Effects of racing rules on boats

If I remember right, the effect of racing rules on sailing rigs was one of Phil Bolger's pet gripes.

 

Thanks Mike, that's good info.

 

There is nowhere to "get" to.

The original question in the thread was about whether current characteristics such as "straight (vertical) bows, sugar scoop sterns and open sterns" were due to artificial rating rules.

The answer is they are not. Quite the opposite, they are simply better solutions for the problems faced. The best design houses in the world seem to realize this.

A few people who post on internet forums can't seem to accept progress and continue to perpetuate the same old myths that have been circulating since the 1970s. The good news is they get no vote in the direction of the art.

 

And what then are the problems?? Is 0.3 knots a problem?? Name one real problem for a occasional cruiser they solve.. Some (like me) have a couple of advantages of sugar coops but that has nothing to do with sailing..
BR Teddy

 

You know, this forum is not a warfare simulation. You get no points for blindly holding your ground and browbeating your fellow members into submission, or outshouting them until they give up in disgust.

Fallout from rating rules has affected design fashions in cruising boats (and even work boats) since they first started being written, as any nautical history buff can tell you.

For you to single-mindedly insist that today's cruising boat designs are based purely on performance and practicality, and that racing boats and the rules that created them have mysteriously stopped having any impact at all on what's fashionable, is absurd. Give it a rest.

While we're at it, it seems you have never designed a boat or even built a boat. So who appointed you the Prophet of The Direction of The Art?

 

Production craft are designed by marketing teams, lawyers and design executives. A basic design is threaded through each department until they have a homogenization of what they think will sell the most units, maintain the company heritage or look, practical or not, so long as the head has a cup holder/tissue dispenser.

They are subject to styling influences from a number of sources, but racing yachts are the biggest trend setters. In the late 1950's, early 60's a well known designer (then a fairly young man) literally took a chain saw, to the stern of his freshly built racer, because he felt it was heavy and this was a safe place to hack some weight off. He won or placed high in the following day's races, while everyone noticed his butchering. Within a year or two, nearly every major production design had a reversed transom. I've spoken to the chain saw wielding man himself, who's not sure if he was first, but he was one of them.

Nat Herreshoff's cut back forefoot took the industry by storm and was the standard for several decades. His rigging advances swept through the pleasure boat industry like fire on wood chips. Once rudders came off the keel, nearly every production boat soon followed. The wings and winglets that appeared in the mid 1980's, where a direct result of Australia II's contrivance and remained on production yachts until tooling was paid for, years after it was long out of fashion in racing circles. Water ballast, blister deck structures, fat butted boats, twin rudders, square top sails, you name it, all came as a direct "trickle down" affect from racing. To deny this is purely to ignore history or in Paul's case a typical stance.

 

+1...

 

Except to try and discuss naval architecture rather than accept opinions?

They are solutions that suit the statement of requirements. With a bit of fashion and current fad mixed in.

Racing boats are designed to a completely different SOR and their design can and does influence cruising boat designers. As I posted before just consider the Froude number a racing boat can operate at. If you actually zoom into the RAO curves and look closely you can find that a pronounced V shaped bow can have a lower resistance at the Fn a cruising boat operates at.

If you compare vessels with the same displacement and sectional area curves then for a cruising boat there are advantages in a raked stem. That doesn't mean a plumb stem is a poor design either.

And a good illustration of rating rules affecting design opinion was your statement

I do think this is something of a current fad. There have even been articles I've read suggesting that a raked stem is somehow unseaworthy ! Which is clearly an opinion based on ignorance and influenced by current trend.

Presuming you are referring to seaworthiness and seakeeping with that comment.
Al I can say is that fortunately Naval architecture isn't based on opinions it's a fact based discipline.
I would note that every time in the past I and others have offered to send you papers and work by institutes that disagree with your opinions you have not been in the least bit interested. I've offered to you several times now that you can open a thread on that and have a proper discussion rather than the snide sniping you like to indulge in.

 

As to comparison of racked vs. plumb stem on otherwise perfectly identical boats(same LOA, same deck in plan view, same sheer in side view, rig, keel, rudder, weight and even same hullform of aft 50% to 65% ).
Explanations first:
1. (Upwind) raked stem design will have bigger entry angle, ,leading to: -> higher bow wave->less clearance between bow wave top and deck-> smaller sea wave required to climb the deck -> more spay and water on deck. (there is a fact, not often considered: when crest of sea wave try to climb to your deck, it climb NOT from the static or dynamic waterline up, it climb from the TOP OF YOUR OWN BOW WAVE up; hence the smaller your own bow wave, the bigger crest is required to reach the deck)
2. (Upwind) raked stem design (assuming same speed) will start to "feel" the sea wave later -> the stem will dig in deeper -> the extra buoyancy immersed will be bigger -> the bow will jump up with greater acceleration and higher -> the bow will fall down in to the trough from greater height -> it will meet the trough or advancing face of next wave with higher downward speed and dig in deeper ->... you got the idea; now guess, which design will have softer motion and be more kind to its crew?
3. (Downwind at about hull speed) raked stem will have bigger bow wave because of fatter waterlines -> effective "immersion" of stem, counting also own bow wave, will be GREATER as for plumb stem with sharper waterlines, making it MORE DIFFICULT to steer in straight line in flat water; in waves, bigger own bow wave will exaggerate any effect from sea waves, like already discussed in points 1 and 2.
List is not exhaustive, I do not repeat points already mentioned, like "same weight on longer waterline" or "smaller Froude Number for same speed" and the like.

Now some practical experience:

Take an old (about '70) R5.5 racing boat. Deck it over to create tiny cabin and even smaller self draining cockpit, while leaving everything else the same. What you will get than? You will get 9.5m * 1.9m hull of ~2.5 tons at ~6m waterline. Keel hung rudder remained without any modifications.
This exactly what was done to one old racer in my home town Klaipeda many years ago. She was not an inordinately successful in handicap racing, but still nice boat to sail for pleasure and to take part in races. I happened to sail her for few occasions. For absolute speed in races she was comparable (but almost always slower) to '80 designs of similar LWL. As regarding wetness and smooth ride, -far from perfect: wet (and I mean Wet) face of helmsman from every wave upwind, and really firm hand on the tiller at all points of sail.
Than, (~2000) new owner "took a chainsaw": he removed all the forepart almost to the mast, and built a new one, about 0.5m longer (by sharpening the very forward end of original deck plan view -he wanted to reuse the same foredeck, only the very front part of was made new), with perfectly plumb stem, same free-board (the boat had almost straight sheerline) with forefoot just clear of water. Rig and sails remained the same (physically same: 20-30 years old R5.5 and cruising sails). I happened to sail her on several occasions. It was a COMPLETELY DIFFERENT BOAT! Most of the spray went off the boat forward of the mast, almost never reaching the cockpit area, let alone the face of helmsman. Steering her was a two-fingers-on-tiller work. I do not even mention much IMPROVED course keeping at all points of sail. For absolute speed in races she started to compete with '80 yachts of 7.0m LWL or so.

Conclusion:
extending waterline with plumb instead of raked stem improve:
1. deck dryness,
2. pitching upwind
3. speed at all points of sail
4. course keeping at all points of sail, especially downwind
5. general behavior of boat

Let me trow this little stone in discussion about virtues of plumb-versus-raked-stem with all the rest (same LOA, same deck in plan view, same sheer in side view, rig, keel, rudder, weight and even same hullform of aft 50% to 65% ) fixed.

 

Perm
You start by defining a rule and then you are comparing designs within the rule.

If you considered two vessels which are effectively the same vessel , displacment scantlings etc with the same curve of immersed areas and looked at two extremes; one with a U section and a plumb bow, and one with a V section and a raked stem, then try the exercise and you'll get quite different results.

If you impose restraints then the restraints drive the SOR. That doesn't mean you can generalize about design features. If vessels are designed on Lloyds length (scantling length) then the bow shape is chosen for the SOR then you'll often end up with a raked stem and with a finer half angle than a plumb stem version.

Also consider the dynamic waterline. Long overhangs Like Paul Kotzebue's designs have short waterlines and lower WSA at lower Fn and a long waterline as the Fn increases. In sheltered water and gentle winds that vessel shape has advantages too.

 

"You start by defining a rule and then you are comparing designs within the rule."

Of course. It is the only way I know to get some meaningful and quantifiable results.

"If you considered two vessels which are effectively the same vessel , displacment scantlings etc with the same curve of immersed areas and looked at two extremes; one with a U section and a plumb bow, and one with a V section and a raked stem, then try the exercise and you'll get quite different results."

In my example curves of immersed areas were different: to same aft part different fore parts were attached. So for plumb stem vessel max area section would be further aft (in % of LWL), prismatic different and so on. It is not ideal way to modify the boat design, but it is perfectly suitable to modify existing boat. With results I have described in story about poor R5.5 (she has been modified in pursuit for pure performance, with whatever handicap turned out in the end). It has been done many times for different vessels, form maxi racers, both IOR and modern, to cruisers; one example was already mentioned here in post #11. To name just another one: http://www.sponbergyachtdesign.com/Wobegonbow.htm. I am yet to hear about negative results from this kind of modification.

"If you impose restraints then the restraints drive the SOR. That doesn't mean you can generalize about design features. If vessels are designed on Lloyds length (scantling length) then the bow shape is chosen for the SOR then you'll often end up with a raked stem and with a finer half angle than a plumb stem version."

What you mean under SOR?

With Lloyds length as scantling criteria, lengthening the WL with plumb stem will mean heavier structure, but also longer WL to support it, so in first approximation they are about to balance.

With same length on deck, It is hard for me to imagine sharper waterlines for raked stem boat versus plumb stem boat; unless they so completely different to hardly comparable.

"Also consider the dynamic waterline. Long overhangs Like Paul Kotzebue's designs have short waterlines and lower WSA at lower Fn and a long waterline as the Fn increases. In sheltered water and gentle winds that vessel shape has advantages too."

I do not want to insult anyone, but "dynamic waterline length" is like some kind of myth for me; as far as I can see as designer and sailor, it only give some benefits in very specific environment -fixed LWL and free LOA. However, those few feet of "dynamic waterline" come at high price in money, extra weight, dramatically increased pitching (stretched-out weight is supported by wery short LWL, while pitching forces from any wave can by applied far from end WL to resist them). As sailor, I simply fail to see significant speed advantages from extra length in overhangs: boat speed in races correlate pretty well to static LWL of any boat, incapable to routinely plane or surf, regardless to "free" length provided by the overhangs. "Cruiserised" International dragons with LOA of 9.0m static LWL of 5.8m with ~2.3t weight, sail pretty much the same, if not slower as boat of '60 design with 6.5mLOA, 5.8mLWL, 1.8t weight. Just facts I do see around me. 20 years ago I was great believer in long overhangs and their positive effects on everything. Before I tried more modern boats, to discover all the benefits of shorter overhangs and longer LWL I present here to the forum.
The only real advantage I see from my sailing practice is great performance in drifting conditions, when only relevant factor is sail area to wetted area ratio.

Regards

__________________

 

Perm
If LOA and maximum performance are the main design criteria then you are absolutely correct, I’m not saying otherwise.

But beware of the argument that says for a fixed deck length the best performance result comes from a plumb stem, so therefore a plumb stem is the best option in all situations regardless of deck length. That argument doesn’t allow for the benefits that some other bow shapes offer.

I was probably confusing but I meant two vessels of the same Lloyds length \scantling length D etc with deck length variable as the rule. I was just illustrating that your SOR actually drives the vessel design. SOR (Statement of requirements).

As for pitching just be careful it is affected by a combination of longitudinal gyradius. wave energy spectra and self damping . The shape of the forward sections and bow is chosen to match the required RAO. ( wave response, seakeeping )

Consider that a U section with a plumb bow pitches with greater amplitude than a V section. But you get higher deceleration with the V section, (unless you have a higher longitudinal Gyradius…..... and so we go around in the dance of optimal design. )

I’d suggest that static waterline is the myth (even if it’s a good general measure), waves even self generated in smooth water are the reality for WSA and LWL and stability. Just look at your tank test pics at say Froude numbrs .2 and .5

 

"Consider that a U section with a plumb bow pitches with greater amplitude than a V section." "But you get higher deceleration with the V section, "

This depend on heel angle at which we make our investigations; flattish V at 20...30 degrees of heel is much worse (slamming, if nothing else) as U with almost vertical sides in the same condition...
For sailing upwind, and have soft ride, V has to be really deep, much deeper as is common or possible on light displacement boats; not less than ~50 degrees from horizontal. It is really possible and even desirable for heavy designs with weight to length ratio comparable to XIX century pilot cutters. Nothing wrong about type of boat; it appears that some features are good on heavy boats and bad in light, and otherwise.

(looks like I am drifting to necessity for very clear set of design restrictions to make considerations really useful and applicable)

"(unless you have a higher longitudinal Gyradius…..... and so we go around in the dance of optimal design. )"

With long overhangs, gyradius as compared to LWL, is always greater as the same ratio with short overhangs. Whatever the other restrictions.

...I would guess, that fore overhang of, say 3% LWL (with high freeboard common on today's designs) is almost equal to plumb stem...

Optimality of design starts with optimization criteria, set by design brief, directly or indirectly. As an extreme example I remember tall ship "J.R. Tolkien" (http://www.sailingnetworks.com/gallery/view/585393) with overhangs so pronounced it looks almost like cartoon (or dream ). My guess would be this feature was set forth from the very beginning of design process.

"I’d suggest that static waterline is the myth (even if it’s a good general measure), waves even self generated in smooth water are the reality for WSA and LWL and stability. Just look at your tank test pics at say Froude numbrs .2 and .5"

Myth or not, but average speed of sailboats which are not able to plane routinely, correlate within ~5% with static LWL: average speed on course (including drifting with 0 wind and counting only straight distance from A to B when beating, no motoring) v[knots]= 1.5(LWL[m])^0.5; as well as hull speed is vmax[knots]=2.43(LWL)^0.5, with overhangs or not. This data is collected from actual sailing experience with real boats, not calculations or tank tests or whatever. I agree, that long overhangs could contribute by making driving force necessary to sail at hull speed somewhat smaller, but speed as such cannot be increased more as by few %. Only exclusion I know about is really poor design that drag transom; but this boat was specifically designed to use short-lived IOR measuring advantage of "transom stern" (back on topic ). With 1m of stern extension added, average speed increased by ~0.5...0.75 knots.

 

Thanks for your PM

Yes there are some important distinctions you consider the design of all aspects of the hullform based on many factors.

We could go on to talk about forward section shapes in all sorts of detail and further derail this thread It is worth it's own thread later .


Here's another issue:
Appendages (keel and rudder) racing induced fashions that can be detrimental for cruising boats.
For example a short section strut and bulb has a higher drag than a foil with internal ballast, stalls easily at low reynolds numbers and has a poor lift drag coefficient but for the racer it's worth it for a reduced WSA and an increased righting moment.
Bulbs are also prone to getting hung up with higher levels of damage in groundings (as are wing keels) when the boat is pulled off. Their attachment can be troublesome but they look very modern.

 

Here we could derail the topic again .
Because design, build and use philosophy of racing and cruising boats are different.
For racers it is "whatever helps to win the race at whatever price an owner could be forced to pay"
For cruiser it is more like "whatever comfort, fashion, and performance fit inside set budget", or myriad other variations.
Racing rules influence cruising design rather indirectly -trough results in research and development in speed department which would never be done for cruisers, and trough fashion -some people like their cruiser to look like current racing boats.
But all this is rather beside the point.
I would guess this tread is more geared towards racing boats, as they are directly influenced by racing rules.

So I would propose to keep discussions on racing boats field.

When comparing foil with internal ballast versus strut and bulb configuration, there is a trade-off between extra stability from bulb and lower drag from integral foil.

As to extremely long-narrow-thin keels with (T) bulbs -currently it looks like owners are prepared to pay for all the super strong steels for struts, all the high end and high cost technologies necessary to make them and to attach to hulls; and all the risks of failure; crews are yet to be fed up with high precision, required in handling a boat with keel and rudder, which stall at ~10 degrees; with all the problems of debris caught by T-bulb configuration. I am not inside high-end racing circuit and do not know if there are some underwater trends.

I would guess, not only rules are responsible for current skinny appendages.

As far as I know, not all VPP-s consider balance of boat and drag of rudder deflection to keep boat balanced. Hence it looks like the bigger rudder area simply mean more drag, when studying the numbers...

And certainly no VPP consider maneuvering modes, where stall and high angle of attack performance of rudder and keel became of vital importance.

Also I did not yet hear about fully functional VPP, which could consider sailing in the waves in dynamic mode, with boat pitching, rolling, rudder constantly moving, angle of attack on keel constantly changing in time (and differently over different parts of it). Current VPP-s, as far as I know, consider waves by coefficients, by adding some drag, by modifying drag (or speed?) due to certain gyradius and so on. So negative side of otherwise very efficient thin and high aspect foils -extremely narrow range of usable angles of attack and early stall -is not readily apparent in numerical form. They have to be accounted for in "common sense mode".

However, sometimes (once in a few years in Yachting World for example) there appears a featured boat with a comment like "with bigger rudder you use it less, and so create less drag". So maybe, top designers are quietly at work on this.

Also the fact, that the more benign intended operating conditions are, the less rudder area is necessary; and for so long conditions (wind strength, waves) remain below intended limits, extra rudder area indeed can create extra drag and slow down the boat.

Hmm....

It looks like my considerations lead to conclusion that too skinny keels and rudders are caused not so much by rules by itself. In handicap classes keel and rudder design is restricted very little (unlike RORC or IOR times, where draught and CG of keel were effectively strictly limited), and are driven the way they are now by current state of the art of design tools and design philosophy behind the process.

So rules are only responsible by setting (almost) no limits. In long run it might be even better for all of us (until we get to 6m boats with 4m draught, that is ). When area of diminishing returns will be reached, either common sense of owners and designers, or the rules will set some sensible limits.