Riverboating

Where's? Limbang........ u sound like an asian to me ........ or one of the charlies ........

 

Borneo welly, best check your history (some forty years back)

 

'Fraid so Bergalia and we all know who started the VW off don't we, cusin Adolf (Don't mention the War)

Actually I wouldn't ruin a good Landy on a fishing trip when there's a perfectly good Jeep to tear the hell outof and oh yes whilst you were on holiday I was made an Honary Yank (some people will do anything to win, and all people have their price, I'm just rediciously cheep is all)

 

I knew that........

 

In Indonesia...... Walrus teeth are very expensive ......... can i have the pair in your mouth heard it is cheep!

 

'fraid not Welly, I'm not THAT cheap!

 

justkiddin man no hard feeling

 

Esteveo;
This thread has attracted some comedians. O.K. humor is good but it does not get the answers you asked for.

I suspect that the Mud Buddy or similar will be your most practical propulsion method. Even with one of those you are going to need some poles for getting off very shallow places.

You are going to need a very shallow draft boat to get through those thin water places. That implies that it might need to be wide for its length. First make an educated guess at what the total weight of the entire outfit will be. The boat, motor, passengers, provisions, water, booze, and other stuff. Just for example sake, say the whole lot is to weigh 550 pounds. Now use following little number to tell how many cubic inches of displacement you will need. That is to say, the boat must push a certain amount of water out of the way in order to float the 550 pounds. The number is 0.03611 O.K. ? Now divide the weight, 550, by the number 0.03611. That gives us 15,231. That is the number of cubic inches of water the boat must displace. You can substitute any weight you might decide on. Continue to use the constant 0.03611 to do the division arithmetic.

We are half way there. Lets say that you are going to build a 18 foot boat. For the river boat you will want to raise both ends quite a bit above the waterline. Look at some of the float boats typical of northwest river use. They look like rocking chairs. Because of the extreme bottom rocker. Lets say that only 12 feet of the boat bottom is in the water. That is, the waterline is twelve feet long or 144 inches. Now divide the number of cubic inches by the WL length. 15,231/144= 106 square inches. That is only the area of the average section. Not the center section or any other section. We're not quite there yet.

If you figure to make a boat with the front end pointed and the back end about 60% of the maximum beam you can make a wild assed guess at the prismatic coefficient. Sorry about those technical sounding words. Never mind, they're just words to describe the percentage of the center section that will be encompassed by the whole underwater part. You are for sure going to build a flat bottomed boat. A very durable flat bottom. The prismatic for a boat like that will be in the region of 0.55. Thats close enough for preliminary estimates. Now. We found that we needed an average section area of 106 square inches. Divide 106 by the prismatic as before ..... 106/0.55=192.7 The mid section of the boat will need (round off) 193 square inches.

Figure out what minimum draft you can get away with. Let's say you can live with 4 inches of draft. Divide 193 square inches by 4 inches of draft, and you get a bottom beam of 193/4=48.25 inches. This little bit of arithmetic will get you into the ball park as dimensions go. You can see that if you wanted to float on 2 inches of water you'd have to make the bottom twice as wide or make the bottom longer than the 12 feet in the example.

Different boats have different prismatics The Jon boat type you mentioned is basicly a barge with rockered ends. They have larger prismatics on the order of 0.65 or more. If you had a box that was completely rectangular, then the prismatic would be 1.0 I would not recommend a box, but a john boat type might be a fair compromise. With a prismatic of 0.65 the boat could float in 3 inches of water if it had a botom width of .....106/0.65=163 and 163/3" = 54.3
bottom width.

Have fun with the estimates but don't get into trouble by assuming that everything is as simple as this exercise. Simple boats are not hard to design. They are however, hard to design well.

 

Incredible and cool.

 

I posted a message above that included some arithmetic. The aim was to help Estevio, or others, get a handle on what kind of boat he could figure on. Re-reading my own message, I'm not sure that I did a good job of it. I'll take another run at the subject. I had a couple of private messages that asked what in hell I was talking about.

All you knowledgeable boat guys out there are asked to forgive this rudimentary excercise. It is a fact that many people who have a genuine interest in boats are not conversant with many of the design basics. That, by no means, implies that they are dummies. I'm only trying to encourage them to learn more, so that they are less likely to make expensive mistakes. Plenty of good books on this and other pertinent subjects.

Boat designers use a lot of terms to describe a certain shape or size by using a number. Reducing a design to a set of numbers, makes it easier to compare one hull form to another. Prismatic co-efficient is just one of the many terms. What it means is this:.... Use you imagination a bit here.......You have a piece of wood that you will carve out to the shape of the main underwater section of your boat. The main section usually occurs at about the mid point of the boat or perhaps at little aft of the middle. Just imagine a bread slice across the middle of the boat. We call that a section view. Now look at the part that will be immersed. At this point we don't care about the top sides of the boat as we are trying to figure out if the thing will float on the designed lines.

Carve the piece of wood from end to end in the exact shape of the underwater mid section. In that condition there is 100% of the wood in place.

Boats have some shape. The front and back is usually narrower than the mid section. Not only that but the boat may curve upward in the front or the back or both. Imagine whittling away at the wood block until it looks like the underwater part of the boat you have in mind. You'll have a lot of wood chips when you finish. Let's say you have chips that amounts to 40% of the original piece. That would mean that 60% of the wood is left and the carved block looks like the underwater part of the boat you have figured on. The prismatic co-efficient is 0.60. If you'd carved away exactly half of the wood then 50% would remain and the PC would be 0.50. No carving at all and the PC would be 1.0 or 100%.

The number 0.03611 is simply the number of pounds that one cubic inch of fresh water will weigh. Salt water is a little heavier so the number will be a bit larger. (0.0370) Grab the calculator and multiply 0.03611 by 1000. You will see that 1000 cubic inches of fresh water will weigh 36.1 pounds. You can make a pretty good guess of how much a floating boat weighs by using this method. All you need to know is the approximate PC and some easy arithmetic.

Estevo needs to tell us about the conditions in his river. Does it have a lot of hidden rocks like the Rogue river ? Is there a lot of white water ? If the river is really big, how much chop is to be expected ? Finally, how fast do you wish to go. Speed requirement will largely influence the shape of the boat and the power needed. If your river has a lot of hidden obstacles, like rocks, Please try to disabuse yourself of the need for speed. You'll live longer that way.

 

These links might give you some ideas. I would definitely suggest you look at marshrider, as it is a paddlewheeler that could allow for a really shallow draft. It's pretty darn cool.
www.marshrider.com
www.teampersuasion.com
www.ronniesairboats.com
http://www.airboat-transportation.com/muddhogg.html

Also, I found this concept interesting
http://www.mokai.com/

Good luck.

 

Yes that is interesting.
http://www.mokai.com/slideshow/slideshow.htm

 

What most of these guys are thinking is drift boats. That is not what you want. I would build something along the lines of a jon boat but wider to lessen the draft and some good hefty strakes on the bottom to fend off the rocks and sand bars. You could easily run this with an O/B with a jet drive instead of a prop. Yes, you are going to suck some sand and rocks, but they have been using jets in the rivers in Washington and Orgeon and Idaho for decades and they do the job better than a prop on rocky rivers.

Besides the North Platte is so wide and shallow in some places that if any thing goes wrong you just get out and walk home. Ever here that saying, "A mile wide and an inch deep" They must have had the North Platte in mind.

 

kach 22i

I own 3 of those boats and just love them. They have taken me many places in skinny water. I will have one for the rest of my life. MOKAI paddle no more. Up the creek with out a paddle? Hope you are in a MOKAI.