Long - Skinny Power Boats

[Ad Hoc]

so your requirements need to be 'drawn' up...otherwise it is a list...just a wish list. You need the list, your SOR, to be made into a concept that some basics can be established...so you need to draw up the layout, does it fit, do u need a longer hull..do u need a catamaran..do u need a tri...too many what if's...you can only draw up what u want....you ahve to start somewhere....you're at the point where if you don't....it'll just remain a dream in words rather than reality.

[Ad Hoc]

"...I think Ive made some good decisions go find myself a competent NA and let him do a cost analysis.."

A shipyard will give you cost.

A competent NA will just scrutinise your work and then tell you if it will work, not pay lips service to your wants. If you're serious, you need to get the basics with a NA now, not later.

[Boston]

Ill know what I want when I figure out what works best
and Ill be a whole lot happier figuring it out by consensus in a group setting than going on one mans opinion
no shipyard brother
if its anything like home building
most of those guys look like they just got out of prison and I wouldn't trust em to build an outhouse
no thanks I am fully capable of building it with my own crew under the supervision of the NA

thing I always hated about clients I was designing a house for was that they were generally clueless about how things go together and they tended to want mutually exclusive design concepts
Victorian porch elements on a post modern house for instance or a multi story house that had 9' ceilings and looked like a single story from the outside or that you couldnt see from a mile away

my deal with designing the boat is to strugle out the various components and get an idea as to what I want
basically if yacht design is going to be a no right answer science
then some of these decisions will be made by consensus of opinion in a place like this were the opinions are generally informed ones
generally
not sure if you have been over to the climate thread yet
now that is one seriously misguided group of people

point is that each design element has made itself self evident the more I got into it
this one will as well
box keels are supposed to be pretty dam efficient
tri hulls are supposed to be pretty dam efficient
one will be better in the open sea than the other
one will get better millage
bla bla bla
so I thought Ild start with the millage
soooo
whats the deal

two boats of the same length and weight
one a box keel
one a tri hull
given the same power plant
who wins for fuel efficiency at the same speed
and
whats the speed
Ild like to see say 15 kts

[Guest625101138]

Originally Posted by Boston

does that 5t represent 5 short tons or what is that
42000 lbs = 19050 kilos if that helps

.....

Boston
You have to iterate with this. You need to set out the requirements such as cruising speed, range, accommodation, amenities, tankage etc.

Taking 19t as the upper limit the lowest drag 18m hull form gets quite unrealistic. It has a draft of 1.9m and beam of 720mm. The power on the hull has now gone up to 64kW.

If the draft was constrained the power will go up again.

The important thing is to set out the things you want from the boat and go from there. The problem with this concept is that you are starting from scratch so there are no readily available examples that you can take data from.

Rick W

[Ad Hoc]

"...my deal with designing the boat is to strugle out the various components and get an idea as to what I want.."

Well, you have a basic SOR. But you need to progress from this, otherwise you be like "..clueless about how things go together and they tended to want mutually exclusive design concepts.."

Because design is just one big compromise. Until you decide what is important, and list them in order of merit, ahve them drawn up on a general arrangement that satisfies your basic concept of what you want, you shall be clueless too, to why the reply is as it is. You're going around in circles.

Hence, draw it up yourself, or get someone to do it for you, but you MUST get it drawn up before talking any details and making any radical changes/decisions based upon, what...er...um...another idea that's unproven for your boat!

I cannot give any more advise, until you get your boat drawn up....it is meaningless to do so...

[Boston]

ya that hull doesnt look like its going to work at all
there is a solution in there somewhere just got to find it

speed should be 15 knt
range should be 2000 miles
fuel load is 7 tons to make that 2000 miles
4 people in two dbl berths
4 people need to to 7.5 days food and water so call it 1500~2000 lb of supplies
that makes about 8 tons of cargo including fuel
so there is about 26000 lbs of boat involved
assuming 42000 ttl

lets just stick to the basic comparison to hull efficiencies for the moment and Ill see how its incorporates once it is determined what is best under what conditions

what happens if you make that hull wider
say enough to get the draft up to about 1 meter
then reduce the primary hull to only carry say 75% of the ttl disp

think Ild want the primary hull in the trimaran configuration to hold say 75% of the weight
so that 42000 becomes 31500 and the two outer amas hold about 5350 lbs each
in a 60' vessel thats still going to be a pretty long skinny hull
each one is long and skinny in itself so although Im paying in surface friction Im saving in pressure of depth

[Ad Hoc]

"...lets just stick to the basic comparison to hull efficiencies for the moment..."

well, you can discuss with Mr.Numbers and get hull forms that displace 5t when your fuel requirements is 7t...or you can forget efficiencies fro now and focus on what is required first.

As I said before, amaterur designers, non-naval architects and those that tap away into programs on their PC will talk about efficiency until the cows come home..why.??..because they have never designed a real boat before and have no frame of reference other than a series of numbers.

It is your choice if you wish to continue discussing numbers, that is your prerogative. But I gave you credit from your post about building for others etc that you understood this concept. Perhaps i'm mistaken....my bad!

[Boston]

I got the concept
had I been designing a house for the first time I would have gone through the same basic process
learn a few things
then go talk to someone
Im still learning a few things draw up some sketches
which I have
thing is its time to get a hull under these numbers and as you yourself said
this is an inexact science
what the sciences do when they have an inexact conclusion is derive a percentage of confidence from a consensus
thats what Im after on this hull issue
some folks will explain what hull they like and why what they do best and where
so on and on
those are the folks Im looking for
I think you underestimate Rick
he doesnt just seem like a pencil pusher to me as he's got more screwy designs he's worked through to floating than a lot of folks in here
thing is being as how this is an inexact science a conglomeration of opinions is going to paint a better picture than just one
should I go bother 10 designers into some kind of design contest
or should I just join a design group and learn a few things before Im ready to rock and roll
besides
this is a great way to interview possible NA's for the task
got some great folks hiding behind this computer screen
one of em just might end up making a few bucks off me who knows
I got lots of time before im ready to move back to the coast and start building

thanks though
I appreciate the help
that hull resistance formula will come in handy

comparing basic hull configurations
say long skinny hulls
is what this thread is all about though isnt it
seems like an excellent educational tool that might just allow me to make a better decision in the end
so I do appreciate the help
B

[Guest625101138]

Originally Posted by Boston

ya that hull doesnt look like its going to work at all
there is a solution in there somewhere just got to find it

speed should be 15 knt
range should be 2000 miles
fuel load is 7 tons to make that 2000 miles
4 people in two dbl berths
4 people need to to 7.5 days food and water so call it 1500~2000 lb of supplies
that makes about 8 tons of cargo including fuel
so there is about 26000 lbs of boat involved
assuming 42000 ttl

lets just stick to the basic comparison to hull efficiencies for the moment and Ill see how its incorporates once it is determined what is best under what conditions

what happens if you make that hull wider
say enough to get the draft up to about 1 meter
then reduce the primary hull to only carry say 75% of the ttl disp

think Ild want the primary hull in the trimaran configuration to hold say 75% of the weight
so that 42000 becomes 31500 and the two outer amas hold about 5350 lbs each
in a 60' vessel thats still going to be a pretty long skinny hull
each one is long and skinny in itself so although Im paying in surface friction Im saving in pressure of depth

Boston
Once you start getting up in weight there is advantage spreading the load across more hulls for a length constrained vessel. This is something that Matt Marsh arrived at when he developed the faux-tri concept for his needs. Although his ended up as a conventional trimaran.

If you reduce the power requirement then the fuel load comes down accordingly.

It is useful to set up a spreadsheet that sets out your requirements. This way you can link dependencies. Displacement is an important requirement to narrow down. Some things will not change through the iterative process as they are set and independent of other factors. Others will. A hull that is easily driven will have lower forces on the propulsion system so mountings get lighter. The engine will be lighter. You will need less fuel.

At some point you need a complete list of all the items in the boat to build an estimate. Right now their weight is the data required.

Rick W

[Boston]

the original numbers are all for that old elco
so my thinking is that by optimizing the hull the fuel load and weight can only come down compared to a hundred year old design

[yipster]

i'm trying to attend a session and this tread was on top, anyone "in" here
Nigel Irens http://www.proboat.com/ June 10, 1 pm US EDT and Live: Designing Fuel-Efficient Powerboats
i keep gettin "your allready registerd for this" but cant get in
so what am i doing wrong how to get in later up to 90 day's after..
anyway, here the masters filosofie on LDL http://www.nigelirens.com/

[Guest625101138]

Originally Posted by Boston

the original numbers are all for that old elco
so my thinking is that by optimizing the hull the fuel load and weight can only come down compared to a hundred year old design

Boston
Do you intend to build the boat yourself?

Is unsheathed wood your material of choice?

Are you wedded to the steam propulsion?

If these are criteria for the boat then they need to be included in the design requirements.

Rick W

[Guest625101138]

Originally Posted by yipster

i'm trying to attend a session and this tread was on top, anyone "in" here
Nigel Irens http://www.proboat.com/ June 10, 1 pm US EDT and Live: Designing Fuel-Efficient Powerboats
i keep gettin "your allready registerd for this" but cant get in
so what am i doing wrong how to get in later up to 90 day's after..
anyway, here the masters filosofie on LDL http://www.nigelirens.com/

The first link just loops. I have no idea why some sites do this.

The nigelirons link has some nice concepts. The little clip at the beginning of one of the LDL designs looks good.

I like the way the LDL vessels slice through the water. I have recollections of beamier boats slamming into even moderate seas no more than 1 to 2m high. Absolutely bone jarring. I expect the same conditions in these fast LDL hulls would be less severe.

Rick W

[Boston]

Originally Posted by Rick Willoughby

Boston
Do you intend to build the boat yourself?

Is unsheathed wood your material of choice?

Are you wedded to the steam propulsion?

If these are criteria for the boat then they need to be included in the design requirements.

Rick W

most definitely
I just won a contract to do a black lacquer front entry on one of the old Victorians down town. I had to talk em out of a black lacquer hand rail around the deck and they are talking about doing the deck in black walnut although my vote is for baked poplar, its cheaper and better in this application. Ill be hand turning the rail components and the spindles in the same material. I think Im capable of building just about anything and have from highrises to antique English conservatories, my skills are not the issue its the vagaries of yacht construction that will require I hire a decent yard manager/NA to oversea each aspect of the build and double check my work similar to the inspection process Im used to as a builder. I have no intention of winging it nor do I plan on ignoring the advice of folks who do this for a living. I will also not be pressured to begin or throw my hat in with anyone until I am comfortable that I clearly understand the entire process and why each decision is what it is, which is pretty much why I joined this site.

I have no decisions set in stone and believe that this process needs to be an organic one that is allowed to grow the more I learn

steam propulsion is a strong contender but not the only one Im considering
so far its main draw backs are the mass of the fuel and the blazing fire in the bottom of what amounts to my life raft
course each fuel type has its draw backs

I am glued to the idea that I will not start anything untill I have all the funds fully available, no bank, cash on hand
which means I earn it off my trade account ( I had a stellar day by the way )

Im all about low embodied energy
wood meets that need
if another material can be shown to be as easily reparable as readily acquired and as comparably cheep then I will consider it

I plan on using natural glues wherever possible and only encapsulating the last layer of the double diagonal planking in epoxy under paint and copper bottom
Im however pretty well set on it not exceeding 60' length 4.5' draft and 14'beam although a little smaller is ok
I prefer to remain flexible throughout the process in order to incorporate the best of all worlds

[Guest625101138]

Boston
Your strategy is sound apart from the day trading aspect. You might get lucky and actually be one of the few that make money.

I started with pedal boats to learn about efficient hull design and propulsion at a scale that is fun to use. After I sold my last yacht I began building model boats but i did not find them highly rewarding. Playing with pedal boats has taken me in unanticipated directions. Not a lot of new stuff but ideas and knowledge that are not widely known.

Rick W