1/84 iffy USS Tucumcari

[scooter]

At around 9 minutes, you can see Tucumari foilborne, and waterjets running
If the embedded video doesn't work search "Foilborne (1972)"

[Captain Canada]

That's alot more water out of the jet than I was thinking ! Wow. Easy to see now how she could stay foilborne. Cheers guys.

[PR19_Kit]

That's terrific Scooter, thanks so much for linking it. 

Our Navy's BH7 hovercraft appears in the vid as well, at around 9:25 or so, while exercising with the Tucumcari! 

[Andrew Gorman]

Thank you for that video!  Nice soundtrack too.

[Joe CalPo]

That's a cool video.  I've build some really small hydrofoils for this site, modified Pegaguses.  Pegasi?

[scooter]

Pegasi?

Is an acceptable plural of Pegasus.  It's a shame the Navy didn't have more.  But then again, they're very niche and not exactly cost effective.

[Weaver]

The Italians built seven Sparviero class hydrofoils that were like a shorter version of the Pegasus, and the Japanese built three boats with the same hull and propulsion system but different weapons. In both cases planned orders were cut short and the boats are all out of service now.

The Soviets had several classes of hydrofoils of the simpler, surface-piercing type, as patrol boats, torpedo boats and missile boats. Some of them are still in service. They also built several classes of passenger-carrying hydrofoils as river ferries.

[PR19_Kit]

The Sparvieros were strange looking things, so short they looked as if only part of them had been extruded from the mould!



Surface piercing hydrofoils are really quite common, there were even some running on the Southampton - Cowes route for a few years. They were built by Rodriguez or Supramar, I can't remember which exactly, but they rode very roughly, even in the calm waters of the Solent. They had a much harder ride than the competing SRN5 and 6 hovercraft on the Southsea - Ryde route a few miles to the east.

[Weaver]

Surface piercing hydrofoils are really quite common, there were even some running on the Southampton - Cowes route for a few years. They were built by Rodriguez or Supramar, I can't remember which exactly, but they rode very roughly, even in the calm waters of the Solent. They had a much harder ride than the competing SRN5 and 6 hovercraft on the Southsea - Ryde route a few miles to the east.

Presumably that's because the surface-piercing foils are still affected by every wave just like a hull, but being shorter than a hull, the wave impact comes all at once instead of being spread out. They're fast but they're not smooth.

It's interesting that the Italians seemed happy with a 76mm gun on Sparvieros while the USN decided, retrospectively, that it was OTT on the Pegasi. It's not like the Italians  didn't have choice due to "buying Italian" either: they make a fantastic range of naval guns and could easily have fitted, say, a Breda-Bofors twin 40mm that would be about 3 tons lighter and every bit as devastating to another small craft.

[Rick Lowe]

a Breda-Bofors twin 40mm that would be about 3 tons lighter and every bit as devastating to another small craft.

And aircraft. 

[Old Wombat]

But the OTO-Melara (Otobreda) 76mm system was also very good against other small ships & aircraft - & had a longer range. 

[Weaver]

But the OTO-Melara (Otobreda) 76mm system was also very good against other small ships & aircraft - & had a longer range. 

Longer range but a much lower rate of fire. It's an interesting trade-off. In the 1970s, when these hydrofoils were in fashion, the version of the 76mm than available put out 85rpm. The Breda Bofors Twin 40L70 Compact mount of the day put out 600rpm. Given the limitations of 1970s fire control and the fact that small craft are relatively poor gunnery platforms, it could be argued that the greater statistical chance of scoring hits with the Twin 40 was of more value than the (effectively unusable) range advantage of the 76mm, especially since a hydrofoil could use it's great speed to close the range quickly.

Having said that, the 76/62 Compact and it's successors unquestionably were, and mostly still are, a highly favoured fit for small combatants, often in combination with the Twin 40L70 at the stern. Of course, improvements to both gun systems have massively increased their capability*, and modern fire-control and ammo technology can make either terrifiyingly accurate, so nowadays, perhaps, the 76/62's longer range and higher payload are at an advantage. It's certainly interesting that the Italian Navy, who championed AAA though the "all missiles" era (correctly in my view) moved from using the Twin 40/L70 to the 76mm Super Rapido mount in the mid 1980s.

On the other hand, it's also interesting that the Bofors 57/70 seems to be having a revival, with both the USN and the RN (both former 76/62 users) opting for it. Maybe that's the ideal compromise between RoF, range and payload?


*Current Rates of Fire are:
76mm Super Rapido: 120rpm (burst)
40mm Twin Fast Forty: 900rpm
SAK-57 Mk.3: 220rpm

[Rick Lowe]

The Sparvieros were strange looking things, so short they looked as if only part of them had been extruded from the mould!

Maybe they were made in the same factories as the Fairmiles?
(The old saw being that they were "Built by the mile and cut off as required."    )

[jcf]

The Jetfoil literally flies through the water, all control is done with moveable control surfaces
on the trailing edge of the foils. The same surfaces function as flaps, elevators and ailerons
depending on what is required. The vessel banks as it turns for the same reason that an
airplane does. The fwd strut also has a small degree of movement either side of the centreline
of the vessel.

Yes, I figured that out from what I've read already.

When I 'rode/flew' aboard the Jetfoil to Ostend and back it felt EXACTLY like the APT-E did in a turn in that the ship/boat hesitated just a short while as the yaw came on and the it started to roll, catching up with itself and remaining stable during the turn before reverting to 'level flight' with the same hesitation.

We tried to eliminate that hesitation on the train by adding in some forward gain in the control loop and found that passengers didn't kike the higher vertical acceleration as it started to tilt faster, so we went back to the original system.

The tilting train example is irrelevant to the operation of a submerged foil hydrofoil. The train is operating on a fixed track with curves of fixed radius. When foilborne the submerged foil craft is operating freely at the interface of two fluids, the water and the atmosphere, and is effected by both hydro and aerodynamic forces. It's not on rails.

[PR19_Kit]

The tilting train example is irrelevant to the operation of a submerged foil hydrofoil. The train is operating on a fixed track with curves of fixed radius. When foilborne the submerged foil craft is operating freely at the interface of two fluids, the water and the atmosphere, and is effected by both hydro and aerodynamic forces. It's not on rails.

Not true I'm afraid.

Neither the radius nor the cant of the track is a constant and are always prone to variations and good tilt systems will respond to those inputs, and adjust the angle accordingly. They also respond to inputs from point and crossing work for the same reason.

SOME tilt system are prediction driven, and are run by onboard software 'maps' of the track, but they never give as good a ride as a proper live system.