Search found 1324 matches

by marcelo_malara
Sun Apr 25, 2021 5:36 pm
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 1098

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: 517

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: 1098

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: 1098

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: 1098

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: 1098

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: 1098

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: 1098

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: 1098

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...
by marcelo_malara
Fri Apr 09, 2021 2:36 pm
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 1098

Re: Raumotters to the Rescue

Physics is my second love! If you can measure the hydrodinamic surface of a paravane we can guesstimate the pull.
by marcelo_malara
Fri Apr 09, 2021 1:21 am
Forum: Naval History in General
Topic: Trimaran Ship of the Line?
Replies: 3
Views: 577

Re: Trimaran Ship of the Line?

I don´t get the point of why would they be shallower in draft.
by marcelo_malara
Fri Apr 09, 2021 1:17 am
Forum: Bismarck General Discussion
Topic: Raumotters to the Rescue
Replies: 26
Views: 1098

Re: Raumotters to the Rescue

I don´t believe they would produce enough lift to counter a 50.000 t ship out of control.

Regards
by marcelo_malara
Tue Feb 23, 2021 1:22 am
Forum: Books and Reference
Topic: Anatomy of the Ship Scharnhorst - Stefan Draminski
Replies: 1
Views: 512

Re: Anatomy of the Ship Scharnhorst - Stefan Draminski

I received mine today. It is very well done, to say otherwise is untrue. Incredible heavy for an AOTS, 400 pages, the closest one (that I have) is Dreadnought with 256 pages. The plans are accompanied by 3D renderings, which are excellent to understand the superstructure. No, it has not the detailed...
by marcelo_malara
Sun Feb 21, 2021 4:06 pm
Forum: Off Topic
Topic: trawler damaged by explosion in North sea
Replies: 9
Views: 1239

Re: trawler damaged by explosion in North sea

Yes, any kind of detonator that needs no contact with the ship, mostly magnetic in WW2, I am not sure if there were acoustic detonators then, will go to Campbell´s book to confirm. They have interesting (and deadly) capabilities. For example they would go live after a preset time, not only for the l...
by marcelo_malara
Fri Feb 19, 2021 3:17 pm
Forum: Off Topic
Topic: trawler damaged by explosion in North sea
Replies: 9
Views: 1239

Re: trawler damaged by explosion in North sea

The mine proper has positive buoyancy, so it will always float near the surface, unless the mechanism in the sinker has failed and taken it to the bottom. If it exploded in the bottom it was most probably an influence mine, remember that they can seriously damage a ship in depths of more than 20 fat...