Miracle Tube Cleaner
This may be like teaching you all to suck eggs, but discovered a fantastic cheap alternative to all those expensive "RIB specific" cleaners out there. Used plain liquid detergent from Sainsbury's...you know, the stuff that comes in little plastic sachets. Three sachets did a fantastic job on the tubes of my 6m boat. All for about 50p and an hours work. And believe me they were bloody filthy/oxidised etc.
Just a suggestion........
Have a great weekend, especially if you're out in Plymouth sound or on the Eddtystone reef!