I have just bought my first Merlin and have raced it for the first time today. there was one leg of the course which was dead downwind. Someone watching suggested afterwards that I would have been better off to do this with a couple of reaches with a gybe between, rather than running straight downwind. Is this right?

There's a topic for lots of discussion!

IF you can sail 2 broad reaches with (spinnaker up) with the additional time for a gybe (or two) faster than dead downwind, the answer is "yes".
You pays your money and takes your chances....
I'd suggest that if you don't plane on the dead run, but do on a broad reach (remembering that you're going to be travelling further), go for the broad reaches....
If you have boats in fromt of you, sailing over their wind twice will slow them down as well, but you'll need to be nifty with the gybes!

and now for the next comment:-

Colin

Thanks, so is it all about speed? I used to sail a National 12, and it was a real challenge to keep it upright on a run in any decent breeze/waves. Is a Merlin more stable? What do most people do in a srong breeze?

James,

As I have a foot in either boat.................................

The Merlin is more stable that a Twelve, possibly the best analogy is sitting on a Bar Stool, with a Twelve you fall off after 10 pints, you need an extra 2 to fall off with a Merlin - and Ok I have left myself wide open here!!!!!!!!!!!!!!!!!!!!!!!!!

Wow! I've never seen anyone sail with a foot in 2 boats at once!

I've seen people with one foot in a boat - one on the river bank (for about 25 seconds - before you make your mind up to jump!)

I used to sail Fireflies - same length as a 12, but with a "Death roll" on a dead run (the old swept back rudder didn't help - nor did the round bilge design!).
I think the latest pundits reckon it's faster to sail by the lee rather than dead downwind or very broad reach....

When racing it's how quickly you get round the course, not how fast you go that matters :-)  If "fast boat" = lots of capsizes, then it isn't quicker round the course...
You pays yor money and takes your choices. I think that a Merlin is lots more stable than the Firefly, the spinnaker does make a big difference to the stability - but when I can't keep the boat upright, I've probably made a wrong choice somewhere. 
Lots of practice, try different techniques, watch the experts.
Oh yes, when someone says "you should do xxxx" - invite them to helm & show you. That can be fun - writing as an armchair pundit - I don't like my bluff called.

Colin

I'm not a pundit but....

1.  Don't let the top of the main get in front of the mast.
2.  Use enough centreboard (rarely less than half)
3.  Really concentrate on keeping the boat under the mast.
4.  On a reach, keep the spinnaker pole off the jib stay.
5.  Learn to swim.

It's true that once you have actually got the thing up and pulling properly the boat is a LOT more stable on a run with the spinny up even in pretty extreme conditions, but gybing it and getting it up and down provide plenty of swimming opportunities.  In light winds it can often pay to head up a bit if it either gets the boat onto the plane or helps the spinny to set in a drifter but otherwise you are probably better off just going where the wind is and sailing the shortest course, certainly you won't make the same gains from heading up that a boat with a big assymmetric will.

always go for gybing the angles unless there is not enough wind to get on the plane on the reach, or you are going to gybe away from the shore into to a tide that i going against you, depth of water is always a good one to check before you go reaching past the back of a local boat towards the shore (i wondered why he had a smile on his face!!) as for the swimming practice the more you do at the start the less you end up doing in the end remember you have to go to work on monday what would you love to talk about the death roll the ended up in tears or the great sail you had reaching to the downwind mark !!

I was told its like balancing a broom on your hand - steer to keep the boat under the mast (without going wobbly crazy that is).

I always try to go as low as possible without going by the lee (you notice a real drop in speed then), as the extra speed gained is quite hard to offset against the extra distance gained.  Don't forget that the leg is as tactical as a beat and that good gybing on shifts can really pull you up the fleet quickly.

The less board that you use will help, with speed but not stability, but remember to put it down a bit more for when you gybe to help with stability, and if all else fails to help you get onto the bottom of the boat if it goes wrong!

as the extra speed gained is quite hard to offset against the extra distance gained

This should read against the extra distance sailed when reaching off!!

Must be work getting to me...

I know that (Fireflies again) there were a number of trials carried out - people were experimenting and talking about the results (just not written down!).
The conclusion was that it was actually faster to sail a couple of very broad reaches compared to dead down-wind. The real difficulty - as written - is knowing just how far off the run to sail. Too far and you have to sail so much further that boat speed doesn't matter; too little and you sail further without the increase in boat speed.

In the absence of other factors (shallow water, river banks, trees, motor boats, wind shifts, "dead spots"), we tried to sail the shortest course.
Nowadays, you could go and practice with a small GPS - measure the VMG (Velocity made good) downwind as well as upwind. Which is why the class rules don't allow them

Colin