Flatbed and composite panel build on Dodge 2500
- Thread starter Jeep
- Start date
Got the cabinets done and on, I'm going to do a quick re design and change the box angle from 45 degree to 60 degree, that will tighten it up around the tire a bit and give a few more inches of room at the bottom of the cabinets. Later though, got a camper to build first!
We hit NWOL, great event, got home, put new doors on the cabinets with a really good bulb seal and replaced the latches with what we usually use on our industrial builds. The ones we tried initially looked good and are heavy duty, but they are not as good as what we were trying to replace.
Now we are doing some pull testing with adhesives, we did some 12" square panels with 12" of our extrusion on each end. I used Sika 252 and 3M 760 Hybrid. The extrusions were powder coated white except for one which was left raw.
The samples were prepped as follows:
No prep, just wiped.
Abrasive pad scuff on the powder coated extrusion surface, and the painted aluminum side.
Abrasive pad scuff on the powder coated extrusion side, and the painted aluminum side, Sika activator and Sika primer on the powder coated surface.
Raw aluminum, wiped and scuffed with an abrasive pad (this was the sample for the 3M 760).
The 760 was the easiest to inject into the glue channel within the extrusion, the Sika 252 was very viscous and injected easier when warmed up to the maximum raw product temperature.
We waited 5 days at an average 25 Celsius which is 77 Fahrenheit, humidity never fell below 50%.
Then we riveted anchor plates to the extrusion using our typical 1/4" structural rivets, every 2" apart on one sample and 4" apart on the other, figured we might as well see what we are getting out of the rivets at the same time. The assembly was put into a pull press and we pulled each sample until failure. The results are as follows:
Raw aluminum with minimal prep and 3M 760 failed at 3660 lbs pull.
Just wiped, with Sika 252 powder coated extrusions 4280 lbs to pull and again, only an 8" bead in the glue channel.
Wiped and scuffed powder coated extrusions with abrasive pad with Sika 252 went to 4520 lbs with 8" bead in the glue channel.
Wiped, scuffed, activator, primer went to 4860 lbs with 8" bead in the glue channel.
The panels had no sign of damage, no cracking noises under pressure, nothing. Very happy with the performance.
Now here is the interesting part, this test is completely invalid, the adhesive was not fully cured. I would estimate that they were 50% cured, the adhesive in the glue channel on the fibreglass skin side was cured further than that on the aluminum skin side, the adhesive was fully bonded to the powder coated extrusion, and the fibreglass skin. On the fibreglass side, the adhesive tore and the inside was "tacky" but would not leave anything on your finger. The aluminum side kind of "wiped" the adhesive off the aluminum and the adhesive was a little more gooey. The 760 was pretty much the same. We waited 5 days as per manufacturers cure time charts and I'm pretty sure another 5 days would have made a huge difference. These adhesives are pretty incredible considering, but I am leading to use them in other areas where they can be exposed to a little more moisture and monitored better. I have sourced some 2 component urethane adhesives that will work much better in an enclosed channel, and I won't risk the "it should be cured" statement. I want to be assured of performance and another test will bee under way in another week and based on it's success I will start the camper!
Fibreglass side
Aluminum side
Inside the glue channel in the extrusion
Now we are doing some pull testing with adhesives, we did some 12" square panels with 12" of our extrusion on each end. I used Sika 252 and 3M 760 Hybrid. The extrusions were powder coated white except for one which was left raw.
The samples were prepped as follows:
No prep, just wiped.
Abrasive pad scuff on the powder coated extrusion surface, and the painted aluminum side.
Abrasive pad scuff on the powder coated extrusion side, and the painted aluminum side, Sika activator and Sika primer on the powder coated surface.
Raw aluminum, wiped and scuffed with an abrasive pad (this was the sample for the 3M 760).
The 760 was the easiest to inject into the glue channel within the extrusion, the Sika 252 was very viscous and injected easier when warmed up to the maximum raw product temperature.
We waited 5 days at an average 25 Celsius which is 77 Fahrenheit, humidity never fell below 50%.
Then we riveted anchor plates to the extrusion using our typical 1/4" structural rivets, every 2" apart on one sample and 4" apart on the other, figured we might as well see what we are getting out of the rivets at the same time. The assembly was put into a pull press and we pulled each sample until failure. The results are as follows:
Raw aluminum with minimal prep and 3M 760 failed at 3660 lbs pull.
Just wiped, with Sika 252 powder coated extrusions 4280 lbs to pull and again, only an 8" bead in the glue channel.
Wiped and scuffed powder coated extrusions with abrasive pad with Sika 252 went to 4520 lbs with 8" bead in the glue channel.
Wiped, scuffed, activator, primer went to 4860 lbs with 8" bead in the glue channel.
The panels had no sign of damage, no cracking noises under pressure, nothing. Very happy with the performance.
Now here is the interesting part, this test is completely invalid, the adhesive was not fully cured. I would estimate that they were 50% cured, the adhesive in the glue channel on the fibreglass skin side was cured further than that on the aluminum skin side, the adhesive was fully bonded to the powder coated extrusion, and the fibreglass skin. On the fibreglass side, the adhesive tore and the inside was "tacky" but would not leave anything on your finger. The aluminum side kind of "wiped" the adhesive off the aluminum and the adhesive was a little more gooey. The 760 was pretty much the same. We waited 5 days as per manufacturers cure time charts and I'm pretty sure another 5 days would have made a huge difference. These adhesives are pretty incredible considering, but I am leading to use them in other areas where they can be exposed to a little more moisture and monitored better. I have sourced some 2 component urethane adhesives that will work much better in an enclosed channel, and I won't risk the "it should be cured" statement. I want to be assured of performance and another test will bee under way in another week and based on it's success I will start the camper!
Fibreglass side
Aluminum side
Inside the glue channel in the extrusion
Fast exploring
This is how you get to the top of the mountain! A good weekend riding.
The crew.
Big boys, the peak.
Broken chain 40 KM from camp! Pine tow bar foot peg to foot peg with wire and zip ties and away we go!
3 days riding in the rocks is hard on rubber….
This is how you get to the top of the mountain! A good weekend riding.
The crew.
Big boys, the peak.
Broken chain 40 KM from camp! Pine tow bar foot peg to foot peg with wire and zip ties and away we go!
3 days riding in the rocks is hard on rubber….
Did some more testing after the Sika cured another 5 days. The Sika on the fibreglass side was pretty much cured, the aluminum side was still very raw, maybe 25% cured but some interesting results nonetheless. I just through bolted a couple of pull plates to the panel in double shear to see if it would hold up against adhesive.
All set up in the press:
This panel had just a scuff and Sika 252, it went to 4750 lbs. before bond failure, up from 4520 lbs. as previous, but again not a cured bond.
This is the panel that had a full prep with activator and primer, went to 5000 lbs., up from 4860. Interesting part about this test is that the fiberglass skin failed at just under 5000 lbs. and the aluminum skin held, shortly after the bond failed. So a row of bolts every 2 " is about as strong as a half cured adhesive! Benefit of the adhesive is the panel is not destroyed, and at a 100% cure there is no possible way a row of bolts or rivets will hold as well. One thing to note is the pull plates are riveted on, they have suffered absolutely no deformation or damage, and on one test specimen there are only 4 1/4" rivets per foot. This proves the integrity of the rivets and extrusions, even with half cured adhesive holding 5000 lb. per foot, we know that we can support a structure like a camper at a weight of 20 000 lbs. on a set of jacks only held on by 4 - 1/4" rivets per corner. Obviously I'm going to use a couple more rivets, just because, and the adhesives will be 100% cured, and the camper will weigh in around 1600-1800 lbs. so I don't think we will have any issues whatsoever. I can't wait to test the 2 component urethanes that are on their way, the 2 component guarantees a full cure.
All set up in the press:
This panel had just a scuff and Sika 252, it went to 4750 lbs. before bond failure, up from 4520 lbs. as previous, but again not a cured bond.
This is the panel that had a full prep with activator and primer, went to 5000 lbs., up from 4860. Interesting part about this test is that the fiberglass skin failed at just under 5000 lbs. and the aluminum skin held, shortly after the bond failed. So a row of bolts every 2 " is about as strong as a half cured adhesive! Benefit of the adhesive is the panel is not destroyed, and at a 100% cure there is no possible way a row of bolts or rivets will hold as well. One thing to note is the pull plates are riveted on, they have suffered absolutely no deformation or damage, and on one test specimen there are only 4 1/4" rivets per foot. This proves the integrity of the rivets and extrusions, even with half cured adhesive holding 5000 lb. per foot, we know that we can support a structure like a camper at a weight of 20 000 lbs. on a set of jacks only held on by 4 - 1/4" rivets per corner. Obviously I'm going to use a couple more rivets, just because, and the adhesives will be 100% cured, and the camper will weigh in around 1600-1800 lbs. so I don't think we will have any issues whatsoever. I can't wait to test the 2 component urethanes that are on their way, the 2 component guarantees a full cure.
Thanks Brad, although I've been successful with adhesives I have been exposed to enough false assumptions and misapplications to trust anything other than a thorough analysis and testing of such products in their intended application. There are also enough general fabrication compromises when trying to grab existing parts and pieces from various sources and putting them together. I'm doing an engineered, tested, and proven system of compatible components for other industries I service, that will spill over into my camper build, and I will always have a test specimen in possession! I am glad to share this development with readers, I love seeing this kind of stuff from other industries that can cross over posted up.
