Technology to lead to lighter ships and boats

[JonathanCole]

http://83.219.63.174/Articles/290804/Ship-shape.htm

Light weight boats use less fuel. Only reduction of fuel use will allow boats to remain an economical proposition.

Aloha,

Jonathan

[Karsten]

To design an efficient structure of any kind you have to know the geometry, material properties and loads as accurately as possible. Those "strain gages" in the article will make it possible to measure loads under normal working conditions more accurately. To actually lead to lighter ships those loads have to be incorporated into the various classification rules most designers use to design their boats.

I think more weight can be saved by using higher quality materials and production methods. There are cases where a switch from polyester chopstran mat to carbon prepregs has been made. The result was half the weight with comparable total costs because of hughe material and labour savings. Also many boats haven't been designed by engineers. If a qualified engineer has a look at the drawings and crunches some numbers he/she can usually come up with a much lighter design.

There are numerous ways to save weight on a boat. A good start would be to invest some money into engineering and not just toss the materials that are lying in the corner of the workshop into moulds.

[JonathanCole]

It has always seemed interesting to me that the value of potential saved fuel costs does not drive engineering more than it seems to. I guess when fuel is cheaper than soft drinks, that fuel is seen as a throwaway commodity. Those days may be rapidly drawing to a close. How many people can afford their gas-guzzler boat if fuel prices double as has happened recently here in Hawaii.

Since it is technically possible to power a boat with solar energy in lightweight highly efficient vessels, it is interesting to imagine life on the water with minimal or no fuel costs. Some would say, get a sailboat, and I have spent lots of time sailing, but when the wind dies, you still need fuel and so you still need, lightweight super-efficient designs. So do we have any engineers out there interested in something beside speed and raw power? How about highly efficient, extremely comfortable and delightfully economical?

[rxcomposite]

True. A light boat will save on fuel but most common overlooked is the savings of materials in building the boat. Savings can be tremendous especially in production run.

If care and enough time is used in designing the scantlings, much can be saved by using just the right amount of materials. I use Lloyd's register program and i find it very useful because it allows me to analyse and or reduce scantlings where it is allowed. I usually run it four to five times to determine the best possible combination that will give me the lightest boat. Fiber placement (sequence of lamination) alone will sometimes reduce one or two layers.

Choice of manufacturing technology also helps a lot. Skilled labor contributes much to the success of the product. In contact molding, a skilled laminator can apply just enough resin consistent with the design to produce a perfect piece.

Consistent with the design means what the designer had in mind to produce the right combination of "strength" and stiffness with a given thickness. Many boat manufacturer have suffered returns due to cracks caused by overflexing of the laminate.

Stepping up a little, say VARTM, will produce a lighter, "stronger" laminate but at the risk of flexing (thinner laminates) so the designer has to check again the frame spacings. More frames, more labor, but still a lighter laminate.

Prepregs with the minimum amount of resin to hold the fiber together is the better solution, but being very thin, is used in conjunction with a core to get the right amount of stiffness instead of using too many frames.It is lighter than the VARTM type.

The ultimate solution is to use the exotic materials such as carbon and aramid which are mechanically superior to fiberglass. But then, cost becomes a factor in producing the lightest boat.

[water addict]

for commercial ships- making the structure super-light is irrelevant if your cargo and machinery weights amount to +80% of the total displacement.

[RANCHI OTTO]

Save weight is wonderful but when I design a military boat I have to satisfy all customer's requirements and at the same time reach the contractual speed. Often they require 50% more thickness in the bottom than the Classification Society.
0.5 knots less than the contractual speed means a penalty for the shipyard. Less than 2 knots, their refuse the boat.....
The contractual speed is my nightmare....!

RANCHI OTTO

[cyclops]

You need some of the armor used in British tanks. Ceramic. I presume mines are the concern? Same stuff used to protect tanks from a mine. True, water has a tamping or concentrating ability of any explosion.

[JonathanCole]

Is a light weight vessel necessarily less strong? Are there ways to make a hull more capable of coping with destructive forces without utilizing heavy metal? There must be ways to make a vessel rugged without using tons of steel or iron. I have heard that even thick aluminum can be breached with a sharp blow.

If a hull were a bundle of hollow pipes, could the outer pipes be sacrificial and replaceable? The doubled hull concept (as in oil tankers) leads one to triple hulls, quadruple hulls - multi hulls-within-hulls with flotation as intermediary. If the material costs of these hulls is not too great then maybe the individual hulls don't have to be too strong due to the redundancy.

How about a SWATH hull in this type of configuration? Multiple tubes, some for boyancy, some for ballast, some for fuel storage, some for water. If you could bring an otherwise submerged hull to the surface by blowing water out of a ballast tank, you could put maintenance items like batteries in an otherwise completely submerged hull.

How about a bundle of tubes wrapped with carbon fiber and kevlar and with molded/cast bow and stern attachments? Anyone ever try capping the ends of an ABS pipe and throwing it in the water? My guess is that it would be able to circumnavigate the globe many times. Actually they now make foam core ABS pipe so it probably floats without capping the ends.

Anyway, just blowing the cobwebs out of my imagination.....

[cyclops]

It still amazes me that NO cargo freighter is a sub. Huge displacement, no real storm stresses, use of ocean currents for fuel each way. What does it take for change or improvement? Some one to build it and show the Majors this change does work? Why are they even called a Major if they can not improve in different ways? A builder is not the same as a original designer.

[JonathanCole]

Interesting point about submarine freighters. I have thought about submarines that are not deep diving vessels but only need to dive 50-100 feet or so to get out of the turbulence of the wave action. Such a ship would be much cheaper to build than a deep water submarine and would get all the advantages of efficiency. A shallow diver would make a lot of sense for a cargo sub. The sine-wave propulsion Manta submersible attached here is meant to dive less than 50 feet.

So many cool ways to use the water, so little time!

[RANCHI OTTO]

Dear cyclops,

I use ceramic all around the fore cockpit where is located the 20 mm gun machine.
The MANTA ASD (see pic's) has the following data:

Material > aluminum
Lhull > 14.6 m
Displ. F.L. > 20 t
Range > 550 n.m. at 45 knots
Vk > 50 knots in trop. cond.
weapon > 1 x 20 mm + 2 x 12.7 mm or 2 x rockets launcher

How to save weight ?

1 cabin with 4 berths
1 sanitary fully equipped
air cond.
1 galley
300 kg ammunitions
etc.

Even with floating structure system for the hull I can not save a lot....

Only positive thing is the hull shape that permits me to have reduced draft and to bear 3.5 t fuel oil and to reach at full load condition the contractual 50 knots speed (52 knots in Kuwait) with Arneson and Rolla piercing propellers.
The craft gets in planing condition in few time and it is possible to shoot against target at 50 knots by turning because the reduced heeling angle.

RANCHI OTTO

[rxcomposite]

The sub has long been evaluated for commercial purposes There are many pros and cons.

Sub does not suffer from wave making resistance. it has more surface area thus it is more efficient at high foude number. That means the cargo it must ferry must be economical it it is delivered fastest. Ore or liquid bulk cargo do not belong to this category.

To get an efficient cargo carrying capacity, designers would be looking at high Cb's. This means an over square egg or almost rectangular sections. This will penalize speed which the sub has gained advantage.

At any rate, the sub would require a large amount of draft to be cost effective.

Powerplant would be limited to either fuel cells or nuclear reactors. It is expensive and requires special manning.

Above restraints prevents the Majors from undertaking developments. The return of investment from commercial operation is not promising.

[FAST FRED]

Simplest I have seen was a simple bladder tank , towed buy a tug.
The tank is submerged , so only (HUGE) skin friction drag needs to be provided by the tug.

Advantage , the tug has tiny manning requirements , and simply leaves the tank , to be unloaded at leasure.

FAST FRED