Advice on Raft/barge/ferry from lumberyard material for occasional 6 mile trip

I'm looking for a very simple design and advice. I live on the Yukon River in Alaska and the residents of my village often need to move large heavy objects 6 miles up the Yukon to the road and back again. A $100k landing craft would be great but overkill for the few times it would be used each year. The river is only navigable 5 months of the year, frozen otherwise. Natives have been lashing a dozen 30-40ft logs together for years but Im looking for something more durable. Whatever the design it must be recovered in September and launched in May. Anything left in the water or on the bank over the winter will be destroyed by ice breakup in the Spring. Log rafts are too flimsy for launch and recovery.

Im limited to lumberyard material than can be bolted together and have enough strength and stability to transport a 5000 lb vehicle or similar load in the occasional 2-3 ft waves. Hydrodynamics are unimportant, just stability. Propulsion would be large outboard or pushed by a Jon boat. My thought was log raft-like dimensions (~20'x40') made from whatever Lowes sells. I just have no idea what actual size is required or whether 2x12 lumber, 4x6 timbers or plywood would handle the stresses and buoyancy requirements. We have a bulldozer for launch and recovery.

 

Firstly, you won't find anything at the lumberyard that will be tougher and more durable than a log raft. Secondly, what kind of service will it see? I assume it will be grounded hard and possible hit a lot of ice.

 

Could something like this work, or would it be too expensive relatively?
https://rollingbarge.com/floating-dock-kits/

 

Freight is the problem. It's ridiculously expensive to ship anything to AK. Cheaper to buy what's already being shipped here in bulk. It's been a while since I priced out the dock kits. Gonzo - the problem with log rafts is the lashing together part. I'm sure they can be stiffened for lateral strength but they say the logs get waterlogged so they use them for the summer then cut them up for firewood. If I could make a log raft strong enough that would work but now you are talking about paying men for several days to go harvest enough timbers. Yes, it will be grounded against gravel shore with the waves continually rocking it. Of course we could use a tire as a buffer but the water level is constantly changing, sometimes 2-3 feet per day. It will not be in the water the same time as ice. I love the idea of floating dock kits and the use of poly 55gallon drums. Of course I can build the framework to hold the poly drums and Ive seen a lot of homebuilt frameworks for docks and pontoon boats but I'm not positive how to build it strong enough to carry a Chevy Suburban in 2ft waves.

 

I would think they cut them for firewood because it is easier than going to the woods and cutting new trees, then waiting for them to dry. Waterlogged timber does not make good firewood, so there is something odd about the story. If you can keep locals from taking apart a barge built out of lumber and plywood, you should be able to keep them off the logs. Otherwise, you will be building a new barge every Spring.

 

Ah, so a waterlogged barge starts to loose it's buoyancy? And I suppose it won't dry out over the winter either but go even more kaputt once the water inside freezes.

If you do have access to plastic drums that sounds like the ideal way. You can find many examples for this. But you're also going to need a lot of wood. Does it really have to be 40' x 20'? That sounds like it might complicate things compared to say 25' x 10'.

You need 11 drums for 5000 lb buoyancy (450 pounds per barrel). I read you should triple that for safety and need to include the weight of the barge in your payload. So you're probably going to need 40 barrels or more.

"The outside dimensions of a 200-litre drum are typically 584 millimetres (23 in) diameter at the top or bottom rim, 597 millimetres (23.5 in) diameter at the chines (ridges around drum), and 876 millimetres (34.5 in) height."

Not sure how they'd do being dragged over gravel though. Maybe you need to have a double keel of some sorts to protect them.

Also how are the barrels secured in those rolling barges to "not fall out"? They don't seem to show that anywhere.

 

Thank you bajansailor. I found a company in Anchorage with these kits. I was shocked at how cheap they are in comparison to other options. $3500 plus the cost of the wo0den deck gets me a 10x20 with 9200 payload. Ive got to drive 12 hours one way to pick them up but I think thats the right solution. I thought it would be much more expensive than that.

 

Nice. Let us know how it works out!

 

The natives are extremely knowledgeable about what trees make good firewood and how long they need to dry before burning. When building a raft they look for wood that will make good firewood at the end of the season. Its not feasible to pull them out in the winter and put them back in the summer. It's less work to just find more logs next year. Yukon Men was filmed here and one episode shows that right after breakup the Yukon is a loggers paradise because its littered with massive logs floating down stream and all they do is lasso them and lash them together and pull to the shore. And there's your years supply of firewood.

 

Interesting. But how do those massive logs end up in the water?

 

Excellent!
Although I would be a tad worried about transporting a 5,000 lb vehicle on a 20' x 10' barge, never mind that the payload is 9,200 lbs.
One reason being that the centre of gravity of your vehicle is probably going to be at least 3' (or more) above deck level.
And you mention possible 2' - 3' waves - this is pretty rough really!
I think I would be inclined to make the barge a bit wider.
You could even leave out the barrels in way of the centreline (to create a catamaran of sorts), as they only contribute to buoyancy (which you will have enough of) and nothing to stability.

 

Thank you for validating my concerns. That's exactly why I came to this sight. Just because the salesman says it will hold the weight Im pretty sure he does'nt understand stability requirements. Lets say a Chevy Suburban is 8 x 18. How much wider/longer does it need to be for stability?

 

I'm still not positive about that but I'm sure erosion is partly to blame as well as the massive blocks of ice that are coming downriver. The Yukon has 4-5 feet thick chunks of ice at breakup. When the water level rises it breaks up the ice into chunks the size of buses and 1/2 tennis courts. These get pushed up on shore and knock down trees. It's amazing to behold. Attached is just the first pic I could find. They are often much bigger than that.

Notice the human in the middle of that picture for scale.

 

Did you buy a rolling barge.com kit from them, or similar? Do you have a link? I’m also looking to build a barge/raft for our remote cabin

 

L brackets are screwed into the barrel, and then the l bracket is screwed into the decking.