. In the picture below you can see that the bottom stiffener attaches behind the shear clip and the top one attaches in front of the shear clip. Well, both of those should be behind the clip. Unfortunately I didn’t pay attention when I set the rivet that connects the stiffeners together, which is at the left of the picture, and once that rivet is set it isn’t possible to get the stiffener to the other side of the shear clip. Since I was worried about finishing within the sealant’s working time, I just set the other rivets and hoped it would be ok. A couple minutes later I did the same thing to another set of stiffeners…
These are pretty minor problems that I don’t think really need to be fixed. Regardless, I have sent out an email asking some other builders for their opinions on if they would fix them, and how difficult it is to remove the blind rivets. I’m really frustrated that I made these mistakes but it’s also nice to have the rudder that much closer to being finished.