Yes, sailing boat is one of the terms in "next weeks terms." I agree whith you that at least in AmE the term is rarely heard. I posted the question to see if it is used in another form of English.I noticed it as one of the phrases at the top of the page today. I think I've only heard "sailboat" aside from poetry and song.
I grew up with "sailing boat" but according to the ngram at https://books.google.com/ngrams/graph?content=sailing+boat,sailboat&year_start=1800&year_end=2000&corpus=18&smoothing=3&share=&direct_url=t1;,sailing boat;,c0;.t1;,sailboat;,c0, "sailboat" has been the dominant form in BrE since about 1980 (due, no doubt, to the influence of AmE, which has a number of compound nouns formed like their German equivalents, such as "cookbook" which, again according to ngram, overtook "cookery book" in BrE around 1960).Might be a cross-Atlantic difference again. Sailing boat is the more familiar term for me.