Twin hull sternwheeled landing craft

I am building a twin hulled landing craft, shallow draft and sternwheeled. The hulls are finished at 61 feet long, 60 inch diameter 3/8 thick steel with raked bow cones. Hatches and bulkheads are fitted every ten feet.

I have calculated a 22" waterline loaded, and a 8.9 knot hull speed. This will be a river and protected waterway vessel.

I'd like to hear from the brain trust here regarding proper length to beam ratio. I have planned a 20' beam, but have not commited the design to it yet.

Any ideas?

Ryland

 

What do you want to carry on it....

 

Is the middle deck lowering? Sternwheel how? Can you visualise the idea a bit more?

 

modular and multipurpose.

I have no idea the limits of what might be carried. I started looking for an LCM to meet the requirement. I thought it might be cool to have a boat that can convert from pleasure (bring the Airstream on board) to work boat by loading appropriate deck equipment. I decided to build rather than buy.
The dream to have a boat big enough to play volleyball upon is a reality now and the only way to justify it with a straight face is to give it some commercial functional possibilities.

It will be built to disassemble for over the road movement to the place of launch because my roads will not accomodate the assembled vessel.

I expect to make a 'Swiss Army Knife' of river boats. Form will follow function. I've never done anything like this before but I think I can. If it's as much as an adventure as some of the other things I have built, then it will be worth it.

Any constructive comments welcomed. My next design decision is how wide she should be. I'm leaning to an articulated pair of sternwheels inboard of the hulls. I dont think this has been done before, perhaps with good reason. If that works, I may experiment with cyclic pitch of the individual paddles on the wheels. Certainly that's been tried, but I don't see any available data on efficiency gains as a result. That may be a total waste of time. Immersion control of the wheels might be just as effective.

My objective on this forum is to pick the brains of fellows that know more about this than me and perhaps preclude some stupid mistakes. If there is a community here, I'm interested in that, too.

Ryland

www.tanstaafl.biz

 

I think you can do it too, across the bay from my work there's a stern wheel paddle boat that does harbour charters, seem pretty reliable propulsion but is fitted with a bow thruster to assist berthing. There is similar modular transportable pontoon vessels/work platforms available, I think some have been linked on the site before- maybe European or North American, some came as units including propulsion. Jeff.

 

Thanks. I have seen some pretty impressive efficiency numbers with a vessel in this configuration using slow speed diesel. I have never seen an external keel fitted to pontoons. I once kayaked in a vessel without a keel and it was aweful. Do you have any ideas there? It would be easy enough at this stage of construction to add them.

Ryland

 

Wow, that sure tops my idea....

A paddle wheel? Did I get that right...Why not use a conventional diesel, you can add the wheels for looks, as many of the commercial dinner boats do.

Why a 20' beam....won't most anything you haul be road worthy at 8' wide? Unless your Airstream has slide outs...

Will follow this one....all the best!

 

Rfleet,

There is a reason stern wheels went the way of the dodo. They are hugely inefficient until the wheels get enormous. In addition because of the huge mass, and size they take up valuable space that could be used for cargo, living, or just lounging on. Plus they do a terrible job in tight quarters since they can't be reversed quickly (momentum on all that mass). Today, even those boats that have wheels are after actually driven by props with the wheels just bolted on for cosmetic purposes.

They may look nice, but the low efficiency, and the poor responce to waves, and bad weather have doomed them. Particularly in small boats. Though if you just love the way they look, then have fun.

 

http://www.sydneyshowboats.com.au/gallery.html# here's some pics, maybe not so efficient but apparently reliable....

 

About as reliable as the diesel engines that power the wheels.

 

Or even more so... but one must drive the other.

 

Sternwheels are efficient and reliable, but very cumbersome. The larger the diameter, the better. They don't work well in swells and very large waves, usually not a problem in rivers and protected waterways. Alas and alack, they are susceptible to cannon fire.

I had thought of an articulated paddlewheel and had drawn some rough plans for a smaller boat, 8x32 plus the wheel, where the wheel was mounted on a captive ring and able to turn left and right about as much as an outboard motor. It would seem easiest to drive something like that with hydraulics. A solidly mounted divided wheel, where each halve can turn forward and reverse independently of the other offers better control also.

With a catamaran/pontoon hull I'm not sure of the length to beam ratio, in a solid hull, 3-4 to 1 is acceptable.

http://users.wirefire.com/gemort/contents.htm

 

The beamy'r the less wave interference drag and vertical up sidewalled inside hulls would have been better. Michlet can calculate that if you want
still not clear to me why, what and how you want to land this craft but what sounds better as a violin? thats rite, two violins or so the saying goes, how bout two paddle wheels, one in front as wel and beach as a flintstone mobil, just a late evening wild turkey thought. btw, peddlewheels are out but were not all that inefficient from what learned..

 

I think you should make the paddle wheels robust enough to do beach landings

Like this

from http://www.autocanoe.com/

 

Two violins!!? That struck a chord. I had a company that made the world's best cuckoo clocks, and we doubled the whistles and random cut them to make each clock have a unique voice.

Random harmonics are made of the stuff that humors humans.

Ryland