Having rolled the rudder leading edges a while back, I was never really comfortable with the process of duct taping a 1.25" diameter wooden dowel to the leading edge, and using vice grip pliers to roll the sheet metal around the dowel.
There were several issues that I fought with while using this process
- As the initial rolling with the vice grips progresses, it becomes increasingly more difficult hold the dowel against the workbench
- Adjusting the vice grips to add additional roll is impossible using just one pair of vise grips, and difficult at best with a pair of vise grips at each end of the dowel, as the dowel wants to lift as soon as you loosen the vise grips
- It is difficult to obtain the maximum amount of roll because the vise grips tend to hit the spar first as the roll progresses. Due to this, more hand rolling is then required.
- Hand rolling tends to form waves in the rolled skin due to uneven hand pressure. I also found it difficult to get the rolled skins to come together enough so that clecoes could be inserted with little additional rolling force. Part of this was due to being nervous about over squeezing and deforming the skin while hand rolling
I had started rolling the elevator skins using the same techniques I had used on the rudder, but quickly encountered the same issues.This made me stop and think as to how rolling the leading edges could be turned into a more predictable and repeatable process, minimizing the need to hand bend and the inherent risks associated with deforming the skins by applying too much pressure in the wrong places.
I researched the various forums to see what other techniques builders had used to roll leading edges on their control surfaces, and after some experimenting of my own (using scrapped skins), I landed on a process that works extremely well by
- making the initial roll incredibly simple, and repeatable with minimal effort
- allowing the initial roll to be performed across all skin sections at once (if desired), rather than one section at a time
- maximizing the amount of initial roll, thereby minimizing the amount of hand rolling required
- having less hand rolling, thereby minimizing any waviness in the roll, while making it easier to hand roll the skins to where they virtually touch
- requiring just a minimal amount of additional force to line up the rolled edge holes and insert clecos
I take no credit for coming up with the techniques that I am about to describe in detail. They were all gathered from online Van's RV builder forums and blogs, and I'll link to the relevant threads below. However, I do document my experiences and learnings with the different processes, in the hope that it may help other builders that are struggling with rolling leading edges as I did.
In order to experiment with the different rolling techniques, I had to have some scrap sheet metal to roll. It turns out I had some discarded trim tab skins that I had previously used to practice tab bending, and these were perfect for this purpose.
I started by cutting the trim tab skin in half along the trailing edge, and then cutting off the 4 end tabs. I then trimmed the remaining skin to the length of the longest section of the elevator leading edge (to simulate rolling the elevator leading edge as closely as possible). Finally, I marked the skin at 1/2" intervals to be able to easily measure exactly where the bend formed during rolling.
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| Test piece cut and marked, ready to be rolled |
One very useful
thread I found on VansAirForce.net mentioned a couple of different approaches to rolling the leading edges.
The first of these techniques that I tried was to zip tie two 1.25" diameter dowels together and insert the test piece between them. I then used channel lock pliers to grip both dowels at the ends, and rotated to roll the skin between the dowels.
While this worked to introduce a roll, I ran into many of the same issues I had encountered while using duct tape and vise grip pliers. I had to apply increasing downward pressure as the roll progressed, and I had to be very careful to not allow the skin to move around between the dowels which it was prone to do.
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| Rolling the skin between two zip-tied dowels. I used a level to clamp down the skin to the workbench while rolling, but if doing this on an elevator, an alternative method of securing it would be necessary |
Moving on to another technique discussed in the forum thread, I purchased a 1.25" closet rod, a couple of 7/8" sockets and 3/8" ratchets, and assembled the rolling tool shown below.
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| Rolling tool using ratchets for leverage. The sockets were secured in the closet rod using JB-Weld |
Taking a fresh test piece, and securing it to the workbench using a level and clamps, I duct taped the edge to this rolling tool, and used the ratchets to roll the sheet over.
Because of the leverage of the ratchets, and the fact that I could adjust the ratchet arm position without removing the ratchet from the socket, rolling was relatively easy, and I was able to roll the edge right over. However, I still had the issue of needing to apply a lot of downforce while rolling to stop the skin lifting.
This tool, however, was a definite improvement over the two previous techniques I had tried. I just had to find ways to
- make it easier to keep the skin against the workbench while rolling
- prevent the piece from moving while rolling (in this case the elevator or rudder)
Searching the forums again led me to
another thread on rolling leading edges that described a tool very similar to the one above, but used hooks to keep the tool and skin against the workbench while rolling. So I figured I would try this, and purchased the following items
- 2 U-bolts (from which I could make J-hooks)
- 2 large washers (to help secure the J-hooks against the bottom surface of the workbench top)
- 6ft 1.25" diameter closet rod (to make a longer rolling tool that could span the entire length of the elevator or rudder)
- 1socket - 7/8" diameter
I first had to convert the U-bolts into J-hooks by removing one of the threaded portions on each U-bolt. I did this by clamping the bolt in the vise, and using a Dremel with a cutoff wheel to grind through the bolt.
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| U-bolts converted into J-bolts |
I then placed one of the elevators onto the workbench with
- the leading edge lined up with the edge of the workbench, and
- the elevator horn hanging over the edge of the workbench with just enough space for the ratchet to rotate between the elevator horn and the workbench edge
I marked a hole location centered between each of the sections to be rolled (2 holes), as well as a third hole about 1" in from the edge of the workbench between the horn and inboard leading edge section. The three holes were also positioned about 1" aft from the workbench edge to which the leading edge skin was aligned with.
Next I drilled the holes to 5/16" which was just big enough to allow the J-bolt to pass through, and attached the bolts into two of the holes along with the large washer.
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| J-bolt attached to workbench with large washer beneath |
I assembled a new rolling tool in the same way as the previous one, but cut the closet rod so that it extended across all 3 sections of the elevator leading edge right up to the horn.
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| Longer rolling tool with socket welded into one end |
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| 3/8" ratchet attaches to socket to provide a secure mechanism for rotation |
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| Rolling tool clamped to workbench with J-hooks. Nuts on the J-hooks were tightened by hand. This picture was taken before I had drilled the third hole in the workbench to accommodate a J-hook near the far corner. |
I then proceeded with rolling of additional test pieces.
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| Test piece duct taped to rolling tool. Plastic sheet was place under the test piece because the test piece moves while being rolled (rather than the rolling rod moving). The plastic sheet helps prevent scratching of the work piece |
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| The first test roll using this technique turned out pretty well. The leading edge was rolled to a 45 degree angle (a height of about 1-5/16" above the work surface), and the roll was uniform along the length |
Because the hooks worked to keep the skin against the workbench, rolling this way was incredibly easy, being as simple as just turning the ratchet handle.
Based on measurements I took with the edges I had previously rolled on the rudder and elevator using just a dowel and duct tape, I calculated that the leading edge of the skin would need to sit at least 1-3/4" above the work surface after rolling in order to make lining up the holes for clecoing an easy task. So this meant that I would need to hand roll so that the edge gained another 7/16" (1-3/4" - 1-5/16") in height.
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| I flipped the test piece over and clamped it to the workbench at a position simulating where the spar would be, and then proceeded to add additional roll by hand |
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| Hand rolling to get an additional bend to increase the height of the leading edge to 1-3/4" above the work surface was not too bad. Some skin waviness was still introduced after hand rolling, but the apex of the bend was uniform along its length and I felt this would have been a satisfactory bend if done on an actual part |
Next I attempted another roll, but this time paid more attention to how far I could roll before the J-hooks reached the spar. I had marked the spar location on the test piece and carefully rolled until the piece moved under the pipe to a point where it looked as if the J-hooks would touch the spar (thereby preventing further rolling).
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| Ready to roll again paying attention to the spar location and interference with the J-hooks |
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| In every test case, the test piece was moved to a position so that the skin leading edge was lined up with a vertical tangent to the edge of the rod, and duct taped at that position prior to rolling. This is also illustrated in section 5.9 of the plans (image copied below) |
In this test I was able to roll the leading edge to a height of 1.5", just 1/4" shy of the desired 1-3/4", and this meant I only needed a small amount of hand rolling. At this point I also realized that I could trim back the J-hook a little to get additional roll while still maintaining effectiveness of the J-hooks in holding the skin down.
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| Second test piece rolled. I was again happy with the initial roll that got me very close to the desired final bend amount |
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| Roll was once again uniform along the length of the test piece and the apex of the bend was in a perfect location |
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| J-hool was trimmed back a little more so that it no longer extended beyond the rolling rod and permitted a small amount of additional rolling before reaching the spar |
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| Trimmed J-hook reattached. It still holds the rolling rod down securely but permits rolling until the rod itself contacts the spar |
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| I ran a final test piece through with the trimmed J-hooks and results were once again promising |
At this point I felt confident enough to try this rolling technique on the elevators themselves. Prior to that, I had to complete rolling of the leading edges that I had previously started in early 2023, and with some extremely careful and time consuming hand bending I was able to complete a satisfactory roll.
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| 2 leading edge sections rolled using previous techniques of rolling around a dowel followed by a lot of tediously slow hand bending |
Now it was time to attempt rolling the final section of this elevator leading edge using the hooks and rolling rod.
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| Duct tape placed under the leading edge, ready to have the rolling rod attached |
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| Elevator leading edge ready to roll. Here I used the shorter rolling rod as I had already rolled the other sections |
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| Turning the ratchet was relatively effortless with the J-hooks holding the rod down |
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| Initial leading edge roll done. I couldn't quite get as much bend as in the test pieces due to the rolling rod contacting the elevator horn before the spar |
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| Getting ready to roll the opposite leading edge section prior to any hand rolling |
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| With the placement of the elevator, I had enough space to rotate the ratchet freely between the workbench, elevator skin, and elevator horn |
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| Both skins sections rolled. The next step involves applying hand pressure to increase the bend and move the leading edges closer to each other |
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| Initial rolling of both leading edges was very consistent, with the location of the bend apex making it easier to hand roll |
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| Edges moving closer after a few minutes of had rolling |
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| All leading edge sections clecoed, with no pillowing between clecoes |
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| I was happy with how the clecoes lined up, and with how the bend turned out while keeping the elevator skins tight |
On the left elevator, I used the longer rolling rod to roll two leading edge sections at the same time. This worked out really well, and in hindsight I could probably have rolled all three sections together.
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| Two leading edge sections taped to rolling rod for simultaneous rolling |
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| The J-hooks did a perfect job of holding down the rolling rod while turning |
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| Rolling rod easily fits under the rolled edges, ready to roll the opposite leading edges |
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| While taping the leading edges to the rolling rod, I found it easier to start by attaching the tape along the entire edge near the base of the rod |
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| Rolling the opposite leading edge |
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| I used clean release duct tape which made it easy to detach from the leading edge with zero residual glue left behind |
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| After hand rolling, I was able to get the leading edges to almost touch |
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| Leading edges rolled to a height of 1-3/4" |
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| Smaller sections are easier to roll to the point where the skins touch or even overlap slightly |
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| Leading edge clecoed, with zero pillowing |
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| Center section leading edge hand-rolled to within clecoing distance |
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| Both sections clecoed with minimal additional force |
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| Uniform roll across both skins |
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| The last section to roll was the inboard left elevator leading edge for which I once again used the shorter rolling rod |
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| One thing to note is that for hand rolling I used grippy gloves to ensure the skin didn't slip while rolling. It also helped reduce scrapes and scratches on my hands while maneuvering the overlapping skins |
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| Left elevator leading edge rolled and clecoed |
The final step was to rivet the leading edge skins together. This was easily accomplished while taking care not to introduce any pillowing between the skins
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| Riveting the leading edge sections using a manual rivet puller |
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| Both elevator leading edges rolled and riveted... at last! |
