Negatives of full Fibreglass hulls/decks?

[lo2jones]

It’s difficult to understand why someone would think of building a solid fibrglss yacht now days. I owned a Columbia 29 ‘65 for 7 years: easy maintenance, easy repairs…All the advantages and new building techniques of a cored hull and deck.

[capn_billl]

In every okd boat I've seen the wood was the weakest link.

It's all well, and good to discuss weight stiffness ratios in a brand new boat, but look at one 30 years old you get a different story.

In every old boat, the wood rotted, (usually where it contacts the fiberglass), leaving a fiberglass boat with rotting holes.

In each of those to repair them, i replaced the wood either with plastic, or premade fiberglass sheets cut to fit.

And yes, it's shocking how much more the fiberglass weighs compared to plywood. But at least it don't rot.

[Hillbillybuddha]

I've been kind of dealing with an early cored deck for the last few weeks. I have a 1964 Pearson Rhodes 41. I just replaced the old manual windlass with a Lewmar V4 Windlass. And I've pulled some deck hardware that I just wanted gone, and I've added a few pieces of hardware. My deck has no soft spots. None. When pulling old hardware and adding new hardware, it quickly became evident that, at one time, I had wood coring that has all long deteriorated. The thinnest area of the deck has been about 3/8 inch of fiberglass, about an inch and a half of space where the old wood use to be and about a quarter inch of bottom fiberglass. I can't even imagine the project it would become, trying to replace all the deteriorated wood, but I also can't think of a good reason to do so. I've added a bigger backing plate to the windlass but, honestly, I doubt it needs it.

[Rucksta]

Originally Posted by Benz

Thanks for taking the time to post this.
If you have some spare ammo and materials anytime, could you do a solid panel: 1/4" S-glass woven 10oz cloth; 1/2" Kevlar biax; 1/2" 1708 hand-laid in vinylester? That's the schedule I'm after for the hull of my dream expedition schooner.

I'll bring a case of beer and ear protection.

Sorry Ben.

Under current Australian gun laws I can own a nerf gun.

I'm interested in your dream layup schedule.

Have you considered interleaving the S-glass and Kevlar?

It will produce better interlayer adhesion creating a stiffer structure more resistant to penetration and avoid some of the wet out problems associated with Kevlar.
This technique also allows you end work for the day with a layer of glass which can be sanded unlike the Kevlar which will pill and require shaving before proceeding.

Interleaving also gives the opportunity to taper the layup and / or encapsulate some unidirectional at key locations without creating stress risers.

Compared with the S-glass and Kevlar the 1708 is adding bulk rather than strength. Consider using 2 layers on the outside to 1 layer on the inside to produce thickness and protect your Kevlar and E-glass core.

[David Johnson]

We own and mostly liveaboard a Nauticat 44 in Sitka, Alaska. We are at 51 degrees north latitude. Our boat has a solid fiberglass hull and deck and cabintop. We have had many issues with our new-to-us but old (1986) boat, but none with the solid fiberglass construction.

[WaterLilyCat]

I have a 40ft catamaran built in 1980. It's solid fibreglass including decks and cabin roof. The cockpit roof is a Balsa laminate. I think solid fibreglass is great on old boats because it's very low maintenance. Very heavy but I am retired and not in a hurry to get anywhere. And guess what, the only structural problem I have had is the cockpit roof. Got a bit of water leakage and the Balsa just turns to mush.
When I do work to antifouling at the Boat yard, there are always lots of boats with structural problems and they are always laminated construction.
In my opinion, my number one criteria for buying an old boat is full fibreglass construction.

[Lucky Luke 1]

Originally Posted by Nicholson58

All glass boats are desired by many. Infinitely repairable. The only negative is they are not suitable foe high latitudes. As long as you stay in swimsuit territory, who cares.

What happens with them in high latitudes? Im at -41

[Mike Burch]

For those not familiar with the reasoning behind cores—the bending strength of a panel varies as (among other things) the square of its thickness.

Let's say a panel made of solid fibreglass 10mm thick has certain bending resistance. If we make a panel consisting of the same amount of fibreglass but in two layers each 5mm thick bonded to a 20mm thick core of negligible weight, we get a panel three times as thick with a bending resistance nine times that of the fibreglass alone with little weight penalty. So if bending resistance is the only criterion, then cores are A Good Thing.

But hulls and decks are not subjected solely to bending. Obviously there are many other factors to take into consideration, and they have been discussed in previous posts.

My own experience of solid hull with end-grain balsa cored deck was almost entirely benign, apart from a touch of osmosis in the hull. The deck had been moulded with plywood replacing the balsa in the core in places where compressive loads were to be expected (winch sites, for example), and in places where the moulders had not expected such loading it was easy enough to drill up from below with a hole saw, removing the lower layer of glass and the balsa, to replace it with ply and more glass. (I did get a bit carried away when fitting the windlass—when I sawed out the hole for the chain I was slightly alarmed to find that the deck at that point was an inch and a half thick!)

As for lightning protection, I can't see a core making a blind bit of difference. The surge will find the most conductive way from the masthead to the sea, and in anything other than a metal boat that is surely unlikely to involve the hull? Anyway, your chances of being hit by lightning are a lot smaller than your chances of being hit by a malevolent underwater rock.

The heat insulation afforded by 20mm of core is too little to be a serious consideration.

Glass over ply is a very common way of building hard-chine boats here in New Zealand. Before the days of epoxy it was not always successful, as ordinary layup resin is not a particularly good glue, and the glass/ply bond doesn't take much of a hiding before it fails. Epoxy is vastly better in all respects except cost. One should also distinguish between boats using ply as a core (i.e., glassed inside and out, the glass supplying the strength) and boats where the hull strength comes from the ply, and the glass is only a relatively thin layer on the outside, to resist abrasion, penetration and the sea.

[Benz]

Originally Posted by Rucksta

Sorry Ben.

Under current Australian gun laws I can own a nerf gun.

I'm interested in your dream layup schedule.

Have you considered interleaving the S-glass and Kevlar?

It will produce better interlayer adhesion creating a stiffer structure more resistant to penetration and avoid some of the wet out problems associated with Kevlar.
This technique also allows you end work for the day with a layer of glass which can be sanded unlike the Kevlar which will pill and require shaving before proceeding.

Interleaving also gives the opportunity to taper the layup and / or encapsulate some unidirectional at key locations without creating stress risers.

Compared with the S-glass and Kevlar the 1708 is adding bulk rather than strength. Consider using 2 layers on the outside to 1 layer on the inside to produce thickness and protect your Kevlar and E-glass core.

I hadn't thought about interleaving each layer--only having glass over the kevlar on the last layer of that particular session, so it could be prepped for the next series of lamination. The reason to bulk up with 1708 (which is plenty strong on it's own for what it is), is simply to keep the cost mostly reasonable. In other words, I want a glass boat with kevlar reinforcement, not a kevlar boat with glass bulk. Most of the structure would be regular glass laminate (mat, roving, 1708, with unis in the composite chainplate locations), with the kevlar only from deck-level down, tapered toward the upper end, and with none at all in the bulwarks, where all the fittings go.
Of course, if I win the lottery and can afford to have a hull infused, my whole laminate schedule will change.
Off to buy a ticket!

[Nicholson58]

Originally Posted by Lucky Luke 1

What happens with them in high latitudes? Im at -41

Plastic can become brittle at very low temperatures. Add the possibility of striking ice. Metal is the preferred hull.

[redneckrob]

Originally Posted by Nicholson58

Plastic can become brittle at very low temperatures. Add the possibility of striking ice. Metal is the preferred hull.

What temps are you cruising in where fiberglass becomes brittle? There are plenty of fiberglass commercial fishing boats operating pretty much everywhere without suffering from this alleged "brittleness", heck the body of most snowmobiles are made of fiberglass and I've seen 20 year old versions of those in Barrow Alaska with no ill effects.

[Nicholson58]

Originally Posted by Lucky Luke 1

What happens with them in high latitudes? Im at -41

Originally Posted by redneckrob

What temps are you cruising in where fiberglass becomes brittle? There are plenty of fiberglass commercial fishing boats operating pretty much everywhere without suffering from this alleged "brittleness", heck the body of most snowmobiles are made of fiberglass and I've seen 20 year old versions of those in Barrow Alaska with no ill effects.

Please consider what you wand around you if you are trapped in ice. In addition to metal, the shape is important so how might pop up rather than get crushed. By north latitudes I don’t mean 40. Think arctic.

[Jim Cate]

Originally Posted by Lucky Luke 1

What happens with them in high latitudes? Im at -41

Luke, while I find winters here in southern Tassie unpleasant, I've seen zero floating ice and no fibreglass boats breaking up. Don't let the hyperbole spewing scare mongers get to you!

Jim

[Lucky Luke 1]

Originally Posted by Jim Cate

Luke, while I find winters here in southern Tassie unpleasant, I've seen zero floating ice and no fibreglass boats breaking up. Don't let the hyperbole spewing scare mongers get to you!

Jim

I wasn't worried Jim, seems it's only a high Latitude thing and not a low one. Must be a difference in cold..
Maybe not your cup of tea but this has me interested- Timber though. https://www.gumtree.com.au/s-ad/port...36-/1280541144. Fairly new build.



On a more serious note it seems these older full fibreglass jobs have quite a few advantages over other hull types for cruising. Especially if your not a wielder or a carpenter and would rather have a drink than worry about rotting cores.

[jeepers]

[QUOTE=Cheechako;3503820]

Originally Posted by goboatingnow

I think a case could be made for solid decks (they were made that way early in FG contruction) but were sometimes a bit flexy though. No strength issues, just not a "feel" people liked. With the myriad of wet cored decks out there, what would be nice would be solid decks with a lattice structure to stiffen it say in 6" squares... so effectively small ribs in a squarish pattern for the large flat surfaces. Near other buildups like cabin trunk or toe rail it needs nothing.
Too expensive I guess. But I have often wondered "what am I getting when paying a premium for a Swan?" For the money, things like this should be offered!

Molds for fiberglass reproduction parts, frequently use "Eggcrate" lattice, grid support. Lattice of 6"# can't support the wetted fabric without drooping. Even as small as 3/4"# ie the size of fiberglass diffusers on fluorescent light fixtures, as a core, won't hold the fabric tight enough.
What we did have success with. Was 1/2" & 3/4" holes in perforated sheets of closed cell foam. This facilitated the remedy to the cause of core failure due to water intrusion as well as surface/material compression.
Drilling a small hole @ the location of a fastening or breach into the surface through the fiberglass layer covering the perforated core. Gave better access and easily facilitated the removal of more perf, foam core when necessary, for larger holes. (The best methods were a drill with Triangular metal stock in an "L" shape in the drill chuck. Also a soldering iron with an "L" shaped "tip" was highly effective.) Then very easily, mixed resin with beads/ strands or just mixed resin could fill the hole & voids by a "bakers, confectioners" piping type tool.
Upon curing, the final hole & fastener etc could be installed.
For installation of larger bases of fastening. At these locations. When laying up, the core would be grooved to connect many perforated core holes together. Holes drilled to introduce mixed resin. Holes drilled to create locations to introduce vacuum.