Yes, that's the one. No signs of puffer ducts anywhere, and I've travelled aboard them too.

Handwavium? Or MacGuffinism, perhaps... finally, a RW use of the concept! 

Quote from: PR19_Kit on January 08, 2024, 09:27:38 AMYes, that's the one. No singes of puffer ducts anywhere, and I've travelled aboard them too.

Back in 2001 I rode on the earlier AP1-88 hovercraft from the Isle of Wight to Portsmouth and back again. I had a Ticket to Ryde!

Could it be that the puffer jets are under the skirt? 
They could be blowing different pressure at angles to move sideways. The water ballast might play a part too. It looks to me like the rear blades fold across the fan shroud to create a form of reverse thrust.

Autocar gave one a test drive for Xmas 2022 https://www.autocar.co.uk/car-news/features/christmas-road-test-2022-griffon-hoverwork-12000td

Quote from: Nick on January 08, 2024, 10:29:08 AMAutocar gave one a test drive for Xmas 2022 https://www.autocar.co.uk/car-news/features/christmas-road-test-2022-griffon-hoverwork-12000td

They don't mention how it steers at low speeds either.

I'm lucky to have travelled on all of the SRN series apart from the SRN1. The SRN3 was the most impressive, with a toweringly tall cabin once we were inside.    But it was designed to carry a tank IIRC

That looked like a gravity assisted turn to me. Differential thrust on the propellors at the rear would have an effect like stearing a tank, forward with one propellor and reverse with the other?

Also wondering about the vote at the top. Says I can select no more than three options when there are only three options 

Gondor

Quote from: Gondor on January 08, 2024, 11:19:04 AMThat looked like a gravity assisted turn to me. Differential thrust on the propellors at the rear would have an effect like stearing a tank, forward with one propellor and reverse with the other?

I'm pretty sure the rudders that the fans are blowing through are used for steering.

Evidently the ducts and the multi-blade rudder are used to steer the Griffon machines.
The exception is the new stretched, by two meters, 12000TD built for a customer in
Japan which has skirt-fed puffer ducts added for low-speed fine maneuvering. 
You cannot view this attachment.

I can't see any ducts on the 1200TDs on the Solent route.

Quote from: perttime on January 08, 2024, 08:34:15 AM

Quote from: PR19_Kit on January 08, 2024, 07:05:07 AM...
It's not quite clear how the current 1200TD model steer as there's no sign of ducts, puffers, or steering props. 

This?

At least it has rudders next to the fans.

Looks like a combination of rudders and independently reversible-pitch prop blades to me.

If a hovercraft is only used as a ferry between prepared landing areas, it's questionable how much fine maneuvering capability it really needs. As long as it can back off the "concrete beach" and had room to turn around, it should be fine.

Forgive the poor lighting, but here's a sketch I did to illustrate how a modified SR-N1 might look if it served the SAR role. My idea shows a pair of small jets/turbo-props placed in the ducting. They would each be linked via a drive shaft to a large, counter-rotating compressor fan. The exhaust from the engines plus ducted air from the central compressor would feed through the pipes and exit out of nozzles that are able to swivel 360 degrees. Inputs from the pilot would be fed through a control computer and allow for a wide range of movement.

Quote from: PR19_Kit on January 08, 2024, 02:23:05 PMI can't see any ducts on the 1200TDs on the Solent route.

That's because the puffer ducts are unique to the
stretched 12000TD being used in Japan. 

Quote from: Gondor on January 08, 2024, 11:19:04 AMAlso wondering about the vote at the top. Says I can select no more than three options when there are only three options 
Gondor

Maybe someone's being ironic, or they're catering for the indecisive... I don't know, I'm not sure... 

Having watched the Solent 1200TDs do their 180 degree turn on the somewhat cramped beach at the Southsea end of their run numerous times, I'm not convinced that they don't have some sort of puffer jets somewhere.

I might write to Griffon and ask them.

Videos show pretty clearly that all of the maneuvering is being done with the multi-blade
rudders, which given the size of the propellers and ducts, isn't surprising as a lot of air
is being moved. The multi-blade rudder arrangement works very well to vector the flow.
It doesn't need any sort of puffer to spin about on the beach apron.    

Here's a good general video on hovercraft:

Quote from: RAFF-35 on January 08, 2024, 04:06:32 PMForgive the poor lighting, but here's a sketch I did to illustrate how a modified SR-N1 might look if it served the SAR role. My idea shows a pair of small jets/turbo-props placed in the ducting. They would each be linked via a drive shaft to a large, counter-rotating compressor fan. The exhaust from the engines plus ducted air from the central compressor would feed through the pipes and exit out of nozzles that are able to swivel 360 degrees. Inputs from the pilot would be fed through a control computer and allow for a wide range of movement.

If you watch the above video, than at the 12 minute mark you'll see a Canadian hovercraft that uses exactly the type of steering nozzles you suggest. The US Military LCACs also use a pair of these nozzles.