Cheap to run, cheap to build electro plywood cruiser ?

[Guest625101138]

Here is the ASM10 with canopy, prop, rudder and pilot.

Would be worthwhile building a model of this. I can run performance data on the model.

If you select a motor that has efficiency data it would be reasonably accurate to do performance checks with low cost multimeter. I suggest you go to a model of robust size. You want a displacement around 5kg to give you something to work with that is robust. So suggest about 1/8th scale. This will make the model around 1.2m long.


Rick W.

[rwatson]

Check out the 'Electic Mundoo' - an already designed, proven production design, with battery skeg and all the internal specifications complete at

http://www.duckflatwoodenboats.com/mainpages/mundoo.php

in plywood, trailerable, liveaboard size. Seems to have most of what you need there.

[kengrome]

messabout, I think Rick based his design on the Atkin tunnel-stern Seabright skiffs. These were very economical hulls at low end planing speeds, but this boat will never plane even at low speeds. Therefore I think the original Seabright skiffs might be a better starting point since they were designed for slower displacements speeds, and in fact evolved more directly from sailing boats. I might suggest Spermaceti:



... or perhaps Sergeant Faunce:



... but built using lighter construction materials and techniques than Atkin specifies of course.

I think Knut's suggestion of "Mundoo II - Electric" from Duck Flats would be a nice boat in protected waters, and I think this is actually the kind of use ASM described:





rwatson, I think Bolger's Fast MotorSailer would use gobs of power since it is a planing power boat design. It's a nice boat but not particularly well suited to electric power.

[ASM]

Hee guys,

Thanks for all the comments.

To Rwatson: the Bolger's fast motorsailer does have a lot of resemblense but, as kengrome says, that is a planning design wich does not plane with 70 HP ! Though since it was designed as a sailing boat, it might run efficiently at low speed too...

The Duck flat wooden boat was, as said, also part of my finds on the net which gave me the idea and confidence that what I wanted was possible. I have however, like Rick stated, used the Atkin tunnel-stern Seabright skiffs design in the link as well.

Basically it looks a lot like the 'trimaran' Rick has put together. I had envisioned it a little different, not much. As can be seen in my original post, I had blunt sharp bow, though the underwater one could be as shown by Rick if that gives better efficiency. In fact the bow both under and above water is just like a piece of pie, so also no odd double twist for plywood. The sheer (?) would start above waterline and from flat bar twist into a slightly inverted V shape, like the Atkin's. So in fact my two 'sponsoons' are triangular shaped because of this slight V. Another option would be, and much easier to make, a flat section like Rick drawn, but make the two 'sponsoons' out of pre-cut H80 foam which one stick under the flat bottom, then glass it over with the rest. In my 'ideal' non naval architect world, I see this as a easier to build and a positive influence on pushing the water towards the propeller, thus increasing its performance.

Rick, thanks again for your work, I see you have worked on it again and made it more and more realistic. The problem I have as a beginner, are the V-curved shapes of the bow. Attached I have sketched something I think is easier to make and a little more in line with my original design, though it might be stupid and downgrading the performance and endurance.

Just for my understanding, the first 'tri' you drawn, the grey areas are the wetted areas. These are the surfaces needed to float this boat at the given displacement right ? And can I assume that the position if these 3 areas is the base for a good weight distribution on the water, so moving the outer contact surfaces aftwards will effect the longitunidal stabililty ? So in other words, by increaing the beam and keeping the same weight and location of the wetted areas, one could have a bigger beam without too much influence on the rest ? (I guess the keel hull needs to be the same and therefor the bow through the water does not change in width, thus not decreasing performance ?

[Guest625101138]

ASM
The ASM10 is a monohull straight from Godzilla with a little licence to reduce length and make it developable. The performance numbers are for 80% efficiency prop and the developable hull.

I have attached the lineplan for the revised ASM10. This would be very easy to build using flat pack construction. The strip that forms the flare coming up from under the side wings of the hull may need to be laid up with only one side glassed to enable the curve and then finished off.

There are subtle diiferences from the original lineplan plus more detail.

I am working on the bases that the outrigger hulls are just touching the water so do not contribute appreciably to drag. This is quite different to the Atkin hull - much narrower centre hull. Also the submerged wings on the Duckflat boats would add considerably more wetted surface.

I have not done any work on the ideal placement and shape of the outriggers. Also I have not checked the stability curve. You may require wider outriggers to give good initial stiffness.

Rick W.

The

[kengrome]

Hi Rick,

At first I couldn't understand the benefits of going with such low wing decks and amas that only just touch the water, but now I think there are good reasons for it ... although higher wingdecks would still be an advantage.

If you're using FreeShip 2.6 can you send me your .fbm file? Or if you're using a later version or Delftship can you export it as .fef then send it to me? I would like to join in this discussion with an example or two based on your work, and it will save me some time if I can avoid recreating your hull from scratch ...

[kengrome]

And Rick, a couple of questions:

1- What is the purpose of the rocker forward in the box keel? Is this to provide some lift to the hull, or to aid in beaching ability? The reason I ask is because it is all underwater, so it seems the forward box keel might be more efficient as a purely flat bottom with no rocker forward and instead having a vertical knife edge bow. Wouldn't this reduce turbulence?

2- Why didn't you make the aft end of the box keel a knife-edge instead of pinching it out to nothing? Wouldn't a knife-edged aft end better support the prop shaft and streamline the flow better back there as well?

3- I may have been mistaken and I'm sure you know more about this than I do given your extensive experience with long slim hulls, but I've been under the impression that when a double-ended hull is asymmetrically wider aft than forward, it is more easily driven ... yet in the rendered images your box keel looks wider forward than aft. Is this just an optical illusion due to the fact that the box keel pinches out and basically 'disappears' aft? Or is it really asymmetrically wider forward and narrower aft?

[ASM]

Rick

as usual, thanks again for all your efforts, and as seen from the side, this model is indeed as easy to build as I had envisioned.

Wider outrigger, if needed, would contribute to increasing beam as well, a win-win situation ?

The questions raised by Kengrome, 1 and 2, are exactly the wording I was looking for, but again, I am no naval architect. As for item 3, I would say that like a waterdrop, the shape should be a bit ássymetrical to have a as much as possible on turbulent flow of water to the prop.... but I could be wrong.

Looking forward to your inout Kengrome and Rick, and see at which point it makes sense to start a model.

[Pericles]

A very interesting couple of pages, taking the design process a few good steps further than earlier threads on the subject of electric boats. The benefits of efficient power storage are not far off and in a couple of years or so we'll all be unshackled from the iniquitous prices now being charged for diesel fuel.

http://en.wikipedia.org/wiki/EEstor

The underwater lines at the stern of Narrow Boat Hadar nicely illustrate the second point Ken makes.

Perry

[ASM]

Pericles,

I have had this idea in my mind for years now and think the time has come to try it out, as said, the small yacht/ship building in the Netherlands is very traditional (steel mainly) and they are trying to re-engineer an existing design to run on electricity or they come up with ugly/silly looking crafts....

This is why I published my ideas, since I am no naval architect, they were just ideas from reading through a lot of designs and threads here. Once you can create a good looking electric inland (occasionally coastline) vessel which is moderate in price and cheap to run, you could be in for an exponential growth ! From what I saw on this site there are a lot of smart people on here who can contribute to improvements whilst maintaining most of the original (above waterline) design.

Me, I just want the thing to work always, easy to build, no hassle with diesel engines and smells and fun for the family ! And of course, being a Dutchman, cheap to run !

[Guest625101138]

Ken re ASM10
The rocker is the result of unconstrained length optimised for 6kts direct from Godzilla. It was longer but I chopped off a bit.

This hull is a lot more efficient than an Atkin.

I have not spent a lot of time on the stern. Remember it is not a tunnel hull. It is just a long slender hull with outriggers.

The strern treatment would be better suited to an outboard and you could knock 0.5m off the length.

My little Kelly/Mars drive would work well on this.

Rick

[kengrome]

The rocker is the result of unconstrained length optimised for 6kts direct from Godzilla. It was longer but I chopped off a bit.

That's interesting because I figured a plumb bow on the box keel might be more efficient than the one shown ... but if the box keel's bow was not constrained in Godzilla then I guess it already has the most efficient shape. Interesting ...

Thanks for the file by the way. I will plug it into FreeShip 2.6 and do some mods so I can show you what I'm thinking about, assuming the power and internet are available during the current typhoon. Both were out this morning ...

[Guest625101138]

You will see with Godzilla that as a hull gets heavier the optimum tends to get longer with nice rocker providing length is unconstrained. If the length is constrained then the rocker goes flatter and ends get fuller.

Rick

[John in CR]

Considering waves and loads that aren't perfectly balanced or fixed for real world use, as opposed to conditions for competitive rowing, why isn't a catamaran the first choice when it comes to electric boats? I understand that transportability, boat slip or parking widths, and narrow canal use can preclude cats, but otherwise the extreme hull length to beam ratios and stability seem to make them the logical choice, at least from my noob perspective. Is it only that the maritime industry is stuck in tradition more than most, or are the reasons founded in hard science? Is the inherent increase in whetted surface truly so detrimental?

John

[ASM]

John

I have thought about a CAT for a long time as an option too, and I do agree they tend to have much more usable space. Downside is one needs two engines, so more costs though they can be downsized. OK fair, one engine COULD be possible but somehow seems 'odd' on a cat. A real trimaran would fix this with a centre hull engine. But hen comes in the fact that I am new in the boatbuilding, and going for cat or tri in the first go is a little bit too much. It is more complicated work to my mind and more materials and more space needed. Furthermore, birthing here in the Netherlands is not optimized for CAT's, that is, the width is limited or one comes into the big boat boxes and thus overpaying.

Actually the second design I did was just the hull as original posted x 2 , since I do not want high speeds or extreme condition cruising, it can be done I think.

Let's say it's on my list but as a second project perhaps.....

I fully agree a CAT can be more efficient for electric propulsion, but hey, as Rick calculated 1.5 kW for 7.5 kts.... how is that for efficiency ?