Weigh carrying capacity of SM


karkauai
 

Hi all.
We are going to carry supplies to Caribbean from Ft Lauderdale to hurricane stricken islands this winter. I'm wondering how much weight I can take on safely. Loaded with all our supplies and provisions, Kristy sits about 1 1/2 inches above the original waterline in the stern, and 4 inches above waterline at the bow.

Can I load her to that waterline? If I go above it, the engine and generator exhausts will be below the water. That doesn't seem like a good idea. If that is ok, what other considerations are important if I load her another inch or more above the waterline?

I was going to carry one pallet (40" x 40" x48") on the foreword cabintop and another one or two broken down below decks as carrying capacity allows. I don't know the weight of the pallets yet.

Any thoughts?

Thanks andMerry Christmas!
Kent
SM 243
Kristy


greatketch@...
 

Kent,

I suspect when you describe your boat's current waterline status you are looking at the painted waterline on the hull.  That is not the waterline as drawn for the boat on her design drawings.  

When we picked up Harmonie she was almost empty of gear.  I saw the painted waterline was significantly higher at the bow then the stern. About 3 inches if my memory is correct.  This struck me as very odd for an unloaded boat.  So I measured the distance from the water to the gunwale at bow and stern and compared to the architects drawing.  She was spot on her correct fore and aft trim as per the drawing.

Take away lesson:  The painted waterline is not necessarily where she should sit!  If you were to load our boat until the water at the bow was even with the painted line, you would have water at the top of the bowthruster well, and maybe over it!  Note that I have NOT done this measurement on ANY other Amel.  It is possible it only applies to #160.  Amel might have changed the painted waterlines at other times, or a previous owner might have changed yours!  

I do not know if Amel painted the waterline higher at the bow on our boat as an aesthetic thing, or just got it wrong, but it's definitely not where the boat should sit in the water.

As for how much you can carry...

A Super Maramu has a LWL of 41.3 feet, a Waterline Beam of about 14.5 feet...
A SM has a LWL Area of (very roughly) 0.67 *41.3* 14.5 ~ 400 sq feet
So to sink her a extra inch overall will take 400 * 5.33 ~ 2,100 lbs or close to one ton. 
That's actually a pretty conservative number for a SM because as she settles deeper her LWL becomes a bit longer. 

So how deep you can take her...  I don't have a good answer.  

If loaded so the heavy stuff was down as low as possible and not concentrated at the ends of the boat, I'd guess two inches (two tons) would be a conservative number.  

Carrying that much weight as "deck cargo" would certainly reduce the stability of the boat. But I have no idea if it would be dangerous because I don't know her designed center of gravity or metacentric height.  For a real answer I think you'll have to talk to a naval architect, or ask Amel.

Honestly, my suggestion would be to take the money you would spend on the fuel for that trip and donate it to have the material shipped commercially to the nearest working port.  

Bill Kinney
SM160, Harmonie
Key West, FL


---In amelyachtowners@..., <karkauai@...> wrote :

Hi all.
We are going to carry supplies to Caribbean from Ft Lauderdale to hurricane stricken islands this winter. I'm wondering how much weight I can take on safely. Loaded with all our supplies and provisions, Kristy sits about 1 1/2 inches above the original waterline in the stern, and 4 inches above waterline at the bow.

Can I load her to that waterline? If I go above it, the engine and generator exhausts will be below the water. That doesn't seem like a good idea. If that is ok, what other considerations are important if I load her another inch or more above the waterline?

I was going to carry one pallet (40" x 40" x48") on the foreword cabintop and another one or two broken down below decks as carrying capacity allows. I don't know the weight of the pallets yet.

Any thoughts?

Thanks andMerry Christmas!
Kent
SM 243
Kristy