Water Sealing rack to shell / topper?

[Superduty]

SCROLL DOWN TO POST 5 FOR WATER SEALING DISCUSSION.



I have an ARE contractors shell on my truck. I am going to make a low profile rack out of out 1.5x1.5 8020 aluminum. It will sit about 1/4" about the roof of the shell. The rack will hold a solar panel and an Alu Cab Awning.

I plan on bolting it to the top of the shell. Which method below is better? I assume option 2 is stronger, but I also think that will be considerably hard to make accurate holes to line up with the aluminum frame. Assuming option 2 is stronger is it that much stronger to warrant the extra hassle?

Any other suggestions in terms of bolting it are welcome.

Any suggestions or tips or tricks on getting the rack (large rectangle 4'x8') lined up and marked for drilling?


I will bolt to the aluminum framing.




Option one is to use a carriage bolt and slide it into the track of the 8020. This will likely be easier overall as I only need to get one direction correct in terms of the hole in the aluminum frame, then the carriage bolt slides to the correct location.




Option 2 is to use a carriage bolt and through bolt it all the way through the 8020.




Thanks for your help.


.

 

[Superduty]

@FrenchieXJ thanks for the reply. I am not sure what you mean by running the rails over the existing blocks. I was planning on bolting to these parts of the frame indicated in red.



The frame of the shell is 1x1. Can you explain some more about the larger tube cut into a C to overlay the 1x1? Would the overlay not touch the 1x1? Would that C be made of aluminum?

There are upright supports / legs at the front and rear that go down to the bed rail.

For sealant I was going to use Sika 221.

 

[Superduty]

The U shaped aluminum to work as a large body washer makes perfect sense. I like that idea.

Option 1 it is. I think you are correct @Verkstad it will be easier to seal that way.

 

[Superduty]

Looking for additional guidance. I have built the rack. Now I am looking for suggestions on how best to seal the rack to the shell. Current plan is to use Sika 221 (unless someone suggests something better or a good reason to not use 221).





This is what the rack looks like. There are 12 carriage bolts that go into the bottom track and then will go through the shell and bolt to the aluminum frame of the shell.



Solar panel mounted to the 8020


Small section of 8020 to show the bolting. 8020, then a piece of 3/8" HDPE (spacer between the 8020 and the aluminum roof of shell), then the shell.






I will put a bead of Sika 221 on the bottom of the HDPE. I think that will eliminate any water getting in between the shell and HDPE.




That will likely eliminate MOST water intrusion. I am concerned about water getting into the lower track and then following the carriage bolt down. I suspect there will have to be a heavy rain for that to happen with considerable pooling on the shell roof - as it would have to be above the HDPE to flow over it. But if the truck is moving then I think the water could easily flow over the HDPE and into the lower track.

What do you guys think?

 

[Superduty]

I doubt you will have problem if you get as good bedding of sealant around the fastener shank and between roof skin and HDPE spacer.
As the fastener is tightened, that will force out excess as well force sealant tightly in around the bolt.
A slight countersink in roof skin and/or underside of the spacer will assure a good ring of sealant is captured around the bolt.
As far as HDPE. Be sure its good for long term UV exposure.
I made various spacers from kitchen cuttingboards, a couple years before they cracked up seriously, no longer giving much strength.

That's not encouraging about the cutting boards. I thought the cutting board material is very durable. Maybe they aren't true HDPE? Or a cheap grade of HDPE?