Trim Tab - Riblets Rule!!!

[gpiney]

Well, I spent a good part of nearly two months 'looking' at the trim tab. I was deathly afraid of bending those tabs. I designed and built 4 different 'bending blocks', none of which was any good. I was dreading this job. Not to loose track of things, I just went on by working on the fuselage. About once a week I would re-visit the trim tab. That would amount to staring at it for 30-60 minutes then moving on. The other local -8 builder had done his with riblets. So yesterday I said to myself 'self, why don't you try fabricating riblets'. So I did. I went to Harbor Freight and bought one of their cheep $20 bending brakes. It is a POS but it works if you don't mind all the time it takes to set up a single bend. I cut the blanks out of .016 scrap that came in one of the bundles. The outboard rib took 2 tries and the inboard took 3 tries, but after 2.5 hours of not knowing what I was doing I had riblets that fit and looked good. I then did the brave move of cutting off the tabs. I then marked, punched and drilled the skin with the riblets clamped in place. I will dimple them when that time comes and use 426AD3-3's to hold them in place.

I'm a Happy Boy!

[osxuser]

Funny thing, I screwed up the tabs on the elevator, so I made the riblet to replace those tabs. Then I went on to bend the tabs on the trim tab, and it worked fine. Both solutions work great, I don't know why the tabs didn't work on the elevator skin, but I like that doing the riblet on that allowed me to buck the rivets on the rear spar of the elevator.

[sf3543]

I used riblets on both of my planes on the tab and on the elevator, but bonded them in with JB Weld. 900 hrs on one plane when sold and almost 200 hrs on the second with no problems. Just rough up the surfaces before bonding.
Good luck.

[jmartinez443]

I have absolutely no clue why Van isn't doing this instead of having you do the stupid bend. In case you don't feel like spending $$$ on a bending brake, I made mine out of end ribs I ordered from Van's. Here's how I did mine:
http://www.rv8alog.com/empennage/elevators/Left/e8.htm

[sf3543]

To form these small ribs, you can cut a piece of wood to the appropriate shape. Start the bends by laying the aluminum over the wood and bend the aluminum down over the sides enough to get bend line identified. You can either hammer them down from there or just take a pair of seamers and complete the bend. If you decide to hammer them, round off the wood edges to the appropriate radius.
The web of the rib, at the narrowest point, may not be perfectly flat and perpendicular to the flange, but that is ok.
The same piece of wood will work for all the ribs, just make it big enough for the largest rib.
Make the ribs longer than you need and cut them to the appropriate length after the flanges are bent.
You can also do this in a pan brake, but you will still need the seamers due to the narrow end of the riblet.
Good luck.

[Scott Will]

How I did mine... cut a small wood block to the correct shape. Inserted and clamped it all very well and then went at it like this...




Even though the pics are of the elevator, we did the same thing for the trim tab.

[Phil]

Scott,

I'm going to be facing that step soon. Just curious, were you able to slide the wood out?

[Scott Will]

Yeah... the wood is out. It's not coming along for the ride! Will let you know how it goes on my -10. The kit just arrived about an hour ago!

[G-force]

Similar to Scotts method, both my tab and elevator came out perfect. One thing to note is I did line the inner wood wedge with a sticky friction tape to lock it in place.

[jscottpilot]

could you post a picture of the riblet thing. Or pictures during assembly and after assembled. I will probably end up re doing my trim tab and maybe the elevator.