Fibreglass vs Aluminium Impact Strength

[goboatingnow]

Ive hit a few things in the night on various atlantic trips, the sound inside a GRP hull makes you feel the front has fallen off the boat, on inspection notrhing but a mark. Maybe its bits of wood or something, other then that Ive only ever once seen a submerged container.

did nearly get run down by a submarine though , its the funniest thing to see a rapid yellow light flashing and rising, the brain doesn't easily compute that,!!.

Dave

[noelex 77]

Originally Posted by goboatingnow

Mr B, Im not arguing that in a ultimate test metal is a very durable material indeed, My comments relate to small leisure made out of it. ( which I am very well familar with), High quality cosmetic standard repair of metal vessels demands great skill, as you obviously have. the same is not true of GRP ( to teh same extent). This is not to mention the inevitable repaint , which is equally trickey if its high quality LPU finish. Equally many classification societies require both side welding as well. And Ive always seen teh interior being removed as well as the insulation ( often PU foam, which makes areal mess).

Aliuminium is not difficult to repair, although you do need a top class welder. I am not sure what your concern with paint is. Most aluminium cruising boats are not painted over most of their structure. Aluminium does not require paint (or gel coat) to protect the structure from UV, corrosion or rot like other boatbuilding materials.
If the boat is painted touch ups and matching is easier than matching gelcoat. Cars paint finishes are repaired everyday.The only exception is Awlgip (and similar) paint finishes a which can be very difficult, but that's why almost no cruising boats use them.
The sprayed foam insulation takes about about 10mins to remove for a large repair.
One big advantage is following the repair structure is returned back to the same condition that it was built. With fiberglas the repaired area will have a different thickness, probably a different resin and layup. This means the repair will be heavier and more critically flex in a different way to the unrepaired portions of the hull. Fiberglass cored structures have the added and often serious problem of moisture penetration between the cores.

[minaret]

Originally Posted by noelex 77

Aliuminium is not difficult to repair, although you do need a top class welder. I am not sure what your concern with paint is. Most aluminium cruising boats are not painted over most of their structure. Aluminium does not require paint (or gel coat) to protect the structure from UV, corrosion or rot like other boatbuilding materials.
If the boat is painted touch ups and matching is easier than matching gelcoat. Cars paint finishes are repaired everyday.The only exception is Awlgip (and similar) paint finishes a which can be very difficult, but that's why almost no cruising boats use them.
The sprayed foam insulation takes about about 10mins to remove for a large repair.
One big advantage is following the repair structure is returned back to the same condition that it was built. With fiberglas the repaired area will have a different thickness, probably a different resin and layup. This means the repair will be heavier and more critically flex in a different way to the unrepaired portions of the hull. Fiberglass cored structures have the added and often serious problem of moisture penetration between the cores.

In my experience about 5% of aluminum boats are left bare. People like their boats to look nice. And as a pro painter, nothing is as easy to match or blend as gel. You can blend LPU, but it voids the warranty. And who paints a real cruising boat in anything but LPU? Every case I've ever seen we did a full repaint to give the owner a yacht finish. A big part of the art of pro glass repair is avoiding the problems you mentioned, those are very basic glass repair issues. I always use the same resin and laminate schedule as original, and match lams in the layup for fiber continuity. I have never had a repair fail. I would be much more concerned about the unknowns of weld quality than a laminate bond. Most quality boats are not cored below the waterline, saturation should be a non issue when considering collision damage, though I have seen it plenty in powerboats. Once you have removed foam and cabinetry you have to reinstall both as well. This will take much more than 10 minutes. And still no reply to the question of failure modes, which is what the video in question is all about, not relative ultimate impact strength.

[noelex 77]

Originally Posted by minaret

In my experience about 5% of aluminum boats are left bare.

Have a look at the Ovni range. The largest maker of production aluminium cruising yachts.

Originally Posted by minaret

You can blend LPU, but it voids the warranty. Every case I've ever seen we did a full repaint to give the owner a yacht finish.

Which is why very few aluminium cruising yachts use this paint type. There are plenty of alternatives.

[atoll]

Originally Posted by silverp40

I think that a quick informal survey amongst readers of this post would be interesting for two reasons:

1. Determine in a real life fashion how metal, fiberglass and maybe wood hulls react when impacted by various objects while underway. I am sure a lot of the posters have hit various bits of flotsam while making offshore/inshore trips.

2. Get an idea of the amount of collisions offshore that exist in one's sailing experience in this small cross section of sailors many of whom I think have extensive miles under their belts/keels.

Here is one of ours as a first:

A few years ago, at night, offshore, in heavy air, we hit a semi-submerged object hard with our centerboard. It was hard enough to think that we lost the board for a moment. We were also sailing at hull speed. Upon getting inside an inlet later and examining the board, a small, 1/4" or so dent was visible at the leading edge of the board (which is rounded, not sharp). No other damage to board or mechanism. The board may have swung back a bit but is still weighs 250lbs or so so it had a lot of inertia.
We thought it could have been a log or maybe a turtle.

sailing up the great barrier reef nr cape york we sailed past a steel yacht up on one of the many reefs in the area,who we had met before in bundaberg.

at the time there were fairly strong trade winds and we could see waves breaking on the yacht,so you could imagine our surprise when he turned up in darwin a few weeks later.

i had a chat with the guys when they dried out against the pilings to touch up the anti fouling which was mainly undamaged apart from some shallow dents and grazing just below the waterline and on the bottom of the keel.

apparently it had taken 3 days to get washed over the reef and they needed to replace impellors for the engine and generator,before they were able to carry on the 1000 miles to darwin.

another friend in a plastic oceanis 49 hit the reef at 5 knots just outside royal langkawi yacht club.
this delaminated most of the frames under the saloon floor from the hull,neccescatating a haul out and epoxy rebonding all the under floor frames,and removal of furniture and cabin sole,took a week and $7000 plus hotel...................

[silverp40]

Originally Posted by noelex 77

Fiberglass cored structures have the added and often serious problem of moisture penetration between the cores.

Not really. A cored lay-up that is done properly does not suffer from core delams or moisture ingress. It is up to the quality of the builder and decent maintenance.

As an example, out of 71 Pearsons 40 hulls that were built and cored to below the waterline, NONE have had any issues with core delamination above OR below the waterline and a lott have been "raced hard and put away wet". Same with their decks. After 30 plus years.

[minaret]

Originally Posted by atoll

sailing up the great barrier reef nr cape york we sailed past a steel yacht up on one of the many reefs in the area,who we had met before in bundaberg.

at the time there were fairly strong trade winds and we could see waves breaking on the yacht,so you could imagine our surprise when he turned up in darwin a few weeks later.

i had a chat with the guys when they dried out against the pilings to touch up the anti fouling which was mainly undamaged apart from some shallow dents and grazing just below the waterline and on the bottom of the keel.

apparently it had taken 3 days to get washed over the reef and they needed to replace impellors for the engine and generator,before they were able to carry on the 1000 miles to darwin.

another friend in a plastic oceanis 49 hit the reef at 5 knots just outside royal langkawi yacht club.
this delaminated most of the frames under the saloon floor from the hull,neccescatating a haul out and epoxy rebonding all the under floor frames,and removal of furniture and cabin sole,took a week and $7000 plus hotel...................

Another Beneteau....

[atoll]

Originally Posted by minaret

Another Beneteau....

i think all bolt on fin keel fiberglass boats suffer from this problem,not just bennys to a greater or lesser extent

[atoll]

and fiberglass skegs!

http://www.cruisersforum.com/forums/...nas-82072.html

[minaret]

Originally Posted by atoll

i think all bolt on fin keel fiberglass boats suffer from this problem,not just bennys to a greater or lesser extent

Not so. Beneteau just bonds in a hull liner and other structural members with Plexus. No tabbing. Of course they delaminted in an impact, and of course a lot of trouble had to be gone to to access the area. It's a function of their poor design.

[Panope]

Here is a very unscientific test.

Steve

[DeepFrz]

Steve, wonderful video. Thanks for that. That was 3/8". What did that panel weigh, do you know?

[silverp40]

Quote:

sailing up the great barrier reef nr cape york we sailed past a steel yacht up on one of the many reefs in the area,who we had met before in bundaberg.

at the time there were fairly strong trade winds and we could see waves breaking on the yacht,so you could imagine our surprise when he turned up in darwin a few weeks later.


Some steel boats do not make it like your friends....This one was not so lucky

[Panope]

Originally Posted by DeepFrz

Steve, wonderful video. Thanks for that. That was 3/8". What did that panel weigh, do you know?

The panel thickness is 3/16" 50xx series aluminum. My boat is plated with that stuff almost everywhere - hull, decks, house.

I did not weigh the panel.

Steve

[atoll]

Originally Posted by silverp40

Quote:

sailing up the great barrier reef nr cape york we sailed past a steel yacht up on one of the many reefs in the area,who we had met before in bundaberg.

at the time there were fairly strong trade winds and we could see waves breaking on the yacht,so you could imagine our surprise when he turned up in darwin a few weeks later.


Some steel boats do not make it like your friends....This one was not so lucky

all i see there is a steel boat with the crew on it waiting for the tide or a tow off,,,,,,alive! and not in the life raft,as would have been the case with a glass boat.......