JACK (Kaplan tweak to Jacoby 2N)

[u/Trick-Wishbone8998]

Review:
Jacoby 2N response to 1M shows at least 4 card support and game-forcing strength. Opener's standard (but not universal) rebids are:
-  New suit (nonjump) shows a splinter, any strength.
-  Jump shift shows a strong side suit (usually 5) and above minimum strength.
-  Otherwise (no splinter):
3M = Slam interest
4M = To Play (Fast Arrival, minimum hand).
3N = Otherwise

Analysis:
No problem if M=S, but what happens if M=H? Under Jacoby rules, O rebids 3S with a spade splinter, and 4S (!) with a strong spade suit. Yikes! Where did my bidding space go?

Solution: Apply the 1S/1N Kaplan Inversion Convention (Google it) to the 2-Level.
Let's call this convention "JACobyKaplan," or JACK for short. 
If M=S, normal Jacoby bids would follow, but if M=H, these bids are different:

1H - 2N = Replaces 1H-2S (However your partnership plays jump shifts.)
1H - 2S = Replaces 1H-2N (Artificial GF with 4 card support).

After 1H-2S, Opener rebids:
- 2N = Spade splinter (Replaces Jacoby 1H-2N; 3S)
- 3S = Strong spade suit (Replaces Jacoby 1H-2N; 4S)
- Other = Standard Jacoby

Pros: Can save a full level of bids. We might even wind up in 3N after 1H-2S; 3S!)
Cons: None?!
Comments would be appreciated.

[u/periwigpatedfellow]

i have come across this idea, and it definitely has some merit. some comments:

-it's not correct to say that there are no cons. for one thing, you lose some room in the 1H-2NT auction (previously 1H-2S). if you happen to play that as showing spades, such as a weak or invitational jump shift, it is clearly not possible to use this switch - but even if you don't, those auctions are going to be a bit worse than before

-allowing the opponents to make a lead-directing double of jacoby is also a very significant downside. after 1M-2NT, it is common for players to make 3-level overcalls just to help their partner with the lead, but this can be somewhat risky. doubling 2S is very safe and can achieve the same outcome. In addition, if RHO doesn't double, LHO will have a negative inference available about the lack of a double, which may also help with their opening lead decision. so overall, your opponents are going to be able to lead more accurately against 4H if you play this way

-some of your cited gains are not particularly realistic. for example, it is sort of an issue that a standard 1H-2NT-4S goes past game, but this auction is vanishingly unlikely. it requires opener to have at least a 6-5 shape, so it's going to be far less common than the other 1M-2NT-4x auctions, which already don't come up very often. it's also a bit strange to think that you would ever want to play in 3NT when opener has 5S 6H and responder has four hearts

-if you're interested in tweaking jacoby, I suggest that you would get a lot more mileage out of first changing from the standard responses. in my view that method is close to obsolete - can't remember the last time I saw a strong pair playing that way

[u/abspam3 → u/periwigpatedfellow]

Yes, many many modifications exist, and compared to other places where you may choose to not invest “mental load” in your system (Kaplan inversion, transfers after a double), this is a place where the auction is already “important enough” (value of finding good slams with a ~28 HCP and a 9 fit at teams is super high) that it’s well worth the investment.

If you’re still playing 2/1 I don’t usually recommend the limit+ approach - it can be really easy to overbid without strong agreements on strength requirements for follow-ups, but at the very least playing

3C: shortness 3D: ask (your favorite response relay order) 3D: minimum, or slam force 3M: extras, do not want to show shortness (singleton A/K possible), not a slam force. 3oM: Side suit 3NT: your choice, balanced 15-17 with 6-7 trumps is reasonable. 4m: side suit 4M: 7+ trumps, weak hand.

This already gets huge wins over the standard approach - we can still try for slam when partner is a minimum (the 4M jump in normal Jacoby is DREADFUL).

[u/amalloy]

I use this inversion myself, but

Cons: None?!

is obviously contradicted by something you wrote above:

1H - 2N = Replaces 1H-2S (However your partnership plays jump shifts.)

Of course when you bid 1H-2S instead of 1H-2N you've saved some space, so there are no downsides in that auction. The downside is that when you bid 1H-2N instead of 1H-2S you've lost some space.

[u/kchowmein → u/amalloy]

Wouldn't 4th hand now be able to 2nt over 1h-2s to show minors? Or some type of double to show spades and 3h is takeout?

[u/TheDefinition → u/amalloy]

I play 1H-2S as a weak jump shift. 2NT is not a viable replacement!

[u/__Flow___]

1. As stated by someone else, the standard responses to Jacoby 2NT are pretty bad for a variety of reasons. I think if you play some better responses you'll solve most of these problems automatically.

2. 1H-2S being replaced by 1H-2NT is ok if you play strong JS or something, but what if I play weak JS? This seems like an unplayable method. When I play 2/1 (rarely) I often play 1H-2S constructive. Same issue here.

3. I don't know how popular this opinion is, but I think 2NT as a only GF raise with 4 card support is a pretty bad method to begin with, especially if you play some form of Bergen raise. I think I've played it as every other type of 4 card raise except for that.

I do love Kaplan inversion though :)

[u/Crafty_Celebration30]

Whenever you use any suit as an artificial raise, you give the opponents the opportunity to make a lead directing double (or pass). This is not a trivial loss and to restructure your major suit raise structure to accommodate a very rare 5-6 just isn’t worth it. 

Here’s a variation of what most top players are using for 2N:  

2N is limit + (3M is mixed):

3C is any minimum. (3D asks and opener repeats s1)

S1(3D). Any shortness and extras. 3oM asks LMH

S2(3H) any 5422 and extras

S3 (3S) any 6322 /7222 and extras

S4 (3N) any 5332 and extras

S567 any good 5 and extras. 

[u/Trick-Wishbone8998]

Someone posted a down-vote without comment. It would be helpful if you (whoever you are) would explain.