Prudence and Speed

brucehawsker · 25 April 2006, 14:30

I am intrigued by the issues of how powerful an engine it is safe / prudent / wise even to put on a given hull.

When I bought my Solent, I was advised by the builder that a 150 Opti would be prefect and more than adequate for my needs. True, I was a newbie at the time, but I have taken her to exciting places (yes, I remember Ryde Sands, but don't forget coming back from Brighton or October off the Needles) and have found the engine more than adequate.

Granted, I don't pull water skiers or toys.

I can get 38 knots six up with a full tank of fuel. I can get 45 knots with two people on board and half a tank of fuel. Both averages over two directions so these are real GPS averages.

I use 1.1 lites per nautical mile, and seem to average that almost whatever I do.

Now the Jackeens have a larger engine and essentially a two occasional four seat set up. And oogopach now has an Etec 200 HO; faster still.

In a recent thread the Jackeen's boat was reported at 53 knots, and oogopatch was at 59 knots.

And remember, this is in a 6.5M rib.

Am I missing something or is it 'just' jealousy!!!!

oogopach · 25 April 2006, 14:49

Quote:

Originally Posted by brucehawsker

I am intrigued by the issues of how powerful an engine it is safe / prudent / wise even to put on a given hull.

When I bought my Solent, I was advised by the builder that a 150 Opti would be prefect and more than adequate for my needs. True, I was a newbie at the time, but I have taken her to exciting places (yes, I remember Ryde Sands, but don't forget coming back from Brighton or October off the Needles) and have found the engine more than adequate.

Granted, I don't pull water skiers or toys.

I can get 38 knots six up with a full tank of fuel. I can get 45 knots with two people on board and half a tank of fuel. Both averages over two directions so these are real GPS averages.

I use 1.1 lites per nautical mile, and seem to average that almost whatever I do.

Now the Jackeens have a larger engine and essentially a two occasional four seat set up. And oogopach now has an Etec 200 HO; faster still.

In a recent thread the Jackeen's boat was reported at 53 knots, and oogopatch was at 59 knots.

And remember, this is in a 6.5M rib.

Am I missing something or is it 'just' jealousy!!!!

Bruce,

I think your set up is probably perfect for what you wanted and the advice from Solent was and I think still is right.

My build specification and outline was for a "white knuckle" ride. I was really looking for a fast stable Rib that would get the adrenalin flowing when I wanted or felt the need.

I looked at a number of other boats and hulls, and settled on Solent for a number of reasons.

1) They could build me a boat that could be customised to the HO engine
2) Their Hull was the right one for my personal requirements having tested many.
3) They were prepared to build a boat around large engine rather than other way round.
4) The people were open, honest and professional.

With the higher engine spec comes higher running costs, etc etc etc...

So who has the better faster sexier boat??

That's not the issue. Each of our boats does for us what we want and thats what it's all about surely?

If you want to go for a spin then let me know and I will PM you details.

BogMonster · 25 April 2006, 14:55

I think personally I would avoid a hugely powerful one, at least until I get a lot more experience, on the basis that I would probably get carried away and either kill myself or wreck it (or both)!

If the power is there then the temptation must be to use it

The only serious "pro" thought I have on getting a more powerful motor is that it could run the boat at any given sensible speed with a lot less effort and therefore surely greater reliability. Also that it might be slightly less horribly thirsty at say 30 knots than the one I have at the moment! Best fuel economy on mine seems to be about 18-20kt but that is a bit boring in smooth conditions, however 30kt uses about four times as much fuel....

When I win £38 million on the lottery on the other hand, anything is probable

brucehawsker · 25 April 2006, 16:05

Just to confirm, I am not 'getting at' Solent for poor advice, nor am I 'getting at' oogopach for having a sexier engine. Actually, I am more concerned that others on the forum will be encouraged to over order an engine and kill themselves or someone else.

Don't get me wrong, I love Farfetched and her engine. The hull is just fantastic. Even if the lottery happened I wouldn't change her

simmons0 · 25 April 2006, 18:19

On the other hand we're finding a 30 knots cruising speed a bit slow...

Top's out at 38 knots but being a diesel not supposed to redline it too often

PeterR · 25 April 2006, 18:39

When you are new to ribbing you are given adviceand always air on the side of caution i bought 4 different types of boats with different set ups second hand .I found the dealers always (i think cost came into it) always seem to put smaller engines on.Maybe its good business so the sell another engine later more fitting profit on part exchange.I know countless people who have soon outgrown their original engine.It may be also that a lot of customers are idiots and the dealers are being responsible.You should buy the biggest engine both your pocket and boat can take i did on my last boat and no regrets

codprawn · 25 April 2006, 20:00

A lot depends on the conditions you go out in - if you want really high speeds you may as well stick to a hard boat. Something like a Fletcher or Ring 21 will do 70mph and is FAR cheaper than a new RIB.

RIBs are best in the rough - if 40kts feels slow on a flat calm day it certainly won't feel slow in a Force 7.....

I would normally try to go for the biggest engine option - you can always throttle back and save fuel.

Rogue Wave · 25 April 2006, 20:04

I am in agreement with the Codmeister!

I am feeling the need to buy a Hardboat!

ADS · 25 April 2006, 20:08

Quote:

Originally Posted by Rogue Wave

I am in agreement with the Codmeister!

I am feeling the need to buy a Hardboat!

Got one! Just under 50mph with a 70hp, all newer than year 2000, cost, under £4k. Point me in the direction of a rib that will do that!

FreeTrader · 25 April 2006, 20:18

What is people's average cruising speed. Quick Exit seems comfortable at 35/6 knots doing about 4500 rpm, to break 42 knots we need to be doing 5500 rpm. But I'm finding I just want to go flat out all the time. Is this just newbie enthusiasm?

That's why I've been thinking about changing props etc, to squeeze some extra knots.

The Garfish · 25 April 2006, 20:21

Quote:

Originally Posted by ADS

Point me in the direction

i thort yew woz a jeeograffy stoodent

gArf

ADS · 25 April 2006, 20:25

Quote:

Originally Posted by The Garfish

i thort yew woz a jeeograffy stoodent

gArf

Jimbo · 25 April 2006, 20:41

Quote:

Originally Posted by The Garfish

i thort yew woz a jeeograffy stoodent

gArf

For a Geography GCSE, they give you a brown pencil for land, and a blue one for the sea.

For an a-level they give you a green pencil as well, so that you can "add" to the land.

A degree still only allows you brown, blue, and green colours, but you get to do it on a computer.

ADS · 25 April 2006, 20:45

Quote:

Originally Posted by Jimbo

For a Geography GCSE, they give you a brown pencil for land, and a blue one for the sea.

For an a-level they give you a green pencil as well, so that you can "add" to the land.

A degree still only allows you brown, blue, and green colours, but you get to do it on a computer.

You can hardly talk Jimbo, your course is effectively geography based! But yes, it is mainly colouring in

Alex Brown · 25 April 2006, 20:50

8knots ahead, and then 8knots astern is all you need, both at 700rpm (WOT), 300rpm, hard boat though and it does roll a lot

http://files.ribseadrive.co.uk/8knots.wmv

If I bought a 6.5metre rib that was capable of over 50knots, it would be wasted. Last year, on every trip out, the only time I ever managed top speed was for a few brief moments on the upper estuary. With a 3 or 4 metre swell, I have yet to find it comfortable to maintain anything over 25knots.... I'm sure the boat's good for it, but I bottle out

Saying that though, it's handy when there's a wave taller than you, behind you to be able to push the stick down and stop it depositing itself on the stern of the boat.

-Alex

BogMonster · 25 April 2006, 21:17

Quote:

Originally Posted by FreeTrader

What is people's average cruising speed. Quick Exit seems comfortable at 35/6 knots doing about 4500 rpm, to break 42 knots we need to be doing 5500 rpm. But I'm finding I just want to go flat out all the time. Is this just newbie enthusiasm?

That's why I've been thinking about changing props etc, to squeeze some extra knots.

I had that right up until the first time I filled it up with fuel

Well this is

by most peoples standards on here but I find mine will cruise at 18-20 for best fuel economy and my engine sounds entirely happy up to about 4500 which gives about 28 knots I think, though fuel consumption rockets. 5000 and over and the engine sounds a bit thrashy which is ok in small doses but gets tiring. And then filling it up gets even more tiring... normally I don't cruise for any length of time at more than 4500 and the gauge goes down quick enough at that.

It isn't really worth lots more speed for me as once outside the harbour the number of days when you can even do 30kt is going to be pretty limited due to the South Atlantic having more than a few potholes in

Searider · 25 April 2006, 21:31

High 20s. Maybe 30.
3800 / 4000 rpm

Engine sounds happy.
Ground covered quickly.
1.1 miles per litre.

CJL · 26 April 2006, 22:39

Its interesting reading this.

I've had three RIBS now.
One 6.7 with a 140 which was doing 28 - 30 knots which I found a little slow but it did that through pretty much any weather
A 5.5 with a 150 which was like a rocket ship when it topped out at 53 knots but it was down right dangerous when it was rough or you hit a ripple!

My current boat is a 6m with a 135 and does 43knots, comfortably in a nice weather wide weather window and does a good job of meeting what I want the boat for.

I was worrid when I bought the 6m that I' get bored after the 5.5 but not at all. Its a different beast altogether and just as much fun.

I'v had access to other boats which are very fast and I think its fair to say you can't really enjoy long distance crusing above 50knots cause the forces on your body turn a cruise into an exercise in holding on for grim death!! Its ok for short blasts, not for the whole day!

Chris

ian parkes · 27 April 2006, 00:11

Would be interesting to know how smaller ribs and sibs perform .
I tried my little honda out for the first time at the weekend to see what It will cruise along at loaded with lots of fuel the three of us and camping gear .

OK don't laugh

3 adults and 25L in the fuel tank plus cooler box etc . Its flat out at 18.5 knots , and cruises easily at 15knots with the throttle backed off qiute a bit .. It seems to plane at about 10 knots .
I figure from this that even a bigger engine would be a waste of time although a 20 is stated as the max .
I have yet to test it running light but it feels a lot faster maybe 22 knts

shit i feel like Del Boy here in his plastic pig

ADS · 27 April 2006, 00:21

Quote:

Originally Posted by ian parkes

Would be interesting to know how smaller ribs and sibs perform .
I tried my little honda out for the first time at the weekend to see what It will cruise along at loaded with lots of fuel the three of us and camping gear .

OK don't laugh

3 adults and 25L in the fuel tank plus cooler box etc . Its flat out at 18.5 knots , and cruises easily at 15knots with the throttle backed off qiute a bit .. It seems to plane at about 10 knots .
I figure from this that even a bigger engine would be a waste of time although a 20 is stated as the max .
I have yet to test it running light but it feels a lot faster maybe 22 knts

shit i feel like Del Boy here in his plastic pig

Alot of people on this forum including myself started off with a SIB, and have found that small boats are often more fun than bigger ones. SIBs are very easy to use due to their portability, and low running costs. 18.5knots loaded isn't bad at all, my 4m RIB and 40HP Suzuki 2stroke only did around 25knots and i bet that burned alot more fuel than your Honda!
Once you have caught the bug it won't be long before you buy a RIB of some description.