Registration plate abbreviations?

ruvane

ruvane

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www.techno-laser.com
I found the original (1976) registration plate for my boat (Moody 30) on board and was wondering what the abbreviations meant.

It says:
O.N. 700996 R.T. 7 39/100

I assume the last bit is the Royal Tonnage? What about the rest?

Thanks.
 
It can't be 1996 - I have the builder's certificate from 1976, so I think Official Number seems correct.

However, 7.4 tonnes seems too heavy as the certificate says something about tonnage 4.5. Can it be 4.5 empty? 3 Tonnes of water, diesel and tools seems over the top, even accounting for a few crates of beer!
 
Agree, O.N. - Official number RT = Registered Tonnage

The O.N. number for the Moody 30 is just a sequential number from the registry. I bet Moody wish they had made 700 Moddy 30's in 1976! and as the plate was from 1976 I don't think 1996 would be part of the number.
 
RT is the calculated tonnage by volume and is a bit complicated to explain from memory do a Google for RT calculations, sure it would be most interesting,start with Board of Trade etc.
 
RT = Yacht tonnage, a number relating to cubic volume computed from the beam and the length of the vessel, less the volume of any machinery compartments and bosun's stores.

It was all about cargo capacity, how many barrels or tuns would fit inside.

My boat is RT 6.75 Actual weight 2.5

The length was from the stock to stem, ie. not including bow sprits or anything behind the rudder post. Which explains the ridiculously overhanging stern designs of yesteryear.

In yachts the RT was often inflated to make your boat sound bigger, whilst in merchant ships who pay harbour dues by RT, the figure was reduced by leaving as many upper deck walkways etc, even parts of the bridge, open to the elements.

Nowadays I think things are counted differently, certainly with yachts its all LOA. which never seems to include the windvane or prodruding pulpit when paying at marinas.

All a load of bollards really
 
[ QUOTE ]
RT is the calculated tonnage by volume and is a bit complicated to explain

[/ QUOTE ] Gross registered tonnage is the volume of all enclosed space at 100 cu ft to the ton. It's further complicated by nett registed tonnage being the gross tonnage less the space occupied by engines, fuel, stores, crew accomodation and other space necessary for the operation of the ship.

Complicated even further by the existence of Thames tonnage for pleasure craft calculated from (L-B) x B x ½B / 94.

I cannot describe my sources as authorative but I undersatnd it is all explained well in the Oxford Dictionary (Encyclopaedia ?) of The Sea
 
Re: Reply to Nordic ranger

Sorry Nordic Ranger, don’t think it has anything to do with what the boat will carry, after all if it was carrying 7 39/100 tons that would be equivalent to 7390 liters of water. Think the Moody would be a few inches down on her marks. R.T. is a calculated tonnage. Long time ago we use to use Thames Tonnage. I had an Arden 4 which had a registered tonnage of 4 tons but the boat had a 50% ballast ratio and the keel weighed 1 ton so the rest of the boat weighed 1 ton. Bottom line is that the Arden 4 with a registered Tonnage of 4 tons actually weighs 2 tons.
 
Re: Reply to Nordic ranger

[ QUOTE ]
Sorry Nordic Ranger, don’t think it has anything to do with what the boat will carry

[/ QUOTE ] Oh yes it does at least historically that was exactly what it was all about.

The word tonnage has been handed down from the days when dues were collected from vessels carrying wine in "tuns" or "tun barrels". A tun is a recognised wine measure of 252 gallons.

So the tonnage of a ship was a figure indicating how many tuns of wine could be carried.

Different countries developed different rules for assessing registered tonnages but an internationally agreed method came into force in July 1982. For British registered yachts under 45 ft, however, new rules have been applied since 1 June 1975 to calculate just one figure, rather than gross tonnages and net tonnages, and it is that which is the Registered tonnage.
 
(another) Reply to Nordic ranger

Brought to you by the misinformation super highway!

"Hi, O.N. = Order No. and it translates to 700 built 9th month 1996."

In some circles this is also known as the Official Number.

"7 and 39/100 tonnes refers to the maximum tonnage that this boat is allowed to carry, and not to the weight of the boat its self. "

Also known as how to sink your boat if a small wave comes. Others have described this quite adequately.
 
[ QUOTE ]

I cannot describe my sources as authorative but I undersatnd it is all explained well in the Oxford Dictionary (Encyclopaedia ?) of The Sea

[/ QUOTE ]

It's "The Oxford Companion to Ships and the Sea". Highly recommended, but one of those books that you pick up to look for a minor item, then put down about three hours later having looked at a few dozen (or hundreds) of others. Put it on your Christmas list.

Oh, yes, it has just over a page on "tonnage", starting with a tax first levied by Edward I in 1303 and ending with the International Convention of 1982. And on the way I learnt about tidal power, tuns, timenoguys, timoneers and tjalks.
 
[ QUOTE ]
"The Oxford Companion to Ships and the Sea".

[/ QUOTE ] Thats the one, thanks
 
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