Designing an etch

[NScaleNotes]

Hello all

Hopefully this is the right place for this post. 

I've created a sheet of flat items for etching in the past but now I'm interested in creating something that will be rolled into a tube to form a tank.



The actual tube bit is fairly straight forward, the potential problem is that the tube/tank will need to have a couple of holes in it:



So I can add manlids, created either in etch or from styrene/3D printed:



Am I right in thinking that the dimensions of the holes that I'd need to create on the flat etch that becomes the tube would be different to the actual dimensions of the manlids to account for the curve of the final tube shape?
If so, how on Earth do you go about calculating how big the holes should be?
Any advice or pointers to a tutorial would be appreciated. Everything I can find relates to surface etching glassware or creating flat etches.

I could be overthinking it, it's been known to happen.

Simon

[emjaybee]

I'm no expert, but if your going to 'add' bits to the surface, do you need holes? Can you not just stick them on top?

[PaulCheffus]

I'm no expert, but if your going to 'add' bits to the surface, do you need holes? Can you not just stick them on top?

Hi

You could but then you would need to file a curve in the base of the added bits so they sit correctly on the barrel.

Cheers

Paul

[NScaleNotes]

emjaybee: No I suppose not, but the holes would definitely help with getting the placement correct.

Interesting thought though because it'd be much easier to design a jig that helps with correct placement.

See, over-thinking again 

PaulCheffus: That's not so much of a problem because I know the radius of the tube. Easy to etch something that folds up to create the right shape or create a 3D part with correct radius on the bottom.

Thanks

[NScaleNotes]

Ah, I think I may have found an answer by changing how I was searching: I'm basically trying to calculate the length on an arc.

This flexible metal framing company has just the tool for figuring this out if you know a couple of the dimensions involved:
http://www.flexabilityconcepts.com/arc-length-calculator

Hopefully, that'll be useful to others too.

Simon