Originally Posted by gobigohome
So hopefully all of you knowledgeable buzzards can hopefully clarify some definitions.
What constitutes a flat bottom
Is there a website that contains all the specs on different boats to compare dimensions ie. rocker, kick height, tube diameter, middle compartment diameter ect. And do different manufacturer measure specs any differently. Thanks for all your help
At the river guides shows we would argue these concepts for way way too long. So I think you need to look at it from each manufactures perspective. Therefore I will give you ours. Please compare to anyone else's I will attempt to follow this thread.
Raft rocker - kick are sort of the same thing. but Here is where rocker is different. On catarafts. Some of the Aire models had a huge amount of rocker in them. Rocker is like the rails of a rocking chair, and it does the same thing in the river, it rocks back and forth. Just like if you put flat sticks on the bottom of a rocking chair, it would not rock back and forth. Now if lots of rocker sounds good to you and you are hauling a lot of gear with a cataraft, you may change your mind by the end of a trip because the boat draft is going to be real low, and the hull speed is going to be real slow. conversely, if you are running the boat solo with no weight it will give a wild ride. It also works that way on rafts to a certain extent, but rafts by the nature of the floor do not draft like catarafts, and they would need less rocker to get the same effect. Consider a rocking chair in mud (catafaft )and one on a firmer surface (a raft). So there is raft kick. and that has to do with the amount the end tube section rises up from the same point in the middle of the raft. Different manufacturers measure this in different ways, but we like to use the same refference point. That is the center line of the tube. The kick can all happen in the first section that kicks up, or in the last section that kicks up. There can be many sections that kick up, but we usually use 2 sections. We like to think of cargo capacity, and hull speed performance as a result of kick. Too much kick is ridiculously inefficient, with wind resistance, and it limits cargo space and causes reduced hull speed. Too little kick and you will plow water, but you will have maximum flotation. In fact we are building a raft for an alaska outfitter that has these features because weight and capacity were more important than speed on the class 1 river they are float fishing.
To us a flat bottom is not a good thing. We built a self bailing raft with a perfectly flat bottom, it had no tracking effect what so ever. It sure could haul some gear, but you could not keep it off the cliffs, because it went sideways as easily as it went forward. We now build them with a tunnel effect where the main tubes sink slightly lower and add a tracking effect without taking too much of the cargo capacity away.
We build our floors with drop stitch fabric. I beam inflatable floors actually add tracking effect without having to be as high on the main tubes. Those floors also extend downward a lot when the boat fills up in a big hole. So you get the idea that everything is give and take here.
We invite you to look at this web site if you would to read about how we engineer out rafts. We feel we have the best possible outcomes for these design issues.
By the way, the raft we are building for our Alaska outfitter has only a 2 inch kick. and it has a perfectly flat bottom. So His performance criteria is gear and people and light weight. He is not worried about how well it tracks, or any whitewater or hull speed performance.
Here is the Jpeg immage of the computer model of that latest raft.
If you are still interested in getting way more information on this than you ever thought possible. visit this web site,
download the edrawing viewer, and some of the edrawing files that seem interesting. open the files in the edrawing viewer, push the play button, and the immage will rotate in 3D. There are a lot of other things you can do with edrawings too. However you can not design with it. you can only collaborate with us on design. In otherwords this is what I like, this is what i do not like. that sort of thing.
When it comes to information about rafts... you may as well go with the guys who hold all the cards... The wild cards at JPW.
thanks for reading this.