Pop 25

I am afraid "Bernard the sailor" you are hopless.

 

Budget, as in US$, or energy budget, as in required kW to consume, produce and store ?

regards,
Bernard

 

Thank you!

Bernard

 

24hr run...autopilot, instrumentation, refrigeration, lighting

 

OK, that's what I thought. Give me some time.

 

I like this design.

It looks like a good coastal cruiser with lots of sapace inside for a boat of its size.

The double bulb keels is a very interesting concept, and I can see their cruising advantages. The bulb effectively lengthens to bottom of the keels, so the boat can stand up on them, at least on sandy bottoms. They also concentrate the weight low.

Clearly the near arrow point hull is intended to get as much live aboard space as possible, without resorting to either a very blunt or even pram bow. Living space is far more a function of Beam than Length, Hence the wide Beam and Arrow point shape.

The twin rudders are to make the arrow point shape work by making sure there will always be enough rudder area in the water to steer the boat. With a single, center line rudder, much of the blade area would be out of the water if hull was heeled over.

I do not believe this boat is expected to be sailed heeled over sharply.
I expect it to be sailed nearly level with maybe 10 to 15 deg. of heel.

In this condition, both rudders and both keels will clearly be fully immersed, or nearly so.

Sailed at a greater angle of heel, I would expect this type of hull to want to round up into the wind. Such a tendency may be so powerful, the rudders may not be able to over come it. I suppose it can be countered that the twin keels will somewhat lessen that tendency, as the leeward one will likely produce more lift and drag than the windward one, causing a turning tendency in the opposite direction. Even so, on a hull like this, the mantra should be reef early and often. It will almost certainly need a strong auto pilot or wind vane for any distance cruising.

My main concern is the masthead rig with no back stay. I find that very worrisome, as I suspect the large jib will not set well, even when mostly rolled up. Perhaps it's the designer's intent to simply use the windage of the shortened jib to hold the bow off the wind, as the main does all the driving work. Then it would hardly matter if the jib held its shape. To make the jib more effective, (only one would be used at a time, except when sailing downwind) running back stays could always be added. I would like the design better, if it went with a bigger main and a smaller jib. This could be done by moving the mast forward a bit and maybe resorting to a gaff main or a fuller roached one.

I suppose a major design goal was reduced slip rental. Slip rental is almost always based on boat length. This is because it is far easier to pack a lot of short wide boats into a given space than it is to pack in a lot of long narrow ones.

Whether or not to build this boat is a function of how well you really like it, your skills, access to building space, and, above all perseverance. Like others have said, it is not an economy move. If you decide to build it, look forward to spending at least a working year (2,000 man hours) of your life and more money than you expect.

But after you are done, assuming you finish (maybe five years down the road), you will have a unique boat and probably owe little or no money on it.

 

Here is what I have so far:

Engine: 1/2 power = 1800W on 24 Volts for 1/4 hour = 30A
Fridge: Needs 5 Amps running 50% of the time = 60A
VHF stand by .6 Amps for 24 hours = 14.4A
talking for 1 h = 2 A
Autopilot totally depending on conditions, but average 1.5 A = 36A
Instruments .6 Amps for 24 hours = 14.4 A
10 cabins lights for 4 hours Led = 16A
GPS .6 A on 24 hours = 14.4A
Total energy consumed in 24 hours -> 187 Amps, add 20% for some margin = 223 Amps

Energy produced:
Engine 40 Watts at 5 K for 23 hours = 920 W
Solar panels 2 * 40 W = 80W remove 25% = 60 W for 8 hours => 480W
Windmill 40 Watts for 24 hours = 960W

Total energy produced = 2360 W / 12 volts = 196 Amps. A bit more than energy consumed, but without margin.

Now, there are ways to optimize this. For example, an icemaker would take 2.4 A for 6 hours to make enough ice for 24 hours in an icebox, would be better than a fridge taking 5 Amps for 12 hours. There are solar panels producing about twice as much energy for the same size. Could have a second water generator, etc, etc...

If you look at the Pop 25, there is room enough for 3 75 W solar panels. Even at 50%, that makes for 900 W instead of the 480 I used in my calculation.

As I already said, the batteries to store that energy are already taken into account as ballast, and they store 600A. Even with the calculated margin, they would not be discharged to 50%.

Maybe the safety margin should be better, but I don't see any important item that I would have forgotten here. I still don't see where the impossibility would be, and I still don't see why a 25 feet sailboat would not be able to consume and produce energy as indicated.

BTW, if it's more than 24 hours cruise, motoring only to get out of the marina, it makes it better. I don't take into account motoring to get back in, as you can top the batteries on AC/DC once docked.

 

The engine you propose will be a 1.8Kw at half power working for 15 minutes?
I don't understand you first paragraph.
I understand the other, but not the first one.

 

Where did the windmill, motor and solar power come from ? - you were talking Hydrogenerator. I dont even see that in the equation !

You are changing the argument.

 

The engine is given for 3.6 kW at full power. I believe that, beside short bursts, to get out of a marina you are not even using 1/2 power, and that, as an average, 15 minutes motoring should be enough. It's obviously arbitrary, as there are so many conditions influencing this. So, as I say, you would consume about 30A (it's on 24 volts) to run the engine for this lapse of time and at that power.

 

No. You are making one that does not exists. Go back to my first message in this discussion.

 

Sharpii2 you are dead on with the number of hours. I had exactly had this number in my mind. It means yes five good years and let say $35,000 to $45,000.
Inflation is terrible, everything for boat construction and fitting exploded what ever the material the boat will be built of. When launched the price of everything will be 30% more.
So hurry up abh

 

I am afraid is far too small. This boat of 2.8 metric tons need at least 8 to 12 hp to go against any tidal current or to get out of trouble.
To cruise without wind but with residual waves 5hp will be necessary.
At 3.6 Kw the boat will not move. 15 minutes range don't get you out of a river, or an narrow estuary.
But on a 10 hp and 20 liters fuel tank will keep you going at let say 5knots for 12 hours. The weight of the fuel will be 16kg, and the aluminum tank and addition of 5 kilogs.
That against 150 kilogs of batteries.
Plus electric motor are heavy and often need to be water cooled.
Nope BernardG as nice as it sound, it is not an option.
The boat is too small. At let say at 12 metric tons, it will start making more sense.

 

Thanks for this contribution. I am not sure I will build THIS boat, but I look closely at the possibility. I know it's not an economy move, if you compare to used boats, but it is one if you compare to new production boat.

I am sure it will be (with this one or another) more money than I would expect, but that is also very much the case with used boats, with the difference, I believe, that with a one you build it's easier to plan and foresee expenses.

best regards,
Bernard

 

Well, I took as scenario getting out of a marina. This calculator http://www.psychosnail.com/boatspeedcalculator.aspx
tells me that I would need 1.3 kW to move the boat at 3K, which is well below my estimation, and I don't see why I would want to motor faster.

Now, I agree that to go against tidal current I would need more, but maybe I can also wait till the tide helps me rather than the contrary? BTW, as I intend to mostly sail in the mediterranean sea, I don't think I will have to fight tide much