Importance of Hull Strength and Construction Quality

[colemj]

Originally Posted by SunKing

It's time for Gemini bashers to own up to their coments!!! I would like to know how you came to that conclusion. Have you ever heard of a Gemini coming apart? Are you aware Gemini hulls are built in a ONE piece construction, unlike most others which are built in three pieces? How often have you been on a Gemini? What gives you the expertise to decide a Gemini would fall apart?

Settle down Beavis. Take a deep breath and re-read my post. Then read my most recent post. Take another deep breath and try to realize that not everyone is against you...

Mark

[Mr B]

That part of the Southern Ocean is where I said I was, its the junction of the Southern, Bass Straight and The Tasman, it also where all the Sydney- Hobart yachts hit trouble, Its the top of Tasmania,
Its about 200 miles to the east from where I have my Gemini parked.

Its the bottom right hand corner of Australia, the roaring 50's and 60's is a lot further south than that, I dont think yachts even go that far south, Its too cold, even big ships have trouble down there, thats another 1000 miles further south from us,

Your quote was, A Gemini would probably fail in the Southern Ocean, 2nd post,

Yes, we are very sensitive to our Gemini's being bashed, we get it all the time, But no one ever states where, when or why they are so fragile, Never a peep of proof to substantiate their claims,

Holes in my boat dont make it structurally unsound, just holy in the bottom, It will sink and did, But the rest is solid, Its very unseaworthy as well, It cant keep the water out, Hahahahaha and I did step off the front of the boat onto the beach,

In 3000 NM of Ocean, not once did I feel unsafe in her, And I did have a few times when I thought I was gone, But that was due to sea conditions and height of waves over the transom, not the integrity of the boat, 10 metre waves hanging vertically over the Transom are some thing not all that many boats can handle, especially if they drop onto you, fortunately, my 34 foot little Gemini just popped out from under it,

I have no problems or worries about sailing my Gemini in the Southern Ocean Safely,

They have changed the rules for the Sydney Hobart race,
They are not allowed to cross that particular bit of ocean where the 3 oceans meet if the weather is very bad, 90 foot waves are very common there,

The Spirit of Tasmania does not run on bad days, Thats the two ferry ships between Tasmania and Melbourne, Daily, They cross Bass Straight only,

[minaret]

Originally Posted by Dulcesuenos

Many of the links min Provides are more out that builders can do sloppy shoddy work, not sure it really points whether or not aboard design is not seaworthy just sometimes builders screw up. I've seen almost new monos w "keels a flopping"

Exactly my point. Many builders do shoddy work at some point or another, it's quite common (some much more so than others). We do a great deal of warranty work on new boats in commission. The problem is that you can generally get away with some of that on a mono without it breaking, they are more forgiving. A cat is not at all forgiving of shoddy workmanship during construction. It better be right, or there will be severe problems. Often the design is pushing the envelope of what's possible with a given weight of laminate in the interest of weight savings already, it doesn't take much of a screw up to have serious repercussions. So cat builders need to be super conscientious and build very carefully. Unfortunately some of the bigger cat builders are the same people who provide the worst examples of quality control in construction in monos as well. Some very poor builders cranking out cats, and they don't seem to be making any added effort for cat construction. You'd think they would for the extra money.

[colemj]

I don't think you are even reading my posts. Again, I only picked as an example the smallest production catamaran that came to my mind. And the example was to make an extreme case that all catamarans can fail in conditions not expected by the designer, but that all production catamarans are perfectly safe in the use that everyone wants them for. I expounded on that to make it even more absurd by specifying very high latitudes, as well as specifically stating that I did not mean to pick on Gemini and that my example holds for all production catamarans. But you still feel slighted. You guys are really edgy - even for the multihull forum - should probably lay off the coffee a bit.

But I withdraw my example of the Gemini and replace it with the Manta. Will that make you all happy?

I think someone should start a thread just for Hunter and Gemini owners to complain about how nobody respects them. Call it the whine club.

Mark

[Cheechako]

I would say what's extremely important on a Cat is the bridgedeck assembly/attachment to the hulls. Big radii to distribute the stress etc. A well done composite seems perfect for a cat IF it can be done such that it wont delaminate, and wont invite water intrusion.... Big IF's....

[smj]

Originally Posted by colemj

I don't think you are even reading my posts. Again, I only picked as an example the smallest production catamaran that came to my mind. And the example was to make an extreme case that all catamarans can fail in conditions not expected by the designer, but that all production catamarans are perfectly safe in the use that everyone wants them for. I expounded on that to make it even more absurd by specifying very high latitudes, as well as specifically stating that I did not mean to pick on Gemini and that my example holds for all production catamarans. But you still feel slighted. You guys are really edgy - even for the multihull forum - should probably lay off the coffee a bit.

But I withdraw my example of the Gemini and replace it with the Manta. Will that make you all happy?

I think someone should start a thread just for Hunter and Gemini owners to complain about how nobody respects them. Call it the whine club.

Mark

I personally don't think your being hard on the Gemini. The Gemini is a great boat doing what it is intended to do which is coastal cruising. They weren't designed or built to be bluewater boats just ask Tony Smith. Yes Tony sailed one across the Atlantic later stating he wouldn't do it again. And yes there are quite a few that have done ocean passages as well as one that did a circumnavigation, doesn't mean it was built or designed for it. I commend colemj for his statement as I think it is realistic and it doesn't talk negatively about the Gemini and its designed uses.

[Jim Cate]

[QUOTE=Mr B;1062613]

In 3000 NM of Ocean, not once did I feel unsafe in her, And I did have a few times when I thought I was gone, But that was due to sea conditions and height of waves over the transom, not the integrity of the boat, 10 metre waves hanging vertically over the Transom are some thing not all that many boats can handle, especially if they drop onto you, fortunately, my 34 foot little Gemini just popped out from under it,

I have no problems or worries about sailing my Gemini in the Southern Ocean Safely,
/QUOTE]

Brian, I keep meaning to ask you: could you please post the date and approximate lat/lon where you encountered the vertical 10 meter waves between Fiji and Bundy? I'm interested because we make that passage fairly frequently and would hate to be in conditions like that.

Cheers,

Jim

[monte]

haha

[sy_gilana]

www.infoAndratx.es: Un catamarán colisiona contra unas rocas en el Port d'Andratx

[monte]

I was in Andratx a couple of days after that. Apparently it was blowing 40k and its mooring line broke. Ouch. Beautiful Port btw, had a ball there. Good place to pick up a mooring ball.

[Mr B]

[QUOTE=Jim Cate;1062847]

Originally Posted by Mr B

In 3000 NM of Ocean, not once did I feel unsafe in her, And I did have a few times when I thought I was gone, But that was due to sea conditions and height of waves over the transom, not the integrity of the boat, 10 metre waves hanging vertically over the Transom are some thing not all that many boats can handle, especially if they drop onto you, fortunately, my 34 foot little Gemini just popped out from under it,

I have no problems or worries about sailing my Gemini in the Southern Ocean Safely,
/QUOTE]

Brian, I keep meaning to ask you: could you please post the date and approximate lat/lon where you encountered the vertical 10 meter waves between Fiji and Bundy? I'm interested because we make that passage fairly frequently and would hate to be in conditions like that.

Cheers,

Jim

Coral sea, between S 22.58.71 E 155.16.86 and S22.38.06 and E 154.28.40

I passed a ship who said the wind was force 6 during the same day,

I had two wave directions, one north and one nrth, nrth west, the one going nrth came over the transom and filled the cockpit, The one going nrth nrth west was the one that stood up behind the boat, I had two of them that did that,

after the first one, I let out the Genoa a bit more, to get a bit more speed up,

It was the third in a series of four big rollers close together, I was at about 45 degrees sliding backwards over the 3rd wave, when the big one stood up behind me, two of them in about half an hour,

It wasnt a continous roller. it was just a big wave that stood up out of the ocean,
I find they are where the sea floor changes, they flick these huge waves up, only about 200 yards long, they come up and go down and dissapear.
They are a lot higher than the surrounding waves as well,
If either of those waves had dropped on me, I was gone, no doubt about it, It would have smashed the boat to pieces,
I am quite aware of the power of water,
But thats only my opinion,

My mast is 12 metres high, my top spreader is 10 metres, the wave was level with the top spreader when I was level, That gives me a 10 metre wave,

I was in it, and could do nothing about it, I do not want to be in waves like that ever again, I wont be, as I am not going out there again, I will wait for the nice conditions in future, as I cruise up the coast, Inside the reef,

It was a delivery run, I just wanted to get my boat and myself home, Some of the weather I encountered coming across, I will never see again, I will be sitting in a nice quite place till the bad weather passes,

[Jim Cate]

[QUOTE=Mr B;1063065]

Originally Posted by Jim Cate

Coral sea, between S 22.58.71 E 155.16.86 and S22.38.06 and E 154.28.40

I passed a ship who said the wind was force 6 during the same day,

I had two wave directions, one north and one nrth, nrth west, the one going nrth came over the transom and filled the cockpit, The one going nrth nrth west was the one that stood up behind the boat, I had two of them that did that,

after the first one, I let out the Genoa a bit more, to get a bit more speed up,

It was the third in a series of four big rollers close together, I was at about 45 degrees sliding backwards over the 3rd wave, when the big one stood up behind me, two of them in about half an hour,

It wasnt a continous roller. it was just a big wave that stood up out of the ocean,
I find they are where the sea floor changes, they flick these huge waves up, only about 200 yards long, they come up and go down and dissapear.
They are a lot higher than the surrounding waves as well,
If either of those waves had dropped on me, I was gone, no doubt about it, It would have smashed the boat to pieces,
I am quite aware of the power of water,
But thats only my opinion,

My mast is 12 metres high, my top spreader is 10 metres, the wave was level with the top spreader when I was level, That gives me a 10 metre wave,

I was in it, and could do nothing about it, I do not want to be in waves like that ever again, I wont be, as I am not going out there again, I will wait for the nice conditions in future, as I cruise up the coast, Inside the reef,

It was a delivery run, I just wanted to get my boat and myself home, Some of the weather I encountered coming across, I will never see again, I will be sitting in a nice quite place till the bad weather passes,

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.

Personally, I feel that the structural stresses developed by multihulls are both more severe and harder to quantitatively analyze than those on a conventional monohull (Volvo 70's do not meet that description!). So, yes, I firmly believe that the care in design and execution of a multi is very important. It's interesting to note that Minaret, who has no dog in the fight, and who professionally encounters the damages due to inadequate structures, seems to believe that there are issues to worry about here.

I think that we mostly agree that the majority of production cats (not that many production cruising tris to use as data) are quite adequately made for normal cruising. There may be the odd "monday morning" boat sneaking through QA, but really, the beaches are not littered with the bones of broken cats... at least here on the East coast of Oz where there are lots of cats and lots of beaches! But, when stressed beyond "normal cruising", they sometimes do fail, and these failures could likely be avoided by stronger structures.

Cheers,

Jim

[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.

Personally, I feel that the structural stresses developed by multihulls are both more severe and harder to quantitatively analyze than those on a conventional monohull (Volvo 70's do not meet that description!). So, yes, I firmly believe that the care in design and execution of a multi is very important. It's interesting to note that Minaret, who has no dog in the fight, and who professionally encounters the damages due to inadequate structures, seems to believe that there are issues to worry about here.

I think that we mostly agree that the majority of production cats (not that many production cruising tris to use as data) are quite adequately made for normal cruising. There may be the odd "monday morning" boat sneaking through QA, but really, the beaches are not littered with the bones of broken cats... at least here on the East coast of Oz where there are lots of cats and lots of beaches! But, when stressed beyond "normal cruising", they sometimes do fail, and these failures could likely be avoided by stronger structures.

Cheers,

Jim

Actually Jim,

The sea was dead flat the whole 21 days from Fiji to Australia,
It was a figment of my imagination, I bow to your extensive sailing experience,

[minaret]

[QUOTE=Mr B;1063124]

Originally Posted by Jim Cate

Actually Jim,

The sea was dead flat the whole 21 days from Fiji to Australia,
It was a figment of my imagination, I bow to your extensive sailing experience,

If I had a nickel for every time I've heard or read "the waves were the height of the spreaders"....
Various navies have done studies on this for centuries, it is a well known effect. Judging actual wave height, especially of larger waves from the deck of a boat, is something that comes only with long experience. It's the "Froude Effect".


Measuring Wave Height | Boating Magazine

[David_Old_Jersey]

Originally Posted by Jim Cate

I think that we mostly agree that the majority of production cats (not that many production cruising tris to use as data) are quite adequately made for normal cruising. There may be the odd "monday morning" boat sneaking through QA, but really, the beaches are not littered with the bones of broken cats... at least here on the East coast of Oz where there are lots of cats and lots of beaches! But, when stressed beyond "normal cruising", they sometimes do fail, and these failures could likely be avoided by stronger structures.

Cheers,

Jim

Given that everything has design limitations (Boats and whatever), and that these are usually intentional to gain benefit elsewhere then I don't think the "answer" is simply making something stronger (as likely that means compromises elsewhere) - it's more about understanding the limitations of what you have, accepting them and then using accordingly. and the good news is that if you have a well known design and build (of anything) rather than version #1 then likely can find out a bit more than simply what the brochure says or the dream would like. If one wants to.

And for the sake of clarity, I am sure that most multihulls are not only capable of fulfilling there designed purposes (which for all practical purposes likely cover 99% of what any sane person would want to do recreationally - even if for that figure they may sometimes need at least some wit onboard). but are likely also fun as well. Albeit from the sounds of it, if someone wanted to navigate the Northwest passage in winter they will probably need a G#mini .