Why not use a design from 1916?

I've been looking at a design drawing of a displacement motorboat from 1916 (9,6 m x 1,70 m) by designer CG Pettersson he labelled "Fast Motorboat". see pictures, and my question to this forum is why this would not be a great hull in the future. I interpret the challenges going forward as inverted to the challenges in 1916, thereby possibly having the same answer. In 1916 boat designers had access to a lot of energy (gas) but not enough power (few and heavy engine alternatvices and a 14 hp Volvo Penta was a 180 kg).

If in the future we should not rely on fossil fuel, I guess going fast on water will require foiling, and going long distances will require lower speed. For short distances I guess anything would still work. But even lower speeds must be defined, I would argue 8 knots is a lot more than 5 knots so every knot in speed increase is relatively significant. Well, speed is of course subjective, the design from 1916 had a 15 hp engine and supposedly made 10 knots, thanks to a long and slender hull, and the designer labelled the boat a "fast motorboat", those were the times back then when 10 knots was considered fast.

I would love to go slower than planing speed, 8 knots, in silence, electric, and no need for a grease monkey on or after the journey (engine ownership). What do you think of the relevance of a design from 1916. I guess a big difference from contemporary designs in the same category is where the maximum depth is located, back then in the front approx 40% aft from the bow, and today the hulls are made very flat and more or less the most depth in the stern.

What do you think?

//Anders

 

Nigel Irens has designed powerboats which are high length to beam ratio, and low displacement to length ratio, and deep forward/shallow aft. They go faster than "hull speed" with relatively low power. He calls this design concept "LDL".
This link has a discussion of the concept: Hull Design for Propulsion in Small Craft - Clara Boat Company by Nigel Irens https://claraboat.co.uk/hull-design-for-propulsion-in-small-craft/
Other examples:
Wilhelmina: The Nigel Irens motor launch designed for sailors https://www.yachtingworld.com/boat-test/wilhelmina-nigel-irens-motor-launch-120503
Molly Ban - Nigel Irens Design https://nigelirens.com/boats/power-boats/molly-ban/

 

EcoSmart, an efficient motorboat https://www.boatdesign.net/threads/ecosmart-an-efficient-motorboat.66733/

 

Probably a decent way to look at going electric.

My only thought is on the electric motors, have watched more than a few alternative energy youtube boat channels. Electrics have a different set of operational parameters, but there is no escape from having to work on them just like a modern ice engine. It may be a different type of grease monkey but it's still gonna take maintenence.

 

Electricity has to be produced somehow. It then has to be stored in batteries that require mining and transporting (pollution), then manufacturing (more pollution), and finally creating very toxic chemicals which nobody is recycling due to cost. Regardless of power source, high speed is the least economic way, per distance, to travel.

 

Many thanks for the links. Very interesting and encouraging indeed. Inspriring reading and nice looking boats also.

 

Most of the 20th century was all about going faster, not efficiency; and definitely not environmental efficiency. Most small vessel "issues" could be solved by throwing HP at the problem. That mindset continues to linger today, one quarter the way through the 21st century. FWIW, mobile "electric", as it (i.e. batteries) is manufactured in the present, is horrible for the environment; much better to use an ICE...and will be for the next 30 to 40 years. At least Sweden is using ~30% Nuclear.

 

Thank you soo much for the enclosed file. I've actually seen the ecosmart, I saw it as a prototype at Lidingö boat show, very nice and inspiring. Your test enclosed was really really interesting to read, especially because the parameters you mentioned in the text are comparable, lengh widh, displ. and wetted area. That brings me to a follow up question. I can intuitively see that your design would be better in higher speeds and as an alround 0-15 knots or so, and actually it seems that your design is somewhat more efficient also in speeds below 8 or 10 knots. Personally I would like to stay away from the 10-16 knots range as I guess the energy consumption no matter design would be to great for considering longer distances on electricity. But do you find the difference in speed up to 8 knots being significant? and what will the difference be between your design and CGP in overall effectiveness and handling, for example motion, G-force and handling upwind against the waves, would your design for example be bumpier and slam more as to the flatter botom section in the middle or wich design would you choose if limiting yourself to the relative "cheap" speed up to maximum 10 knots for a 10 meter boat or so? Would your design have better handling in docks, keeping a steadier course or any other axpects of a boaters life you can think of // Anders

 

I believe you will be right in that assumption, and honestly, electricity and electronics usually are not a best friends of the humid and salty marine environment so I would be cautious in that aspect. On the other hand, windlasses are usually mounted in the worst possible place on sailboat bows and get lots of hugs and kisses from the oceant, and they are merely electric motors and still seems rather god at staying put, so it might not be so bad// Anders

 

I agree, and running a small diesel with HVO100 fuel would be rather clever both financially and environmentally going forward. And with that configuration there would be no environmental or financial reason to go electric really, except maybe the silince, space utilisation and easier fueling possibilities. One aspect Nigel Irens mentioned in the links included by DCockey is the cultural change and opening of new travelling possibilities for motorboats when speed reduces and hull efficiency develops and thus the cost for longer trips will be affordable and the journey will be smoother and less bumpy, more of the life of sailboats, and that would be nice I think. Reading about CGP going to the Baltics, To Netherlands, Rounding Scandinavia, to Denmark ant other longer trips mad me really inspired. I went through a lot of CGP drawings (maybe 100) briefly a while ago and it was so obvious when the engine manufacturere came up to speed offering better and lighter engines how even CGP drawings became wider and shorter obviously putting more horsepower in for more speed. People want speed.
//Anders

 

If you are satisfied with ten knots with a ten-meter boat, the transom depth should be slightly less draft.
JS

 

I would be fine with 8 knots actually. But what other difference between your design and a CGP with deeper forward section would you expect, pros and cons, are there any obvious benefits in either direction, I guess I am trying to figure out if, settling for 8 knots, is there any logic or pros in using an old drawing instead of inventing the wheel once again.

For example with your test where the two hulls were comparable in displ etc, if you would settle for 8-10 knots and there would be an effiancy favourability towards your design, would there be other pros for your design or any pros for CGP design?

For example, going against the wind, heavy seas, in ports etc.

ATB//Anders

 

You will probably need to add ballast to account for a much lighter moder engine.

 

Do you have any idea how much it would differ between a thin lightweight original wood hull and a modern sandwich composit hull, and do you think it would/could be a real problematic issue if using an old drawing but building with modern material? I guess that if going electric battteries could be a good ballast putting the weight low and maybe even increasing the stability.

 

100 years ago boats were built more heavily, with thick planks and hundreds of metal nails and washers binding planks to frames, and often many layers of varnish / paint. Modern light materials and construction methods would be beneficial to low power requirements, but without the heft of old materials, an old design made lightweight will probably have different sea keeping characteristics, and handle differently. Old designs do look more graceful though, generally. A decaying old boat disintegrates; a decaying new boat pollutes.