Mounting the Trim Tab Servo

Since my rudder trailing edge is still curing, I decided to work on the last remaining task left on the empennage: Mounting the trim tab servo.  I started out the work tonight by wiring up the servo, its indicator and switch to my 12V bench power supply to test its function and make sure it was in the neutral / take-off position.   I have a pretty good background with low voltage and electronics, so this was pretty fun for me.  After a little fiddling, I managed to get the servo working, and the indicator showing its true position.  I made sure it was in the neutral spot before un-wiring the servo to install it in the elevator. Here’s a video of it on the bench.

I mounted the servo to it brackets on the E-616-PP plate, and then inserted it in the left elevator so that I could cut the jack screw to the proper length.  The kit ships with a 7″ jack screw, which is WAY longer than you need.  I made sure my trim tab was in complete alignment and in trail with the elevator by using a long peice of angle stock, a block of wood and a small clamp with very light pressure.

Now that the trim tab was lined up in the take-off / neutral position, it matched the position of the trim tab servo.  You can see in the photo above just how long the jack screw is.  I used a ruler to measure from the middle of the clevis pin attachments on both the trim tab and the servo and came up with just about 3.5″ inches in length.  I used a hacksaw with a metal cutting blade, and a clamped the jack screw to my bench and made the cut.

After I cleaned up the threads on the cut end, I threaded the jack screw into the clevis pin attachments and adjusted the length so that it aligned perfectly.  Now I have my measurement, I use the jam nuts to lock the clevis pin attachments into place so I could continue working.  I then re-wired the servo so I could move it across its entire range and mark where  I needed to trim the skin.  Van’s mentions in the plans, that its OK to trim the elevator skin to allow for proper clearance of the jack screw.  I had to trim a decent amount to keep the jack screw from contacting.  I used a combination of tin snips, files and scotchbrite pads to get it roughed into shape.

Once I had the skin trimmed to where I wanted it, I ran the servo through its entire range of motion to check for binding and clearance.  I also checked the maximum angle of deflection using a protractor and angle finder and I have right about 25 degrees of up and down max deflection.  This is right at the lower bounds of what Van’s recommends for the maximums (25 – 35 degrees).   I left plenty of room for adjustment in the jack screw, but I am not sure if I have any room due to clearances if I need more travel.  I honestly think since I am at the lower end of the maximum range, I will be fine. This is a very big trim tab, and 25 degrees is a sizable deflection.  The important part was that when the indicator is indicating neutral / take-off position, the trim tab should be completely in trail and aligned with the rest of the elevator.  My trim tab hit this perfectly:

With the skin trimmed out, and the servo able to move through its range with no binding, all that was left is to clean up the edges.  I used a file to smooth all my cuts, round out the corners, and followed it all up with a good buffing with a scotchbrite pad and then vacuumed all the shavings out.  I removed the servo and stored it in its box, and I also took the trim tab off the elevator.  I am planning to store these separate to avoid them getting damaged. I think I might end up making some sort of shelves or hangers in the rafters of my basement/shop to keep my empennage parts up and out of the way.  That finished up tonights work session.  Roughly 3 hours spent total, most of that was trimming the skin and finishing those edges.  Here is the full photo album:

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Hours Worked: 3

Closing up the Trim Tab

I am coming down to the finish line on this empennage kit.  Tonight I finished up with the elevator trim tab, and it is ready to be permanently attached.  I had gotten it nearly completed the last time I worked on it, but I needed to get the elevator riveted up so I’d have a finished surface to work with.  I started out the night by getting the trim tab lined up with the elevator.  The trailing edge is critical, and needs to be perfectly in trail with the elevator trailing edge.  Luckily, I had an easy way to make sure of this.  I had some left over 2×2 angle, so I laid one side of the angle under the elevator, and let the other side function as my straight edge.  I made sure the angle was sitting flush up against the trailing edge, and then I positioned the trim tab so that its trailing edge also fit flush against the angle.  This made sure that both trailing edges were perfectly in alignment.


Once I was happy that the trailing edge was flush, I double checked the edges on the inboard edges as well, to make sure they are aligned together. Then it was time to clamp it all down and get to match drilling.  I used a cleco side clamp to hold it, while I drilled the first hole on the inboard edge.  Then I cleco’d that hole and re-checked my alignment and drilled the outboard hole which held the E-721 trim tab hinge from loosing its alignment.

Then I removed the trim tab, but left the forward half of the trim tab hinge clecoed to the elevator. I used all of my cleco clamps to help hold the hinge flush against the E-616PP spar. This also helped hold the hinge steady while I gently match drilled the remaining holes, using the E-701 as a guide.

After I got the forward hinge drilled to the elevator, I removed everything, and then deburred all the holes, and cleaned up the edges of the hinge, rounding the corners.  The plans also has us mark and trim off the excess hinge from the inboard side, which was easy to complete. I dressed these edges as well.  Next up was to rivet the hinge to the trim tab itself.  I had triple checked that everything was still in alignment with the tab on the elevator, and then I drilled the holes for the end tabs on the inboard side of the trim tab, using a #40, followed by a #30 for final size.  I clecoed those holes and then removed the trim tab to rivet everything.  I riveted the trim tab hinge using my squeezer making sure I did not catch the loops of the hinge in the squeezer.  Riveting this hinge cause a slight bend in the loops, so I spent some time gently bending the loops back into alignment, using the hinge pin to make sure.  With that being done, I drilled the outboard end tabs and then used CS4-4 blind rivets to finish up both sides of the end tabs.  With that, the trim tab is done!

Here’s all the photos for tonights session:

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Hours Worked: 2.5

Riveting the Trim Tab

After having a lot of things going on today, I decided to get down to the shop and build a little on the airplane to help clear my mind. Our little 9 month old, Acacia, had to be put in a brace for her hip dysplasia for a few weeks, so that broke mine and Tammys hearts 🙁   Getting down in the shop and working on the plane and working with my hands is a good stress reliever for me so I figured I’d go do some build-therapy for a few hours tonight.

Since I am waiting on a good full day to prime the rest of the elevator parts, the only thing I have left to work on right now is the trim tab.  I had previously assembled it, so I started this session by deburring all the trim tab parts, and dressing the edges of all the parts.  Then I dimpled the skin using my squeezer, because the tight spaces wouldn’t allow it in my DRDT-2.

The E-607PP trim tab spar needs to be machine countersunk only on the top side so it can receive the dimpled skin, but we can’t dimple it because we don’t want a bulge on the bottom, where the hinge will attach.  I fired up my micro-stop countersink and knocked this out pretty easily, and then followed it up by dimpling the bottom of the spar with my dimpler per the plans.

After all the parts were deburred, dimpled, dressed and countersunk, I went ahead and assembled everything to start riveting. I riveted on the bottom side of the skin to the spar using my squeezer, but this was not a fast process.  I had to use a few blocks of scrap wood to hold the skin open in order to get my squeezer in there.  It was still a tight fit in most of the spots, so I had to pay extra attention to what I was doing.

I left the E-717 and E718 trim tab horns for the very last so I did’t risk bending or damaging them during this process.  I also used a cleco to help hold the hole for the clevis pin in alignment on the trim tab horns just to be safe.  With a little bit of patience and fiddling, the bottom of the skin was riveted onto the spar.

I am going to hold off on attaching the top part of the skin to the spar, because we have to do some measuring of the trim tab against the elevator in order to align both halves of the hinge just right, so for now, I just clecoed it on and then attached the forward half of the hinge to keep the hinge pin safe and free from getting bent on the shelf.  That’s about all I got done tonight.  A total of right at 2 hours of work and I called it a night.  Here’s the photos from tonights session:

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Hours Worked: 2

Building the Trim Tab

I started this session by first dressing the edges of the left elevator skeleton parts, but that only took about 30 minutes, so I decided to find something else to work on.  Since those parts are waiting on priming, the only thing I have left to start on is the trim tab.  I read the plans and decided to give it a go and try to get the end tabs bent, and some work done of the trim tab itself. I managed to almost finish the trim tab assembly tonight 🙂

After dressing up the edges of those left elevator parts, I laid them up on the shelf and dug out the trim tab parts.  First we have to start off by bending the trailing edge of the skin for the trim tab, and this is done exactly like the elevators.  So I set up my bending brake  and put a very smooth and gradual bend on the trailing edge, and made sure it was straight with the spar in place.

Granted, I took my time on this, I got it done in about 20 minutes or so.  I have been reading up on bending these tabs for a while now, and watched the Orndorff videos, so I was pretty prepared to begin.  I started out by making some bending blocks that fit into the end of the trim tab.  I used the tab itself to draw an outline on a piece of 2×4 and then cut the shape out on my bandsaw.  I made two sets because the bends on each end are at slightly different angles.

With the bending blocks made up, its time to get to bending the trim tab! I start out by inserting the blocks and clamping everything down to my work table nice and tight so it doesn’t move during bending.

We start out by bending the bottom tab first, and overlapping it with the top tab, so that the top tab folds over the bottom, helping to keep water and debris from getting into the trim tab.   I used a block of wood in my hand to get the bend started and once I had it at about a 45 degree angle, I use a small hammer against my wood block to help shape the metal.  This way, I am using the soft face of my wood block against my tab and the bending block instead of the hard metal face of the hammer.  This keeps from dinging, denting and scuffing the aluminum.  I took lots of time and did this very slowly, using small light taps with the hammer against my block to bend the metal.  Once I had the bottom tab bent up to a 90 degree bend, I did the exact same to the top tab, bending it to overlap the bottom.   I am really happy with the results.

Now that we have the inboard side of the trim tab bent, it time to move to the outboard.  These tabs are MUCH smaller than the inboard side, so I had to take extra caution on these little suckers.  They would be easy to crack if you work the metal to much.  Eventually, I got them folded up, overlapping the bottom tab with the top just like on the other side.  I stuck the spar into the trim tab and clecoed it in a few spots to check my work, and I am happy with how it turned out!

Outboard Tabs

Inboard Tabs

After having a good victory on the tab bending, I still felt good enough to continue on working. The plans have us mount the E-717 and E-718 trim tab horns to the bottom of the trim tab.  E-717 has 3 of the 4 holes pre-drilled, so its easy to line up.  Then I just clamped E-718 to E-717 with some side clamps, and then use one of the clevis pins and hinges from my electric trim kit to make sure the holes were lined up properly in the trim tab horns.  Once everything was lined up, I back drilled both of the trim tab horns to the trim tab.

So, next up was to fully cleco on the spar, and then attach the hinge bracket so it can be back drilled.  I studied the plans and made a few alignment marks on my E-721 trim tab hinge.  Vans gives the measurements to the center of the hole in the skin/spar so its easy to mark the hinge with a sharpie, and then line up the cross hairs with the center of the hole.  I also marked the entire centerline of the hinge to the measurements Vans gives with a sharpie so I could align every single hole.  Once I had them all aligned, I used some cleco side clamps to hold it all together.  Once I had the hinge clamped on firmly, I started back drilling using the holes in the E-619-PP trim tab skin as my guides.

Once I had the hinge back drilled, I flipped the trim tab over and match drilled all the holes on the bottom to the spar.  Now, the plans has us disassemble the trim tab, so that we can trim off any excess from the trim tab horns, as well as the excess from the inboard side of he E-721 hinge.  I went ahead and trimmed off the very little bit of excess on the E-718 and E-717 trim tab horns, and smoothed the edges with a scotchbrite pad, and then did the same to the little bit of excess on the E-721 hinge.  I figured this was a good place to stop, so I called it a night.  I still need to deburr the holes, dress the edges of the trim tab parts and then dimple it all.  I am contemplating if I should prime the trim tab or not, not sure yet.  Here’s all the photos I took tonight:

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Hours Worked: 4

Assembling the Trim Servo and Deburring Parts

I got to do some pretty neat assembly work tonight, working with actual aircraft components, instead of just aluminum!  I worked on assembling the mounting brackets for the Ray Allan Electric Trim servo. I also deburred all of the metal parts for the left elevator skeleton.  The work session started out by unboxing the electric trim servo.  Van’s ships this assembly as an option for the RV-7, and they include all the mounting brackets, screws, nutplates, rivets and hardware thats needed to fully install it.  Another testament to how well Van’s build their kits!

I started out by studying the plans to note the proper orientation of all the parts.  There are quite a few custom bent brackets and they need to be lined up just right in order to drill the holes correctly.  The plans gives us some measurements to place the EET-602B-L mounting bracket.  I decided to mount the E-616PP cover plate to the skin so I could draw an outline of where the ribs and skin lay on the cover plate.  This will keep me from mounting the brackets to close and causing interference, and I also made sure to notate the orientation of the plate in reference to the aircraft as well.  Once I had that all marked up, I used a straight edge to mark lines on where the plans tells us the forward edge and inboard edges of the EET-602B-L bracket. Then I placed the servo bracket on the plate, using my lines as a guide and clamped it on with cleco side clamps.  Once I verified that the bracket was where it needed to be, I drilled the holes and attached it with normal clecos.  Now that the hard one was done, I just stuck the servo in that bracket, and then placed the right side bracket and used the servo attaching bolts to hold it while I drew and measured its placement on the E-616PP plate.

When I was happy it was in the right spot, I removed the trim servo and match drilled the holes into the E-616PP plate using the bracket as my guide.  Stuck in some clecos, and made sure it all fit perfectly.

Happy with how the trim system went in, I decided to drill a 3/8 hole in the elevator spar, just above where the stock hole is.  I will use this 3/8 hole and a snap bushing to run the wiring for the servo, and the stock hole for the servo jack shaft.  This way, I don’t have any wearing or chaffing of the wiring, and there is less chance of the jack shaft binding on the wires.  This is a suggested procedure per Van’s.  You can see the smaller 3/8 hole just above the larger stock hole in the photo below:

Once that was all done, I decided to go ahead and deburr all the holes in my left elevator skeleton.  I spent about an hour or so doing this, and got all the parts deburred and ready for dressing the edges.  I will do that tomorrow night, and then these last few remaining parts will be ready for priming.

That was a good stopping point for the night, so I cleaned up the shop, swept up all the metal shavings and called it a night. Here is the full album of all the photos:

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Hours Worked: 2.25