In my biased opinion , ACOL is one of the worst bidding systems ever devised. Therefore , it comes as a surprise to me that I really like one of their systemic bids. The ACOL 2♦ shows all strong diamond one suiters or two suiters with diamonds as the anchor suit with the strength just under a demand two bid. Standard bidding handles strong diamond hands above the range of a 3♦ rebid to under a 2♣ opener abysmally. The ACOL 2♦ fills the gap nicely that standard bidding can not handle. ♠Ax ♥xx ♦AKQxxxx ♣Kx & similar hands are hopeless to describe with standard methods. 4-4-4-1 with 17-21 HCP’s are very difficult to describe. Hiding 5♦ with a 2NT opener impedes minor suit slam bidding . Strong diamond reverses to a major ( 6-4 or the like ) are no bargain. These problem hands are now all solved with the ACOL 2♦.
Therefore , a 2♦ opener shows a single suited or two suited diamond hand or a balanced 2NT opener with at least 5♦ or a Roman 2♦ with its original range of 17-21. All stronger diamond hands ( 22 HCP + ) are opened with 2♣. I originally thought we could get away with a huge range ( all strong diamond hands ) for these bids but it might cause too much ambiguity.
A 2♦ bid demands a 2♥ waiting bid after which opener describes her hand as a single suit , two suiter , NT hand or Roman. A Roman 2♦ is shown by bidding 2♠ after the 2♥ waiting bid which causes partner to relay to 2NT. Now opener describes her hand by bidding the singleton or jumping in the void.
Conventions are rated by their frequency. This 2♦ ACOL range is just more frequent as Roman 2♦ with 17-21 HCP of course are more frequent than their larger counterparts. The range 18-21 ♦ hands or two suiters are more frequent than their forcing to game counterparts. 2NT openers with 5 diamonds are relatively frequent.
6-4’s are very hard to describe & strong 6-4’s exceptionally so. We now have the following understandings to describe these hand patterns playing the ACOL 2♦.
3♥ 6♦ & 4♥
4♥ 6♦ & 5♥
3♠ 6♦ & 4♠
4♠ 6♦ & 5♠
3♣ 6♦ & 4♣
4♣ 6♦ & 5♣
BJ & I added ACOL 2♦ bids to our natural 2♦ structure & got very good results. Returning game forcing 2♦ bids to the 2♣ structure is no big deal as that is what we are used to. Super strong diamond reverses no longer exist as they are opened 2♦. When we open 1♦ , we almost have forcing 1♣ inferences with 6 card diamond distributional hands that we are under 17 HCP. Almost , but not quite as judgment & the length of the diamond suit are factors. A balanced hand with a 2NT rebid is still opened 1♦. 5 card diamond suits in the 17-20 are still opened at the one level. 2♦ followed by a 2NT rebid shows the 20-21 2NT openers with a 5 card diamond suit.
Those of us who play the ACOL 2♦ with a range of 17-21 have the Roman 2♦ included in that mix. We can not play the Roman 2♦ the “old way” where 2NT was a game force & other bids escaped to a partial. With the duality of the 2♦ involved , 2♥ must always be the first bid by responder. How do we escape to a partial ? We do this by “breaking the relay” . As soon as we hear 2♠ , we know that the hand is a Roman 2♦ , so we are supposed to bid 2NT as a relay. If we break the relay to a suit , we want to play it there unless that is openers stiff. If so , the 2♦ opener bids up the line & we scramble to the best partial. If responder accepts the relay to 2NT , we are on a game force.
♠xxx ♥xxx ♦xxx ♣xxxx 2♦-P-2♥-P
♠AJ10x ♥Axxx ♦xxx ♣xx 2♦-P-2♥-P
In standard bidding , a response shows 6 or more HCP’s & the bidding structure unfolds accordingly. Not so with the Acol 2♦ , as responder may have zero HCP.s & does not get an initial chance to show her suit. Therefore an ACOL 2♦ has to be a special bid based on distribution & not just your normal 5 card ♦ suit with 17 –20 HCP. These hands are still opened at the one level. 2♦ shows the 6th diamond & an outstanding distributional attribute to justify starting the bidding at the 2♦ & skipping bidding steps.
This ACOL bid changes the structure of 1♦-P-1NT as extreme reverses & strong 6 card diamond /club hands no longer exist. We now can play light reverses in these sequences as the stronger 6 card reverses would have been opened 2♦ . Strong diamond one suiters , no longer exist also after a 1NT response. Playing an ACOL 2♦ structure has a nice positive ripple effect in your overall system,