Long Skinny Vessel

[Reid]

Hey everyone,

I received this question regarding a Long Skinny Vessel design. He would like to hear your feedback/thoughts. Also looking for a reply from Jacques.

"From reading on line forums the topic of displacement boats comes up often and specifically to the idea of what I seen called a Long Skinny Vessel (LSV). Now I know you have the FL26 in your portfolio of designs but I see in comments online that the interest in that design is minimal because of limitation from what can be incorporated (or expected in this day) by the design and purpose of the design. The main draw back that I see written about a long skinny vessel is the cost of docking that negates the positive of fuel efficiency. In other words why limit yourself to a slow efficient boat with limits of space when for the same of overall cost you can have a fast planning boat with the same space and added niceties. So I was started thinking of how could you design a long skinny vessel for the efficient long slow cruise and still be able to dock it or even trailer it similar to a smaller power boat. In researching I see that there are plans and kits for small boats that are “nesting” or “take apart” where a bulkhead is built into the hull so that each part is floatable and when bolted together it becomes one larger hull. So I though why not do that with a Long Skinny hull and add a hing mechanism to spit the hull apart then swing it back closed for one large hull. Since this is a displacement vessel, to maximize the speed of the vessel I would make it as long as possible and still fit into a reasonable trailer sized boat or slip. For instances what I would like to see since I have a 20-22 ft craft no that is easily trailered is a vessel twice as long and half as beam so that when cut in half you can fit each 20’x4’ section side by side on a trailer or in a slip. Now I am not an architect so I don’t know if a vessel 40’ long and 4’ beam is possible or even safe or stable but maybe some sort of outrig or small ama could be designed to fold or swing out from the hull such as a trimaran even adding space by rolling out a trampoline as well. Now I am thinking this would be a great powerboat for those that want to explore coastal waterways at a slow pace and for an extended time. To power the vessel I think a small outboard would be the easiest and least expensive way of moving the vessel, so it would have to be designed where all the controls, helm etc. would be on the stern half the vessel."

[fallguy1000]

Meaning no disrespect, cutting a 22 foot boat in half is silly. Cutting a 40 footer sillier still.

A long skinny vessel has some inherent problems. A hull like my catamaran is simply not stable. In fact, the stability is negative which means a single hull 4' wide, 32' long will fall over. This is not to suggest all will, but the hull becomes more and more cylindrical as you lengthen and watch what a pencil does in water. It spins.

So, what about long canoes? It can be done.

But what you first need to do is develop the requirements. Why do you want a 40 foot long boat not wide enough to lay on sideways?

[VT_Jeff]

Maybe this will work for him.

https://www.youtube.com/watch?v=IfA7w4D_Olc

[Fuzz]

Displacement speed for boats is a product of waterline length. The longer it is the faster it will go at displacement speed. 1.34 times the square root of the waterline length. Long and skinny, within reason, will be faster. As for seaworthiness long and skinny makes some of the best boats ever built. You need look no further than the ultimate resource. Noah was told to build the ark 300 long, 50 wide and 40 tall. Only man has decided to built short fat boats because they fit into needs or wants that have nothing to do with being seaworthy.

[OneWayTraffic]

Displacement speed for boats is a product of waterline length. The longer it is the faster it will go at displacement speed. 1.34 times the square root of the waterline length. Long and skinny, within reason, will be faster. As for seaworthiness long and skinny makes some of the best boats ever built. You need look no further than the ultimate resource. Noah was told to build the ark 300 long, 50 wide and 40 tall. Only man has decided to built short fat boats because they fit into needs or wants that have nothing to do with being seaworthy.

I'm not a believer in the bible as a whole anymore (don't want to argue religion here) but that got my interest up. I put those dimensions into my Gerr scantling calculator for fun.

The planks would be 240mm(10") thick with frames 350mm (14") spaced 1.4m (5'). That's a stout boat. Would take a lot of time, wood and some help. I'll stick to plywood core glass epoxy with my boat thanks.

[fallguy1000]

Displacement speed for boats is a product of waterline length. The longer it is the faster it will go at displacement speed. 1.34 times the square root of the waterline length. Long and skinny, within reason, will be faster. As for seaworthiness long and skinny makes some of the best boats ever built. You need look no further than the ultimate resource. Noah was told to build the ark 300 long, 50 wide and 40 tall. Only man has decided to built short fat boats because they fit into needs or wants that have nothing to do with being seaworthy.

I'm not a believer in the bible as a whole anymore (don't want to argue religion here) but that got my interest up. I put those dimensions into my Gerr scantling calculator for fun.

The planks would be 240mm(10") thick with frames 350mm (14") spaced 1.4m (5'). That's a stout boat. Would take a lot of time, wood and some help. I'll stick to plywood core glass epoxy with my boat thanks.

Gerr tends to overbuild. I would say wood planks doubled from 2-4" thick to 4-8" would suit.

History of ships is really cool stuff. For example, the Chinese led; not stole and followed, for about 400 years in sailing.

[jonnymac]

Meaning no disrespect, cutting a 22 foot boat in half is silly. Cutting a 40 footer sillier still.

A long skinny vessel has some inherent problems. A hull like my catamaran is simply not stable. In fact, the stability is negative which means a single hull 4' wide, 32' long will fall over. This is not to suggest all will, but the hull becomes more and more cylindrical as you lengthen and watch what a pencil does in water. It spins.

So, what about long canoes? It can be done.

But what you first need to do is develop the requirements. Why do you want a 40 foot long boat not wide enough to lay on sideways?

I can speak to this having been on a submarine and in long period 6' swells we would roll like 5-10 degrees sometimes. At 600' below a category 4 hurricane we were rolling 15-20 degrees and almost everyone was sick. of course the boat was ballasted to stay upright

[Fuzz]

I am surprised to learn a sub gets tossed around that deep down. Learn something new every day

[fallguy1000]

He is a better man than me. They wanted me in that program in 1985, but I've got this thing for sunny days. And didn't like cigsmoke.

[jonnymac]

He is a better man than me. They wanted me in that program in 1985, but I've got this thing for sunny days. And didn't like cigsmoke.

fortunately smoking was banned like 10 years ago, I would have enjoyed more sunny days. I did get to enjoy swimming a few times in warm water where the water was so clear that I could see both ends of the boat underwater.