Sheetmetal fastening - Smooth finish surface?

[AgitatedPancake]

Looking to get schooled on all the various sorts of sheetmetal fastening, trying to get the best finish in a production style environment. Essentially hoping there's a mechanical connection that can leave a nearly perfect surface finish like on an exterior body panel without requiring body work to follow. Don't really want to rely on adhesives unless I can be convinced they're essentially indestructable.

-Resistance spot welds like the factory use are very effective and quick, but dimple both surfaces getting pinched and connected.

-Flush mount rivets like on planes would be aerodynamically smooth, but the rivet head is very obvious (and this seems time intensive)

-Self cinching studs seem similar to flush mount rivets in leaving a visible obvious circle head even if it is flush with the panel.

-Threaded studs welded only on one side?

What else is there?

 

[Donk]

Bonding with some form of structural adhesive? Does it need to come apart easily again?

 

[Donk]

About the only way to break this shit LOCTITE EA 9309NA AERO is to freeze it with dry ice or heat it till it melts.

 

[AgitatedPancake]

I'm hesitant about adhesives because even though I know they're impressive and the factory uses them all over, I'm just stuck in the mentality "they just can't be as strong as a mechanical connection". I know that may be irrational with how good they are these days and they check most of the boxes I want, maybe that is what I need to look at after all. I've seen some pretty impressive ones from 3m also more research to be done.

 

[Twankie]

What exactly is the application?

Can you roll an edge over similar to a door skin on an automotive door shell?

Or are you fastening lapping sheet metal joints?

 

[AgitatedPancake]

Working on a custom built flatfender concept I've been kicking around for a while. Trying to figure out the best plan of attack to connect the rear wheel wells to the outer body skins. Would rather leave that outer panel nice and smooth, uninterrupted if possible. So unfortunately I can't roll/hem them together due to the edges not being aligned. But I can change the size of the flange that the wheel tub uses to interface with the outer skin, so I could make it nice and wide to get as much bonding surface area as possible if I were to go the adhesive route.

 

[SLOWPOKE693]

Panel bond adhesive and seam sealer.....


Done

 

[dirtybird]

A flush huck bolt would do it.

 

[Donk]

I'm hesitant about adhesives because even though I know they're impressive and the factory uses them all over, I'm just stuck in the mentality "they just can't be as strong as a mechanical connection". I know that may be irrational with how good they are these days and they check most of the boxes I want, maybe that is what I need to look at after all. I've seen some pretty impressive ones from 3m also more research to be done.

The brilliant thing about adhesives is a 100% joining surface. No gaps to trap moisture/dirt/salt, no rivets to work loose, no HAZ to crack. Some downsides are lack of extreme temperature resistance, inability to easily disassemble, sensitivity to surface preparation and cost of some of the ultra high strength adhesives.
Rivets for example may seem simpler but installing them dead flush in aluminium without distortion of the panels is easier said than done.

 

[Provience]

Working on a custom built flatfender concept I've been kicking around for a while. Trying to figure out the best plan of attack to connect the rear wheel wells to the outer body skins. Would rather leave that outer panel nice and smooth, uninterrupted if possible. So unfortunately I can't roll/hem them together due to the edges not being aligned. But I can change the size of the flange that the wheel tub uses to interface with the outer skin, so I could make it nice and wide to get as much bonding surface area as possible if I were to go the adhesive route.

would you be able to roll an angle piece, which could be then riveted/bolted to the body side and use panel bond/adhesive to hold a flush fender on top?

at least it would be removable in the event of damage

 

[AgitatedPancake]

dirtybird, the huck bolts look like they leave a visible circular head (even if flush), I was really hoping for an uninterrupted surface but realizing that may not be possible without adhesives.

Hey Provience! The riveting/bolting to the body side is my hang up, as there isn't a great way to conceal any fastener on the body panel itself.

So far it's looking like adhesive is my answer even though I've been stubborn and resistant to it haha. May be time to get learned up.

 

[bdkw1]

dirtybird, the huck bolts look like they leave a visible circular head (even if flush), I was really hoping for an uninterrupted surface but realizing that may not be possible without adhesives.

Hey Provience! The riveting/bolting to the body side is my hang up, as there isn't a great way to conceal any fastener on the body panel itself.

So far it's looking like adhesive is my answer even though I've been stubborn and resistant to it haha. May be time to get learned up.

On the old board there was the guy making the sandwich foam camper. He did some good pull tests with different adhesives. The top ones, the aluminum sheet gave up before the adhesive. Ultimate tensile strength was pretty impressive. I wanna say the 5200 3M stuff was the winner but I could be wrong.

 

[Betarocker]

French Cleat concept with some blind fasteners to prevent slipping out.

 

[aczlan]

On the old board there was the guy making the sandwich foam camper. He did some good pull tests with different adhesives. The top ones, the aluminum sheet gave up before the adhesive. Ultimate tensile strength was pretty impressive. I wanna say the 5200 3M stuff was the winner but I could be wrong.

Was it Rocky? He posted the following and seems to run a shop that builds composite campers:

The Dibond is held on with 3M tape, I used Sika flex 252 on the roof. I used Sika for years on other stuff so I started with it but when a 3M rep dropped off some tape samples and we did some destructive testing we found it was stronger than the Sika so I switched. All the panels are arranged so I can rivet the skin if the bonding ever fails.

And Overland Explorer Vehicles – Manufacturers of Fully Composite Campers and Expedition Cabins

Aaron Z

 

[bdkw1]

That was it. ^^^^^^