Search found 1315 matches

by marcelo_malara
Sat May 15, 2021 4:45 pm
Forum: Naval Weapons
Topic: Torpedoes explosions at the end of run
Replies: 6
Views: 334

Re: Torpedoes explosions at the end of run

What would happen with the torpedo sinking at the end of the run? Would the collapse of the warhead because of the water pressure make it explode?
by marcelo_malara
Wed May 12, 2021 3:03 pm
Forum: Naval Weapons
Topic: Torpedoes explosions at the end of run
Replies: 6
Views: 334

Torpedoes explosions at the end of run

Hi guys. Do you know if any navy did have a specific policy about detonating the warhead at the end of run? Have heard this, but for example could not find the specific mechanism in (for example) the Mk14´s torpedo manual in the HNSA site .

Regards
by marcelo_malara
Tue May 04, 2021 2:46 am
Forum: Naval History in General
Topic: the main armament of the General Belgrano
Replies: 25
Views: 1573

Re: the main armament of the General Belgrano

No, it was armed with 6" and 5" guns, plus Bofors 40mm, may be Oerlikons, and two Sea Cat missile launchers. No way that at that distance even the Exocet would be useful for a target located close to the islands. Anyway, she was on a war cruise and as such was a legitimate target, even her CO Capt B...
by marcelo_malara
Wed Apr 28, 2021 12:15 am
Forum: Naval History (1922-1945)
Topic: Scharnhorst/Gneisenau’s Northern Patrol Raid Question
Replies: 3
Views: 319

Re: Scharnhorst/Gneisenau’s Northern Patrol Raid Question

Just to coincide on Haar, both books about Norway are unequaled.

Regards
by marcelo_malara
Tue Apr 27, 2021 12:44 am
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 970

Re: Raumotters to the Rescue

Oh yes, the stress as you described would be higher than the smooth water towing. Other issue would be the towing cable friction against the mine´s mooring cable as it travels to the cutter.
by marcelo_malara
Mon Apr 26, 2021 4:26 pm
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 970

Re: Raumotters to the Rescue

There is no way that the pull would be 30 tons. Let me do some calculations. The paravane is subjected to two forces , lift and drag (plus weight and buoyancy, that have no part on this calculation), the resultant of them would give the angle of the tow. Should the resultant be 30.000 kg, the lift w...
by marcelo_malara
Sun Apr 25, 2021 5:36 pm
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 970

Re: Raumotters to the Rescue

I have this graphic of the British paravanes, from British Naval Weapons of World War Two Vol 1. It has a biplane cambered wing configuration, much alike a WWI fighter plane. Interestingly, the amount of pull of the tow seems to act in the link 4, against the spring 18, to set the angle of attack of...
by marcelo_malara
Sat Apr 24, 2021 8:29 pm
Forum: Bismarck General Discussion
Topic: structure on Bismarck conning tower
Replies: 11
Views: 443

Re: structure on Bismarck conning tower

Brower´s said for it:

FuMO 21 radar (possible)
by marcelo_malara
Sat Apr 24, 2021 8:19 pm
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 970

Re: Raumotters to the Rescue

Yes, may be I took it too far saying that most airfoils are symmetrical, I should have said most airfoils have curved up and down surfaces. As you said, the airfoil section is not the same along the span. I don´t understand this: "The whole plan view of each paravane generates tow load so must be mu...
by marcelo_malara
Sat Apr 24, 2021 4:37 pm
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 970

Re: Raumotters to the Rescue

Hi Wadinga. It is a most common misconception that a symmetrical airfoil will not generate lift. In fact, most aircraft wings are symmetrical, ranging from high speed propeller driven planes to commercial jets, asymmetrical wings with flat lower surfaces are confined to the general aviation low spee...
by marcelo_malara
Thu Apr 22, 2021 9:27 pm
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 970

Re: Raumotters to the Rescue

From Brower´s, Bismarck rudders measured about 5.5 m x 3.8 m. At 20 kt the force would be: Lift = 0.5 * 1000 kg/m3 * (3.8 m * 5.5 m) * (10 m/s * 10 m/s) * 1 Lift = 1045000 Newtons = 106600 kg Again we are assuming a value of 1 to the unknown Cl. Now I can say that the forces needed for turning the s...
by marcelo_malara
Thu Apr 22, 2021 4:42 pm
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 970

Re: Raumotters to the Rescue

Hi Wadinga. I have been thinking about this, but the very simple answer came to me this morning as I woke up :D :D :D . Let as review again the lift formula: Lift (force in Newtons) = 0.5 * fluid density * surface area * V^2 * Cl Now, the rudder is many times bigger than the paravane´s wing. So, if ...
by marcelo_malara
Fri Apr 09, 2021 7:44 pm
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 970

Re: Raumotters to the Rescue

Now remains the question if the force would be enough to correct Bismarck´s track. One may ask what happens if just ONE paravane is deployed in an undamaged ship, would the side force be appreciable?

Regards
by marcelo_malara
Fri Apr 09, 2021 7:38 pm
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 970

Re: Raumotters to the Rescue

Thanks for your kind words. So, if I understand the graphic well, for 20 kt the towing force would be around 80 cwt, 8000 pounds, around 3600 kg, so the approximation is close. As the lifting force varies with the square of the velocity, it is quiet logical that at half speed, 10 kt, the force would...
by marcelo_malara
Fri Apr 09, 2021 4:54 pm
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 970

Re: Raumotters to the Rescue

I did my homework :D :D :D. First let me review the formula of the aero/hydrodinamic lift of a surface traveling thru a fluid. Lift (force in Newtons) = 0.5 * fluid density * surface area * V^2 * Cl All are self explanatory except may be Cl, the coefficient of lift, a non dimensional parameter which...