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  #2831  
Old 12-16-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by outbound View Post
That's a great question. Paulo tells us what's available. Bob shows us what's possible. But there hasn't been a discussion of what we really what. I mean not on the zillion dollar one off sphere but if we were designing a production or small run production boat. Of course would need to divide the discussion into
day sailor
coastal
blue water
high latitude
or like divisions

Still, would be a interesting discussion.
what material
what hull shape
what appendages
what size
what sail plan
what interior features

?anybody want to join in?
By the time my first boat hit the water , I had along list of things I wish I had done differently . For my second it took tan years to get to that stage . In my current boat, after 29 years of mostly full time cruising in her, there is very little I would do differently.

Definitely blue water and high latitude capable . I believe in designing and building all sail boats over 265 feet with that capability. If I don't use her that way, some future owner may .

Definitely steel. The fact that it is increasingly popular with experienced offshore cruisers ( unlike the marina queen crowd, who believe everything the industry tells them to believe ) reflects the reality of long term offshore cruising. ( read Jimmy Cornell's book on offshore cruising)
Single chine does everything a cruising boat is required to do with out the huge expense, and fillers of rounding steel .

Twin keels and outboard rudder, hung on a very strong skeg, which is also the engine cooler.

30 to 36 feet . Larger boats tend to hang out in main ports, while smaller boats , being so much easier to handle, get away a lot more, and see a lot more places.
Cutter with removable staysail is so well proven that it is almost universal among offshore cruisers. Variations from this have not proven advantageous in any substantial way. It also increases the availability of used sails, often in almost new condition, at less than the cost of materials.

Interior? Bunks which can be used in offshore conditions, and an interior which works when the boat is well heeled for weeks on end . Enough insulation and a good heat source and inside steering, to make the boat useable in both tropical and high latitude conditions , year round.
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  #2832  
Old 12-16-2013
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Re: Pros and cons of steel sailboats

"after 29 years of mostly full time cruising in her, there is very little I would do differently."

Ahhh, the active, creative mind at work.

More like in irons.

Brent: did you ever get your package?
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  #2833  
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Re: Pros and cons of steel sailboats

Great answer Brent. Too the point and speaks to your needs.
For me, I have no interest in high latitude sailing been cold and scared often enough to fill my life time needs. Neither do I want inside steering as I've spent enough time inside and don't want to harness and dress every time I need to tend the boat.. I do want to be able to get out of the weather. So a hard dodger suffices. I like to sit at anchor under the dodger with my morning coffee even when it rains.I love the look and ease of a split rig.

material- solid fiber but lay up to include modern materials to increase impact resistance. Still like a solid layup as easier to fix should need arise. solid copper laid in as fish scale pattern. ( SSB ground and no bottom painting.)Synthetic core in decks is fine. NO exterior wood. Interior wood all solid. NO veneers. Blond teak is pretty forever.

watertight bulkheads forward to allow safety and storage of sails, fenders and other light stuff. watertight bulkhead aft in front of rudder posts
high aspect ,balance spade rudder as design and materials have moved along to the point they are as safe and strong as prior skeg hung. The gain in feel and efficiency is worth the expense. But would want top bearing/rudder tube above waterline.
Split rig- either double headed true schooner or ketch. Ability to run all sail controls from cockpit.
high aspect lifting keel. Might go with twin rudders to allow drying out on tripod of keel and rudders.
true sea berths- at least one either side in saloon, small double in quaterberth and island queen forward ( to have fun and snuggles with wife when at anchor)
c shaped galley to allow cooking without getting burnt or using straps. Deep, deep sinks. Two heads. separate shower room. work room.
hybrid propulsion on z drive placed just aft of keel. No need for thrusters. Prop can "free" spin and charge batteries Solar panels on top of hard dodger and Bimini with two wind generators deployed just below mainmast spreaders with ability to bring down to the deck in very high winds. Aft deck set up for integral life raft locker, strong points for JSD and storage of drogue and Hydrovane. Integral ladder to deck or sugar scoop with walk through. Accomendation for dinghy when passaging ( ?recess in fore deck or incorporated into stern).
Forced hot water heat. dehumidifier +/or AC with zones
"keeling cooling" for all engines incorporated into hull design to decrease parasitic drag but with excellent mufflers no open dry stacks
Number of hull piercing decreased by using manifolds and those present in sea chests or being standpipes.
As much natural light and ventilation as possible but no hull portlights ( still think they are ugly and dangerous)
Interior thought out so a place for everything and everything in its place becomes easy.
cockpit drains straight off stern, side decks/ house drain in to funnels in cockpit. Diversion of this to tank to allow fresh water collection.
Under 50' LOA to allow passage through Panama without additional assistance or fees.
my .02 cents
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  #2834  
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by MikeJohns View Post
If the builder converts 3/16 steel plate to 1/4 alloy that’s only an increase of 1.3 times which will be a little weaker than steel but not alarmingly so.

Talking common boatbuilding materials. Alloy needs to be 1.4 times thicker that steel to have the same resistance to buckling. Stiffness scales linearly to Youngs modulus and by the cube of the material thickness. Young modulus or stiffness (desigated E in GPa) of most boat building alloys is around 70 and steel is 200. so for the same thickness alloy is only 35% as stiff (for 30% of the weight). If we take the cube root of (1 / 0.35) we get 1.42 as the required thickness increase. Or one half the weight of the equivalent structural material for the hull for 1.4 times the volume of material.

Alloy makes sense for lightweight boats and can be further lightened and made stronger by adding framing since deflection also goes by the cube of the span. So halving the span reduces deflection by a factor of 8. That’s why with alloy you juggle the skin and framing to find a good balance of strength and weight.

But novel alloy structures also need a careful analysis to ensure that not only material stress is within fatigue and buckling limits, but weld stresses are below the fatigue stress allowances. Alloy should also be professionally welded. It’s the worst material for the home builder to attempt to build in and it’s very easy to produce nice looking welds which have no penetration and can fail easily.

But I think you’d be daft to build an alloy Brent boat, you’d never recoup the material costs in resale. You’d buy a used Brentboat for less than the alloy cost.

It would be much more sensible to opt for a better designer and build compliant to ISO or some class scantlings. At least they catch the design pitfalls which can be numerous. With alloy the devil really is in the detail. You would also have a much better cost to strength ratio.

You find that most common materials have quite similar stiffness to density figures or what’s called ‘Specific Modulus’ Lighter materials have the benefit of being able to increase stiffness with thickness at a much greater rate than they increase total mass. But lot of boats don’t benefit much from a lighter hull construction particularly if they are a heavier type of vessel by design. Alloy does corrode less but a hot zinc or aluminium sprayed steel hull (internal deck and even topsides) comes close in durability if you can afford it.
Span has nothing to do with what direction the framing runs in . Otherwise ,one would have to believe, as it appears Mike does, that if you take a flat plate with stiffeners running vertically, and turn it 90 degrees, so they run horizontally, the plate immediately loses all strength, and you have two options to regain that strength . Either turn it back upright, when it will immediately regain it's lost strength ,or cut the stiffeners off and re weld them back on, running vertically.
Sea captain and cruise ship designer Emanuel ( at sealegacy.com) said they have calculations for running stiffeners either way.
With the Van de Stadt 34 , frames are structurally irrelevant, as the chines, far stronger than frames, are close enough together to give far more strength than any transverse frames could ever give. They are merely there to appease those who are incapable of thinking of structural strength in three dimensions. Span in that case, is the distance between chines. Longitudinal curve takes the place of transverse framing, when it comes to strength and stiffness, doing a far better job of it, without the hard spot, point loading, and increased suceptibility to holing of transverse framing and thinner plate. Ditto longitudinal stringers. The plate support of transverse framing only goes a couple of inches either side of them. Chines are far stronger, in that they maintain the curve of the topsides , adding far more strength that the merely local stiffening a couple of inches either side of transverse frames .
Thinner plate with more framing has far greater chance of being holed on a shipping container, or a sharp rock, than thicker plate with less framing. It is also far more expensive and labour intensive to build, and far less forgiving when it comes to corrosion. .It is also much harder to eliminate distortion in.

Many make the common mistake of confusing resale price with resale value. Resale price is what you can get for a boat. Resale value is the difference between what you can get for a boat, and what she cost you in the first place . The higher the cost of building the boat, the narrower the gap between the cost of building and the resale price. My first steel boat sold for over 4 times what she cost me to build. The first 31 I built, the owner sold for three times what she cost him to build. Both buyers felt they got a great deal . It is not uncommon for some to spend an extra $40 K to increase the resale price by $20K, a net loss of $20K.( negative resale value)
The gap between building cost and resale price of an aluminium boat and a steel one would usually put the aluminium one at a distinct disadvantage. While the resale price of aluminium would be greater, the gap between price and cost ( resale value) would be far narrower than with steel. Aluminium could well work out to a net loss ( negative resale value.)
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Last edited by Brent Swain; 12-16-2013 at 06:23 PM.
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  #2835  
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by MikeJohns View Post
Well this is important because you may dupe someone into building something dangerous.



But that’s not the only boat it happened to is it ! It was an illustration of your approach to designing by mistakes. I’m just illustrating that your intuition was incorrect. You initially thought it would be strong enough because of the curvature, although any designer worth his salt could have foreseen the weakness and the consequent buckling of the supporting plate. Something you didn’t grasp until it happened. I think it’s a good example of where some sensible engineering would have helped you from the start.

So you modified the plans after it had happened to other boats.
Now you are pretending it only happened to one boat in extreme circumstances after you altered the plans and wrote this .

"Given the tendency for the trailing edges of the twin keels to be driven up into the boat when they collide with a rock, and the fact that they are far enough back to be under the pilothouse floor in the 36, putting a 3/16th plate web across them would reinforce them without being in the way of anything. The top of this web could be T'd with a piece of ˝ inch by 4 inch flatbar, making it extremely strong."



What exactly does this have to do with your earlier designs rotating their keels up into the boat ?



But you had nothing to do with these designs, and you can’t say what framing was used, you are just borrowing them because they started life as origami, not frameless. They have exactly nothing to do with scaling your frameless designs.



No you are being deceptive again I'm not saying your boats under 36’ are not strong enough. I said a scaled up design sans frames wouldn’t be strong enough.

I have shown that pre welding the longitudinals flat and then pulling them into a curve along with the plating is weaker than post welding after foldup and I showed you why. So your method is weaker than you could achieve with the same material, its why your designs will dent easily.

If you pre stress something its already under load, when you push in the middle of that member it deforms more easily and again I showed you and explained why. You had no comprehension about stress reversal nor about buckling. You still don’t. The internal longs cannot stay in compression under load, if you push on the hull they can only work to resist the load by going into tension because they are not in enough of a curve to be self supporting like the arch. So by pre bending them along with the plate you make them weaker, they want to straighten which assists the load in deflecting the side of the hull rather than resisting it.

That the longitudinals are arches always in compression is the whole basis of your strength argument which is simply wrong.

This in important because it’s easy to show that you cannot scale your boats to 60 feet as you claim. Simply because your structural arguments are completely flawed and based on intuition. I offered to model a hull and give the imploding depth in a bow dive, you didn’t want to know.

Any frameless design scaled much over 36 feet will start to get quite weak without some transverse framing. I’m still happy to model it if it saves someones bacon.

So save your 3 knot collisions in sub 36’ frameless origami boats, that's where it works, I don't have a problem with that. Even if you design weak boats for the material used they may well be strong enough becaue the material is so tough anyway.

Anyone who understands structures can explain to you why shell buckling renders thin shell monocoque unsafe if it’s simply scaled . You can ask any naval arch mechanical or marine engineer. You’ll get the same information. Try it we are all approachable.



Again what does this have to do with scaling your design or your misunderstanding of how structures work exactly ?

Thinner plate with a lot of transverse faming is less likely to be holed than thicker plate with less framing?
Presser of longitudinals outwards, reduces its ability to resist inward pressure?
Only one of my boats, who's builders ignored my plans, has ever been holed behind the keels, and that at far above hull speed on a solid rock, yet you claim, from Australia, without having ever seen any of my boats, to know of many more that I am not aware of ,and you claim I am being deceptive?
You claim that logitudinals, arcs, under longitudinal compression, are not under compression when faced with inward pressure?
Man what a crock.

Someone without the ability to comprehend such simple basics, is definitely not a reliable source of any info on the structural factors in a metal hull.
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Last edited by Brent Swain; 12-16-2013 at 06:42 PM.
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  #2836  
Old 12-16-2013
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Re: Pros and cons of steel sailboats

Out,

WHile I like the comments about your dream boat, I can not come up with a picture in my mind as to how the boat should look! You've rattled off all the what you want, but nothing to give a designer a picture other than a fixed dodger. You could end up with all that you want, but nothing as far as hull looks go! Maybe I am missing something.....

At least with Johns and my start, one has an idea on the general look of the hull, speed potential etc.

Marty
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  #2837  
Old 12-16-2013
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Re: Pros and cons of steel sailboats

What would I like ? I would like a few of you all to look at my thread in learning to sail ( FJ open stern or transom ) Maybe Bob or PCP Brent.. Wish I saw that Wolf en ease from the full keel vs fin keel thread.
I like that you all do not agree. Worst thing is a bunch of yes men in a group you always know the answer

1st I would like a boat that floats regardless of how much water gets in . Etap had this going for them. The boat should be the life raft.
2nd I want a boat that is stable with in reason to be able to sail to the wind and have a little speed.
3nd I want a boat that you can get dry You can hand bail or pump it out. It will not be scuttled full of water. So many boats if they were on their side and the tide came in went down the companion way the boat is on the bottom. pooped or breached with an open companion way The boat is on the bottom.
A boat should float and be able to dry out.
4th what about all the leaks? thru hulls, chain plates, hatches , Deck to hull
5th my comfort if you have the first four this is going to be easy for the next 5 I am not going to sink I can be dry and get dry I am learning how to sail. Swimming is not sailing. Dry boats are the best boats.
Good Day, Lou

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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by Brent Swain View Post
Span has nothing to do with what direction the framing runs in . Otherwise ,one would have to believe, as it appears Mike does, that if you take a flat plate with stiffeners running vertically, and turn it 90 degrees, so they run horizontally, the plate immediately loses all strength, and you have two options to regain that strength . Either turn it back upright, when it will immediately regain it's lost strength ,or cut the stiffeners off and re weld them back on, running vertically.
I have no words. This statement is a true exhalation of ignorance.

Beautiful.

Quote:
Originally Posted by Brent Swain View Post
Many make the common mistake of confusing resale price with resale value. Resale price is what you can get for a boat. Resale value is the difference between what you can get for a boat, and what she cost you in the first place . The higher the cost of building the boat, the narrower the gap between the cost of building and the resale price. My first steel boat sold for over 4 times what she cost me to build. The first 31 I built, the owner sold for three times what she cost him to build. Both buyers felt they got a great deal . It is not uncommon for some to spend an extra $40 K to increase the resale price by $20K, a net loss of $20K.( negative resale value)
And this one...stupendous. Why, Warren Buffet would KILL for a 400% return! Maybe I should fill him in on the incredible investment opportunity in steel boats.

Brent...your shoes are calling...

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  #2839  
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Re: Pros and cons of steel sailboats

I just asked Brent if he had received my package. Can't bother to reply.
Somebody should have taught him simple manners.
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  #2840  
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Re: Pros and cons of steel sailboats

Always liked the look of the Murray Peterson schooners. Realize design of hull shapes has moved forward but would like to achieve that look. Would have a single house not split as in many of his designs. But retain dual companionways. Would have bow sprit easily retractable to decrease LOA when necessary. Would use variant of Bergstrum rig with carbon masts so no backstay on main mast. Sail design would appear close to gaff rig without dual halyards necessary.
Bob- maybe he does not have a "package" and that's why he could not reply. Woo, don't often hit below the belt but it was too good to let by.
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