UK Defence Forum

shark bait wrote:

Dave wrote:27 knots should be enough to do it, wouldn’t it?

It would, but have they ever been clocked at that speed? On paper they look a little too underpowerd to reach the high 20's. The invincible class has far more power (3-4 times more) than the Tide class to supposedly reach similar speeds.

You’d think the Royal Navy might just have an idea of the top speed of their ships .

The Royal Fleet Auxiliary vessel is one of four built to refuel the new Queen Elizabeth class aircraft carriers and her task group when at sea.

Measuring just over 200 meters in length and with a top speed of 27 knots, RFA Tidespring is a welcome addition to the fleet.

https://www.royalnavy.mod.uk/news-and-l ... inster-ras

maybe, but on the other hand;

• BMT list the speed @ 18+ knots
• Wartsila @ 19 knots
• Norwegian Navy @ 18 knots.
• DE&S @ 15+ knots

That makes the RN the odd one out, so I don't believe them.

Yes, but the other nations do not have the special "low friction" paint.

shark bait wrote:maybe, but on the other hand;

• BMT list the speed @ 18+ knots
• Wartsila @ 19 knots
• Norwegian Navy @ 18 knots.

That makes the RN the odd one out, so I don't believe them.

I’d be more inclined to believe the organisation that is actually operating them. The RN doesn’t gain anything by making false claims.

They actually state 27+ knots on the home page of RFA Tidespring.

https://www.royalnavy.mod.uk/our-organi ... tidespring

Dave wrote: They actually state 27+ knots on the home page of RFA Tidespring.

https://www.royalnavy.mod.uk/our-organi ... tidespring

The Points were also bought "with two different speeds"... and the ones with bigger engines sold off as uneconomical as we won't be going anywhere in a hurry (... anymore ).

There's no evidence the Tides have been fitted with an uprated power plant.

The DE&S site states 26.8 knots.

If true that would be welcome as the best place for your support ships are with those they are supporting, which means they need to keep up. Their are no front lines at sea so you cant send your support ships somewhere "safe" without escorts, which we haven't got enough of anyway.

From the DE&S magazine.;

The tankers, which can travel at speeds in excess of 15 knots

https://www.contracts.mod.uk/wp-content ... 18-Web.pdf


Can anyone point to a source confirming any tanker travelling at 27+ knots ?
Can anyone point to a source that explains how a massive ship can travel at 27+ knots with only 21MW of installed power?

The invincible class required four times the power to travel that fast.
The smaller T26 requires twice the power to travel that fast.

I'd expect that there's a significant difference in maximum speed between an empty Tide and a fully loaded one.

I'm not sure.

Speed is not a function of weight, it is a function of drag. An empty ship may sit higher, and therefore less drag, but sitting higher causes other fluid dynamics issues.

shark bait wrote:Can anyone point to a source confirming any tanker travelling at 27+ knots ?
Can anyone point to a source that explains how a massive ship can travel at 27+ knots with only 21MW of installed power?

The invincible class required four times the power to travel that fast.
The smaller T26 requires twice the power to travel that fast.

I think its worth noting that the Wave Class can only do 20 knots with 18MW of power

And to get an AOR to hit 25+ knots you have to do this sort of crazy....which even the USN struggles to afford.

https://en.wikipedia.org/wiki/Supply-cl ... pport_ship

https://en.wikipedia.org/wiki/Sacrament ... pport_ship

Some good examples from similar size naval auxiliaries above.

The Americans get 25 knots from 80 MW
The Wave class get 20 knots from 18 MW

That is the perfect demonstration of how hard it is to make big ships go fast. Looking at all these figures there is clearly something wrong about the Tide class figures.

shark bait wrote:That is the perfect demonstration of how hard it is to make big ships go fast. Looking at all these figures there is clearly something wrong about the Tide class figures.

I think the fact that HNoMS Maud, a sister ship of the Tides (admittedly a smaller one, but using the same AEGIR hull form from BMT that the Tides use), with similar machinery achieves 18 knots should give everyone pause for thought.
The Fort Class AOR's do 20 knots. The Bay Class do 18 knots. Pretty much every RFA vessel's max speed is c18-20 knots. It's clearly an organisational choice to have an efficient cruising speed with commercial standard machinery. It's the same for every auxiliary in any Navy on earth.
e.g.
The USNS Henry Kaiser Class are roughly the same weight as the Tide Class, and have a combined 25MW powerplant. To all intents and purposes they are the USNS analogue to the Tide Class. Their top speed is 20 knots, there just isn't some secret sauce that will get the Tide Class to 27 knots. That is unless the RFA has secreted away a couple of MT30 GT's in the design....

https://en.wikipedia.org/wiki/Henry_J._ ... ment_oiler

Scimitar54 wrote:Yes, but the other nations do not have the special "low friction" paint.

Low friction paint can add 2-3 knots, but not 7 knots...

Classified

Found some good shots of them at work with RFA Fort Victoria on Twitter:

(@HMSQNLZ) 10th September 2019

How low can you go @RFATideforce? #WESTLANT19 tanker makes like a submarine as the UK Carrier Strike Group ploughs through the cool Atlantic.

Not as good as the image at the top of page 28 with A136's bow under water

from ""

RFA Tidespring (with Phalanx now installed) seen from RRS Sir David Attenborough in the wet basin at CammellLaird Birkenhead

I'm afraid the forward CIWS fire arc does not cover well for surface threats, because of the bulwark?

donald_of_tokyo wrote:from ""

RFA Tidespring (with Phalanx now installed) seen from RRS Sir David Attenborough in the wet basin at CammellLaird Birkenhead

I'm afraid the forward CIWS fire arc does not cover well for surface threats, because of the bulwark?

How odd, it's almost as if its primary role was for AAW.

However the 30mm will up the surface stuff