How does baseplate shimming work?

I thought I understood baseplate shimming but realised I don’t at all have an understanding of the mechanics of it. Is the board flat and we change the foil angle? Or is the foil always flat and we change the board angle?

Does anyone have a good explanation?

KDMaui has a great explanation of what to change based on different feels, but I think it would help to have an explanation into why it feels different, as it is something I don’t really have a good understanding.

Maybe other than shimming baseplates to remove the effect of board rocker, we shouldn’t baseplate shim?

1 Like

I’ve just started shimming the front with a 1° shim on my takuma foils, and really like it. The main reason right now is that the foil doesn’t seem to come up too much and brake, so that suggests it adjusts the foil. But winging i like it because the board is more level, so I guess it’s both, depending on the situation.

That’s an awesome visual right there. I always think about the paper airplanes I made as a kid to help me understand what those angles mean. I used to tilt the wings up to pull the nose of the plane up, flat for speed and down to pull the nose down. Too much in either direction and the plane wouldn’t “cruise”. I’d imagine that you just need a tiny tweak for that base shim to feel right on the foil. I’d like to dive back in again on this topic - as I’d like to tighten up my stance and move forward on the board. I think this takes away a little efficiency but it’s a balancing act based on a bazillion factors.

1 Like

The board flat illustration is true when the board is in the water, the foil flat illustration is true when the board is out of the water.

This means that shimming the base changes how much AOA you have at takeoff since the board will be more or less flat in the water at that point. Nose down shim will make the foil want to takeoff earlier since there’s more built in AOA. To me, shimming in the “board flat” scenario is about fixing takeoff issues, so if your nose is bogging or the foil is lifting too soon, you might want to shim nose up. Likewise, if the tail is bogging or the foil is not lifting enough, try shimming nose down.

Once flying, the foil will always be at the same AOA at any given speed regardless of base shim. This means that shim changes the angle of the deck while riding. Optimum deck angle can also be affected by: Rider preference, Speed range, Board design, Foil design, Foil setup… A lot of variables.


@J_L that is perfect, nice one.

So in essence you can compensate too short or poorly positioned foil tracks with the shim to manage a takeoff.

When up and riding, ideally the deck and foils are parallel and you rely on the foil designer to have optimised things, and not need much shim for the designed context, BUT if you do need to change the feel, you can tweak things.

fwiw I updated it with your and @KDW insights, thanks both.


1 degree baseplate shim leveled off my ride when up and foiling. I’ve only tried it winging but will definitely try it on the prone board.

1 Like

Great illustrations :clap:

I’ve tried shimming a Lift 120 “nose up” per KDMaui’s tip in the past, but it felt like it caused too much drag while prone paddling around.

1 Like

nose up shimming definitely helped me handle steeper take offs (on lift ha gear with lift glide tails)

I had a wing foil setup where the board and foil were not working in harmony. The result was too much drag trying to get moving. Shimming nose down helped a lot.

I would consider shimming only if the board angle seems wrong while riding or if the board is draggy and doesn’t come up to foiling speed without excessive power.


Great points J_L, I completely agree there are two ways to think about base plate shimming - effects to takeoff and effects to riding when on foil. I’ve pointed out to people asking about shimming to think of it as a “board shim” rather than a “base plate shim” which often makes things click.

When riding at a given speed, our foils need to produce a set amount of lift (your weight plus ~gear weight). To do this, the foil runs at high angles of attack at low speed and will actually move into negative angles of attack at very high speeds.

Base plate shimming when riding is really just working with this phenomena. If you know you’ll be going slow and working to build speed during the session, your foil will be forcing your board “nose up” so shimming your board “nose down” will counteract this and feel more natural. Conversely, if you know you’ll be pushing your foil really fast in big waves or high winds, you can counteract the “nose down” pull of the foil by shimming your board more “nose up” for more secure feeling riding and better touch down performance.

Similarly you can take advantage of this and use baseplate shims to get on foil with less energy. Taking off at the lowest speed possible corresponds to the highest angle of attack which your foil can lift you (stall speed). If your board and foil are parallel, this mean your board will not be at its most efficient when your foil passes though its stall speed or rather your foil will not be at it’s critical angle of attack when accelerated past its stall speed. By shimming your board “nose down” the board moves through the water more efficiently and the foil is closer to the critical angle of attack.

Luckily, these aspects of shimming generally works well together since shimming “nose down” for really light wind wing or small waves will also perform well during riding since you’ll likely be below peak efficiency most of the time. For high wind or powerful waves, trading takeoff efficiency for high speed performance is usually an easy decision!


So on a downwind board in week waves when learning should you shim the back of the mast?

1 Like

Answering @Girvin, and just to check I understand you @Greg_F:

Yes you need to shim the back of the mast, the idea being that you will be paddling the board with the foil at an angle closer to it’s highest lift position. The downside to this, is that the foil will be lifting off closer to the stall speed, and so you will have to be careful not adding any additional foil angle because it will stall it. Depending on the foil obviously as some can tolerate more angle.

Greg this part I don’t think I agree with, the foil will have an increased angle of attack, so more lift but also more drag?

1 Like

Hey Matt, I worded that poorly. completely agree the foil will have more lift and more drag at the higher angle of attack imposed by a nose down shim. However, this drag is minor compared to the drag of the board.

Without the nose down shim you’d have to increase the board to a higher angle of attack in order to bring the foil up to an angle which it can lift you. Due to this the whole “board/foil system” is producing more drag at minimum takeoff speed with the foil at the critical angle of attack.

Pumping can change this very temporarily which is why we don’t need to shim the board extremely nose down to get the foil right close to its stall angle but even a couple degrees closer has made a big difference in my experience winging and prone surfing and I think this is due to the whole foil and board system producing less drag when I’m working to get on foil.

1 Like

I get you, thanks, yes replacing board with system and then it reads per my understanding.

So could you perfectly tune a board shim so that you never need to pump the board off the water, so perfect that any pumping would be in fact worse and hinder the takeoff?

Edit: Thinking about that a bit more - the foil comes tuned to provide sufficient lift force at a specific speed (eg 70kg at 12mph) when flat, so I suppose the answer is yes you could tune it to provide that 70kg at 8mph but then you are taking off at a much lower and more precarious speed? (A worthwhile DW trade off when every mph is muscle power)

And further, the trade off being less control and stability at high speed for the sake of the earlier takeoff… yes this is covered already just joining the dots on my head

Hey Matt, shimming to takeoff with minimum speed and no pumping should definitely be possible! That would end up being over 10 degrees “board nose down” though for most foils so I think not practical as it would be uncomfortable at even moderate cruising speed and touchdowns would be instant superman!

1 Like

Anyone have leads on people making the heel to toe shims? keen to give one a try

1 Like

@ChiliG What if we mock one up and 3D print it? This could be a decent starting point for size. Not sure about what sort of angles would make sense.

Fold two credit cards into thirds as a quick test. I did that for a shim before, works fine.

Something like


Stole my daughter’s safety scissors and made a video on this topic:

Let me know what you guys think, I made a couple technical slip ups but I’ll blame that on glue fumes!


Would be great for racing, but just going one direction :face_with_spiral_eyes:

What else would you think it’ll be better for?