[gnasher]

ahydra, on Aug 18 2010, 03:34 PM, said:

- 1♣
1♠ 3♦ (jump shows 18-21)
3♥ 4♣ (3♥ is 4SF, 4♣ shows 6cards)

Anybody can construct an auction to 7NT if East doesn't show his spade support. Why would East bid 4♣ rather than 3♠?

[ONEferBRID]

gnasher, on Aug 18 2010, 11:47 AM, said:

Anybody can construct an auction to 7NT if East doesn't show his spade support. 

Here's one.
Responder
♠ AT632
♥ AKQ2
♦ AJ
♣ 43

Opener
♠ KJ8
♥
♦ KQ82
♣ AKQT87

Responder gets a gleam in his eye after the 2D Reverse ( 17+ hcp ) .
With his 18 hcp, he knows slam is there and just decides to check for controls at a low level via Minorwood ( 4C!) -- he would stop in 6NT if a keycard were missing:

-    -1C
1S - 2D
4C! - 5C! ( 5th step = 2 + void in a major ; analogous to 4NT - 5NT! reply )
5D! ( cQ-ask) - 5S ( cQ + sK ; so obviously the VOID is in Hts )
7NT
No need for a 2nd K-ask:

Why? Opener has to have either:
a) the Diam K ( the Diam Q is immaterial ) or
b ) if no Diam K, he has to have the Sp Q for his count .

    Responder knows the Cl suit must be at least 6 cards with the Ht void ( either 3 0 4 6 or 2 0 5 6 because
if he only had 5 cds Cl he would have to have 4 cds Sp : 4 0 4 5 but he didn't immediately raise Sp or he is 2 0 5 6 ).
So he is counting on the Cl suit running ( needs a 3-2 split or the Jack falling and Opener has the Ten or Opener also has the Jack ):

2s, 3h, 2d, 6c ( assuming the dK ) or

3s, 3h, 1d, 6c ( no dK but sQ ).

[Cascade]

gnasher, on Aug 18 2010, 09:05 PM, said:

Cascade, on Aug 13 2010, 05:51 PM, said:

Partner has 17+ hcp or so

Partner typically has 3=1=4=5 for this auction

♠K ♦ KQ ♣ AKQ = 17 hcp will be fairly normal

Do you really need all that for a reverse when you have three-card support? KJx x KQxx AKxxx looks more like a normal minimum to me, and even with KJx x KQxx AQ10xx I might reverse - it looks really heavy for 2♠.

I think you miss my point.

I was not suggesting partner had to have those cards but rather the rest of the auction should be aimed at finding evidence not to bid 7NT rather than specifically getting to some other slam.

A double dummy analysis this morning says that on the condition that partner has three spades, four diamonds and at least five clubs and 16+ hcp that 7NT is a much bigger favourite than 7S. I appreciate that double dummy will overestimate the number of tricks but it still strongly indicates aiming at no trumps rather than a suit contract here.