You're welcome Chris, that's the reason why we, any and all the members, are on this absolutely *No.1* website !
With your beautiful photos I am proud to be one of the members/brgds jadran

Thanks Jadran

@ Patagualino ... Hello !
The constructions fitted aside/outside on the Main Hull of the ship are so called: sponsoons or blisters.
They are void spaces i.e. void tanks (not ballast tanks).
Their purpose is only to widen/make bigger the ship's width on the waterline.
The numerical value of the ship's width ON THE WATERLINE (better is larger width as possible) is one of the crucial factors in the calculation for the basic ship's stability worthiness.
brgds/jadran

Probably, no doubt a more tehcnically minded member will answer.

Well Chris, They were amazing conversions from fundamentally a good design of a Cargo-Passenger, "semi-Cargo-liner" but that narrow beam & such a high surface area after conversion: would have worried me as a crew-member.....would I be right in thinking those "extensions" are some kind of external ballast tanks on the water-line (Rather like saddle tanks on a submarine?) to improve stability?

Very interesting photo, on first glance it is possible to see that this was not originally a carcarrier, it is very narrow for such one and the funnel shows it as well.

Still better looking than modern cupboards.

HOEGH TRAVELLER was converted (together with her two other sisters) at shipyard Viktor Lenac, Rijeka, Croatia (then YU) beginning 1970s.

They were actually a good design built for a trade that could support both passengers and cargo, ie UK to South America, generally they were well supported with passenger numbers, the killer was the constant delays while working cargo, the same thing that killed them when Shaw Savill operated the three briefly to Australasia, they did however become the best looking vehicle carriers, well in my opinion.

Hard to believe that these unsightly ro-ro conversions were once the handsome Royal Mail passenger/freight liners! how obsolite these combination liners proved to be! mrdot.