Pumpsack Modification

27 October 2023

It's the day before a trip, which means it's my best time for last minute gear modifications!

Today, I'm working with my beloved 2018 Thermarest NeoAir Xlite. It's lightweight, warm, and packs really well! I used to camp with someone who had a matching pad and the associated pump sack, which I would borrow to inflate mine. This year, I tried to get my own pump sack, only to find that Thermarest no longer sells ones that match the older style valves. Inflating by mouth is possible, but not optimal; it introduces moisture into the inside of the pad, and with such a plush pad, it takes a tremendous amount of breath to get there.

So! Earlier this week, I noticed that 3ROC had an inflation bag from Big Agnes in stock. The valve, however, is oversized for my Xlite. This is fine; it's easy to make something that's the right size from something that's too big.

I cut a piece of rubber off an old bike inner tube, gave it a good scrub with simple green to take off some gunk, and cut a small hole that fits snug to the Xlite's valve. Then, I trimmed this down to a donut that fits over the inside of the pump sack's valve. I roughed up the rubber with some sandpaper, applied contact cement to the rubber and the valve reinforcement panel, then carefully pressed them together. Now I have a pump sack that fits my Xlite!

The downside: fitting the rubber donut over the Xlite valve puts pressure against the glue connection, which risks ripping it off. However, the connection is strong in the direction of airflow, which is what I wanted to optimize. I'll find out this weekend how it holds up.

Photos!

The top of a bright yellow Thermarest NeoAir Xlite with my hand holding the small valve.
The Xlite with the old style valve

The Xlite valve inserted into the Big Agnes pump sack, with about a centimeter's worth of gap all around it.
This large gap makes it impossible to inflate with this sack.

A rectangle of bike innertube rubber held in my hand next to the pump sack and sleeping pad.
I have so much bike tube rubber, y'all.

The tube with a small circular hole cut out of it.
Using the elementary school skill of folding something in half and cutting out a semi-circle along the fold in order to get a nice circle.

Showing off the rubber strip fitting snugly over the sleeping pad's valve.
Fit-test!

The rubber strip trimmed down to a donut, shown over the reinforcement panel of the pump sack's valve.
Trimmed down to size; rounded shapes are more secure for adhering, because the edges don't tend to peel as much as if there's a corner.

Sandpaper, donut, and contact cement. I'm now wearing a black nitrile glove to protect my hands from the adhesive.
Rubber adheres better if it's a little roughed up.

Closeup showing contact cement on both the rubber donut and the valve reinforcement panel.
Contact cement applied to both sides, then left to cure for a few minutes until it becomes tacky.

The donut glued over the valve.
Line up the donut and press!

The outside view, showing the donut inside the pump sack valve, and the sleeping pad valve nearby.
Hope this works tomorrow night.