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Bull City

Skerry Cruisers

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I have been smitten by Skerry Cruisers. I thought others may been too, and that it would be an interesting topic. I recently added a post to the Swede 55 topic in Sailing Anarchy, and I'll begin with that.

 

Not a Swede 55, but a 22 Square Meter. If a video ever came within inches of making me loose my senses and buy a boat that I wasn't equipped to maintain, this is it. And it only took 1 1/2 minutes.

 

 

Long, lean, close to the water, tiller.

 

 

And then you take a look inside and realise you have to either stick to daysailing or go up in size, as

 

(launch of a SK 95), or

 

(SK 75 sailing), or

 

(SK 75 Bacchant, re-taken from US)

 

and so on.

 

Here you see the inside of Tor's SK55 (from 1917):

From the re-framing in 2011, Cooking!

 

/J

 

 

 

Not a Swede 55, but a 22 Square Meter. If a video ever came within inches of making me loose my senses and buy a boat that I wasn't equipped to maintain, this is it. And it only took 1 1/2 minutes.

 

Long, lean, close to the water, tiller.

 

That's a real beauty, Bull. A jewel of a boat. I can almost feel the tiller from watching it.

 

But it did make me think that varnish might be cited as a co-respondent in divorce proceedings ;)

 

 

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I will be the first to reply to this exciting new topic. I picked this image of a Skerry Cruiser from You Tube. I'm struck by the curved mast. Is that permanent?

post-54228-0-45539200-1481648810_thumb.jpg

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BC, great topic and one that should have a high potential for boat porn. Look to see our own KimB add his experience(s). Of course, Frankie, is the ultimate evolution of a Skerry Cruiser. Given my own experience with a Yankee One Design (sort of a Skerry cruiser without the extended overhangs), the sailing experience is unparalleled by most any other designs today. Some are faster, most are roomier but for the simple joy of sailing, few can beat 'em.

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I grew up saililg on Lake Starnberg, south of Munich and there was quite a fleet, IIRC

 

Here is a newly built 30 square meter Skerry Cruiser, quite unusually a double ender.

 

Article (in german): http://segelreporter.com/blogs/braschosblog-der-doppelender-schaerenkreuzer-kaa-von-jo-frowein/

More pics: http://segelreporter.com/fotostories/sr-bilderstory-ueber-die-doppelender-schaere-kaa/

 

img_0169v.jpg

 

foto.jpg

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I am attracted by how easily-driven Skerry Cruisers are. That should make them the ideal cruising boat for people who really like sailing, and can understand the difference between a boat and a floating loft apartment.

 

But it's sad to see how few boats have developed the theme. The Swede 55 is a 40-year-old design. The marginally-newer Aphrodite 101 fascinated me at the time as an attempt to update the concept, but it failed in many ways, and ended up as a sort of super-slim IOR boat which found a niche only on lakes. There seem to be some newish boats which are replicas of the old metre-boat-derived vessels, and a few pastiches such as the Rustler 33 ... which to my eyes is yet another aesthetic failure from that designer.

 

While I was writing the above, Veeger posted to point out that Frankie is the ultimate evolution of the concept. Absolutely right: all the virtues of slimness, but with added lightness, righting moment and low-wetted-surface slipperiness.

 

I would love a 40-foot Frankie. Build it light and keep it simple (like Frankie), and you'd have the perfect 2-person antidote to the 15-month-pregnant barges which sell at the boat shows.

 

C'mon, Kim, please develop the prototype. Frankie needs a little sister to keep her company on that slip ;)

 

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My parents had an International Dragon.

I had a Reimers 30 Square Meter and a Reimers Swede 55.

 

Clearly those vessels had a major influence on the Sliver Project that produced FRANCIS LEE.

 

(The Swede 55 and FRANCIS both have heads. We used a bucket ala LFH on the Dragon and the 30.)

 

A 40' version of FRANCIS would not have headroom or decent accommodations, such a vessel would not fulfill my desires. And with true 30's available for purchase why bother? Closest I have seen was Bruce King's Nantucket Splinter, and she had an extremely cramped interior just like my 30. But they all (including the Dragon) make wonderful daysailer!!

post-8115-0-91815900-1481654901_thumb.jpg

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If you get older, things like a head will matter more.

 

Depends. I'm a 50-something woman, but I have never been one to believe that a full set of suburban facilities is the only way to live.

 

Check http://www.saffieryachts.com/

I believe they have a larger then 30 fter in the pipeline.

 

The Saffiers don't look to me like evolved Skerries ... or at least, not evolved in a direction I like.

 

Their Sc 10m Cabin is light and narrowish, but is clearly aimed at the same retro-daysailer market as the Morris Yachts M-series. Excessive overhangs for that retro look, and wheel steering to take the joy out of sailing, and electric winches to further disconnect you from the fun.

 

The Se 33 has a more evolved hull shape and isn't aiming at the retro look, bit it's still playing the party-boat game of the modern posh daysailer ... rather than the leans sailing machine of the Skerry heritage.

 

And neither is anywhere as narrow as a true Skerry-boat

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Jammer,

 

I talked to a guy with a couple of Dragons at a Xmas party last week and his Uncle had the Cruising Dragon that I mentioned in an earlier thread that you had started. I think that they have taken all three boats up to Maine. The heat and sun down here on the Gulf Coast were too much to keep up with on the varnish work.

 

015-3.jpg

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I first drew the sail plan for Frankie with a curved topmast like you see on the 30 sq. m's. Sailmaker did not approve. Then we went with the Farr 40 rig and it was a moot point. Too bad.

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Ehum,

 

Dragons are not SK's. They might be long and narrow, but that is not sufficient to be a SK (SkärgårdsKryssare). Actually, a Dragon is not so long, not so fast then. Heavy compared to a SK.

 

As SK's main measure is the sail area (eg 22 sqm, main + 85 % headsail), it can be instructive to compare a Dragon with comparable SK: A dragon has about 22 sqm, the same as SK 22 has. Dragon is 8.9 m LOA, a SK 22 is typically 12-16 m LOA.

 

SK 22 were / are very popular, as costs are reasonable. Simplifying further resulted in the B22, which still is a SK. Then those which are not that simplified are A22. A even more cost reduced version was the M22 - similar, but not really a SK.

 

Wasn't it Uffa Fox who had a SK22 on the book cover, or even on the hard book cover - story was he sailed the SK22 non-stop from England to a race in Sweden as he was not allowed to race it in English waters. As he was late to the start he went directly into the race - this in a SK22 which has about zero volume inside.

 

There are modern SK22, Peter Norlin designed at least one. Many alternatives made in GRP, Swede 30 one step up in size, Lotus, and so on. Agree that the Aphrodite 101 is not really a SK, it is more a good example of long & narrow - which leads into all the Danish design of such sailboats (not here and now).

 

Going up in size there are (were) 30, 40, 55, 75, 95, 120, and 150 SK's. Some of the larger has been re-classed to a lower class by decreasing sail area. The 150'ies are large beasts!

A smaller class does also exist, SK15.

 

Over 1200 boats have been built since 1908, most of these in wood. Many still exists, owners are keeping many of these in good shape - sometimes a huge work as can bee seen in the video clip where Tor is re-framing his SK from 1917 (see first post in this thread).

 

Still popular to sail SK:s: In the harbour where I have my (non SK) boat there are some few wooden SK, one 30, 2-3 55 (larger SK would be too large for this harbour, in terms of length, depth and weight).

On the more modern kind 2-3 Swede 30, 4-5 Wasa 55 (not really a SK I think) and a number of others.

 

/J

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If you get older, things like a head will matter more.

 

Depends. I'm a 50-something woman, but I have never been one to believe that a full set of suburban facilities is the only way to live.

 

No, it doesn't. If you're lucky, you'll see.

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Dragons were the compromise I was willing to settle for. What I want is a Skerry with some living accommodations.

That glass one has a porta pottie

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My favorite square meter - the Tumlaren (Porpoise in Swedish, it's a 22 sq).

 

post-2611-0-19440200-1481679429_thumb.jpg

 

post-2611-0-96587800-1481679458_thumb.jpg

 

Adlard Coles had a Stor Tumlaren named Cohoe I (Stor = Large in Swedish ~32 feet/7000 pounds/33 sq meters of sail). Several of the chapters in earlier versions of "Heavy Weather Sailing" featured his experiences in her.

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Dragons were the compromise I was willing to settle for. What I want is a Skerry with some living accommodations.

That glass one has a porta-potty

 

 

Needs more than that for overnight races. Needs minimal berths, galley and head. It can be spartan. It can be bivouac, not camping, but there's a minimum. Crew off watch has to sleep safely, everyone needs to eat, everyone needs to process that eating.

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My favorite square meter - the Tumlaren (Porpoise in Swedish, it's a 22 sq).

 

attachicon.gifPT2010.jpg

 

attachicon.gifWBSHOBART2007311.jpg

 

Adlard Coles had a Stor Tumlaren named Cohoe I (Stor = Large in Swedish ~32 feet/7000 pounds/33 sq meters of sail). Several of the chapters in earlier versions of "Heavy Weather Sailing" featured his experiences in her.

Sam, how is it that the Tumlaren is a 22 SqM? Its sail area is just shy of 20 SqM according to Sailboat Data.

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Check http://www.saffieryachts.com/

I believe they have a larger then 30 fter in the pipeline.

 

Those look sweet but the wheels are ridiculous.

 

Sloop, I agree 100%. Would you have a wheel on a Lightning?

 

Saffier 26 foot open daysailer. The wheel is ridiculous (IMHO).

post-54228-0-65014300-1481685912_thumb.jpg

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If you wanted a little more furniture you should look at an 8 meter. A little heavier but still get that feel of watching the water rush by about 6" below your nose. And power going to weather. Or maybe an R. Wet ride, no freeboard, but real sailing.

If you are in PNW look for a converted 6 called Erne. She was a big 6 and made a nice conversion.

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Dragons were the compromise I was willing to settle for. What I want is a Skerry with some living accommodations.

That glass one has a porta-potty

Needs more than that for overnight races. Needs minimal berths, galley and head. It can be spartan. It can be bivouac, not camping, but there's a minimum. Crew off watch has to sleep safely, everyone needs to eat, everyone needs to process that eating.

No dog in the hunt, but the glass one looks to have 4 singles. Nothing about a galley. jet boil and a cooler?

 

Not the boat for me yet. I think I have one more ocean boat in me.

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Skerry's have been using that curved mast for decades. Comes close to the holy grail of the 'elliptical planform'.

Is the curved mast sort of like the big flat headed main? Can someone explain "elliptical planform?"

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Cute little (glass) one for sale in US

 

http://m.sailboatlistings.com/sailboats/30%20sq%20meter

 

That's on the wrong coast for me! Bummer... looks very much like a 6-meter I was once involved with, maybe a bit slimmer if possible. Ours had a tiny pot-belly stove in it, very cute but the boat found itself in Florida. There's almost as much room in those cabins as there is crouching under your dining room table.

 

That 20sq looks like it was a very well done project, somebody expended a lot of time & effort on her... hope she goes to a good home.

 

FB- Doug

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Bull:

I'll give you a quick and dirty explanation:

 

Elliptical means a portion of an ellipse. Planform means a plan view, usually a profile, of an object. In this case it's the "side view" or profile of the rig. If we were talking about keels the planform would be the profile of the keel.

The theory behind the elliptical planform is that it preserves the greatest lift for the lowest drag and reduces tip vorteces. The famous Spitfire wing tip is a classic example. If all limitations were removed from a design, the keel and rudder might have elliptical planforms. But it's a balancing act and it seldom works so foils just get chopped off for a number of reasons.

 

If memory serves, the British designer David Boyd tried the curved mast tip on one of his 12 meters. I think he did it to gain some unmeasured sail area.

 

The masts of those Skerry cruisers were built with the curve laminated into the spar. They were bent out of the box.

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If memory serves, the British designer David Boyd tried the curved mast tip on one of his 12 meters. I think he did it to gain some unmeasured sail area.

Lionheart, for the 1980 America's Cup. Designed by Ian Howlett for Tony Boyden. (Quickly) copied by the Aussies for Australia.

 

Australia-mast-bend.jpg

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Thanks for the correction on that Ed. I had totally forgotten abut Ian Howlett. Failing in an America's Cup bid back in those days was an easy way for any designer to fall off the map. Where did Howlett go?

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Herreshoff's S Boats had a permanently curved mast. Designed in the teens, I think? Apparently the advantage of an elliptical platform was known by aerodynamicists, even if they didn't know why.

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SA thread from 2013: http://forums.sailinganarchy.com/index.php?showtopic=150338

 

Comment from the thread:

 

That boat, while suffering from limited funds, was the epitome of the Hamble school of sailing, with John Oakeley leading the project seconded by Barrie Perry (Proctor's boss): they are famous for their "bendy" rig.

In the first pic you can see that adding area up the mast was their motto (one could think John "O" was pushing for this too with the one-tonner)

If I understand correctly, the idea of "adding area up the mast" was to combat the fault of the triangular marconi rig of the top being too skinny. I think I remember a graph from wind tunnel tests by Marchaj showing a better lift/drag ratio for the bent mast. Even a slightly bent mast. Whether they got a benefit in actual square feet would depend on the exact method of measuring sail area prescribed by the rule. I don't know anything about that. And, of course, if you could take advantage of the concept depends on the skill of the sailmaker.

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I knew a guy who long ago raced a Dragon in PHRF or some other mixed class races here in WLIS. He said they didn't have enough sail area for our light winds and the big over-lapping genoa was a pain. This was back when 170% genoas were in vogue.

 

Bill Luders wrote that he felt the Luders L-16 was a better boat for these waters. (Well, he would, wouldn't he!)

 

IMG_5110.JPG?format=500w

 

L-16_Construcion_Plan_thumb.jpg

 

Seems similar to a layman. What is the essential difference?

 

More info here.

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Skerry's have been using that curved mast for decades. Comes close to the holy grail of the 'elliptical planform'.

Is the curved mast sort of like the big flat headed main? Can someone explain "elliptical planform?"
https://en.m.wikipedia.org/wiki/Elliptical_wing

 

Spitfire.planform.arp.jpg

 

I think it's technically more elliptical lift distribution, but how can any airplane inspired by the flight of swallows be wrong? There was a glider pilot named, IIRR, Schumacher that thought tip rake back ordered flow better along the chord lines of the wing as a whole, rather than flow getting more confused at the tip with a straight leading edge. Which he thought is a more advantageous method to control tip vortexes. He used tufts on the wing to confirm the flow. Gaff rigs (among other rigs with spars tipped back) were doing that, although with a shitload of drag from all the stuff up there. Gunter's a pretty good compromise, and has a lot of advantages, especially when reefed, as far as CoG, gust response , and scandalizing.

 

Fatheads are about twist (washout?) and tip vortex control. I understand that they can also develop elliptical lift distribution, or at least a close facsimile.

 

I keep reading the main advantage of the Spitfire was that because of the wing it could turn tighter than the Me 109.

 

Look at Windsurfer mast/sail development.

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This from Amati made me wonder about mast rake. Is it related?

 

There was a glider pilot named, IIRR, Schumacher that thought tip rake back ordered flow better along the chord lines of the wing as a whole, rather than flow getting more confused at the tip with a straight leading edge. Which he thought is a more advantageous method to control tip vortexes. He used tufts on the wing to confirm the flow. Gaff rigs (among other rigs with spars tipped back) were doing that, although with a shitload of drag from all the stuff up there.

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Bull:

When I opened my office I was reading glider mags and I noticed that most of them had the trailing edge nipped off at the tip, not the leading edge. If you look at my rudders once you get past the Valiant 40 you ca see that shape.

N447%20alu%20lines_zpsyypic6os.jpg

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When I had my Shark, I bought a beautiful elliptical rudder for it. there were two choices, One had the tip lopped off and the other not. The full version was deeper than the lopped off version, which had the same depth as the original rudder. I opted for the full elliptical shape. I always had a bit of a vibration in the rudder, most noticeable on light air days, which I attributed to the bottom of the rudder extending into the turbulence from the keel. I wonder now whether it had to do more with turbulence coming off the tip off the rudder.

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Py:

A vibration at certain speed is often caused by asymmetry in the rudder blade. Sometimes it's a function of how the trailing edge is shaped. A round trailing edge is to be avoided as is a knife sharp trailing edge. A nice, crisp little flat trailing edge works best. Some like to chamfer it off at 40 degs.

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Bob, Amati and others, thanks for enlightening me about elliptical planform. I think I'm beginning to understand it. So this 34' Swordfish has some elliptical looking underwater appendages. Is this the idea? There should be less turbulence from the tip?

 

post-54228-0-12958600-1481824590_thumb.jpg

 

On the other hand, here is a line drawing of my H-Boat. The rudder and keel look kind of chopped off. Am I a turbulence machine?

 

post-54228-0-90483400-1481825001_thumb.jpg

 

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Bull:

Yes, that Swordfish is a pretty radical example of elliptical planform but I don't care for the taper of either blade. To my eye there should be more taper towards the tip. Go back and look at that Spitfire photo.

 

On your boat the designer had to choose how much draft he could work with. With that draft established giving the keel an elliptical planform would have significantly raised the ballast VCG. That's the downside of an eliptical keel. If there is a rating rule involved you may not want to pay for that extra draft.

 

Consider also that with a true elliptical tip you cannot set the boat on the keel when you haul out. It's not a convenient shape for a cruising boat.

 

A couple more posts like this and I will be able to spell eliptical.

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@Bull

Chopping off the end is not an absolute sin, later Spitfire had chopped wings and were better in some conditions.

 

 

mk14.jpg

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I think the "elliptical" part of this get's confusing. There is an elliptical profile and then there is elliptical loading which I think you can get without an elliptical planform.

 

Elliptic Loading is a force distribution on a wing that has an elliptical form in the spanwise direction. It is well known that this load distribution results in the least induced drag for a given wing span, and total lift.

 

Those Swordfish appendages look funkeeeeee.

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It also appears the Swordfish rudder kicks up...considering the pivot mechanism and it's reinforcement, I doubt the rudder is as hydrodynamic as it appears in plan view. The same may go for the swing keel.

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Back to the subject

 

Bull:

Yes, that Swordfish is a pretty radical example of elliptical planform but I don't care for the taper of either blade. To my eye there should be more taper towards the tip. Go back and look at that Spitfire photo.

 

On your boat the designer had to choose how much draft he could work with. With that draft established giving the keel an elliptical planform would have significantly raised the ballast VCG. That's the downside of an eliptical keel. If there is a rating rule involved you may not want to pay for that extra draft.

 

Consider also that with a true elliptical tip you cannot set the boat on the keel when you haul out. It's not a convenient shape for a cruising boat.

 

A couple more posts like this and I will be able to spell eliptical.

This drew a snort of laughter.

 

I found this image which really illustrates radical differences in design: freeboard, overhangs, mast rake. I would not be surprised of the the two boats had close to the same LWL. It's nice boat pornography too. Incidentally, I think Kim B took the photo. See more at http://www.squareskerryyachts.net/30sqm/hansinas185us44/launch-of-hansina/

 

post-54228-0-09000400-1481829973_thumb.jpg

 

 

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Long and skinny.

 

Seriously, That's a very nice shot. I very ,much like the way the masts line up

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Bull:

Nope: Boats that skinny rarely have any helm at all. Maybe the mast isn't far forward, Maybe the back end of the boat just goes on forever. Also remember those masts were built with the curve in them.

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Are there any Skerrys with a cutter rig?

I don't think so. Every pic I've seen of the sq meters they've carried a low-aspect Genoa with a long LP. The Tumlares all appear to be sloop-rigged also. Possibly some very early Universal rule boats (Rs, Qs) were cutter rigged. The Js were.

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This from Amati made me wonder about mast rake. Is it related?

 

There was a glider pilot named, IIRR, Schumacher that thought tip rake back ordered flow better along the chord lines of the wing as a whole, rather than flow getting more confused at the tip with a straight leading edge. Which he thought is a more advantageous method to control tip vortexes. He used tufts on the wing to confirm the flow. Gaff rigs (among other rigs with spars tipped back) were doing that, although with a shitload of drag from all the stuff up there.

 

This is more a Schumacher influenced wing: note the straight trailing edge, span wise.

 

 

post-906-0-40925600-1481838271_thumb.jpg

 

 

IIRR, The lower the AR, the more rake back at the tip, and the closer to the wing root the rake starts. Kinda like a Gaff and it's ilk, huh?

 

I'll try to find the Schumacher article, but it was in a magazine. An old Soaring(?) magazine. Neat pics

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Another bendy mast. The rig seems very far forward - to correct for weather helm?

attachicon.gifSqM tabu.jpg

 

If you look where the leech of the 40 square jib is, its pretty much at the point of max speed flow of the low pressure side of the main, which means the flow at the leech of the jib doesn't have to slow down as much, which means the flow on the low pressure side of the jib doesn't have to slow back down as much as well (thank, you Mr Kutta), so it is less likely to get stressed out and break down (or out :lol: if you prefer), never to reattach. Less drag.

 

Also puts a higher pressure regime at the mast, which, depending on your belief system, is either good or bad. :wacko:

 

Edit-Gentry liked a 165% jib, for this reason.

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post-906-0-80671500-1481839496_thumb.jpg

 

Ah- found an image of a page of the Schumacher article I had in the laptop- hopefully it isn't too small. ( it isn't if you click on it) Sorry I can't find the whole article, but this page is, I think the crux of his argument.

 

post-906-0-14190800-1481839529_thumb.jpg

 

And here (above) a cartoon I did for different AR wings based on Schumacher's criteria

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Back to the subject

 

 

Bull:

Yes, that Swordfish is a pretty radical example of elliptical planform but I don't care for the taper of either blade. To my eye there should be more taper towards the tip. Go back and look at that Spitfire photo.

 

On your boat the designer had to choose how much draft he could work with. With that draft established giving the keel an elliptical planform would have significantly raised the ballast VCG. That's the downside of an eliptical keel. If there is a rating rule involved you may not want to pay for that extra draft.

 

Consider also that with a true elliptical tip you cannot set the boat on the keel when you haul out. It's not a convenient shape for a cruising boat.

 

A couple more posts like this and I will be able to spell eliptical.

 

This drew a snort of laughter.

 

I found this image which really illustrates radical differences in design: freeboard, overhangs, mast rake. I would not be surprised of the the two boats had close to the same LWL. It's nice boat pornography too. Incidentally, I think Kim B took the photo. See more at http://www.squareskerryyachts.net/30sqm/hansinas185us44/launch-of-hansina/

 

attachicon.gif2009_0813 BlakelyHbr_Bottles.jpg

Yes, I took that picture. That is HANSINA a Becker designed 30 that belongs to my friend George Fisher of Portland, Oregon. She was on our mooring buoy for a couple Summers. I believe she is the longest 30 ever built at 46' LOA.

Bull:

That might be Kim's old 30 sq. m. The boy does like his boats skinny. Maybe Kim's was green.

Skinny boats go through the water best........

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A couple of posts have distinguished between an elliptical plan form and elliptical loading. The supposed optimality the Spitfire-style elliptical wing was based on a theoretical result. Meaning calculus. Which is not perfect in the realm of fluid flow.

 

You will note that most wings for subsonic craft have trapezoidal wings which are as good or better that the Spitfire-style. Although the was a fad for elliptical shapes in keels for a while, the fad has run its course, very high aspect ratio foils are now in vogue.

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A couple of posts have distinguished between an elliptical plan form and elliptical loading. The supposed optimality the Spitfire-style elliptical wing was based on a theoretical result. Meaning calculus. Which is not perfect in the realm of fluid flow.

 

You will note that most wings for subsonic craft have trapezoidal wings which are as good or better that the Spitfire-style. Although the was a fad for elliptical shapes in keels for a while, the fad has run its course, very high aspect ratio foils are now in vogue.

 

Correct, and the loading can be duplicated with subtle adjustments to camber in a trapezoidal planform wing. The Brits just liked the elliptical wing tip design but I read somewhere the real reason was they were trying to fit a 20 mm cannon that was so long that the required wing chord was way too big to carry out to the tip. In that case it would have been a real Hershey Bar design and they didn't have the ability to make a wing strong enough to handle the tip loads considering the G requirements of a fighter.

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Bull:

Yes, that Swordfish is a pretty radical example of elliptical planform but I don't care for the taper of either blade. To my eye there should be more taper towards the tip. Go back and look at that Spitfire photo.

 

On your boat the designer had to choose how much draft he could work with. With that draft established giving the keel an elliptical planform would have significantly raised the ballast VCG. That's the downside of an eliptical keel. If there is a rating rule involved you may not want to pay for that extra draft.

 

Consider also that with a true elliptical tip you cannot set the boat on the keel when you haul out. It's not a convenient shape for a cruising boat.

 

A couple more posts like this and I will be able to spell eliptical.

Bob, besides giving me a good chuckle, this post was very informative in a practical way. Thanks.

 

BC

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A couple of posts have distinguished between an elliptical plan form and elliptical loading. The supposed optimality the Spitfire-style elliptical wing was based on a theoretical result. Meaning calculus. Which is not perfect in the realm of fluid flow.

 

You will note that most wings for subsonic craft have trapezoidal wings which are as good or better that the Spitfire-style. Although the was a fad for elliptical shapes in keels for a while, the fad has run its course, very high aspect ratio foils are now in vogue.

 

Correct, and the loading can be duplicated with subtle adjustments to camber in a trapezoidal planform wing. The Brits just liked the elliptical wing tip design but I read somewhere the real reason was they were trying to fit a 20 mm cannon that was so long that the required wing chord was way too big to carry out to the tip. In that case it would have been a real Hershey Bar design and they didn't have the ability to make a wing strong enough to handle the tip loads considering the G requirements of a fighter.

 

It could be convincingly argued that the Spitfire saved liberal democratic society from fascism, and if this was due to the elliptical planform, and the trailing edge fillets that Bob P so admired (as I did), to say nothing of the brave pilots who flew the Spitfires, I am a devoted acolyte.

 

Did the Spitfire designers get it from the Skerry Cruisers?

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Kim,

 

Do you have pics of your Skerry Cruiser? I would love to hear about your experiences. Did you and SWMBO do any cruising or weekending on her?

 

BC

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A couple of posts have distinguished between an elliptical plan form and elliptical loading. The supposed optimality the Spitfire-style elliptical wing was based on a theoretical result. Meaning calculus. Which is not perfect in the realm of fluid flow.

 

You will note that most wings for subsonic craft have trapezoidal wings which are as good or better that the Spitfire-style. Although the was a fad for elliptical shapes in keels for a while, the fad has run its course, very high aspect ratio foils are now in vogue.

Correct, and the loading can be duplicated with subtle adjustments to camber in a trapezoidal planform wing. The Brits just liked the elliptical wing tip design but I read somewhere the real reason was they were trying to fit a 20 mm cannon that was so long that the required wing chord was way too big to carry out to the tip. In that case it would have been a real Hershey Bar design and they didn't have the ability to make a wing strong enough to handle the tip loads considering the G requirements of a fighter.

It could be convincingly argued that the Spitfire saved liberal democratic society from fascism, and if this was due to the elliptical planform, and the trailing edge fillets that Bob P so admired (as I did), to say nothing of the brave pilots who flew the Spitfires, I am a devoted acolyte.

 

Did the Spitfire designers get it from the Skerry Cruisers?

Wikipedia is your friend:

The elliptical wing was decided upon quite early on. Aerodynamically it was the best for our purpose because the induced drag caused in producing lift, was lowest when this shape was used: the ellipse was ... theoretically a perfection ... To reduce drag we wanted the lowest possible thickness-to-chord, consistent with the necessary strength. But near the root the wing had to be thick enough to accommodate the retracted undercarriages and the guns ... Mitchell was an intensely practical man ... The ellipse was simply the shape that allowed us the thinnest possible wing with room inside to carry the necessary structure and the things we wanted to cram in. And it looked nice.

 

Beverly Shenstone[61]

 

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The story I like about the Spitfire wing was the designer was recovering from some medical Bad Shit in the typical upper class British manner - reclining in a chaise lounge bundled in blankets outside, sipping tea. While engaged in this pursuit, for a month or so, he became enamored of the swallows flying overhead, enjoying speed and maneuver. Elliptical wings, more or less. I really hope he was listening to the 'Lark Ascending' too, a lot, but that is asking too much, I fear. I also hope he did not have some of them shot, for closer examination.

 

Now, this was before the Spitfire and the design was for one of the racers of the 30's, but the same planform. Can't remember if it won or not.

 

Both the Spitfire and the Me 109 were designs based on racers, and speed record holders, which is cool, but gruesome, given the ensuing slaughter of men, in the Homeric sense.

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So when are we going to have to accomodate machine guns in our keels? Think that will keep the whales out of our way?

Or landing gear. Might help if a 'designers' boats have a propensity to hit beaches and reefs.

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The story I like about the Spitfire wing was the designer was recovering from some medical Bad Shit in the typical upper class British manner - reclining in a chaise lounge bundled in blankets outside, sipping tea. While engaged in this pursuit, for a month or so, he became enamored of the swallows flying overhead, enjoying speed and maneuver. Elliptical wings, more or less. I really hope he was listening to the 'Lark Ascending' too, a lot, but that is asking too much, I fear. I also hope he did not have some of them shot, for closer examination.

 

Now, this was before the Spitfire and the design was for one of the racers of the 30's, but the same planform. Can't remember if it won or not.

 

Both the Spitfire and the Me 109 were designs based on racers, and speed record holders, which is cool, but gruesome, given the ensuing slaughter of men, in the Homeric sense.

Racing seaplanes was big in the 30s. IIRC the Italians were particularly good at it. IDK why seaplanes were preferred over land-based aircraft. I suspect the elliptical wing was developed from that.

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Here is a blatant Wiki copy/paste on the Spitfire wing. In addition to the taper it is also important that a wing have wash-out (in sailing terms a loose leach) to have the wing stall at the root first. If your tips stall first then you loose roll authority when the stall covers your ailerons. Not a good thing to have happen in a dogfight with a ME-109.

 

Theoretically, the most efficient way to create lift is to generate it in an elliptical spanwise distribution across the wing.[1] The basic elliptical wing meets this condition.[2] Elliptical taper of a constant-aerofoil section wing shortens the chord near the wingtips in such a way that all parts of the wing experience equivalent downwash, and lift at the wing tips is essentially zero, improving aerodynamic efficiency due to a greater Oswald efficiency number in the induced drag equation.

The superiority of the pure elliptical shape is only theoretical. Wings with other planforms can be optimized to give the necessary elliptical spanwise lift distribution.[citation needed]

The basic elliptical wing shape also has disadvantages:

  • The uniform lift distribution of a constant-aerofoil section elliptical wing causes the entire span of the wing to stall simultaneously, potentially causing loss of control with little warning. To improve the stalling characteristics and give the pilot some warning, designers use a non-uniform aerofoil. For example the wing of the Supermarine Spitfire was both thinned towards the tips and twisted to give washout, reducing the load on the tips so that the inner wing would stall first.[3][4] Such compromises depart from the theoretical elliptical lift distribution, increasing induced drag. Thus, in practice the elliptical planform seldom achieves the theoretical efficiency of an elliptical lift distribution.
  • Elliptical curves are difficult and costly to manufacture.[citation needed] In practice, most elliptical wings are approximations, for example several sections of the Spitfire leading and trailing edges are arcs of circles.

Here is another way to ruin your day

 

article-1311828-0B2D77C6000005DC-701_964

 

This guy had landing gear Koch and it didn't seem to help much in this case.

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The story I like about the Spitfire wing was the designer was recovering from some medical Bad Shit in the typical upper class British manner - reclining in a chaise lounge bundled in blankets outside, sipping tea. While engaged in this pursuit, for a month or so, he became enamored of the swallows flying overhead, enjoying speed and maneuver. Elliptical wings, more or less. I really hope he was listening to the 'Lark Ascending' too, a lot, but that is asking too much, I fear. I also hope he did not have some of them shot, for closer examination.

 

Now, this was before the Spitfire and the design was for one of the racers of the 30's, but the same planform. Can't remember if it won or not.

 

Both the Spitfire and the Me 109 were designs based on racers, and speed record holders, which is cool, but gruesome, given the ensuing slaughter of men, in the Homeric sense.

Racing seaplanes was big in the 30s. IIRC the Italians were particularly good at it. IDK why seaplanes were preferred over land-based aircraft. I suspect the elliptical wing was developed from that.

 

Retracting landing gear is complex, heavy and requires thickness. Pontoons were lighter, more aerodynamic, and the bracing allowed for a much thinner wing.

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Here is a blatant Wiki copy/paste on the Spitfire wing. In addition to the taper it is also important that a wing have wash-out (in sailing terms a loose leach) to have the wing stall at the root first. If your tips stall first then you loose roll authority when the stall covers your ailerons. Not a good thing to have happen in a dogfight with a ME-109.

Theoretically, the most efficient way to create lift is to generate it in an elliptical spanwise distribution across the wing.[1] The basic elliptical wing meets this condition.[2] Elliptical taper of a constant-aerofoil section wing shortens the chord near the wingtips in such a way that all parts of the wing experience equivalent downwash, and lift at the wing tips is essentially zero, improving aerodynamic efficiency due to a greater Oswald efficiency number in the induced drag equation.

The superiority of the pure elliptical shape is only theoretical. Wings with other planforms can be optimized to give the necessary elliptical spanwise lift distribution.[citation needed]

The basic elliptical wing shape also has disadvantages:

  • The uniform lift distribution of a constant-aerofoil section elliptical wing causes the entire span of the wing to stall simultaneously, potentially causing loss of control with little warning. To improve the stalling characteristics and give the pilot some warning, designers use a non-uniform aerofoil. For example the wing of the Supermarine Spitfire was both thinned towards the tips and twisted to give washout, reducing the load on the tips so that the inner wing would stall first.[3][4] Such compromises depart from the theoretical elliptical lift distribution, increasing induced drag. Thus, in practice the elliptical planform seldom achieves the theoretical efficiency of an elliptical lift distribution.
  • Elliptical curves are difficult and costly to manufacture.[citation needed] In practice, most elliptical wings are approximations, for example several sections of the Spitfire leading and trailing edges are arcs of circles.
Here is another way to ruin your day

 

article-1311828-0B2D77C6000005DC-701_964

 

This guy had landing gear Koch and it didn't seem to help much in this case.

They're referring to what sailors call twist. Except in a sailboat you want to keep the bottom flowing and let the top twist open to reduce lift and drag, thus heeling moment. An opposite case from aircraft where stalling is a concern.

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Koch,

 

You don't have wind gradient from the water to the masthead on an airplane so things are a bit different. Good point though. I need to think through the comparison a bit more.

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I have been smitten by Skerry Cruisers. I thought others may been too, and that it would be an interesting topic. I recently added a post to the Swede 55 topic in Sailing Anarchy, and I'll begin with that.

 

Not a Swede 55, but a 22 Square Meter. If a video ever came within inches of making me loose my senses and buy a boat that I wasn't equipped to maintain, this is it. And it only took 1 1/2 minutes.

 

 

Long, lean, close to the water, tiller.

 

 

And then you take a look inside and realise you have to either stick to daysailing or go up in size, as

 

(launch of a SK 95), or

 

(SK 75 sailing), or

 

(SK 75 Bacchant, re-taken from US)

 

and so on.

 

Here you see the inside of Tor's SK55 (from 1917):

From the re-framing in 2011, Cooking!

 

/J

 

 

 

Not a Swede 55, but a 22 Square Meter. If a video ever came within inches of making me loose my senses and buy a boat that I wasn't equipped to maintain, this is it. And it only took 1 1/2 minutes.

 

Long, lean, close to the water, tiller.

 

That's a real beauty, Bull. A jewel of a boat. I can almost feel the tiller from watching it.

 

But it did make me think that varnish might be cited as a co-respondent in divorce proceedings ;)

 

 

FWIW, Amati was supposed to be a mix between a 30 square :wub: and an IMS Mk 1 B) . A picture of Robert Perry's brain :) as a younger man. Mine too....

 

post-906-0-48216700-1481862708_thumb.jpg

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The story I like about the Spitfire wing was the designer was recovering from some medical Bad Shit in the typical upper class British manner - reclining in a chaise lounge bundled in blankets outside, sipping tea. While engaged in this pursuit, for a month or so, he became enamored of the swallows flying overhead, enjoying speed and maneuver. Elliptical wings, more or less. I really hope he was listening to the 'Lark Ascending' too, a lot, but that is asking too much, I fear. I also hope he did not have some of them shot, for closer examination.

 

Now, this was before the Spitfire and the design was for one of the racers of the 30's, but the same planform. Can't remember if it won or not.

 

Both the Spitfire and the Me 109 were designs based on racers, and speed record holders, which is cool, but gruesome, given the ensuing slaughter of men, in the Homeric sense.

Racing seaplanes was big in the 30s. IIRC the Italians were particularly good at it. IDK why seaplanes were preferred over land-based aircraft. I suspect the elliptical wing was developed from that.

Retracting landing gear is complex, heavy and requires thickness. Pontoons were lighter, more aerodynamic, and the bracing allowed for a much thinner wing.
Hmmm...good points. Gut instinct would tell me that fixed gear with skirted wheels would be less drag. Maybe using water to take off and land was softer and smoother than the grass strips at the time, and allowed a lighter frame?

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Friction drag, definitely. But those pontoons were insanely light, and very streamlined. They could also land and take off at high speeds. Longer by a lot- easier on flow? Some studies I've seen touted better balance- wheels were like tripping over drag, pontoons could be controlled lift. And they were longer, so it's like hull speed. In the air.....

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Kim,

 

Do you have pics of your Skerry Cruiser? I would love to hear about your experiences. Did you and SWMBO do any cruising or weekending on her?

 

BC

No cruising or weekending, she was just a daysailer. Great little boat.

41x6 6000#

I sailed her single handed quite often.

post-8115-0-17134300-1481864024_thumb.jpg

post-8115-0-17356800-1481864057_thumb.jpg

post-8115-0-72641100-1481864106_thumb.jpg

post-8115-0-29822600-1481864127_thumb.jpg

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That would be a fine weekender. 2 bunks, portipotti, cooler full of beer and sandwiches, and a jetboil to make morning coffee on. What more do you need?

 

Amati - Baccant was racing on the Great Zlakes the summer I spent up there ('87). Even more gorgeous up close. A real jewel.

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That would be a fine weekender. 2 bunks, portipotti, cooler full of beer and sandwiches, and a jetboil to make morning coffee on. What more do you need?

 

Quite a bit more, actually.

 

That might do for Swiftsure, but it's not enough for anymore than thirty or forty hours.

 

I like electronics.

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That would be a fine weekender. 2 bunks, portipotti, cooler full of beer and sandwiches, and a jetboil to make morning coffee on. What more do you need?

 

 

but it's not enough for anymore than thirty or forty hours.

Yep. A weekend. ...and it would be a lovely weekend.

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