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Seam Sealing X-PAC: What Works Better?

by Jameson MacFarland-Hall February 03, 2021 3 min read 4 Comments

Seam Sealing X-Pac

X-Pac® has long been one of the most popular fabrics on the market for making backpacks, bags, accessories, and more. Tons of makers rely on X-Pac® to bring the best performance to their gear.

However, a common problem that DIYers struggle with is how to seal their project when using X-Pac®. Although seam sealing is not crucial for all items, no one wants their stuff to get wet.

In this article, we'll look at two common methods of seam sealing: silicone and PSA tape to see how they work on X-Pac®. Let's get started!

Shop X-Pac® fabrics HERE 

Why Seam Seal?

Although it is certainly not a must, we recommend that you seam seal your X-Pac® project for a few reasons. 

First, every time your sewing needle penetrates the fabric, you create a place for water and moisture to pass through. Repeat that hole-punch several hundred times and you've got a LOT of places for water to seep in. Proper seam sealing will close all of those little needle holes and make sure the items inside stay dry. 

Second, seam sealers help strengthen the stitches by acting as a bonding agent that holds everything together - sort of like glue. Some people worry about the additional weight of seam sealant, but this is often negligible. 

Shop seam sealers HERE

So, What's the Test?

To start, we standardized our test by making two identical X-Pac®  VX07 stuff sacks. When we say they were the exact same, we mean it - dimensions, construction, stitches, buckles, and webbing. 

After making the stuff sacks, we seam-sealed one with Silnet Silicone Seam Sealer and the other with DCF repair tape

Lastly, to further standardize things, we put the same amount of stuff in each sack. We even matched the number of rolls for the roll-top closure.  

Finally, it was time to make it rain!

Putting the stuff sacks through a rigorous test was important to us. Simply testing water resistance wouldn’t tell the whole story. That said, we chose to completely submerge the stuff sacks to stress the seams as much as possible.


Silicone Sealed Stuff Sack

The silicone-sealed stuff sack was noticeably damp on the inside, but not sopping wet or dripping. Also, no water had pooled in the bottom. But yeah, it was a far cry from a "dry" bag. 

From what we could tell, most of the moisture was near the bottom of the sack. For that reason, we think that water probably entered through the bottom seam. When we sealed the bag, we made sure to seal on the top, bottom, and in between the panels knowing that this might happen.

Overall, we give the silicone seam sealer a grade of "C". It kept the items mostly dry, but not entirely.

DCF Repair Tape Sack

If the silicone seam sealer got a C, then the DCF® repair tape got a C+

It was also noticeably damp on the inside, but again, none of the fabrics were soaked. There also appeared to be less moisture overall within the sack as compared to the silicone-sealed test.

Interestingly, it appeared that the water was more prevalent on the upper half of the bag. Most likely entering through the closure or the roll top seams.

But once again, not good enough to be a dry bag.


Although neither system worked as well as we hoped, we still recommend that you seal your X-Pac® projects. The test that we ran on the bags was far more rigorous than what most people will see. We believe that if these bags were just exposed to rain or a brief submersion, they would have been totally fine.

The most important piece to remember when seam sealing is to cover all important seams. If you’re taping, ensure your margins are small enough to tape over comfortably. If you’re sealing, then make sure you apply the gel in all areas needed, (i.e. between panels). 

After all, a bag with good water resistance is better than a bag with no water resistance.

Lastly, be sure to stay tuned as we plan to continue this testing in future articles with new methods and sealants. The seam sealing search continues...

Your Thoughts 

  • What do you think about our test?  
  • Do you have a method that works well for you?  
  • Let us know in the comments below!

4 Responses


March 04, 2021

Silicone seam sealant is for silicone fabrics, so is a poor test for XPAC? Surely seam grip is a better choice, as it sticks well to anything but silicone fabrics.

Ripstop by the Roll
Ripstop by the Roll

February 08, 2021

@Michael – We have heard that @Guy is correct! Silnet sealant seems to work better than the two tested here. However, we have also recently discovered that Dimension Polyant now makes an X-Pac specific PSA tape! We are hoping to get that in stock soon. On this week’s podcast, we chatted with the makers of X-Pac, may be worth a listen if you’re interested!


February 07, 2021

Thanks for posting this comparison. Have you tested the performance of water-based seam sealants such as the Gear-Aid product? https://www.gearaid.com/products/seam-grip-sealant-fast-cure

My experience on a VX-42 framebag was very poor with the same silicone product you used.


February 07, 2021

So I was looking forward to this video when I saw it was posted because I’m in the middle of designing and constructing a few things. However I’d have to say I’m disappointed in the results. What actually works well?!?!?

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