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Old 05-12-2012, 23:18   #211
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Re: Fibreglass vs Aluminium Impact Strength

As far as plausible scenarios go:

If you visualise someone cutting your boat into peggy squares and attacking those squares individually with a pickaxe, they'll have a bit more trouble cutting an alu hull up, but from then on, it appears than aluminium might put up less of a fight than fibreglass. If you put yourself in their place, that is ...

Now THAT's what I call considerate.

Reverting for a moment to the topic under discussion:

One abrasion scenario for which metal boats are conventionally preferred is navigating (or long term mooring) in floating ice.

Fibreglass boats tend to develop a broad grin, in inverse proportion to their owners' ...
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Old 06-12-2012, 04:48   #212
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Is aluminum thought to cause Alzheimer's Disease? Just saying' : popcorn:
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Old 06-12-2012, 05:21   #213
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Re: Fibreglass vs Aluminium Impact Strength

I forget
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Old 06-12-2012, 05:23   #214
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Re: Fibreglass vs Aluminium Impact Strength

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Is aluminum thought to cause Alzheimer's Disease? Just saying' : popcorn:

I can't remember.

Steve
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Old 06-12-2012, 07:04   #215
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Re: Fibreglass vs Aluminium Impact Strength

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I can't remember.

Steve
What was the question?

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Old 06-12-2012, 12:41   #216
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Re: Fibreglass vs Aluminium Impact Strength

Clearly steel is just a recipe for a sunken boat...


Photos Reveal Damage to Corvus J Following Fatal North Sea Collision, Update With AIS Data | gCaptain - Maritime & Offshore News
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Old 06-12-2012, 12:42   #217
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Re: Fibreglass vs Aluminium Impact Strength


This is one that sank within 15 minutes
Car Carrier Sinks Near Rotterdam After Collision, Casualties Reported – UPDATE | gCaptain - Maritime & Offshore News
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Old 06-12-2012, 15:07   #218
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Re: Fibreglass vs Aluminium Impact Strength

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I guess this means I need to find a piece of steel to attack. And ferrocement, plywood, paper mache, stainless steel, balsa core, Kevlar, seal skin, bamboo, hypalon, titanium, carvel planking, copper nickle, polypropylene..............

Steve
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Old 06-12-2012, 17:33   #219
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Re: Fibreglass vs Aluminium Impact Strength

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I guess this means I need to find a piece of steel to attack. And ferrocement, plywood, paper mache, stainless steel, balsa core, Kevlar, seal skin, bamboo, hypalon, titanium, carvel planking, copper nickle, polypropylene..............

Steve


Just get a job in a boatyard. You'll end up working with most of those eventually.
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Old 09-12-2012, 22:37   #220
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Re: Fibreglass vs Aluminium Impact Strength

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G'Day all,

I'm curious about your laminate thickness numbers, Minaret. Looking back at the damaged Bene 47 whose picture I attached in post 89, the layup in the bow sections where the failure occurred was much less than the 3/4 inch you mention as typical at the sheer line. I wasn't able to measure it, and the ragged fracture may have been deceiving, but it appeared to be on the order of 1/4 inch in this highly stressed area... certainly less than 1/2 inch.

Would it be unreasonable to expect that this was common practice in the manufacture of modern production boats of the French design school?

Cheers,

Jim

Certainly scantlings will vary dramatically from builder to builder. And of course thickness is just one factor to consider, laminate schedule and resin ratio are just as important. But just for your edification I thought I'd post a little preview of the upcoming pics from my present refit, so you can see I'm not just pulling numbers out of thin air here. These are pics of my boat with the thru hulls removed, taken today. The thinnest area I could find was a pair of thru hulls on either side of the bow fairly close to the waterline. The side which has already been peeled was 15/16ths, the unpeeled side was 1". The thickest area which I have a thru hull in is still quite a ways from the turn of the bilge, I'd say about 4'. It reads right on 1 1/2" on the caliper. I wouldn't be surprised if it's 2" at the turn of the bilge.

Wasn't trying to ignore you Jim, just taking my time getting the photo evidence. The original thru hulls were all heavily glassed in and were a real bear to remove.
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Old 09-12-2012, 23:28   #221
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Re: Fibreglass vs Aluminium Impact Strength

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Originally Posted by minaret View Post
Certainly scantlings will vary dramatically from builder to builder. And of course thickness is just one factor to consider, laminate schedule and resin ratio are just as important. But just for your edification I thought I'd post a little preview of the upcoming pics from my present refit, so you can see I'm not just pulling numbers out of thin air here. These are pics of my boat with the thru hulls removed, taken today. The thinnest area I could find was a pair of thru hulls on either side of the bow fairly close to the waterline. The side which has already been peeled was 15/16ths, the unpeeled side was 1". The thickest area which I have a thru hull in is still quite a ways from the turn of the bilge, I'd say about 4'. It reads right on 1 1/2" on the caliper. I wouldn't be surprised if it's 2" at the turn of the bilge.

Wasn't trying to ignore you Jim, just taking my time getting the photo evidence. The original thru hulls were all heavily glassed in and were a real bear to remove.
Well, that is indeed thick fibreglass!! Just out of curiosity, can you tell what sort of glass was used? As in, CSM, rovings or whatever...?

But, what I was getting at was the difference between layups like yours and the current crop of (especially) French production boats. There is endless discussion about the strength of these boats, some saying that modern engineering trumps massiveness while others claim that thick is the essential thing. To me, the broken Beneteau bow was shockingly thin, and the damage showed that at least in this case the structure was not all that forgiving of misuse. I don't know the gory details of the collision (speed or angle of impact) but the results were pretty devastating.

Anyhow, thanks for the pix... I wouldn't be worrying about longevity of that hull!

Cheers,

Jim
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Old 10-12-2012, 00:58   #222
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Re: Fibreglass vs Aluminium Impact Strength

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Well, that is indeed thick fibreglass!! Just out of curiosity, can you tell what sort of glass was used? As in, CSM, rovings or whatever...?

Yes, it's easy to tell. This is a fairly typical layup for a boat in my size range with a solid hull. It's about a 1/4" of chop matt followed by alternating rovings and matt hand laminated. The glass stringers and frames are 3/4" thick as well.


But, what I was getting at was the difference between layups like yours and the current crop of (especially) French production boats. There is endless discussion about the strength of these boats, some saying that modern engineering trumps massiveness while others claim that thick is the essential thing. To me, the broken Beneteau bow was shockingly thin, and the damage showed that at least in this case the structure was not all that forgiving of misuse. I don't know the gory details of the collision (speed or angle of impact) but the results were pretty devastating.


I don't want to indulge in too much Beneteau bashing here. Suffice it to say that in the past I have not been impressed by their construction. Caveat emptor and all that.



Anyhow, thanks for the pix... I wouldn't be worrying about longevity of that hull!

Cheers,

Jim

Happy to share!
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Old 10-12-2012, 02:40   #223
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Re: Fibreglass vs Aluminium Impact Strength

I wish my Hulls were as thick as that, Minaret, I might not have got holed so easy,

My hulls are about 1/4 to 5/16 of an inch thick, as per Piccys,

The stiffeners that ran between the two bulkheads was 3 pieces of pine in each side totally glassed in, 3 X 2 inches thick,, not one piece, which it should have been for a stiffener,

But you cant see that when its buried beneath fibreglass, and I wasnt going to pull my thru hulls out just to measure the thickness of the material,

My thru hulls were straight under the boat, where it sat on the sand, recipe for disaster, They are being moved to safer places, like transom mounts, or in boxes on the side that can be closed off so they can be water tite if they fail,
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Old 10-12-2012, 03:56   #224
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Re: Fibreglass vs Aluminium Impact Strength

Mr B - Sorry, this is a thread about fibreglass. All I see there is resin...
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Old 10-12-2012, 08:47   #225
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Re: Fibreglass vs Aluminium Impact Strength

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Mr B - Sorry, this is a thread about fibreglass. All I see there is resin...
I wasn't gonna say it, but I sure wanted to. That is one rich layup!
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