Hello, please can you give me some guidance about the relative strengths of this design.

From what i have read they seem to be rather poorly regarded cpmpared to the 2s and 4s.  Not a quick planing boat and not great on restricted waters or rivers.

What is the reality?

Thank you in advance. 

"This design was in concept somewhere between the Smokers Satisfaction and the Summer Wine. Essentially the Smokers was well known for its ability to carry weight, and the Summer Wine was a design for lightweights. The Wine's classy performance caused the well-built fraternity to pester Phil Morrison for a Wine that would carry weight. NSM stands for “New Smoking Material”.

This boat was an instant success when introduced in 1978, and soon became the most popular design, particularly after the GRP version appeared in 1980, some 35 being built. The NSM2 derivative quickly replaced it in the early eighties and it must be said too, that the rig was evolving rapidly at this time, and since 1980 boats have had a low bow tank which gives more hull stiffness to cope with the increasing loads placed upon it by the modern rigs.

The NSM's stability makes it suitable for those regularly racing in strong winds or those converting from more stable boats such as GP14's who find other Merlin designs a bit tippy."
 
You have probably read that already, but the key here is the bit on the low tank and the rig. The low bow tank made a huge difference to the way that boats were rigged and sailed and only about half of the NSM 1s had them. Most of those were the foam sandwich ones. The NSM II had arrived by then and was considered a definite step forward, though NSM 1s continued to be built for some time.
 
Inland looking at the results suggests that NSMs were able to hold their own for many years, but as a championship contender they were considered outclassed very quickly. 
 
I think the thing is that everything the NSM did, the NSM II did better.The I planed well in breeze, but the II was faster again. The I would carry some weight, but the II carried more. The list goes on! 
 

Chris, thanks for the note.  Yes I recognise some of the text from my trawling of this very informative forum.
 
We are a lightweight crew likely to mostly river/inland sail so I'm getting the impression that the design might not be for us - also the one we are looking at doesn't have a low bow tank.

On restricted water it'd be absolutely fine, though a summer wine might suit your weight better if it's windy - an NSM i or II will tack better though.

The other point is that most low tank boats were upgraded to raking rigs. You can't really do that effectively with a high rank hull and if you do the hull isn't stiff enough without reinforcement.

An nsm II with a raking rig might well be more up your street even though on paper you aren't heavy enough for it.

The other thing to look for as well as low bow tank is what sticks the boat together.  West epoxy came in (I think) around 1980 so late NSM1's will probably have stronger joints as well as low bow tank.   There were some  tweaks made to by builders of NSM 1 design later on so bear in mind that some late 1's may have a 'hint of 11' .