2hp enough?

codprawn · 20 May 2008, 21:44

i was really shocked today - I was watching some yachts going out racing and one of them had a 2hp Tohatsu 2 stroke on the back. The boat was about 24' long and was a lightweight racer with no transom but it was certainly not a dinghy either - there were 4 people on board.

The tiny little outboard pushed the boat along no problem and it easily kept up with all the other yachts going out to sea - all from a silly little 2hp!!!

it was funny watching him stop - he just spun the engine whichever way he wanted to go - marvellous.

Bigmuz7 · 20 May 2008, 22:10

Just shows you how few horses you really need to be better than wind power

... AND have it at your 'beck and call' when reverse is required

BruceB · 20 May 2008, 23:04

I have this argument with all the yotties regularly as they wax lyrical about yacht compared to RIB's
My answer is always that I can go somewhere for the evening/day in a straight line and come back in the time it would take them to get out the bay.
Plus I point the bow where I want to go and go direct rather than have to tack back and forth for 6 x the distance to get where I want to go.
And I don't spend weeks just getting it ready for the three weekends a year I could use it to go somewhere.

codprawn · 20 May 2008, 23:08

Ah but could you take a RIB across the Atlantic or down to the Falklands without refuelling???

Nos4r2 · 20 May 2008, 23:38

Quote:

Originally Posted by codprawn

Ah but could you take a RIB across the Atlantic or down to the Falklands without refuelling???

That's what a Hercules is for

codprawn · 20 May 2008, 23:46

Quote:

Originally Posted by Nos4r2

That's what a Hercules is for

They won't go that far either!!!

Nos4r2 · 21 May 2008, 00:30

Quote:

Originally Posted by codprawn

They won't go that far either!!!

Yeah, but you don't have to refuel the rib...

BruceB · 21 May 2008, 13:25

Quote:

Originally Posted by codprawn

Ah but could you take a RIB across the Atlantic or down to the Falklands without refuelling???

And how many yachts ever go more than a few miles from their mooring, honestly?

codprawn · 21 May 2008, 13:37

Oh there are quite a few. Where ever I have been in the world it's suprising how many British yachts you see.

This is the main reason I didn't buy a yacht. The temptation would be too great to go and pay Luxton or Bogib a visit!!!

eilean mor · 21 May 2008, 15:00

i used a little yam malta o/b - something like a 2.5-3.5 (escapes me now ) on the back of a GK24 (displacement 4000lb ) for a while, and it would use 3L per hour, in the flat, and travel about 4-5kn, so that's now the aux for the destroyer

BruceB · 21 May 2008, 16:51

Quote:

Originally Posted by codprawn

Oh there are quite a few. Where ever I have been in the world it's suprising how many British yachts you see.

I'll rephrase the question. How many yachts as a proportion of the total number go more than a few miles from their mooring more than a couple of times a year. And then only locally rather than crossing the Atlantic or even the channel?
I bet its a very small proportion of the total from any marina I know of.

Locozodiac · 21 May 2008, 18:47

Quote:

Originally Posted by codprawn

Oh there are quite a few. Where ever I have been in the world it's suprising how many British yachts you see.

This is the main reason I didn't buy a yacht. The temptation would be too great to go and pay Luxton or Bogib a visit!!!

Don't think all have departed from UK, you have UK territories like BVI with lots of British yachts cruising the Caribbean too. This small, reliable and insignificant engine, really pushes...

Happy Boating

Pete7 · 21 May 2008, 18:49

Quote:

Originally Posted by eilean mor

i used a little yam malta o/b - something like a 2.5-3.5 (escapes me now ) on the back of a GK24 (displacement 4000lb ) for a while, and it would use 3L per hour, in the flat, and travel about 4-5kn, so that's now the aux for the destroyer

Arr, it don't work like that

Your slippery hulled yacht was built to travel at 5 knots and had a hull shape to provide the minimum resistance at that speed. You rib however is designed to plane. So it has a squared off transom to encourage the water to break away from the hull giving you planing speeds. However your rib at displacement speed is not efficient and that squared off transom creates drag which is why you will need a few more hp to make it move with a little aux. The other thing you need to do is ensure the aux prop is well down below the hull because if the transom blankets the prop it will be very inefficient.

Pete

m chappelow · 21 May 2008, 19:08

my other 18 ft hard displacent type boat will easly move at 5 knots with a 2 hp but when the tide turns or the wind gets up or theres a lumpy sea no chance ,its like with the old seagull engines ,low hp , high thrust propeller, and the engine buzzing away .infact its only last year that a 60 ft long narrow boat passed by on our local canal and they had a seagull on the back pushing a boat weighing tons .. only about 3 knots mind.

codprawn · 21 May 2008, 20:11

Quote:

Originally Posted by Pete7

Arr, it don't work like that

Your slippery hulled yacht was built to travel at 5 knots and had a hull shape to provide the minimum resistance at that speed. You rib however is designed to plane. So it has a squared off transom to encourage the water to break away from the hull giving you planing speeds. However your rib at displacement speed is not efficient and that squared off transom creates drag which is why you will need a few more hp to make it move with a little aux. The other thing you need to do is ensure the aux prop is well down below the hull because if the transom blankets the prop it will be very inefficient.

Pete

Spot on.

codprawn · 21 May 2008, 20:12

Quote:

Originally Posted by m chappelow

my other 18 ft hard displacent type boat will easly move at 5 knots with a 2 hp but when the tide turns or the wind gets up or theres a lumpy sea no chance ,its like with the old seagull engines ,low hp , high thrust propeller, and the engine buzzing away .infact its only last year that a 60 ft long narrow boat passed by on our local canal and they had a seagull on the back pushing a boat weighing tons .. only about 3 knots mind.

I wonder how long they would take to stop though???

rickuk3 · 21 May 2008, 20:35

Quote:

Originally Posted by codprawn

I wonder how long they would take to stop though???

approx 240ft and just under 60 secs !!!

Bigmuz7 · 21 May 2008, 20:53

Quote:

Originally Posted by codprawn

This is the main reason I didn't buy a yacht. The temptation would be too great to go and pay Luxton a visit!!!

He might see you coming though.. and be standing on the beach with his Lee Enfield

Hugh Jardon · 21 May 2008, 22:12

Quote:

Originally Posted by Nos4r2

That's what a Hercules is for

have you ever travelled that far in a herc?

Nos4r2 · 21 May 2008, 22:22

Quote:

Originally Posted by Hugh Jardon

have you ever travelled that far in a herc?

I wasn't suggesting accompanying the boat on one