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Cataraft Design FAQ

Which is safer, single tube design with baffles, or double tube design with tubes side by side?
I think that there is a safety advantage of the single tube design. Here is why. When we have something real nasty in the river in class 4 or 5, It could put a hole in both tubes on a double tube design. I even know of one instance where all four tubes were lost at the same time. The single tube design will only loose one half. Actually when properly inflated, the cone shaped baffle in out cat tubes, moves part way into the deflated section, and it is only like loosing a third of a tube, even though the rest of the tub is rather soggy, it can be safely rowed to shore.

There is a story about two customers who were boating the Crystal River in Colorado. They both had Daddy Cats. The first one was surfing in a reversal on purpose and having fun. It must have been a good hole, because his buddy did not see him in there, and came down right on top of him. The motor mount on the back put a good size hole in the top of the first Cat. It deflated very fast, and he had to make it out to shore in Class 4 whitewater. He informed me that he had no problem doing this, but I am sure that his skills were challenged at this point.

The amount of surface area on the water also has an effect on the ability of a Cat to punch through a reversal. Even the guys at AIRE will agree, and they put it in their brochure. AIRE calls it the awesome hole punching power of the single tube design. There is simply less surface area for the water to act upon, so the boat punches through easier.

PVC inflatable boats are now available with or without bladders. Could you explain the difference. What are the advantages and disadvantages?
Many manufacturers are using unsupported fabrics as a bladder inside of a coated fabric. There are some advantages to this and some disadvantages.

Advantages include: There is one more layer of material to rupture, and this may add a slight amount of security to the owner. The outer shell does not have to be air holding, and can have a heavier substrate, or a lighter substrate, or a cheaper substrate. It cost money to get fabric to hold air. In some instances a new bladder can be added and a rip sewn up to make a repair, if an owner or boatman does not know how to repair with glue or hot air welding.

Disadvantages include: The use of a zipper so that the bladder can be installed. Zippers are prone to failure over time. The accumulation of mud and moisture between the shell and the bladder. This causes the boat to become heavier, even after it is heavier to begin with. If a rip does cause the bladder to fail the bladder and the shell have to be repaired. This results in twice as much repair work. There is some loss of coating adhesion when using heavier base fabrics. This means that seams may be prone to failure, even though the rip strength of the base fabric is high.

The fabrics we use at Jacks Plastic Welding are of two weights. Our 35 oz per square yard fabric has heavy weave, with good coating adhesion, air retention, and excellent tensile strength. we use this material in all of our inflatables. We also use 42 oz fabrics that is installed as double bottoms on our expedition cat tubes. In this way we build a far superior boat by using all of the best properties of these materials to the best advantage.

What are the advantages and disadvantages between highly rockered and straight tube cataraft designs?
Stability, maneuverability, and load capacity are the main issues when it comes to cats. our most maneuverable cat is the flyer cat, because of the rockered style of the tubes. The shape of this boat is excellent for surfing, and playing on the river. In fact Micro cats that are even shorter are very popular in some parts of the country. Our Cutthroat is becoming a popular play style cataraft, and we are building micro cats with lots of rocker for Big Wave Dave's in Spokane Wa for the same reason.

If you only put one set gear load on a cat then it could be designed for the ultimate performance. I have a bias against doing this because it takes from the usefulness of the craft. That is one reason why we have not built more fully rockered tube styles, in our larger models. The styles that we have work well in an all around way. If you are doing serious class 4 plus or 5 rapids, then you will thank yourself for that stability. The ability to blow through a hole that stops and turns the other boats sideways or flips them will be appreciated more than the ability to spin on a dime. This attribute also gives the boat more cargo capacity. If a boat is loaded too lightly, then it will not have the momentum to blow through holes. If the tubes are too big the surface area of the tubes will add to the problem. If the load is too heavy the boat will sink very far into the water, and compromises the ability to turn.

Adding a little rocker to the boat does aid in the ability to spin. There will always be some give and take. For a expedition size load, rocker will work against you. Your boat will be down deeper in the water and will have no more ability to spin because of it. Rocker is OK for day tripping, but I prefer to work a little harder When it is a light load and work a lot less when it is a heavy load. There is a problem at the bottom of Cataract and the San Juan where the river bed is silted in. If a boat sinks too far in the water, then it will drag on the bottom in the low water times, and everyone will have to get out and push.

New Boats for 2001 are the Royal Flush designs. They have a modified rocker shape. This means that there is rocker on the front and back, and a straight section in the middle. We feel that this is a good compromise for a lot of customers. Especialy those who wish to have a good performing boat under a medium gear load. The Royal Flush is estimated to carry about 100 lbs less than the counterpart Daddy 25, or Daddy 28 at 6 inches of draft.

Here is another Idea. If spin and cargo are important, consider a daddy 28 inch diameter. The 28 sits higher in the water, and therefore spins much easier. The load capacity for draft is much higher, but the drawback is price and wind resistance is greater too.

Performance is an issue of give and take. I am sure that our competitors boats are capable craft with the right frames. However some will do better in some instances than others and the other way around depending on the conditions. For these reasons, I lean toward sacrificing the ability to spin for the ability to do more with the boat. It seems obvious to me which issue is more important.

Once again this is personal bias, and it does not have anything to do with the reality of how other boaters enjoy their sport. Keep in mind that I have been a guide on the Grand Canyon, and Cataract, That I have run motor rigs and 22 ft cats with 36 inch diameter tubes (called snouts used at least since 1969 in the Grand Canyon). There lies my bias; to get back to the Grand Canyon, with enough food and beer to do another 21 day trip and still have ice in July, and still have the ability to do a low water trip down the Upper Animas. If you agree with this philosophy, then our boats are the right boats for you. if you do not agree, write to us, so that we can provide the kind of boats that fit your needs.

How long is the glue good for on my raft before I need to reglue the D rings?
The majority of our older boats have not experienced any glue failures. The glue is softened by the plastisizers in the vinyl, by age, and by heat. Humidity also may have an effect on how soon the glue goes bad. Some of our boats have been in the tropics in high humidity for 7 years, without signs of trouble.

If your boat is over 5 years old, we recommend taking a little extra adhesive with you, and keep checking those D rings especially on hot days. Do not be afraid to ask us about the warranty that may result from the our use of improper glue mix ratios. Write to us if you have a problem.

Please note: All boats built in 1999 and later, have all the D rings RF welded in place. Therefore the new boats from JPW are not prone to this problem. We have never built a boat where any glue was responsible for maintaining the air chamber integrity. If you are running an older boat, please take extra straps in case you need to strap directly around the tubes for extra strength. This technique can elliminate the need for D rings.

I want a Cat boat that is light weight for Class 4 plus white water, and one that doesn't get punctured easily. What do you recommend?
Weight is an important factor in the higher class of white water. I will assume that there will be a small gear load, and that there is a very limited number of passengers. If this is the case then our standard Cats are usually very adequate for most customers. However commercial operations require a high passenger to guide ratio, and they have a tendency to load their boats much heavier with passengers than do private individuals. For these reasons, and because they can not afford down time, we recommend installation of double bottoms on commercial rafts. Still there are a few companies that run the Upper Animas that do not use double bottoms on their Cat boats, and some of those tubes have 8 years of use. Keep in mind that the Upper Animas has Rail Road Iron, and fresh rock slides. I recommend taking an extra tube in the party even though there is a double bottom on your boat.

The double bottoms that we do are very tough. They are designed to take extreme point loading (more about that later) and are constructed in such a way to actually limit the tearing of the fabric. In this way when there is a hole, the boat looses air more slowly, and can be maneuvered to shore. I would also like to point out that there is nothing that will sustain abrasion from coral reefs. If you intend to drive or sail your inflatable across coral reefs, please install a double bottom. Let the bottom take the abuse. It can always be recoated with urethane at a later date.

Urethane Coatings
Flexane and Flex tough are two urethane coatings that can be used to both seal and to add material and toughness to the bottom of Cat tubes. This Urethane based material is very abrasion resistant, and in many cases it can be thick enough to offset the effects of point loading that would put a hole in a boat. By the time the boat has ridden over the sharp point, the urethane coating has not been cut through. Please be aware that application of solvent based urethanes is NOT USER FRIENDLY. Know what you are dealing with, and the hazards associated with the use of these chemicals

Point Loading
This is a term that we use to describe what happens to PVC cat tubes when there is a tear in the fabric. The theory of point loading is important, because it is a bigger problem on cat tubes than on conventional rafts, because Cat tubes ride lower in the water. Basically Point loading is when a boat rides sideways over a sharp point, and half of the entire Cat boat's weight is placed on that one point. If it is a sharp enough point, and there is enough weight on the tubes, then there will be a hole in the boat as a result of this incident. The point load is greater as the tube is lifted higher and higher out of the water until half of the weight of the tube is on that one point. That is why most holes are within 6 inches of the bottom of the boat. Of course the velocity of the river and the sharpness of the rocks have a lot to do with this happening. For instance. A very low water trip would cause the boat to stop and not ride over the point. There is not enough momentum to force the tubes over the point. There seems to be more rips in tubes in the upper Animas in medium flows than high or low flows, because the boat still has momentum, and the rocks are getting exposed. Keep in mind that momentum is weight and speed, so if you are doing a low water trip with lots of gear, your chances of riding up on top of a sharp rock are greatly increased because of the gear load. It is also important to keep in mind what sort of rocks that you will be encountering. The Grand Canyon for instance has rapids that are formed by sedimentary rocks that have moved down the side canyons to stop up the main channel. These rocks are worn smooth by the time they reach the river. Quartzite inside the Granite that is near shore is a much more immediate hazard, and parking a boat is the only place that I have ever put a hole in a boat in 45 grand trips. This happened three times. One in Hypalon, one in Neoprene, and one in PVC.Conversely, the rocks in the Piedra river have not been the stream long enough to get smooth, and care should be taken to keep the load as light as possible. This is a good reason to know a little about the geology of a region before attempting a descent.

The vast majority of Cat tubes that we produce are made without double bottoms. We see very few of these come back for repairs. Double bottom fabric is 42 oz fabric with a very heavy denier They add about 60% more weight to a set of tubes, and they are glued on a bias. This bias gluing aligns the fabrics so that there is 50 % more rip strength. A rip is hard to continue through a bias in a fabric. This option is rather expensive, and careful consideration should be given to weight, and cost. Remember transportability is also compromised by using a double bottom.


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