Shipbucket

Ships of this type for Naval operations doesn't have bow thrusters. due to the noise.

I thought I saw one on VISBY, and I know the OHP have a retractable one. Either way, I will just remove it. I should have enough maneuverability to get away from the pier with just pumpjets.

The SONAR did look a little far back. Since it will mostly exploit bottom bounce and surface duct propagation I'm not really worried about whats going at the bow.

Here is a good article on SONAR propagation:

http://www.fas.org/man/dod-101/navy/doc ... r_prop.htm

Visby doesn't have one. And you can see that by just looking on pictures: If there is painted and icon in the bow area showing that there is and bowthruster under water then she have one if not... (Every single ship, whatever type shall have those marking)
"Acelanceloet" have probalby best knowledg on that. But I don't think OHP have retractable one:

1. because of the year of design.
2. what the ship is intended to do.
3. space.
4. US Navy would most likely not invest in things that might break at that time period.
5. No hull marking about it.

But if you have seen one, it might have been an OHP that have been upgraded by the US NAVY or sold to an another country and then upgraded.
This is what Visby is about.... you don't need bowthruster when you have pumpjets

As that link you posted show... the sonar need to be mounted more forward. if you want it on the center... you need an sonar that you can drop down a couple of meter bellow water (similar to an towed sonar) but for that to work you can't move.


BTW. you should try to smooth out the under water hull of you'r vessel, now it looks like an displacement boat have had sex with an Visby (planing hull)....

the perry has retractable 'get home' thrusters in the bow, as can be seen on my FFG-7 drawings, heuhen.
still, the only reason why that works for a ship like that is because they are retractable and thus go flush with the hull, and make next to no additional noise.

on a quick glance, that page gives no data about hull noise interference. correct me if I'm wrong.
but, where it is now, the sonar will not be effective in the 60-90 degrees aft (too close to the pumpjets) and 30+ degrees forward. (that is, 30-45 and 15 if you look at half the ship, symmentrical) also, I think the deep point of the bow wave will be very close to the current sonar position.

all in all, if you look at real ships, there is none with the sonar in this position. placement, space, and effectiveness are all less then on the bow or bow-keel position.

_________________
Drawings are credited with J.Scholtens
I ask of you to prove me wrong. Not say I am wrong, but prove it, because then I will have learned something new.
Shipbucket Wiki admin

Im glad we can agree.

At the bottom of the article it demonstrates the active sonar equation. Without a basic understanding of the equation and digital beamforming it would be difficult to explain it.

even so, the article does not mention anything about interference from the hull, only signal loss in the water.

_________________
Drawings are credited with J.Scholtens
I ask of you to prove me wrong. Not say I am wrong, but prove it, because then I will have learned something new.
Shipbucket Wiki admin

This is taken from that same article.
NL = Noise Level. Which is a combination of Ambient Ocean Noise and Own Ship Noise. So explain again how it doesnt mention hull interference? Unless you are talking about the physical structure of the hull? Did you see all the raytrace pictures? Sound bends downwards or more accurately due to the effect of Snell's law sound propagates towards the area of minimum sound velocity. In most areas of the world that is toward the deeper part of the water column.

Also this picture clearly shows a bow thruster on Visby.

http://gcaptain.com/wp-content/uploads/ ... ipment.png

text deleted by meeee.


Edit: I have talked with and friend of me, and YES Visby have bow thruster (something that surprised me), This bow thruster is hided behind doors. But as he was told they are never in use due to noise level and problems with those doors. thus no marking at all.

It came out of the Visby brochure PDF on Kokums website thats why I thought it was credible.

EDIT: Well that explains the mystery!