LOA vs. LWL: A design question

[rslifkin]

Originally Posted by MartinR

Yes, but I think we are talking cruising boats here. Modern racing boats are indeed made for planing.

Plenty of the modern cruising hulls are quite capable of planing. However, that doesn't mean they're typically carrying enough sail to actually drive the typically heavier boat beyond hull speed under most conditions.

[Jim Cate]

Another factor in long LWL designs is less pitching and hobby horsing than in similar LOA designs with less LWL. We noticed a big difference when we changed boats.

Jim

[valhalla360]

Originally Posted by jtsailjt

I understand modern, wide, sterns with little to no overhang but I don't understand plumb bows at all. If you look at the boats in the photos just above, both have very long anchor rollers to effectively lengthen them enough so the anchor doesn't bang against the bow when being retrieved and I think they look quite ungainly. So, what I don't understand is, why not take the same boat and also add a little flare to the bow so it's a bit wider at deck level (more working space on deck) and also extend the length of the bow up at deck level a couple of feet. so everything could remain exactly the same from about a foot above the waterline down and sailing performance would be unaffected except in big waves you'd add a small amount of reserve buoyancy near deck level, but you'd have more room at the bow on deck and the anchor roller wouldn't have to be cantilevered so far out in front of the boat. I can't see any disadvantage to this and think it would look a lot better along with the practical aspects I mentioned. So, except for stylistic reasons, why have plumb bows become popular on boats that aren't pure racers?

Even with overhangs, most boats have an anchor roller that sticks out a ways, otherwise, the anchor will still smack into the hull, so you aren't really adding much if anything on a plumb bow boat.

Even if you want to argue it's a 6" longer bow roller, for marketing purposes, it doesn't count as being a longer boat in terms of pricing.

[Cadence]

Originally Posted by Jim Cate

Another factor in long LWL designs is less pitching and hobby horsing than in similar LOA designs with less LWL. We noticed a big difference when we changed boats.

Jim

Seems to me hobby horsing would be more a factor of wave period?

[jtsailjt]

Originally Posted by Cadence

Seems to me hobby horsing would be more a factor of wave period?

That’s a factor for a given boat but in similar conditions a boat that has a shorter LWL will hobbyhorse more and this is exaggerated in a boat with long overhangs with weight in the overhangs.

BUT, I had just such a boat (Hinckley Pilot 35) and while it definitely would hobbyhorse, it had the most amazing soft ride sailing to weather. It never pounded and instead you’d see the bow softly plunge into a wave and the bow would appear to be within an inch or so from going under but then start to rise. So this worked out great for the Pilot, but not all designers of sailboats during this era of long overhangs were as skilled as S&S.

[jtsailjt]

Originally Posted by valhalla360

Even with overhangs, most boats have an anchor roller that sticks out a ways, otherwise, the anchor will still smack into the hull, so you aren't really adding much if anything on a plumb bow boat.



Even if you want to argue it's a 6" longer bow roller, for marketing purposes, it doesn't count as being a longer boat in terms of pricing.

Yeah I realize that all anchor rollers stick out, but it’s a question of degree, and the choice to forego the advantages I cited in the post you responded to.

I don’t think it looks like even close to 6’ longer, more like just a foot or two. But the point is that it looks a bit odd to have such a long anchor roller, to my eye at least. And as far as pricing goes, just by adding a slight flare and overhang to the bow, that would turn a 45’ boat into a 47’ boat, which certainly wouldn’t hurt the price. Another advantage to doing this is it would move the tack of a downwind or broad reaching sail forward into cleaner air without adding a bowsprit. It just seems to me that it doesn’t make sense to sacrifice so many functional advantages just to achieve a certain look.

[valhalla360]

Originally Posted by jtsailjt

Yeah I realize that all anchor rollers stick out, but it’s a question of degree, and the choice to forego the advantages I cited in the post you responded to.

I don’t think it looks like even close to 6’ longer, more like just a foot or two. But the point is that it looks a bit odd to have such a long anchor roller, to my eye at least. And as far as pricing goes, just by adding a slight flare and overhang to the bow, that would turn a 45’ boat into a 47’ boat, which certainly wouldn’t hurt the price. Another advantage to doing this is it would move the tack of a downwind or broad reaching sail forward into cleaner air without adding a bowsprit. It just seems to me that it doesn’t make sense to sacrifice so many functional advantages just to achieve a certain look.

6" (inches) not 6' (feet)

The construction cost and sales price for two boats of same LOA but one has overhangs, is almost identical, so they can sell a faster boat with more payload at the same price.

Plus most marinas don't actually measure the boat but go off the manufacturers listed LOA...so you get a bit of a discount.

[rslifkin]

Originally Posted by valhalla360

Plus most marinas don't actually measure the boat but go off the manufacturers listed LOA...so you get a bit of a discount.

This is a big one. Some marinas do measure (usually if you'll be on a face dock where your length determines if what other boats can fit). But most don't. My own marina goes off listed LOA in most cases, although various slips have a minimum length you have to pay for even if your boat is a little shorter. As an example, my boat is listed by the manufacturer as 38 feet LOA, but the slip I'm in is 45-ish feet long. Minimum length for my slip is 40 feet, so I pay for 40 feet of boat.

I've also found that many manufacturers really list LOD as the LOA, so things bolted on like a longer anchor roller don't get counted. Which means a more plumb bow and a longer roller comes out as a slightly shorter boat even if its real LOA is the same. I know the published LOA for my boat excludes the pulpit overhang and the swim platform, and only includes the length of the actual hull.

[valhalla360]

Originally Posted by roland stockham

Moderate overhangs can reduce wetted area and therefore drag when sailing upright in light airs

For racers this is a big issue. If you are racing in <5kts true wind, squeezing an extra 0.1kt out of the boat is huge.

For your typical coastal cruiser (the kind that buy probably 95% of new boats), once you are ghosting along at 2-3kts, they crank up the diesel and get the speed back up into the 5-7kt range. So at best it delays starting the diesel by a few minutes. Not a bad thing but very low on the design criteria list.

[jtsailjt]

Originally Posted by valhalla360

6" (inches) not 6' (feet)



The construction cost and sales price for two boats of same LOA but one has overhangs, is almost identical, so they can sell a faster boat with more payload at the same price.



Plus most marinas don't actually measure the boat but go off the manufacturers listed LOA...so you get a bit of a discount.

I don’t agree with either point.

As LOA increases on similarly shaped boats, so does the overall volume and displacement and cost, and the increase in cost increases at more than a proportional rate. But if you take a 45’ boat and only change the shape of the bow, leaving everything below the waterline unchanged, the displacement and volume are changed very little and thus, so is the cost to build it.

I don’t know what marinas you frequent but I’ve had mixed results in this regard. I’ve had them go by the advertised length but I’ve also had them measure anchor rollers and davits and swim platforms. But I agree with you that generally speaking you are less likely to get charged at a Marina for an extra long anchor roller as opposed to actual on deck length. But when you consider the functional and aesthetic (subjective) benefits, and the overall cost of the boat compared with occasionally being charged for 2 more feet at a Marina, I’d be very willing to take a chance on having to pay the additional few dollars a night.

[valhalla360]

Originally Posted by jtsailjt

I don’t agree with either point.

As LOA increases on similarly shaped boats, so does the overall volume and displacement and cost, and the increase in cost increases at more than a proportional rate. But if you take a 45’ boat and only change the shape of the bow, leaving everything below the waterline unchanged, the displacement and volume are changed very little and thus, so is the cost to build it.

I don’t know what marinas you frequent but I’ve had mixed results in this regard. I’ve had them go by the advertised length but I’ve also had them measure anchor rollers and davits and swim platforms. But I agree with you that generally speaking you are less likely to get charged at a Marina for an extra long anchor roller as opposed to actual on deck length. But when you consider the functional and aesthetic (subjective) benefits, and the overall cost of the boat compared with occasionally being charged for 2 more feet at a Marina, I’d be very willing to take a chance on having to pay the additional few dollars a night.

But they aren't similarly shaped boats...that's the whole point. Long overhang race boats rely on a shape that increases LWL when heeled. Cruising boats don't need to be restricted by this limitation and the entire hull shape is changed.

Been around the Great Loop a time and a half plus lots of time on the Great Lakes (hundreds of marinas). I think twice they measured the boat.

[Jim Cate]

Steve Dashew once opined that one should always buy the largest LWL that you could afford when choosing a cruising boat... this after his first cruising boat being a Columbia 50, a boat with considerable overhangs.

His own subsequent designs have always featured very short (if any) overhangs, and they have been pretty successful cruisers IMO.

I think that he is a pretty smart fellow...

Jim

[jtsailjt]

Originally Posted by valhalla360

But they aren't similarly shaped boats...that's the whole point. Long overhang race boats rely on a shape that increases LWL when heeled. Cruising boats don't need to be restricted by this limitation and the entire hull shape is changed.



Been around the Great Loop a time and a half plus lots of time on the Great Lakes (hundreds of marinas). I think twice they measured the boat.

You correctly cite the reason for long overhangs during the days of the CCA, but that’s not what I’m talking about.

And to Jim regarding Dashews, of course he’s a brilliant yacht designer and designed some vertical bowed boats that sailed very well, but Chuck Paine and Bob Perry and Olin Stephen’s weren’t too shabby either and they designed lots of post-CCA boats with overhangs so I’m not sure what your point is there. Paine snd Perry both designed numerous boats that are pretty much as I’ve been describing, with no overhang at the stern but a modest overhang at the bow which I think improves their appearance and also is practical for retrieving anchors without damaging the topsides.

I completely understand the reasoning behind overhangs that supposedly increased LWL, thus hull speed when heeled and I also understand why yacht designers want to maximize LWL, even though the result isn’t usually very aesthetically pleasing when the shape of the bow is just a vertical straight line. But what I don’t understand is why, after designing a sailboat with max LWL, it wouldn’t be a good idea to leave the stern entirely alone and at the bow leave the waterline and everything beneath it as is, but slightly pull the bow forward at deck level and widen the bow slightly as it approaches deck level (not near the waterline) so they could avoid the necessity of adding a tacked-on looking anchor roller sticking way out in front of the already aesthetically compromised hull shape. This would have no noticeable effect on sailing characteristics or hull speed and wouldn’t add much cost to construction. Maybe it wouldn’t look good either to do this while leaving everything beneath the waterline alone and that’s why vertical bows are more common than the bow modification above the waterline that I’ve described. Or maybe the designer was so focused on performance that he didn’t even plan on it having an anchor stored on the bow? But I wish that it wasn’t necessary to have such ungainly looking long anchor rollers on these boats because I think it looks bad.

Valhalla, traveling around the great loop I wouldn’t expect to get measured hardly ever as long as you kept moving. It’s usually when you will be staying for longer periods of time in a slip or on a dock or indoor storing for the winter when I’ve noticed that marinas become interested in knowing your actual length vs what the design LOA is.

[Jim Cate]

But what I don’t understand is why, after designing a sailboat with max LWL, it wouldn’t be a good idea to leave the stern entirely alone and at the bow leave the waterline and everything beneath it as is, but slightly pull the bow forward at deck level and widen the bow slightly as it approaches deck level (not near the waterline) so they could avoid the necessity of adding a tacked-on looking anchor roller sticking way out in front of the already aesthetically compromised hull shape.

Well, whaddya know? You just described my boat! Not quite vertical bow, a bit of flare, very fine entry with somewhat hollow lines near to the stem, short bow roller forward of the stem. Still needed a pad on the bow to prevent damage from the anchor when weighing in a chop.

But to my eyes, she's not aesthetically compromised at all!

Jim

[Don C L]

A little bit of cushioned pitching isn't all that bad IMO. Overhang in the bow often is the entry for a hull that is deeper and v-shaped; more conducive to a more comfortable uphill slog.
But we've been all through that!