Water Pressure Question

[Kitsune]

If you have a hose spraying water at 18 meters per second, how would I calculate how much pressure that would exert on a flat plate?

[raptor3x]

p_t = 1/2*rho*u^2 + rho*g*h + p_s = constant

If you're looking for a way to determine the force exerted on the plate, conservation of momentum would be the better option.

[Starglider]

If you have a hose spraying water at 18 meters per second, how would I calculate how much pressure that would exert on a flat plate?

A parallel stream of water hitting a 1 metre square plate would deliver 18 cubic metres of water per second, weighing 17964 kg at room temperature/pressure. The force required to deccelerate that mass smoothly to a halt would be 323.3 kN. Obviously the mass isn't deccelerating smoothly but the force exerted should be equivalent - perhaps a bit higher due to rebound/splashback - for a pressure of about 350 kPa (3.5 bar).

[Kitsune]

Starglider, thank you for your help

I am in a debate about what would happen if a torpedo was to hit the gates of the Gatun spillway. A person stated that the water would flow out at 35 knots (with is about 18 meters per second) and you calculated it to be 350 kPa.

What I am getting is that water pressure at the bottom of the gate which is around 20 feet deep is around 160 kPa, less than half.

Basically, the person is trying to say that it would be impossible to patch such a hole

[Starglider]

Basically, the person is trying to say that it would be impossible to patch such a hole

They're being foolish. You'd just have to sink enough ballast (e.g. huge concrete blocks) upstream of the hole to block the flow. This is a challenging operation to be sure but easily comparable to the kind of feats civil engineers perform when building bridge supports in fast-flowing rivers, tidal defences etc.

[Kitsune]

My quick idea would be to sink a barge to block the flow...now thinking that a large steel patch lowered into position would be better

[Sea Skimmer]

The guy you’re arguing with isn’t going by the name robdab by chance, and claiming that couple flying boats could destroy place is he? That guy’s been going to every forum he can to proclaim what a brilliant idea he’s come up, and he just puts up a wall of ignorance every time one tries to debate it with him.

Anyway you could use several tactics to block a damaged spillway gate, sinking a ship would work fairly poorly but it could slow down the rate of loss, some combination of steel sheet pilings and cables would likely work best. The steel could be obtained quickly from the emergency dams maintained to prevent loss of water through the locks if the lock gates failed.

Also keep in mind, with the lake at its normal level the spillway gates are only holding back 16 feet of water. The maximum draught of a ship in the canal was 44 feet. This means even if the spillway gates are compromised and the entire lake drains down (which would take quite some time) ships of up to 28 foot draught could still use the canal! That includes almost all of the world’s merchant ships and Yorktown class aircraft carrier at full load! Even US battleships could still transit if they first offloaded a good deal of fuel, most standards as they stood in 1941 drew about 30-32 feet loaded. At worst this would add a day to transit for defueling and refueling on the other end.

In short the canal would not be closed at all! The only limitation would be with less water stored, transits could not be sustained at a high rate. That would affect merchant shipping, but certainly not warship transits. However releasing water from the Madden dam could be used to help make up the difference anyway, this was the whole point of building that dam, and in the wet season Panama got so much rain you’d hardly notice the loss…. This was after all the whole reason for building such a big spillway.

[Kitsune]

You hit in one...This is his post

Could the Japanese have knocked out the Panama Canal had they attacked it on Dec.7'41 ? I believe so and the following is my suggestion as to how they could have accomplished that feat at the same time as the historical Pearl harbor air raids were going on. Sorry about the length of it.

One source, http://www.history.army.mil/books/wwii/ ... s/ch12.htm indicates that, "Plans for protecting the Canal against sabotage during an international crisis of this sort had been drawn up in Panama and given constant study ever since the spring of 1936. Now, steps to put them into effect were quickly taken. Three basic measures had been provided for: first, the installation and operation of special equipment in the lock chambers, designed to detect underwater mines and bombs and to prevent damage from this cause; second, the restriction of commercial traffic to one side of the dual locks; and third, the inspection of all ships before they entered the Canal and the placing of (2-25) armed guards on vessels while in transit through it. These measures were instituted between 26 August, when the President gave Secretary Harry H. Woodring the signal to go ahead, and 1 September."

So, blockship sabotage success there would thus be very unlikely.

The Japanese surprise air attack that I have in mind instead would see just 3 H6K "Mavis" floatplanes flying in the 855 nautical miles (984 regular miles) from the Galapagos Islands on the afternoon of Dec.7'41 (timed to match with the OTL strike on Oahu). I'm not bombing Panama, I'm torpedoing it instead.

Sneaking a surface warship or two across the busiest shipping lanes of the wide Pacific, un-noticed a la the Kido Butai, would most likely be impossible even in peacetime so a "show-the-flag" state visit voyage by the IJN seaplane tender Chitose would have to provide a "good enough" peacetime cover story to get them into air range. With official permission from the governments of the countries scheduled to be visited, naturally. Perhaps the OTL flag delivery "1941: To commemorate the 400th anniversary of the founding of Santiago, Japan presents Chile with a giant Chilean flag." mentioned at http://www.janm.org/projects/inrp/engli ... _chile.htm might have been a good excuse for Chitose to visit Chile ?

We know that in the OTL Japan tried (unsuccessfully) to buy oil from several suppliers in Central and South America, after the start of the American led embargo. A newspaper announced port-to-port IJN tour thru international waters there could have been used as a part of an ATL Japanese diplomatic effort to secure new supply contracts. Not at all likely to succeed but that would not have been Japan's real intention in this AH case, anyway. Scheduled visits to Chile and Argentina would be far away from Panama. Suspicious in that time of high international tension to be sure but not unheard of as the IJN had been conducting annual OTL round-the-world cadet training cruises for decades previous.

What world power would be greatly worried about 1 lone seaplane tender on tour ? Completely un-announced in the newspapers would be a detached fast IJN auxilliary oiler and Chitose's close escort of 3 IJN submarines, each capable of 21 knots on the surface.

Chitose's OTL assignment at Mindanao could be fulfilled by Japanese CVL Hosho, detached from the mostly idle Combined Fleet.

Much as was done historically with the Tatsuta Maru's fake voyage thru Honolulu (see Prange's "At Dawn We Slept") Chitose's schedule of South American ports of call visits would be published in various newspapers by the local Japanese consulates but she would never arrive there. If spotted by US/UK/Dutch forces on her way across the still peacetime Pacific prior to Dec.7'41, she would merely be reported as being on course and schedule for those announced port visits. On the evening of Dec.6'41 she (and her 3 submarine escort) would quietly anchor instead in a deserted lee bay somewhere in the Galapagos Islands, owned by Ecuador. That South American nation had a substantial Japanese population in 1941, many of whom were fishermen or guano miners outon the Galapagos. Both being good covers for the pre-war scouting of a suitable anchorage for Chitose and her 3 big floatplanes.

Chitose was originally built to handle 25 single engined seaplanes with 4 catapults and 5 cranes as per the painting to be seen at http://www.combinedfleet.com/chitosesp_t.htm In order to hoist a much heavier/larger 4 engined Mavis aboard at least one of those cranes would have needed to be upgraded to one similar to that installed on the much smaller Akitsushima as seen at http://www.aeronautic.dk/Warship%20Akitsushima.htm

AFAIK the US had only 12 PBYs based on the Pacific side of Panama before Dec.7'41 so my AH Japanese warship would have a clear advantage when launching it's 3 surprise air attacks. All three Mavis floatplanes would be hoisted over the side during the previous night, checked out, fueled and armed with twin "shallow water" torpedoes of the same newly perfected type as used by the Kido Butai for their air attack on Pearl Harbor. After an open water takeoff all three would depart at different speeds and on differing courses, for Panama. The reason for those seperate but co-ordinated flight approaches to Panama being the more than passing resemblance of the Mavis to the PanAmerican Airline's "China Clipper" aircraft, the Sikorsky S-42. If pre-painted in Pan-Am colors and markings, any observer expecting to see a lone "China Clipper" pass by overhead could certainly mistake a single Mavis for one of them instead. By no coincidence at all, Pan-Am was flying a daily "China Clipper" shuttle service on the Miami - Costa Rica - Panama - Columbia - Venezuela - Buenos Aries route at the time. As well as developing a trans-Pacific route thru the Galapagos Islands.

Please compare for yourself at http://www.warbirdphotographs.com/NavyJB&W/H6K-8s.jpg and http://www.flyingclippers.com/S42.html . Both with 4 engines and twin tails.

Each Mavis could carry a pair of torpedoes as per http://www.warbirdphotographs.com/NavyJB&W/H6K-1.jpg with the wooden tail fins giving a framework for the attachment of breakaway "fuel tank panels" added to help with their appearance as long ranged China Clippers.

The target of those 3 Mavises being the Gatun Dam's (not the Gatun Locks) spillway gates which controlled the water level in man-made Gatun Lake and thus, the operation of the entire Panama Canal.

The Gatun Dam itself, an earthfill structure is far too thick to be affected by a torpedo warhead but the same cannot be said wrt the central spillway gates. Only about 8 of the Dam's 14 steel spillway gates could be targeted by air dropped torpedoes because as http://www.panoramio.com/photo/5294557 shows, that curving spillway structure (to the upper left of the photo with the Gatun Locks being seen to the upper right of that photo) is in a somewhat screened position. Each of the 14 electrically raised steel spillway gates were 45' wide by 20' high and made of 1/2" thick plate. Photos of the underwater damage done by Japanese aerial torpedoes to a US battleship at OTL Pearl Harbor leave no doubt that just one torpedo hit would easily destroy each such much weaker spillway gate. Please see http://owensarchive.com/world-war-ii/pe ... d_104.html

Certainly the US was aware of the vulnerability of the Gatun Dam spillway TO BOMBING as early as 1923 when a training exercise called Fleet Problem I, which is documented at http://en.wikipedia.org/wiki/Fleet_P..._note-Wright-1 , pointed that out quite dramatically.

My questions is, what, if anything, did they do about it ? I suspect little as the US defenders of Dec.6'41 Panama did NOT know that the Japanese had perfected a shallow drop depth aerial torpedo and thus would not have been likely to protect against such, just as the OTL at Pearl Harbor illustrates. AA guns may have been deployed at the then peacetime Gatun Dam (but I have yet to find any confirmation of that) however they would be placed so as to protect against overhead bombing, not torpedo drops from some distance away, well out over Gatun Lake.

I do know that 3 US interceptor squadrons, each of 10 x P-36 fighters, were flying in Panama already but AFAIK the 71 more modern P-40s which had just arrived were not operational there until well after Dec.7'41.

However, I have found several sources which do NOT present the other OTL American defences in a good light:

For example, page #349 of http://www.history.army.mil/books/wwii/ ... s/ch13.htm summarizes the state of Dec.'41 US defences at Panama against a surprise air attack: "He did, however, call to the attention of the War Department certain deficiencies in the defenses of the Canal. In General Andrews' opinion, the commandant of the naval district did not have enough planes or vessels under his control to conduct an adequate reconnaissance. The Aircraft Warning Service in the theater, he reported, was totally inadequate in personnel to supervise the installation of detectors on hand as well as to man the equipment when installed. Only two radar detectors were installed and in operation in the Panama Canal Department. The harbor defenses had less than one complete manning detail available. The antiaircraft artillery had insufficient personnel to man the armament being installed in the Canal Zone and only enough ammunition for one minute of fire per gun for the 37-mm. guns. There were no barrage balloons. The Air Force,General Andrews continued, was totally lacking in night pursuit planes and in very-high-frequency radio equipment with which to direct pursuit in air. Only 8 modern long-range B-17C bombers and 12 modern AC-20 light bombers were available..."

One minute worth of AA fire hardly inspires any confidence that a surprise IJN air attack could be prevented from reaching good positions to launch unexpected torpedo attack on the Gatun Dam. The US Army itself estimated that loss of all of the water stored in Gatun Lake would have prevented all Canal operations for a period of at least two years and possibly three, depending on the refill rates dictated solely by local rainfall amounts.

It is NOT a photo of the Gatun Dam spillway but if you would go to http://www.pbs.org/wgbh/buildingbig/won ... 2_dam.html
you will see the closest detailed photo that I could find.

The thin nature of the steel gate is shown, as are the still attached lifting chains that would have raised and lowered the gate had it's left side anchoring rail not failed just before this 1995 photo was taken.

If that volume of water is coming thru with the gate still in place, just imagine the current and flow volume if the gate was blown right off ?

Page #274 on http://www.ibiblio.org/hyperwar/AAF/I/AAF-I-8.html provides the assertion of: "The problems involved in providing a serviceable radar screen to alert the inner defenses of the Canal were less easily solved. Equipment in use at these stations was "inadequate" for early warning and "quite useless" for purposes of controlled interception. Sites had been selected for four British-type radars, the sets to be supplied from Canadian production, but improvement in equipment could not overcome deficiencies of operating personnel. Operators in Panama were largely untrained, had been given no indoctrination in the need for precision standards, and were frequently unenthusiastic about their assignment. Radar crews had made no effort to plot the permanent echoes in their search areas, and therefore could not discriminate between such "echoes" and "live" targets. The combination of inadequate equipment, poor site selection, and untrained operators produced such inefficiency that even the best station in Panama was "far below any acceptable standard of operational utility." The elimination of all the deficiencies noted depended on action by the War Department to provide improved equipment and better trained crews. No complete remedy was available to local commanders."

Pages #424-426 of http://www.history.army.mil/books/wwii/ ... s/ch16.htm provide: "Although General Andrews recognized the U-boat campaign as "a definite menace to our war effort," he considered the canal to be "the one real enemy objective" and its protection to be his "paramount mission." Although he was somewhat concerned about the possibility of German surface raiders penetrating [from] the Caribbean, he was more than ever convinced that the principal threat was by carrier-borne aircraft from the Pacific.

The means for detecting an enemy carrier force before it launched its planes and for sighting the enemy planes before they reached the canal were the nerve center of the Panama defenses. Patrol planes, operating at about the 900-mile radius, were depended upon for the initial warning of an enemy's approach. Long-range radar (the SCR-271 and its mobile version, the SCR-270) was relied upon for the detection of enemy planes at distances up to about 150 miles. Still closer-in, the fixed antiaircraft defenses relied upon short-range, height-finding radar (SCR-268) for searchlight and fire control.

At the time of the Pearl Harbor attack however, serious deficiencies existed in the warning and detection system. There were not enough planes and operating bases to carry out the search as planned. There were only two SCR-271 radars in operation, one at each end of the Canal. Although three additional sets arrived by the end of December and were being installed on the Pacific side of the Isthmus, the work was slowed down by a shortage of trained radar engineers and mechanics.

There were nevertheless certain deficiencies which were not entirely the result of a shortage of equipment and trained men. Tests in Panama repeatedly disclosed that low-flying planes approaching directly over the Bay of Panama were not detected by the radar system. Visiting British experts had noted this characteristic in American sets and attributed it to a basic defect of the equipment, but the Signal Corps insisted that, properly placed and operated by competent crews, the American equipment in this respect was just as good as, if not better than, the British radar. Whatever the cause, the blind spot remained. Furthermore, neither the SCR-270 nor the SCR-271 was designed to show the elevation of the approaching plane, and neither gave a continuous tracking plot. These qualities were indispensable for ground-controlled interception (GCI), which British experience had demonstrated to be the most successful method for conducting an air defense.

Pages #160-166 of: http://www.ibiblio.org/hyperwar/AAF/I/AAF-I-5.html detail the poor overall situation in Panama: "The vital importance of this phase of Canal defense was revealed in an estimate of enemy capabilities prepared by the Caribbean Defense Command in the latter part of November 1941. Japan was regarded in respect to the Canal itself as the primary potential enemy, and a carrier-based attack from the Pacific was considered "not an improbable feat." Other possibilities were taken into account, but it was concluded that in any event the most important defensive measure was "increasing and thorough reconnaissance and observation of the air, sea, and land approaches to the Canal Zone." Existing forces in the area were regarded as sufficient to repel any probable initial attack on the Canal provided they were given "timely warning" of the approach of hostile forces. The inability of defending naval and military air forces to perform the required amount of reconnaissance and to provide the "timely warning" constituted perhaps the chief weakness in Caribbean defense immediately prior to American entry into the war. It was a weakness which was recognized by both Army and Navy commanders, their expressed hope lay in the postponement of attack by an enemy until the defending forces could achieve the proper degree of co-ordination and the necessary equipment for complete coverage of the vast sea frontiers."

THUS IT IS REVEALED THAT THE PRIMARY US DEFENSE OF THE PANAMA CANAL IN DECEMBER 1941 RELIED SOLELY ON THEIR MERE HOPE THAT THE JAPANESE WOULD NOT ATTACK THEM ANYTIME SOON !!!

Just how pathetic was that ?

Had the Japanese but known ... or dared ...

Your thoughts, constructive criticisms (with sources), please.


P.S. - It does occur to me that this mission might be undertaken without Chitose if just the 3 submarines are used for refueling and torpedo hauling out to the Galapagos as the Japanese did at French Friagte Shoals in March '42 for their failed 2nd night bombing raid on Pearl Harbor. I'm just not sure what route that my 3 fake ATL Pan-Am China Clipppers could fly to get there without being spotted & reported ?

Veni, Vidi, Velcro. - I came, I saw, I Stuck Around

[Sea Skimmer]

You’re really wasting your time then. His plan has some merit as a harassment attack, but he will NEVER acknowledge that even the slightest problem of coordination exists, and he’ll admit that hitting the spill way is not fatal damage. He also doesn’t understand that because the gates are so thin, they wont offer much resistance to a torpedo explosion.. and thus will take LESS damage then the side of a battleship (even the outer skin of a battleship is thicker, let alone the inner hull ect...) because the blast partly vents to the empty air. Not that it matters anyway, its just some sliding steel plates. Once the water drops you can move a boat right up and get to work welding.

In fact he’s actually claimed that claim that fixing the spillway would be harder then clearing a major landslide out of the Gaillard…. Yeah right. Not that hitting the cut is more practical, but it just shows how much he’s just on a personal mission to convince the whole internet that he figured out how Japan can win WW2. He’s been on at least a half a dozen different forums, and pissed off a whole lot of people.

[Sky Captain]

In case Japanese managed to take out Panama canal how increased travel time from Atlantic to Pacific oceans would have affected outcome of WWII. Panama canal operational or not does`t change the fact US still has massive industrial advantage. I can imagine war in Pacific may have dragged on a bit longer but outcome would still be the same. Nuclear bomb would still be developed and used against Japan.

Sometimes I`m wondering with which part of their body Japanese military planners thought when they decided they can take on US and still come out victorious.

[Sea Skimmer]

In case Japanese managed to take out Panama canal how increased travel time from Atlantic to Pacific oceans would have affected outcome of WWII. Panama canal operational or not does`t change the fact US still has massive industrial advantage. I can imagine war in Pacific may have dragged on a bit longer but outcome would still be the same. Nuclear bomb would still be developed and used against Japan.

You’re completely right; America’s advantage was far too great for the canal being even totally blocked to have long term significant strategic effect. Transit time around Cape Horn would be about six weeks given typical warship cruising speeds. Merchants are generally slower, but its still a shorter route then many ships sail at the time. In all likeliness any damage to the canal short of total demolition of the lock structures was going to be repairable in 6-12 months.

Considering the actions of the USN in the first six months of the war hardly mattered, this is not a crippling limitation. The war against Japan couldn’t really begin in earnest until mid 1943 no matter what, we needed that time to build our amphibious fleet. But once it got started at Tarawa in November 1943 it just didn’t stop.

Sometimes I`m wondering with which part of their body Japanese military planners thought when they decided they can take on US and still come out victorious.

When one giant colossal out of control war fails, the best solution is to launch even more colossal wars against even more powerful nations! The only real explanation for this is simply that Japans leadership was still stuck in a feudal mindset in which wars and the exchange of territory for peace was a standard form of interaction. This mindset had only been reinforced by the ‘short victorious war’ of 1904-05 against Russia, which seemed to ‘prove’ to Japan that it could defeat a much larger nation with superior skill and inferior forces. They just didn’t get that Imperial Russia, or disunited China, was just not even in the same league as America. But then… even Britain was a superior industrial power to Japan on its own.

In the end you can call them stupid, and its just plain true. Unfortunately you can also draw a lot of comparisons between the Japanese run up to WW2 and the ‘cheap victories’ they won against Russia and China and the military actions of the United State following its own cheap victories in 1991/1995/1999 period. Get it in someone’s mind that war works, and it works cheap, and they’ll keep trying it. Everyone always plans for the short victorious war… (victory in six weeks/months/by Christmas are such common predictions) anything else just looks crazy.

[Kitsune]

Well, he got banned for attacking members of the group.....
He was asked to moderate his tone but decided to respond insultingly to the moderators

The group is far more religious than this board and the majority are conservative as well. The age of the members is much greater than this board, average is likely around 50 years old.
Being all that, I have argued greatly in such issues and have never even been warned.

[Sea Skimmer]

I’ve dealt with him on three forums; well I’ve seen his activity in detail on three forums anyway, only really dealt with him on two. He was banned from one, and if the other two had any effective moderation at all he’d have been banned from them as well. He even went so far as to start pursing people onto completely separate message boards to harass them about having dared to question his brilliance at one point. Don’t encourage him by wasting your time debating.