Effects of racing rules on boats

Yes, crazy me, living in bizarro world and defining boats by LOA. No one in their right mind would do that.

It's not my fault. I have been brainwashed by all the boatbuilders who name boats things like "Catalina 36". These goofballs use the designation to define the LOA! What fools!

I know too many people who shop for boats, looking to buy "something in the 30 foot range" instead of "something with a WL around 25 feet". I guess they need to be edumacated.

Ditto the lunatics at the marinas and dry storage yards who dare to define my boat by LOA instead of LWL. It is all a conspiracy!

I will have to break this habit I guess. Maybe I'll get right on that in the new year.

There's that claim of "Flare" again. I wonder if you can point us to any raked stem cruising designs from the past 20 or so years that have flare in the bow sections?

Since someone else mentioned Boob Perry earlier in the thread I just checked his book Yacht Design According to Perry. He was good enough to include linesplans for about 20 of his designs, everything from His Valiant 40 to his latest creations.

I only saw what might be flare in two designs (Valiant 40 and Freeport 36). Both look like they might have flare in the -1/2 station. It is hard to tell for sure since the reproductions are so small and indistinct. In both cases they have no discernable flare at Station 0 and by Station 1 they have flam.

Now if Perry isn't doing flare in the bow sections I wonder who is?

One that has been going on for the 30+ years I have been interested in Yacht Design.

 

Funny you mention this. I was going to bring that up in my reply to you but didn't want to introduce yet another variable into this discussion.

If I was doing something for myself I would definitely include this characteristic. You might be surprised to hear I would probably rake the bow a bit, maybe 1.5 to 2 inches per foot of freeboard, just because a dead plumb bow doesn't fit my eye for some reason.

I wouldn't be adding the minimal rake for performance, that's for sure.

 

"Flam" is the correct term for what many think of as "flare".

A clarification of terms for those following this thread:

Flare is concave curvature in the topsides. Flam is convex curvature in the topsides. A few sailboats have flare. Lots of sailboats have flam.

 

I'm not surprised at all. The look of a plumb bow is an acquired taste. I went with a flying bow for a 15 square meter I designed for myself. Definitely rating rule influenced, but I like the way it looks.

 

I'm not sure what your definition of flare is, but it doesn't have to include curves. A straight outward slant from the bilge or chine is also flare:

Flare is the outward, upward curve or slant of a vessel’s sides, from the waterline to the deck line.

to open or spread outwards; to project beyond the perpendicular; as, the sides of a bowl flare; the bows of a ship flare.

to project outwards; contrary to tumbling home.

'A bow with more flare gives a drier ride' is such an obvious statement that I see no point in bothering to explain it; methinks I'd just be walking into a minefield of quibbling and semantics if I tried. It should also be obvious that other things being equal, a bow with a plumb stem will have less flare than one with any sort of rake.

Let's compare apples with apples and oranges with oranges as much as possible, shall we? Obviously a plumb bow with a deep forefoot would have more 'tendency toward this issue' than a raked stem with a deep forefoot, and a plumb bow with a shallow forefoot would have more 'tendency toward this issue' than a raked stem with a shallow forefoot.

Obviously, it isn't an insurmountable issue. But it is one that should be kept in mind during the design process. As I've mentioned before, traditional shallow-draft, flat-bottomed sharpies dealt with the problem simply by being designed and trimmed to keep the forefoot of the stem above the waterline.

edit: I removed my reference to flam; the definition I was using doesn't seem to be the accepted one.

 

I like to use the one that is understood by people who design boats. Here it is, borrowed from Perry's book. I have it in other, earlier tomes, probably one or another that Perry borrowed it from, but the Perry book is here at hand.

Edit: Paul Kotzebue beat me to it in Post #78.

 

Flare is not necessarily curvature; it simply means the boat widens as you go up from the waterline. You can have straight sides that flare. My new flat-bottomed canoe has a fair amount of flare...which disappears at it approaches the plumb bow, and would still be there had I raked the bow instead.


edit: I deleted my definition of flam; it seems I was full of it. Although Ted Brewer, on page 29 of Understanding Boat Design, says that at least one marine dictionary defines it the way I did...so at least I have company.

 

A lot of naval architecture terms get subject to local norms. In this case I meant as troy posts here that the forebody sections widen towards the deck.
Whether it's a V which is common or an accentuated flare I consider them both to be flare. The other section being a U shape. And there are shapes and variations in between .

 

Can you post any examples of modern sailing yachts where the bow sections don't get wider towards the deck?

 

Summary: your opinion is that boats should be designed on LOA alone. That wasn't actually what we were talking about. We were looking at the fact that adding 3 feet on the bow doesn't just give you bragging rights. It can give you some advantages.

So if you were going to add a bowsprit for anchor handling can you see that there could be some benefits in some vessels in actually extending the deck out instead?

 

Now you are talking about the amount of flare, even a U section can have flare. If you start parsing the nuances on every minute detail we will get nowhere.

Is this all because you don't want to admit that there can be some advantages to raked stems?

 

Regarding "wet" boats, many newer boats are wet because they are fast. If you slow them down to the same speed as older boats, they may not be so wet.

 

On plumb bows, the deck disappears a lot faster as you approach the stem.

That doesn't make them horrible. But it's a fact that needs to be dealt with, particularly if you're planning to hang out forward trying to do something useful.

Backtracking a bit:

People's ideas of aesthetics differ and are subject to change, I guess. I used to feel the same way. But over the years I've gotten fond of the way plumb bows look, particularly on traditional-style boats.

 

Raggi
Model tests on plumb bowed U section open 60 and well flared foreward sections showed the U sections to be much wetter with 15 to 20% larger motions at the bow relative to the well flared model for the longer steeper waves. For seakeeping that's very significant.

However racing boats like the Open series operate at Fn's well in excess of cruising boats and often the RAO is pitched for them at a Fn well above .4 which would be considered a very decent speed for a cruising boat.

For slower speed boats more attention of the characteristics below Fn of .4 is worthwhile and there are gains to be made that just wouldn't be considered in a racer which has quite a different design paradigm.

That's where racing boat styles may influence cruising designs unfavorably, features which do benefit a high Fn may actually penalize a cruising boat.

There's an overview on bow shape in "ship design for economy and efficiency" the points made are pretty close to what's been said here re reserve buoyancy, seekeeping, dryness, collision.

 

without reading the whole tread if its not already named
Marchaj's "seaworthynes, the forgotten factor"
is a good book on "Effects of racing rules on boats"