Self Bailing Whitewater rafts and silt

JPW Self Bailing Whitewater Rafts and Silt Buildup

For every combination of design features, there are positive results, and negative results. This is so very evident in an area that is as complex as white water rafting. At JPW we believe that the positive results of our designs outweigh the negative results. Because our products are made in the USA, we can solve problems when they come up. Often those problems are not obvious to us even if we have been using a design for years. We want to assure our customers that we can and will solve design issues when they arise. We are located in the South Western River Zone where anything is possible.

Here is a good example of what we are talking about: 20 years ago we made one of our first dragon fly designs for ourselves. It had some issues, and we changed some things over the years. However one of the things we missed was silt buildup between the inflatable drop stitch floor, and the main floor. This was not a problem for us because we seldom get on the river during the high runoff, high silt content time of the year with this boat. We were more likely to take a cataraft during the high water. We also had some other kinds of catarafts with self bailing floors that did not have the same construction issues. The bottom line here is that we know a few things, and we miss a few things.

So let’s talk about silt build up, and why we have not really missed it, but perhaps did not pay enough attention to it till this year.

We were convinced that the force of the inflatable floor pushing against the main tubes, would keep the volume of water down in between the main floor, and the inflatable floor. We are still convinced of this. Our boats do not carry a lot of water weight with them where there is no silt in the river (more info when you read about John Feinbergs raft retrofit). All rafts with our Drop stitch design that are used by Fishermen, do not seem to develop this problem, and there are no complaints from these customers, or any customers who boat on Clear rivers, because of this issue. There is always a small amount of water between the main floor and the inflatable floor. A fact we addressed that by putting some drain holes front and rear in our rafts to let that water out when the boat is picked up to be taken to the trailer. We expect less than 5 gal to drain out, but that is 40 lbs. you do not need to carry to the truck.

This first image shown, is one of Greg Ward’s boat recently purchased from Colorado Love Outdoors in Cortez Co. He took it down the Delores. The first day he was very happy with the boat. There was very little silt build up in the bottom because McPhee reservoir was filtering out all the silt from the river, and that is where one can start. We also went down this section of the Delores with our 20 year old dragonfly, and had no silt buildup in the bottom of our boat. However after a few more days the silt content of the river increased, and this was the result of that silt build up in Greg’s Boat.

So what exactly is happening here? After experiencing this situation from a couple of different customers, we have come to this conclusion.

This picture shows a small buildup of silt.

This picture shows a larger buildup of silt, as the silt gets washed clean, and the heavier sand settles in between the main floor and the inflatable floor. Silt is heavier than water, and sand is heavier than the mud in the silt. Sand and the heavier elements of the sediment collect at the bottom of the floor. This extra weight pulls the main tubes inward, making the pocket even larger. When the pocket gets larger more silt can get deposited in this area, and more heavy parts of the silt settle out and lighter elements like mud wash away. The problem makes itself worse over time. I think it is important to note that the inflatable floor floats more readily on top of the sand trapped between the floors because the sand is even denser than the water is.

These problems have been noticed on high water Cataract canyon, and the lower stretches of Delores. However the problem is more pronounced on the San Juan River. On the San Juan the sediment is so intense that we get a phenomena called Sand waves. These waves of sand are caused when sand is deposited in the river bed with such speed that if forms waves of sand along the bottom of the river that actually move upstream. The sand is deposited on the upstream face of the wave, And sort of resemble sand dunes under water. These can be fun to run, and can reach over 6 feet high with a feature where the distance crest to crest is less than the distance from trough to crest. They can be challenging in small boats, and can pop up and disappear in 15 minutes.

Evolution of the main floor bailing holes:

Scott Japhett took his 16.5 ft. raft down Cataract at high water, in 2010, and experienced a lot of sediment build up in between the main and inflatable floor. His boat did not have bail holes on the side. We did not put new bail holes in that boat, but we did not hear any issues about it afterward. I had a chance to fix a minor leak in the inflatable floor in the spring of 2016, and the issue did not come up. We thought it was not going to be an issue, and maybe there was something else that lead to the problem like an underinflated floor or something like that. We did not pursue the issue.

John Feinnberg was the next customer to have this issue, and it happened in 2011, when we had the last big flush of the San Juan, and a large sediment load in the river. We put more bailing capacity in John Fienberg’s 14 ft. raft by installing more bail holes along the side in the middle of the main floor. Since that time the boat has navigated the Upper Animas in high water, and The Middle fork of the salmon in low water. However that boat has not been on the San Juan with Sand Waves, or a large sediment content since that retrofit. We thought the problem was solved.

Royal Rose purchased a boat from us, and it did not have bail holes in the middle of the main floor. (Our big mistake.) It went down the San Juan during the high sediment flow and this boat suffered terribly from sediment build up. Once again we thought that the problem would be solved with more bail holes in the middle of the floor near the outside.

Finally Greg Ward talked to us the other day about how his boat operated, and I think we are finally ready to offer the correct solution. With all of this information, it seems easy for us to draw some conclusions.

The easy fix:

When you look at Greg’s boat, with the understanding of what is happening, it just seems to make sense that a couple of well-placed bail holes in the bottom of the main floor near the center will do the trick to keep the sand from accumulating in that area. Many good solutions are easy solutions.

After applying this fix to Gregs boat he was able to take it down the Delores River and this is his report:

Wanted to let you know that I had the raft out last week on the Dolores and it worked great! I think the extra holes in the bottom floor have made a difference and allow the soot/sand to drain. I do love this boat!

Greg Viditz-Ward

may 10, 2017

What are our competitors doing about this situation?

Maravia, Sotar, Hyside, and NRS all have laced in floors that do not have this pocket where sediment can collect. Their floors are either straight drop stitch or I beam (like a heavy duty air mattress) construction. These floors have more drag associated with the design. This drag is what we at JPW are trying to engineer out of our self-bailing raft floor systems.

Aire- uses a zippered pocket where an I beam style bladder is installed. In silty rivers, zippers fail more often. The pocket has holes in the bottom that will allow the silt and water to escape. I do not know how effective this is in relieving the problem caused by a sediment load like the San Juan River. I can only imagine that a good portion of sediment is retained in the pocket, and there is a serious amount of maintenance required to get the boat cleaned out at the end of a season, or after a trip like the San Juan. Of course zippers tend to fail in silty rivers, and it is not painfully obvious where the extra weight is comming from when the silt is hidden from view.

Star – Star inflatables has tried all kinds of things from laced in I beam floors with similar designs to Aire, to straight laced in I beam floors. So they have had the same issues as all of these competitors.

JPW is the only raft manufacturer with a curved drop stitch floor that fills the entire floor compartment. Without the sediment build up we are still the fastest and lightest and most durable all welded boats on the water. All air holding seams are welded there is no glue.

A couple of final questions: What about the vulnerability of the floor right over the center sediment bail holes?

If you plan to run some rivers that have sharp lava or travertine that can cut through the 42 oz. bottom material, we suggest that you think about putting a small wear patch on the bottom side of the inflatable floor if you have these bail holes in your main floor. Otherwise simply monitor the wear on the inflatable floor when you clean the boat at the take out. It should last for a very long time.

Should everyone get the sediment Drain Holes for their rafts?

We do not think so. If you are planning to run the San Juan at high sediment flow, and you want to put a couple of sediment bail holes in the bottom, then we think that is a fine idea. You may consider reinforcing them with patches on the inside of the boats main floor. Or we can install them at the factory at no extra charge. If the flow on the Colorado, Green, Yampa, or Desolation is medium or low, the sediment build up may not be an issue. If you live in Montana, or the Northwest, you may not want to do this at all.

Is there any loss of performance by adding the sediment holes?

We really do not think so, but the holes can be patched over if you are not comfortable with the performance you get.

What can I do to make sure a JPW self-bailing system works as best as it can?

On high silty rivers, make sure that the floor is tight. It is after all just like a stand up paddle board, only that JPW ISUP and raft floors are all welded. The pressure of the floor on the main tube is what keeps the main floor tight against the inflatable floor.

Keep in mind that this is the best way to get the fastest lightest and best performing raft on western rivers today. We have other floor designs that we are working on and we will let you know what our customers think of those also.

Thanks for reading this article.

Jack and the crew at JPW

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