Field Report – Sea to Summit Ultra-Sil Dry Sack

Review Date: July 13, 2006

Name: Pat McNeilly
Age: 43
Gender: Male
Height: 5’ 8” (1.7 m)
Weight: 165 lb (75 kg)
Email address: pmcneilly@osophs.dhhs.gov
City, State, Country: Gaithersburg, MD, USA

Backpacking Background:
I have been hiking for at least 20 years but backpacking for only the last three years.  Most of my backpacking is done as overnight trips and occasional weekend and weeklong trips.  My typical packweight is approximately 18 to 20 lb (8 to 9 kg) before food or water.  Most of my backpacking is the three season variety in the mountains of Maryland, Virginia, and West Virginia.  In addition to backpacking, I also fish, hunt, and have been involved in disaster relief.  As a result, some of my backpacking equipment gets use in a number of different venues.

Product Information:

Product: Ultra-Sil Dry Sack
Size: 13 Liter (793 in³)
Manufacturer: Sea to Summit
Year of Manufacture: 2006
Color: Light Blue
URL: http://seatosummit.com
MSRP: Not listed

	As listed	As measured
Weight	1.4 oz (40 g)	1.3 oz (37 g)
Length	21 in (53 cm)	21 in (53 g)
Diameter at base	8.5 in (21 cm)	8 in (20 cm)
Diameter at opening	12 in (30 cm)	12 in (30 cm)

Product Description (as described on the manufacturer’s website):
According to the manufacturer’s website, the Ultra-Sil Dry Sack is made of a Siliconized Cordura material, which is a waterproof nylon fabric.  The manufacturer goes on to say that Ultra-Sil nylon is a polyurethane coated Siliconized Cordura which allows for better waterproofing and greater durability.  Ultra-Sil Dry Sacks are reported to be more than 50% lighter than other popular dry sacks.  The product uses a Hypalon roll top closure with a stiffener at the top for a watertight seal.  The material has a slippery feel for easy packing and is nearly transparent for viewing the contents of the bag.  The manufacturer indicates that the seams are double stitched and taped.

Field Conditions:  
I have used this product on a range of trips including a weekend trip on the Appalachian Trail in the Pine Grove Furnace area of Pennsylvania and dayhikes in the Shenandoah National Park, the Norvin Green State Forest of northern New Jersey, and suburban Maryland’s Cabin John Trail.  I also took this bag along on a week long trip in the George Washington National Forest in central Virginia where I encountered three days of very heavy rain.  The elevation on these trips varied from 200 ft to 3200 ft (60 m to 1000 m).  The temperatures I encountered on these trips ranged anywhere from 48 F to 87 F (9 C to 30 C).

Product Review:
To ensure that I was able to evaluate the watertightness of the dry sack, I ran a series of tests looking at how waterproof the bag is.  I filled the bag with gear (sweaters and fleece) and closed it as directed by the manufacturer and submerged the bag in a tub filled with water.  During this test I kept bearing in mind that the instructions with the product indicated that water may get in if the sack is submerged.  I held the bag under the water for 2 minutes.  I noticed that a few air bubbles could be seen rising to the surface when the bag was submerged.  After removing the bag from the water and drying it with a towel, I opened the bag and found that water had made its way into the folds at the top of the bag around the seal but no water actually entered the bag.  I repeated the test by partially filling the bag with and without the top being rolled tightly against the contents and (each time the top was folded at least three times).  I found that a small amount of water was able to get into the bag if the top was not rolled tightly against the contents.  This was not a large amount and I felt that after being submerged for two minutes the contents were still protected by the bag. 

I will note that in all the cases where I attempted to submerge the bag it floated and had to physically be held under the water.  I took this as a good sign and felt that submersion of the bag is not going to be easy in the field unless it is being held under water by another object.  A bigger problem may be that one would have to deal with a bag floating away rather than the contents getting wet.

I also tested the Ultra-Sil Dry Sack in my home shower to gauge how well it might deal with a heavy rain.  I placed items in the bag and closed the bag in three different ways including (i) folded at least three times and tightly closed against the contents; (ii) folded at least three times and loosely closed against the contents; and (iii) folded over only twice and loosely closed against contents.  For each test, I placed the bag in the shower at full power for five minutes.  In all cases the contents of the bag remained dry.  I was very impressed with the results of these tests and believe that the Ultra-Sil Dry Sack will keep items dry even under some extreme conditions.

In addition to these tests, I used the Ultra-Sil Dry Sack to keep my down sleeping bag dry during three days of intense rain (described in the media as a 200 year rain event) in central Virginia.  Any gear that I carried which was not in an absolutely watertight container ended up wet.  The Ultra-Sil Dry Sack kept the sleeping bag dry during this period which allowed me to at least have something dry when I went to bed.

After using the sack on a number of trips I have found that the sil-nylon material has shown little wear despite being pulled and pushed in and out of various packs, as well as being tossed about on the forest floor and rocks.  I have not noticed any stress along the seams and the taping of the seams is intact.  I was initially concerned that the closure system of the bag could cause stress at the top of the bag and lead to a leak.  I have not encountered wear at the closure to this point. 

I have found that the sil-nylon fabric allows the sack to easily slide into a pack.  The loop formed when closing the bag also acts as a convenient handle for hauling the sack around.  The size of the bag makes it very useful for packing items in a large backpack or as a liner for a smaller day pack (e.g., 1000 in³ (16 L) pack).  However, I felt that it was a bit too large for lining my lumbar pack (which has a 600 in³ (10 L) volume).  The bag fits into the lumbar pack without a problem but completely expelling the air when closing the Ultra-Sil Dry Sack always seemed to be difficult with the smaller pack.  The problem would arise if the sack was already in the pack and I was trying to expel air out of the sack.  I had less of a problem if I removed the sack and closed if before pacing it in the lumbar pack.  I still found that I needed to make sure all the air was out or it would tend to take up more room than necessary.

 I have primarily stored either clothing or a sleeping bag in the sack.  If soft materials are packed inside, the only problems I found were that I had some problems with expelling all the air from the sack before closing it.  I also found that the portion of the opening with the stiffener tended to fold down toward the inside of the sack and needed to be straightened and then aligned with the Hypalon seal before folding.  This was is only an annoyance and there was not any problem with sealing the bag properly.  I did pack a stove and a windscreen in it for one day during my weeklong hike.  Although I did not have a puncture or tear, I was not confident that the edges on the stove might not penetrate the fabric.   The fabric is thin and has stood up to a normal amount of use but the stove’s sharp edges had me questioning whether it was a wise idea to use the sack for that purpose.  I also wanted to have an intact sack for at least a portion of the test period.  I will continue to test the Ultra-Sil Dry Sack with objects other than clothing or a sleeping bag to get a better feel for how it stands up to rough objects.

I had occasion to look for items in the sack during both fading light and dark conditions with a flashlight.  I was usually looking for items of clothing.   In these instances, I was able to view the items I needed through the fabric.  I felt the light blue color of the fabric helped to ensure that I could see the various items inside.

Test Plan:
I plan to continue to monitor how well this product keeps moisture out with a special eye on areas that may show signs of wear.

I plan on continuing my monitoring of the durability of the sack and will be looking at the following:

●    How well does the bag handle normal abrasion?
●    Can the bag handle objects with sharp edges?
●    Will the seams and their taping show signs of stress from being packed too tightly? 
●    Does air trapped in the bag play a role in stressing the seams?
●    Does the Hypalon strip wear after repeated use and allow for an inefficient seal?
●    Can the plastic stiffener pierce the nylon fabric?
●    Does the buckle remain closed?  How easy is it to release the buckle?
●    Does the fabric degrade or become more opaque after being exposed to sunlight?

Some other things that I will continue to investigate include:

●    Will the bag’s coating help with loading and unloading it from a pack?
●    Is it better to have the bag full when closing or is it difficult when half full?
●    How useful is the bag for other purposes such as hauling water or washing out clothes?

Summary:
The Sea to Summit Ultra-Sil Dry Sack is a very light weight item that appears to be sturdy, and well constructed.  The sealing mechanism folds easily and creates a very water tight seal.  The fabric of the bag appears to be durable and strong and which also allows me to identify items inside the bag.

Things I like:

    1. Light weight
    2. Transparent fabric
    3. Simple closure system

Things I don’t like:

    1. Difficult to expel air when partially filled
    2. Plastic stiffener tends to fold inside bag 

I would like to extend my sincere appreciation to Sea to Summit and BackpackGearTest.org for the opportunity to test this product.