Sizing Chain... Again

[a64pilot]

If your within an inch or two of spec draft, surely you can't be more than 100% overweight?

[Cheechako]

My guess is the travelift you were on was way out of spec.

[Greg4cocokai]

On our last 2 haul outs- in Fiji they said we were 51 tons! In Thailand we were 31 tons. I checked with them on both in and out. I'm pretty sure we're closer to the 31! ?????

[natew]

Ok then. If I work backwards with a prop calculator based on my max speed, engine RPM, known prop pitch and dimensions, blades, etc.. IN THEORY that puts the boat at about 12000 lbs. I think that puts me more within the range of the 5/16 chain.

[FSMike]

My 40' Norman Cross trimaran has a design displacement of 8500 pounds. Even allowing for it having been "cruiserfied", I'm sure it still weighs less than half your 22,000 pound figure.

I would guess that your keel was probably designed by Norman Cross. Many other trimaran designs, notably Pivers, had keels of his design added. His trimaran keels were lateral resistance devices only, and as such did not have any added weight for ballast.

My boat uses a 33 pound Rocna with 50' of 5/16 HT chain as its primary ground tackle. Works well around the east coast USA and the Bahamas.

[natew]

Thanks everyone. 5/16 it is.