Benefits of a bigger boat?

[Adelie]

Originally Posted by donoharm

We're talking like a 1 knot difference then for a 35 vs 40 foot boat based on this formula then, right?

https://www.boats.com/reviews/crunch...d-boat-length/

There might be a 1kt difference in hull speed based on waterline length (lwl) but average daily distance is likely to be significantly different.

The best formula for Daily Average Milage I've found is

Daily Average Mileage = 24*(2.62 + 0.066*SA/D+ 0.051*LWL ).

You mentioned Ericson
E-35.1: lwl=24.08' SA/D=16.7 DAM=118nm/d PHRF=158nm/d
E-39.1: lwl=30.00' SA/D=16.6 DAM=127nm/d PHRF=183nm/d

So according to DAM there's a 9nm/d advantage for the extra 6' of waterline length. In reality there are a number of other factors that affect baot speed that DAM does not account for:
Actual hull shape
Actual sail plan
Ballasting
draft
Crew effort expended sailing

PHRF takes these into account but misrepresents sailing conditions:
ie races are called for lack of wind or for storm conditions so there is not data from sailing in those conditions when the PHRF ratings are calculated.

I would say that DAM provides a good ballpark estimate for what kind of daily milage to expect but PHRF gives a better comparison between boats.
Based that I would expect those two Ericson boats to get about 123nm/d but the E-39 will be about 18nm/d faster than the E-35.1, about 0.75kt.

So the E-39 is 18nm/d faster, what's the tradeoff?
The E-35.1 is built heavier for it's length and beam than the E-39 and it presumably more durable.

What about the E-35.2:
E-35.2: lwl=25.83' SA/D=16.7 DAM=122nm/d PHRF=167nm/d
So the performance gap has significantly narrowed, you are looking at about a 0.5kt difference but the boats are built just about as heavily as each other.

[Pizzazz]

My view is that there is a step change at 30 ft, 40 ft and 50 ft. Below 30 ft you have no standing headroom and that is super important. As you go up in size from 30 ft you get bigger cabins and saloon but it is all marginal. Many newer boats waste a lot of space with the anchor locker and the swim step, so you may find a 37 footer having similar space to a 31-32 footer in the cabin. At 40 ft and above you typically get a second head (nice but not essential for cruising) and bigger cabins to the point that you can actually use the cabin for more than just sleeping. At 50 ft you get a three cabin layout that may be important if you have a number of kids/guests. Very much like a three bedroom apt.

Space is a personal preference and only you can decide how much you need.

In terms of passage making a bigger boat is more stable and faster other things being equal. However other things are rarely equal. Passaging making speeds depend first on wind, then on your willingness to put up (and keep through the night) a large sail plan and only then on waterline. Most of the time winds will be around 15 knots. A small boat will maintain hull speed easily. A larger boat needs a bigger sail plan/spinnaker to maintain hull speed at 15 knots and few people are willing to keep that up at night. So, in reality passage making speeds are not that different but I am being somewhat partial to smaller boats here.

Next, while it is true that larger boats handle bigger seas better, you should put this in perspective. There is a great video on the web showing a cruiser next to an aircraft carrier in storm conditions. The cruiser is jumping up and down while the aircraft carrier is stable. So, it is all relative. Up to force 5-6, there would be much difference in comfort. At force 7, a 40 footer will be more comfortable. At gale and above all recreational boats are uncomfortable. So, how often do you sail in force 6-7 vs. the increased cost of upkeep and the lower performance in light winds? It is a personal choice.

In terms of storage and systems, it is a fallacy that today you need that much space or weight carrying capacity. You keep minimal water and run the watermaker more often. Get a second watermaker or spares as backup if worried.

Yet, if I ever go cruising full time, I would probably prefer a 50 footer vs. a 31 footer .

SV Pizzazz

[Kolchac]

Using criteria 35-45' is quite unwise. There're a lot (!) parameters to consider first, I will not even calculate them, you should educate yourself.
But if you choose the design, you have to know, that at most marinas boats bigger than 40' have much more service and storage fees per foot, so 39' and 41' - very big difference.

[rbyham]

We recently went from 31 to 36 feet and I personally feel a huge increase in comfort to the point of being surprised until I one day thought that my own size being 6"2" and about 230 just fit and moved so much better with more room. So while the argument of speed and other factors already mentioned here in our case it was my size that made a larger boat a better fit.