Opening 2 Diamonds

[JLilly]

Statistical considerations:

 

By my calculations, you get a Flannery distribution 2.8% of the time (5-7 hearts, 4+ spades, with # hearts > # spades).

You get a 6-card diamond suit 4.2% of the time.

 

The probability of 11-15 HCP is 34.0%

The probability of 5-11 HCP is 56.4%

 

There's nonzero correlation between distribution and HCPs (extreme example: if you know that you have a 12-1-0-0 distribution; the probability of having 15 HCP is zero), but, naively multiplying the probabilities, you get a Flannery opener .028*.340 = 0.966% of the time, and a weak 2D .042*.564 = 2.37% of the time. So the rewards of Flannery have to be about two-and-a-half times as great as the rewards of weak-2D for it to be superior.

 

Especially at IMPs, I can see Flannery coming out on top, since it's at once constructive and preemptive w/r/t making game. If your side has the points for game, you'll find the right contract, and if you lack a fit and 3NT is a no-go, you can easily stop in 3M. If opps have the points for game, you've eaten up half their bidding space. A weak 2D is unlikely to lead to a game.

 

On the other hand, in a 36-hand tournament, your partnership will probably never use 2D Flannery, but you're more likely than not to use 2D weak 6-card suit. 2D as weak 6-card suit is much more likely to block their game.

[awm]

A couple points on the frequency:

 

1. Flannery can actually help you when you open 1♥ also. You can bypass the 1♠ response on most (all?) four-card holdings, which can conceal declarer's distribution or help you find the right partial (say responder has a 4-6 hand). It can also help you find 5-3 fits (presumably opener will always raise on three after 1♥-1♠ since he won't have four without a lot of extras).

 

2. Most people will open a weak 2♦ on a five-card suit at least sometimes (it depends on shape and suit quality and vulnerability and position) but the assumption of six-card suit is likely to be overly restrictive.

[mycroft]

The Flannery players would say that yes, the rewards from playing it *are* 2 to 2- times more than were they playing it as natural and weak. In fact, first they say "we've never had a bad board when we open Flannery"; then they talk about all the advantages they get when they open 1♥ (especially now that Kaplan Inversion is illegal - yeah, since 199mumble, but still).

 

Those that don't play Flannery acknowledge all those benefits, but you are correct, the frequency is pretty low, and I wonder how much worse they are when they get a 6-card diamond suit and 5-10 high.

[TresAces]

My partner and I open 2 diamonds showing 18 or 19 High Card Points. It has no other meaning and does not describe shape. We alert it as such. The partner responds withi6 point steps to show his./her High Card Point Count. 2H shows 0-6, 2S shows 7-12 and 2NT shows 13+ HCP. The opener uses this information to determine whether to proceed to game or explore slam. The 2H response says proceed with caution, 2S says game pointss are there, 2NT says explore slam. If the responder bids H or S in response to the 2D opener, the opner then bids best suit looking for a fit, or 2NT if no good five card suit. If opener bids 2NT as second bid, responder treats it as though it was an opening NT bid and bids stamen or transfer, or in the case of a very weak hand, passes at the 2NT level. Either partner might have distributional points to add to the HCP already established and push the other partner toward game or slam. I don't know that our system fits any of those named here: Mexican, Flannery, etc.