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9 Card Fit with Jacoby 2NT and Splinters

#1 User is offline   Spock_ 

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Posted 2020-November-04, 03:51

In all the material I have accessed to bid Jacoby 2NT or make a splinter bid you need at least a 9 card major fit. Is this because its advisable to have a 9 card fit to bid slam or is there another reason. You don't seem to need a 9 card fit to bid Blackwood or RKC.
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#2 User is offline   Stephen Tu 

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Posted 2020-November-04, 05:37

9 cd fits play substantially better than 8 cd fits. They can withstand bad breaks better, you can obtain multiple ruffs more easily without creating additional trump losers, more likely to pick up the suit without losers, less susceptible to multiple trump leads killing necessary ruffing tricks. In general you should be more conservative bidding with only 8 cd fits. Promising the 4th cd in support helps opener evaluate.

The other reason, is that if you have only an 8 cd fit in the major, you might have a bigger/better fit in another suit, which you can no longer find (since now your bids are mostly control showing not length showing). Also, if there is a 4-4 fit in another suit and a 5-3 fit in the opened major, in some cases the 4-4 fit plays for another trick as a ruff in either hand can increase the trick count (instead of only in the short hand of the 5-3), or the 5-3 fit can produce a crucial pitch of a loser (or 2 losers) in one of the remaining suits.
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#3 User is offline   mikeh 

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Posted 2020-November-04, 06:47

Adding to what Stephen wrote, and considering only splinters, showing the singleton (or void, but singletons are far more common), does two things, in terms of slam auctions. A splinter assures partner that we will lose only one trick in that suit, or none if partner holds the Ace. The second thing it does is to suggest that our side can score tricks by ruffing losers in the hand with the shortness.

Slam bidding requires both finding out that we have only one loser (or none, if we are considering a grand slam) and that we have good prospects for 12 winners.

Consider AQxxx xxx Axx Kx facing Kxxx x Kxxx AQxx

Even on a trump lead, declarer can concede a heart, win the second trump lead, and arrange to ruff two hearts in dummy.


Consider a dummy with Kxx x Kxxxx AQxx

Now, if they lead trump, if we give up a heart, they lead another trump and we can only score one ruff in dummy (on this imperfectly chosen example, we have some play for slam after that defence, but itís a poor contract)

In addition, and this can be critical in slam decisions, a combined holding of AQxxx opposite Kxx, or any holding where one is missing J109xx or equivalent will lose a trick, due to a 4-1 break roughly 31.5% of the time whereas the same honour holding, with a 9;card fit will rarely lose a trick....losing only to a 4-0 spilt.

Jacoby auctions are a little different, in terms of slam bidding, since they are more commonly bid on sheer power, but of course most Jacoby 2N auctions seek to identify shortness in openerís hand. This identifying what is, in essence, the equivalent of a splinter also allows for assurance about losers in that suit and trick taking through ruffs.

If one has KQxx in trump in dummy, and AJ10xx in hand, and say xxx in a side suit opposite a singleton in declarerís hand, one can surrender a trick in that suit and, after scoring 2 ruffs with the 5 card trumpmsuit, one has scored 6 trump tricks.....4=winners in dummy and two ruffs.

On the other hand, if dummy was KQx and declarer AJ109x, and we score two ruffs in hand, we only get 5 trump tricks in total. The ruffs controlled losers but didnít add a trick. Plus, if we do take those ruffs, we now may lose a trump trick if th3 suit breaks badly


So knowledge of a 9 card fit makes slam bidding possible on weaker combined trump holdings than does knowledge of an 8 card fit.
'one of the great markers of the advance of human kindness is the howls you will hear from the Men of God' Johann Hari
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#4 User is offline   mycroft 

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Posted 2020-November-04, 10:09

And it's not just slam; even direct limit raises are, by agreement, 4 cards; because a shaky game opposite Kxx is a very likely one opposite Kxxx.

The key is that you can show 3-card support later, with a delayed raise; you're not going to *lose* the 5-3 fit because you don't show it on your first call.

And it's not just slam; knowing about the 9-card fit makes it safer to *look for* slam, with more assurance that the 5 level is safe if it turns out that 6 isn't.

Mike's analysis is better than I could ever do as to why this is so.

There is a principle in designing the constructive side of bidding systems that higher bids should show more specific hands. The opponents will preempt you out of space if they can; if you bid 1-4, you've done as good a job of preempting yourself as if the opponents had bid 4. So you would only do that if you can pass enough information with that call that it's worth it. "4-card support, game(or slightly +) values, and a singleton diamond" - that's worth it. Outside that, make a 2/1 and then show spade support, and hopefully you get to cue the diamond shortness below game, or you might find that partner has limited their hand so that you know not to try, or...

1-2NT isn't as drastic, but it still takes up a lot of space, and so it's worth keeping that relatively constrained, as well.

This is one of the places that 2/1 Game Forcing (in whatever context) makes life easier. With more ways to set an immediate game force, there are more sequences available later, knowing partner won't pass. So each of the sequences can be more limited, better defined.
When I go to sea, don't fear for me, Fear For The Storm -- Birdie and the Swansong (tSCoSI)
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