[Nirmalya]

Hello everybody

I got interested in DCB or Spiral scan. I am yet to figure out, playing a NON RELAY precision, how can I use spiral scan particularly when the responder has a void or a singleton?

Also, when the asker has a Q in a suit and the responder shows One Honor, how do we know whether it is Ace or King?

Please pardon my ignorance. I am still trying to understand the total concept.

[mike777]

I have always found spiral scan a mystery.....a great mystery

I hope bbo forum can explain it it in a way even I, a simple soul, can understand.....

[the hog]

You cannot play dcb without playing a relay system. The whole point is that you need to know responder's exact shape.

[Zelandakh]

Hello and welcome to the BBO forums, Nirmalya.

the hog, on 2013-April-12, 02:39, said:

You cannot play dcb without playing a relay system. The whole point is that you need to know responder's exact shape.

That is not quite true. Several systems include spiral scan without full shape being known. It is an optional part of Forum D+ after 1M - 2NT for example.

Spiral scan is commonly played in natural systems after a key card enquiry. You then order the remaining cards - trump queen, side kings, etc and the follow-up bids scan for them in order. For example, if the auction starts 1♠ - 2NT; 3♠ - 4NT; 5♣ (1 or 4), you might play that 5♦ asks for ♠Q, 5♥ asks for ♥K, 5NT for ♦K, 6♣ for ♣K and so on. In response, partner bids the first step without the card asked for and skips an additional step for each additional card held in the sequence.

Denial cue bids can be played in a natural system lower. The advantage of this approach is that the cue bids can be used as a form of asking bid when made by the hand taking control. As an example, the auction begins 1♠ - 2NT; 3♠ as before. Now you could agree 3NT = slam try; 4♣ = serious denial cue bid/asking bid in clubs; 4♦ = serious denial cue bid/asking bid in diamonds, 4♥ = serious denial cue bid/asking bid in hearts. In response to a DCB of this type, partner should bid the trump suit without a control in the suit or bid the next suit up where a control is not held holding a control in the asked suit. If controls are held in all suits then key cards can now be shown or asked for.

If desired, you can also choose to allow the denial cue bids to continue at the 5 level. You can make whatever agreements you like here. Making a further denial cue bid in a suit where you denied a control should probably deny the queen, while skipping the suit would show the queen. For a second cue bid in a suit where a control has been shown, one possibility would be that this shows one of the top 3 honours (or a singleton) while skipping the suit shows 2 (or 3) of the top 3 (or a void); another option that a second cue denies first round control, skipping the suit shows first round control.

What you cannot do is to use DCB or Spiral Scan in a non-relay system without first agreeing a trump suit. And that allows you to figure out whether an ace or king is being shown by using RKCB or its equivalent.

[Nirmalya]

Zelandakh, on 2013-April-12, 03:59, said:

Hello and welcome to the BBO forums, Nirmalya.

If desired, you can also choose to allow the denial cue bids to continue at the 5 level. You can make whatever agreements you like here. Making a further denial cue bid in a suit where you denied a control should probably deny the queen, while skipping the suit would show the queen. For a second cue bid in a suit where a control has been shown, one possibility would be that this shows one of the top 3 honours (or a singleton) while skipping the suit shows 2 (or 3) of the top 3 (or a void); another option that a second cue denies first round control, skipping the suit shows first round control.

What you cannot do is to use DCB or Spiral Scan in a non-relay system without first agreeing a trump suit. And that allows you to figure out whether an ace or king is being shown by using RKCB or its equivalent.

Thanks Zelandakh
I am begining to get a handle on this. Will see how and in what situation we can use this seemingly nice gadget

[hrothgar]

the hog, on 2013-April-12, 02:39, said:

You cannot play dcb without playing a relay system. The whole point is that you need to know responder's exact shape.

Well, you COULD, you just wouldn't want to...

I can't "prove" the following, but I am pretty sure that it holds true.

On average, Denial Cue Bidding seems to be more efficient that traditional Control Asking Bids.
However, the improvement in efficiency comes about because you have detailed knowledge about shape.
(Scanning order is important)

You could, in theory, decide that you will always scan the trump suit first, and then resolve suits in order S --> H --> D --> C
Furthermore, you'll inflate your control count for singletons and voids.

I think it would be a god awful system, but technically it would be DCB...

[the hog]

Mike, there are a number of methods; the one we used most recently was:





DCBs occur after cont. asks & ask for the location of hons.

Only look for the hons. asked. You look at suits in their length order - look at the longest first, then at the second longest, then at the third longest etc. If 2 suits are of equal length, look at the higher ranking first.

Two separate schemes are used, 1). with a singleton or void and 2). with no singleton

Only show the honors partner asked for, that is if he asked for A and K, only show those.

You can ask for A & K controls or A, K & Q controls with either scheme.

1 step ask for C1 controls, 2 steps for C2 controls.



1). With a st. or void:

step 1 = all in 1 or something in all.

if it is obvious, continue, otherwise

1 = something in all.

2 = all in suit 1.

3 = all in suit 2.

4 = all in suit 3.



step 2 = all in 1 & 2.

step 3 = all in 1 & 3.

step 3 = all in 2 & 3.



1 = longest, 2 = next longest, 3 = shortest.

After this, look for next hon. down.

After you have shown the hons asked for, relayer might ask again. If he asked for C2

controls, you should now show Qs, BUT use scheme 2, ie. look at suits in length order.

Also look at your singleton. For the singleton, stop with an honor and by- pass without one ( the opposite of usual practice)





2).With no st. or void:

Examine suits in length order. If suits are of equal length, look at the higher ranking first. To stop on suits of 4 = cards shows 0 or 3 of the top 4 hons. To by pass a suit shows an hon.

[Siegmund]

Quote

You could, in theory, decide that you will always scan the trump suit first, and then resolve suits in order S --> H --> D --> C

If you aren't going to resolve shape first and scan in order of importance, there really is no good reason not to simply scan them in their natural order and play some souped-up type of natural cuebidding. Sweep cues are highly effective, in the hands of a pair that pays attention to all the inferences.

But they too - and standard cuebids for that matter - work a lot better if you know about singletons before you start cuebidding, even if you don't know full shape.

[dake50]

If you aren't going to resolve shape first and scan in order of importance, there really is no good reason not to simply scan them in their natural order and play some souped-up type of natural cuebidding. Sweep cues are highly effective, in the hands of a pair that pays attention to all the inferences.

But they too - and standard cuebids for that matter - work a lot better if you know about singletons before you start cuebidding, even if you don't know full shape.
***
I have always questioned shape relays for this very point.
Relay for short *BEFORE* 2nd suit.
Now that short (working/or duplicated) is used to decide ask 2nd suit or not.
Essentially the remnant in shape-asks would show before the second suit.
That would determine if slamming was still feasible.

[the hog]

dake50, on 2013-April-13, 10:02, said:

If you aren't going to resolve shape first and scan in order of importance, there really is no good reason not to simply scan them in their natural order and play some souped-up type of natural cuebidding. Sweep cues are highly effective, in the hands of a pair that pays attention to all the inferences.

But they too - and standard cuebids for that matter - work a lot better if you know about singletons before you start cuebidding, even if you don't know full shape.
***
I have always questioned shape relays for this very point.
Relay for short *BEFORE* 2nd suit.
Now that short (working/or duplicated) is used to decide ask 2nd suit or not.
Essentially the remnant in shape-asks would show before the second suit.
That would determine if slamming was still feasible.

This approach is badly flawed and would lead to an unsymmetric and very difficult structure to remember. I don't think any serious player would even contemplate this.