For some mysterious reason in MAF the 1NT and 2NT responses on the 1§ opening bid are not needed for the system.
Just omitting these responses would be too bad. Therefore it is good to realize, that with a 5,5 in the major suits you get the whim to want to inform your partner immediately about this very valuable possession.
After a 1¨ opening we offer also the 2NT response to WHIMS, because here the major suit information is very valuable too. Unfortunately here we cannot do without the 1NT response.
The WHIMS-convention implies that, both NT responses to 1§ and the 2NT response to 1¨, have similar conventional meanings as the openingbids of 1NT and 2NT have in MAF. The 1NT response on 1§ and the 1NT opening are done on the same types of hands.
After a response of:
Het rebid op een 2NT antwoord is een andere biedsituatie als het antwoord op de premptieve 2NT opening. Toch is het wenselijk dat het bieden overeenkomsten vertoont. Anders ontstaan er misverstanden.
Therefore we assume, in both situations, that there will always be a fit in one of the major suits. if need be a 2,5 fit. Further we take care of it, that the longest suit will always be established as trump suit. Then the composition of the opening suit is not very important any more.
Further we suppose, that the responder own at least 8 hcp's besides his two beautiful 5-suiters. His hand is evaluated on atleast 11 hcp's now. So there are at least 22 hcp's together.
These assumptions lead to the fact that commonly a 3-level contract in a major suits has a fair chance to be successful.
The strength of the opening hand and the support in trump suit are primarily determinative for the chances of making the game. Therefore the opener, having 13 hcp's, similar to the 2NT opening, has to do an inviting bid of: 3§/¨, while at the same time showing the trumpsuit of his preference. Else, so if weaker, he should call normally 3©/ª to show a minimum hand.
Now the responder determines, with the knowledge he has gained, on his second turn, what has to happen next in his opinion: play on 3-level, play on 4-level or exchange controls and explore slam.. The latter is done by calling anything except the trumpsuit.
When the opener, or the responder, shows a weak hand through bidding the major suit on 3-level, this call has to be regarded as a limit bid by his partner. It is not out of question that the remaining player has a very strong hand and consequently will call the game contract.
This description seems a bit laborious. What happens however is so smooth and natural, that it's hard to demonstrate this in a diagram. It is very similar to what happens after the 2NT opening bid. The only difference is in the comparitive strength of the two partners. By using common sense the minimum strengths to start the conventions is easily reconstructable.
It's recommended to read the chapter on the 2NT-opening again now. Here a similar story is told in other words.
WHIMS bids only count when they are done in the first response. If different calls have been made before then the bids 1NT and 2NT are commonly real. The 1NT bid denotes usually 6-9, and the 2NT bid usually denotes 10-12 hcp's, always in situations when there is no clear trump suit. Generally speaking 2NT bids are not raised to 3NT. This is only done in situations when the 3NT bidder has much hidden strength. Of course all suits must be stopped.
There are a few exceptions on this rule. This concerns conventions like: Ghestem, Truscott, Diamond Sohl, Jacoby 2NT after a major suit opening bid, the 2NT response or rebid after a 2-level opening bid and probably also in some other conventional situations.