FIN ASSEMBLY GUIDE | How to fit your fin into the box and don't damage it
We’ll cover:
Tools You’ll Need
Step 1: Fit the Fin by Hand
Step 2: Sand for a Perfect Fit
Step 3: Choose the Right Screw Length
Step 4: Emergency Screw Fix
Step 5: Tuning with Rake (Optional)
NP7 Fin - developed by Nico Prien
Checklist
How to Fit Your Fin Perfectly Into a Fin Box (Without Damaging It)
Upgrading your windsurf board with a third-party fin—like the NP7—can unlock significant performance gains. However, to get the most out of your fin (and preserve its warranty), it’s crucial to follow a few essential steps when fitting it into the board. In this guide, we’ll walk you through how to properly fit your fin, avoid damaging it during installation, and use fin rake to fine-tune your setup.
⚠️ Warranty Disclaimer: NP7 fins come with a strict warranty condition—if you damage your fin by using incorrect screw lengths or forcing it into place, the warranty is void. Be sure to follow the instructions below precisely.
Step 1: Why Your Fin Might Not Fit Perfectly (And Why That’s Okay)
Each board and fin is made in different factories—often by hand. These semi-custom manufacturing processes can result in minor variances in shape and dimensions. As a result, it’s completely normal for a new fin not to fit perfectly out of the box.
In fact, it’s better if the fin is slightly too large rather than too small, because material can be removed for a perfect fit, whereas gaps caused by too-small fins can’t be easily fixed.
Step 2: Tools You’ll Need
Torx screwdriver (or standard screwdriver)
Small screwdriver (flathead or similar)
Sandpaper (120–180 grit for shaping, 600 grit for finishing)
Sanding block (wood or aluminum)
Screws in various lengths
Washers
Step 3: Fitting the Fit
Test the Fit: Insert the fin as far as it goes by hand. It’s okay if it doesn’t fully seat—it shouldn’t require force.
Identify Contact Points: Remove the fin and look for scratched areas on the base. These indicate where the fit is too tight.
Sanding: Use 120–180 grit sandpaper on a sanding block to gently remove material from the tight spots. Take off a little at a time and check the fit repeatedly.
Fine Finish (Optional): For aesthetics, you can use 600-grit wet sandpaper to smooth out the surface.
Repeat this process a few times until the fin sits almost flush. Be patient—removing too much material can make the fin loose.
Step 4: Choosing the Right Screw Length (Avoid Fin Destruction)
Before screwing in the fin:
Use a small screwdriver to measure the depth of the fin box.
Mark the insertion depth with your finger and compare it to your screw lengths.
Choose a screw a few millimeters shorter than the measured depth.
Warning: Using a screw that’s too long will force it into the solid part of the fin head or even the blade—this can crack the head, push out the blade, and void your warranty. This is one of the most common and costly mistakes!
Always use washers between the screw head and board to distribute pressure. If you’re short on the right screw length at the beach, adding extra washers is a temporary fix (though not ideal).
Step 5: Raking the Fin – The Final Tuning Step
Once the fin is securely installed, you can fine-tune your board’s behavior using rake adjustments:
To Raise the Nose: Sand the back of the fin slightly more so the rear of the fin can sit deeper in the box, increasing the rake.
To Lower the Nose: Screw the front in more, leaving a slight gap at the front and reducing rake.
It’s okay if the fin isn’t perfectly flush after raking—as long as it’s not sticking out. I’ve done it before in competitions and have achieved very good result with it.
Final Thoughts
Fitting a third-party fin like the NP7 into your board is a process of precision and patience. Do it right, and you’ll have a snug, high-performing fit that holds under pressure. Take your time, follow the steps, and protect your investment.
And remember—incorrect installation, especially screw damage, voids the warranty. Always measure before you tighten.
Now you’re ready to get back on the water—faster, tuned, and without damage!
The NP7 Fin - developed by Nico Prien and Phil Carbon
NP7 Rockstar Fin – First Limited Edition
I’ve always said that a fin is the most affordable way to make a big leap in your windsurfing equipment. That’s why I’m presenting the very first NP7 product here: the NP7 Rockstar Fin. It’s now available for order, and I’m very proud of it.
The NP7 Rockstar is a premium fin made from the best materials and with top-tier craftsmanship. The result is a fin that offers an exceptional combination of speed and control.
What Makes It So Special?
Its unique design, performance tuning, and build quality ensure that it stands out — whether you’re chasing speed on the straights or control in tough conditions. This is not just another fin; it’s a performance upgrade tailored for riders who want to push their limits.
Where to get it
You can order the NP7 Fin via surf-center.com
Checklist
🛠 Tools Needed
Screwdriver (torque preferred)
Small screwdriver (for depth check)
Sandpaper (120–180 grit)
Optional: 600-grit wet sandpaper for finish
Sanding block
Screws (various lengths)
Washers
🔧 Fit the Fin
Insert the fin by hand—slight resistance is normal
Remove and check for scratch marks = tight spots
Sand only those areas carefully
Repeat until the fin sits nearly flush
(Optional) Use 600-grit wet sandpaper for a smooth finish
🔩 Set Screw Length
Use small screwdriver to measure box depth
Select a screw a few mm shorter than the depth
Always use a washer
Never force a screw—it can crack the fin
Wrong screw = no warranty + damaged fin
🛠 Emergency Fix
No short screw? Use extra washers to shorten it (temporary fix)
⚙️ Fine-Tune with Rake (Optional)
Sand back of fin more = more rake = lifts nose
Sink front of fin into the box = less rake = lowers nose
Slight gaps are okay—just don’t let the fin stick out