What do these strakes do?

[kach22i]

http://www.portierramaryaire.com/for...&sd=a&start=45








Aren't they going in the wrong direction?

[kach22i]

Are these also strakes? Or are neither set strakes?

http://www.militaryphotos.net/forums...-Country/page4


http://www.portierramaryaire.com/for...&sd=a&start=30


http://www.duramax-international.com/Recent.asp

[kach22i]

And what the heck are these?

http://www.duramax-international.com/Recent.asp







Some sort of thruster?

Which part of the waterjet is this?
http://www.duramax-international.com/Recent.asp

[Tiny Turnip]

Last ones look like heat exchangers, but no idea on the strakes...

[baeckmo]

Those strakes are probably there to protect the hull in areas susceptible to damage from bumping into jetties or tied along other vessels. You find similar on trawlers, in the area where the fishing gear comes in. Also on a diversity of work boats, like service vessels, tugs et c. .

The hull openings are for what we call grid coolers. Judging from size (hard to tell though since no referrence objects) it might be for airconditioning or stand-by gensets.

[Ol-Paint]

Duramax makes heat exchangers, which is what is behind the grids in the sides of the vessel. The waterjet appears to be a Schottel pump jet (SPJ). The picture is of the foundation for the thruster.
http://es.wikipedia.org/wiki/Patrullero_Fluvial_PAF_III
http://www.schottel.de/eng/r_produkt...uebersicht.htm

Douglas

[kach22i]

Originally Posted by Ol-Paint

Duramax makes heat exchangers, which is what is behind the grids in the sides of the vessel. The waterjet appears to be a Schottel pump jet (SPJ). The picture is of the foundation for the thruster.
http://es.wikipedia.org/wiki/Patrullero_Fluvial_PAF_III
http://www.schottel.de/eng/r_produkt...uebersicht.htm

Douglas

Nice links, from the last one:

An impeller sucks in water from under the hull and forces it into a pump housing.The outlet nozzles are fitted in the bottom plate, making it possible for the jet to be installed in a flat-bottomed hull too.

At the risk of straying my own thread off-topic, why don't we see such pump/fan configurations on air breathers such as aircraft and hovercraft?

Doesn't air act as a fluid in most situations? As in computational fluid dynamics?

[kach22i]

Originally Posted by baeckmo

Those strakes are probably there to protect the hull

That was my guess too, so unless somebody knows better lets go with that.

[Squidly-Diddly]

maybe they some crap they could could only get in that shape or fasten at certain points, thus not optimized water-wise.

[Ol-Paint]

Originally Posted by kach22i

Nice links, from the last one:



At the risk of straying my own thread off-topic, why don't we see such pump/fan configurations on air breathers such as aircraft and hovercraft?

Doesn't air act as a fluid in most situations? As in computational fluid dynamics?

Poor efficiency and a lack of the unique requirements that drive consideration of this type of thruster are why you don't see them on aircraft/hovercraft. Low efficiency means poor power/weight ratios, which make them suboptimal for application on weight critical designs (aircraft/hovercraft). The closest analog to this type of pumpjet I can think of would be the LCAC bow thrusters (puffers), but those aren't self-contained. The system is simply too inefficient to be useful in an aerial application outside of some highly specialized circumstance.

Maybe a super low profile blimp designed for storm sewer inspection or spelunking could make effective use out of this type of propulsor--that would be the kind of highly-specialized requirement needed to force adaption of this type of propulsor (and even that is questionable).

This type of thruster is usually only preferred on marine vessels where (1) azimuthing thrust is desired/required and (2) draft is limited. A side benefit is the compact installation footprint compared to a retractable thruster or inline jet thruster. Where draft is not limited, a drop-down and non-retractable azimuthing thrusters will provide higher thrust for the same engine/motor input power. Where draft is limited, but azimuthing thrust is not needed, a tunnel thruster offers a simpler (less expensive) alternative.

Douglas

[kach22i]

Originally Posted by Ol-Paint

Poor efficiency and a lack of the unique requirements that drive consideration of this type of thruster are why you don't see them on aircraft/hovercraft. Low efficiency means poor power/weight ratios, which make them suboptimal for application on weight critical designs (aircraft/hovercraft).

I think that if we ever had "aircars", or hovercraft operating on dry land near brush, people and other things more often than open water we could see a reason for enclosed and compact thrusters. They might even be more quiet too.

It's always the efficiency thing, which is ironic because once you lift the hull up and operate in a medium 1/100th as dense as water (air) you can get pretty efficient.

concur in both cases.

The well IS for housing a SPJ installation (you´ll find another one on the other side of the vessel).

And the "strakes" are just reinforcements of the hull in high load areas. All Rig supply vessels (AHTS) and modern tugs sport similar structures. They could be executed on the inside of the hull, but that would interfere with the frames and stringers.

Regards
Richard

[kach22i]

Originally Posted by apex1

And the "strakes" are just reinforcements of the hull in high load areas. All Rig supply vessels (AHTS) and modern tugs sport similar structures. They could be executed on the inside of the hull, but that would interfere with the frames and stringers.

So the strakes are dual purpose, both structural to distribute dock and other boat impacts (boarding looking for drugs) and secondly serviceable and expendable upon impact like a automobile bumper.

Correct?

I'm guessing this is one of the larger craft on the river and may indeed push drug running boats aside after capture or capsize them without use of firearms.

EDIT: Buque Nodriza translates into "Parent Ship".

Nodriza translates to; Nurse

Ship hull up against river bank/shore......................notice access door.
http://www.fotosmilitares.org/viewto...st=0&sk=t&sd=a


Inside: same link as above
http://www.fotosmilitares.org/viewto...st=0&sk=t&sd=a


I'm guessing that the diagonal ones work better than the horizontal ones considering tide height rises and different heights of ships being boarded.
http://www.fotosmilitares.org/viewto...1137&start=300

[kach22i]

Nothing new under the sun..........looks to be WWII era.
http://funkoffizier.wordpress.com/ca...allas-navales/

[daiquiri]

I didn't know that river patrol boats need to be of low radar signature type. Thought that mountains, hills and trees are enough to hide them during operations.