# help on maths!

Discussion in 'Boat Design' started by bevan, Jan 20, 2004.

1. Joined: Jan 2004
Posts: 16
Likes: 0, Points: 0, Legacy Rep: 10
Location: Wales

### bevanJunior Member

Can anyone tell me the equation to work out the centre of effort.

thankyou

2. Joined: Jan 2003
Posts: 190
Likes: 6, Points: 0, Legacy Rep: 52
Location: SF

### nicoSenior Member

Which one? and for what calculation?

*for lead: centre of effort of the sails is often the centre of area of mainsail + foresail
the same for appendages (or sometimes 1/4 chord)

*for appendages in general (before stall) 1/4 chord is a good estimate
*for sails: varies in a big range

3. ### fhjgjgbwGuest

er

hi everyone i like boats

4. Joined: Oct 2004
Posts: 1,260
Likes: 148, Points: 73, Legacy Rep: 1806
Location: South Africa

### Wynand NRetired Steelboatbuilder

Hi Bevan,

I assume you mean the centre of effort of sailplan relative to centre of effort of lateral plane. This is generally termed lead, which is a percentage of the waterline. Usually the CE of sails leads the CE of lateral plane. Remember, different types of boats and rigs required different values of lead.

The CE of sails are usually the combined CE of both the mainsail and 100% fore triangle. This is usually calculated geometrically, but there is a rather primitive but quite accurate shortcut. Go about as follows:

Draw your sailplan (main & 100% foretriangle) as per plan on stiff paper to scale. Cut out the sailplan, balance over sharp edge, mark the line. Repeat randomly and where all the lines crosses, that is the combined CE of sailplan.

CE of lateral plane is the centriod of the lateral plane, meaning the underwater profile with keel, excluding rudder. There is some disputes amongst designers about the rudder. Some includes the rudder with the hull and keel, others not.
Conventially the same primitive shortcut as for the sailplan can be used to establish the CE of the lateral plane. Otherwise it can be found geometrically or with fancy software.

Bevan, this is not the mathematical model you had in mind but a simple method for the curious and beginner alike.

Fair winds

Wynand Nortje

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.