Anthony
Jun 20, 2003, 04:01 AM
Umi_Ryuzuki <Umi_Ryuzuki.ounak@rcgroups.com> wrote in message
news:Umi_Ryuzuki.ounak@rcgroups.com...
> Heeling Moment
>
> The heeling moment (HM) is defined as the pounds of wind pressure per
> foot squared multiplied by the sail area (SA) in square feet multiplied
> by the heeling arm. The heeling arm is the distance from the center of
> effort (CE) to one half of the draft of the boat.
Unfortunately this formula isn't as much use on models as on full-size craft
because of wind sheer. The wind speed varies almost linearly with height up
to a level well above any model yacht, consequently the actual centre of
effort will be much higher up the sail on the model compared with the real
thing. This is one reason why scale model yachts don't sail properly unless
they have much deeper keels to give a greater righting moment.
Anthony.
news:Umi_Ryuzuki.ounak@rcgroups.com...
> Heeling Moment
>
> The heeling moment (HM) is defined as the pounds of wind pressure per
> foot squared multiplied by the sail area (SA) in square feet multiplied
> by the heeling arm. The heeling arm is the distance from the center of
> effort (CE) to one half of the draft of the boat.
Unfortunately this formula isn't as much use on models as on full-size craft
because of wind sheer. The wind speed varies almost linearly with height up
to a level well above any model yacht, consequently the actual centre of
effort will be much higher up the sail on the model compared with the real
thing. This is one reason why scale model yachts don't sail properly unless
they have much deeper keels to give a greater righting moment.
Anthony.