This summer I have been working on a number of projects, and decided to give the old NRS Otter a load test. Been thinking about it a while, and finally came up with the idea of using a couple of fish totes full of water to simulate a maximum load. The plan was to gradually fill the totes with water (5 gallons weighs 40 lbs.), and measure the displacement at regular intervals. I still have to collate the data, and I'm not happy with my testing methods... it's going to require a redo later... but the final results were most enlightening. Actually I was shocked at what the boat was able to carry without the floor flooding out (the boat was a 14' NRS Otter self-bailer). The bottom line? I hit 2,000 lbs. and flat ran out of room in the two fish totes I had. I actually had a third tote along for this eventuality, but my support structure, a cargo module from my cataraft, and a sheet of 3/4" plywood, were scaring me. I thought the ply board was going to break in half, it was sagging that much. Also I discovered that the bow and stern sections, which were not carrying any weight at all, need to be weighted equally next time, as they were actually resisting and causing the boat to begin to taco in the middle. Another interesting detail was that the floor was hogged up lengthwise, to the point that I believe it would actually come close to the height of the main tubes if stressed much farther. I believe I could have gotten another 500 lbs in there before the floor would have flooded.
Finally I did monitor the increasing tube pressure and noted a fairly significant pressure increase as the load increased. I believe this is a contributing factor to some of the explosive detonations we've seen in a handful of cases with overloaded packrafts. The fabric is just not strong enough to withstand significant pressure increases that come with overloading. A possible exception to this would be AIRE's new BAKRaft; with an outer shell made of Dyneema. I don't think that shell would explode. More likely, the boat would be overloaded until it submerged, would be my guess.
The point is that the Otter SB in a 14' length will carry much more weight than I previously thought. SIGNIFICANTLY more.
One final item of interest: the loaded boat drafted 12". More details to come, but I thought some might be interested in the sheer load-bearing capability of this boat.
This is what the boat looked like with just a small amount of water in each fish tote. I was careful to fill the totes equally, and took displacement readings every 160lbs. I will publish the data once hunting season is over. I have a hunt breathing down my neck right now and am typing this in the middle of packing...
This is what the boat looked like when the totes were close to being full. When the totes were completely full, the boat drafted 12".