My fuel effiencient powerboat project , any suggestions?

[Doppson]

HI!

im currently working on a design for a powerboat which need to be as fuel effiencient as possible. Because it is going to be powered by a powerfull electricmotor 80kw+.

specs.
Production year 2020.
motor plus energystorage package ~550kg, ~1100lbs. currently available. But this will improve through advanced technology. just look at the Tessla Motor company, new rodster.
power: ~70 -120kw, 3phase, 4 pole electric motor.
speeds: 18-30 knots, semi-planning or planning hull.
Runtime/charge: 4-7 hours
usage: To the beach/island and back, on a sunny day
type: a daytrip cruiser, bowrider.

the big problem is of course, the energy storage. im thinking of a hybrid type, with Li-IOn battieries for intial power for planing and acceleation and fuelcells for cruisespeed or only just for recharging the batteries. The technology is infact existing today but very expensive, but the current development advances will make it more offordable in the future.

So, lets not focus too much on the energy storage part.
But I would like to get some help from you guys on making the hull as fuel effiencient as possible

any suggestions??? i will post the changes of the design as it progresses.

have good day!!

// micael

[FAST FRED]

If your'e willing to keep the speed down to SL x 4 , check out the Box keel and Sea Bright threads .

These can beach easily and will be OK with thousands of pounds of batteries.

FF

[Doppson]

Originally Posted by FAST FRED

If your'e willing to keep the speed down to SL x 4 , check out the Box keel and Sea Bright threads .

FF

Hi fred! thanks for the input!!!!
iv'e tried to figure out waht you meant by SL x4, but i still have'nt got it. Can you please explain it for me, im sort of a newbie.

But your right about the box keel, seabright skiff configurations!! they might work!! i have decided to deacrease the the beam to about 80-85 inches while still keeping the hull long and narrow...with a box keel configuration.

im have also been looking at the "Admirals Tender 28" from superior yachts for insperation, it seems to me like a lightwirhgt combination of the two might give my boat an edge.

Another question for you. have seen the "Tender 06" http://www.designboats.ch/html/tender_06.html
It looks to me like it moves through the water with ease, do you agree? maybe that's the way to go?
// micke

[ted655]

Have yu modeled without the side fins (or mini sponson, ever what they are). Just add big radius at the chine (large tumblehome). Gain less underwater drag while keeping yaw stability. What do I know!

[kach22i]

I like the hull shape, we are seeing more and more like this - yours is still one of a kind though. The other hull I'm thinking of is a SES (Surface Effect Ship) recently posted.

The next closest shape is this (I think it's French - stability at speed issues I think):

Are you in a position to wind your own electric motor? You might see if this superconductive wire is in your price range.

Link:
HTS - The Future of Navy Motors - high temperature superconductor

[messabout]

Doppson;
FF refers to a ratio that is based on a long standing equation that is based on wave making and the space between the principal waves at various speeds. That is the Froude equation. "Hull speed" is said to be square root of the waterline in feet multiplied by the constant 1.34. the result is the theoretical speed in Knots. That rule applies mainly to displacement type hulls. Certain displacement hull types have been shown to exceed the bounds of the equation. FF refers to a boat with the capacity to attain speeds that are equivalent to the sq. root of waterline multiplied by 4.

One may ask; "how is it that such a boat can violate the laws of physics?" Planing boats can obviously do so. That is because the planing boat uses hydrodynamic lift to carry most of the weight of the boat and thus not be constrained by the physics of wave making. To complicate things further there are boats that fall into the category of semi planing or semi displacement types. Box keel boats, notably the Seabright Skiff, have shown the capability of exceeding speeds that would be predicted by the classic hull speed equation. There are other designs that do so too. Long skinny boats, such as catamarans are prime examples.

One of the primary requirements of a relatively fast, low powered, boat is light weight. That is a universal truth that applies to boats ranging from kayaks up to world speed record types. That gets us into another pretty well established equation called displacement length ratio. That one is ...Weight in long tons divided by (WL x 0.01)^3 Boats with Low numerical quotients are destined to be the fastest for a given power application.

There is a lot more than these simple equations to consider when designing a boat. A good start toward understanding some of this stuff can be found in "The Nature Of Boats" by Dave Gerr. Additionally, "The Propeller Handbook" also by Gerr. These are easy to read and informative but there are far more scholarly books that you will want to consult as your knowledge cotinues to expand.

[tom28571]

Your hull looks very interesting. There have been some similar designs but none that I know of carried quite this far. There were some called "wave collectors" that go back into the early days of planing boats. Bolger has one with a similar profile without the aft downturned appendages. Without these, it is a hull with extreme warp.

Too risky to just build without some testing though.

[Doppson]

thanks for all the input guys!!!
yes, the 3d model is just in its first phase of design, it will get more into detail and numbers as soon as i figure them out, hehe..
thanks Messabout!! for your theory's, you where talking about box keels and seabright skiffs. Have you seen a "petterson" boat, an old 1920 design, here is a link: http://www.trabatsakuten.nu/batbilde...orbatar_08.htm

Kach221: you were also wondering about my electric motor. a company "ABB" has given me help in deciding choice of motor, it will be a 3phase 4 pole unsynchronios motor which can developed about 160 peak power... i will not have to buy, because this project is just ( for the moment ) a school design project, but i will conduct tests with the finished scale model.

im currently waitng for a new image to be apporoved, which will show some new major changes i made to the the hull......i will post as soon as i get it approved.

// micke

[Doppson]

HI! this is my latest edition on the the hull design version #2. its still just a fast 3d sketch under lunch time. I do know i want to ad some "air steps?" ( as they got on fast speedboats, to the hull to even increase its performance and to decrease the wet area a bit and drag.

here it is! i got kind of rid of the "pontons" on the sides and applied a box keel configuration, im wondering where should it end? will it make "big" difference if i cut the box keel even shorter bak in to the body?
i also decreased the beam to 1,82 m ~85 inches

//micke

[charmc]

Originally Posted by Doppson

Hi fred! thanks for the input!!!!
iv'e tried to figure out waht you meant by SL x4, but i still have'nt got it. Can you please explain it for me, im sort of a newbie.

Micael,

Fred doesn't seem to be back yet, so, hoping you and he don't mind, I'll try to explain. As I understand it, the S/L ratio was first mentioned by William Froude in the 1960's. S/L stands for speed-length ratio. S/L = V/sq rt L, or the boat's speed, expressed in knots, divided by the square root of the waterline length of the hull, expressed in feet. S/L numbers below 1.34 represent displacement hull speeds, 1.35 - 3.0 represent the range of semi displacement/semi planing hulls, and numbers higher than 3.0 represent full planing hulls. The S/L number is a useful tool for the designer, at the very least helping him/her make choices in key design elements. The formula works equally well for lengths expressed in meters, but the numbers for each hull category are different, and I'm not familiar with them. Perhaps someone else here does and can give them to you. Also note that the number doesn't mean much for extremely skinny hull forms, which is why sailing cats and wave piercer/SWATH hulls can go so fast.

For example, let's assume your 7.5 m/24.75 ft OAL boat has a waterline length of 6.36 m/21 ft. The square root of the waterline length in feet is
4.6. This is the number you divide into speed to get the S/L number. In this example, your highest mentioned speed is 30 knots. 30/4.6 = 6.5.

An S/L number of 6.5 means your hull can't reach 30 kts designed as a semi-displacement hull (It probably could, but it would take so much power, it would not be worth the expense). At the low end of your range, 18 kts, the s/l number is 3.91. Fast Fred said some box keel and Sea Bright skiff designs can achieve this speed at a waterline length of 21 ft. These designs have bows much more upright/less rake than yours, so the same overal length might have a 24.5 ft waterline length. That would bring the S/L number for 18 kts down to 3.64, well inside the range Fred mentioned. I'm sure you see that, all other things being equal, the lower the S/L number, the less power it takes to drive a hull at a given speed.

Hull design gets a lot more complicated than that, and there are many people here with more knowledge of boat design than I could hope to acquire in a lifetime, but this can start you in the right direction.

[Doppson]

im been looking at the new hull #2 and still want add something to it. I feel like giving it more cavity, more air underneath.
Keep in mind, this is an design concept project. It needs to be new, innovative or at least testing some new untested idea's. Idea's that normaly wouldn't get to market in x years.......That's a luxuary i got and commercial company's do not.

[kach22i]

I've been seeing a lot of mid hull foils or fins, not sure what they are supposed to do though.

[Doppson]

Thanks Charlie!!!
a very good lecture, i understood it all !!!
i got infact hold of an XLS sheet, planning hull ratio from this forums somewhere( i forget where exactaly) today, but thanks to it i can run som test figures and numbers into it, to figure my basic design out, based on all knowledge i gathered from this particular forum..

This is just great!!! thanks

[ASM]

Hi Doppson

Just wanted to jump in as a newbie, who is playing around with ideas (mostly 'looks'of superstructures) but not have the time or resource yet to try things. Your first hull design rang a bell, it is exactly what I was thinking too, and has the basic elements I had drawn before. I will mail you a sketch of the design I did, though have no clue about hull designs.. I am looking into fuel efficient electric powered boat, inland cruiser, ~8 m long and 2.5 m wide.
I would like the hull to be clean, sharp, esy to build out of plywood sheets and a mixture of the Wally power / Tender 06 and Bolger box boats.. yes I know impossible because of different usages. So a box keel with straight bow and two side pontoons, having the box ending just before the pontoons, making a electric pod possible or a strainght shaft.

[Doppson]

to ASM:
One thing i have learned as a prdouct designer is, Clean sharp surfaces are very easy to mess up, just one little scratch or bulge, bad finish painting spackle etc. on a plain surface can destroy and will destroy the beauty of it.
Don't get me wrong, i like them clean... but its a pain in the **s to make and keep them clean.
send your sketch.. and i'll take a look at it