VAF Forums - Tip: Trim Tab II

Warning: Long on tongue-and-cheek commentary, short on meaningful content. :)

Let me start by saying that I am rather fastidious. I tend to obsess about small details and in my never ending quest for perfection, at the occasional expense of increased build time and $, I will choose to re-do something that doesn?t need re-doing. You must also know that as this is my first kit-plane and I am in no means an expert, and will not claim to be one. With all that in mind, let more offer an unsolicited tip to those builders just getting started.

Order two trim tabs from the start! That?s it, that?s my advice. Alright, I will explain.

I believe the task of bending the trim tab ends (and elevator tabs), in the desired locations, to be a task that while not incredibly difficult is easier and produces better results with the benefit of experience under your belt. The more builders I talk to the more I hear things like, ?It took me two (sometimes three) times to get it right?. Even the Van?s catalog quips about it not getting it right the first time. Sure, there are those that will boast about how they got it perfect the first time, and I am happy for them, really I am, but that wasn?t the case for me. My first attempt, while completely acceptable from a technical and safety perspective, left me with a gap between the tab and elevator tabs of inconsistent width, and a few dings in the end of the tabs (which could have been filled). Bottom line is, I just wasn?t happy with it. The locals (builders) told me I was nuts, and I tried real hard to convince myself it was good enough, but I found the desire to make it better too strong to overcome... In a moment of late night weakness, I broke and ordered a new tab.

The second tab is now complete (for the most part) and I am happy I chose to do this a second time. The results I was able to much more easily produce on what I will call ??Trim Tab II ? The Sequel? are superior to that of the first, simply because I had the benefit having practice. Therefore, at the expense of $15 or so, I propose you order a second trim tab skin before you start construction of your elevators. Try to get it right the first time, but treat the first one simply as practice. This will allow you to make adjustments to your forms and bend lines before starting the second tab. If the first one comes out great, you?ve just earned yourself a membership to the One-Tab-Club. If it doesn?t, there is no need to stress, just throw it in the scrap pile make your adjustments and start again. I think you will find the benefit of the experience to be well worth the $15 admission cost. In the event that you get it right the first time, you can always be another builder?s hero when you offer them your extra tab to replace the one they screwed up? just another benefit to being a member of the One-Tab-Club (along with a patch for your flight jacket). :D

Ok, a few tangible tips?

Before bending anything, including the elevator tabs, lay it all out. IIRC, the directions have you bending the elevator tabs before you even touch the trim tab. You may find that you have bent the elevator tabs too far inboard or outboard if you don?t think and plan ahead.
In my case, I found that lining up the rivets in the rear elevator spar with the rivets in the trim tab spar yielded the optimal alignment. Again, clamp, cleco, line-up, and adjust everything before making a single bend.
To smooth out the tabs and avoid dings don?t hit the tabs directly with the flush set, instead use something more forgiving like a piece of wood between the tab and the set. Making sure to turn your rivet gun way down to start (say 10psi), you can always turn it up if you aren?t getting the desired results.
If you are unhappy with the elevator tabs, consider cutting them off and fabricating a little rib. While not necessary, lots of other builder?s have done this to overcome their elevator tab issues, we just like to be referred to as elevator-tab-challenged. ;)
Last but not least, take your time and use a light touch.

Well this turned out to be about 10-times longer than I thought it would be, but I hope there is value here for somebody, if nothing else, a little entertainment value. As usual, these are just one man?s opinions, so YMMV. Good luck and happy bending! :)