A Modular Riverboat

Discussion in 'Boat Design' started by Sweet Dreamer, Jul 10, 2014.

  1. Westfield 11
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    Westfield 11 Senior Member

    Fiberglass is not cheap either, nor is resin. You are going to want epoxy not polyester, but there is no reason you can't use the cheapest Home Depot plywood instead of marine. If you start cutting and drying trees, sawing planking and then building four boats from those planks you will be into the next decade before you launch. It's all time vs money...... Perhaps you should do a quick off the cuff calculation of how many planks and frames you will need, it might surprise you. Four of these barges built of wood by traditional techniques will take a lot of trees!
     
  2. Westfield 11
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    Westfield 11 Senior Member

    Wood boats did indeed work before fiberglass came along. However they were built from long wide planks of clear straight grained wood and large timbers for frames by craftsmen skilled in complex trades they had spent a lifetime mastering. Joining long planks of wood along their edges in such a way as to keep water out for weeks at a time is not an easy thing, it can be done, but a novice will struggle IMHO. It is also the slowest way possible to get your project onto the water. You will need dry wood that will not shrink, twist or crack as you are building, if you want to build this year you should have cut the trees last spring, planked them and dried the planks over the summer and winter at least. Same with the thicker framing material it too needs to be dry and stable. There will be hundreds of planks in each boat and if they shrink or swell the effects can be disasterous. There will also be thousands of fasteners of some kind and they won't be cheap either. When you step back a bit buying or scrounging cheap plywood might be the cheapest method in the long run.
     
  3. Sweet Dreamer
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    Sweet Dreamer Junior Member

    You're probably right. The plywood route would be the easiest for sure.

    Just for the record, we're expecting this project to take several years to complete. Part of the reason for this is due to the need for lumber to cure. We have solar kilns to speed that process up a bit, but it will still require some curing time. We expect this and have already taken it into consideration.

    What I think I'll do is draw up plans for both methods of construction. Then we can make our final decision based upon the cost of materials, etc.

    Right now I'm only designing the boat. We don't expect to even begin construction on the boat for at least a year. And that beginning may indeed just be cutting lumber for the project.

    So this isn't a rush project. It's a long-term project. If we can realize this dream in 3 or 4 years that would be great. Right now we are just in the design stage.

    In fact, I'm hoping to build some working scale models before we actually build the real thing. So it will be a work in progress.

    I might draw up plans for several different designs before we decide on which one to actually build.

    In the case of these hulls I can easily draw them up as basic frames, then have separate drawings for plywood or planks.

    If I go with planks I'm thinking on running them horizontally instead of vertically. I think that would be especially easy considering the curvature of the hulls at the ends. With horizontal planking no planks need to be curved.
     
  4. PAR
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    PAR Yacht Designer/Builder

    Don't you think maybe some engineering and hydrodynamics understanding is necessary, before you start "designing" anything?
     
  5. Sweet Dreamer
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    Sweet Dreamer Junior Member

    I am an engineer. ;)

    Besides, what kind of hydrodynamics is going to be required to design two very slow moving paddle wheel tugs to push around two floating Jon-boats at a very low speed?

    I chose the hull shapes I did precisely because I know they are already time-tested to be hydrodynamic and stable for the purpose I have in mind.

    It would be silly for me to try to design a better hull shape. These are already perfect for my purposes. They are also quite simple and easy to construct. So I'm off to a great start. ;)
     
  6. fredrosse
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    fredrosse USACE Steam

    Paddle Propulsion

    "I agree, the paddle wheels are entirely an artistic or nostalgia desire. In fact, since that is their purpose they could even be non-functional accessories actually. By non-functional I simply mean that they wouldn't necessarily need to be the propulsion system. But they should at least turn and appear to be working."

    OK, its a given that I have a pre-disposition to paddles, however they do have merit:

    Real paddle propulsion works, and even can have reasonable efficiency, many boats have worked well for over a century with this type of drive system. In my view, fake paddles are just a drag.

    The real advantage of paddles is the very small draft requirements. When I go out with all the other steamboats, they draw 20-36 inches, and constantly foul their conventional propellers with grass, etc. The sidewheeler draws only 8 inches of water.

    Docking a sidewheeler is problematic, but not so with a sternwheeler.
     
  7. Westfield 11
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    Westfield 11 Senior Member

    Fred, where is the rudder on a stern wheeler?
     
  8. Sweet Dreamer
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    Sweet Dreamer Junior Member

    On this little "Showboat" design the rudder is centered under the bow.

    Paddle Wheel Showboat

    I'm thinking that in my modular design where I will be having a full barge in front I may need to actually place steering rudders on the front of the barges instead.

    This could be a design challenge. But I'm sure there are ways to solve this problem. It's certainly something to keep in mind from the outset of the design to be sure.
     
  9. SamSam
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    SamSam Senior Member


    I talked to the owner of this boat and he said he got about 6 MPG which I thought was OK. That's a 4 cylinder engine from a Datsun pickup truck. When he docked it, instead of slowing the RPMs, he would just downshift the auto transmission.

    It didn't steer too well so he added some 6' dagger boards or maybe lee boards for the boat to pivot around, which helped a lot.
     

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  10. Sweet Dreamer
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    Sweet Dreamer Junior Member

    I was actually thinking of using a small 4 cylinder car engine myself. Mainly to save money. But then I thought that a couple of 18 HP garden tractor engines would probably suffice. They'd be a lot smaller and easier to install and design around. But more costly to obtain no doubt. Especially if purchased new.

    Actually if I run across some free car engines I may very well be tempted to go that route. But they would also be quite a bit heavier than the garden tractor engines too.
     
  11. Sweet Dreamer
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    Sweet Dreamer Junior Member

    By the way, the hull of that boat doesn't appear to even be 2 feet deep. It's surely not 3 feet. Those trailer tires are most likely 15" or less. And the boat hull doesn't appear to be any taller than the size of a tire.

    I'll need to look into doing some buoyancy calculations to decide on just how deep to make my hulls. I'd like to keep the decks quite a bit higher than the water level. At least a foot above the water line.

    This is why I haven't put this dimension in my hull drawings yet. I haven't figured out on how deep to make these yet. I'm thinking between 2-1/2 feet to 3 feet just off the cuff. 3 feet would probably be overkill. But it would also make for nice high decks.

    I'm thinking too that I'll have to do some buoyancy calculations based on the expected weight of finished boats.

    Here's a nice little app on buoyancy. The only problem is that this app seems to be quite limited. It only allows for doing solid blocks of wood.

    Bouyancy App

    [​IMG]




    What would be cool is to find an app that allows for the design of a hull made of wood so I can see precisely where the waterline will be visually.

    Of course I can do this calculation just using numbers in a spreadsheet. But visual apps are a lot more fun to use. ;)

    Anyone know of a decent detailed boat-hull buoyancy app similar to the one above that allows you to virtually design a hull and launch it to see it's buoyancy characteristics?

    It would be super-great if they would also allow for the placement of cargo such as engines etc., so it can easily be seen how level the boat will naturally sit in the water.

    It's hard to believe that a sophisticated boat buoyancy app hasn't already been written. Surely there are some around?

    I should be able to design a hull, and then stick weights on the deck to see how the hull sits in the water with various weight distributions.

    I could write an app like that actually. But I don't have the time to do that right now. So I might end up just using a spreadsheet to calculate the basic waterline for my hulls.
     
  12. SamSam
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    SamSam Senior Member

    Of course you have to do some buoyancy calculations based on the expected weight of the finished boats. You also have to add everything else that will be on it, engines, fuels, people, anchors, generators, food, pets, etc.

    And if you build 4 separate vessels and don't have the same weight on each, they will all float at different levels. If you don't have the weight distributed evenly on each, they will all be tilted at different angles both fore and aft and side to side.

    I have photos of that boat under construction and the hull was built pretty close to the way these were. He might even have used these plans or something from Glen-L. Looking at these might give you an idea of relative dimensions.

    http://www.svensons.com/boat/?p=HouseBoats/BayouBelle

    http://www.svensons.com/boat/?p=HouseBoats/FloatAhome

    I know the bottom frames were 2x6 tapered down like in these plans so the whole bottom was a slight vee, and the bottom ply was 3/8". That would be way too thin for my peace of mind.
     
  13. SamSam
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    SamSam Senior Member

    Also take windage into your calculations.

    Where are you going to locate this boat and what river will it be on?

    The trailer was made from an old mobile home frame, so the tires are regular full size tires. You can kind of judge by the truck on the side of the photo.
     
  14. SamSam
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    SamSam Senior Member

    The boat was 8' X maybe 25' or 27'. It wasn't too good for a paddlewheel as the bottom at the stern should curve up, something like the bow. That feeds water to the wheel and keeps it from just piling up on the transom in reverse.
     

  15. Sweet Dreamer
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    Sweet Dreamer Junior Member

    Save for during extreme storms there is never any wind on this river. It is located in a deep valley of heavy forested hills on both sides. You're lucky to get any breeze at all here. No winds that would need to be taken into consideration. Unless, like I say, it's a particularly stormy day. We aren't likely to be using this rig during stormy whether.

    This particular "Showboat" will only be launched during times when the whether has been predicted to be calm. Which is far more often than not in this location during a typical summer.

    It also won't be used to go very far. Probably no more than a mile or two from dock at most. Two miles up or down river would be considered a long journey.

    So the whole thing is designed and intended to be used in a very small area. The river is deep here, and dammed. So the water is very slow moving as well. No heavy currents to deal with.

    It's a really nice secluded area perfectly suited for this type of boating.

    Of course, if we actually build the rig we may be tempted to take it other places as well, being that it will be portable via trailers. But if we take it to other locations we'll take into consideration that conditions may indeed be quite different.

    It could become problematic on a rough lake, a fast flowing river, or in high wind conditions. But for now I'm not worried about those things because they don't exist at the location we're actually considering.

    I would personally be happy to just stick with this one location.

    If people want to take it other places, we'll have to address those new potential risks and conditions and take them into consideration.

    It could be hazardous to try to tie all these barges together in rough water with lots of wind. I don't anticipate that being an issue for the river under consideration. It is characteristically a very calm river. Like I say, it's dammed (no current), and also sheltered by forests in a very deep valley (no wind). So it's a really calm situation. ;)
     
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