Help with Construction Drawing for Double-Curved GRC Panel

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I’m working on construction drawings for a GRC panel with a double-curved surface, and I’m not sure what’s the best practice to document it clearly for the factory.

I attached a sample of how we usually document standard panels (mostly flat or double-curved), but now I need to make sure the double-curved shape is clearly represented for mold fabrication.

My main questions:

  • How can I document the curvature clearly? Will showing Gaussian curvature or section profiles help the factory build the mold more accurately?
  • Should I include 2D contour slices, or is there a better way to communicate the 3D shape?
  • Do I need to flatten or unroll the panel for dimensions, or should I keep curved lengths?

The panel will be cast in GRC, so accurate formwork is important. Any advice or examples would really help. Thanks in advance

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What do the fabricators need? It sounds like you will want to create eggcrate framework and/or profiles that they can check against.

How does that work with the stiffeners?

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Thanks a lot for the quick response!

Yes, the panel will be cast in GRC, and it includes integrated stiffeners on the back, so accuracy is important.

I understand that using eggcrate framework or profile sections could help the fabricators check the double-curved shape. I just have a few follow-up questions:

  1. Do you recommend adding a series of section cuts (e.g. every 300mm) as reference profiles for the mold verification?
  2. Should those section cuts be aligned in one direction (X or Y), or both axes, especially since the panel has curvature in both directions?
  3. Regarding the stiffeners — should I extract their profiles from the same section cuts used for the front face, or is it better to model and document them separately?

Also, would adding curvature analysis (Gaussian or mean curvature) visuals help the factory understand the geometry better, or is that mostly useful for design review?

Thanks again – I really appreciate your help

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A lot depends on the fabricators, being cast vs rolled does make this a lot easier.

Cutting out the profiles x & y out of scape material that could be put together egg crate style seems optimal. How is the mold being generated? 3d printed?

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Yes, the panel will be cast, and not rolled — so that definitely simplifies things.

Right now, we’re exploring two mold generation options:

  1. CNC-milled foam mold, based on the double-curved surface.
  2. Or, using laser-cut eggcrate profiles (X and Y) from MDF or plywood to manually build the mold frame, then skinning it with fiberglass or similar material.

We’re not considering 3D printing for the full-size mold due to size and cost constraints.

Do you think combining the eggcrate approach with curvature section profiles is reliable enough for the factory to follow?
And would you recommend embedding any tolerance margins in the drawings?

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The eggcrate and curvature is the traditional method. It’s low cost, and easy to adjust as your shop works through process.

Tolerances aren’t too much of an issue with the profiles, it they fit its correct, as will be the stiffeners.

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i see different issues / topics:

  • the data to validate if the contract is fulfilled - more a legal aspect - and maybe the main reason why we still have so much paper and 2d. Diagonals might serve as a nice / additional value for validation - but are not very helpful for production.
  • the production data, that describes the final part - which might also be a 3d file
  • the data for the mould making

If the production company needs accurate 2d plans for their production, ask them if they can do the drawings based on your input geometry / 3d file. - or work out a sample with them - or ask them for a reference 2d-Drawing

??