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  #11  
Old 11-11-2004
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more on old IOR boats

We sailed a San Juan 28 for years, a cut-down version of 1970''s Bruce Kirby designed IOR half-tonner, the SJ30. I remember Dennis Clark telling me how they modified the SJ30 mold with a 55 gallon drum of polyester filler to make the 28. It was a classic IOR boat, dinky main, big foretriangle, pinched ends, squirrely as hell with the chute up in a breeze but fast up and down in light air. Per the brochure it had a 50% ballast ratio and despite the very rounded sections stiffened up and was powerful upwind in a big wind and sea. I remember getting caught in the Gulf of Alaska 20 years ago in a 40 knot northerly while traveling in company with a J-30. We had no problem going upwind into this to beat into a sheltered bay, after trying for a while he gave up and cracked off. When we met up the next day he had seaweed hanging from his lifelines, we never took more than spray.

The interesting thing about this boat was how well it sailed under just main. Clearly the power was in the foretriangle but you could sail it around like a dinghy with just the main up. It held up OK in some tough use although we blew the rig off it in Typhoon Holly, but that was asking a lot of a boat that is really a coastal cruiser.

Bottom line is I think at least some IOR boats are under-rated; they can sail very well, especially in lighter air where the pinched ends reduce wetted surface and the big foretriangles provide power. Given that, we now sail a boat based on the typical IMS type-form (before the latest slab-sided weirdo''s) and love it. We had the chute up in 20-25 this summer in good sized seas 100 miles off-shore and it was effortless. In the IOR boats I''ve sailed it would have been a white knuckle deal. Time does move on.
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  #12  
Old 11-22-2004
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cpa,

I do have a few questions for you. If you would, please contact me off-list@ owen.mccall@abbott.com. Thanks.

Owen McCall
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  #13  
Old 11-23-2004
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Is the discussion solely related to IOR boats designed solely for racing? If not...

I think that for most sailors who would like a performance boat, IOR boats are a fact of life. The IOR existed from roughly 1970 to 1990, correct? Thus, If you are looking for a boat of any significant size at a reasonable price....welll..... I think you are getting an IOR boat.

But that is not a bad thing. I too think many IOR boats are under rated. The sheer number alone that have circumnavigated indicate that there are robust and seaworthy designs that a good sailor can be happy with.

Yes, by today''s standards IOR designs are somewhat of an artifact based on a rule. But then, was the rule such that it was impossible to create a good sea boat? I don''t share that view (though you might make that case for the CCA rule).

In my opinion, there are a plethora of "IOR" boats that are not at all alike. Like any design field, there seems to be a range of designs that went from one extreme (perhaps light, pinched and wet) to the other (heavier, less extreme, moderate and seakindly). Pure racers to boats more suitable for cruising. Thus, I am not sure we can dismiss all boats of that era under the rubric of the IOR rule. There are certainly IOR boats that sail well, have a sea kindly motion and are not at all wet.

I also think there are some advantages to IOR boats. The overhangs for one. Less extreme than those of CCA boats but offering greater reserve bouyancy forward than many of the plumb bow designs popular today. This attribute is important to cruisers who might carry more ground tackle forward and also do not wish to spend long tacks ''submarining'' the boat. IOR sailplans that have modest mains and large genoa jibs are not as easy to handle as more recent plans with fractional jibs and large mains, but, this type of rig is simple and robust, roller furling and large winches can mitigate jib management to a significant degree.

IOR boats can be fun to sail and a thing of pride to own. And they are affordable. There is plenty of upside for us :O)

Best to all

John
s/v Invictus
Hood 38

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  #14  
Old 11-23-2004
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more on old IOR boats

John

I look at this differently, while there were a lot of IOR boats built during the period 1970 through the late 1980''s, most boats built during that period, that are suitable for cruising, especially aimed at coastal cruising or specifically aimed at offshore cruising, were built with little or no regard for the IOR rule except perhaps for the fad of tiny mainsails and huge genoas which really was a carry over from earier race rules as well.

I think that most IOR boats are overrated rather than under rated as cruising boats. They are tender, wet and a bear to sail without an army of gorillas. While I am sure that there are a number of IOR boats that have sailed around the world, I doubt that they represent a very large portion of the cruising population and in most cases they certainly do not represent a reasonable decision for a distance cruiser without an enormous amounts of heavy modification and a certain willing to take risks and live uncomfortably while doing so.

By the very nature of the rule anything built after IOR-1 was anything but "heavier, less extreme, moderate and seakindly". The rule explicitly discouraged that so a boat built that way was by definition not an IOR boat.

I also disagree with your statement, "The overhangs.....[were] Less extreme than those of CCA boats but offering greater reserve bouyancy forward than many of the plumb bow designs popular today." Actually one of the advantages of the plumb bows of today is that they actually have more reserve buoyancy forward than bows with overhangs and they use that reserve buoyancy sooner and more gently than a boat without a more plumb bow. That is the reason that traditional working watercraft in areas with rough conditions typically have plumb or near plumb bows. Plumb bows are less likely rather than more likely to submarine as they start to lift the bow sooner.

Respectfully,
Jeff

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Old 11-23-2004
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Hi Jeff,

It is great to chat with you again. I take your point that boats that were designed to be heavier and more sea kindly departed from the IOR rule. Perhaps they are better termed IOR era boats?

The issue of reserve bouyancy is one of great interest. I am not an NA nor expert in any way but as I view watercraft, both power and sail and watch how they move through the water (in real life and in pics), I see more plumb bow boats going bow down than I do boats with overhangs. When I look at the design of major ships like deep ocean work boats and ships such as Aegis class cruisers, the design trend is the "plow sheild" bow....which is essentially an overhang. I may be quite mistaken but I think this type of bow, either on a sailboat or powerboat or ship serves two functions: that of creating a drier ride through the waves and reserve bouayancy. I understand your point about a plumb bow boat using its reserve bouyancy sooner...and as I look at some of the new Bene''s and Dehler''s I might see how a higher bow might do that. But...intuitively...if you have a broad bow with its overhang, you have a hull area of light displacement. Thus under Bernoulli’s principle it is bouyant and it is bouyancy not being used by the boat at its static waterline...thus it is reserve bouyancy. No? Remember, I am no expert so this is what I come up with thinking in the simplest terms.

All the best

John
s/v Invictus
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  #16  
Old 11-23-2004
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more on old IOR boats

John, Jeff and the Group:

I''m coming to the party a bit late on this thread, but find it a pretty interesting discussion after John''s initial observations.

First, I''d agree with Jeff that many boats out cruising and that were built during the ''IOR era'' are not direct descendents of the IOR rule; or at least, that''s not what I''ve been seeing. I''d also agree that there has been some ''bleed over'' between IOR design trends and more generic cruising boat designs, one good example being the large foretriangles that exist on many 80''s and 90''s cruising boats. Personally, I think that''s helpful because most often a cruising boat (or at least, one used for long distance cruising) will end up - sooner or later - with an inner stay, and the utility of that stay is aided by the larger foretriangle. (I''m sure I''m destroying lots of nuance and design sublety with that statement but, in general, I think it''s a valid one).

Second, I think you''re basically on target with your comments about bow designs and reserve buoyance, John. I''m troubled by Jeff''s comment that, in general, a plumb bow is going to produce more reserve buoyancy than one with an overhang because a) the plumb bow is most likely present in the design to extend the static waterline length and improve hull speed, not because of its reserve buoyancy benefits, and b) because reserve buoyancy is going to depend on the lines of the boat''s forward sections, not just on a single line we see in profile of the hull shape but on the three-dimensional form of the bow section. Intuitively (tho'' perhaps also in ignorance on my part), logic suggests that with identical hull forms and with one hull offering more overhang than the other, greater reserve buoyancy will exist in the lines with greater overhang. To the extent that designers include a fuller bow section with a more plumb bow (as seen in profile) in order to provide equal or greater reserve buoyancy, there''s going to be more weight and also cost introduced by those fuller lines, so it''s not a free lunch. I mention this because there''s almost the implication in Jeff''s comments that the greater reserve buoyancy of a plumb bow comes from the plumb bow itself (as seen in profile), which I don''t believe to be close to true.

So Jeff...and few more words to knit together John''s and my views with your own, if you please. And BTW, Happy Thanksgiving to you both if I don''t have a chance to see this thread until late in the week.

Jack
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  #17  
Old 11-23-2004
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What I think is confusing to me is that we are not specifying "a fuller bow GIVEN (1) A FIXED DECK LENGTH OR (2) A FIXED WATERLINE LENGTH." If we are talking about a fixed waterline length, then a overhanging bow will have more reserve bouyancy than a plumb bow. If we mean per a fixed deck length, then a plumb bow will have more reserve bouyancy and a submerged "ramming prow" (reverse overhang, like on a Roman trireme) will have the MOST reserve bouyancy.
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Old 11-23-2004
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Neither am I trained in the esoteric art of maritime design, but I have my own intuitive notion about this subject. The phrase “reserve buoyancy” must be understood in a broader sense than it is normally thought of. It is not simply load carrying capacity.

Think of the differences in the entire hull form, not the bow alone. From above, the waterline shape of earlier IOR influenced boats appears much like a diamond, especially in comparison to more recent plumb bow hull types which tend more toward a triangle shape. IOR boats with larger bow overhangs typically have broader beams which occur further forward then taper more to the stern, relative to plumb bow boats which typically have somewhat narrower beams farther aft forming a fuller stern section.

Simply imagine a block of wood cut to these waterline shapes. With the IOR diamond shape, the center of flotation is near mid-ship and the boat tends to rock (pitch) from this central axis. Lifting the bow tends to depress the stern and visa versa. With the triangle archetype, the bow waterline is sharper and narrower and center of flotation is moved aft. Lifting the bow depresses the stern much less and pitching motion is dampened.

While it is true that sailboats with plumb bows are likely to be more sensitive to excess weight forward, it seems reasonable to assume that with properly distributed ballast and gear stowed aft they will rise more easily and with gentler motion to oncoming seas given the longer lever arm between bow and beam and reduced pitching energy to be overcome. This is functionally the same thing as reserve buoyancy.

Many other well understood benefits also accrue, such as waterline length as mentioned plus downwind stability resulting from a more stable three point stance, so long as proper ballast trim is maintained. If ultimate storage capacity is the goal then fuller bow sections will be beneficial, but at a cost. As in all boat design decisions, some compromises are made, moderation is best and more is not necessarily better.

This simplistic perspective does not address the extensive overhangs of older, slimmer designs which grew out of far different circumstances. I’ll leave historical context, technical corrections and terminology to the better qualified among us. Am I misunderstanding completely, Jeff?
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Old 11-23-2004
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Well, I''m no navel "artichoke" but some of my observations may be revalant.

Back in the 70''s when I was doing a lot of sailing on IOR boats, 1 Tonners, 2 Tonners, "Grand Prix" boats, I spent a couple of weeks campaigning on a "Thistle" one design sloop. I was particularly impressed one weekend in Buzzards Bay, 25+ kts, lots of steep chop, and the Thistle just flew... If you know the Thistle, it has a plumb bow and a very full forward section and carried it''s beam well aft. Almost a cylinder with one end shaped to go through waves. Not to mention the fractional rig, large main, small jib and ''chute. After that weekend, I always wondered why you could not design a "big" boat the same way. When I saw my first Riechle-Pugh (sp) maxi, I said to myself, "Hmmmm looks like somebody finally saw the light!"

One of the things about the IOR designs was yes, they have overhang, but they carry a narrow entry well aft before they baloon out to their maximum beam. Yes, by definition, a boat with overhang would have more reserve boyancy, but that would assume a similar beam profile. Modern designs carry their beam farther forward and farther aft, so as the bow goes down, a much greater area is being pressed into the water, and as a result, there is more boyancy.

Now, I will have to agree, that by dismissing all IOR designs as "bad", you may be throwing the baby out with the bathwater. My trusty old IOR designed Heritage 1 Ton has many of the bad design traits of the IOR era, but the whole is way more than the parts. I show my transom to most boats in my size range, regardless of when they were built. But I have to "shift gears" much more often than newer boats, and that is when they can get me. Unless I have a full crew, who really know what they are doing, I am forced on a race course to make compromises that will ultimately affect my boat speed.

As far as cruising goes, I don''t carry the comforts of home with me, think "camping with sails", but I am WAY faster than any modern non-racing design. I can remember a brisk fall day, 20 - 25+ kts. I was having a blast with full main, no genny. Steaming along at 7kts, enjoying the sun and weather, and the occasional wave rolling aft, while most of the cruisers were huddled behind their dodgers, full fowlies, and struggling. But that is just the way I sail. For some, that day was work, for me it was playtime. I think that if you are into the look of the IOR boats, and I certainly am, they can be a good value. I would steer clear of the post "Celebration" (Bill Cook designed 1 Ton from 1978) era IOR boats, with their funky rule cheating flat section down the center of the hull. They will rattle your teeth in a chop. But I like the look of the early designs and best of all Silmaril is PAID FOR!!!!!
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Old 11-23-2004
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Nice discussions and always great to hear from Jack (not just because he agreed with me :O)

I think for the purposes of discussion we will have to stipulate that either beam carried forward and angle of V in the hull have perhaps more to do with how dry a boat is and/or that comparisons need to be made on a standard LWL or LOD.

But lets take the case of two similar boats meeting the same wave:

When a boat with a plumb bow say 5 ft above the static waterline meets a 6 ft wave, at the moment of impact there is little opportunity for the hull to be bouyed at this point to overcome the motion of the wave and the wave washes over the bow.

When a similar boat with some overhang approaches the same wave....the angle of the face of the wave carries to the angle of the bow and thus a portion of the boat not already directly involved with bouyancy is used to provide more (read addional or reserve) displacement (read bouyancy) before the portion of the boat above the static waterline is carried to the wave. Thus the boat is carried over the wave rather than through it.


I also have a question. If it true that a plumb bow boat has a longer lever arm ...then that arm (LWL) creates more torque and (as mentioned above) it takes less pitching energy to overcome and thus it has a greater ability to float forward (bouyancy). BUT....this runs counter to statements made here that boats with longer waterlines (same LOA) pitch LESS. SO...we have a theory that runs counter to an observation.

So...the related observation that has been made about boats with longer overhangs is that they pitch more. If that observation is true, then either these boats must have a reduced pitching energy to overcome...or lever arm has little to do with pitch. I submit that what accounts for the discrepancy in these observations is that boats (with overhangs) in fact have appendages that contribute downward force when above the water (due to gravity) and upward force with meeting water...reserve bouyancy!

My best to all

John
s/v Invictus
Hood 38 (searching for its identity as an ''IOR era" boat :O)
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