gwnn, on 2011-August-15, 17:53, said:
just to reiterate, you would double on a 4531 11 count, but would overcall on a 4531 18 count, and you think this is common sense?
Let's look at all the possibilities, assuming that partner can have either three hearts, four hearts, four spades, five spades, four diamonds, or five diamonds.
Bold ones are the ones unique to that choice.
If you overcall on the 4531 11-count, you will get a useful bid from partner when:
1. He has 3 hearts and you have a partscore
2. He has 4 hearts and you have a partscore
3. He has 3 hearts and you have a game
4. He has 4 hearts and you have a game
5. He has five spades and you have a game (unless the responder passes and pard can bid 1S with ~9 HCP)
6. He has five diamonds and you have a game
6 1/2. He has four diamonds and you have a game (not too likely you make 3 extra tricks in diamonds than NT, probably won't matter if you miss the fit)
If you double, you will get a useful bid from partner when:
1. He has four hearts and you have a partscore
2. He has four hearts and you have a game
3. He has three hearts and you have a game
4. He has four spades and you have a partscore
5. He has five spades and you have a partscore
6. He has four spades and you have a game
7. He has five spades and you have a game
8. He has four diamonds and you have a partscore
9. He has five diamonds and you have a partscore
10. He has four diamonds and you have a game
11. He has five diamonds and you have a game
Summary:
Overcalling has one good thing going for it: you will find a 5-3 heart partscore where by doubling you won't.
Overcalling has several bad things going for it: you miss all diamond and spade partscores (four altogether) and you will make it difficult to find a 4-4 spade game.
In conclusion, making a takeout double with a takeout double shape, when you are not strong enough for two bids, is the best bet.
(Upon reflection, this is actually quite similar to opening 1NT with 15-17 with a balanced shape, whether or not you have a five-card major - getting ~11 of your cards across and 15 of your points is better than five of your cards and 11 of your points. Aside from the fact that all of your rebids will be lies)
For the rest of what you said gwnn, I guess the overcall first then plan to takeout double if they pre-empt would have an upper ceiling of about 17 or 18, if responder finds a pass, partner would need about 8 or 9 to bid 1
♠ or 1NT, so if you had any more than 18 there is a small danger of missing a game. If you have more than this, 18 or 19+, you'd plan to double and bid/invite game if pard bids your five card suit or cuebid otherwise.