how did the narratorand the other three men in the dingey try to help constans? why does the narrator say its is "lucky" that constans never reached the men in the dingey?

Here is the quote you are looking for. It's all in there.

Constans, who was "seen by the captain to jump into the gig,"

Note: Daily News, March 17, 1887. luckily for us and unluckily for himself did not reach us. He came down out of the tangle of ropes under the stays of the smashed bowsprit, some small rope caught his heel as he let go, and he hung for a moment head downward, and then fell and struck a block or spar floating in the water. We pulled towards him, but he never came up.

I say lucky for us he did not reach us, and I might almost say luckily for himself; for we had only a small breaker of water and some soddened ship's biscuits with us, so sudden had been the alarm, so unprepared the ship for any disaster. We thought the people on the launch would be better provisioned (though it seems they were not), and we tried to hail them. They could not have heard us, and the next morning when the drizzle cleared,