Originally Posted by xymotic
I've sounded my hull pretty thoroughly and this summer I intend to grind off the bottom paint
so I should hopefully be able to see a bit better; but can you elaborate on the light and what are you looking for? Deflection of the surface when you hit it?
No, sounding is a separate and unrelated method. Takes a while to learn to interpret what you hear/feel. Seeing is easy
A glancing or "skimming" light beam - i.e. almost parallel to the surface under inspection
- casts long
shadows of even the tiniest surface imperfections. Throws irregularities into sharp relief like aerial surveys near sunrise and sunset.
On topsides, when someone has used a grinding disc or a rust patch has been grit blasted you can see exactly the limits of the repair.
You can tell where sheet edges, frames etc. are by the tiny changes in level/direction of the plates.
Even under thick antifouling you can see when rust is bubbling up as soon as it starts.
Inspecting this way is more effective in low light simply because the contrast is better than in bright light.
The newer LED torches throw an even light over a wide or narrow beam.
Vastly better than an incandescent bulb, very white light.
I like the Cree T6 with a focusing beam, 2 rechargeable batteries
, alloy body with water resistant seals
, drop-proof. About £15 from China
Not keen on modes (flash, bright, dim) accessed by repeated presses of the power button for industrial use but they're better than anything else available so I put up with it.
I can find any tiny blemish on an 8 x 4 powder coated sheet in a few seconds.
With steel hulls keep a plastic coated magnet in your pocket to find filler and estimate its depth
- and a tiny mirror to deflect the beam iwhen you want to "skim" a small panel in, say, a bilge
next to a frame where you can't hold the torch flat.