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Joelark81

Deep vs. shallow keel

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A friend of mine recently aquired a one-off 28 foot sailboat which has a shallow, very long chord keel.  The old owner said the boat went fast upwind (possibly due to the fact that it weighs around 4500 lbs.) and tracked well.  It made me wonder if a long chord shallow keel would produce the same lift as a deep skinny foil, keep in mind that I have next to no knowledge of hydrodynamic/ aerodynamics.  Basically what are the pros and cons of the deep skinny keels and shallow long keels and in what ways do they even out in performance.

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No - that's why fast boats have deep, skinny keels.

The only advantage a long, shallow keel has is when there isn't enough water for a deep, skinny keel.

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Sorry #81,  Deep keels increase stability (for the same weight) and significantly increase windward performance.  A shallow keel boat can go just as fast as a deep keel boat but it will be sliding sideways MUCH more so you'll have further to sail.  But if you like to go into cozy little spaces and places, that shallow keel will enable it quite nicely and there'll be no centerboard/daggerboard trunk inside messing up your accommodations.

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2 minutes ago, Veeger said:

Sorry #81,  Deep keels increase stability (for the same weight) and significantly increase windward performance.  A shallow keel boat can go just as fast as a deep keel boat but it will be sliding sideways MUCH more so you'll have further to sail.  But if you like to go into cozy little spaces and places, that shallow keel will enable it quite nicely and there'll be no centerboard/daggerboard trunk inside messing up your accommodations.

So does the chord length even out the lift at all when going upwind?

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   Wide shallow keel does not implicitly mean more leeway*- but it will have much more drag for the same lift.

* if it has a decent shape

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Actually, as Longy says, a long chord/shallow keel (foil/wing) can produce as much lift (esp at slower speeds) as a short chord/deep keel.  The issue is that it will also create more drag, and (for the same amount of ballast), less righting moment or stability...

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12 hours ago, longy said:

   Wide shallow keel does not implicitly mean more leeway*- but it will have much more drag for the same lift.

* if it has a decent shape

It kinda does though, if we are pedantic. A low aspect planform will have a shallower lift coefficient/angle of attack curve. When you get to 5 or 6 true aspect ratio, the lift curve slope approaches that of the 2 dimensional section. On an aspect ratio of 2 or 1 or less, the lift curve slope is maybe 1/2 that - meaning twice the angle of attack to achieve the same lift. Your leeway angle might go from 3 degrees to 6. In addition to more induced drag. The two are connected, it is vortecies and spanwise flow and pressure escape and all that nonsense that changes the lift slope. This is also the reason low aspect foils are more forgiving and stall at larger angles - the crap coming around the end delays flow separation. 

 Of course generally the area of the long shallow keel will be much more than the area of a narrow fin, which changes everything as well. If the long shallow keel has twice the area of the narrow fin, then it may be able to run at the same angle of attack, but now has more profile drag as well as induced drag. 

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F 14 prototypes in flight

Here's a good way to look at it.  All three F-14's are generating the same amount of lift at the same speed.  If you look closely, you'll see horizonal stabs on the one with the wings swept aft shows some aft trim (leading edge down, trailing edge up) as compared to the one with the wings all the way forward, indicating it's flying at a greater angle of attack.  If you could be in the cockpit, you'd also know the one with the wings swept is at a higher throttle setting due to the increase in induced drag.

 

main-qimg-684bfa0e3e18424d5512bdb8ee37fbe4.webp

Here's another great example.  Because the area of the two wings are the same and because they have to be at the same angle of attack, at this speed, due to AOA the wing that is swept forward is creating more lift than the wing that is swept aft, and so to keep them balanced, you can see the spoilers are partially deployed on the forward swept wing...

As Bob says, generally there is no substitute on a sailboat for draft.  Leaving out lifting foils and canting ballast, etc, etc....

 

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14 hours ago, Joelark81 said:

A friend of mine recently aquired a one-off 28 foot sailboat which has a shallow, very long chord keel.  The old owner said the boat went fast upwind (possibly due to the fact that it weighs around 4500 lbs.) and tracked well.  It made me wonder if a long chord shallow keel would produce the same lift as a deep skinny foil, keep in mind that I have next to no knowledge of hydrodynamic/ aerodynamics.  Basically what are the pros and cons of the deep skinny keels and shallow long keels and in what ways do they even out in performance.

Have you ever seen a glider with stubby, long-chord wings?

A long shallow keel is going to perform poorer than a deep narrow one.

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2 minutes ago, RKoch said:

Have you ever seen a glider with stubby, long-chord wings?

 

Maybe?

 

SZ-07Gap-WS-LJA-01-1.jpg

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I sailed 4500 offshore NM on a Joe Byars design combo....traditional  shallow draft full keel ...rudder on skeg.....kicker was a SS dagger board...28' awesome boat on every point of sail in all weather..in all depths....it had a open dagger board trunk in the cabin...great for taking a piss in 

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All things being equal ... greater  draft will deliver greater performance!  It's not by happenstance every handicap rule in the last century,  looks hard at the depth of draft!

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53 minutes ago, RKoch said:

Have you ever seen a glider with stubby, long-chord wings?

A long shallow keel is going to perform poorer than a deep narrow one.

Fair point, I haven’t thought about it that way before.

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1 hour ago, RKoch said:

Have you ever seen a glider with stubby, long-chord wings?

A long shallow keel is going to perform poorer than a deep narrow one.

Yep!

Rgalo18a.jpg

 

Waco CG-4A USAF.JPG

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In this house, we OBEY the laws of physics! [Homer Simpson]  Long and skinny maximizes lift and minimizes drag.  Glide ratio is quite similar to leeway.

How many of those Rogalo wings are still around? (they weren't very stable)  Nowadays hang gliders look more like this:

saturn-planform-flying-746x402.jpg

Or this;

images?q=tbn:ANd9GcREyGqlKWSmBUcBulMgbKy

 

That WWII glider still has a higher aspect ratio than most 'fin' keels.  Even in 1944, they knew a thing or two. 

 

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Sure, but compare that Waco Glider to this B-24.  It all depends on the requirement you're building the foil (wing) to meet.  For the Glider, which was going to land in fields and meadows and where you wanted to put alot of them into that one field, shorter wingspan, longer chord was the answer.  For the B-24, which was only going to launch or recover from a hard surface runway, and fly at high altitude, then longer wingspan, skinnier chord was the answer...

1024px-Consolidated_B-24_Liberator_from_above.jpg

I'm not trying to argue that long, skinny wings or deep, short chord foils aren't more "efficent" than short stubby ones.  The OP asked if they could produce the same amount of lift.  The answer is yes.  But at a cost of higher drag, thereby costing some performance.  Given no depth restrictions, there is no substitute for draft.  When there are draft restrictions, well, that's where different shoal keel answers come in (or centerboards, or wings or etc).  But to answer the basic question asked, a shallow, long chord keel could produce the same lift as a deeper, shorter chord keel.

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I'll see your B-24 and raise you a B-17!

Image result for b 17

   I knew a guy who lied about his age towards the end of WW2 and they didn't discover he was still just a kid until they had put him through flight school. I guess they figured the could use him anyway but had him deliver B-17's to England until he reached the legal age. They had women doing the ferry flights too, and when they got there with the planes it was often a week or two before they could catch an empty troop ship back to the US to get another bird. 

   Someone figured that they could use the ferry crews to do the break-in flights after a new engine was was fitted. It was necessary to give the new engine a good run-in so they would take off with it at and idle and then slowly climb while monitoring oil pressure and exhaust manifold temp on the green engine. They would carefully increase RPM's according to a strict protocol and it would take all day and my buddy said it was even more boring than the long delivery flights. At least you got to land at a new field on those at the end of the day. They would take a paperback and put the plane on autopilot and take her right up to service ceiling and keep her there on a big 'race track' course until the engineer gave them the thumbs up on the newly broken it engine. Charlie said on one flight that they had a couple of extra hours since they had left at the crack of dawn and it was a fine sunny CAVU sort of day and he asked the other guys if they had ever wondered just how high a b-17 could really fly. Everybody was in on his experiment and they took the big bird on up and went well above the published ceiling rating. 

    Once they got there, he posed the question of how far could a B-17 glide from that altitude and they shut down all four engines festhered the props and played around with airspeed until they found the best glide slope. He said that big wing with a low loading with little fuel and no bombs on board was just like a glider and they milked it for all it was worth. It took so long to lose most of that altitude that it attracted the attention of the tower and the CO and he asked what the hell were they doing and get back to the field. It was starting to get on towards dark and when they tried to pitch the inboard props to help start the motors they found that the cold from altitude had congealed the hydraulic fluid in the props and they couldn't get the extra 'push start' from the props to help the electric starter motors turn the frozen engines. The oil was pretty stiff to and with only 10,000 feet of altitude left, the situation was getting pretty stupid. Only hope was to send a guy most of the way to the tail to a single cylinder gas genset with a pull cord starter to get some more juice in the fading batteries. It was cold on the flight deck but nobody wanted to go to the drafty tail and wrestle with the equally frozen one lunger but they drew straws and barely got the genset going in time to start the engines. 

    The CO was waiting for them on the ground and gave them a royal chewing out on the spot and confined them to quarters while they decided on what sort of disiplinary action should be taken. The engineer drafted up a full report on the performance at the extra altitude and computer the gliding range they had determined on their unauthorized experiment and handed it to the disiplinary board when the were called on the action. They got some minor extra KP duty or some such and shipped out back to the states a couple of days later.

    The funny thing about this whole affair is that when they returned to that base on their next ferry trip they were given commendations for the through report of the planes high altitude gliding performance and they were credited with helping damaged bombers to make it back across the North Sea instead of the hazardous ditching and rescue at sea.

That B-24 wing has less taper and looks to have a higher aspect ratio, wonder what their max altitude was?

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7 minutes ago, Rasputin22 said:

I'll see your B-24 and raise you a B-17!

Image result for b 17

   I knew a guy who lied about his age towards the end of WW2 and they didn't discover he was still just a kid until they had put him through flight school. I guess they figured the could use him anyway but had him deliver B-17's to England until he reached the legal age. They had women doing the ferry flights too, and when they got there with the planes it was often a week or two before they could catch an empty troop ship back to the US to get another bird. 

   Someone figured that they could use the ferry crews to do the break-in flights after a new engine was was fitted. It was necessary to give the new engine a good run-in so they would take off with it at and idle and then slowly climb while monitoring oil pressure and exhaust manifold temp on the green engine. They would carefully increase RPM's according to a strict protocol and it would take all day and my buddy said it was even more boring than the long delivery flights. At least you got to land at a new field on those at the end of the day. They would take a paperback and put the plane on autopilot and take her right up to service ceiling and keep her there on a big 'race track' course until the engineer gave them the thumbs up on the newly broken it engine. Charlie said on one flight that they had a couple of extra hours since they had left at the crack of dawn and it was a fine sunny CAVU sort of day and he asked the other guys if they had ever wondered just how high a b-17 could really fly. Everybody was in on his experiment and they took the big bird on up and went well above the published ceiling rating. 

    Once they got there, he posed the question of how far could a B-17 glide from that altitude and they shut down all four engines festhered the props and played around with airspeed until they found the best glide slope. He said that big wing with a low loading with little fuel and no bombs on board was just like a glider and they milked it for all it was worth. It took so long to lose most of that altitude that it attracted the attention of the tower and the CO and he asked what the hell were they doing and get back to the field. It was starting to get on towards dark and when they tried to pitch the inboard props to help start the motors they found that the cold from altitude had congealed the hydraulic fluid in the props and they couldn't get the extra 'push start' from the props to help the electric starter motors turn the frozen engines. The oil was pretty stiff to and with only 10,000 feet of altitude left, the situation was getting pretty stupid. Only hope was to send a guy most of the way to the tail to a single cylinder gas genset with a pull cord starter to get some more juice in the fading batteries. It was cold on the flight deck but nobody wanted to go to the drafty tail and wrestle with the equally frozen one lunger but they drew straws and barely got the genset going in time to start the engines. 

    The CO was waiting for them on the ground and gave them a royal chewing out on the spot and confined them to quarters while they decided on what sort of disiplinary action should be taken. The engineer drafted up a full report on the performance at the extra altitude and computer the gliding range they had determined on their unauthorized experiment and handed it to the disiplinary board when the were called on the action. They got some minor extra KP duty or some such and shipped out back to the states a couple of days later.

    The funny thing about this whole affair is that when they returned to that base on their next ferry trip they were given commendations for the through report of the planes high altitude gliding performance and they were credited with helping damaged bombers to make it back across the North Sea instead of the hazardous ditching and rescue at sea.

That B-24 wing has less taper and looks to have a higher aspect ratio, wonder what their max altitude was?

thanks for sharing that story.....

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Currently class racing gliders have true aspect ratios of around 30 or 35:1. Open class gliders somewhat more. The glide ratios are in the high 50s and low 60s. That is equivalent to a pointing angle of 1 degree apparent. There is a project in Germany attempting to exceed 100:1 glide ratio. 

At high altitude there are some additional problems: the air is thin enough you have to fly at high true air speeds to get the same lift. The true airspeed for wing flutter goes up as well, but not as fast. Those two lines cross somewhere. The U2 in its final form was supposed to have only a 7 knot range between stall and flutter when at altitude. The Perlan project is attempting to reach 100,000 ft in a sailplane. So far they hold the world record at a little over 10 miles high. Lots to think about in that design, including how composites hold up at some seriously low temps. 

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Thanks Sail,

     The really sad thing is that Charlie told me that story at a Mardi Gras party at his house about 5 years ago and with us was an English gent who had been in the Merchant Marines during that same era. I think he might have been a bit older and had worked as a mariner his whole life. I felt so lucky to be with them swapping sea stories with them and I later told my GF that I should go back with a video camera and get the B-17 story archived. I was active in a soaring club at the time and a student with maybe 50 hours and came up with the idea of having Charlie and the Capt to come out to the club on Veterans Day and treat them to a dual glider flight with one of the Old Eagles who made up the majority of our club membership. The club was in Pensacola (lots of retired aviators) and we had some old birds nearly as old as the WW2 vets still flying and the club was totally behind honoring these two in such an appropriate manner. 

    I made the invitation to Charlie and he told point blank that he would never set foot in a sailplane! I still should have just gotten him to retell the story in his own home and if I had the fine video capabilites that the Iphone provides today I could have recorded it in a very unobtrusive manner. By the same token, I should have done the same with my own Father who was a US Navy Captain after 27 years of service and who I lost just this summer. I was raised on his 'sea stories'.

 

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Good read

 

Wing Design—Which Model Has the Edge?

There is only one part of an airplane—any airplane—that is absolutely necessary for flight and that is the wing. This is one area in which the B-17 possessed something of an advantage over the B-24. The aerodynamics of the Flying Fortress stemmed from designs of the late 1920s and early 1930s, featuring a wide chord, the width of the wing from leading to trailing edge, and shorter span. The British slang “kite” is appropriate for the B-17, because the huge wing provided tremendous lift that did make for a stable bombing platform and, at least in the minds of B-17 fans, provided increased lift that was valuable in the event of a power loss on an engine. The B-24, on the other hand, incorporated a brand-new wing design that was on the very cutting edge of aviation technology in 1937. The long, narrow Davis Wing was what is known as a “high aspect ratio” wing, meaning that the span is proportionally much greater than the chord, a feature that provides significantly reduced drag and increased performance on heavier airplanes—which is why the B-24 was considerably faster than the B-17.

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In 'splaining all this to the OP aren't we leaving out a discussion of camber, section and area as it relates to foil performance? It seems to me everything that's been said about aspect ratios ought to have the caveats "foil section and lifting surfaces being the same".........

Also, keeping D/L ratios and L/D coefficients in the competitive range for performance boats pretty well supersedes considerations of tracking stability and comfortable motion in seaways which rightfully are of increased concern to cruisers. He should bear in mind that one design doesn't fit all sailors and try to find which tradeoffs work for him. 

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Perhaps friend Bob can enlighten us as to how or why a symmetrical keel creates lift..

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3 minutes ago, poncho said:

Perhaps friend Bob can enlighten us as to how or why a symmetrical keel creates lift..

hence...Terrorist....asymmetrical dagger boards....symmetrical keels are compromised foils

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2 hours ago, Bob Perry said:

Make a list of today's high performance sailboats that have low aspect ratio appendages.

It's going to be a very short list.

None that I can think of Bob, but doesn't that go back to the requirements piece...someone who wants a high performance sailboat is typically willing to be "not draft constrained"

Funny part is make a list of high performance aircraft like the F-22, F-15, F-18, Swedish Grippen, etc.  All of them have low aspect ratio wings...because the requirement is high sustained "G" capability and high roll rate.  Any you can't get that with big long wings...

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  They have motors - bigly, huuuge motors. Drag is not much of a hindrance when you've got enuff power to go straight up.

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My understanding is that high aspect foils are more efficient in terms of lift vs. drag but are also easier to stall.  Everything is a compromise in some way.

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Foils that are designed for supersonic speeds answer to a completely different set of rules, it has nothing to do with aspect ratio but rather angle of attack.

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Supersonic or near sonic aircraft have shock wave considerations to deal with too. When the fluid become compressible, a lot of things change. In low speed aerodynamics and certainly in boats, the fluid is considered to be incompressible. Even airliners have swept back wings, as they fly at high Mach numbers (.5 and above). You will never see a modern sailplane with a swept back wing. You really shouldn't see it on boats either, but for kelp and fishing tackle. 

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Shock wave, that’s the word I was looking for. Thank you I won’t have to go look for that fluid dynamic school book.

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44 minutes ago, PJ_Tabarly said:

Foils that are designed for supersonic speeds answer to a completely different set of rules, it has nothing to do with aspect ratio but rather angle of attack.

That's very true.  But Fighters have slow speed maneuvering requirements as well.  We might come into a merge at 450kts, and end up in a slow speed rolling scissors fight at 125-175kts.  Of course, a slow speed scissors is a good way to die in today's high off boresight missile environment, so that requirement may be going away.  But Navy fighters have to be able to have good slow speed handling to come back aboard the boat as well...

Every requirement is different, and requires a different set of compromises...

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regarding the supposed course stability of long keels....designer Michel Joubert used to explain that they dont have more course stability... it's just that they are slower, hence take longer to deviate....

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4 hours ago, Crash said:

That's very true.  But Fighters have slow speed maneuvering requirements as well. 

There's nothing wrong with low aspect ratio and sweep back for low speed maneuvering. In fact it's great for that as you can operate at very high angles of attack without a classic stall. The "lift strakes" on some fighters are there for that reason. In sailing, Marchaj went into that in some detail on his often (wrongly) maligned study of the crab claw rig. It gives you high lift at high angles of attack. It does not give you low drag - but drag isn't very consequential to a fighter with that kind of thrust. 

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Really?  Then why are the wings on a Pitts Special or Extra 300 short?  Or an A-4 Skyhawk?  None of those are supersonic aircraft.  Short wings also improve roll rate.  On an aircraft carrier, short wings let you park more aircraft in a given space without needing a wingfold system (which adds unwanted weight).  Point design aircraft that are just meant to go supersonic end up with wings looking like a Concorde's or the Space Shuttles.

DDW is right, and today most fighters have excess power and flight control systems that let them operate at extreme angles of attack.  But drag is also an issue for fighters, as they need range to get to a target,  intercept threat aircraft outside of weapons employment range, etc.  So those foils at typically pretty thin as well to enable  a (relatively) low drag, high altitude max range profile as well...and use relatively large control surfaces/high lift devices (flaps/slats, etc) to generate low speed lift.  But they are also relatively long of chord to provide fuel storage and load carrying capability (weapons, extra fuel tanks, etc)...

The Warthog's roll rate is not all that special, but its load carriage is, as well as its ability to sustain damage from ground fire.  Hence (for a modern attack aircraft) it has big thick straight wings...but it pays a penalty in that it's no faster then a WWII fighter.  So it can only operate in an environment in which we have air superiority...

Again, it all comes down to what set of requirements are you trying to meet?  I would argue that like a Concorde, or a 737, or a modern glider, which are "point" designs, a high performance, racing sailboat is also a point design.  And so its foil shape can be optimized to only have to meet a relatively small set of requirements, which allows a deep draft, short chord, skinny foil design.  It doesn't have to be highly maneuverable (operates mostly going in a straight line, it doesn't have to operate at extreme AOA, it doesn't need to provide volume for tankage, etc. 

 

 

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The problem with high aspect ratio is that it requires speed to work. No matter is the subject a glider wing, keel fin or a rudder. Of course, it depends a lot of profile but generally a glider with high aspect ratio tend to have higher stall speed than average. Glider with lower aspect ratio wings can fly sower and draw tighter circles that might be beneficial in narrow thermals. Same time the glider with higher aspect ratio has higher lift to drag ratio (polar) and will loose less while flying from thermal to thermal with higher speeds. Pretty much the same thing applies to sailboats. If you have racer then you need to have thin high aspect ratio keel (and rudder) to reduce drag in higher speeds but this does not mean that it is good in weak weather. And if you have a heavy cruiser that is not able to plan then a thin keel will not help, a long keel with low aspect ration might work better.

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15 minutes ago, pilot said:

The problem with high aspect ratio is that it requires speed to work. No matter is the subject a glider wing, keel fin or a rudder. Of course, it depends a lot of profile but generally a glider with high aspect ratio tend to have higher stall speed than average. Glider with lower aspect ratio wings can fly sower and draw tighter circles that might be beneficial in narrow thermals. 

This is incorrect. High aspect ratio reduces induced drag at any speed. It does not affect stall speed except as I pointed out above (in that very low aspect ratio planforms delay stall). There are no gliders with aspect ratios that low except for Rogallo hang gliders. In practice, gliders with high aspect ratio wings are intended for high performance use, and usually will have a greater wing loading, which will increase stall speed. But this has nothing to do with aspect ratio. A trainer for example will have a wing loading of 7 lbs/ft^2, while a racing glider filled with water for strong conditions will be at 13 lbs/ft^2. There are racing gliders that can fly in both conditions as they have tankage for 500 lbs or more of water ballast. The stall speed will go up by 36% in the ballasted condition. 

Circling in thermals, a glider with less wingspan can circle a little tighter than one with a large wingspan, as the inside wing slows down more on the large span, increasing its angle of attack. The difference in practical gliders is very small. Again aspect ratio has nothing to do with it. Much larger is the difference (again) in wing loading - with light wing loading your stall speed is less, and you can circle tighter at the slower speed.

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Poncho:

Simple. Angle of attack. I am very surprised that you don't know that by now. In a perfect world we would have asym foils, one for each tack. But you most certainly know this.

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Although there are many analogies between keelboats and low Mach number wings, they are quite different. Wings need to always provide lift enough to keep the plane from dropping down. That is lift=weight. This means that slower speed equals to higher loading and AoA. Dropping speed too much results to stall.

Sailboats are more complex. They have also sails and they work in the air water interface, not in just one fluid. Lift provided by keel (and rudder + hull) changes very much depending on wind speed, wind angle sailed and sail trimming.

So for sailboats there is no specific stall speed. It depends on the lift neeed, which is equal to side force generated by the sails (and hull over water). Typical keel would stall only at a very extreme situations, in which forces are not in balance or speed is much below normal point of sailing. Accelerating using high sideforce from sails with low speed would be the most common case.

Note that stall is not at all as catastrofic for a sailboat as it is for a plane. When a wing/keel/rudder stalls it's lift is reduced, but not at all removed. At the same time drag increases. For a plane this is deadly combination, since lift needed must be equal to weight and drag due to stalled wings is very high portion of the total drag, which makes it very difficult to get back to the state before stalling.

A stalling keel means just more leeway and the need for reducing sideforce from sails. The added drag due to stalling keel is usually a very minor portion of the total hydrodynamic drag and thus does not make much of a difference on the forward force needed from sails to keep the speed constant. The leeway is huge before stalling and more of a problem than stalling itself.

A stalling rudder leads often to broach due to reduced lift or maybe it's better to say that the boat broaches when load on the rudder is higher than its maximum lift at that speed.

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32 minutes ago, Joakim said:

Although there are many analogies between keelboats and low Mach number wings, they are quite different. Wings need to always provide lift enough to keep the plane from dropping down. That is lift=weight. This means that slower speed equals to higher loading and AoA. Dropping speed too much results to stall.

Sailboats are more complex. They have also sails and they work in the air water interface, not in just one fluid. Lift provided by keel (and rudder + hull) changes very much depending on wind speed, wind angle sailed and sail trimming.

So for sailboats there is no specific stall speed. It depends on the lift neeed, which is equal to side force generated by the sails (and hull over water). Typical keel would stall only at a very extreme situations, in which forces are not in balance or speed is much below normal point of sailing. Accelerating using high sideforce from sails with low speed would be the most common case.

Note that stall is not at all as catastrofic for a sailboat as it is for a plane. When a wing/keel/rudder stalls it's lift is reduced, but not at all removed. At the same time drag increases. For a plane this is deadly combination, since lift needed must be equal to weight and drag due to stalled wings is very high portion of the total drag, which makes it very difficult to get back to the state before stalling.

A stalling keel means just more leeway and the need for reducing sideforce from sails. The added drag due to stalling keel is usually a very minor portion of the total hydrodynamic drag and thus does not make much of a difference on the forward force needed from sails to keep the speed constant. The leeway is huge before stalling and more of a problem than stalling itself.

A stalling rudder leads often to broach due to reduced lift or maybe it's better to say that the boat broaches when load on the rudder is higher than its maximum lift at that speed.

 

IMG_0002.jpg

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Then again you can both situations with a long keel & centerboard... the board provides good lift at speed, and the long keel provides angular stability and low speed lift, when the board might be stalled. The combination does have a crapload of surface area and resulting drag... 

 

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1 hour ago, Joakim said:

So for sailboats there is no specific stall speed.

It is a common misconception that a stall is caused by lack of speed. Any airfoil stalls at a certain critical angle of attack, regardless of speed.* In an aircraft, there may be a loose relationship between angle of attack and speed in typical operation. But the wing can be stalled at very high speed (that is how a snap roll is performed), or be unstalled at very low speed (in a pushover). The same is true of sailboat rigs, keels, and rudders. You should think angle of attack, not speed.

Other than that your post is right on. 

* There is a secondary effect due to Reynolds number - at very low Reynolds numbers, the critical angle will change a bit depending on section. 

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22 hours ago, Crash said:

None that I can think of Bob, but doesn't that go back to the requirements piece...someone who wants a high performance sailboat is typically willing to be "not draft constrained"

Funny part is make a list of high performance aircraft like the F-22, F-15, F-18, Swedish Grippen, etc.  All of them have low aspect ratio wings...because the requirement is high sustained "G" capability and high roll rate.  Any you can't get that with big long wings...

Crash, you're  right about many things in your post but not this one. Sustained G can be achieved in a couple of ways. One is to push it through the air with excess thrust (which current, 4 & 5G fighters have in ridiculous abundance). Another ( and the only other one I can think of) is to decrease induced drag at high AOA. High aspect ratio foils/wings do that. There are other techniques (endplates, and stall fences for example) but they all relate to the tendency for spanwise airflow to develop at the boundary between high pressure (lifting) and low pressure surfaces-which generate those tip vortices we hear so much about. Short, stubby, delta or swept wing planforms are particularly conducive to induced drag, spanwise flow and tip vortices so they don't, in and of themselves, contribute to sustained high G-quite the contrary. 

Anyway, all of this has probably caused the OP's eyes to glaze over and swear off Sailing Anarchy. Joelark, by any chance have we given you an answer to your question that helps you decide? 

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I like to think of my keel being a wing and although symmetrical has a slight angle Windward thus generating lift towards the wind and helping me progress in the wind. It is a tapered Peterson fin with a nice profile, thick one third aft with rounded leading edge and thin trailing  Edge. I can hardly imagine the airfoil shape of a full keel, too wide chord for the thickness so it acts mostly like a plate to keep the boat from drifting sideways.  

There are so many parameters influencing the design of wings that taking one feature (aspect ratio) without  consideration for the other factors is an incomplete exercise. One of those important factor being the evolution in materials and engineering that has allowed higher aspect ratio foils to sustain the stresses that only short and wide foils could endure when built of wood or riveted aluminum.

wingdes.pdf

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3 hours ago, kinardly said:

Crash, you're  right about many things in your post but not this one. Sustained G can be achieved in a couple of ways. One is to push it through the air with excess thrust (which current, 4 & 5G fighters have in ridiculous abundance). Another ( and the only other one I can think of) is to decrease induced drag at high AOA. High aspect ratio foils/wings do that. There are other techniques (endplates, and stall fences for example) but they all relate to the tendency for spanwise airflow to develop at the boundary between high pressure (lifting) and low pressure surfaces-which generate those tip vortices we hear so much about. Short, stubby, delta or swept wing planforms are particularly conducive to induced drag, spanwise flow and tip vortices so they don't, in and of themselves, contribute to sustained high G-quite the contrary. 

Anyway, all of this has probably caused the OP's eyes to glaze over and swear off Sailing Anarchy. Joelark, by any chance have we given you an answer to your question that helps you decide? 

Honestly everything said so far has been pretty helpful, considering that it won’t be worth it to fit a new keel to the boat I think we’re just going to see how it performs in races and go from there, I just wanted a general idea of what to expect

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40 minutes ago, Joelark81 said:

Honestly everything said so far has been pretty helpful, considering that it won’t be worth it to fit a new keel to the boat I think we’re just going to see how it performs in races and go from there, I just wanted a general idea of what to expect

You run what you brung. Now it's up to you.

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3 hours ago, kinardly said:

Crash, you're  right about many things in your post but not this one. Sustained G can be achieved in a couple of ways. One is to push it through the air with excess thrust (which current, 4 & 5G fighters have in ridiculous abundance). Another ( and the only other one I can think of) is to decrease induced drag at high AOA. High aspect ratio foils/wings do that. There are other techniques (endplates, and stall fences for example) but they all relate to the tendency for spanwise airflow to develop at the boundary between high pressure (lifting) and low pressure surfaces-which generate those tip vortices we hear so much about. Short, stubby, delta or swept wing planforms are particularly conducive to induced drag, spanwise flow and tip vortices so they don't, in and of themselves, contribute to sustained high G-quite the contrary. 

Anyway, all of this has probably caused the OP's eyes to glaze over and swear off Sailing Anarchy. Joelark, by any chance have we given you an answer to your question that helps you decide? 

Kinardly, 

Your right, esp. from a purely aero standpoint.  That said, I can't think of (off the top of my head anyway) of an aircraft that can sustain 6-9 Gs with a high aspect ratio foil/wing.  I'd love to know of one, just cause that'd be cool...But that's really a structural challenge, and its the structural issues that make building a low aspect ratio - shorter, wider - wing much easier do. Plus that low aspect ratio wing will have (generally) a higher roll rate, which is another good trait for fighters.  As an example, the F-14 with its wings out could roll at about 180 degrees/sec.  An A-4, with it's little short stubby delta wing could roll at a rate of 720 degrees/second.   But you're also right that we have likely gone way too far down this rabbit hole, and are providing little value to the OP at this point...

Crash

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11 hours ago, DDW said:

It is a common misconception that a stall is caused by lack of speed. Any airfoil stalls at a certain critical angle of attack, regardless of speed.* In an aircraft, there may be a loose relationship between angle of attack and speed in typical operation. But the wing can be stalled at very high speed (that is how a snap roll is performed), or be unstalled at very low speed (in a pushover).

I wouldn't call the relationship between AoA and speed loose in an aircraft (with fixed wing area and profile). In normal flight operation lift is always equal (or very close) to weight and at the same AoA lift increases by rho*V^2. So at a given altitude (constant rho) there is a fixed minimum flight speed, which comes from maximum AoA dictated by stall.

Yes you can have very different lift in special cases and thus break the normal relationship between speed and AoA. E.g. having wheel on the ground the lift can be anything from zero to weight. And by introducing vertical acceleration you can increase or decrease lift. But while flying you can't have long term vertical accelaration unless you are flying a loop.

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Aircraft certainly can have long term vertical acceleration (from the aircraft's frame of reference). In a 60 degree bank turn the lift required is increased by  100%, and that condition can be maintained indefinitely - even in a glider. This will increase stall speed by 41% - not a small amount. The AoA for stall will be exactly the same though. You mention Rho which also greatly affects stall speed - but not stall AoA. At 18,000 ft Rho is approximately 1/2, again increasing stall speed by 41% - but again stall AoA is unaffected. This is why commercial jetliners are flown by AoA indicators as much as airspeed, and almost exclusively when operating close to stall. In an aircraft, thinking only about airspeed has killed many pilots and passengers. The Air France crash in the South Atlantic comes to mind - flown in a high speed full power stall from 35,000 ft right into the water, because the high AoA was not noticed by all three pilots. An incipient spin or stall is immediately mitigated by simply pushing the stick forward, lowering the AoA and unstalling the wing - long before any additional airspeed is gained. Yes your lift is reduced and you are now accelerating towards the ground, but you can deal with that later, after you have regained control.

Returning to boats, it isn't normal to stall the keel unnoticed, since the leeway angle will be extreme. On the rudder though, attention to AoA is important. In a sharp turn (like a tack) the local flow around the rudder is very different than that around the keel - and boat speed has nothing to do with the angle of attack at stall. If the rudder is stalled, the immediate solution is not more speed - it is less rudder angle.

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12 hours ago, Crash said:

Kinardly, 

Your right, esp. from a purely aero standpoint.  That said, I can't think of (off the top of my head anyway) of an aircraft that can sustain 6-9 Gs with a high aspect ratio foil/wing.  I'd love to know of one, just cause that'd be cool...But that's really a structural challenge, and its the structural issues that make building a low aspect ratio - shorter, wider - wing much easier do. Plus that low aspect ratio wing will have (generally) a higher roll rate, which is another good trait for fighters.  As an example, the F-14 with its wings out could roll at about 180 degrees/sec.  An A-4, with it's little short stubby delta wing could roll at a rate of 720 degrees/second.   But you're also right that we have likely gone way too far down this rabbit hole, and are providing little value to the OP at this point...

Crash

Crash,

    These are the basic specs for a Polish aerobatic sailplane called the Fox MDM-1.  Does nearly 16:1 aspect ratio work for you at +9G -7G? Glide ratio is still 28:1, not too shabby.

General characteristics

  • Crew: Two
  • Length: 7.38 m (24.22 ft in)
  • Wingspan: 14.00 m (45.93 ft in)
  • Wing area: 12.3 m2 (132.4 ft2)
  • Aspect ratio: 15.9
  • Empty weight: 345 kg (761 lb)
  • Gross weight: 525 kg (1,157 lb)

Performance

  • Maximum speed: 281 km/h (175 mph)
  • Stall speed: 84 km/h (53 mph)
  • G limits: +9.0/-6.0 (one occupant), +7.0/-5.0 (two occupants)
  • Maximum glide ratio: 28
  • Rate of sink: 1 m/s (200 ft/min)

Image result for MDM-1 Fox

How is this for some negative B? Outside loop anyone?

 

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Next time you are in California, you can take a ride (or a lesson) with Luca in a Fox up at the Williams gliderport. He will ask you "are your seat belts tight?" and you might say yes. Then he will say "Can you still breath?" and you might say yes. Then he will say "Then they aren't tight enough...."

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The fighter Luke Skywalker would choose. Careful with the landing.

Lockheed_XF-104_(modified).jpg

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3 minutes ago, Grey Dawn said:

The fighter Luke Skywalker would choose. Careful with the landing.

Lockheed_XF-104_(modified).jpg

104 Star Fighter.... built all the Revell models back in the day....saw one at an airshow in Titusville ,Fl a few years ago

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DDW,

     I ran across a promo video for the WIlliams Fox tours. I'll definitely do that if I get to that area. Here is a link to the new World Acro Soaring champ which show a real contrast to the edgy Red Bull style of the Italian. The new kid on the block is Swedish and even the editing and music of the video show a smoother more flowing attitude. That outside loop to a hammerhead stall looks like a real stomach turner!

     In his interview he mentions having come from the ultralight background and mentions wanting to get a SWIFT in order to have a go at the Ultralight Aero title. I had to look that one up and was surprised at the load ratings and glide ration for such a minimal craft.

image.png.578aaed51c27e4aa8b44809a3ce24ba0.png

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Lars Bergstrom co inventor of the Windex mast head fly and proponent of many of the sail , keel and rudder designs seen on today's Volvo boats  spoke fondly of the Windex Plane....sadly he died in a flat spin crash thought to have been caused by carbon monoxide poisioning

 

Windex.jpg

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A boat with a shoal keel may be a big handicap when the boat heels. My father's Columbia 23 would slide to leeward by the yard when heeling in a gust. 

 

 

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Hard to think that with that engine mounted so far aft that CO could get drawn into the pilot compartment. But when you consider how air tends to move towards the bow in a boat I can guess it is possible. A shame to lose Lars that way. 

RIP

http://www.nytimes.com/1997/03/09/sports/lars-bergstrom-boat-and-plane-innovator-62.html

That Windex is pretty sweet!

SUE-inAfQDioWw58yrvQ8SFIHsj_70usb-OrCBw2MvmJtR9VcjF5A1rdajkUQQIlsvIXYivIEGToG7TME-u-_vz5L0D3BQAOnLTpE8SNMb5YaU7GUZoMEDfbr0MkD7HhJNk62AxoVnzXs8_W1dWyrdkSsOIbR5UVcHo8vcbPOib9gQ9rqjrTWNGdDHlalDB96EdTtWlBDIcOWl2X1i5Z9U8AtjnyG-B_Wl6MQFc6JNrFAcilD60CGQC_pwXMjtoWvd8CNNDJpF5xPGkbbsOJXi9pR0Or2O8YfNuDlVnEJte7Ui6X_ksUljyvFaKcqXp5EKJol5LO68OjAslAvt3BGkwp951pgkxwBTVtvjrsyvXkBdJLTu2fsZtY7mNwza0XSPKVCemdnOeqLYodawl9K06u9sPbsEqBoeJ5Mszq08QkNa_EMx6vjpfPgBPsa26oht64cj8X6xOMhjSv0txSZy4p8aVwHyaEAGMi98VFy73842tQny2UZP09l7rHxkmrQ47BCA9S2-jJZTM5iByqSN2n-eV2XwZHcQUgYYc-i7mNVMnjuEdUjf3g78zlMa4JOXRRPtMt-zTH5qIarrY4yVRZWmu_59j64hDxDVt3fydeQyPWT0GxoLem98oUiFatejrS623WMMRVCUWUf_m16e5PJXZljOeQ_wtp=w1190-h892-no

It is even rated +9G -7G as well. 36:1 glide ratio on only 12m span! I want one!

6GPwrdRqSH4BeB3xWrc0jj7C0KtfLIdKRQxXyTDbiEav3MJuzFJbOvHyDJjm-ACv_QQ2XGvqVRQ6t0mzjj2tv8Md9vB1DKwkmqCp6otXwld_dBbZBTWDwpPiS2qw56b1utj0x9USHiiTF8SvWRzWt_gn7Xf_HQ8doAnZwnlwYpIYG3et1xEREwv3AeWyPKiE6Tm2qS0I1hlb6k3iGt6WY8ARJUIp5PHukiRymyFOEBVDoxunEyTWmZsYLD67gLK4N5CYly2EJR8DcoU2_VECo9xU32ko-TsQ9jYl-EZYN5oOmgMSYyO_9mfPGWYLzHHPENXdhYUtVcr-2kgu4_BTR8riw_dzxNaxuYLvV1NmxLAZte0PCFrf0YmiDUV1YgDFz_6Ne2v5WEWeH2-Nws6pHcAyenlORtznetdIucHx__rsvMOuZy7o_1PUPjB-z09uGmTiVNrzKI4ypkZFePwq6QArzC6FYw-xxe8hPnTGlWfH2r2IhDiE3L53CNrVPKhMXL-d6BYbRMsbBZ42mow_FeSU-WGdsXua85sop6VFU_aAkSqYyycn0tc86CLXLjkNzpkk84MRY7t8PwbIHlqSRs3DvqO51eCndMPdMWwN86YIfP04u1V5C9-2_ydCaEfHf1enPp6yKGDf-4gRmgtm2L0g19lDKFxNKH_o=w669-h892-no

 

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13 minutes ago, Rasputin22 said:

Hard to think that with that engine mounted so far aft that CO could get drawn into the pilot compartment. But when you consider how air tends to move towards the bow in a boat I can guess it is possible. A shame to lose Lars that way. 

RIP

http://www.nytimes.com/1997/03/09/sports/lars-bergstrom-boat-and-plane-innovator-62.html

That Windex is pretty sweet!

SUE-inAfQDioWw58yrvQ8SFIHsj_70usb-OrCBw2MvmJtR9VcjF5A1rdajkUQQIlsvIXYivIEGToG7TME-u-_vz5L0D3BQAOnLTpE8SNMb5YaU7GUZoMEDfbr0MkD7HhJNk62AxoVnzXs8_W1dWyrdkSsOIbR5UVcHo8vcbPOib9gQ9rqjrTWNGdDHlalDB96EdTtWlBDIcOWl2X1i5Z9U8AtjnyG-B_Wl6MQFc6JNrFAcilD60CGQC_pwXMjtoWvd8CNNDJpF5xPGkbbsOJXi9pR0Or2O8YfNuDlVnEJte7Ui6X_ksUljyvFaKcqXp5EKJol5LO68OjAslAvt3BGkwp951pgkxwBTVtvjrsyvXkBdJLTu2fsZtY7mNwza0XSPKVCemdnOeqLYodawl9K06u9sPbsEqBoeJ5Mszq08QkNa_EMx6vjpfPgBPsa26oht64cj8X6xOMhjSv0txSZy4p8aVwHyaEAGMi98VFy73842tQny2UZP09l7rHxkmrQ47BCA9S2-jJZTM5iByqSN2n-eV2XwZHcQUgYYc-i7mNVMnjuEdUjf3g78zlMa4JOXRRPtMt-zTH5qIarrY4yVRZWmu_59j64hDxDVt3fydeQyPWT0GxoLem98oUiFatejrS623WMMRVCUWUf_m16e5PJXZljOeQ_wtp=w1190-h892-no

It is even rated +9G -7G as well. 36:1 glide ratio on only 12m span! I want one!

6GPwrdRqSH4BeB3xWrc0jj7C0KtfLIdKRQxXyTDbiEav3MJuzFJbOvHyDJjm-ACv_QQ2XGvqVRQ6t0mzjj2tv8Md9vB1DKwkmqCp6otXwld_dBbZBTWDwpPiS2qw56b1utj0x9USHiiTF8SvWRzWt_gn7Xf_HQ8doAnZwnlwYpIYG3et1xEREwv3AeWyPKiE6Tm2qS0I1hlb6k3iGt6WY8ARJUIp5PHukiRymyFOEBVDoxunEyTWmZsYLD67gLK4N5CYly2EJR8DcoU2_VECo9xU32ko-TsQ9jYl-EZYN5oOmgMSYyO_9mfPGWYLzHHPENXdhYUtVcr-2kgu4_BTR8riw_dzxNaxuYLvV1NmxLAZte0PCFrf0YmiDUV1YgDFz_6Ne2v5WEWeH2-Nws6pHcAyenlORtznetdIucHx__rsvMOuZy7o_1PUPjB-z09uGmTiVNrzKI4ypkZFePwq6QArzC6FYw-xxe8hPnTGlWfH2r2IhDiE3L53CNrVPKhMXL-d6BYbRMsbBZ42mow_FeSU-WGdsXua85sop6VFU_aAkSqYyycn0tc86CLXLjkNzpkk84MRY7t8PwbIHlqSRs3DvqO51eCndMPdMWwN86YIfP04u1V5C9-2_ydCaEfHf1enPp6yKGDf-4gRmgtm2L0g19lDKFxNKH_o=w669-h892-no

 

I worked closely with Lars 1973 - late 80's....I heard from the other room in our house a light powered glider crashed in Sarasota...I stuck my head in the room and saw the tail of the plane and knew instantly it was him....he has gotten himself out of the plane ,stood and walked a bit then collapsed and died....carbon monoxide was speculation, but it was flat spin stick in the ground  

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59 minutes ago, Grey Dawn said:

The fighter Luke Skywalker would choose. Careful with the landing.

Lockheed_XF-104_(modified).jpg

Here's a story:

Daryl Greenameyer was a retired SR-71 pilot, and he managed to assemble an F-104 from parts; one of the few that was privately owned.  This was during the cold war, so the US and Russia were being a bit coy with records; rather than show what their aircraft could do, they would just beat the other guy's record by a bit.  So Daryl starts setting his own records; he got the low altitude speed record (988 mph, and it still stands), and was going for an altitude record when he had a landing gear failure.  He had to punch out and watch his baby auger in.   Not only did we build the Revell model to look like his plane, my buddy found a piece of the wreckage in the desert to put in the display case with it. 

 

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The Widowmaker was the sexiest fighter ever.

Yeager apparently zoomed one well over 100K feet.

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2 minutes ago, SailBlueH2O said:

I worked closely with Lars 1973 - late 80's....I heard from the other room in our house a light powered glider crashed in Sarasota...I stuck my head in the room and saw the tail of the plane and knew instantly it was him....he has gotten himself out of the plane ,stood and walked a bit then collapsed and died....carbon monoxide was speculation, but it was flat spin stick in the ground  

Sail,

    When I first read about the 'flat spin' crash I wondered if Lars could have survived the actual crash but died from the CO poisoning. The reason for my thinking so is for such a light wide span sailplane in a flat spin the rate of descent really isn't very high. My own sailplane has 12.6 meter span and is a bit lighter due to no engine and when the intial flight testing what done, a test pilot sort of freaked when it went into an inverted flat spin and and he bailed out. The plane fell like one of those maple seeds and ended up in a corn or wheat field. The pilot in his chute landed not far away at about the same time. When they pulled the wings and flipped it over the test crew were surprised to find that other than a smashed canopy (which was open for the bail out) there was no other damage. Seems they checked the plane out closely and put a new canopy on it and flew it again after a day or two! 

    There seems to be some debate about the CO poisoning in the Lars crash. Some blamed the CG due to the aft mounted motor on the 'flat spin' but the test pilot of the Windex has strongly refuted that. He seems to think that Lars suffered a case of narcolepsy. 

From http://www.aviationbanter.com/showthread.php?p=943655

My name is Steve Coan and I was the test pilot for every Windex that was built in the U.S. I did extensive flight tests and evaluation on the ship including spins and flat spins. I can tell you that Lars Bergstrom did not enter a flat spin. With his weight, the CG was very much sufficiently forward which would render a flat spin impossible. The notion that the engine mounted in the vertical stab could have contributed to entering a flat spin is "poppycock". Lars suffered from narcolepsy. Plain and simple: he fell asleep and entered a standard spin - to the ground. This was evident when I examined the crash site. The Windex 1200C is a might fine aircraft and I am looking to purchase another if I can find one!
Hope this helps.

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yeah there is some debate....and other darker speculation

Ras22...I tried to send you a SA message....but you do not accept messages

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50 minutes ago, SloopJonB said:

The Widowmaker was the sexiest fighter ever.

Yeager apparently zoomed one well over 100K feet.

I'll grant you it's a good looking fighter but I always thought the F-4 (if you like them athletic) or the F-5 (if you prefer them pettite) looked even better. Must be the twin engines. 

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1 hour ago, IStream said:

I'll grant you it's a good looking fighter but I always thought the F-4 (if you like them athletic) or the F-5 (if you prefer them pettite) looked even better. Must be the twin engines. 

I disagree with the first half.  The F-4 Phantom "looked like the box it came in" and was "America's proof to the world that a brick would fly with enough engines"  (Both are actual quotes from back in the day.)

OTOH, I agree that the F5 is one of the prettier jets ever. 

 

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14 minutes ago, Kirwan said:

I disagree with the first half.  The F-4 Phantom "looked like the box it came in" and was "America's proof to the world that a brick would fly with enough engines"  (Both are actual quotes from back in the day.)

OTOH, I agree that the F5 is one of the prettier jets ever. 

 

As a boy in the 1950's the  F-86 Sabre 

was my favorite

 

F 86.jpg

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Shoulda, known you guys would instantly come up with a bunch of examples!  This old fighter guy is gonna go stand humbly in a corner for awhile...

I wonder how long the composite structures of those gliders can standup to the cyclic loading, and if there is a way to tell if you start to have cracking/delams, etc.  I remember when the Navy took delivery of some F-16s to use as adversary aircraft at Topgun.  F-16 was capable of a sustained 9Gs, and was rated to 9Gs.  But as USAF had designed and used it mostly in a strike role, most of them weren't routinely subjected to alot of time at 9Gs.  After the Topgun guys flew them for awhile, constantly performing as a 4th Gen Fighter (think Mig-29), they ended up cracking the center barrel of the jet, and having to ground the fleet and re-engineer/repair the center barrels to take the constant G-loads.

I remember watching Italian F-104's doing touch and go's at Sigonella.  Doing something like 195kts on final.  As I recall, that's about the speed of a Tomcat with the wings stuck in the full aft position.  It's amazing how little wing that airplane has...Sloop the one Yeager was in was modified to also be rocket powered.  reaction rockets in the nose failed, and it departed when he couldn't get the nose back down.  He eventually got out of it, but got pretty badly burned when the seat hit time after ejection...

NF-104.jpg

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If shallow draft keels were equal in performance to deep draft keels, then ALL boats would be built as shallow draft.

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6 minutes ago, Crash said:

Sloop the one Yeager was in was modified to also be rocket powered.  reaction rockets in the nose failed, and it departed when he couldn't get the nose back down.  He eventually got out of it, but got pretty badly burned when the seat hit time after ejection...

NF-104.jpg

I knew about the ejection bit but didn't realize or at least remember that it was connected to the big zoom. Also didn't know it had reaction controls - thought it only had big balls for that sort of thing. Yeager was the only childhood hero I ever had. To have done all the crazy shit he did and still live into your 90's - maximum cool life.

I love that "departed" term. :D My favourite was "The aircraft departed controlled flight and entered the ocean" - translated - they crashed into the water.

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My favorite is "controlled flight into terrain."  Meaning you flew into the side of a mountain, or dove to steeply and couldn't pull out...

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The Yeager quote is this:

"A crash happens when a pilot runs out of altitude, airspeed and ideas all at the same time"

 

There's probably a corollary about boats and a lee shore. 

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3 hours ago, Rasputin22 said:

There seems to be some debate about the CO poisoning in the Lars crash. Some blamed the CG due to the aft mounted motor on the 'flat spin' but the test pilot of the Windex has strongly refuted that. He seems to think that Lars suffered a case of narcolepsy. 

Aft CG is only one of the problems with the engine so far aft. The polar moment will be a lot greater which makes stopping a spin harder. But we will never know. I thought it was kind of a neat glider.

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1 hour ago, Crash said:

I wonder how long the composite structures of those gliders can standup to the cyclic loading, and if there is a way to tell if you start to have cracking/delams, etc. 

The Schleicher ASK21 is their two place all composite trainer and it is aerobatic (only to 6G I think). It has been around a long time and they've made a lot of them. They started with 3000 hour tentative life, then due to experience extended it to to 6000, then 9000, then 12000, then 18000, and more recently I believe it has been made indefinite "on condition" that it is inspected every 3000 hours. Of course not all of them are subjected to 6G all the time, but rather to students - which is probably worse. 

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I guess the Windex sort of faded away after the crash with Lars. This was a link to the NTSB on that incident but I can't seem to get it to work with the present NTSB website. I'm looking for the original designers who seem to be Storch, maybe the same family that did the Storch STOL craft.

Image result for storch aircraft

No, that is just German for Stork. Hans Storck seems to be who I am looking for.

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29 minutes ago, DDW said:

The Schleicher ASK21 is their two place all composite trainer and it is aerobatic (only to 6G I think). It has been around a long time and they've made a lot of them. They started with 3000 hour tentative life, then due to experience extended it to to 6000, then 9000, then 12000, then 18000, and more recently I believe it has been made indefinite "on condition" that it is inspected every 3000 hours. Of course not all of them are subjected to 6G all the time, but rather to students - which is probably worse. 

Wow, That's impressive!  You'd think I'd stop being amazed at the range of knowledge of the folks here...but then I find a thread like this, and get amazed all over again.

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Bob wrote an article about keel design and shapes a few years ago. Was most informative.

I have sailed behind, but not for long, larger long keeled boats, when it was blowing over 30. I was amazed at how sideways they managed to go. Was sailing my Viking 33 number 12.

We managed to go around Vancouver Island this year, in to many bays, and dodging quite a few rocks. Got close to home and hit one near Nanaimo. It is really easy to do, once you get the hang of it. Keel is about 4 inches too long. All fixed for next time.

Unkle Crusty

 

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21 minutes ago, Unkle Crusty said:

Bob wrote an article about keel design and shapes a few years ago. Was most informative.

I have sailed behind, but not for long, larger long keeled boats, when it was blowing over 30. I was amazed at how sideways they managed to go. Was sailing my Viking 33 number 12.

We managed to go around Vancouver Island this year, in to many bays, and dodging quite a few rocks. Got close to home and hit one near Nanaimo. It is really easy to do, once you get the hang of it. Keel is about 4 inches too long. All fixed for next time.

Unkle Crusty

 

Let me guess. Shipyard Rock on Gabriola?

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