# Best way to accurately find the concavity of a longboard?

I am working on a 3d printed enclosure and I have a cheap no name deck that has a bit of concavity to it. With relatively simple tools what is the best way to measure the concavity? Need it relatively precise to minimize the gap when seating the enclosure underneath the deck.

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Use maybe some sort of seal that enertion is using on their new enclosures.

I have no idea what the best way is, to answer your real question.

It doesnâ€™t have to be that precise. Just enough concave so the box doesnâ€™t have to stretch to far. To measure, I take a ruler and a straight edge. Hold the straight edge at 90 degrees to the board and measure the gap on both sides at the approximate place where the edge of the case will be. Adjust until you have exactly the same gap on both sides. Then draw your arc. Use adhesive foam or something to fill in the gaps when mounting.

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Thanks, I tried that and I also tried putting a straight edge across the top of the board and then using a caliper to measure the depth at the middle to give me a â€śdepthâ€ť of the arc then subtracted the sides to get an approximate arc shape, I got a pretty similar shape from that method as well but it was a bit more shallow will try printing it and post results later.

the tool you are looking for is called a contour gauge.

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or a bunch of skewers in a piece of cardboard if you are on a budgetâ€¦

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Contour gauges are not expensive if you want to get it super precise. You can pick one up for around \$10.

Of course @lowGuido knows the tool. He da man.

Wow thanks that looks super useful, I am hoping that the concavity of my deck is nothing more complex than a parabola, but that device would give much more accurate measurements. Canâ€™t imagine inputting those values in CAD

EDIT: For those looking for finished enclosure:

Getting them in CAD, you could make a photo of the profile gauge. Import it and scale it. There will be a little distortion, but it is probably good enough.