Conversion sail to power

[TANSL]

Of course, then?

 

[James Wellington]

I'm shocked, shocked to find that someone would just cut a mast down.
If you don't want it, have it lifted out and keep it and all its rigging and related parts intact.
You'd still want some kind of mast/boom, (maybe two booms, one forward of the mast,) if only for easy hoisting of tenders/heavy gear.
I think you'll find that a sailboat without a mast becomes a horrible rolling nightmare in anything much beyond calm conditions.
The motion can become violent, people aboard literally get thrown around like rag dolls, it ain't a smooth ride.

I suggested keeping the boom, and the retractable keel, down to 3.2meters.

 

[James Wellington]

I like the idea, but she'll probably roll like a ******* with the mast cut down. Just sayin'

Still has a retractable keel down to 3.2cmeters.

 

[jehardiman]

My opinion is that, in a hull with such rounded shapes, the wet surface of the heeled boat does not have to be very different from that of the upright boat. Therefore, the frictional resistance will not be very different.

While it is true that many older CCA era hulls are pretty much all "rounded" in section so that heel angle does not matter, most modern (say post mid 1970's when sailboats got much lighter for their length) hull forms tend to have elliptical (i.e. wider than they are deep) sections. This does two things for sailing; first it lifts a significant portion of the windward hull out of the water giving more "rounded" sailing lines while reducing the need for ballast, and second they generate an AoA to the actual direction traveled generating lift to weather to reduce leeway. Look at an IMOCA 60 hull for an extreme example of this.

On the other hand, the heeled boat will raise many more waves than the upright boat, with the consequent increase in the resistance due to wave formation, which is always greater than the frictional resistance.

Again, this goes back to the difference between modern "still water" lines and the designed "sailing" lines. Many, if not most, modern sailing hull designs have less wetted surface and larger L/B ratios while sailing than while flat; with only over-powered dinghies (such as an Aussie Skiff or 49er) which are designed the same as a planning powerboat, sailed flat.

EDIT to ADD: FWIW, a Chatam 60 has a L/D ratio of 161 and as SA/D ratio of 22...so these are not displacement cruisers, comming in well in the middle of the lightweight racing yachts.

 

[rangebowdrie]

Many of the modern hull forms are quite "flattish" than any of the older boats, and in plan view they appear more as arrowheads.
That shape wants to be sailed as upright as possible. As they heel the waterplane shape becomes grossly asymmetrical, the CB while moving to leeward also moves aft, and the bow wants to dive.
Their hulls exbibit great initial stability due to hull form but give-up ultimate stability.
They also give-up seakindlyness/comfort and require the crew to be much more "on top" of the situation, they're "high strung". Performance has a high price tag.
Then look at a 12 Metre from the '60s, they heel fairly easily in the beginning, but kind of "hit the wall" where further heel angle meets very high resistance.
Of course, having a ballast ratio of perhaps 60% or more makes capsize almost impossible.

 

[TANSL]

@jehardiman, I'm not going to discuss your comments because I don't have any data on the boats you're referring to. I just want to point out that my comments refer to the boat shown by the OP, whose shapes have little to do with the shapes of current sailboats, which is not a racing boat and of which, not of it but of similar boats, I have enough data to have the opinion I have expressed.
I also want to comment that, in my opinion, current boats are more concerned with achieving shapes that give rise to greater righting moments, with bows that avoid the formation of large waves and that friction resistance is less of a concern for them (I'm not saying that they forget about it). The bow shapes, in my opinion, avoid the formation of waves by submerging the stem, producing more friction but expending much less energy on the bow wave. I'm just stating my opinions.

 

[jehardiman]

@TANSL , I don't have a section, but here is her data and plan. She is quite light and shallow for her beam.
https://sailboatdata.com/sailboat/chatam-60/

 

[gonzo]

How many have been on a sailboat without the mast on moderate to heavy weather?

 

[James Wellington]

How many have been on a sailboat without the mast on moderate to heavy weather?

I don't know , but this one has a 3.2 meter retractable keel, and low center of gravity. And it was recommended to keep the boom, for a small emergency sail.

 

[gonzo]

Is the reason to remove the mast to be able to go under low bridges?

 

[James Wellington]

Is the reason to remove the mast to be able to go under low bridges?

That's a minor reason, for European canals, mainly though so us old guys don't have to do all that sailing work, and out in the cold.

 

[gonzo]

You don't have to put the sails up because you have a mast.

 

[James Wellington]

You don't have to put the sails up because you have a mast.

Sailing is a lot of works compared to motoring, that's why many old people switch, like Steve Dashew too. And with a mast can't use European canals.

 

[CT249]

How many have been on a sailboat without the mast on moderate to heavy weather?

Me. It's ugly.

One other thing I note is that even displacement powerboats from my memory typically have much harder bilges than the vast majority of boats, plus a false keel or bilge keels to stop rolling. D K Brown's superb books on warship history go into quite some detail about the way that warship hulls were designed to reduce rolling. So even if one could compensate for the c of g issue, sailboat hulls probably normally roll much more than powerboats.

 

[gonzo]

Yes, it's ugly. I have delivered boats to get their mast up at a different location and the roll was quick and stopped suddenly.