Trimaran motorboat / stabilized monohull

Transport Efficiency

Refering to my expierience with ZEB 25
it is important to locate the sponsons in the right posisition
and to choose the right bottom beam
before we made up the final design we made many test
the position of the sponsons is very critical
it is hard to calculate this
practical test is the best way

ZEB 25 is designed to FnV 2.0
so at higher speed it can be better than showed in the chart


in the chart your boat are the yellow dots
your boat shold only need 36 hp if properly designed


js

www.sassdesign.net
www.zeroemissionboats.se

 

Yes, you have made me rethink my initial decision, which was based on the concept of selling the boat as a kit, consisting of pre-cut sheets of steel.

If I want to use different materials, I will have to study and dig in to wooden construction though.

How exactly will you go about the build? Will all the wood eventualy be covered with a layer of fiberglass?

 

MWatts / Sandwich plywood or foam

I had fun to work with plywood and fiberglass for the proto.
For the next one I will use sandwich core construction with fiberglass laminates inside and out and uni carbon in some special places. Those foam or honeycomb sandwich are Weigh Less than glassed plywood and I espect 700kg for the 12m hull. You can keep the concept of selling the boat as a kit, consisting of pre-cut sheets of sandwich.

ref : http://www.diabgroup.com/europe/literature/e_pdf_files/man_pdf/sandwich_hb.pdf

 

I don't know the sandwich material. How thick are the plates? Will it bend like plywood or steel? Could you construct a hull like in my design (for instance the twisted bottom plates) from sandwich?

 

I Wonder if the central hull (similar to a Box Keel) provides lift at speed?

As a water ski would?

If it does , do the amas hold any weight at speed , or just stabelize the vessel?

FF

 

FF: Are you referring to my design or Eric's? As far as I can tell, Eric's central hull is very narrow, so I would not expect much lift. I think the speed advantage is mainly in the high Froud numbers.

The central hull of my design is approx. 20 cms wide, which isn't very much either, but I estimate more than Eric's. So there could be a little more lift, but my expectation is not that it will be very much. If you can compare it to a mono ski: you need quite some speed to keep a grown man out of the water.

 

3/4 cm lift at 18 knots with 2 deg hull trim

At speed amas are dynamic stabs only.
I have tried to limit wet surface has much as possible on amas.

 

Box keel and planing amas

Like this one?!
With my expierience, the amas do not hold much weight, mostly stabilizing.
Therefor is the ama position importend, both longitunal and vertical.
And that is related to the designed speed.
Remember that the amas are planing at very high relativ speed, FnV.

js

 

I've read all posts on "faux tri" power boats with great interest. What I have in mind is a 10 m long, 3 m wide boat with a displacement of typically 2.5 tons (minimum 2 tons, maximum 3 tons). Max speed would be 15 kn and typical cruising speed 12 kn.

How should the results obtained or predicted with faux tri hulls of similar length be scaled to get a first estimate of the power requirements for this hull at these speeds?

Erik

 

Eric
I have made quite a few stabilised monohulls in the form of pedal boats. This is a nice scale to work with and gives me a lot of feel for how the hulls perform. I can get 6kts with 130W from the latest. I have been using GODZILLA to generate the lowest drag hull form for the design displacement and power level. This is the latest:
http://www.boatdesign.net/gallery/showphoto.php/photo/15138/size/big/cat//ppuser/18624

My eventual aim is a solar powered coastal cruiser. One variation linked here is designed for 8kts with 1kW, one up:
http://www.boatdesign.net/gallery/showphoto.php/photo/15019/size/big/cat//ppuser/18624

You have achieved much the same results as I have demonstated. My interest is in a zero fuel boat so my speeds are a little lower.

I design and build the complete system. With easily driven hulls like this you can get much higher propeller efficieny using low area blades. I am using ratios less than 10%. There is a lot of information on the pedal power thread on the props I design. The WHIO uses a hand fabricated prop to improve efficiency. With props like this you can get efficiency around 90% compared with about 70% from a typical outboard prop in your speed of interest.

Rick W

 

Pics collected on the WEB

Pictures are better than words so voila my collection
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Some new pics of Crossbow 12m









Toilet on front, then shower, then master bed room and guests beds.

 

Have you guys seen pix of the one John Shuttleworth is building...40m.

Tad bigger than what u guys are after,but cool to look at:


http://www.john-shuttleworth.com/power-40m-19-windows.pdf

http://www.john-shuttleworth.com/P41-v9-back-veiw.jpg

http://www.john-shuttleworth.com/P41-v9-front-veiw.jpg