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Old 14-05-2007, 04:41   #1
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Post Fiberglass Over Wood Hulls?

Interesting that Brent recently spoke about his experience with fiberglass over plywood.

I have recently seen some fishing vessels that are constructed as fiberglass over wood.

Does anyone have any opinions, insight, advantages/disadvantages to this method of construction?
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Old 14-05-2007, 04:52   #2
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They tend to be ugly and boxy, look at these two abominations, designed and built by Sam Devlin.



Here's another one built in 1984, lived all its life in Florida, seems to be holding up ok. Built and designed by Reuel Parker.

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Old 16-05-2007, 22:49   #3
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There are a lot of boats built this way. The problems are that wood and fibreglass have different expansion rates, so eventually they separate in some areas. Water gets between the two layers. The wood rots, the fibreglass flakes away. (I am referring to boats that are built in wood and then covered with a layer of fibreglass and then wetted out with resin).

Epoxy works better than polyester resins, but it still works loose eventually.

If you spend a LOT of time and effort on maintenance you will be able to forestall the inevitable.

If you like the look of wood, but want the ease of fibreglass, then the best thing to do is consider cold-moulding, or epoxy-saturated strip planking.

If you like sailing more than working on the boat, then stick with fibreglass.
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Old 16-05-2007, 23:30   #4
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Not all timber rot's, and if done corectly timber cored boat's last just fine.

Some boat design's can't be built from solid glass due to weight constraint's, so suitable cores must be used.

Ply boat's resin sealed with epoxy on the inside and glassed on the outside with epoxy , if done correctly also have a long life ahead of them, but it can be argued that the extra framing and labour put's the lighter strip plank boat in front marginaly.

But yes, a traditional planked boat glassed over wiil have issues down the track, especialy if polyester resin is used.

Dave
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Old 17-05-2007, 00:08   #5
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When you say wood construction I tend to think of the traditional plank on frame type. Not a good idea to use fiberglass over this. The other types, cold molded veneer, strip planking, plywood over frame, or plywood stitch and glue have been around for decades and have a proven track record. I believe the photos of the boats Efraim sent are all epoxy/glass over plywood. For multihulls these types of construction give you lighter weight than solid glass and probably less expensive and easier to build for the home builder than foam core. Plywood may get a bum rap these days because people think of the crap you get at Home Depot. A proper marine grade ply if you can get it is an excellent boatbuilding material.
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Old 17-05-2007, 00:48   #6
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Glass over ply is probably the most common method around, epecially in smaller boat hulls. But I have seen many boats of upto 50ft built this way and have no issues at all. Some of those hulls have been in the water for nearly 20yrs now. The next most common is glass over daigonal timbers. These are medium size hulls up to quite large vessels.
The traditional timber plank hull, usually found in say the older commercial fishing boats, were sealed by a caulking and the immersion in water made the planks swell and take up the gap so as water was sealed out. Of course, they need a lot of upkeep. So many hulls got faired and glassed over. The ones I have seen around have held up well, but they are big heavey lumps of hulls.
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Old 25-05-2007, 22:11   #7
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If you want to learn truths from myths about glass over wood get Allan Vaitses book "Covering Wooden Boats With Fiberglass". It's quite a good read and puts the lid on a lot of BS that is often posted on the subject. Nobody on the planet has more experience or knowlege about it than Vaitses. He spent decades doing it in his shop and took core samples on boats annually to see what did and what didn't work. One interesting myth he busted was that old rotten carvel planked boats covered with a thick layer of glass to restore them to sound condition did not turn into heavy slugs. They performed better after the glass job, not worse. The reason is wood dries out and that water weighs more than the weight of a very heavy structural glass skin. The skin thickness also increased displacement enough to require additional ballast because the boats floated higher on their WL. At the same time you get a dry wood in the hull which is stronger than wet wood. He mechanically fastens the glass to the hull to and by the way, uses polyester,etc.
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Old 25-05-2007, 22:29   #8
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Just incase my comment on the hull being
Quote:
big heavy lumps of hulls
is taken the wrong way, I mean by my comment that the hull itself being off very heavy timbers and frames make them big heavy hulls. Letting them dry does indeed make them very much lighter. As much as 13% of the weight of a timber hull is water.
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Old 26-05-2007, 07:10   #9
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Quote:
Originally Posted by ssullivan
Interesting that Brent recently spoke about his experience with fiberglass over plywood.

I have recently seen some fishing vessels that are constructed as fiberglass over wood.

Does anyone have any opinions, insight, advantages/disadvantages to this method of construction?
I recently seen a sailboat come through the yard that could literally be described as a "wooden sailboat skinned in fiberglass". It had framing and planking like a traditional wooden boat but skinned with glass out side the hull and atop the deck. Almost as if it was done as an afterthought. Owner said it was quite bulletproof, if not heavy. Certain bits of the boat looked odd, like the toerail, but not bad.
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Old 26-05-2007, 10:12   #10
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Thank you for the responses so far. It's a strange concept (taking a wooden hull that may or may not be falling apart and putting fiberglass over it to extend the life).

In some ways, I would imagine if it was done well, you would be able to have completely rotted timber inside and a safe hull of fiberglass surrounding it. I suppose that's what the people who have done it imagine too.
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Old 26-05-2007, 11:24   #11
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Aloha Sean,

"Thank you for the responses so far. It's a strange concept (taking a wooden hull that may or may not be falling apart and putting fiberglass over it to extend the life)."

Its not a strange concept at all. I've seen it done on several boats. Depending on the method and workmanship and materials used it can be a very good thing.

My
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Old 26-05-2007, 11:25   #12
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Aloha Sean,

"Thank you for the responses so far. It's a strange concept (taking a wooden hull that may or may not be falling apart and putting fiberglass over it to extend the life)."

Its not a strange concept at all. I've seen it done on several boats. Depending on the method and workmanship and materials used it can be a very good thing.

My old friend, Shep, did it to an Herreshoff S-Boat which was originally built
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Old 26-05-2007, 11:33   #13
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Aloha Sean,
I don't know why these messages are turning out this way but I'll continue until I complete the intended thread.

Shep's S Boat was originally built in 1939 with traditional wood construction at Pearl Harbor. He used polyester glass sheathing in the early 80s. It is still sailing today. His method used a bit more glass than necessary and it could have turned out lighter if he'd used less layers of glass and epoxy. Still sailed very well and he one many races over the years.

Kind Regards,

JohnL
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Old 26-05-2007, 14:01   #14
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And another very common sheathing method for old wooden hulls, was FC. Especially in old commercial hulls, it extended the life of the hull dramaticly. Not done today as epoxy/glass is easier and has taken over.
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