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Old 09-09-2022, 11:26 AM   #1
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Gas Strut Roof Modification Backing Plate

I know it has been a long time since my last post here. I finally have all the hardware and gas struts for my modification following Trailer Texan's measurements. I am not sure how big of a backplate it requires. I have a 2" wide 1/8" aluminum flat bar that I was going to use for this. Would a 3" piece of this be enough? I am not an engineer and do not know exactly how much surface area is required to distribute the force. Does it need to extend to structural support?

Thank you for any insight.

Dadroach
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Old 09-09-2022, 12:30 PM   #2
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cut a piece of white cutting board from a cutting board like at walmart in the kitchen supplys. tough as steel, shapable easy to drill. its my go to material for spacers shims. Doesnt glue well, but sealable with silicone.
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Old 09-09-2022, 03:21 PM   #3
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Dadroach

Having replaced the lift motor with gas struts myself, I understand your question.

From an engineering perspective, the bolts for the strut mounts are going to be primarily in shear, not compression or tension. The A-frame wall is pretty weak in point shear (screws easily pull out or wallow sideways), but much better in overall shear forces because the aluminum frame is taking some of the load. Therefore, I sought to make a clamp with the strut mount and backing plate to spread the load. Both strut mount and backing plate should carry the shear load of the mounting bolts. I used #10 machine screws, and 1/4" plywood backing plate with 3/4" flat washers on the inside of the camper to attach the lower strut mount. The plywood is maybe 2" x 3", no need to make a whole lot bigger than the strut base. I caulked and tightened the screws to just start to visibly dimple the outer fiberglass surface.

I have had no problems in the year since I performed the mod. I used 40# struts on the rear, and had previously installed 60# struts on the front roof. The 60# struts have caused a visible curve in the aluminum flange, but nothing like that happened with the 40# struts. The backing plates have prevented any damage around the mounts.

Fred W
2019 Flagstaff T21TBHW A-frame
2022 Hyundai Palisade
last trip: Charlotte and Cary, NC, Aug-Sept 2022
next trip: in planning
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Old 09-09-2022, 03:33 PM   #4
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Thank you, Pgandw.

From your information, the 2" X 3" aluminum flat bar will work perfectly. I will give that a try.

Dadroach
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Old 09-11-2022, 07:17 PM   #5
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Good evening! This is Cale J. I believe we met at McDowell Nature Park in Charlotte the morning of 9/2. We were staying beside you and had almost and identical camper. You showed me your system and it’s amazingly coincidental that I found you on this forum. Would you be willing to share images of the inside backing plate you installed? I’m doing the modification now and I want to get it right. I’m so glad I ran into you. This is awesome!
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Old 09-12-2022, 11:48 AM   #6
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Quote:
Originally Posted by bz564 View Post
Good evening! This is Cale J. I believe we met at McDowell Nature Park in Charlotte the morning of 9/2. We were staying beside you and had almost and identical camper. You showed me your system and it’s amazingly coincidental that I found you on this forum. Would you be willing to share images of the inside backing plate you installed? I’m doing the modification now and I want to get it right. I’m so glad I ran into you. This is awesome!
Cale - Attached is a photo of the backing plate I made for the port front gas strut. The front roof gas struts were OEM on my early 2019 A-frame, as Flagstaff/Rockwood tried to figure out ways to deal with the failing electric lift problem. The lower gas strut mounts had no backing, and simply used screws into the side of the camper. These were tearing out due to the side forces on the screws. The starboard side was faring better because the screws hit the piano hinge for the toilet cabinet cover.

The OEM front roof gas struts were not doing anything so I replaced them with 60# struts, and reinstalled the lower mounts with #10 stainless steel machine screws (1.75" long, could have used 1.5" long). I added a backing plate on the port side made of 1/4" plywood. I stained the plywood to make it look better, although it turned out to be behind the dinette back cushion. Only seen when we use the dinette for a 3rd bed. Since all screws on the starboard side hit the wall portion of the piano hinge for the toilet cabinet, no backing plate was needed. Acorn nuts were used with lock and regular washers to avoid any sharp edges.

The 60# front struts provided some assistance to the electric lift, but didn't solve the problem. But I'm not removing the front struts because the mount holes would be ugly to plug. The 40# rear gas struts eliminate the need for the electric lift. On this forum in another thread are my notes from my install Sept 2021.

When I get a chance, I'll take photos of the rear strut inside install - A-frame is currently stored in garage. As I pointed out in earlier write-ups of the rear roof gas struts, I needed the lower mount point to be behind the mattress of the rear bed. Longest 40# struts I could find readily were 35"-36" extended. My queen DW would not allow being able to "feel" the acorn nuts while sleeping in the twin bed configuration. This made the strut more vertical than others who made more of a folding knee action strut with a higher lower mount point.

But the 40# rear struts work great anyway. I've had them for a year now, raised and lowered the camper roof at least 20 times since. The rear struts hold the roof at any position I push/pull it to. I use a boat hook with rubber tips in the handle from the ground outside to push the roof up or to pull it down. Usually have to go to other side to fully engage roof "latch" in the up position.

Electric lift was removed Sept 2021, and I have not reinstalled. There is nothing to prevent using the lift with the gas struts if I wanted to, but it is so much faster just to push the roof up or pull it down than wait for the motor to do it that I can't be bothered reinstalling the lift motor, and hoping it doesn't crap out this time.

That was a nice park in Charlotte, with really nice bathrooms/showers. Lots of shade. Sites not very level, and some were real short, but enjoyed the park anyway. Very much enjoyed meeting you.

Fred W
2019 Flagstaff T21TBHW A-frame
2022 Hyundai Palisade
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Old 09-12-2022, 12:29 PM   #7
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Cale - here's some photos I just took of the port side rear gas strut backing plate and mount. We have the stock mattress with 3" memory foam pads on top, but mount is behind stock mattress, almost to the bottom just above plywood base.

Again, others doing this mod have mounted the lower mounts much higher than I did, which gives more of a folding action to the strut. My struts are almost straight push/pull.

Had to be careful that I didn't hit either max or min extension of strut with roof open/closed. Mounted upper end first on roof frame about 23.5" in from back edge. Then put extended strut on upper mount with roof open and swung arcs with strut to find suitable lower mount point. With mount point determined with extended strut, took measurements, then moved lower mount 1" closer to upper mount. Remeasured with roof open and closed before committing to drilling holes.

Hope this helps.

Fred W
2019 Flagstaff T21TBHW A-frame
2022 Hyundai Palisade
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Old 09-12-2022, 01:35 PM   #8
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So very helpful! Thank you so much for the information. It was nice meeting you. Happy trails,

Cale
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