How To Use Tail Wing Shims On Your Hydro Foil

Tail wing shims can be incredibly confusing and really mess up your ride if you don’t know what you are doing.  Here is a quick run down as to how tail shims work on a foil.

What is a shim?

Foil shims will vary from company to company, but generally speaking they are small plastic wedges that changes the tail wing angle of attack.

Why do you need a shim on a foil?

When you change the tail wing angle with a shim, you can make the foil have more or less lift, improve pitch stability, go faster or slower and increase or decrease the turning radius.

Shimming Basics:

When you shim the tail wing you are changing the angle of that tail.  If the tail wing is on the bottom of the fuselage, a negative shim is making the trailing edge of the tail wing higher than the leading edge.  This causes more drag, has more lift, more pitch stability, less glide and stiffer turning.  Negative shim is best for beginner or intermediates riders.

If you add a positive shim and the tail is on the bottom of the fuse, the trailing edge of the tail wing is coming down and the tail wing will be flatter. This has less drag, less lift, less stability and is faster and looser. Positive shims are best for intermediate to advanced riders.

When the tail wing is mounted on top of the fuselage, the effects of shims will be opposite of what is listed above. The negative shims will make the foil faster and looser and the positive shims will make the foil slower and more pitch stable.

What shim set up will be right for you?

Your ability level will dictate the appropriate amount of shim for you. Most beginners to intermediate should be using no shim or a negative shim (tail wing on bottom of fuse) to maximize your stability and lift you are getting from the foil.  As you advance and want higher speeds, longer glides on your pumps and looser turning, then you can start shimming up the tail with a positive shim(tail wing on bottom of fuse).


As you start to add positive shim (tail wing on bottom of the fuse) you are decreasing the lift that the tail wing is creating.  This will make it harder for the foil to come up out of the water. To compensate for this, you need to move your mast forward so get more lift from the front wing. With the more forward position of the mast, the board feels shorter since you only “feel” the board that is in front of the mast.  

A mast that is farther forward allows you to pump better since the board is essentially shorter, and you will get more crisp turns by putting your foot behind the mast. For a general rule, you will move your mast forward a centimeter for every degree of positive shim you add to your tail wing(tail wing on bottom of fuse).

How to dial in your gear:

Tuning in your tail wing shim and mast position can be really tricky and make things worse rather than better.  We recommend to ride the stock set up until you are comfortable with it.  When you are ready to test shims, change one thing at a time mid-session.

First add the shim and keep your mast in the same position. Test the foil. Second come in and adjust the mast. Positive shim, the mast moves forward and negative it moves back(tail wing on bottom of fuse). Test the foil.  As you make these adjustments one at a time, you will have the ability to feel what works for you.  Everyone rides a foil very differently so if you want to get more performance by shimming your tail, you will need to do some testing to find out what works for you.

If you have more questions about foils, contact a REALpro at 252.987.6000 or email us at

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