Topics

Gross tonnage on SM

Patrick McAneny
 

We checked in yesterday here in Montserrat and were charged ,based on gross tonnage,this has happened on other island as well. I think we are paying more than we should,because I believe our ship papers are wrong. Our papers show gross tonnage to be 58 GRT ,net 46 NRT. That sounds high to me,could someone confirm the correct tonnage?
Thanks,
Pat
SM Shenanigans

Richard Colebatch
 

Patrick,

Sailboat data below.

Rgds
Richard. FAO

Hull Type:
Wing Keel
Rigging Type:
Masthead Ketch
LOA:
52.49 ft
LWL:
41.34 ft
Beam:
15.09 ft
S.A. (reported):
1,302.00 ft2
Draft (max):
6.73 ft
Draft (min):
 
Displacement:
35,274 lb
Ballast:
12,125 lb
S.A./Disp.:
19.45
Bal./Disp.:
34.37
Disp./Len.:
222.89
Construction:
FG
Ballast Type:
Iron
First Built:
1989
Last Built:
1998
# Built:
237
Builder:
Amel (FRA)
Designer:
Henry Amel & J. Carteau
Website:

Craig & Katherine Briggs SN 68 Sangaris Tropic Isle Harbor, FL
 
Edited

Pat,
Remember that Gross and Net Tonnage on your Ship's Papers IS NOT weight.  It is a measure of volume of cargo a ship can carry that goes back to setting tax rates on shipping. Net is total less machinery space conceptually, but the formulas are a bit arcane. You can get more info on the USCG or NVDOC web pages, which has an easy way to get an approximate measure.

Yours sounds exactly right - my Santorin, which weights some 22000 pounds, or 11 tons has a Gross Registered Tonnage (GRT) of 31 and 28 Net. Again, Registered Tons are cubic volume, not weight.
Cheers,
Craig Briggs, SN68 Sangaris

 
Edited

Pat,

Your SM Gross Tonnage is: 27GRT
Net Tonnage is 24GRT
You should get your Certificate of Documentation changed to below.

Best,

CW Bill Rouse
720 Winnie St
Galveston Island, TX 77550
+1(832) 380-4970

On Wed, Mar 13, 2019, 7:10 AM Patrick McAneny via Groups.Io <sailw32=aol.com@groups.io> wrote:
We checked in yesterday here in Montserrat and were charged ,based on gross tonnage,this has happened on other island as well. I think we are paying more than we should,because I believe our ship papers are wrong. Our papers show gross tonnage to be 58 GRT ,net 46 NRT. That sounds high to me,could someone confirm the correct tonnage?
Thanks,
Pat
SM Shenanigans

Jamie Wendell
 

Wow Pat that seems really high. I see Bill responded as well, but I can tell you with my Amel 54 my documentation shows 23 and 20 respectively. I would guess the 54 is a bit heavier and probably a bit more voluminous.
So I am surprised either way - maybe I am lucky? I do know that I weigh in at about 47,000 pounds.
Was nice to see you in Les Saintes.
Jamie
Phantom, A54

Ian Park
 

Craig
My Santorin has a big brass plate that says net tonnage is 15 and 1/4 and gross tonnage is 18+. But the spelling is tons.
I know it refers to capacity, but I don’t know if there is a difference in where it was measured.
In metric tonnes the Santorin is 10 tonnes.
I give up !
Incidentally my Part 1 registration has the boat length at 12.3 metres ( rather than the 14 that it is). It has saved me money several times when a marina has just asked for my registration certificate!

Ian

Ocean Hobo

 

Pat,

The terms Gross Tonnage and Net Tonnage are terms that were invented by I believe the British Royal Navy. They are calculated numbers that should tell you how much cargo a vessel is capable of carrying. These terms have little to do with weight of the vessel. 
 
Best,

Bill Rouse
720 Winnie St.
Galveston, Texas 77550
832-380-4970



On Wed, Mar 13, 2019 at 7:10 AM Patrick McAneny via Groups.Io <sailw32=aol.com@groups.io> wrote:
We checked in yesterday here in Montserrat and were charged ,based on gross tonnage,this has happened on other island as well. I think we are paying more than we should,because I believe our ship papers are wrong. Our papers show gross tonnage to be 58 GRT ,net 46 NRT. That sounds high to me,could someone confirm the correct tonnage?
Thanks,
Pat
SM Shenanigans

heinz@quetzal.berlin <heinz@...>
 

My sm2000 says 14t netto 16t groß
Fair Winds
Heinz sm2000 292

Am 13.03.2019 um 11:40 schrieb Ian <parkianj@...>:

Craig
My Santorin has a big brass plate that says net tonnage is 15 and 1/4 and gross tonnage is 18+. But the spelling is tons.
I know it refers to capacity, but I don’t know if there is a difference in where it was measured.
In metric tonnes the Santorin is 10 tonnes.
I give up !
Incidentally my Part 1 registration has the boat length at 12.3 metres ( rather than the 14 that it is). It has saved me money several times when a marina has just asked for my registration certificate!

Ian

Ocean Hobo


 

Heinz,

That is the weight of the vessel, not the GT (Gross Tonnage) or NT Net Tonnage.

Unfortunately, most countries use GT and NT on recreational vessel registration, confusing most of us.

Best,

Bill Rouse
720 Winnie St.
Galveston, Texas 77550
832-380-4970



On Wed, Mar 13, 2019 at 3:24 PM heinz@... <heinz@...> wrote:


My sm2000 says 14t netto 16t groß
Fair Winds
Heinz sm2000 292


> Am 13.03.2019 um 11:40 schrieb Ian <parkianj@...>:
>
> Craig
> My Santorin has a big brass plate that says net tonnage is 15 and 1/4 and gross tonnage is 18+. But the spelling is tons.
> I know it refers to capacity, but I don’t know if there is a difference in where it was measured.
> In metric tonnes the Santorin is 10 tonnes.
> I give up !
> Incidentally my Part 1 registration has the boat length at 12.3 metres ( rather than the 14 that it is). It has saved me money several times when a marina has just asked for my registration certificate!
>
> Ian
>
> Ocean Hobo
>
>
>



Patrick McAneny
 

I should have mentioned that I knew tonnage was not the weight of the boat ,but a volume measurement . Still it seemed high and apparently that is the case and I will have it changed. Thanks for the correct numbers.
Pat
SM Shenanigans

Beaute Olivier
 

Hello,

a vessel's tonnage is indeed a volume (how much can this vessel carry). This international value is now expressed without unit's name. 
It was previously expressed in tons or tonneaux (for France). This "ton" is not equivalent to a metric ton which is the weight of 1000 liters of water, but it is equivalent to 100 cubic feet which is around 2.837 cubic meter 

Every country's authority has its own calculation for tonnage (from length, beam and inside height).
This is why the tonnage of a Super Maramu is 30.14 in France and is, for instance 33.24 (gross tonnage) and 23.35 (Register tonnage) in UK.
It will for sure be different for Australian or NZ or US flag.

However, Pat's tonnage seems high.

Olivier.

On Wednesday, March 13, 2019, 10:40:10 PM GMT+1, Patrick McAneny via Groups.Io <sailw32@...> wrote:


I should have mentioned that I knew tonnage was not the weight of the boat ,but a volume measurement . Still it seemed high and apparently that is the case and I will have it changed. Thanks for the correct numbers.
Pat
SM Shenanigans

Craig & Katherine Briggs SN 68 Sangaris Tropic Isle Harbor, FL
 
Edited

Pat,
Here's a link to the US Coast Guard's Simplified Measurement Guide I mentioned.USCG Simplified Tonnage Guide
You can use this for vessels under 79 feet. As Olivier points out different countries have different methods.

You should work it out yourself, but, for your SM it would be ABOUT the following (I had to guess at a couple of numbers but you can fine tune it.
GRT = (Hull volume + Deckhouse Volume) / 100
Where Hull Volume = S x K x L x B x D and Deck Structure Volume = Ls x Ds x Bs 
L, B and D are overall length, breadth and depth, but depth is measured from the deck edge to the bottom of the keel.
You consider the Deck Volume to be 0 if it is less than the hull volume, which it is.
S is a Shape factor which is 0.5 for sailboats. K is a Keel factor which is 0.75 for our shape of sailboat.

So, let's use Richard Colebatch's posting for your SM dimensions. That is 52.49' in Length and  15.09' in Breath.
Richard shows a Water Draft of 6.73' from the bottom of the keel to the water line and let me guess another 6' of freeboard to the edge of the deck.
That would be a Depth of 11.73' (which seems about right as my Santorin's Depth is 10.5')

So the SM Gross Register Tons (GRT) would be (they say to round feet to the nearest tenth):
  S  x  K    x  L     x   B    x  D   
0.5 x 0.75 x 52.5 x 15.1 x 11.8  = 3507  / 100  = 35 GRT
Then, NRT = M x GRT, where M is a Machinery factor which is .9 for sailboats, so
NRT = .9 x 35 = 31  (you are instructed to truncate any fraction)

So, it does seem your numbers are, indeed, way high and should be more like a GRT of 35 and NRT of 31.

Bill Rouse's GRT 27, NRT 24 comes from his Documentation Certificate, I'm sure, but seems low as my Santorin is 31 and 28 and the USCG calculation above is pretty straightforward. Anyway, there are lot of other numbers in this thread that may have their origin in countries other than the US and/or may be weight based. Numbers that have fractions are definitely not US GRT/NRT, which are always whole numbers. Also, in the US the documentation is pretty much self reported with, seemingly, very little checking by the NVDOC. Whatever, your's seems high.

The US Coast Guard's National Vessel Documentation center has a super new website that it very easy to navigate and you may be able to change your numbers on-line. Check it out.

Cheers, Craig Briggs, SN68 with  GRT 31 NRT 28

eric freedman
 

Kimberlite is documented in the USA with 28 gross tonnage and 25 net tonnage.

That was provided by Amel when they had Kimberlite documented.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

From: main@AmelYachtOwners.groups.io [mailto:main@AmelYachtOwners.groups.io] On Behalf Of Craig Briggs via Groups.Io
Sent: Thursday, March 14, 2019 8:46 AM
To: main@AmelYachtOwners.groups.io
Subject: Re: [AmelYachtOwners] Gross tonnage on SM

 

[Edited Message Follows]

Pat,
Here's a link to the US Coast Guard's Simplified Measurement Guide I mentioned.USCG Simplified Tonnage Guide
You can use this for vessels under 79 feet. As Olivier points out different countries have different methods.

You should work it out yourself, but, for your SM it would be ABOUT the following (I had to guess at a couple of numbers but you can fine tune it.
GRT = (Hull volume + Deckhouse Volume) / 100
Where Hull Volume = S x K x L x B x D and Deck Structure Volume = Ls x Ds x Bs 
L, B and D are overall length, breadth and depth, but depth is measured from the deck edge to the bottom of the keel.
You consider the Deck Volume to be 0 if it is less than the hull volume, which it is.
S is a Shape factor which is 0.5 for sailboats. K is a Keel factor which is 0.75 for our shape of sailboat.

So, let's use Richard Colebatch's posting for your SM dimensions. That is 52.49' in Length and  15.09' in Breath.
Richard shows a Water Draft of 6.73' from the bottom of the keel to the water line and let me guess another 6' of freeboard to the edge of the deck.
That would be a Depth of 11.73' (which seems about right as my Santorin's Depth is 10.5')

So the SM Gross Register Tons (GRT) would be (they say to round feet to the nearest tenth):
  S  x  K    x  L     x   B    x  D   
0.5 x 0.75 x 52.5 x 15.1 x 11.8  = 3507  / 100  = 35 GRT
Then, NRT = M x GRT, where M is a Machinery factor which is .9 for sailboats, so
NRT = .9 x 35 = 31  (you are instructed to truncate any fraction)

So, it does seem your numbers are, indeed, way high and should be more like a GRT of 35 and NRT of 31.

Bill Rouse's GRT 27, NRT 24 comes from his Documentation Certificate, I'm sure, but seems low as my Santorin is 31 and 28 and the USCG calculation above is pretty straightforward. Anyway, there are lot of other numbers in this thread that may have their origin in countries other than the US and/or may be weight based. Numbers that have fractions are definitely not US GRT/NRT, which are always whole numbers. Also, in the US the documentation is pretty much self reported with, seemingly, very little checking by the NVDOC. Whatever, your's seems high.

The US Coast Guard's National Vessel Documentation center has a super new website that it very easy to navigate and you may be able to change your numbers on-line. Check it out.

Cheers, Craig Briggs, SN68 with  GRT 31 NRT 28

Denise McGovern
 

CARA is USCG Documented: 26 GRT, 23 NRT

Denise McGovern
s/v CARA
SM #440
Chesapeake Bay

Craig & Katherine Briggs SN 68 Sangaris Tropic Isle Harbor, FL
 
Edited

Here's what's been reported on this thread.
  • Denise on CARA, a SM, has 26GRT  /  23NRT
  • Eric on Kibelite, a SM  has 28 GRT / 25 NRT on his US Documentation but that was done by Amel (French numbers?)
  • Bill Rouse reports SM as 27 GRT / 24 NRT
  • Craig's Sangaris, a SN has 31 GRT / 28 NRT
  • Ian on Ocean Hobo, a SN  reports 18+ "gross tons" and 15 1/4 "net tons"  (definitely not USCG format); plus 12.3M length, not the 14M actual. 
  • Olivier reports SM as 30.14 in France, 33.24 Gross / 23.25 "Register" in England
  • And the smallest boat of all is Jamie's Amel 54 at 23 GRT and 20 NRT
So there you have it - in the Amel fleet, the biggest boat is the Santorin, the Super Maramu is somewhat smaller and the tiniest one of all is the Amel 54.
My only definite conclusion is that the government bureaucrats live by "garbage in - garbage out" with no concern for accuracy.  Frankly, in the recreational market the number really is of little consequence and it's good our tax dollars are not going toward trying to make this accurate. 
I do have to give it to Ian for saving on his dock fees with that short Santorin, although I have heard that fiberglass shrinks a lot when immersed in water.

Cheers around,
Craig Briggs SN68 Sangaris 

 

This thread is as long as an anchor thread.😀

Best,

Bill Rouse
720 Winnie St.
Galveston, Texas 77550
832-380-4970



On Thu, Mar 14, 2019 at 11:46 AM Craig Briggs via Groups.Io <sangaris=aol.com@groups.io> wrote:
Here's what's been reported on this thread.
  • Denise on CARA, a SM, has 26GRT  /  23NRT
  • Eric on Kibelite, a SM  has 28 GRT / 25 NRT on his US Documentation but that was done by Amel (French numbers?)
  • Bill Rouse reports SM as 27 GRT / 24 NRT
  • Craig's Sangaris, a SN has 31 GRT / 28 NRT
  • Ian on Ocean Hobo, a SN  reports 18+ "gross tons" and 15 1/4 "net tons"  (definitely not USCG format); plus 12.3M length, not the 14M actual. 
  • Olivier reports SM as 30.14 in France, 33.24 Gross / 23.25 "Register" in England
  • And the smallest boat of all is Jamie's Amel 54 at 23 GRT and 20 NRT
  •