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  #2611  
Old 12-03-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by mitiempo View Post
Mike
I agree with most of your post except for the part quoted. I can't think of any sailboat that cannot benefit from a lighter hull, given adequate strength. Whether a light or heavy design ballast/disp ratio is important. If not ballast, load carrying ability as most cruisers end up overloaded. In a smaller boat, under 45' to 50' it is even more important. .........................
You design a boat based on a list of requirements, target performance is one. Most cruisers for example want reasonable performance and seldom really push their boats on a passage because it's hard on gear and often uncomfortable.

Anyway from a design perspective.... Lets say you have a target waterplane area, displacement range, roll inertia righting moment and utlimate AVS, then you sketch a midship section with the required draft and beam then pick a desirable prismatic coeff and wrap your lines around the above. So the hullform and mass are dictated, then the hull material , fitout, machinery, rig ,stores..... then you go round a few times till it all falls into place....eventually.

Within your weights study one component is the hull material. With a heavier displacement boat the difference in hull material between alloy and steel as a % of the total Displacement can be insignificant, especially as the boat gets bigger.
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  #2612  
Old 12-04-2013
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Re: Pros and cons of steel sailboats

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Originally Posted by MikeJohns View Post
Y...
Within your weights study one component is the hull material. With a heavier displacement boat the difference in hull material between alloy and steel as a % of the total Displacement can be insignificant, especially as the boat gets bigger.
Yes but heavy displacement boats are quickly becoming a thing of the past. Even the type of boats that once used to be high displacement boats are today medium to light boats by 30 years ago parameters.

regards

Paulo
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  #2613  
Old 12-04-2013
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by MikeJohns View Post
You design a boat based on a list of requirements, target performance is one. Most cruisers for example want reasonable performance and seldom really push their boats on a passage because it's hard on gear and often uncomfortable.

Anyway from a design perspective.... Lets say you have a target waterplane area, displacement range, roll inertia righting moment and utlimate AVS, then you sketch a midship section with the required draft and beam then pick a desirable prismatic coeff and wrap your lines around the above. So the hullform and mass are dictated, then the hull material , fitout, machinery, rig ,stores..... then you go round a few times till it all falls into place....eventually.

Within your weights study one component is the hull material. With a heavier displacement boat the difference in hull material between alloy and steel as a % of the total Displacement can be insignificant, especially as the boat gets bigger.
I can see the hull weight means less on a Colin Archer or Westsail type design but it still takes away from ballast weight even on those designs. If it doesn't then you need more sail area as the weight has increased and with more sail area you need more stability (ballast) to stand up to it.....

I don't think any reputable designer would say that hull weight is not important. And as Paulo states above the heavy boats are really not built today in any number.
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Re: Pros and cons of steel sailboats

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Originally Posted by PCP View Post
Yes but heavy displacement boats are quickly becoming a thing of the past. Even the type of boats that once used to be high displacement boats are today medium to light boats by 30 years ago parameters.

regards

Paulo

There are always trends, and heavy boats are expensive so there's a sweet spot for manufacturers where scantlings are not onerous and generous sail area to Displacement is achieved at lower cost. And they are the certainly boats of choice for a lot of people and they suit some sailing lifestyles admirably.

The heavier the boat the greater the loads the the more costly the material and the larger the required sail area for the same performance. But the flip side is greater comfort both at sea and at anchor. Also a greater internal volume and an increased 'homeliness' feel of the boat, and alos the greater it's stores carrying ability.
But not a good cash cow for production boat builders because most of the target market cross bays not oceans .

They are certainly not becoming a thing of the past, just they suit a different lifestyle to the raft of production boats that fill marinas in the clement sailing areas of the world.

Look at the sailboats in my area where any passage offshore ( and often coastal) is 'boisterous', probably close to 70% of cruising sailboats are medium heavy to heavy displacment and nearly all the offshore cruising boats that cruise into the Pacific from here are. Popular designs from NZ and Australian designers abound here. Multihulls are almost non existant here, rough water strong variable winds and good deep anchorages and few marinas, conditions that are often the hallmark of higher latitude sailing around the globe.

In other areas with more benign conditions you'll hear the multitude of multihull owners declaring that monohulls are a thing of the past. Monohulls carry ballast and weight is bad..............

Last edited by MikeJohns; 12-04-2013 at 06:53 PM. Reason: clearer punctuation
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Re: Pros and cons of steel sailboats

Thanks Guys- Enjoyed the discussion of Al my last post precipitated which encourages me to try again.
I truly, truly love my boat so please don't take this the wrong way. If I had no financial restrictions I would build a one off utilizing modern wood epoxy techniques. With advancement in fabric technologies and available of woods from around the world I would have hull construction derived from an outline offered around 10 years ago in Wooden Boat.
The inner core would be edge nailed strip plank using plastic or bronze nails and a low density wood. This would be coated with double diagonals of appropriate fabric. Then a layer of hard wood laminates appropriate to vector analysis of forces applied. Then on the outside lay up of puncture and abrasion resistant fabric. The design would incorporate integral epoxy coated tanks centrally and water tight bulk heads fore and aft( just forward of rudder(s) posts). Through hulls would all be stand pipes or in sea chests.
At present the military have utilized fabrics as armor. Wood for weight remains an excellent construction material both in terms of strength, acoustic/thermal properties and lack of restriction in developing complex shapes.
Given there are so many sailors with much, much greater resources than I can anyone offer an explanation why we don't get a chance to drool over such boats.
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  #2616  
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Re: Pros and cons of steel sailboats

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Originally Posted by mitiempo View Post
.............
I don't think any reputable designer would say that hull weight is not important. ..............
I said

" With a heavier displacement boat the difference in hull material between alloy and steel as a % of the total Displacement can be insignificant, especially as the boat gets bigger. "

All weight is important and is accounted for in a design but a design starts with displacement as one of the inputs ( underwater shape and volume) so all your weights add up to that displacement, there is an optimal range of position for the center of mass (called center of gravity) . It can be too low as well as too high. It's never a case of getting as much ballast as possible but only of getting a desirable range of righting moments.

If you achieve your target sail carrying ability ( well described as Delenbaugh angle) and get your desired AVS and roll period for the laden craft then you achieve your goal in the weight and stability criteria of the design.

A designer can easily make a sailboat miserably uncomfortable in a seaway by giving it too high a righting moment. Just as a lightweight boat with a relatively large waterplane area can give a very wild ride in a seaway. One reason a lot of would be offshore cruises go belly up after the first offshore leg if they encounter a blow. It can be darn miserable offshore in a light boat in a boisterous sea.

So where you 'come from' with arguments about weight depends on what you want out of a design. The best advice for anyone and especially designers is to sail offshore on different types of boats and see the difference.

Ted Brewer termed a ratio he called the comfort ratio which is worth looking at if you want a rough comprehension of comfort factors.
But naval architecture now has a raft of good software tools to predict boat motion and generate what are called RAO's. It's often an eye opener for people to run a few different designs through something like Formsys Seakeeper and simply show them the difference.
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Re: Pros and cons of steel sailboats

Quote:
Originally Posted by MikeJohns View Post
I said

" With a heavier displacement boat the difference in hull material between alloy and steel as a % of the total Displacement can be insignificant, especially as the boat gets bigger. "

All weight is important and is accounted for in a design but a design starts with displacement as one of the inputs ( underwater shape and volume) so all your weights add up to that displacement, there is an optimal range of position for the center of mass (called center of gravity) . It can be too low as well as too high. It's never a case of getting as much ballast as possible but only of getting a desirable range of righting moments.

If you achieve your target sail carrying ability ( well described as Delenbaugh angle) and get your desired AVS and roll period for the laden craft then you achieve your goal in the weight and stability criteria of the design.

A designer can easily make a sailboat miserably uncomfortable in a seaway by giving it too high a righting moment. Just as a lightweight boat with a relatively large waterplane area can give a very wild ride in a seaway. One reason a lot of would be offshore cruises go belly up after the first offshore leg if they encounter a blow. It can be darn miserable offshore in a light boat in a boisterous sea.

So where you 'come from' with arguments about weight depends on what you want out of a design. The best advice for anyone and especially designers is to sail offshore on different types of boats and see the difference.

Ted Brewer termed a ratio he called the comfort ratio which is worth looking at if you want a rough comprehension of comfort factors.
But naval architecture now has a raft of good software tools to predict boat motion and generate what are called RAO's. It's often an eye opener for people to run a few different designs through something like Formsys Seakeeper and simply show them the difference.
I don't want to start an argument but that is a pretty conservative talk specially in what regards that story about Ted Brewer comfort ratio and also about "The best advice for anyone and especially designers is to sail offshore on different types of boats and see the difference".

You know, many of the best French designers had an offshore racing past with lots of transats over their bellies and certainly they have also sailed old designed heavy boats and what they design as passagemakers and voyage boats certainly would not meat that criteria of yours regarding Ted Brewer comfort ratio.

Regards

Paulo
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Re: Pros and cons of steel sailboats

Gosh, so many experts here it's intimidating.
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Re: Pros and cons of steel sailboats

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Gosh, so many experts here it's intimidating.


But thought provoking!
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Re: Pros and cons of steel sailboats

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Originally Posted by bobperry View Post
Gosh, so many experts here it's intimidating.
Yes, you say a lot of things like that and they don't mean nothing. What about saying what you thing about the subject?

Regards

Paulo
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