TigaWave
Well-Known Member
too many props?
- Thread starter TigaWave
- Start date
[2068]
...
Same number as I have!
Just that his look a bit pointier (it's a technical term).
Just that his look a bit pointier (it's a technical term).
Whitelighter
Well-Known Member
That looks like the arse end of a fountain 48
Mmmmmmmm - surface drives...
Mmmmmmmm - surface drives...
DoubleVision
Well-Known Member
I have 5--if you include the bow thruster /forums/images/graemlins/laugh.gif Just replaced the bloody lot too! New stainless C6`s for the drives and a new thruster prop cos the old one fell orft.
MRC
Well-Known Member
thats bigger than 48ft... looks like 80ft ++
TigaWave
Well-Known Member
OK Shafts! must be busy in the engine room
epervier
Well-Known Member
obviously I've arrived too late, or I need to go to spec savers,
where's the image?
where's the image?
jfm
Well-Known Member
Sorry to get engineery but does anyone know what those drives are? They're not arnesons
They have no flexible joint so the shaft angle seems fixed, and boat trimming must be done by the huge trim tabs.
What are the 4 vertical pipes/struts going to the underside of the swim platform for? The outer two support the aft shaft bearing - you can see the massive bracket bolted to the transom at the top. But they also have flaps and then outlets just in front of the props - I think they're also exhausts. The inner two vertical pipes are probably exhuasts too (they don't serve to support the aft shaft bearing cos that is done by lower big brackets bolted to the transom
It seems a bit odd to fit fixed shaft angles when you could have had articulated arnesons?
Boat is bigger than 48 - I'd agree the 80foot estimate
They have no flexible joint so the shaft angle seems fixed, and boat trimming must be done by the huge trim tabs.
What are the 4 vertical pipes/struts going to the underside of the swim platform for? The outer two support the aft shaft bearing - you can see the massive bracket bolted to the transom at the top. But they also have flaps and then outlets just in front of the props - I think they're also exhausts. The inner two vertical pipes are probably exhuasts too (they don't serve to support the aft shaft bearing cos that is done by lower big brackets bolted to the transom
It seems a bit odd to fit fixed shaft angles when you could have had articulated arnesons?
Boat is bigger than 48 - I'd agree the 80foot estimate
me2
Well-Known Member
This is it www.apolloduck.com/feature.phtml?id=100670 if so its 62 foot
benjenbav
Well-Known Member
I think they're like this:
and the big struts lift the units up and down. The bearing housing just doesn't look like it has any articulation.
and the big struts lift the units up and down. The bearing housing just doesn't look like it has any articulation.
jfm
Well-Known Member
Ah thanks, that's the boat. The 62 footer porpoises a lot
benjenbav
Well-Known Member
Actually, I think my last comment is complete bolx.
jfm
Well-Known Member
i cant see your pic (office firewall blocked) but those vertical props are not up downers i dont think
Whitelighter
Well-Known Member
Sorry yes, the Fountain 48 is only three engines /forums/images/graemlins/blush.gif
Scarron
Well-Known Member
No doubt someone more in the know will put straight if I am wrong but this my understanding of how it works - the ducts in front of the props are switchable exhaust outlets used to get the boat up on the plane.
When it is running at displacement speed the props are fully immersed and the gearing used is such that the props can't spin up against the water resistance. So, you divert the exhaust from their normal straight thru outlets down through the outlets in front of the props and give it a load of beano, this aerates the water the props are running in, allowing them to slip enuf that the engines get up on their cams/turbos. Then with a bit of luck and a fair wind you can build up sufficient boat speed [about 30- 40 knots] to allow the prop gearing to chime in. Next thing you know you are whizzing along at 80+ knots with just the bottom half of the props in the water.
Well that's my theory anyway.
Paul
When it is running at displacement speed the props are fully immersed and the gearing used is such that the props can't spin up against the water resistance. So, you divert the exhaust from their normal straight thru outlets down through the outlets in front of the props and give it a load of beano, this aerates the water the props are running in, allowing them to slip enuf that the engines get up on their cams/turbos. Then with a bit of luck and a fair wind you can build up sufficient boat speed [about 30- 40 knots] to allow the prop gearing to chime in. Next thing you know you are whizzing along at 80+ knots with just the bottom half of the props in the water.
Well that's my theory anyway.
Paul
Scarron
Well-Known Member
BTW, the shafts are fixed - you trim the boat with a combination of HUGE trim tabs and bow tanks that pick up / dump seawater. Steering with those big sharp rudders.
You can see most of this on 'Red FPT' Fabio Buzzi's Cowes Torquay winner from this year. It also has the exhaust ducted down the rear face of the rudders, not sure why- mebbe to reduce the low pressure area behind them?
You can see most of this on 'Red FPT' Fabio Buzzi's Cowes Torquay winner from this year. It also has the exhaust ducted down the rear face of the rudders, not sure why- mebbe to reduce the low pressure area behind them?
jfm
Well-Known Member
Thanks scarron - that`sounds the perfect explanation. The vertical doofers are definitely exhausts, and the aeration of the water to make the props slip sounds dead right
Separately, ref your reply to jrb, the pic he posted was of articulated surface drives (arnesons I suspect) not fixed. You can see there are 3 hydraulics for up/down trim and 2 for steering (the centre drive is steered by tie bars, not its own hydraulics). They still seem to have exhaust temporary divert ducts, however. And trim tabs. The customer must have said "just fit everything"
Separately, ref your reply to jrb, the pic he posted was of articulated surface drives (arnesons I suspect) not fixed. You can see there are 3 hydraulics for up/down trim and 2 for steering (the centre drive is steered by tie bars, not its own hydraulics). They still seem to have exhaust temporary divert ducts, however. And trim tabs. The customer must have said "just fit everything"