N546RV

N546RV

Well Known Member
So I started working on the trim tab last night. Drilled the control horn pieces, no problem. Then I got to the step of lining up the hinge with the top of the spar and drilling it, and I'm a bit unsure of how to proceed. It almost seems like it'd be easier if the spar wasn't prepunched...lining up three pieces, two of which have prepunched holes that need to be accurately aligned, seems ripe for error.

The plan I've come up with so far goes like this:
  • Lay out the elevator and trim tab, with the tab properly aligned
  • Use this setup to determine proper positioning of the hinge; mark the hinge alignment on both the tab and elevator
  • Drill a #40 hole at one end of the tab hinge half
  • Cleco through this hole and the first hole in the tab spar/skin
  • Now it should be significantly easier to align the hinge, spar, and skin on the other end of the tab; do this and clamp in place
  • Drill the rest of the holes, clecoing as I go
  • Finally, go back and final drill that first hole

I kind of feel like I'm overthinking this...what did you guys do? Just clamp the stupid thing together and drill, without all my complications?

:)
 
Ditto.....

.....what Aaron said about sacrificing some edge distance on the elevator side of the hinge in order to get everything to line up the way I wanted it. Hopefully this post in my log details all the steps I went through regarding the trim tab hinge alignment process.

I think I drilled the holes on the trim tab side of the hinge using the centerline I drew as shown in the comments of this next post:
marking trim tab rivet lines on hinge

Note my comments about the 1/4 inch measurement in the plans vs. "real" edge distance, and how I resolved that. Then when it came time to fit the trim tab to the elevator, I had to trim a small amount of hinge on the elevator side so that the trim tab would line up correctly. It wasn't much, and only impacted the area for the last 2 rivets on the outboard side of the hinge, but it was necessary.
 
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I don't have the plans in front of me, but I started with the trim tab. I seem to remember using a measurement off the plans that show where the hinge should terminate on the outboard side of the trim tab. I measured that distance and marked a line. I then measured 6/32 from the straight side of the hinge at several points along that half of the hinge. I drew a line through all those so that I had a 6/32 line (from the straight side) all the way down the hinge. I clamped the hinge half on the tab with the edge of the hinge at the terminating line that I had drawn. With my 6/32 line on the hinge centered in the holes of the trim tab and spar, I drilled and clecoed.

I drew the same 6/32 line on the elevator side hinge, attached it with the hinge pin to the trim tab hinge, set the tab to the elevator the way it should fit, and lined up the line on the hinge in the holes on the elevator. I made a mark on the 6/32 line at the outboardmost hole. Took the whole thing off and punched and drilled that outboardmost hole in the hinge. After that you can cleco that hole, clamp the inboard side and match drill the rest of the holes along the 6/32 line. Worked like a charm for me. Hope this is not too long and confusing.
 
Looked at my plans and found that measurement. It shows the trim tab hinge edge at 3/8 inch from the outboardmost hole, measured toward outboard on the trim tab.
 
3 pieces

I'm not sure if this is helpful as I don't remember exactly how I aligned and drilled the hinge on the tab.

When hanging the flaps we have the same scenario you describe. The there are two plies which are pre-punched and the hinge is not. To keep the two pre-punched plies in correct alignment but allow the hinge to lay flat on against the bottom side I squeezed some number 3 rivets just enough that I had an interference fit in the hole. I inserted them with small vice grips thru both pre-punched holes in the skins until flush with the bottom ply. They held the skins in tight contact and alignment, yet allowed the hinge to lay flat on the bottom ply.

Edit: Changed rivet size to number 3. Previously referenced wrong rivet size.
 
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DaAV8R said:
I'm not sure if this is helpful as I don't remember exactly how I aligned and drilled the hinge on the tab.

When hanging the flaps we have the same scenario you describe. The there are two plies which are pre-punched and the hinge is not. To keep the two pre-punched plies in correct alignment but allow the hinge to lay flat on against the bottom side I squeezed some number 4 rivets just enough that I had an interference fit in the hole. I inserted them with small vice grips thru both pre-punched holes in the skins until flush with the bottom ply. They held the skins in tight contact and alignment, yet allowed the hinge to lay flat on the bottom ply.
Click to expand...

Good tip...I had thought of doing something similar to this, using a rivet for alignment while I lined everything up, though I hadn't worked it to anything resembling a useful process.

I'll probably be giving it a whirl tonight. Got to finish riveting the elevator together first, then I can move on the figuring out the alignment and all the other fun stuff. I'll report back with results.

:)
 
Thanks so much!!

I used both of your tips and I really appreciate the insight! I think the hinge is right on...but I will have to wait and will know for sure, when the elevator and trim tab are married... :)

But I will say that it took me a long time to find 6/32" on my electronic caliper ... I mean, it took me forever :D

Good question - Philip!


KMinor said:
I don't have the plans in front of me, but I started with the trim tab. I seem to remember using a measurement off the plans that show where the hinge should terminate on the outboard side of the trim tab. I measured that distance and marked a line. I then measured 6/32 from the straight side of the hinge at several points along that half of the hinge. I drew a line through all those so that I had a 6/32 line (from the straight side) all the way down the hinge. I clamped the hinge half on the tab with the edge of the hinge at the terminating line that I had drawn. With my 6/32 line on the hinge centered in the holes of the trim tab and spar, I drilled and clecoed.

I drew the same 6/32 line on the elevator side hinge, attached it with the hinge pin to the trim tab hinge, set the tab to the elevator the way it should fit, and lined up the line on the hinge in the holes on the elevator. I made a mark on the 6/32 line at the outboardmost hole. Took the whole thing off and punched and drilled that outboardmost hole in the hinge. After that you can cleco that hole, clamp the inboard side and match drill the rest of the holes along the 6/32 line. Worked like a charm for me. Hope this is not too long and confusing.
Click to expand...


DaAV8R said:
I'm not sure if this is helpful as I don't remember exactly how I aligned and drilled the hinge on the tab.

When hanging the flaps we have the same scenario you describe. The there are two plies which are pre-punched and the hinge is not. To keep the two pre-punched plies in correct alignment but allow the hinge to lay flat on against the bottom side I squeezed some number 3 rivets just enough that I had an interference fit in the hole. I inserted them with small vice grips thru both pre-punched holes in the skins until flush with the bottom ply. They held the skins in tight contact and alignment, yet allowed the hinge to lay flat on the bottom ply.
Click to expand...
 
But I will say that it took me a long time to find 6/32" on my electronic caliper ... I mean, it took me forever :D
Click to expand...

Oh yeah, I guess I meant 3/16! I read so many measurements in 32nds before I did this, then stared at the 32nd side of my machinist rule for so long, that I couldn't think in terms of reduced fractions!
 
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