[kenberg]

Suppose that I open 1C, lho passes, partner responds 1S, rho overcalls 2D or 2H, I make a support double, lho passes, partner bids 2S, rho opponent passes.

OK, if I have a minimum hand I pass. Suppose I have a good hand. Since I didn't open 1NT, suppose I have a good hand with long clubs. What are my options?

Partner does not really have to have five spades, right? With a six count and four spades he would respond 1S, he can't leave the double in, so he bids 2S, right?

If I bid 3C, he will rebid spades whenever he has five. Can he pass if he has only four spades? I would think so.

Suppose he has five spades. When will he simply coonvert 3C to 3S, when will he bid 4S? Suppose we agree that I always pass 2S when I have a minimum (I would) but that still leaves the question of how, with 5-3 spades, we sort out landing in 3S from 4S. Some samples:

AQx/xx/x/AKxxxxx. Do I bid 3C and then pass out partner's 3S?

How about AQx/xx/x/AKJxxx.
or AQx/xx/xx/AKQxxx.
or Axx/xxx/x/AKQxxx.

etc.

The general question is how to develop the auction after the support double, given that opener has extras. When would partner bid 4S over 3C, when would I raise his passable 3S to 4S?

[Codo]

3 ♣ is never ever just a try to improve the contract, it is always a game try in itself. To me, pass is the only answer with just 4 spades in a weak hand. The strong answer is the cuebid or 3 NT.
This is much more tricky over 1 ♦ pass 1 ♠ (2♥) X (pass) 2 ♠ (pass) 3 ♦. Partner may look at a 4216 hand or so and may judge that 3 spades is a better partial.

With all your example hands however, I would pass 3 ♠. With KJxxx,Ax,xxxx,xx or similar, he had accepted my invitation anyway.

[Fluffy]

What Roland said, 3♣ is a game try, with more or less same playing strenght as a 3♣ rebid, I think some of your example hands are close to just passing 2♠.

[phil_20686]

3C is constructive but NF. You can cuebid with a GF hand.

I think 2N should be forcing for one round, and should show a heart stop, but basically when partner is weak he should be compelled to go back to a suit, even with only four spades. 2N then should be 15-17, and typically some 3316 or 3415 hand.

[kenberg]

Codo, on 2012-September-12, 03:06, said:

With all your example hands however, I would pass 3 ♠. With KJxxx,Ax,xxxx,xx or similar, he had accepted my invitation anyway.

Right, this is helpful. The way to decide when I would pass 3S is to first be clear on when I would not have to decide, partner already having bid 4. Assuming he would bid 4S with the hand you suggest, passing 3S is easy. We were in 4S failing on hands that I do not precisely remember, but my strong three card spade holding and my strong six card club suit was not enough. I'll discuss this with partner from the viewpoint that you suggest: When will 3C be followed by 4S?
Thanks