Sweden: Vasa Museum - the rescued ship from Stockholm

[machining 4 all]

[marksbug]

totaly awesome!!! I didnt get to see the ship in the leonardo D museeum in Milan as they had something special going on and pushed us all out....I spent a lot of$$ to get there and they just pushed us out.some kind of gala or something...makes me wonder what a museum is for... although I did get to see a lot there I probably missed half due to the gala.

[machining 4 all]

It really is a work of art! Think of the time it takes to build something like that. It is a pity that ships of this type were used for war and destroyed in battle!

[ipsumental]

Wicked Cool! Truly the Volvo of warships. <img src="https://www.homemadetools.net/forum/images/smilies/smile.png" border="0" alt="" title="Smile" smilieid="1" class="inlineimg"> To see it in person would be the thing. Is it bigger or smaller than imagined. Are museums free? How much to see$. How big is it, by the way? Every square inch is a detail. Wood...weather...What did it look like new? Was it under water? Et cetera. Tell ya what. I can't take my eyes off of it. The displacement is barely imaginable. I wonder what Archimedes would say/think.

[hemmjo]

Those old ships were indeed so awesome. No power tools around when they were built. It was all blood, sweat and tears. There is nothing about them that is not totally awesome. This one is indeed a spectacular example. But even those much less ornate are still amazing.

https://en.wikipedia.org/wiki/Vasa_(ship)

[machining 4 all]

[DIYSwede]

Today: -Sweden's single biggest tourist attraction with over 1,5 M visitors 2019 (before Covid hit).
Yesterday: -The Pride of the Royal Navy, the most powerful battleship of the Baltic Sea, that just couldn't keep afloat.

FWIW: THIS particular ship didn't do any fighting at all, 2 years after Peter Minuit bought Manhattan for 24 bucks,
on Aug 10th, 1628, it simply keeled over on its maiden journey after abt 2 NM of sailing in light wind.
It was utterly unstable, had top-heavy rigging, an extra cannon deck added, sub-optimal material for keel ballast etc.
More info at: https://www.vasamuseet.se/en (No admission due to the pandemic until further notice)
On the disaster:https://www.vasamuseet.se/en/vasa-history/disaster

Some shots from its contemporary successor:

1st Official Press show landing (Pilot Induced Oscillation: Feb 2nd, 1989):

PIO hits again, 4 years later - now in central Stockholm (sic!) in an annual festival with several ten-thousands of spectators:



4:55 long video, 1st stall starts at 2:00:

Morale: Today's bad engineering can provide tomorrow's clickbaits and big tourist attractions in a few centuries...


Cheers

Johan

[machining 4 all]

Although we can film, nothing replaces a face-to-face visit to this and other museums around the world! They are places where we can notice all our intelligence and all our ignorance ...

[mklotz]

...
Morale: Today's bad engineering can provide tomorrow's clickbaits and big tourist attractions in a few centuries...

My understanding is that aircraft with canards must have the canard surfaces under constant computerized control to maintain stability. This seems to be borne out by the Wiki article on the JAS 39, which states

"The Gripen has a delta wing and canard configuration with relaxed stability design and fly-by-wire flight controls."

A further Wiki reference explains "relaxed stability" as

--------------------------
"In aviation, relaxed or negative stability is the tendency of an aircraft to change its pitch and bank angles spontaneously. An aircraft with relaxed stability cannot be trimmed to maintain a certain attitude, and will, when disturbed in pitch or roll, continue to pitch or roll in the direction of the disturbance at an ever-increasing rate."
----------------------------

so you're depending on the computer and its software to keep the plane in stable flight. Perhaps it provides some performance advantage but I don't want to fly in anything with canards.

Completely OT but didn't the Wright flyer have a single forward canard control surface?

[DIYSwede]

My understanding is that aircraft with canards must have the canard surfaces under constant computerized control to maintain stability.
//Snip//
so you're depending on the computer and its software to keep the plane in stable flight.
Perhaps it provides some performance advantage but I don't want to fly in anything with canards.

Completely OT but didn't the Wright flyer have a single forward canard control surface?

Might as well stray even further from the Vasa....

-That's correct, Marv - The Wright Flyer had canards (as well as pushing propellers).

Fly-by-wire & continous computer control is the trade-off for achieving maximum manueverability in all axes
for any aircraft with relaxed stability by design (with or w/o canards).

The Swedish Accident Investigation Authority (NTSB) has great FOI transparency,
where a "JAS 39" web search renders 13 hits, and the entire accident report is among those:

Link (Pdf in Swedish only): https://www.havkom.se/assets/reports...JAS-39-F-7.pdf

From "Investigation results":



Freely translated (grammar, terms most probably not correct):

"13. The Pilot's joystick maneuvres in the roll-out from the low-speed turn was overall the same in angle at the show as in pre-training.

14. That the stick started operating first at 2 deg starboard (due to the alpha >20 deg: the auto-disconnected roll auto-trim) meant that the stick momentarily hit max deflection, which led to quicker roll angular speed than in pre-training.

15. At the roll-out of the low-speed turn the rudders moved at their max angular velocity,
which in turn led to bigger and bigger time delays between stick movements and aircraft roll and pitch responses.

16. These time delays induced PIO in both roll and pitch, which after a few oscillations led to a/c stall.

17. "Rudder Security*"-warning light (for preventing precisely these flight conditions) was presented to the pilot
1 second after the a/c had become inmaneuverable.

The show flight sked had a max allowed alpha of 20 deg, and a lowest permissible altitude of 1000 ft -
The low-speed turn started at 750 ft @ 150 kn and full afterburner with a 21,7 mean value of alpha.
* Max rudder angular velocity reached: A "-Lean off the stick"-instruction...
Later simulations has also shown that it can be stalled at alpha less than 20 deg too...

(Personal: -Nowhere in the report are actual METAR data displayed,
which could've been great for evaluating the density altitude of the flight,
and given the low flight level aerobatics involved, having a low pressure,
high temp and humid air doesn't improve maneuverability.)

-Oh yes, I almost forgot: -No more jet fighter aerobatics in central Stockholm allowed. Ever again.

Johan