Nimbus 320 owners - what's good and bad

I would examine very carefully my intended use before committing to Nimbus 320. The huge saloon 270 degrees of glass is not bonded and sits in aluminium or s/s farming, and supports the roof. That's absolutely fine for coastal cruising but is completely unsuited to having a few tons of green water hit it at 10 knots. That's just physics, and this is a strange engineering choice imho by Nimbus. So I wouldn't choose this boat for inter-island Mediterranean use or for UK use say 30 miles+ from land. Perfectly fine for UK coastal use. All imho.
The Aquador has the benefit of the frames for its sliding doors, which adds some strength and stiffness to support the roof when/if hit by green water.
 
SimonD said:
If you're serious about a Nimbus you should be aware that the 310/320 was designed with a single engine. I'm not looking to start a single v twin engine debate, but it does make a difference on the Nimbus. The single engine has a decent amount of room to get round the engine. The prop shaft is supported by the shaft log; the prop sits right behind the rudder and is protected by a substantial skeg that supports the rudder. To fit twin engines (I believe at the request of the UK distributor) some space was taken from the guest cabin and still look like a tight fit. The shafts are supported by cutlass bearings and there are twin rudders behind the props which are not protected. You may or may not be bothered by the differences.

One other thing you should know. The 310/320 was never intended to dry out (even with legs). Again, you may not be bothered by this, but I found drying ability really useful on a previous twin keel boat.
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Good feedback again thank you SimonD. I use to run a single donk (Detroit 650hp) on a boat in NZ, and always felt comfortable as long as well serviced, but I know what you mean. I get the impression the Nimbus is not ideal for a twin engine setup. It’s also a good point you make about not taking the bottom, and had not considered this, though used to this as the Seaward has the same issues.
 
jfm said:
I would examine very carefully my intended use before committing to Nimbus 320. The huge saloon 270 degrees of glass is not bonded and sits in aluminium or s/s farming, and supports the roof. That's absolutely fine for coastal cruising but is completely unsuited to having a few tons of green water hit it at 10 knots. That's just physics, and this is a strange engineering choice imho by Nimbus. So I wouldn't choose this boat for inter-island Mediterranean use or for UK use say 30 miles+ from land. Perfectly fine for UK coastal use. All imho.
The Aquador has the benefit of the frames for its sliding doors, which adds some strength and stiffness to support the roof when/if hit by green water.
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Umm. I beg to differ. If that were the case, why is the Nimbus 320 in Cat B - capable of operating offshore with winds to 40 knots and significant seas to 13 feet? Also, has anyone ever heard of a 320 (or any other similar Nimbus design) having had a roof collapse? Bear in mind there are hundreds of them built over many years. I respectfully suggest you're very much mistaken (IMHO).
 
Happy to agree to disagree.
The B certification means nothing.
Picture below - not much supporting the roof when a ton of water lands and decelerates onto it. Serious classification societies insist (even with bonded windows, let alone unbonded windows a la Nimbus) on thick mullions so that roofs can take a few tonnes of water .
As I say, very good for coastal cruising but I wouldn't want to do say 100nm large fetch/open sea crossing unless very sure of weather.
But I'm happy to disagree and everyone is free to choose what build features they do/don't want in their boats.
 

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jfm said:
Picture below - not much supporting the roof when a ton of water lands and decelerates onto it. Serious classification societies insist (even with bonded windows, let alone unbonded windows a la Nimbus) on thick mullions so that roofs can take a few tonnes of water .
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From observation of the photographs it seems to me the window frames are not supporting anything at all and are just there to carry the glass. Instead the roof structure appears to be a cantilever from the pillars at the rear of the glazed section.
Whether it is all strong enough to take a few tons of water or whether any such boat ca take a few tons of water would be a matter for structural design. However the basic proportions look reasonable from a structural perspective.
By comparison a sports cruiser would have little more than some stainless steel poles and canvas yet folks don't worry about a few tons of water landing on the helm area .
 
Martyn there is no way that the cantilever structure is stiff enough to take a decelerating ton of water without significant load passing to the window frames and glass. I'm not talking about the strength of the cantilever structure; I'm talking about its stiffness. The cantilever needs stiffness, not strength, if no meaningful weight is to be taken by the glass/window frames.
I don't follow your arguments on sports cruisers. Folks are, or at least should be, worried about tons of water landing, and so should avoid that outcome (which is all I'm saying about the Nimbus). Ask Piers of this parish who had a couple of tons of green water come over the bow of his princess v39, with major damage. He has recounted the tale on here.
 
If we are agreeing that no leisure motorboat is specifically designed for a Ton of water landing on it then I agree 100%.
My point about a canvas top sportscruiser is it has negligible resistance to a wave landing over the helm so in that respect the Nimbus is superior.

As far as cantilever structures are concerned the stiffness and deflection under any given load could be evaluated given the dimensional and properties of the structure together with young's modulus for the structural material (GRP in this case presumably) but that can't be calculated from a photograph.
 
Another boat to consider is the ACM 31 Elite that David Morris also has for sale. I looked at getting one of these from France as there are a lot over there, then Brexit hit. They were made by Dufour I think.
Anyway, a really good boat, better looking than the Nimbus IMHO and they have a lovely flared bow. A friend has had one for about eight years now and really rates it, he regularly goes to Scilly in her from Falmouth - about 75 miles. A lovely flat foredeck too which is teak on this one.
I see that this one has twin engines which flies in the face of my earlier post about the disadvantages of twins, but so too does my mate's boat and his handles it all fine.
The big thing is the price: £56 000 for a 2002 boat - £35K less than the Nimbus of the same age and as good a boat in my view.
 
Oooo... a boat fight and OG is always prepared to hold somebody elses coat in these disputes.
You can step on my Blue Suade Shoes but do not diss the boat ? :)

The builders and designers of the Nimbus are not alone in committing this apparently cardinal sin.
ACM are also guilty as charged, M,lud.

However OGs limitations are much lower than that of his boats and should there be the slightest likelyhood of several tons of water being anywhere other than under the boat where it belongs a change of plan would be in order .
Either
A.

or B

Ps.
The picture of the ACM is pre purchase, the boat has several more dings and scratches now.
An observation.
All (my) previous boats were constructed during the brick outhouse era with large chunks of glass fibre structure in place to support the flybridge with a few small gaps called windows.
Without exception all the windows in all the boats leaked like sieves due to flexing of the hull and superstructure ?

The ACM spent the first 20 years of its life going around the Channel Isles and across to France and the logbook notes that on a couple of occassions the previous owner abandoned trips due to rough weather (and ran out of fuel twice . ):eek:
The ACM is the only boat ever owned where the windows do not leak.......Yet ?
Do agree with jfm that the seaworthy catagory would be the last thing that would like to put to the test in real world conditions.
:)

....Quite a few of these in France and Spain at very good prices indeed until Brexit hit the fan, then you needed to add another £17K-20 K in Taxes to get it across Le Manche and into the land of the free.
 
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MartynG said:
If we are agreeing that no leisure motorboat is specifically designed for a Ton of water landing on it then I agree 100%.
My point about a canvas top sportscruiser is it has negligible resistance to a wave landing over the helm so in that respect the Nimbus is superior.

As far as cantilever structures are concerned the stiffness and deflection under any given load could be evaluated given the dimensional and properties of the structure together with young's modulus for the structural material (GRP in this case presumably) but that can't be calculated from a photograph.
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Seriously Martin, plenty of pleasure boats are specifically designed (using finite element analysis) to take a considerable weight of water on the roof of the inside helm, with chunky mullions designed/constructed calculated precisely for that. The boat I have in build now in Italy has precisely that engineering, hence rather fat mullions.

Agree your sportscruiser point, but I don't think we ever disagreed on it.

Your last para is true, but telling me how to suck eggs. All builders who want to solve for this would use FEA. You can of course make plenty of sound conclusions (not calculations, granted) from photographs.

Anyways Nimbus 320 + Aquador 32c are both excellent boats.
 
Greg2 said:
Well I reckon we have it covered on the mullion front! 😁

Not sure SWMBO would be too keen on the ton of water test though 😉

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Decks wide enough to walk on , Stantions that do not flex, decent height combings....two cleats midships ..... no daft davits loading down the stern
Where will it all end ?
Form follows function....the boat designed to perform on the water, quite probably by a Naval Architect, as opposed to a piece of "boat art" for display in a marina and most probably somebody whos last job was designing handbags.
Mind you no room for the compulsory twin SatPhone Domes !
 
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oldgit said:
Decks wide enough to walk on , Stantions that do not flex, decent height combings....two cleats midships ..... no daft davits loading down the stern
Where will it all end ?
Form follows function....the boat designed to perform on the water, quite probably by a Naval Architect, as opposed to a piece of "boat art" for display in a marina and most probably somebody whos last job was designing handbags.
Mind you no room for the compulsory twin SatPhone Domes !
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Think we can manage without the twin SatPhone Domes! 😁
.
 
volvopaul said:
Lovely boat .
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Thanks Paul.

Done a lot of work on her since you looked at the motors. Next phase is underway - engine bay re-furb and some changes that meant it was worth taking them out so they can have a bit of a spruce up too.

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