Did a dream got shattered?

Actually, 100 years or so ago there were also hundreds of electric riverboats, at least there were here in the UK. They were pretty much killed off by the introduction of boats powered by internal combustion engines.

One consequence of this shift was a trend to move away from efficient, easily driven, hull designs to boat shapes that were either more practical or easier to build. The hull shortcomings could be addressed by just fitting a bigger engine...........

If designing a boat for limited power (which is essentially what you're doing when opting for electric, rather than hybrid, propulsion then you really need to fundamentally address the hull design before anything else.

It's easy to fall into the trap of thinking that an off-the-shelf design can be converted, without looking at the design requirements that led to that off-the-shelf hull being the shape it is. It's unlikely that the original hull designer was thinking of limited power, the distributed mass of batteries or some of the other specific requirements that you might have.

In the limited time that I've been switching myself from aircraft design to boat design I've come to realise that drag reduction (essential for keeping the propulsion power requirement down) is often pretty low on the list of "important factors" that boat designers seem to work to. Anything you can do to reduce wetted area and increase waterline length, without incurring unacceptable penalties in terms of reduced stability or seaworthiness, will be worthwhile in reducing the power requirement.

BTW, that propcalc programme seems pretty worthless at low powers. I found that it gave big errors when you get down to the 1kW or so region. I'm near certain that most of the best experts on low power, high efficiency, prop design are right here on this forum; people like Rick Willoughby, for example.

There's been lots of grand talk about new technologies, but to be honest, nothing has yet made a massive change in the effectiveness of electric propulsion. Motors today are only slightly better than those in Victorian times; batteries are a bit improved, but not enough to make electric propulsion in any way comparable with internal combustion engines. Even the most unlikely sounding technologies won't make a massive difference and most of them are so far away from a marketable product as to not be worth waiting for.

Jeremy

 

Thank you so much Jeremy, even that it was an icy cold awakening. I expected that this calculation program was accurate. That put a total different angle to the whole concept. In that case, there is no other option for me then to go for the Fisherman 18 . The problem is, I have back problems and the reduced Hartley 28 was more suitable all around. I found it already strange that if I increased the weight, but stuck to the power required, the speed was reduced pleasantly very little in that program.

Jeremy, I really was relying on your country men. What a pity.
What now. The Fisherman 18 has no keels, which would have been used by me for propulsion, steering and battery storage. I don't have the practical knowledge to start re-designing or designing a boat, like somebody said with the distribution of weight of the batteries etc. The reduced Hartley 28 was more suitable then the Fisherman 18. There is more information on the plans.

Is there anybody who could accurately tell me what the power is required for 1600Kg displacement with a 5,5 meter displacement boat. And at a low speed (at 1 Kw, what speed would such a boat go.)

With re-calculating a reduced by 8 – 13% Hartley 28 and redistributing of the weight and compensating the imbalance I introduced with the reduction. I honestly thought, with some help I could pull it off. However if the power required is so way out, then the risk is too great that it changes the total picture.

Still for my own education, I will finish the calculations started. Nothing wrong with learning.
Bert

 

Hi Pierre, I think you misjudge me. Yes, to a certain extend making something what I like and what works (for me) is more important then the money side. Although I don't have too much of that. I have planned to build this boat over a period of 3 years. Starting in a few months time and the past 6 months having experimented with various idea's. Electro motors running in transformer oil for cooling, pipe system for batteries. etc. etc. Now with the main picture of not been able to trust that program it is a real problem for me. Who do I trust now?
My original plan was to make the Hartley28 by a very small reduced margin and if I am too old to use the boat, to sell the boat and that person could either put a taller mast onto the boat with extra lead and go again sailing or use it further with electrics.

I still haven't grasped why a reduced very good displacement boatplan differs so widely from a same size from scratch made displacement boat. I have to figure that out for myself, why this is the case. Nobody can help me there. It is the same as that youngster from Italy who like to cross the Atlantic with a 480 HP electric driven motorboat with only on batteries. He has to graps and figure it out for himself and I hope that we wil help him.

Bert

 

Why cant you use the design of a 25 foot trailer sailer?

 

Possible Yes, absolute no problem. Dennis, you must see the history of the saga.

1) Always rented the boats on which I was sailing and motorboating
2) Buy a plan to build a Hartley 28 feeter on recommendation of an excellent boatbuilder here in Town. (did his practical under van der Stadt, the old one)
3) During sailing overseas, I realise, we are getting too old for not having enough hands. Plan changes to electrics.
4) Boatbuilderbuilder dies while having hartoperation in November 2009
5) Buy new plans for planing hull boat after recommendations. Stick to the same supplier, as this boatbuilder told me how good those plans were.
6) Boat.net up in arms not the right hull for electrics
7) I suggested to reduce in that case the displacement hull by 13 or 8%
8) boat.net nearly murders me
9) buy on recommendations the fisherman hull.
10) boat.net says twin propellor more efficient, books says 3 blade more efficient.
11) feed information into a program called PROP-CALC, boat.net informs me too inaccurate at low power calculations.

Dennis, I am going to have a nice glass of wine. (rose) Sit back, discuss it with my wife and clear my mind in what I am going to make. I hope that you forgive me that I am not going to jump into buying something else before I have a good overview of all my options. I still have a few months before I really start. (I have my reasons) and maybe by that time some people have stopped with insulting other people directly or indirectly.

Bert

 

BerKu, you have made me laugh with this short review of your boating saga (apart the death of your boatbuilder, of course).

I realize that this is a rather important thing for you and also that you appear to be very determined about giving it a try anyways.
The problem, as I see it, is that you are making your moves without having clearly defined your objectives, apart that you would like to go electric.
It's somewhat like you've bought blueprints for a generic mountain house form a renowned architect, because you always wanted to build a house near the sea... But then you discover that seaside parcels are too small, so you have to shrink the house.

Instead, you need to start from the requirements. A glass of rose wine is a good idea - though a red would be better, imho . It will make you relax to the right point when you will take a pen and a paper and write down all the things you want from this boat. It means (at least) cruise speed, range, operating area (blue water, sheltered areas, lakes, rivers etc.), types of propulsion systems desired (possibly not all-electric, if you need a practical boat) and undesired, fuel/energy autonomy, food/water autonomy, time at anchor vs. time in navigation, preferred material and construction method, number of passengers, equipment and commodities on board, deck equipment, etc. etc. etc.

When that part is over, get back here and show us the list of requirements. You will then see that the advices will start to arrive in a much more organized and constructive way.

 

What about a folding tri? It wont be self righting but it would be unlikely to tip in the first place and can be made unsinkable easily. I think the light weight would led itself to low power propulsion better than beamy keeled yacht. Also it would have lots of room outside.

You can always sell your Hartley plans.

 

From Hartley I love this one.
Daniel

 

Bertku

This what I said in my post #31

Nobody did:

Quite the contrary as you can read all the posts trying to help you from the members.

Good luck
Daniel

 

Hi Bonasera,

I am pleased that some of us keeps the sense of humor and I enjoyed your help. Yes, that is what we have done, with the inputs of my wife last night. I am going to chew it over during this week. I will be spending 50.000 per year over the next 3 years. Unfortunately it is in Rands and not Euro's. Inputs from you, Jeremy, Rick, Cor, that Canadian lady designer, Tugboat, Tom and those who have positive reacted, have been absolute helpfull to me

Will you do me a favor and ask your countryman how much money he is willing to invest in his project. I am under the impression that you have a customer for 200.000 Euro, but need some help to clear his mind. Also to keep him away and out of the shipping lanes by Hamburg.
Bert

 

Hi Daniel, I think you were quite positive, except maybe the statement "You don't belong to this forum" or something like it and I even agree with you there. Thus I am taken a break.
However that said, this forum needs to control the shipping lanes by Hamburg. I don't think it is good for the image of this website which has the prime task in obtaining orders for you, designers, boatbuilders etc.

The forum is just there, to see whether there is not an idea coming out of it which could be used by those who are paying for this website. Regardless whether it is an order or trend or direction.
Bert

 

Bert,

I can appreciate the dilemma you find yourself in. Years ago I had a dream of sailing long distances in my own boat, rather than someone else's (either borrowed or chartered). I'd read the "Shrimpy" books by Shane Acton and convinced myself that, on my then very limited means, I could buy a very cheap small yacht, do it up and turn it into what I wanted.

After a couple of years hard work, converting a wreck of an old small boat into what I thought I wanted, I realised that it didn't sail well, wouldn't be practical for extended voyages and had just far too many compromises from me trying to squeeze too much into the size of boat. What was worse, when I added up the cost over the years spent re-building it, I realised that it wasn't the cheap boat I thought it was, either!

The next boat was different, as I accepted her for what she was, learned to live with her little foibles and didn't try to make her do anything she wasn't designed for. I had far more fun with her as a consequence.

Currently I'm working on a far more modest boat, but am having to make some of the same design decisions as yourself. I'm using electric propulsion and solar charging, so only have very little power available. This has influenced the hull design, as to get the performance I want the displacement and wetted area have to be low and the waterline length has to be as long as I can get without compromising stability from an overly narrow beam. Appendage drag has been minimised by removal of anything unnecessary from below the water line, so no keels or skegs, just a very slim, streamlined shaft leg, with a large diameter, slow revving, thin two blade folding propeller (it only folds to shed weed and reduce draft when beaching).

Some of these design compromises, like the low weight, are helpful in other ways, like making transport out of the water easier. Others are less easy to live with, like the relatively large draft caused by needing a big propeller (for efficiency). All told, just like every boat, it will meet one specific set of requirements, matched to my needs. It may well not meet the needs of anyone else though, which is the inherent problem that all "specialist" boat designs face.

Someone above suggested starting with a clear set of requirements, before even thinking about details like hull shape, design, power systems etc. This is excellent advice. In my case I sat down and ordered my thoughts into a list of things I wanted, and things I didn't want. I then put this into two lists, in priority order, one of things I wanted, with the most important at the top, and one of things I didn't want.

I worked through these lists several times, to make sure I was completely happy. My list of "must haves" started like this:

An open boat for use on sheltered inland waters
Seating for two, in comfort
4 mph cruise speed
Fairly traditional looks
Electric propulsion
Near silent at cruise speed
Endurance of at least 8 hours cruising without charging
Can be launched and recovered single handedly
Easily trailer-able on UK and European roads
Freedom from external power requirements for charging
etc
etc

The list of things I didn't want was just as important, especially as one or two of them ended up being traded off to allow things that I did want to be included.

I've found that this process of ordering my requirements has helped to maintain focus. There have been times when I've been tempted by suggestions from others, like the time that Rick W suggested his faux tri design. I managed to get back to my list and realise that I'd be giving up something high up, the "fairly traditional look", something I knew I'd regret later if I switched to his design.

Boats are always a compromise, the secret is in finding exactly the right compromise for your needs. The happiest sailors I've met have been those who, either by luck or planning, have ended up with a boat that fits their needs very well.

Finally, it's worth remembering that sails don't generate very much power. A 10m² sail running before the wind, with a boat speed of 5kts and a wind speed of 15kts is only delivering around 416 watts. An electric propulsion system, fitted to a boat that is optimised for it, can now have a performance that is close to that of a sailing boat, provided you are prepared to accept the compromises that come with that choice.

Jeremy

 

Thank you Jeremy,
Well said.
Bert

 

Are you going to show us your list now?

 

It's a forum, things come and go, feeling fly high and low. Nothing serious.
That said, I apologize for the

No need for that, I agree.
Good luck.
Daniel