Claimed boat speed versus actual.

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PhilipF

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We have a Nimbus 280 'Familia', this powered by a Volvo D3 160HP engine. A brochure claimed that the cruising speed is 16 knots, and a top speed of 20. MBM buyers guide states "speed from" 19 and "speed to" 20 (those figures strike me as daft - what does "from" mean? The speed "from" to me ought to be tickover speed, the lowest speed it will go at the minimum throtttle setting)

Anyway, I've never managed to get remotely near these claimed speeds. The highest ever being 16knots, and that 'speed over ground' - probably with a following tide! With the throttle lever as hard forward as it can be pushed, the engine revs are given as 3500. Yesterday in Poole harbour it was held at a steady 3000 - which I regard as a comfortable running speed, the boat was hardly managing ten knots. It was only placed in the water in early June, it can hardly have picked up enough hull debris to slow it much in just a few months can it?

Philip
 
Ok, ther can be many reason why it slows down. I had a Bayliner 285 last year. When it was shiney new in March it just about got to 30knts. Went out in, erm, juneish after a bit of not much use cos it was, ahem, petrol, and bloody thing hardly got on the plane. ooer, broken it? no, bucket loads of weedy mess slowed it right down. So yes, 5 months and it can be very messy.

Also Nimbybus make quite solid boats methinks? Your 280 must weigh in at 4 tonnes? Mebbe a bit more. A single 130hp engine on a boat of that weight would be, IMHO, a bit underpowered.

I suspect that this is the smallest engine option available? Is this a new boat? MBM may well have tested (infact almost certainly did) with a bigger engine.

All is not lost however. Once your years warranty from VP has expired, you should be able to breath on the lump and turn it into a D3 160, or mebbe even a 190 which will give you more go.

In the mean time, clean your bum and props as a reduction from 16knts to 10knts is almost certainly fouling. You are never going to hit 20knts with that engine, IMHO.
 
Yes it can already been slowed down by growth.

Manufactures figures are nearly never attainable.

Speed in boat terms is to do with, what it will happily cruise at and WOT max speed.

Many boats have a hump about 12-14 knots usually.

Now, you have either the power to get over it or not.

Problem with a boat of 20 knots manufactures speed is, in reality it means about 16 knot's, which with a bit of growth means 12 knots, struggling like hell to get over the hump. (Not all boats have one)

If you look closely at speed, it usually says things like, half fuel tank, no water. Course theres none of your personal junk either.

You sound a bit underpowered. Try getting the hull washed in Cowes.
 
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Also Nimbybus make quite solid boats methinks? Your 280 must weigh in at 4 tonnes? Mebbe a bit more. A single 130hp engine on a boat of that weight would be, IMHO, a bit underpowered.

I suspect that this is the smallest engine option available? Is this a new boat? MBM may well have tested (infact almost certainly did) with a bigger engine.



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The boat actually weighs in at 3,000 kgs. But by the time it's fueled up etc then give it 3,500 odd. So you are not far wrong - or should that be right? /forums/images/graemlins/ooo.gif
 
Hi! I agree completely with previous posts!
But for info, we know someone with a 280 Coupe with a 150 hp TAMD 31P. Lovely boat.
The 'brochure-speed' was 21 knots max...! Ha! But I know our friend's boat with full tanks, and all its cruising gear aboard, plus a few crew members, will achieve about 16 knots max on a clean hull; and has a 'fast cruising' speed of about 12 kts (though comparatively economical; an advantage of a single engine?). Although she's a semi-displacement type, who doesn't have to get over a 'hump', and is very comfortable at any speed in her speed range, any growth on the hull just slows her up, relatively. And our friend tells us she likes a nice polished-up prop at the beginning of the season, too...
Best wishes
 
Sounds pretty fouled up to me too.

Good guess on the weight Jez, 3000 + 430 fuel and water + 200 for peeps and personal gear, safety gear and raft and I bet it gets to over 4 tonnes.

Quite alot for a single 160, would go well with about 230 really.

Still, a nice well made boat. /forums/images/graemlins/cool.gif
 
Fouling does have an enormous effect on speed - I vaguely remember from naval architecture notes many moons ago that even a layer of slime on the bottom can knock 10% off your speed - and as for weed and some shells, it could easily be 20% or more.

Some years ago I was involved with building 27' semi displacement commercial fishing boats here, with a similar hull form to your Nimbus, and weighing about 3.5 tonnes - these boats were equipped with John Deere 4045TFM engines, producing around 135 hp, and they could reach a top speed of about 16 or 17 knots, and could happily cruise at 13 knots.
 
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It was only placed in the water in early June, it can hardly have picked up enough hull debris to slow it much in just a few months can it?


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Er yes it can and almost certainly has!! Clean off the prop and hull and hey presto, your speed will almost certainly re-appear as if by magic!

I bought a Boston Whaler many years ago, had been in the water for just a few months, was supposed to do 30 odd knots but it wouldn't even get on the plane so was over 20kts down on what it should do. A quick clean of the hull and she immediately flew up to 36kts!! I was amazed. It certainly taught me how important it is to keep the hull and sterngear as clean as possible. And as I am a diver I also knosee how quickly unwanted growth can appear. Luckily I am also able to get rid of it without too much effort.
 
> I am confused! Nimbus do not make a 280 Familia with D3?

They 'reintroduced' Familias in 2005 - only a run of 25 I think. We have 'build 23'. There seemed to be three left when we went to Gothenburg in late February this year to have a look at them.

I have very great difficulty in viewing the Nimbus web site via my Netscape browser - seems too "wizzy wizzy" for it to handle. Matter of interest; Nimbus appears to have been one of the very earliest companies to have 'embraced' the web - their first pages went on-line in 1994. From my memory, it was several years before the 'web' really got going. I suppose they want to keep on top of the technology - not a good idea if many like myself are unable to cope with them.

Anyway: Thanks for the replies. Not best pleased if this implies that my boat ought to be lifted out and cleaned off two or three times a year. Would it help to cope with this fouling up if the hull was treated with a high quality paint treatment?

Philip
 
> Where are you getting the speed predictions from?

MBM as stated in my originial quiry for one - top of this thread! There are Nimbus brochures which also state these speeds.

Philip
 
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Would it help to cope with this fouling up if the hull was treated with a high quality paint treatment?

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Yes! /forums/images/graemlins/smile.gif

As already noted, a boat with no or poor anti-fouling will gain fouling at an alarming rate and this has a huge effect on speed; especially when your boat is more 'sturdy' than 'performance'.
 
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But he says his is a D3 - 160 already, not a 130hp version.
Agree totally re the effect of 2-3 months of fouling.

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/forums/images/graemlins/blush.gif Slapped meself on the wrist for not reading properly.
Still, breathing on it to 190hp would be easy and would make a big difference.
 
Generally magazines test boats 'light' ie only partially filled with fuel and water, no cruising gear and clean hull/props.
Bung a dinghy on the back, load it with stores, clothes, spares etc and fill it with fuel and water and you could easily increase the weight by maybe upto a ton which on a boat weighing 3 tons dry is a huge increase. Add some hull and prop fouling and it's no wonder the boat won't get near it's tested top speed
 
Not too dissimilar to the Nimbus, my Fjord 27, with an AD41A, has a calculated speed via PropCalc, in excess of 20 knots. 17 knots is the fastest I have seen, 3800 revs, prop just refurbished and a month back in from being slipped and pressure washed. The A/F is not slippy smooth but has no growth. Trim tabs fitted but not in use.
17 knots small.jpg


OK, sloppy job on the fenders!

Half fuel (120 litres) and pretty much no water. Much faster is, I suspect, hard to manage, although ideas would be welocme:-)
 
"Familia" Thought that was the Model name for the earlier 27's.
D3 160 means you have a fairly recent boat.
My old 27 with a TAMD30 105hp Was supposed to do 20 flat out 16 cruising.
Well My 1994 jobbie cruises at 12/13 at 3200rpm and is fllat out at 16 with the mill turning over at 3550. Can,t get the 3600rpm She's rated at.
Would have thought your boat would get to 18 no prob with a clean bottom. Unless your carrying 5 bods loads of fuel and water and booze and stuff!
If the bum on My old crate is dirty I loose a couple of knots.
There is no noticable "hump" when I progress to an amazing 16 knots.
However tweeking the trim tabs can gain me 2/300 revs depending on conditions and about a knot.
How old is the boat?
Early June till now is plenty of time for the Hull to be crudded up imho.
 
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