If you are planning to fold them from sheet metal, why not use a different design and orient the material to provide better stiffness rather than use a thicker gauge?
If you cut and folded something like this, you could design strength at the parts which need to resist the most load.
Could drill each side and bolt together at midspan with a spacer for extra rigidity.
nice sketches brother, and I like where you’re going with this!!
Hmmmmmmmmmmmm
seems like all the sheer force would develop right at the end of the horizontal bend line at the board end… relatively easy to fixerate with a good sheet-metal design and a tig welder…
Cheers Kook.
Thought about a bunch of diy options for these a while ago.
I bought G Bombs instead. Haha. Lazy.
Probably could’ve had my mate who has a water jet to cut and fold something like this for me, now I think about it 
If he just wants to cut and fold, he could try this in steel and bolt each side together and it’d be pretty strong.
I think it’s the board side connection where the weakness is. Lengthening that would help dissipate stress into the deck.
Hey
Sorry, I’m a little late for the party.
Assuming it’s 5052 like @MysticalDork said, the Yield strength is 193MPa (don’t aim at ultimate)
With your 70kg, you’re getting over it at 223MPa with a single 4mm sheet.
There are two problems with what you’re trying to do:
Assuming you have a single 6mm sheet, the stresses go down to ~100MPa, for 8mm to ~60MPa
These numbers seem to compare better with what 5052 can do, then again I have no idea what happens at the bend.
I have to ask why? I mean drop through is good when you’re trying to lower your board, but you manufacture those, so just make a bigger vertical offset…
For quick and dirty bending stress estimates, use the following:
S=6M/(b*c^2)
S-stress
M-the bending moment
c-plate thickness
b-the width of the plate
I estimated the loads long time ago for a different purpose, but it still holds:
https://dosimplecarbon.com/calculating-loads-for-longboards/
In your case it’s 70/2kg*(45+40mm)=~3kg.m (assuming the load from the truck acts at the middle of 90mm and the max stress is at the bend (sorry, I didn’t use cosine for the 40mm)…
Dani
So, notice what happens when we load the two stacked plates, notice the separation between the two, and bigger displacement (the scale is exaggerated for clarity):
The stresses are not that bad:
Another thing to consider is the localized shear on the bolts.
That’s an interesting idea 
Thanks Dani for your time 
Lots of stuff to read this morning
Having the choice to lower the board a bit if needed, and most of all I love the look of these forks decks 
That would be fixed by weldind
Ok, I’ll confess all those numbers are like Chinese to me
Would you say it’s a Go or no Go?
Where do you want to weld?
I would weld the sides edges together
Sounds good
I’ll rerun the analysis to see the new colors 
here is a 5 dollar ghetto version
It’s not bad, I say go for it.
It’s better to use the 5052 aluminum over 3003
(don’t overstress about the high stresses at the holes)
Good luck
Thanks Dani
dani
may I ask where you placed the welds when running the analysis?
complete circumferential?
I wish I knew how to run one of those stress analysis gizmos…
Because I’m fixing the bolts on the right side there’s no additional need to “weld” there.
The weld in this analysis are only on the cantilevered part, like in the picture:
This is more conservative than fully all around weld
