I am gunna say some stuff that will be entirely different approach (and also agree with many great serve teachers like Brett Clarke)… so strap on your ratchet cargo straps and read.
Gus, what you describe you are doing (poor impact timing on aggressive serves) is what EVERY PLAYER does when they are trying to execute an aggressive serve where they have not become good enough on the major components.
There are SO MANY things going on in a serve, that if you try to do them all at the same time when you have not yet developed the skills to do them... it ALWAYS results in an EPIC FAIL every damn time.
I sound like I am making fun, but I will CHALLENGE anyone on the internet to show me video proof of being WORSE than when Der_Echte first started trying to learn serves. To put it short, if you were within 20 meters of me without robust body armor and ballistic eyewear, I was a severe public health hazard to you I mis-hit so bad and it was so epically funny.
What I advocate (so does Brett, I think MaTT does too) is a staged, progressive approach to get certain aspects of the serve down, so it is easier to put it all together.
The serve toss and timing to the ball are very important. It is also connected to the biomechanics to make the whip and there are also things to do with the impact itself, then also how/when/where to strike the ball to make it do what.
That is an awful LOT of stuff one usually never gets trained on... so when one watches a video, gets inspired, then goes to the table only to fail time and time again. it can get pretty discouraging pretty damn quick... more determined you are, often, the more of a hole you dig for yourself.
There are reasons. Again, I advocate separating the components to isolate things where you are only doing 1-3 things at a time.
First mistake on impact timing is people do not have a good ball toss and timing for the toss... which is compounded by trying to use a real long swing to whip the bat. Truth is, you do not need much of a backswing to make a good whip. Brett Clark "Serve like a Boss Backspin" vid - search for it on youtube. He advocates elbow tucked in a little behind and on side, just like you stuck a pole between both your arms behind your back and pretty much keeping elbow in this position. I advocate for a little more of a swing, but not much more backswing, elbow get to that position and must stop there and allow lower arm to go forward... it is that simple and not require a big backswing.
You can shadow practice that a few times to get the hang of it. To isolate and practice the impact to the ball, TAKE A SEAT !!! Yeah, sit down, toss ball a little over head high, do your tiny backswing WITHOUT the bat, open your palm, swing upper and lower arm, when elbow gets to position on side of body and a little behind, stop uppr arm and pivot lower arm on stationary elbow to go forward... with your open hand, you are catching the ball and following through a little bit.
This will isolate the other complicated stuff people are trying to do and will get you to quickly achieve decent impact timing with a short stroke. This is an important first step, because if you cannot do that 100%, serving at the table trying to accelerate the bat is gunna be a fail.
Next thing most do wrong on an underspin serve is failing to keep bat angle flat like the surface of table full open impact bottom of ball. People, when you actually video them, somehow have a habit of closing the bat on the swing and there is no way to serve short underspin unless the bat is full open.
So the next progressive step to address that is shadow practice your new short serve stroke and keep the bat angle exactly the same full open on backswing AND on the forward swing. Once you shadow stroke practice that to muscle memory... and that is real hard for some, but important, then you are ready for next stage.
Most people make a mistake at the table practicing as they are trying for too much of a swing and did not yet develop the open bat at impact... so they fail... what you can do is STAND UP on side of table or any open space, toss ball, and do your short serve stroke full open bat and impact bottom of the ball... swing under the ball and make it go up and forward... make ball go a 2 meters or so, and have the ball spin back to you. Do this on your most slippery surface, like the wood floor next to the table.
Since you have the basic timing to impact fixed, AND you fixed your basic whip, AND you fixed your open bat angle at impact... the drill I just described will practice putting all of those moving pieces together without the pressure of trying to get it all correct at the table... it is like a game... and it is.
Once you can consistently strike the bottom of the ball and make it spin back to you, because you also learned how to keep everything loose and firm up ONLY at impact... now you have developed
- A ball toss that works for you
- Good basic impact timing
- A fundamentally sound short whip motion for the serve
- A consistent open bat at impact
- Good loose muscles to whip and a good touch at impact to make good spin
Now these are the raw basic building blocks... you pretty much got most of it down... but you are not yet at the table and have the visual things going on as when you serve for real.
So, one additional step you can do is stand a meter or two behind table, do your ball toss, and try to make a high bouncing heavy underspin serve that lands once on your side of table, then spins back to net... and eventually back over the net, whether it is in 1 or 2 or 3 bounces. Important sign of spin is ball comes back and doesn't die.
Once you can do that, you are ready to go to the table. DO not expect perfection yet. Use endline as a guide for ball toss, impact ball close to the endline, do not toss ball 1-3 feet behind endline. Do not worry about making your serve very low over net - you are working on just getting ball to go over with good spin and be short...
You can fine tune the very small things of impact and bat angle and whip to get that nice short heavy tight double bounce serve as you improve those things. For now, you need to see the ball go in with decent spin and make it short.
There are a hundred of things to talk about how to get first bounce closer to net or further away and still have short tight serve... (thise things are dictated by how fast you make ball go forward and what horizontal/vertical angles are the result of your impact) for now don't geek out about any of that - just practice at one speed of serve . This will have you become consistent at that speed to make the serve short and tight as you develop command over bat angle, whip motion, and timing...
...once you get your comfortable speed of serve consistent short double bounce with good spin and good enough net clearance... then you can start experimenting with the more advanced aspects of the short serve of where on bat to strike the ball, how to vary it to get a different spin and launch... MaTT talked about this on a couple of his vids a few months ago. These are a great read great view, but it is a little advanced right now... but keep those in mind - you should improve and have a need to develop those things MaTT is talking about in those vids.
THEN you have the ART of selling a serve with your after motions and how/where you strike the ball with a similar serve arm slot and similar looking swing, but produce wildly different results.
That is getting into the JEDI MIND TRICK territory of serving... then you get into deception, double deception, triple deception, which all the territory of learning how to sell your opponent a pair of his own underwear as they say in the sales industry.
Serve ideas always evolve. There is science and the laws of physics... it is good to understand how they apply and how to use them. Then there is the Art and salesmanship/showmanship of serving.
Ultimately, one should ask oneself an important question...
WHAT IS THE PURPOSE OF A SERVE IN TABLE TENNIS?
The answer should be something along the lines of:
A. To give the server an IMMEDIATE OFFENSIVE ADVANTAGE in the rally.
You integrate serves and attack and mix it in with your over-all tactics and plan... which should be very flexible... but it cannot be flexible if you have not practiced a whole heap of good serves.