I have been spending way too much time researching materials online, but the end result is that I am again confused on how to estimate the weight of a 50 ft cruising harryproa. I have gone through and added up the hull, bulkheads, furniture, hardtop, cockpit, bunks, etc, etc and come up with 2100 sq ft. This does not include the rig, crossbeams or rudders, since I don't know how to calc that.

Anyway, I then research the core material (pretty much all of them are 80Kg/m3), which translates to 0.3 lbs/sq ft for 2/4" (20mm) core. Add in 2 layers of 18 oz/yd2 fiberglass (1 top and 1 bottom) and an equal weight of resin and I get 0.8 lbs/sq ft total. Add 20% for fillets, bog, etc, and it comes out pretty much exactly 1 lb/sq ft.

I add in my batteries, outboard engines, refrigeration, water and fuel tanks, instrumentation, ground tackle, etc and get another 1500 lbs.

With schooner rig, I would estimate each mast/sail/boom combo at about 500 lbs, so that is 1000 for the rig.

I am now up to 2100 lbs for structure + 1500 lbs equipment + 1000 lbs rig = 4600 pounds.. supposedly only missing the crossbeams and rudders.

I am happy with that. But then the urge to do a reality check comes in and I look at Rare Bird at 6,720 lbs, and it doesn't have a 10' x 12' bridgedeck.

So, what am I doing wrong? At about 5000 lbs and 1000 sq ft of sail, this should be a screamer, but if it is 10,000 lbs with the same sail area, that is a totally different boat!

 I would probably be safe by just taking Rare Bird and adding a couple thousand pounds, but I actually want to be able to do this stuff. Help! 

Thanks,

- Gardner Pomper

York, PA

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