Search found 1282 matches

by marcelo_malara
Tue Apr 07, 2020 12:37 am
Forum: Naval Weapons
Topic: Wind correction in long range gunnery
Replies: 3
Views: 532

Re: Wind correction in long range gunnery

I think that the variation responds to the dynamic pressure formula: Q = 0.5 * rho * V^2 * S * C rho = air density V = velocity S = surface exposed to the flow C = a non dimensional coefficient related to the form Air density decreases with altitude, approximately linearly for the lower atmosphere, ...
by marcelo_malara
Sun Apr 05, 2020 5:47 pm
Forum: Bismarck General Discussion
Topic: Wind Behavior: 0400 - 0600
Replies: 35
Views: 1828

Re: Wind Behavior: 0400 - 0600

We cannot disregard "the human factor", may be at 6 am, just in the middle of the battle, the crew was a little busy and worried to assess correctly the wind direction. Anyway, there are some explanations that I can put forward: -changes in wind speed: they just happen at any moment, are very common...
by marcelo_malara
Sat Apr 04, 2020 11:08 pm
Forum: Naval Weapons
Topic: Wind correction in long range gunnery
Replies: 3
Views: 532

Wind correction in long range gunnery

Hi guys, a question related to wind. What was the effectiveness of putting the wind in the long range gunnery calculation? The firer can only measure the wind direction and speed at sea level, on firing the shell will climb many thousand meters, passing by atmospheric layers with different wind dire...
by marcelo_malara
Sat Apr 04, 2020 10:46 pm
Forum: Bismarck General Discussion
Topic: Wind Behavior: 0400 - 0600
Replies: 35
Views: 1828

Re: Wind Behavior: 0400 - 0600

Hi Bill. The sources are: https://www.netweather.tv/charts-and-data/gfs-archive https://www.metcheck.com/WEATHER/gfs_reanalysis_1871_now.asp# Don´t specify time of the charts. There is a third site: https://www.wetterzentrale.de/reanalysis.php?map=1&model=noaa&var=1&jaar=1941&maand=05&dag=21&uur=000...
by marcelo_malara
Sat Apr 04, 2020 5:42 pm
Forum: Bismarck General Discussion
Topic: Wind Behavior: 0400 - 0600
Replies: 35
Views: 1828

Re: Wind Behavior: 0400 - 0600

Added to the excel the corretion for gradient wind around a low. The gradient wind is the one that besides pressure gradient force and Coriolis effect, takes into account the centrifugal force provoked by the wind following a curved isobar. Using the same presure gradient as before, and measuring th...
by marcelo_malara
Sat Apr 04, 2020 4:26 pm
Forum: Warship Photos
Topic: Can anyone identify these cannon?
Replies: 2
Views: 5385

Re: Can anyone identify these cannon?

A little late, I would like to see the photos.

Regards
by marcelo_malara
Sat Apr 04, 2020 4:11 pm
Forum: Books and Reference
Topic: A strange occurance
Replies: 2
Views: 406

Re: A strange occurance

Like you said Paul, the pilot decided not to shot down an already heavily damaged and defenseless B-17, allowing it to return to UK. I think that we spoke about it in this forum years ago. Personally, I don´t think any lives were spared, because surely the crew flew again another bomber mission to k...
by marcelo_malara
Sat Apr 04, 2020 3:58 pm
Forum: Bismarck General Discussion
Topic: Wind Behavior: 0400 - 0600
Replies: 35
Views: 1828

Re: Wind Behavior: 0400 - 0600

Thanks for your words Byron. Hans, I mentioned 15/20 for some wind below the 26 surely found in the UK, may be it was 15, I don´t really know. There is a way to calculate it accurately, besides the pressure gradient (pressure diff / distance) the radius of the curved isobar needs to be used in a for...
by marcelo_malara
Sat Apr 04, 2020 3:51 pm
Forum: Naval Weapons
Topic: Propulsion less torpedo
Replies: 8
Views: 566

Re: Propulsion less torpedo

Hi:

No Byron, this "torpedo" was apparently used in about 1885.

Regards
by marcelo_malara
Fri Apr 03, 2020 5:23 pm
Forum: Bismarck General Discussion
Topic: Wind Behavior: 0400 - 0600
Replies: 35
Views: 1828

Re: Wind Behavior: 0400 - 0600

Hi guys. I used an excel I have done once with the geostrophic wind formula. Data: -distance between London and the Orkneys 950 km -isobar passing by the Orkneys 996 mb -isobar passing by the Thames 1011 mb -pressure diff 15 mb https://i.postimg.cc/wMPhhQyS/Untitled.png Result 26 kt. The geostrophic...
by marcelo_malara
Fri Apr 03, 2020 3:44 am
Forum: Bismarck General Discussion
Topic: Wind Behavior: 0400 - 0600
Replies: 35
Views: 1828

Re: Wind Behavior: 0400 - 0600

Can you guys find wind data for that day in the UK? I can´t get any. I would like to see how these isobars spacing translates into wind.

Regards
by marcelo_malara
Fri Apr 03, 2020 3:41 am
Forum: Bismarck General Discussion
Topic: Wind Behavior: 0400 - 0600
Replies: 35
Views: 1828

Re: Wind Behavior: 0400 - 0600

That´s good data, quiet agree with the charts, we can disregard Suffolk´s, may be the barometer was not correctly calibrated.
by marcelo_malara
Fri Apr 03, 2020 3:25 am
Forum: Bismarck General Discussion
Topic: Wind Behavior: 0400 - 0600
Replies: 35
Views: 1828

Re: Wind Behavior: 0400 - 0600

Another synoptic chart:

Image
by marcelo_malara
Fri Apr 03, 2020 3:23 am
Forum: Naval Weapons
Topic: Propulsion less torpedo
Replies: 8
Views: 566

Re: Propulsion less torpedo

Mmmm....I don´t quiet agree. In the mentioned site there is a picture of a launching, the "torpedo" was launched almost horizontally, question would be how far would the bare inertia take the torpedo before it goes to the bottom or comes to the surface, according to if it is hydrostatically positive...
by marcelo_malara
Fri Apr 03, 2020 3:09 am
Forum: Bismarck General Discussion
Topic: Wind Behavior: 0400 - 0600
Replies: 35
Views: 1828

Re: Wind Behavior: 0400 - 0600

To find true wind you have to re arrange the formula:

relative wind + ship movement = true wind