Bare hull specifications?

Can someone suggest a source for bare hull specifications? I want to look at hull weights as a function of length and beam so I can evaluate some trimaran design ideas.

Are there any manufacturers that have bare (mono)hull specs online?

 

It doesn't look like anyone has information concerning bare hull weights. Here's an alternate question: does anyone know the weight per square foot of hull for typical foam-core fiberglass construction? (assume LOA between 30-40 feet).

 

I think Derek Kelsall could probably answer that question for you. He can be reached at derek@kelsall.com

Regards,

Pat

 

depends on the design...since a short fat hull will have a very different weight per metre compared to a long thin one....not an easy Q to answer hence the deafening silence.

 

The average American male weighs 160 pounds and is 5' 9". How much does this tell you about yourself?

 

That tells me I'm slightly taller and heavier than average.

 

My point is quite simple, if you are slightly taller and heavier does this mean anything?

The specifications for yachts are much the same. Are you a better or worse version of the average American male because of your weight and weight?

Humans, like yachts are such a complex set of variables that direct comparisons are exceedingly difficult. Now a clever person could set up an evaluation, based on multiple figures, taken from a large pool of yachts, but unless each yacht in the pool has a similar design brief (goals the design was attempting to address) the results are meaningless.

Now this can be done to class racers to some degree, as they've all been design within a "box" of requirements, which tends to focus the design brief considerably. As far as a blanket approach, even for a specific type (like 40' racing catamarans for example) the field will be too diverse for reasonable assumptions to be made, though general trends, fads and approaches could be gathered, if the numbers were consumed properly.

It's likely your extremely generalized question's nature, has put off the majority of potential replies. In other words how do you answer a question such as this.

Most designers assemble information about designs piece meal over the years. I have a large data base for hundreds of yachts. I use them in restoration, repair and comparative purposes. It's taken 30+ years to compile this information. Your sources are plenty; books, trade publications, manufactures, designers, etc.

Research is the hallmark of a good engineer.

 

I would bet that if you looked at ten different monohull sailboats in the 30-40' range (foam core sandwich), the hull weight per unit area is quite similar. Nobody is going to use significantly more laminate than necessary, it's just a waste of money. Based on what I'm finding online it's probably in the range of 1-2 lbs. per square foot of hull surface.

 

PAR

i think you summed that up perfectly

 

How does one manage to build such a database? It seems to me that asking a designer the thickness of his 35ft cat is like asking a lady her weight. One cannot exactly gather parameters just by looking at a boat from the outside. Then again one needs to live close to a number of shipyards to be able to collect a range of data. Even then shipyards tend not to allow anybody in unless he has a boat inside.

Does this mean that a lone designer does not have a hope?

regards

 

Buy some study plans. The materials lists should give you the scantlings and you can cost per square foot or metre from there. As a rough guide to the weight of the glass skins, the glass will soak up its weight in resin.

So, sq foot of glass/resin-foam-glass/resin = weight per sq foot. Also easy to cost this way. Remember, thats the skin only. Bulkheads etc are extra but can be worked out from a set of scaled study plans.

A suggestion: best amount of info vs cost is probably the Farrier study site. You can download the details of 6 foam boats including materials lists and scantlings for minimal cost.

 

"Based on what I'm finding online it's probably in the range of 1-2 lbs"

I think this is where the problem is. A racing cat might be 1 lb (i'm not a designer, so I really have no idea ) and a crusing 2 lb. and at the end of the day you have 1 40 ft boat that weighs twice the other.

 

I tend to hold against that bet........... And I´m a cheater, I do´nt bet if I do´nt know I win.