Swain BS_36 Stability curve

Simply put
BS is rather opinionated, calls black white, but he sure as heck has wound up people who simply have time on their hands .
So he wins
For a backwoods Hick, he surely has soaked up many chargeable hours
For myself, it is amusing,
Sure some poor buyer maybe sucked into forking the old readies to pay for one of his creations, but then people have forked out hundreds of grand for designs that have not worked
Least ole BS we know who he is
Some contributers to this thread, well we know not who they are
Been following with interest because I am quoting on a 41m sailing yacht and I want conformation from indepent source of stabilty.
As it stands the angle of vanishing stabilty , from departure to arrival seems too great

 

What point:?:
That is the problem with you Brent. You make statements factual and believe everyone must believe these fairytales. On this forum there are many professionals posting and please do not insult their intelligence, let alone the average guy.
This type of statements you so often make - origami thread for one - works when somebody come to you for plans - that person is already prejudiced for what ever reason, and just want confirmation from you with just these sort of arguments to oil his/her conscious. A good salesman always tells clients what they want to hear.....even if its criminally wrong

Fitting retro buoyancy is one of my daily chores and the recommended foam we use (boating industry) is an expanded closed cell Polyurethane-RX121 - 44V20 type with a density of 39kg/m3

I will use fresh water as an example and sea water wont really make a difference on this small amount buoyancy. I will keep it simple and repetitive for Brent to follow.

1 meter square 1/8th inch plate (3mm) weight about 23.6kg (1 x 1 x 0.003 x 7850 whereas 7850 is SG for steel)
The "volume" of 1 meter square 25mm foam is 25 liters (1 x 1 x 0.025)
1 liter of buoyancy can float 1 kg in fresh water less weigh of flotation medium which is 0.98kg. The 25L foam can only just float 24kg
With this scenario the claim just float but closer to sinking.
Funny thing Brent, air with basically no mass (these quantities) is a better floatation medium as foam (with mass) you just changed you tune to
But the fact is Brent did not specify foam type and then any argument can be true as AD Hoc illustrated using a high density foam. When making claims, be specific so apples can be compared with apples....

Amen

 

Mr WYNAND
I think we all know that Origami is some sort of intended shortcut, shortcuts do not apply in boatbuilding, there are many ways , but no shortcuts

 

Except for that in the real world, the mast hitting the water would be a dynamic event, with more resistance to to roll motion coming from the sails hitting the water. Also, the mast will not hit the water all at the same time, the tip will hit first (at least it has every time I've capsized a dinghy!)

This nugget shows that you can not count on the inside of a hollow mast staying dry in a capsize event! Ergo (to use a BS-ism) one should actually assume that the mast is full of water as soon as it hits the water, and therefore reduces stability. (Or is JH going to tell us that all BS designs are constructed with 100% watertight masts)

 

If he let his ideals stand on their own merit sure.
He is however one of those who finds it necessary to cite all who do not follow him as being in error.

He has stated that the entire industry is populated by designers and builders who are cheating a public foolish enough to buy the professionally built and designed boats.
Such a position is bound to raise some hackles...


I had the privilege to attend a lecture by W. Crealock a few years back. He began a treatise on his canoe stern by quipping "I would like to state that if 100 boats set the cross the Atlantic, only the one canoe stern vessel would make it to the other side.... Unfortunately I can't say that."

I believe that professionals are well apprised of how many viable solutions exist to meet a particular design challenge. Those with less experience tend to trumpet their one approach to the exclusion of all others.

 

I don't believe this yet, because we're dealing with multi-bodies as the mast enters the water.......the spike at 95 degrees could be erroneous and it needs to be checked in another program........The sealed mast does little for the righting arm length, but it does add considerable area under the curve.

This is with the steel spar specified by Jack/Brent at 7.54 lbs/ft, the original curve was with an aluminum tube of 4.2 lbs/ft.

 

Perhaps I missed it but you need to include the 3 litres of water displaced by the steel as buoyancy. So the steel will "weigh" 21.6 kg when submerged in fresh water.

Above should not be construed as expressing an opinion on the merits of any designs or the competence of any designers.

 

As an engineer you are not very observant in reading postings correctly before you comment.
Brent Swain / Jack said and I quote: "Throw it in water and it will float, marginally." IOW the emphasis is on float and not suspended in a submerged condition. In this case since he used foam in the argument, the impression is it will be supported by the foam on the water....
Btw, submerged the steel plate will weigh 20.77kg if you want to be that specific.

My post was not construed as expressing an opinion on the merits of any designs or the competence of any designers and I never even suggesting it. My reply was to buoyancy claims made and not boat/design.
Having raised this issue, the whole thread is about claims of a specific design and the competency of this designer was challenged over the years on this very forum.

Myself, Im just a qualified boilermaker with 35 years experience (with technical diplomas obtained up to T4, then got lazy), retired steel boat builder and during my tenure at that, spent some three years obtaining a diploma in small boat design from a well known institute in England.
On my CV I can add that I am the first designer to published an IMS design (40ft) in South Africa during 1992 in SA Yachting magazine titled "Simple Concept" .
Furthermore, I achieved 3rd price in the same magazine with a design competition within set parameters with the title "Module Boat". Quite a few other designs were published in local yachting/sail magazines in the 90's.
Im not so well decorated as other designers on this board, but however, when posting, I keep things simple for everyone to understand and not all posting here are designers and engineers to understand technical terms.

Since this thread is about the stability of a certain design and designer and you raised the issue of competency of designer(s), what a good starting point for such persons laying down their qualifications when challenged.

 

I'm not an engineer or naval architect, and a lot of this discussion is sailing right over my head. But it seems to me that a boat designer who includes the buoyancy of a hollow mast in his calculations might be trying to cut things a bit fine....

It reminds me of Ford lowering the recommended air pressure for the back tires of Explorers, to improve stability.

 

I did not challenge your competency or anybody elses. My statement "Above should not be construed as expressing an opinion on the merits of any designs or the competence of any designers" was intended to convey that I wasn't picking sides in this argument.

It's a legitimate point over whether the steel will be in the water under the foam or on top of the foam. The amount of foam needed for the steel to float differs. I don't know how the discussion about how much foam needed to support steel started.

The emotions expressed in this thread is interesting to someone who had not heard of Brent Swain or his designs until reading this thread.

 

DCocky, Brent has a lengthy track record of belittling, insulting and sneering at professional designers and builders. To hear him tell it, everyone in the business except him is not only incompetent and ignorant, but deliberately cheating and gouging the public.

So the hostility you're seeing here has long roots...

 

I agree completely. It also ignores a number of issues:

1. The mast may well not stay watertight.

2. The mast may well not stay attached to the hull.

3. The mast is not free-standing and Brent has made no mention of the mass of rigging wire that holds it up and MUST be taken into account.

Assume a 13.5m stick because that's as close as I can measure it from Brent's book, let's keep it simple and assume the wire length is equal to the mast length even though we know it'll be somewhat longer and therefore mass more. Assume 3 shrouds per side. We therefore have 81 metres of 6.5mm 7x7 wire. Catalog shows 6mm wire to be 0.14kg/m so a bit over 11kg of wire. Assume another 2kg for masthead fittings etc.

The 165mm x 3.5mm wall steel pipe (150NB light wall) is 14kg/m so 189kg for the length. Add the 13kg and we have a mass of 202kg.

Mass of water displaced = pi*r^2*h so:

3.141 * (8.25^2) *1350 to get cm^3 = 288608/1000 to get kg = 288.6.

Maximum possible positive buoyancy therefore in the order of 86kg. This, for a boat with a theoretical displacement of 100X that, is NOISE LEVEL.

PDW

 

Calculations aside, has it ever occurred to anyone to simply tape a one inch thick piece of styrofoam to a piece of plate and see if it will float? I have . It does. Proves it does, far more than any math. Not a huge expense in trying it out. A small piece will do as well as any
The point I am making is that any mast will float if it is sealed, which it should be ,given the advantages it offers. It also makes a mast a lot quieter. I would never suggest that an open ended steel pipe would float ,as some imply I am.
Thanks for all the help in clearing this up ,Tad. You show a definite open mindedness when it comes to correcting past errors, a good recommendation for any designer. .

As Marchage's book " Seaworthiness the FORGOTTEN Factor" points out in it's title. There are many forgotten factors in boat design,any one of which can throw your calculations out of whack from that point on, and are far more complex that todays computers are entirely capable of taking into consideration, or so the computer whiz kids tell me.
Thanks again Tad, for giving us such examples
Nothing better than a simple test ,like taping styrofoam to a piece of steel ,and throwing it in.
We should always look for more such simple tests to test any hypothisis, in the real world.

 

OK, real world test are good. I'm looking forward to the inclining test results for a BS 36. Jack, cant you assist with this?

Its what we need now to compare to the painstaking and pretty thorough theory and calcs in this thread for stability. And they show some reason for concern so it accentuates the need for the inclining.

 

I cannot believe this statement from you Jack /Brent :?: it mystifies my mind (maybe everyone's).
If only you could returned the same courtesy when designers and professionals tried to corrected/ helped you in the past, instead of dishing out insults etc.....

DCocky no offense taken or meant, but Troy2000 summed it up nicely.

This is another typical example of Jack /Brent's tactics to change things to suit his arguments.
First he used AIR for same argument, then changed to FOAM and then was whipped by AD Hoc with a high density foam calculation, then yours truly with calculation with medium density foam.
Now the argument is about STYROFOAM that has very little weight.
I said before one must be specific in a debate to have a sensible discussion and apples can be compared to apples and not to changes one's statements as you go along to suit your particular case.