Synapse 25 true volume

[gianlucamazzi]

How is the volume measured? What is the method to come to 25L?

In looking at the dimensions, I see that competitor bags of around the same HWD have more around 30L. I assume this may be due to the amount of material used on the inside of the bag for dividing it up into each compartment.

Synapse 25 25L 20 x 13.4 x 9.1

vs...
Timbuk2 Uptown 30L 19.5 x 11.6 x 6.50
Tortuga Outbreaker 35L 20.3 x 12.9 x 8.2

[sturbridge]

This is from a 2018 post by Darcy when asked how another product volume was measured:

We currently calculate volume using the ATSM standard (or a slightly modified method): we fill a bag with 20mm (~0.75”) hard polypropylene balls, then remove the balls and dump them into a graduated measuring cylinder and/or we also weigh them (weighing turns out to be a more accurate method for smaller bags/pockets/compartments). For the three dimensions (LxWxH) we use a big set of calipers. So, two different methods. Remeasuring/fixing the dimensions doesn't change the volume.

[Cristina]

Thanks sturbridge for quoting Darcy’s post on how they do the measurement.

I have been using my Synapse for a few years now and the way that space is divided in it is quite different from most bags out there. In a Synapse (and Synik) there is the main pocket and then there is the front half of the bag, which is pocket city. The front pockets of a Synapse 25 can hold two 12 ounce water bottles or two Side Effects (in the side pockets), a 16 ounce Contigo thermal water bottle (in the water bottle pocket), AND a 3L Side Kick bag (in the bottom front, or “chin” pocket). A lot of the total space is devoted to these front pockets. If you do not want that much space devoted to smaller pockets, then the Shadow Guide series can provide a similar total space (23-33L) divided only into a large main compartment and a generous top pocket. (For the purposes of this entire paragraph I am ignoring flat pockets).

I hope this helps you find the right bag for your packing style.

How is the volume measured? What is the method to come to 25L?

In looking at the dimensions, I see that competitor bags of around the same HWD have more around 30L. I assume this may be due to the amount of material used on the inside of the bag for dividing it up into each compartment.

Synapse 25 25L 20 x 13.4 x 9.1

vs...
Timbuk2 Uptown 30L 19.5 x 11.6 x 6.50
Tortuga Outbreaker 35L 20.3 x 12.9 x 8.2

[moriond]

This is from a 2018 post by Darcy when asked how another product volume was measured:

We currently calculate volume using the ATSM standard (or a slightly modified method): we fill a bag with 20mm (~0.75”) hard polypropylene balls, then remove the balls and dump them into a graduated measuring cylinder and/or we also weigh them (weighing turns out to be a more accurate method for smaller bags/pockets/compartments). For the three dimensions (LxWxH) we use a big set of calipers. So, two different methods. Remeasuring/fixing the dimensions doesn't change the volume.

Thanks sturbridge for quoting Darcy’s post on how they do the measurement.

I have been using my Synapse for a few years now and the way that space is divided in it is quite different from most bags out there. In a Synapse (and Synik) there is the main pocket and then there is the front half of the bag, which is pocket city. The front pockets of a Synapse 25 can hold two 12 ounce water bottles or two Side Effects (in the side pockets), a 16 ounce Contigo thermal water bottle (in the water bottle pocket), AND a 3L Side Kick bag (in the bottom front, or “chin” pocket). A lot of the total space is devoted to these front pockets. If you do not want that much space devoted to smaller pockets, then the Shadow Guide series can provide a similar total space (23-33L) divided only into a large main compartment and a generous top pocket. (For the purposes of this entire paragraph I am ignoring flat pockets).

I hope this helps you find the right bag for your packing style.

The most recent detailed discussion of how dimensions are calculated came in the threads for the Le Grand Derriere. One of the pictures that I showed in a post (#23) in review thread (LGD Logic/Coyote First Impressions also Ursa/Hunter, Black/Red & Wilderness/Coyote!) showed the LGD packed into one side of front pocket of a Western Flyer. In a later post (#31) in that same thread, I quoted some of the relevant statements about how the dimensions were calculated, along with the comment that if the LGD depth were really 6" wide (instead of expandable to 6" maximum size) that I would never have been able to fit it into the Western Flyer. If you visit the linked post where I quote sections of posts from other thread, you can click on the red arrow to the right of the quoted section to be taken to that post in the context of its original discussion thread (I'm highlighting some of the excerpted quote).

We measured the LGD using the same methodology we use to measure all our bags: we fill them with .75” / 20mm hard plastic spheres and pack them reasonably tight. We then measure the tallest, thickest and widest dimensions using a large caliper. The thickest (deepest) dimension of the LGD is just over 6".

However, the most graphic, visual interpretation of this method was posted by Darcy in 08-25-2021 in a thread titled Is the Zeitgeist volume underestimated??

As we’ve talked about elsewhere (but I couldn't find it when I searched, I'm no moriond that's for sure!), when we measure the volume of a bag, we use a modified ASTM standard method: we fill the bag with hard plastic balls to a point that it is reasonably full, then we measure the weight of the balls (having previously calculated the weight to volume ratio for the balls). This gives us and you a relatively standardized view of how much stuff you can put inside the bag.

When the bag is in this state of being reasonably full of the hard plastic balls, we use a large caliper to measure the bag’s extreme height, width and length (we ignore protruding handles, just measuring the bag and any exterior pockets). Imagine, if you will, that we are going to build ourselves a rigid box into which we can easily slide the now filled bag: that’s pretty much what those three dimensions are giving you. If a bag is relatively rectangular, it’s going to fill that rigid box more completely than if it’s relatively curvilinear: think of an Aeronaut (which is square-ish and designed to fill the maximum allowed carry-on space), compared to a Synapse (which has many curved surfaces).

Or, for the sake of illustration, think of a VW Beetle vs a Honda Element:


You can see that the box around the Element is much more filled-in by the vehicle than the box around the Beetle, yet they are pretty much the same size boxes! If we actually built boxes for these two cars and wanted to ship them to you, you can see we’d use a lot more packing peanuts to fill in around the Beetle than we would around the Element.

This fun video further illustrates how much volume is impacted by curved surfaces; it takes the extreme case of comparing a sphere to a cube (both with the same gross three dimensions of 5cm x 5cm x 5cm):
https://www.youtube.com/watch?v=QNpmxGpey_0

Now here's my text comment on the carrying capacity of the Synapse: The compartments in the Synapse are designed to "flex" and occupy more or less room according your usage of the adjacent compartments. So, if you have a modest water bottle, and want to store other water bottles in the top zippered side pockets, or use them for Handy Little Things, or if you repack the bottom zippered pocket of the Synapse so that it holds a very full Travel Laundry Stuff Sack for A30, the walls of that compartment will also flex to give you maximum sharing of space between adjacent compartments depending on how much you've put into them. That's why this is referred to as a Tardis bag that appears to carry more things than the simple stated volume (assuming that your bag is built like a rectangular block) would indicate.

HTH

moriond