Is Vans contradicting themselves here?
I talked to Van's this morning, they had a few things to say:
The trim tab sticking out past the trailing edge has little or no aerodynamic affect. They have seen some stick out as much at 2-3 inches on some of the older DIY kits.
The edge distance rule is not as set in stone as I presumed, it can be less based on many factors: thickness of material, type of material, load type, etc. In this case there are many more rivets than needed, the forces are not shearing forces, and it is under relatively little load,etc.
Basically I am overly concerned, build on.
So it has taken me a while to reply to this thread because I needed to go back and research my own posts to see how I resolved these problems. After reading this response from Vans I wanted to review what was stated in the plans. I found the step that says to take the trim tab and align both the trailing and inboard edges with the elevator. In parentheses it then states: "(The alignment of the trailing edge being the more critical one.....)"
I took the use of that word "critical" quite literally, and therefore I was determined to ensure that the trailing edge of the trim tab was properly aligned with the elevator. Now I am even more curious about what they actually meant when they used the word "critical" in the instructions, compared with the response they gave you.
In any event, how did I resolve the dilemma you have been facing? I simply sacrificed about 1.5/32s of edge distance (one half the rivet width) on some of the rivet holes on the outboard edge of the hinge flange that is attached to the elevator so that my trailing edges all lined up. I also had to trim a small amount of the outer edge of the hinge flange away to maintain clearance with the radius of the trim tab rear spar for about the last 1.5 inches or so toward the outboard end of the elevator. All of my holes for the hinge on the trim tab itself were drilled right down the center of my reference line, which I drew 3/16 from the outer edge of the hinge flange (did not follow the 1/4 inch statement in the plans - there are many former posts about this dilemma here on VAF)
So yes, it matters where you draw your reference lines on each hinge flange, and yes, even after doing this as accurately as possible, you still end up sacrificing some edge distance for some of the holes in the hinge on the elevator side in order to make the trim tab trailing edge fit.
If you wish I can supply links to the appropriate posts, or some of the pics that I took. I wanted to spare you from having to dig for pertinent info because these posts are long and involved, and the relevant info is imbedded deep inside several of my posts. My trim tab experiences begin in November of 2011 and continue into January of 2012, so you can use the date links on the left pane of my blog site and the search and label functions as you wish.
It is not my intent to muddy up your thinking about how or if you should resolve the trailing edge misalignment you are experiencing, but I found it a bit strange that Vans seems to be contradicting themselves just a bit when comparing the statements in the plans to what they told you recently. I opted to do what it took to align the parts correctly per the statement in the instructions, since the deviations from edge distance requirements in order to make them fit were minimal in my opinion.
The real problem is twofold: The trim tab rear spar web is not quite as deep as it probably should be to avoid having this problem all together, and the note in their plans about the 1/4 inch measurement for the rivet holes is just wrong. Do you need to build a new trim tab? - HECK NO! You just need to measure and draw some new reference lines on both of the hinge halves using min edge distance of 3/16 from the outer edge of the flange, and adjust the fit of the hinge on the elevator side until the parts line up the way that they should. Mine came out fantastic with very minor deviations to edge distances. Will I check it during preflight and during condition inspections once I am flying - you bet I will.
My 2 cents.
