Post by wisconsinjoe on Sept 23, 2021 7:27:25 GMT -8
There are so many problems to solve in this hobby that wake me up in the middle of the night. Recently, I had to figure out a way to cut holes in the aluminum skin to match the exact places where I had wires protruding for exterior mounted lights. The solution is using templates.
I had created two separate ones to locate the places to run marker lights for the front and rear, used on both curb and street side. Because I had the original full size template from which the walls were built, I had a reference to trace the exact curves that lined up with the roof framing that was visible. Some scrap plywood quickly turned into these templates. I used them originally to set the placement of the wire holes, and saved them for the skin placement. I drilled ½” holes to run the wires through the ¾” plywood set flush with my 1-½” deep wall framing. Once my skins were solidly attached at the bottom, but not the top, I clamped the template in place, carefully re-registering to the same marks. A sharpie then marked the holes.
BTW, a good reason NOT to glue in your insulation is that by removing it you can more easily clamp skins on (or template in this case) for tracing the profile curves to be cut.
20210904_111341 by Joe Mirenna, on Flickr
20210904_131455 by Joe Mirenna, on Flickr
Not wanting to damage the protruding wires, I slipped a scrap piece of ¾” plywood between the aluminum skin and wall framing and punched the center of the marked hole. Then I used a ⅝” spade bit to drill the hole. I wanted to have a hole slightly larger than my wood framing hole because I feared wire being cut by the relatively sharp aluminum vibrating while traveling. Once the hole was cut, I filed the edge to remove any sharpness. Now, the skin was ready to pull the wires through and fasten permanently. That plastic was there to catch the tiny disk of metal cut from the hole in case it fell off the bit between the skin and framing.
20210904_132805 by Joe Mirenna, on Flickr
20210904_132736 by Joe Mirenna, on Flickr
20210904_133432 by Joe Mirenna, on Flickr
I had a more challenging situation at the rear where I had two large holes for the tail lights and another small hole for the license plate. With careful measurements I made another template from scrap ¼” plywood. But, I was puzzling how to accurately register it to the body once the aluminum was attached. The solution was to pop rivet some scrap aluminum strips to the template and screw the upper ends to roof framing that would not be covered by the lower section of skin that covered the light holes. I made sure the template holes were perfectly aligned with the camper holes. It helped that the scrap aluminum had a strong curve from the original roll, making it lay flat against the curve. That same thing helped when the roof got attached later.
20210908_141038 by Joe Mirenna, on Flickr
20210908_120500 by Joe Mirenna, on Flickr
Once that was attached I slid the skin between the template and framing, keeping about ⅝” proud on one side (...later marking the same overlap on the opposite side for trimming just one side). I pulled the skin tight against the curve with 4 sets of straps that ran completely around the camper. That worked amazingly well.
With the template in place, a sharpie marked the holes. Using the same practice of accurately marking and punching the centers and placing scrap wood beneath to bear the drill bit, the holes were cut in the aluminum. Best to drill a small pilot hole to register the rather cumbersome hole saw. I marked that by using a compass to draw a comparable circle, thus finding my exact center, and then taping the cardboard cutout over the sharpie marked circle.
20210908_131047 by Joe Mirenna, on Flickr
20210908_135809 by Joe Mirenna, on Flickr
The only difference was that with the large 4-½” tail light holes, I used a 4-¼” hole saw. I wasn’t worried about wires rubbing on sharp edges. Rather, I worried about the accuracy of my template. Sure enough, I was off by just a smidge, but since the hole was smaller than I needed I was able to trim it correctly using a trim bit in a small router. This seemed to work harder than I expected. If I was taking off more than ⅛” of this thick 40 mil aluminum, it seemed to gum up the bit with melted metal. That easily broke off the bit with a light pry of the punch. Nevertheless, all my holes were cut and perfectly aligned.
BTW, be careful using a hole saw. At one point of cutting only partially through the aluminum, the bit grabbed while the hand held drill violently twisted in my hand. It banged against a thumbnail (...ouch) and literally threw me backward. I landed outside the tarp on the shed. I quickly learned to slowly rock the hole saw in a circular motion to cut the aluminum along one part of the circle at a time.
I used a similar take to accurately place the two rectangular cut outs for the fridge vents and the circular electrical connector hole. There I was able to screw the plywood template to exposed framing above the lower piece of skin which went on first. Of course the window cut outs were easy because there was interior access from which I could drill corner registration holes, match up on the outside for drawn lines, staple securely to the frame, mask the edging (... avoid tool marks), and cut out with a jigsaw.
I slept better that night.
I had created two separate ones to locate the places to run marker lights for the front and rear, used on both curb and street side. Because I had the original full size template from which the walls were built, I had a reference to trace the exact curves that lined up with the roof framing that was visible. Some scrap plywood quickly turned into these templates. I used them originally to set the placement of the wire holes, and saved them for the skin placement. I drilled ½” holes to run the wires through the ¾” plywood set flush with my 1-½” deep wall framing. Once my skins were solidly attached at the bottom, but not the top, I clamped the template in place, carefully re-registering to the same marks. A sharpie then marked the holes.
BTW, a good reason NOT to glue in your insulation is that by removing it you can more easily clamp skins on (or template in this case) for tracing the profile curves to be cut.
20210904_111341 by Joe Mirenna, on Flickr20210904_131455 by Joe Mirenna, on FlickrNot wanting to damage the protruding wires, I slipped a scrap piece of ¾” plywood between the aluminum skin and wall framing and punched the center of the marked hole. Then I used a ⅝” spade bit to drill the hole. I wanted to have a hole slightly larger than my wood framing hole because I feared wire being cut by the relatively sharp aluminum vibrating while traveling. Once the hole was cut, I filed the edge to remove any sharpness. Now, the skin was ready to pull the wires through and fasten permanently. That plastic was there to catch the tiny disk of metal cut from the hole in case it fell off the bit between the skin and framing.
20210904_132805 by Joe Mirenna, on Flickr20210904_132736 by Joe Mirenna, on Flickr20210904_133432 by Joe Mirenna, on FlickrI had a more challenging situation at the rear where I had two large holes for the tail lights and another small hole for the license plate. With careful measurements I made another template from scrap ¼” plywood. But, I was puzzling how to accurately register it to the body once the aluminum was attached. The solution was to pop rivet some scrap aluminum strips to the template and screw the upper ends to roof framing that would not be covered by the lower section of skin that covered the light holes. I made sure the template holes were perfectly aligned with the camper holes. It helped that the scrap aluminum had a strong curve from the original roll, making it lay flat against the curve. That same thing helped when the roof got attached later.
20210908_141038 by Joe Mirenna, on Flickr20210908_120500 by Joe Mirenna, on FlickrOnce that was attached I slid the skin between the template and framing, keeping about ⅝” proud on one side (...later marking the same overlap on the opposite side for trimming just one side). I pulled the skin tight against the curve with 4 sets of straps that ran completely around the camper. That worked amazingly well.
With the template in place, a sharpie marked the holes. Using the same practice of accurately marking and punching the centers and placing scrap wood beneath to bear the drill bit, the holes were cut in the aluminum. Best to drill a small pilot hole to register the rather cumbersome hole saw. I marked that by using a compass to draw a comparable circle, thus finding my exact center, and then taping the cardboard cutout over the sharpie marked circle.
20210908_131047 by Joe Mirenna, on Flickr20210908_135809 by Joe Mirenna, on FlickrThe only difference was that with the large 4-½” tail light holes, I used a 4-¼” hole saw. I wasn’t worried about wires rubbing on sharp edges. Rather, I worried about the accuracy of my template. Sure enough, I was off by just a smidge, but since the hole was smaller than I needed I was able to trim it correctly using a trim bit in a small router. This seemed to work harder than I expected. If I was taking off more than ⅛” of this thick 40 mil aluminum, it seemed to gum up the bit with melted metal. That easily broke off the bit with a light pry of the punch. Nevertheless, all my holes were cut and perfectly aligned.
BTW, be careful using a hole saw. At one point of cutting only partially through the aluminum, the bit grabbed while the hand held drill violently twisted in my hand. It banged against a thumbnail (...ouch) and literally threw me backward. I landed outside the tarp on the shed. I quickly learned to slowly rock the hole saw in a circular motion to cut the aluminum along one part of the circle at a time.
I used a similar take to accurately place the two rectangular cut outs for the fridge vents and the circular electrical connector hole. There I was able to screw the plywood template to exposed framing above the lower piece of skin which went on first. Of course the window cut outs were easy because there was interior access from which I could drill corner registration holes, match up on the outside for drawn lines, staple securely to the frame, mask the edging (... avoid tool marks), and cut out with a jigsaw.
I slept better that night.
