Barge to carry a single pick-up truck

@bajansailor tells me welded steel would be a good choice. Truck driven in when empty, moving its CoG as far aft as possible. Backed on when fully loaded, same reason. Deck sides, and push frame omitted for clarity.

 

If you want to build it yourself, I am thinking that steel could be a reasonable option, as it would be much easier to become fairly proficient at welding steel, compared to welding aluminium (?) - and much quicker than strip plank timber construction like Serenity
And steel construction (similarly aluminium) can go together very quickly indeed, especially so if you can get all the hull and deck plates and frames nested (for minimal wastage) on the computer which then sends instructions to the cutting machine - then it is just a case of assembling the kit and tacking everything together followed by final welding.
And if you use plate that is already blasted and primed then you would just have to repaint the welds, followed by the top coats of paint.

Is the broken (dotted) line in the side profile sketch the outline of the bulwark around the deck?
I presume that there will be a gate on the bow - and what about a ramp for loading / discharging cargo?

Re how the push frame is omitted for clarity, this little 25' pusher tug has a couple of impressive pushers on her bow - would yours on Serenity extend down below the 'ram' as well for maximum pushing contact area?
2010 25' Truckable Steel Push Tug /To Be Ordered From Builder for sale. View price, photos and Buy 2010 25' Truckable Steel Push Tug /To Be Ordered From Builder #50319 https://dailyboats.com/boat/50319-buy-25-truckable-steel-push-tug-to-be-ordered-from-builder-for-sale



A steel barge carrying a 6 tonne load (re the truck) is probably going to be up around 9 or 10 tonnes total displacement - will the sea sled hull form still be effective (re the tunnel) at relatively slow speeds (4 or 5 knots?) when being pushed, or might a more 'conventional' hull form be better (or perhaps even a simple catamaran hull form, with well raked bows?) ?

And finally (for now), a rather left field thought - if you were towing instead of pushing, could you maybe have a pair of towing eyes on the bow of the barge, fairly low down (maybe just above the waterline, like on a dinghy being towed)? This might then help to 'lift' the bow a bit while under way?

 

Mostly lurking, but isn't the big issue in a ply/wood boat to resolve just the deck?

The barge front hits the beach, so needs abrasion, but the scantlings can be figured out using Gerr's method for a barge...

I don't think it is that hard. The hard part, afaic, is getting the Vg right. If you don't make the barge wide enough; the risk is the weight of the cargo becomes more than the hull, etc.

all beyond my ability to pen, but based on my Pikangikum story; a small sized vessel has lotsa risk..

 

But your expectation is 98% pushing because of what you read so far, it's more efficient, no?

I just don't see the advantage of a Sea Sled hulled barge over a conventionally hulled barge.
In fact all I see are disadvantages, but what do I know.
And, you have Sea Sled goggles on.
Are you sure you're not related to Hickman?

 

I absolutely have Sea Sled goggles in. But it moves easier through the water than the classic barge shape, has beam stability better than even a cat, and can move quickly when light. More difficult to build than a barge box, that's certainly true. If there's another disadvantage, no one has articulated it yet. Not saying there isn't one, just waiting to hear it.

 

@fallguy , I cheated for roll stability. I just found other landing craft that successfully do what I want, and copied that beam. And the SS shape has far better roll stability than a shallow V. More seaworthy too.

 

@bajansailor , your observation is correct: that is a tentative bulwark. The oblique line at the far left edge of the image is a tentative gate. Ramps might be separate, hand placed affairs.

The push knees are to be part of the barge, rather than Serenity, since the latter would frequently operate alone, but the barge never would. I like the idea of the towing eyes as you suggest.

I don't know how much more efficient the SS form might be at low speed. It would take some towing tank tests to prove that it was less efficient than the classic 'brick with the ends beveled' shape. And a life threatening dose of LSD to convince anyone that said shape would be better driving into wind driven waves. I've tested that one myself at 4-5 knots, a couple hundred hours so far.

It is likely to not be worth the extra effort to build. However, it may allow a working speed of 7 knots vs 4 knots. Or 5 knots into headwinds and wind driven waves. And that might be worth something.

 

@BlueBell , you are correct: pushing has been proved to be significantly more fuel efficient than any other mode, with enormously better control than towing: comparable to side towing. It is not suitable under bad conditions though. Or so the research papers and descriptions from towboat operators would have me believe. I have a total of about ten hours towing time, so my own experience means nothing. Setting up for pushing seems reasonable, considering I designed Serenity for that, and carry a weight penalty in the form of the ram. Being able to push doesn't mean towing is precluded. All ten hours were towing another boat on a hawser.

 

Why not use the truck to provide the propulsion.

Park the drive wheels on rollers connected to a propeller.

Alternatively connect the rollers to a generator to power an electric drive.

 

You look at what others have done before you. Best known example: https://upload.wikimedia.org/wikipe...e_and_Construction_Plan_-_NARA_-_78116787.jpg

 

@latestarter , the mechanical efficiency would be very low, and steering very difficult to arrange.

Fantastic paper on optimal barge forms. The Reynolds numbers for these are rather different from mine. Are these directly applicable? I refer to the first lae of design: "That depends"

https://www.google.com/url?sa=t&sou...AQFnoECDMQAQ&usg=AOvVaw1ojhvTxw_s5A-A-zvPW7KO

 

The flat-bottomed box will always have the least draft for a given load, which will be a huge deal if you're working on/off an unimproved beach. It's also far simpler to build, totally eliminating the centreline structure. Sectional shape, say inverted vee vs flat-bottomed, will make little or no difference in stability or resistance at 5.5 knots. The big factors are length, beam, weight/VCG, and how the rake on the ends is done.

 

A couple of elongated hypalon envelopes and some strong web netting will get it done, and then pack into the bed of the truck.

 

I'd have to watch someone take their new truck off a rocky beach, cross open waters, and land their new truck on a different beach before I'd be confident.

 

I can’t quite see your desired launch/land beach from here, but surely you have tides that could be useful?