Importance of Hull Strength and Construction Quality

[44'cruisingcat]

Selective hearing?

[GordMay]

Quoting Jack Hornor, NA:

“... Often the Valiant 40 problems have been more severe than the typical osmotic bottom blistering associated with many production boats of the 1970s and 1980s. My experience has shown a number of Valiant 40 models built by Uniflite between 1976 and 1981 to have severe blisters of the fiberglass laminates, some as large as eight inches in diameter.

Initially the blistering problem was blamed solely on fire retardant resins used by Uniflite. Later research has shown that a combination of sizing used on fiberglass strands chemically reacts with the fire retardant resins resulting in the blisters. This has the potential to be considerably more serious than typical osmotic blisters restricted to areas near and below the waterline. The Valiant blisters affect the entire hull. Most attempts at repair I am familiar with have been unsuccessful, and blisters have redeveloped in as little as two years.

I have heard of several successful repairs, although the solution is very expensive and the last I know of done professionally cost in excess of $60,000. On the positive side, there were 200 Valiant 40s built, and less than 20% have been reported to have severe blistering problems. I do not know of any reported sinking or catastrophic failure resulting from these blisters ...”

Here➥ BoatUS.com: Boat Reviews by Jack Hornor, N.A. - Valiant 40

[44'cruisingcat]

[QUOTE=Jim Cate;1063111]

Originally Posted by Mr B

G'Day All,

Well, that position is about 40 miles SW of Wreck reef and 45 miles NW of Cato Island. The sea floor is fairly even in that area... no seamounts nearby on my charts.

Now, Brian, the ship said that it had been force 6. That's between 22 and 27 knots, and develops 3-4 meter seas. Mate, those are standard tradewind conditions, and with seas from the standard directions (between S and E, just as you describe).

It is very common for novice sailors to grossly overestimate the size of seas and swells, and frankly, I find it very hard to believe in a 10 meter wave developing in that area under those conditions. So, let's just agree that you had uncomfortable conditions and agree to disagree about just how big the waves were.

Jim

Brian did point ot that waves were coming from two directions - so there is likely to have been waves standing on top of other waves fairly often. (The BOM does say in it's forecasts "max waves may be twice the height")

Then add in a bit of swell...

[geoleo]

This topic is very important and the OPS very interesting--my takeaway is-"you pay your money and take your chances,more money may not equate to less chances" "eternal vigilance is a necessity" "take it easy when you can"

[Mr B]

[QUOTE=Jim Cate;1063111]

Originally Posted by Mr B

G'Day All,

Well, that position is about 40 miles SW of Wreck reef and 45 miles NW of Cato Island. The sea floor is fairly even in that area... no seamounts nearby on my charts.

Now, Brian, the ship said that it had been force 6. That's between 22 and 27 knots, and develops 3-4 meter seas. Mate, those are standard tradewind conditions, and with seas from the standard directions (between S and E, just as you describe).

It is very common for novice sailors to grossly overestimate the size of seas and swells, and frankly, I find it very hard to believe in a 10 meter wave developing in that area under those conditions. So, let's just agree that you had uncomfortable conditions and agree to disagree about just how big the waves were.

Getting back to the original discussion: I can say from my own experience in both the Coral sea and the Southern Ocean that surviving the Coral sea (except in a cyclone or severe tropical storm) does not have any bearing on survivability in the Southern Ocean. They are simply different worlds. I would have no worries about taking a Gemini across the Coral sea outside of cyclone season, and really no worries about coastal sailing on the south side of Tassie in stable weather (Southern Ocean fringe). But there is no way that I would attempt a long Southern ocean passage in one. YMMV as always.


Cheers,

Jim

I think you had better get some better Charts, Jim,

That Chasm under the sea is even on Google Earth.

Its certainly on my GPS, My paper Charts, and the Maps the bloke downloaded for me into my laptop in Efate,
I said the force 6 winds were on the same day, from a passing ship, I considered it to be a nice day when that ship went past, and had force 6 winds. For me it was just a bit blowy, Not a concern for me in the slightest,

later on in the day it got a lot worse, The wind still didnt bother me, The waves did, Some of them were actual monsters, Very strange waves, only 200 metres long and they came out of the ocean and dropped back in, well above what all the other waves were doing,

You can see where I went from the piccy I added,

As for heights and lenghts my Boy, I have been in steel all my life, 49 years to be precise, I can tell if the steel is under or over lenght before it comes off the truck,
steel comes in 6 8 10 12 13 15 metre lenghts, I definately know what 10 metres is,

I live at the entrance to the Southern Ocean, Bass Straight and the Tasman sea, It can be very rough,

They had 90 foot waves when the Sydney-Hobart Race boats sank,

And only a total idiot would go out there in bad weather,

The Princess of Tasmania had windows smashed on the 10 floor above sea level, That was in Bass Straight,

The real bad part of the Southern ocean is under Tasmania, Not recomended for man or boy, Even ships have a hard time going down there,

[Zindab]

I think you have all covered all the angles, end result if the bulkheads holding the cross beams are not up to standard the hull will fail,and if the cross beam fails the mast will fall,not like a mono a cat can not heal and spill the wind so there is a lot of stress on structural parts mentioned and the method of sailing a cat to a mono is considerably different.

[ArtM]

Great discussion and good technical points on all sides. Thanks everyone.

I think my takeaway on this is that some early design catamarans have design flaws that could result in a structural failure under some conditions (grounding or extreme sea conditions).

Modern designs by reputable manufacturers that are not wood, however, would not be expected to experience a structural collapse while at sea, and structural strength should not be considered a safety issue on these boats.

[maxingout]

I don't know how important hull strength is on a multihull, but I know how important it is for my peace of mind.

Our Privilege 39 is very robust and I never felt that it was under built for the conditions encountered during our circumnavigation. There is a fair amount of wood on the interior, and I could always hear the noise of the wood creaking when the boat was sailing in heavy seas. Even on a stiff hull like the Privilege 39, the hull does work and flex causing those wooden boat noises.

I never felt like the boat had a problem in winds to fifty knots with the accompanying seas. The hull was up to the job.

Most of the hull strength issues that I saw in multihulls during the circumnavigation related to bridge deck slamming in heavy seas causing structural damage to the bridge deck of several different cats that I saw in New Zealand the two times I sailed to NZ.

One of the reasons I like smaller cats like the Privilege 39 is the relatively small size and robust construction making me feel confident in heavier seas. Our smaller size presented a smaller cross sectional area to the seas, and I believe it gave us a larger margin of security when things got rough.

[geoleo]

Originally Posted by ArtM

Great discussion and good technical points on all sides. Thanks everyone.

I think my takeaway on this is that some early design catamarans have design flaws that could result in a structural failure under some conditions (grounding or extreme sea conditions).

Modern designs by reputable manufacturers that are not wood, however, would not be expected to experience a structural collapse while at sea, and structural strength should not be considered a safety issue on these boats.

Guess you missed the OP who said that Outremers cross beams and their connection to the hulls are wood--plus there are many custom wood composite designs that are very fast and accomplished Catamarans ---Such as those designed by Chris White and Kurt Hughes--seems that large fast Cats do use wood structurally and safely

[ArtM]

Originally Posted by georgetheleo

Guess you missed the OP who said that Outremers cross beams and their connection to the hulls are wood--plus there are many custom wood composite designs that are very fast and accomplished Catamarans ---Such as those designed by Chris White and Kurt Hughes--seems that large fast Cats do use wood structurally and safely

Yeah-- I was trying to politely avoid saying "homebuilt plywood boats"

[smj]

Originally Posted by ArtM

Yeah-- I was trying to politely avoid saying "homebuilt plywood boats"

There are also quite a few homebuilt plywood boats that are beautifully built. Maybe hard to find but if you do they can be a great deal for a well built strong boat.

[Factor]

Originally Posted by smj

There are also quite a few homebuilt plywood boats that are beautifully built. Maybe hard to find but if you do they can be a great deal for a well built strong boat.

+1 - there is a Shawn Arber 40 footer here that is I think one of the nicer owner built boats I have seen - its ply and its a very nice thing.

[44'cruisingcat]

Originally Posted by ArtM

Yeah-- I was trying to politely avoid saying "homebuilt plywood boats"

I'd choose a boat built by it's owner, for his family to use, over a production boat built down to a price, with profit being the only reason for it's construction.

Sure the production boat will likely be shinier inside, but the owner built boat is less likely to be structurally compromised in the interests of cost cutting.

[ArtM]

Originally Posted by ArtM

Yeah-- I was trying to politely avoid saying "homebuilt plywood boats"

Next time I'll simply not say it!

I know that some homebuilt boats are good boats, and many will be better than a price-pointed production boat. The point of the OP was whether a multihull cruiser should be concerned about hull strength, and the answer was that for modern, factory made plastic boats, the answer is "no", but for all other boats the answer is "maybe".

[44'cruisingcat]

Originally Posted by ArtM

Next time I'll simply not say it!

I know that some homebuilt boats are good boats, and many will be better than a price-pointed production boat. The point of the OP was whether a multihull cruiser should be concerned about hull strength, and the answer was that for modern, factory made plastic boats, the answer is "no", but for all other boats the answer is "maybe".

I'm presently moored next to a modern, factory made plastic boat, (one of your WTB's as it happens) which has had the hull-deck join seperate aft of the chainplates. This happened in heavy, but not storm conditions.

This caused some flooding of the hull, and resulted in them having to change course (putting the damaged hull to the lee side) and seek shelter to save their boat.