What I conclude about RG 65 keel and bulbs is that I need choose both correctly because I can penalize the displacement. With this figure we see this clearly:
Considering that I can have a efficient keel with 0.5 m (and upper?) we can see that:
– never use bulb with 400g weight with keel less than 0.375 m
– never use bulb with 500g weight with keel less than 0.400 m
Yes, have the intermediary bulb weights.
Beside the fact that we do not have exactly the sails moments exists what we have nowadays: a minimum bulb and a minimum keel and a maximum bulb and a maximum keel (efficient ?) and with this alert we are with more data to choose the better. Choose the wrong bulb weight or a wrong keel height is penalize the displacement and by consequence the resistance.
And I see that the goal is do a hight efficient big keel, that will lead to lower weight bulb and lesser resistance.