Update: The weight of the rotopax plus the ladder and necessary strut support rating made this a fail for me. If you don’t have a ladder, this may work for you. For details: https://www.xterranation.org/index....ear-hatch-rear-gate-install.10105/post-526676
There are probably a couple approaches to getting a Rotopax mounted to the bump on the rear hatch (and I tried two different ones), and this is what seems to work better than I expected. First, finished photos (3 gallon pictured):
The biggest challenge to this is that the bump-out is entirely curved. I used (on my second attempt) the single mounting plate from Rotopax, which spread the bolts out to a larger area. There is more curve vertically than horizontally, which is why I mounted my plate this way so the longer distance between bolts was horizontal.
My original plan was to try to do a "flat" mount where I would use closed cell foam or thick rubber sheeting to act as a gap filler, but the sheet metal is so flimsy that it collapses before the rubber squeezes. Plan two was to get high-strength two-part urethane foam and use a plastic bag to mold it to the shape of the curve on the inside, which would theoretically allow me to use flat steel bars to hold it in place, and prevent the sheet metal from buckling to do foam/rubber on the outside. I'm pretty sure that would've worked as well.
What I ended up doing was using a series of washers to keep the flat parts "away" from the curved parts so they could stay straight and not buckle the metal.
Parts:
Rotopax single mounting plate with rotopax holder already attached
4x Grade 8 1/4" x 1 1/2" bolts
8x Grade 8 washers
4x Grade 8 lock nuts
4x 1/4" galvanized bonded sealing washers
4x small diameter stainless washers
4x large diameter stainless washers (I used 1 1/4")
4x small diameter rubber washers
4x large diameter rubber washers
1x 24" x 12" galvanized sheet metal
1x 3" x 3' steel bar (I did 3/16" thickness, you can also go wider)
1x 1" x 3' aluminum square tubing (you could do more steel, but I did this to keep weight down)
Scrap rubber sheets, or new sheets from the plumbing department. (Comes in 6" squares in 1/8" and 1/16" thickness)
RTV
Rustoleum or any protective paint
Here is a rough diagram done in powerpoint:
1. Take the rear panel off. There are two 7mm bolts behind the first aid kit, and two 10mm bolts in the handle under the covers. Then gently pull to release the clips.
2. Mark your drilling locations with masking tape and marker - this is easier with help. I aimed to have mine centered, but if you want to keep your Xterra badge on the rear you may have to adjust. I also used a level to verify my bumper and the floor were level, and made sure the mount was the same.
3. Double-check everything, then drill a small pilot hole, followed by 1/4" holes (the size of the stock hardware, and replacement hardware I bought).
4. Remove the tape and any burs, and apply a bit of paint to the bare metal to protect from rust.
5. Using cardboard or similar, figure out the largest you can cut your sheet metal, and trace where you have to cut tabs out to sit flat against the existing metal.
6. Apply pressure to the back of the sheet metal to match the curve of the hatch, and mark the four holes for drilling.
7. Drill out the sheet metal.
8. Put the bolts and washers through the four holes of the mounting plate, and slide on the bonding washers, which will keep your bolts from moving.
9. Place the four bolts through the holes in the hatch, put some RTV on the hatch for the sheet metal to grab to, and optionally put some on the inside of the bolt threads as well.
10. Put the sheet metal in place, and use washers and nuts (ideally regular nuts so you can spin them on easy) to hold the sheet metal to the hatch. Make sure you're not buckling anything.
11. Use cardboard or paper to see how long you can cut your steel bars so that they're vertical when the hatch is closed. Mark this, as well as the holes to drill using the bolts now in place for both sides. Important Note: the length will vary based on your placement, both proximity to supports and proximity to the curve of the hatch. The longer, the better for support, but too long and the end will be making contact with the metal and potentially buckle when you tighten down. I did about two inches above and below the bolts. If you're unsure, go ahead and stack all four washers in the diagram above, and make sure your ends don't contact the metal.
12. Cut your steel bars and drill them out.
13. Do the same measuring for the aluminum tubing horizontally, but they only need to bridge the steel bars to add rigidity. They may not even be entirely necessary, but I didn't want any doubt. For the square tubing, one side will be the 1/4" hole and the other side needs to be large enough to fit a socket head through (see pics below).
Assemble everything except rubber shims as shown in the diagram above. Be sure when you tighten, you criss-cross and do a little at a time. Go SLOW and watch for buckling. If there is any, you may consider doing an additional small rubber washer on the inside and/or outside.
14. Once tight, use rubber sheeting or scrap rubber as "shims" between the ends of the steel bars and the hatch. This will eliminate any last little bit of play the metal may have and tighten everything up nicely. To do this, I used a 1/8" piece about 3" square so it extended out past the steel, and then inserted a 1/16" thick piece as tight as I could get it between the hatch and steel bar. You might be tempted to put this in place before you tighten down the four nuts, but don't as I can tell you from experience it will end up creating a gap pulling the bar off the bolt's washers, and you'll add buckling. If you want it really tight, you can do the two different thicknesses, then use a thin fender washer to wedge in there as well to add tension. Do this for all four steel edges.
15. To cover sharp edges, clean everything up, help prevent vibration, and to make sure rubber shims didn't relocate, I added duct tape.
16. Put everything back together and admire!
In my case, with the hatch closed and I can yank on the extended part of the rotopax mount, and not only does the hatch and sheet metal not move at all, but the truck body moves slightly. It's extremely secure.
Here is a view from the side where I was making sure there was no buckling and checking to see that the bonding washers were tall enough to maintain a slight gap:
There are probably a couple approaches to getting a Rotopax mounted to the bump on the rear hatch (and I tried two different ones), and this is what seems to work better than I expected. First, finished photos (3 gallon pictured):
The biggest challenge to this is that the bump-out is entirely curved. I used (on my second attempt) the single mounting plate from Rotopax, which spread the bolts out to a larger area. There is more curve vertically than horizontally, which is why I mounted my plate this way so the longer distance between bolts was horizontal.
My original plan was to try to do a "flat" mount where I would use closed cell foam or thick rubber sheeting to act as a gap filler, but the sheet metal is so flimsy that it collapses before the rubber squeezes. Plan two was to get high-strength two-part urethane foam and use a plastic bag to mold it to the shape of the curve on the inside, which would theoretically allow me to use flat steel bars to hold it in place, and prevent the sheet metal from buckling to do foam/rubber on the outside. I'm pretty sure that would've worked as well.
What I ended up doing was using a series of washers to keep the flat parts "away" from the curved parts so they could stay straight and not buckle the metal.
Parts:
Rotopax single mounting plate with rotopax holder already attached
4x Grade 8 1/4" x 1 1/2" bolts
8x Grade 8 washers
4x Grade 8 lock nuts
4x 1/4" galvanized bonded sealing washers
4x small diameter stainless washers
4x large diameter stainless washers (I used 1 1/4")
4x small diameter rubber washers
4x large diameter rubber washers
1x 24" x 12" galvanized sheet metal
1x 3" x 3' steel bar (I did 3/16" thickness, you can also go wider)
1x 1" x 3' aluminum square tubing (you could do more steel, but I did this to keep weight down)
Scrap rubber sheets, or new sheets from the plumbing department. (Comes in 6" squares in 1/8" and 1/16" thickness)
RTV
Rustoleum or any protective paint
Here is a rough diagram done in powerpoint:
1. Take the rear panel off. There are two 7mm bolts behind the first aid kit, and two 10mm bolts in the handle under the covers. Then gently pull to release the clips.
2. Mark your drilling locations with masking tape and marker - this is easier with help. I aimed to have mine centered, but if you want to keep your Xterra badge on the rear you may have to adjust. I also used a level to verify my bumper and the floor were level, and made sure the mount was the same.
3. Double-check everything, then drill a small pilot hole, followed by 1/4" holes (the size of the stock hardware, and replacement hardware I bought).
4. Remove the tape and any burs, and apply a bit of paint to the bare metal to protect from rust.
5. Using cardboard or similar, figure out the largest you can cut your sheet metal, and trace where you have to cut tabs out to sit flat against the existing metal.
6. Apply pressure to the back of the sheet metal to match the curve of the hatch, and mark the four holes for drilling.
7. Drill out the sheet metal.
8. Put the bolts and washers through the four holes of the mounting plate, and slide on the bonding washers, which will keep your bolts from moving.
9. Place the four bolts through the holes in the hatch, put some RTV on the hatch for the sheet metal to grab to, and optionally put some on the inside of the bolt threads as well.
10. Put the sheet metal in place, and use washers and nuts (ideally regular nuts so you can spin them on easy) to hold the sheet metal to the hatch. Make sure you're not buckling anything.
11. Use cardboard or paper to see how long you can cut your steel bars so that they're vertical when the hatch is closed. Mark this, as well as the holes to drill using the bolts now in place for both sides. Important Note: the length will vary based on your placement, both proximity to supports and proximity to the curve of the hatch. The longer, the better for support, but too long and the end will be making contact with the metal and potentially buckle when you tighten down. I did about two inches above and below the bolts. If you're unsure, go ahead and stack all four washers in the diagram above, and make sure your ends don't contact the metal.
12. Cut your steel bars and drill them out.
13. Do the same measuring for the aluminum tubing horizontally, but they only need to bridge the steel bars to add rigidity. They may not even be entirely necessary, but I didn't want any doubt. For the square tubing, one side will be the 1/4" hole and the other side needs to be large enough to fit a socket head through (see pics below).
Assemble everything except rubber shims as shown in the diagram above. Be sure when you tighten, you criss-cross and do a little at a time. Go SLOW and watch for buckling. If there is any, you may consider doing an additional small rubber washer on the inside and/or outside.
14. Once tight, use rubber sheeting or scrap rubber as "shims" between the ends of the steel bars and the hatch. This will eliminate any last little bit of play the metal may have and tighten everything up nicely. To do this, I used a 1/8" piece about 3" square so it extended out past the steel, and then inserted a 1/16" thick piece as tight as I could get it between the hatch and steel bar. You might be tempted to put this in place before you tighten down the four nuts, but don't as I can tell you from experience it will end up creating a gap pulling the bar off the bolt's washers, and you'll add buckling. If you want it really tight, you can do the two different thicknesses, then use a thin fender washer to wedge in there as well to add tension. Do this for all four steel edges.
15. To cover sharp edges, clean everything up, help prevent vibration, and to make sure rubber shims didn't relocate, I added duct tape.
16. Put everything back together and admire!
In my case, with the hatch closed and I can yank on the extended part of the rotopax mount, and not only does the hatch and sheet metal not move at all, but the truck body moves slightly. It's extremely secure.
Here is a view from the side where I was making sure there was no buckling and checking to see that the bonding washers were tall enough to maintain a slight gap:
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