Trimming Drysuit Gaskets -- Another Method May 01 2015

Drysuit gaskets or seals often need to be trimmed. Most come with fairly small openings to fit people with small necks or wrists, and these are often too tight for people with larger body parts. Some gaskets come from the manufacturer with the ends entirely closed (see photo below), and these have to be cut open by everyone and trimmed to size.

drysuit with closed, untrimmed neck gasket

We blogged previously about trimming drysuit gaskets using scissors. That method works well, but we now prefer this method, which we find easier to produce a nice clean cut, and quicker as well.  

Tools

tools for trimming a drysuit gasket

You'll need:

  • An 11-oz. coffee can (this size people still call "one pound") or a 1-qt. paint can for neck gaskets. For wrist gaskets, use a 6-oz. tomato paste can for narrow wrists or a 10-oz. soup can for wider ones. If a can is just a little too narrow, you can build it up with several wraps of masking tape, as on the paint can in the photo.
  • Scissors: only needed if the end of the gasket is closed.
  • Utility or craft (e.g., X-acto) knife
  • Sharpie or similar permanent marker

Procedure

opening a closed drysuit gasket with scissors

If the gasket has a closed end, cut it off with the scissor above the first molded guide ring (i.e., the smallest opening). This cut doesn't have to be terribly neat, as long as you don't leave any nicks in the edge that could turn into tears when you stretch the gasket in the next step.

use a marking pen to highlight the trim ring on a drysuit gasket before cutting

Turn the drysuit inside out. Stretch the gasket over the can and position it so that the guide rings are fairly straight and even. Pick the guide ring you want to cut, and use the marking pen to highlight it all the way around. The guide rings can be difficult to see, even with good light, and the marking pen helps a lot. You can mark just above the ring you plan to cut, or mark right on the ring itself.

trim drysuit gaskets with a utility knife

Lay the can on its side. Cut through the gasket with the utility knife, making long, smooth cuts.

drysuit gasket stretched over a can, trimming with knife

You'll have to stop periodically to turn the can. When you do, begin the next part of the cut exactly where the previous one ended. Make sure the final cut ends exactly where the first one begins.

slight flaw in trimmed drysuit gasket

There's a slight dip in the edge of this gasket. This is okay, but if you want to make this a neater job, or if you left a nick in the edge that could turn into a tear, you don't have to cut all the way down to the next guide ring. Instead, make a gradually-sloping cut to exclude the just the flaw. You're aiming for a smooth, gradual dip in the edge.

properly trimmed drysuit neck gasket 

The finished trimmed neck gasket, turned right side out.

Notes on Sizing Drysuit Gaskets

Drysuit gaskets should be just slightly snug but not uncomfortable. If you feel tingling or numbness, or if breathing is difficult, the gasket should be trimmed wider.

Trim off just one guide ring at a time. A little bit can make a big difference. You can always trim it wider, but you can't undo a cut if you've taken off too much.

Rather than trimming their gaskets, some people stretch them, placing them over a fairly big object and leaving them there for a few days. We advise against this, as it permamently reduces the elasticity of the rubber.

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