Trim Tabs

james gevay · Post by **james gevay** » Mon Mar 31, 2008 16:14

I need to build a new elevator trim tab because of some small dents and cracks in the one off my 7AC. The picture shows whats inside the tab on an Aeronca.

The hinge is anodized aluminum, .047 thick by 25". The tab as close as I can measure it is .020 and the green doubler is .040. The tapered phenolic block on the end has 3 different lengths of rivets, although I've seen screws on other planes. Two fillister head screws hold the belcrank on the end.

Questions, the hinge was riveted to the tab with 10 steel rivets that had about 1/16th dimples on the shop head, listed as AN465-AD3-4.

Can I substitute AN470AD3-4's or is there a reason they have to be steel? The hinge is listed as NAS 40-4A-TT-25 and NAS 40-4A-LL-25, the 2 halves.

Which should I order from Aircraft Spruce, the MS20257P or the MS20001P and whats the difference in this application.

Thanks, Jim

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Dennis · Post by **Dennis** » Mon Mar 31, 2008 19:23

"The tapered phenolic block on the end has 3 different lengths of rivets, although I've seen screws on other planes."

I made an aluminum block to replace the phenolic block.

Dennis

Nathan K. Hammond · Post by **Nathan K. Hammond** » Mon Mar 31, 2008 22:46

The difference in the hinge is how it's made. 20257P is machined to be a hinge and can pull apart. 20001P is extruded, so the only way it comes apart is by pulling out the pin.

As for the rivets, I'm not sure. But you'd think aluminum rivets would be preffered so there wasn't disimilar corrosion. I don't see any reason not to use them.

nkh

Paul Agaliotis · Post by **Paul Agaliotis** » Tue Apr 01, 2008 08:08

Jim,
You might check with ACA. The 7ECA tab might work.
Paul

Jimmy Payne · Post by **Jimmy Payne** » Tue Apr 01, 2008 08:22

Jim,

The AN465 is the head style of the rivet. Are you sure it is not AN455 or AN456? They are both Brazier Head rivets which have a lower profile than the standard universal head rivets in use today. You may want to check for clearance problems between the trim tab and elevator. I can't find any info on the AN465.

The -AD3-4 tells me it is an aluminum rivet.

I am getting this info from the Standard Aircraft Handbook 4th ed.

james gevay · Post by **james gevay** » Tue Apr 01, 2008 10:18

Yes your correct on the rivets, they are AN456 not AN465, I transposed the number incorrectly. I got the numbers straight out of my Champ service manual.

The factory head looks normal but the shop or driven side has a large dimple in it, not like you normally have after driving it, and their steel. I wasn't sure if because it came off a moveable control surface they had to be steel rivets or not.

I know that Wag Aero has the trim tab for sale but I want make my own for the learning experience and the cost. I only want to replace the hinge and the aluminum skin.

I think anyone who has bent up a RV rudder or elevator could help me with the bending part. Nathan, thanks for the drawings, sometimes a picture helps describe a part better thar whats in the catalog.

The hinge that came out of the elevator was the extruded kind and that's the kind I'll order.

Jim