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BCC Balance
Posted by: Vixen (IP Logged)
Date: October 10, 2018 05:19AM
Category: Miscellaneous

I have some questions on weight and balance for BCC's.

I'm rebuilding Vixen, so I have a rather clean sheet of paper. When I sailed her from Seattle, the bow seemed a little heavy. At rest the bobstay fitting on the hull was touching the water. Vixen has 4200# encapsulated lead for ballast. According to Craig Johnson, builder, their calculation were off 5% and ballast was moved back slightly on later boats. Vixen currently has no movable ballast in the bilge and has a light 215# 2GM20F Yanmar engine. I understand the early BCC were designed and fitted with a 280Kg or 860# 2cyl Sabb diesel. Vixen has two 35 pound bow anchors and 330 ft of 5/16 chain so roughly 425 pounds of ground tackle up in the bow. Balancing all that she has a powerful Gaff rig with a heavy stiff hollow spruce mast.

I'm a dinghy sailor so I know weight and balance is important. Should I try to keep her light? or add ballast and go for power? Do BCCs like weight forward or back?

Rich
Portland Oregon
Vixen BCC #2


Re: BCC Balance
Posted by: Bil (IP Logged)
Date: October 12, 2018 01:31AM
Category: Miscellaneous

I think both trim and displacement are important.

Of the two, I think trim is the more important. Trim in the sense of the hull NOT sitting on a waterline parallel to her design waterline. Trim in the sense of whether she trims by the bow (is sitting bow down) or stern (stern down).

I reckon a BCC carries mass (added displacement) surprisingly well, within reason. At the design waterline, sinkage (PPI = pounds per inch of immersion; also measured in kg/cm and Tonnes/cm) is 909 pounds per inch.

Most all BCCs in live-aboard mode or departure mode sit with the waterline above the design waterline. Our experience is not unique. Zygote has crossed oceans and sea with her LWL inches above the design waterline. Others have done the same.

I further reckon, based on my experience with Zygote and reports from others, that the worst you can do is stow so a BCC trims bow down. I think dinghy experience is that trimming by the bow can be a slight advantage on a downwind run, but I've not found that on Zygote. Trimming by the bow is I think a disadvantage on a reach and probably on any point of sail in choppy waters.

BCC 116 Zygote,
Scarborough Marina, Moreton Bay, Queensland, Australia

Re: BCC Balance
Posted by: svshaula (IP Logged)
Date: October 12, 2018 07:21PM
Category: Miscellaneous

I wonder if the weight of a gaff rigger's wooden mast, boom and gaff is significantly greater than the usual Al mast and boom? In any case, I think it's very important to have a buoyant bow. We sailed alongside gaff rigged BCC Chautauqua between PV and La Cruz, Mexico. Instead of rising to the oncoming seas of several feet like Shaula did, Chautauqua plowed into them, slowing significantly. She had 2 anchors on her bow, the main one a 35 lb CQR, and a spare plow of about 45 lbs. Both BCCs were fully loaded for crossing the Pacific. I'm sure the extra anchor contributed, but other factors could have been involved. Maybe the weight of the spars? I don't know where the chain locker was located. Chautauqua had a wooden main cabin which must have weighed significantly more than the standard FG cabin.

I would definitely remove the spare 35 lb CQR from the bow and also move anything heavy that's stored way forward. You might consider replacing 100ft of chain with 100ft of line. We've carried 235ft of 5/16" BBB while cruising through the Pacific, NZ, Australia and Pacific NW without needing more. We do have 2 spare lengths of 50ft, 200ft of line and a spare 35 lb CQR (stored in the forepeak's bilge.

Re: BCC Balance
Posted by: Vixen (IP Logged)
Date: October 12, 2018 11:52PM
Category: Miscellaneous

Wow, Thanks for all the the input, I think I have a plan of action. The spruce mast and spars are I'd estimate about 50% heavier, which shifts center of gravity up and forward. The deck and cabin are wood also so even with AYC decks I'd estimate this also moves center of gravity up. Ballast is also light at 4200 Lbs as opposed to 4600 pounds on the later BCCs so COG again is raised.

My thought is to add about 400 pounds of lead in the bilge below the engine in the bilge. It is an area totally inaccessible so I'd encapsulate it for safety in a knock down. Batteries are also something that I'm thinking of moving from above and aft of the engine, to forward and under the floorboards again secured. She is going to explore BC and Alaska I'm thinking 150' of chain and 150' of line will lighten up the chain locker a lot. Spare sails are going in the bow to keep it light up there. I'm also thinking maybe a stern chain locker through a PVC pipe that will have 80' of chain and 120' of line and another emergency 80' length of chain stored under the engine in the bilge. Spare anchors and heavy equipment goes back in the lazarette. This should bring the center of gravity back and aft.

I've raced keelboats where we'd put all our movable ballast, crew and gear up forward. In theory, it lengthens the waterline increasing hull speed and lifts the stern, reducing drag. BCC's having no bow overhang and the stern doesn't appear to drag, probably no speed advantage to having weight forward. I can see how it would be really bad in big waves too.

Thanks for the info on Chautauqua, sounds like a very similar build.

Re: BCC Balance
Posted by: svshaula (IP Logged)
Date: October 13, 2018 01:23AM
Category: Miscellaneous

I should have mentioned that it was embarrassing because we wanted to sail along side Chautauqua with our good friends Cris and Dick. At the time I thought it was due to that extra anchor, but guess there could have been other factors.

Maybe we'll cross paths with you next summer? We spend the summer in the greater Desolation Sound area.

Re: BCC Balance
Posted by: MCilenti (IP Logged)
Date: October 13, 2018 01:40AM
Category: Miscellaneous

Bil,

Just sent you a PM on a completely different topic.
Mike



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