Another Bolger lapstrake, Nord Coaster, 16 foot Cat Yawl

[brucehallman]

Here is another of the 'curvy' Bolger designs, Nord Coaster, 16 feet, lapstrake balanced lug Cat Yawl. I did the strake layouts and it looks like a relatively quick build. The wide width, and the sail rig means that it would not be strenuous to sail. The seats are hinged to fold up for sleeping space for two under a tarp awing as a camp cruiser.

http://hallman.org/bolger/NordCoaster/

[Steve Paskey]

I've always liked that design ... the one built by William Clements is a real beauty. But Bill's boat is the only boat I know of that was built to this design -- Do you know if plans are available?

[Canoez]

I've always liked that design ... the one built by William Clements is a real beauty. But Bill's boat is the only boat I know of that was built to this design -- Do you know if plans are available?

It is a pretty boat. Wasn't it Bolger's take on the George Holmes Ethel?

[Clinton B Chase]

Bruce, I like those renderings. What program?

[earling2]

Did I see that boat at the Maine Boatbuilder's show several years back, or was that just a brochure? I know that Antonio Dias's "Small" was at the Clement's booth
Love Nord Coaster

[T. Traddles]

Several years ago I wrote Bolger and inquired about the Nord Koster. He had a chance to sail the boat but noted it did not sail as well as he would have liked. He was not sure why that was the case, although he did speculate that the builder's modification of the c/b to case to accommodate a rowing station may have had something to do with it. He recommended another design in consequence. Too bad, I like the looks of that boat and Bolger's write up about it, which you can still see on Clement's site, sounds very promising. I'd probably opt for Spartina if I was in the market for a short and beamy boat.

[brucehallman]

Several years ago I wrote Bolger and inquired about the Nord Koster. He had a chance to sail the boat but noted it did not sail as well as he would have liked. He was not sure why that was the case, although he did speculate that the builder's modification of the c/b to case to accommodate a rowing station may have had something to do with it. boat.

Also, judging from the photos, the cut of the mainsail seems to sag towards the aft. A better cut mainsail could probably improve performance. Still, any 16 foot boat is going to be slow. That said, sailing at any speed can still be fun, especially in pretty boat.

My isometric model was created using the sourceforge software Free!Ship version 2.6. It is very quick and handy for calculating bulkhead shapes and expanded strake shapes.

Plans for Nord Coaster are available from:

Phil Bolger and Friends,
P.O. Box 1209
Gloucester, MA 01930
Fax: (978) 282-1349

[DGentry]

Several years ago I wrote Bolger and inquired about the Nord Koster . . . He recommended another design . . .

Which one did he recommend?

Nord Koster is only a 16' boat, but weighs 850lbs(!), and it's beamy and has a centerboard slot and a salient keel and end plates on the rudder - and only 140 sq ft of sail area. I'm just speculating, but, with all that weight and drag, and so little sail area, there's little wonder that it might not be a spirited sailer (depending on the conditions). She is very pretty, though!

[brucehallman]

... there's little wonder that it might not be a spirited sailer (depending on the conditions). She is very pretty, though!

I think by design. The design spec for this boat was for "a pretty boat with a large cockpit for four adults, space for sleeping bags for two people, and capable to be sailed in an unstrenuous fashion with a minimum of scrambling". This boat design seems to meet that specification exactly, and being a spirited sailer might require more stress than would be fun for the type of person this boat is meant for.

[T. Traddles]

Bolger recommended his 18ft camper design. A birdwatcher type sharpie. Ugly, in my mind.

[DGentry]

Huh. I can't imagine Camper 640 (a lee board sharpie) being a better sailer than Nord Koster! The accommodations would be more amenable to overnighting, and the hull itself would be quicker to build, but I surely don't see any advantages other than that. The NK is certainly in an entirely different universe, looks wise.
Perhaps Mr. Bolger was emphasizing the sleep-over capacity, rather than sailing ability?

As a pointless aside, I am taken with the visual style of the original Birdwatcher, and also with Bolger's Berengaria. But Camper 640, William D Jochems and Birdwatcher 2 leave me cold. Whalewatcher is, well, maybe a whole other topic of discussion.

[T. Traddles]

DGentry, I agree with you assessment of the designs mentioned in your previous post. I have plans for Spartina and will probably build that boat within the next year or two.

[brucehallman]

Huh. I can't imagine Camper 640 (a lee board sharpie) being a better sailer than Nord Koster!

Water hydrostatics doesn't care about "ugly".

Camper 18 ft long, 5'3" wide x 6 inch draft (150 sf sail)

Spartina 15'4" long, 7' wide, 6 inch draft (143 sf sail)

Nord Coaster, 16 ft long, 6'6" wide, (141 sf sail)

I dunno, (not paying attention to ugly) I would bet that the longer narrower boat with greater sail area will sail faster than the shorter wider boats with less sail areas.

[DGentry]

Good point, and I agree - the Camper should be often be faster. But, I should qualify my earlier thought: When I think of sailing ability, I am always subconsciously thinking of windward ability, and I think Spartina and Nord Koster would be superior in that respect. Camper's hard chine sharpie hull form, and those leeboards, are not ideal for windward work. And, too, the Camper might be a little top heavy, and that, combined with the narrow hull, could make her not nearly so able to stand up to a press of sail when going to weather. Spartina, with hopefully less weight, and definitely less underwater drag, than Nord Koster, might be the best at sailing anywhere above a beam reach, despite being shortest.

This is all just theorizing on my part, never having sailed any of these boats. There's more to sailing than just windward ability, too, of course, as we have discussed elsewhere.

[brucehallman]

I am always subconsciously thinking of windward ability, and I think Spartina and Nord Koster would be superior in that respect. Camper's hard chine sharpie hull form, and those leeboards, are not ideal for windward work.

I am in the process of studying these designs now. Modeling and hopefully isometrics soon.

Camper 640 doesn't have leeboards, it has a swinging centerline daggerboard. So do Spartina and Nord Coaster.

That said, I don't understand the problem with leeboards relative to lateral plane for windward work. The big complaint here against leeboards (I understand) is that they are ugly and a pain to handle, and that they take a special effort to tend. (And maybe the noise?) As far as the wind and water is concerned, I am thinking that lateral plane is lateral plane. The water has no idea whether the lateral plane is located on the centerline or off the centerline of the boat.

And, it is also worth noting that Camper 640 uses a distributed lateral plane shared between the large rudder and the daggerboard being a bit forward of the location considered "normal". This reflects things learned in water tests done with Bolger's Dart Dinghy and later with his St. Vallery design.

Eyeballing it, I would bet that Camper 640 actually has more lateral plan than both Nord Coaster and Spartina. I don't understand any physical reason that the greater lateral plane would not make better to windward that both the Nord Coaster and Spartina boats. Why does the pretty boat seem to go better to windward?

I could hear an argument about the effect of the slot top cabin on Camper, but this is offset by the greater width of the other two boats that also contributes significant top hamper too. I am just trying to tease out the physical reasons from the aesthetic reasons in the 'conventional wisdom' here.

[DGentry]

Aesthetics were never in my consideration or explanation for sailing ability here.

The width of the low sided Koster and Spartina is not adding to instability - it is substantially adding stability. Camper, being narrower and having a much, much taller hull/deck - ergo much more mass up high - is naturally going to be less resistant to heeling forces than the lower, wider boats. I'd rather be in a Camper than a Spartina if they were sitting on their sides (or if I was camp cruising), but traditional hard chine sharpies, even those with low sides, are typically not renowned for their windward ability, esp in choppy conditions.

Here's the Camper 640, for those who are curious.


I hadn't so much as glanced at a pic of Camper in months, and forgot she didn't have leeboards like the William D Jochems.
But lateral plane is definitely not lateral plane. High aspect ratio underwater foils are definitively more efficient for upwind work, for one thing (assuming a hull and sails that can take advantage of that), and leeboards themselves - surface piercing foils - just don't work as efficiently as end-stopped, fully submerged foils like centerboards, daggerboards, or bilgeboards. This is both well established, and something that Bolger said himself (which, offhand, I can not document). Practically speaking, it is evident in the fact that purpose built racing boats of all types that could opt for leeboards never do so.
- Excepting for homebuilt boats, of course.

All that being said, Camper 640 might sail just fine. I still think that Spartina - and likely Nord Koster - would be better going to weather, though.

[brucehallman]

DG:"The width of the low sided Koster and Spartina is not adding to instability - it is substantially adding stability. "

There are three ways to resist overturning: width (like Spartina), deep ballast (like Marconi sloops), or high reserved buoyancy (like Birdwatcher or Camper 640).

Boats like Birdwatcher and Camper640 are supposed to heel over a lot while sailing. This isn't a failure of "stability", but merely the nature of their design.

DG:"...but traditional hard chine sharpies, even those with low sides, have never been known for their windward ability, esp in choppy conditions."

I agree when compared to fin keeled Marconi rigs. This is attributable to three things: the high tension jib stay (aerodynamics), the effect of engineered high aspect ratio foils (hydrodynamics), and the high mass of their ballast (mass for busting through chop).

We were comparing Nord Coaster, Camper640 and Spartina, and none of these have a jib stays, massive ballast or high aspect foil keel.

DG:"... end-stopped, fully submerged foils...well established, and something that Bolger said himself (which, offhand, I can not document). "

I agree with you about this...if we are talking about engineered high aspect ratio foils which most swinging boards are not.

I am trying to remember the passage of Bolger about leeboards that you are recalling...it would be interesting to collect together his opinions about leeboards...I agree that he stated that they have their drawbacks.

One benefit is that the lateral plane area is measured from the waterline in the case of leeboards, and not measured from the lowest point of the hull as with centerboards.

DG: "All that being said, Camper 640 might sail just fine. I still think that Spartina - and likely Nord Koster - would be better going to weather, though.

I am just trying to tease out the physical reason you believe this. Is it that Camper640 is hard chined? Is there evidence that hard chined boats don't go to windward as well as short wide rounded boats like Spartina. I was tempted to guess that this was a "ugly vs. pretty" subconscious bias, but you say it is not.

[James McMullen]

A friend and I did an experiment with a couple of super quick and dirty Bolger Teal's many years ago. Sam built his exactly according to spec, clamp-on leeboard and all. Because I had been a little dis-satisfied with the performance of the leeboard on the Chamberlain dory-skiff I had built, I made a daggerboard case on the other one and jammed the stock leeboard in it as a daggerboard. The difference was unequivocal, even for a couple of young, brash, not particularly skilled sailors. Both Sam's Teal and the dory-skiff got daggerboards too, immediately after, and I've never bothered with a leeboard since.

The explanation I've heard is that the surface-piercing foil of a leeboard is much more prone to developing unfavorable spanwise turbulence than an end-stopped fully submerged foil like a CB or DB.

The most interesting thing to me about the Nord Koster design is that I am using essentially the same size rig in a boat that weighs less than half as much in Rowan. Different strokes for different folks, of course. But I will note that the double-ended lapstrake lug yawl Rowan, with her fully submerged CNC machined NACA section foils, is indeed renowned for her windward ability, esp in choppy conditions.

[brucehallman]

surface-piercing foil of a leeboard is much more prone to developing unfavorable spanwise turbulence than an end-stopped fully submerged foil like a CB or DB.

Why might this be? What is the physics making this happen. I cannot imagine that a home made Teal daggerboard/leeboard is achieving much NACA foil laminar flow either "end stopped" or not. Without laminar flow, I cannot imagine this 'lack of end stopping' increasing the turbulence of flow. Excuse me for asking, I am just trying to tease out the physics from the conventional wisdom.

[Steve Paskey]

Boats like Birdwatcher and Camper640 are supposed to heel over a lot while sailing. This isn't a failure of "stability", but merely the nature of their design.

That's true in principle, but in the case of Camper (no. 640) it appears that the original design does, in fact, lack sufficient stability.

If I remember correctly, the only person to build Camper sold his boat without trying to sail it. The builder had sailing experience, but after raising the mast without a sail he apparently concluded that the boat was too top heavy to stand up to sail in even modest winds. I haven't seen any updates, so I don't know whether the new owner has tried to sail it.

[brucehallman]

That's true in principle, but in the case of Camper (no. 640) it appears that the original design does, in fact, lack sufficient stability.
If I remember correctly, the only person to build Camper sold his boat without trying to sail it. The builder had sailing experience, but after raising the mast without a sail he apparently concluded that the boat was too top heavy to stand up to sail in even modest winds. I haven't seen any updates, so I don't know whether the new owner has tried to sail it.

True. I am personally of the opinion that the report from the owner was naive. (I think that a lot of people would find it disconcerting to sail at extreme angles of heel.) And, I interpret SA's comment to be that disconcerted owners deserve to feel better about extreme angles of heel, and this could be fixed with 200 pounds of lead fastened to the bottom.

That said, with the windows being watertight in this type of sailboat, they are stable in principle. (Meaning, they retain righting moment at extreme angles of heel.) Both Camper640 and Birdwatcher are designs that rely on the occupants of the boat being seated and serving as live ballast. When I look at the stability curves, these boats appear to be self righting from even a 90 degree knockdown. (Except with this caveat!) The Achilles heel with both of them is the wildcard of the shifting live weight of gear. If there is 300 pound of beer in a cooler that gets shifted to a high C.G. in a knockdown, then it would be less 'self righting' until after you drink, or relocate the beer to a lower center of gravity. I don't see these boats easily turning turtle.

[James McMullen]

Without laminar flow, I cannot imagine this 'lack of end stopping' increasing the turbulence of flow.

No need to imagine anything, the phenomenon of surface piercing foils has been very extensively studied, both mathematically and with empirical and tank testing. High speed hydrofoil vessels are especially concerned with these surface piercing effects, and there has been an awful lot of published research on it. The primary issue is ventilation from the air/water interface. This sort of turbulence rapidly degrades lift, especially for foils operating at an angle of attack as is seen of a boat sailing to windward. Some other issues can include the wave drag and from interaction turbulence of a "separate hull" moving above its natural hullspeed if the leeboard is far enough from the main hull to behave somewhat independently of the flow from the main hull.

Fully submerged bodies behave differently than those working at the air-water interface. The interface necessarily adds some drag--this is why modern nuke subs can go so very much faster when submerged than when traveling on the surface.

[brucehallman]

No need to imagine anything, the phenomenon of surface piercing foils has been very extensively studied, both mathematically and with empirical and tank testing. High speed hydrofoil vessels are especially concerned with these surface piercing effects, and there has been an awful lot of published research on it. The primary issue is ventilation from the air/water interface. This sort of turbulence rapidly degrades lift, especially for foils operating at an angle of attack as is seen of a boat sailing to windward. Some other issues can include the wave drag and from interaction turbulence of a "separate hull" moving above its natural hullspeed if the leeboard is far enough from the main hull to behave somewhat independently of the flow from the main hull.

Fully submerged bodies behave differently than those working at the air-water interface. The interface necessarily adds some drag--this is why modern nuke subs can go so very much faster when submerged than when traveling on the surface.

And experiment with a Teal's leeboard/daggerboard is neither high-speed nor a foil. I just glanced at some of this hydrofoil research and see that the essence, I believe, is the problem with air ingress from vortices. How is this applicable at slower speeds where their is not air ingress?

[James McMullen]

There is an air ingress vortex that travels down the leading edge at even very moderate speed, my friend. The faster you go, the further it can travel, but it is always there at the air-water interface. But I dont ask you to take my word for it, build yourself a couple of Teals and test it out for yourself.

You don't need to do thought experiments and careful theorizing or complex computer modeling to answer this question. Even someone with minimal sailing experience can figure out better pointing and less leeway slippage with a handheld GPS, or better yet by sailing side-by-side with an otherwise identical boat. Do a real-life empirical test rather than all this theorizing and parsing of the sacred revealed texts and scripture of the Mighty Bolger. It won't take you more than a weekend or two and a couple hundred bucks to conclusively answer the question to your own satisfaction without needing to guess . . .and then you'll even have a couple of cute little sailboats to use or even just give away to the local Boy Scouts or something as a bonus.

[brucehallman]

There is an air ingress vortex that travels down the leading edge at even very moderate speed, my friend.

Amazing, you see an air vortex on your Teals? I don't see it on my Teal. I guess I will have to look again.

[DGentry]

Two boat testing is well proven - just ask DC. But, regardless of the perceived results of any two boat Teal testing, I reiterate that one need only look at serious racing boat design. Remember - there are rich men's egos on the line! If it isn't constrained by arbitrary rules, racing boats are designed for maximum performance in real world conditions. With the advent of computers, nowadays millions of dollars are invested in scientific research and testing to develop the utmost efficiency in every aspect of boat design - whether for rowing shells, racing kayaks or round-the-world ocean racing sailboats. I've even seen doctoral dissertations on the bio-mechanics of the ideal racing stroke for kayak paddling! Looks are not a factor, and convenience is never trumped by performance. If flat bottomed, hard chine hulls, of sharpie width, were advantageous, they'd sure as heck be using them. And, if leeboards had any performance advantage over - or even parity with - other foil configurations, you'd be seeing them, too.

That doesn't mean that sharpie hulls or leeboards don't have their place, or can't perform - it just means that they aren't the best option when maximum performance (even in light air) is the issue, and money isn't.

[brucehallman]

...when maximum performance (even in light air) is the issue, and money isn't.

Agreed. And if maximum performance is the criteria, one should stay away from choosing Spartina, Nord Coaster and/or Camper640.

(And in my imaginary triangle course race between these three boats, my money bet would be on Camper640 because it is narrow, longer, has more lateral plane and more sail area.)

If the criteria is non-strenuous pretty boat sailing, I like Spartina best. (This surprises me because I usually prefer double enders.)

[brucehallman]

I reiterate that one need only look at serious racing boat design. Remember - there are rich men's egos on the line!

OMG serious racing?!? <big smile>

The hidden hand fallacy here is the fact that these rich men write their own racing rules. And they have shown a long clear history that their rule committees selectively choose expensive criteria to advance the elitist nature of their clubs. (Originally pushing "working boat" gaff sails out of the club via measurement rules, and since then, much more.)

I would bet that if the racing rules included shoal draft water, that we would see leeboards, chine runners and more.

My favorite proposed rule is that all boats are handicapped by the price of the boat, with the owner declaring their price before the race. The winning boat is then obligated to put their boat up for sale at the declared price at the end of the race. That would equalize things!

[BBSebens]

Unless your going for historical accuracy, why wouldn't you try to make your boat the best it can be? Within reason, of course. And everyones reason will vary.

For example, Im making my boat the best it can be by upgrading the rudder, building a new rig, and messing with the ballast a bit. I may re-make the CB as well...

[brucehallman]

why wouldn't you try to make your boat the best it can be?...And everyones reason will vary.

'Best' is completely subjective. One criteria might be "easiest to build by an all thumbs first carpenter", or another "voluptuously curvy sculpture", or "most ostentatious", or another "best patio platform in the marina". All those are legitimate criteria to wish for in a boat.

[BBSebens]

Quite right you are.

What is the "Best" that you are going for? (not trying to be snippy, snide, or sarcastic.. Im honestly curious)

[brucehallman]

Quite right you are.

What is the "Best" that you are going for? (not trying to be snippy, snide, or sarcastic.. Im honestly curious)

Personally, I favor owning many boats, with each one tailored to do the exact thing you want at any moment in time. I personally don't like to have boats that compromise trying to do two opposing things well. For instance, I believe if you design a boat to be both a racer and a cruiser you end up getting a boat mediocre in both.

[slidercat]

James, a lot of folks have had similar experiences, trading leeboards for daggerboard and seeing an unmistakable increase in windward performance. Thomas Firth Jones is one, and I'm another. We had an 8-Ball as a tender for one of our big boats. Someone gave me a rig of the right size, and I built leeboards to go with it. It was okay, but when I finally got fed up with the leeboards and cut in a board case, it was day and night.

[brucehallman]

What is an 8-ball?

[slidercat]

It's an 8 foot pram from Glen-L. Makes a decent tender.

[brucehallman]

James, a lot of folks have had similar experiences, trading leeboards for daggerboard and seeing an unmistakable increase in windward performance. Thomas Firth Jones is one, and I'm another. We had an 8-Ball as a tender for one of our big boats. Someone gave me a rig of the right size, and I built leeboards to go with it. It was okay, but when I finally got fed up with the leeboards and cut in a board case, it was day and night.

I just looked at the Eightball lines, and if you rested the leeboard against the gunnel and sheerstrake at the balance point, the toe-in angle seems very steep. Excessive toe-in might be the reason for your disappointing experience with a leeboard on an Eightball.

[Nicholas Scheuer]

Concerning leeboards:

My Shearwater Yawl has a pair of assymetric laminar foil leeboards like illustrated in this sketch.

The performance of the bat to windward is had and shoulders above her performance employing the original flat, fan profile boards, both of which fractured right across below their bearing surface against the hull on different occasions under boistrous conditions.

There is one other Shearwater sporting a pair of NACA00 assymetric foils (60%/40% chord proportions) and it is this boat whose performance to windward I was attempting to match. I was more of less successful; a equivacal judgement resulting from the other boat having a more efficient rig, as well as a more able Skipper.

I posted reccently on the WBF in another thread, I cannot understand why those who build leeboard designs still employ flat leeboards when kthe evidence in favor of assymetric foils is so convincing.

There is a wooden sharpie ketch in Australia equipped with a pair of centerboards hung in a common case. The mating surfaces of the boards are flat, while the outboard surfaces are curved. The board appropriate for generating lift is employed on alternate tacks. The boat sails quite well.

As I said, the evidence is convincing, as least to those not totally committed toward engraving ALL the words of Bolger and Peter Duff in stone.

Moby Nick

[slidercat]

That's really not what "toe-in" means, if I'm understanding you. In any case, I added a rubbing strip partway down the board to support it at the proper angle.

Endstopped foils are just more efficient than surface-piercing foils. The science is really not in dispute. I can give you a real-world example that seems pretty unassailable. The Stiletto 27 catamaran was originally produced with a central swing-up foil. This was a very fast boat, much advanced for its time, built of Nomex, very light and well-designed in almost every respect. However. a few were produced with in-hull daggerboard, and these boats were markedly faster than the ones with a surface-piercing foil.

There are applications where leeboards would be appropriate. The Dutch have made quite an art out of boats with leeboards. They have very shallow inland waters, and for them, leeboards were an excellent solution. In very small monohulls, leeboards get the leeway resistance mechanism out of the cabins. They are easier to maintain, for shallow draft working boats.

But if performance is part of your design brief, leeboards, in my opinion, are less than optimal.

[Nicholas Scheuer]

My foil leeboards have wooden cores sheathed in a stout schedule of fiberglass/epoxy.

The lower end design is predicated on my opinion of what constitutes the most efficient shape with the boards trailing aft 45-degrees over a shoal bottom.

Moby Nick

[Nicholas Scheuer]

My boards appear to have no "toe-in" because the designer of the foil told me that the foil itself has a 3-degree angle of attack with the chord centerline parallel to the keel.

Moby Nick

[James McMullen]

I just realized that I am shooting myself in the foot by condemning leeboards like that. In fact, I would most definitely enjoy it if every boat but mine were sporting leeboards when rounding the leeward mark.

They'd probably just handicap my PHRF rating though, but line honors are always glorious no matter what the judges with the calculators say!

[boat fan]

I just looked at the Eightball lines, and if you rested the leeboard against the gunnel and sheerstrake at the balance point, the toe-in angle seems very steep. Excessive toe-in might be the reason for your disappointing experience with a leeboard on an Eightball.

I`m really confused now Bruce ....

I was always under the impression that "toe-in " referred to the angle the board makes in relation to the longitudinal center line , in plan view ?.

Have I had this all wrong all this time ?

[htom]

You could (not going to say it would be easy) build leeboards with both endplates and "surface plates", just below the DWL. How large would the plates have to be to make them equal the performance of an foil stopped in the hull, or midway between plateless and hull-stopped?

[boat fan]

You could (not going to say it would be easy) build leeboards with both endplates and "surface plates", just below the DWL. How large would the plates have to be to make them equal the performance of an foil stopped in the hull, or midway between plateless and hull-stopped?

That would be easier to do with a dagger board style bilge board.
Should work well.

[John Meachen]

I just realized that I am shooting myself in the foot by condemning leeboards like that. In fact, I would most definitely enjoy it if every boat but mine were sporting leeboards when rounding the leeward mark. :

They'd probably just handicap my PHRF rating though, but line honors are always glorious no matter what the judges with the calculators say!

Only six days ago I was looking at a C-Class catamaran that had assymetric foil section daggerboards.The boats designers are employed by Airbus and might be expected to know a bit about fluid dynamics.Only a few inches of location between the definitions of leeboards and daggerboards.Good design always succeeds.

[Nicholas Scheuer]

No, boat fan, you have "toe-in" right, angled in the plan view.

There are advantages both ways in angling leeboards either inward or outward (relave top an end view) but all that has to do more with roll resistance than anything else.

As for end plates, htom, I may be biased, but after years of sailing Dovekie and Shearwater (both advertised by E&D as "Shoal Draft Champions") I would not be at all interested in leeboards having end plates. I've sailed too many leagues with a leeboard trailing aft over a shoal bottom. Wouldn't it be lovely having an end plate dragging through the water at an angle like a drogue.

Moby Nick

[htom]

Making the end/top plates tilt would complicate things, one scheme would be the foil in two parts that slide on each other, the plates attached to each of the foil parts.

[brucehallman]

That's really not what "toe-in" means, if I'm understanding you. In any case, I added a rubbing strip partway down the board to support it at the proper angle.

Yes, I am asking if your redesign of the Eightball lateral plane involved correct fore-aft location and angle of the leeboard, as perhaps some mislocation might have skewed your experiment. Also, I am questioning if there is some Observer-Expectancy Effect in your test.

Endstopped foils are just more efficient than surface-piercing foils. The science is really not in dispute. I can give you a real-world example that seems pretty unassailable. The Stiletto 27 catamaran was originally produced with a central swing-up foil. This was a very fast boat, much advanced for its time, built of Nomex, very light and well-designed in almost every respect. However. a few were produced with in-hull daggerboard, and these boats were markedly faster than the ones with a surface-piercing foil.

Actually, the research I saw about surface-piercing foils involved hydroplane research which evaluated much higher velocities than we see here with dingy sailing. I don't dispute the research at high velocities, but what about the lower velocities? Is there research data "science" whether the effect is significant at these lower velocities?

Can I read this Stilletto 27 data somewhere, or is this anecdotal?

Pardon me for being skeptical of anecdotal 'evidence'. Just asking.

But if performance is part of your design brief, leeboards, in my opinion, are less than optimal.

It is sloppy to simply say "performance" as if it is a binary thing.
There are many types of performance, speed reaching, speed running, and there is also the issue of performance measured in ergonomics, where cruising space is ruined by a centerboard trunk, and/or the issue of shoal draft. Sailing is a holistic activity involving, cost benefit trade offs of many aspects of performance and the quality of the sailing experience, and being vague about 'performance' implies a bias and sometimes sounds dogmatic.

[boat fan]

Making the end/top plates tilt would complicate things, one scheme would be the foil in two parts that slide on each other, the plates attached to each of the foil parts.

Bolger`s Insolent 60 ?

[htom]

Ohhhh I'd never heard of that one! Yes, like that.