1. I assume that the Spark Trap (Product No. 484733) is used when sanding on metal. Is this correct, or is it intended more for cutting metal, and hence might not be necessary for sanding paint and resin off of steel;
You do not need the sparktrap when sanding metal. Believe me, I've sanded quite some metal in my life, and sparks, well, they are simply not part of the experience.
under what conditions am I most apt to create sparking sufficient to cause a problem?
You get sparks when you get metal on metal action, like when you cut it with a grinder/jigsaw or use a wire brush. Sandpaper does not contain any metal parts. The grit particles in Festool's sandpaper are made from either aluminium oxide or silicon carbide, both non-metals. Perhaps on some extremely rare occasions can you get a spark. Not something I'd worry about. In my experience it's easier to create a smoldering wood particle with sawing than creating a spark while sanding.
2. The text for the Spark Trap states "For use with the Festool CT 33 and CT 33 Dust Extractors." I assume it will work with the CT26/36/48 units and the text is merely in need of being updated. Is this correct?
The text apparently needs updating. When you type in the spark trap's product number in Festool USA's search box you get the following page
, which states the new vacs also as compatible. Which is logical since the hose size and it's connectors didn't change.
One curious thing though: on the European websites the description of the spark trap is now changed
. It specifically states it is not to be used in actions that generate a lot of sparks like with grinders and only acts as additional safety device for sanding wood which might contain an unexpected nail. Which renders the entire spark trap more or less useless, because the chance of a nail generating sparks when sanding is about zero.
3. Can anyone compare Titan 2 with Saphir for removing paint and "half-inch thick" resin from a steel boat hull?
When you're talking about paint that's actually, SERIOUSLY, half an inch thick, I'd look at other ways to remove it than sanding. Its gonna be an impossible job, sanding that away. I'd try to start by scraping/chiseling it away with a good big scraper (4'' blade, 2' handle) first, and if you can get your hands on it, a sandblaster. That's how the professional companies do it. A chemical stripper is also a solution that might prove faster and cheaper than sanding. Only use sanding to clean up the last bits. Sanding is simply not suited for layers half an inch thick. As a comparison, we used to spray cars in the body shop with a layer of 120 micrometer. That's about 1/200th of an inch. Quite a difference. Paint on wood is generally a bit thicker, more in the 250-400 micrometer range.
Titan paper is used for high end finishes on cars and is best suited for the 120 micrometer range I was talking about above. Nevertheless, 40 grit Titan can be very aggressive. But such a low grit is no use for layers half an inch thick. Same story for Saphir. If the paint was fully cured (hardened through and through), it might take you AGES to get rid of it. But chances are, and I'm pretty sure they are, that such a thick layer will never cure completely. So your paper is gonna gum up in no time making the task even more impossible.
I'd try to get my hands on a sandblaster, start with that and go on with a paint stripper, and finally sanding for the last phase.