Hull speed?

[dunedin]

Bulbous bows allow for an increase in speed of about 15% in a very narrow relative speed range of between 0.6 and 1 ( Sqr root DWL x speed factor). As sailing yachts operate at the variance of the wind, a bulbous bow makes no sense. Freighters tend operate pretty much precisely in this speed range.

….

One yacht design tried the bulb bow - Coronet Elvstrom 38 - Coronet Elvestrom 38 for sale Spain, Coronet boats for sale, Coronet used boat sales, Coronet Sailing Yachts For Sale Coronet Elvstrom 38 - Apollo Duck

Think there is one at Largs. No idea if works or not, but must catch a lot of kelp and pot buoys

 

[Chiara’s slave]

One yacht design tried the bulb bow - Coronet Elvstrom 38 - Coronet Elvestrom 38 for sale Spain, Coronet boats for sale, Coronet used boat sales, Coronet Sailing Yachts For Sale Coronet Elvstrom 38 - Apollo Duck

Think there is one at Largs. No idea if works or not, but must catch a lot of kelp and pot buoys

I doubt bulb bows will catch on in the racing community.

 

[Laminar Flow]

Yes, the Elvstrom is a motorsailer and the bow's performance advantage is (near enough exactly) between 3 and 5 kts. If you are happy pooteling along at 4 kts (average) then that is ok.

There are other options. The CP on our tub is 0.6 with an optimum relative speed of 1.25. This CP offers a 20% reduction in resistance at this speed over a lower CP of say 0.55, which would be more common. The penalty for this at lower speeds is easily overcome with more sail; the reduction in windward capability I can live with. It also goes a long way in explaining why such a supposedly ungainly craft as ours, can indeed sustain speeds of well over 8 kts under sail. This, in spite of a D/L of 360.

 

[Chiara’s slave]

Yes, the Elvstrom is a motorsailer and the bow's performance advantage is (near enough exactly) between 3 and 5 kts. If you are happy pooteling along at 4 kts (average) then that is ok.

There are other options. The CP on our tub is 0.6 with an optimum relative speed of 1.25. This CP offers a 20% reduction in resistance at this speed over a lower CP of say 0.55, which would be more common. The penalty for this at lower speeds is easily overcome with more sail; the reduction in windward capability I can live with. It also goes a long way in explaining why such a supposedly ungainly craft as ours, can indeed sustain speeds of well over 8 kts under sail. This, in spite of a D/L of 360.

Some of the most unlikely craft are surprisingly nippy. All down to the design brief. We too overcome our light air deficit with sail power. A tall rig, roachy square top main and big kite, and a code 0. We need 8kn of wind to plane. Our design trade offs are limited accommodation and a final limit to ultimate stability. Horses for courses. A 1/4 tonner usually drags a massive sternwave to show off it’s underwater profile. Plus that tiny transom Smaller than ours, with the ability to turn on a sixpence, whether you intended to or not. Quick in medium airs though.