[RogerPfi]

1♣ - 1♦; 2♦ -

As someone converting from 4 to 5 card majors, this is a serious question. In Acol I know what nearly every natural action means. But is Standard American there are (what I would expect to simple auctions) that leave me lost.

How many clubs does the opener have (or range)?
How many diamonds does the responder have (or range)?
How many diamonds does the opener have (or range)?

Which of the two partners have set HCP limits (and shape limits) on their hands and what are they?

Thanks if you can help.

--
Roger

[mgoetze]

Well, "5 card majors" isn't really much of a standard system, but I expect the following to be the majority view: opener has about 11-15 HCP, 4+ diamonds, and 5+ clubs (possibly 4 clubs if you allow a 1♣ opening with 4-4 in the minors). Responder has 6+ HCP, and 4+ diamonds.

[RogerPfi]

mgoetze, on 2013-August-26, 03:09, said:

Well, "5 card majors" isn't really much of a standard system, but I expect the following to be the majority view: opener has about 11-15 HCP, 4+ diamonds, and 5+ clubs (possibly 4 clubs if you allow a 1♣ opening with 4-4 in the minors). Responder has 6+ HCP, and 4+ diamonds.

Yes, thanks for the reply - I agree this is sound reasoning, BUT isn't there a lot more to be got from that fact that neither player has chosen to bid 1N, which from my new 2/1 book, appears to be "the bid" to make if you can in such situations?

What are the inferences I should be able to draw (assuming these opps were "good") players?

[mgoetze]

RogerPfi, on 2013-August-26, 13:08, said:

Yes, thanks for the reply - I agree this is sound reasoning, BUT isn't there a lot more to be got from that fact that neither player has chosen to bid 1N, which from my new 2/1 book, appears to be "the bid" to make if you can in such situations?

What are the inferences I should be able to draw (assuming these opps were "good") players?

For opener: I do think this should show an unbalanced hand (thus 5+ clubs) even if playing a style where more balanced hands are opened 1♣ then 1♦. 5+ clubs, 4 diamonds is always going to be one of the rarer hand types in your 1♣ opening, so you already have plenty of inferences here.

For responder: this is much more a question of style. Most 2/1 players will play Walsh, which means you are already denying 4-card majors with 1♦ unless you are strong. Some will even bid 1NT on 3343. But there are also world-class pairs who bid up the line, so it's really a matter of partnership agreement.

[awm]

Responder had a reason to bid 1D rather than 1M or some number of notrump. With this in mind, opener should always raise with four card diamond support. This could well be key to reaching diamond slam!

What responder can have depends a little on agreements but some possibilities:

5D/4M in a good hand; the raise lets partner know of the 9-card fit which can be key for slam.

Good balanced hand with 5D; again there may be diamond slam but respinder just bids 3nt over 1nt rebid

Hand which is very weak in the majors and does not want to declare notrump; given opener has at most five (four?) major suit cards you are better off in diamond partial or game

Some hand with 6+D where raising can get you to a light game

Basically, if partner did not want to hear you raise with 4-support he shouldn't have bid the suit.

[fromageGB]

As this is the opponents' bidding, and there have been no alerts, they will have agreements and I don't think you can deduce what they are. Certainly opener will have 4 diamonds, but beyond that I would not like to guess. If they are playing the common idea of opening 1♣ with balanced hands not the right strength for 1NT then opener can easily have a 3343 shape. If responder bids 1♦ rather than a 4 card major (which can be shown later) when he is strong, then both parties can have a 4 card major - 2♦ is not the last call in this case.

This means opener has at least 2 clubs and 4 diamonds, and no 5 card major. Strength could be up to 17. Responder has 4 diamonds and no 5 card major, and is at least a 6 count but unlimited.