Would you buy it? Fibreglass over Mahogany

[Wotname]

Originally Posted by clockwork orange

……..
The boat in question is simply a strip planked mahogany boat, edge glued with either epoxy which could be one of many brands that have been available in NZ for decades before West came along, or has been suggested, just as likely, resorcinol and almost certainly sheathed with glass in epoxy, again, with whatever brand the builder preffered. What has not been mentioned is the rest of the construction above the sheerline which is most likely all BS1088 marine ply, species unknown and not important as long as its BS1088, this is what most marine plywood manufacturers in the world except the US uses to make a consistent high quality panel (consequently we make the worst marine ply in the world here) Everything above the sheer will also be glassed with epoxy and painted with 2 part polyurethane. This type of construction is as watertight and low maintainance as any fiberglass boat……….

While BS1088 is a very good standard for marine ply, an even better one is AS/NZS 2272-2006. Of course, this mainly applies to Aussie readers but in case anyone else is interested, it exceeds BS1088 in several areas.

AFAIK, Austral Plywoods are the only manufacturer using AS/NZS 2272 -2006 and they exclusively use Hoop Pine for all veneers.

It is a beautiful ply to work with
See more here Austral Marine Plywood
& Australian Standard AS/NZS 2272:2006 Marine Plywood

[clockwork orange]

Originally Posted by Wotname

While BS1088 is a very good standard for marine ply, an even better one is AS/NZS 2272-2006. Of course, this mainly applies to Aussie readers but in case anyone else is interested, it exceeds BS1088 in several areas.

AFAIK, Austral Plywoods are the only manufacturer using AS/NZS 2272 -2006 and they exclusively use Hoop Pine for all veneers.

It is a beautiful ply to work with
See more here Austral Marine Plywood
& Australian Standard AS/NZS 2272:2006 Marine Plywood

Yes I have heard about this standard and will read up on it but unfortunately have never had the opportunity to lay hands on it. While I believe it may be better than BS1088 it really does not need to be, in over 40 years as a professional boatbuilder I have used hundreds of sheets of BS 1088 marine plywood manufactured in Holland, France, Israel, Australia, New Zealand, Phillipines and even China and consistency has been the common theme. Unfortunatly living in the US where really the only good species for making plywood is Douglas Fir and it is an excellent species, the mills don't build to BS1088, consequently in 35 years here I have yet to see anything I would put in a boat. What they call marine plywood can have repairs in the face veneers, voids, overlaps, not enough veneers and on and on,truly horrible stuff when compared to the consistency of BS1088,fortunately we can buy imported BS1088.
Is anyone in Aus making Kiri marine plywood yet? now that would be the holy grail. As I write this I have sitting next to me a sample piece of Chinese made 18mm plywood(not marine) with thin birch faces on a 7 ply core of kiri, it is marvelously lightweight and beautiful, it is a 79 in2 sample and weighs just 11.7oz which translates into 43lbs for a 4x8 sheet compared to 60lbs for okoume. Unfortunatly it failed the boil test as expected.

[boatman61]

Originally Posted by Wotname

Hmm… 1970… presumably the instructors were what, say 40+ (al least 30+) so they learned their stuff in 50's and 60's and were (again presumably) current with the trends on the early 70's. If so, what they told you was pretty accurate given the polyester resins of that time.

Since then, we have moved on and very few people who know anything about wood and resin, would consider using a basic polyester resin and wood in the same sentence

So yes, they were right, but they are not right, right now

An NZ professionally boat (as like the OP is looking at), will have used epoxy resin and either be sheathed with either fibreglass or dynel and I would be willing to bet it is more likely to be dynes.

Any rot found will not be from the construction method, rather from lack of maintenance / care.

Wot ^^^e^^^ Sed..

[Seymore]

Originally Posted by Wotname

Hmm… 1970… presumably the instructors were what, say 40+ (al least 30+) so they learned their stuff in 50's and 60's and were (again presumably) current with the trends on the early 70's. If so, what they told you was pretty accurate given the polyester resins of that time.

Since then, we have moved on and very few people who know anything about wood and resin, would consider using a basic polyester resin and wood in the same sentence

So yes, they were right, but they are not right, right now

We had epoxy resins then, and the instructors talked of them as required.

[Capt Phil]

When doing a total refurbishment/rebuild of a 1966 strip mahogany plank plank runabout for show and light lake use a few years ago, we used penetrating epoxy to stabilize and strengthen the hull and soaked the hull thoroughly before glossing. It added some weight, maybe 200 lbs but we fe let it was agood compromise for the added strength and integrity.
Capt Phil

[Cadence]

Originally Posted by Seymore

Around 1970 I enrolled in a fiberglass course in Sheridan College in Toronto, near the airport. The course was a beauty. They had molds for canoes, prams, dinghies and all. We chose the boat we wanted, split up into groups, sprayed the gelcoat into the molds, laid up the mat and roving and turned out boats for ourselves.

That was one of the things the instructors told us: Never cover a wooden boat with fiberglass, it'll let water (vapour) seep in and won't let it out. The boat will rot relatively quickly.

For experience, I have seen lots of wooden boats with hulls covered with fiberglass, all of them seedy with the fiberglass letting go. I can't remember any solid wooden boats with competent fiberglass hull covering. But this is lightweight experience. I don't much go near wooden boats with fiberglass covering.

Wooden boats (on their own, without fiberglass) are OK by me, although I've had one and wouldn't have another. You can replace any piece of wood in a wooden boat, so it can last forever if you keep up with it.

In 1970 he was probably speaking of polyester resin? West or System Three on marine ply. seems to be reliable providing the ply is scarfed right.

I would agree covering a planked hull? I guess as a last resort it can have some usefulness. I had made friends with a live aboard couple that had glassed the hull of their 1917 50' Trumpy. She was still afloat.

I question the glass letting water in. I can see it not letting condensation out and causing rot JMHO

[Seymore]

Originally Posted by Cadence

In 1970 he was probably speaking of polyester resin? West or System Three on marine ply. seems to be reliable providing the ply is scarfed right.

I would agree covering a planked hull? I guess as a last resort it can have some usefulness. I had made friends with a live aboard couple that had glassed the hull of their 1917 50' Trumpy. She was still afloat.

I question the glass letting water in. I can see it not letting condensation out and causing rot JMHO

He used the words that I said, and didn't differentiate between polyester and epoxy as I remember. He didn't elaborate.

You're right, the inference was that water vapour type intrusion would occur, not that torrents of water would pass through.

For the OP, a moisture meter run around the inside when the boat is hauled should show up problems of this nature.

[mitiempo]

Originally Posted by Seymore

He used the words that I said, and didn't differentiate between polyester and epoxy as I remember. He didn't elaborate.

You're right, the inference was that water vapour type intrusion would occur, not that torrents of water would pass through.

Epoxy is just about as waterproof as a coating can get. That is why polyester boats are barrier coated with epoxy. Nobody barrier coats with polyester.

If he didn't elaborate he was most likely referring to the common coating of the time - polyester.

[clockwork orange]

Originally Posted by Capt Phil

When doing a total refurbishment/rebuild of a 1966 strip mahogany plank plank runabout for show and light lake use a few years ago, we used penetrating epoxy to stabilize and strengthen the hull and soaked the hull thoroughly before glossing. It added some weight, maybe 200 lbs but we fe let it was agood compromise for the added strength and integrity.
Capt Phil

Wow, do you remember what brand that penetrating epoxy was? That's some impressive stuff, most people find that penetrating epoxy barely penetrates at all but for yours to consume about 20 gallons on a runabout it must be saturating the wood. I have always considered the so called penetrating epoxies which are highly loaded with solvents to be useful only as coating in non critical areas. I do like them for very select purposes and have used Epiglass evedure, tried the Smith stuff and currently have been using some made in Florida.

[minaret]

Originally Posted by mitiempo

Epoxy is just about as waterproof as a coating can get. That is why polyester boats are barrier coated with epoxy. Nobody barrier coats with polyester.

If he didn't elaborate he was most likely referring to the common coating of the time - polyester.

Vinylester is a superior water barrier to epoxy. Epoxy guys just spend way more on advertising.

[clockwork orange]

Originally Posted by minaret

Vinylester is a superior water barrier to epoxy. Epoxy guys just spend way more on advertising.

This is the main reason why so many newbies think that epoxy is the only option, massive advertising. I doubt that I have ever seen an ad for polyester or vinylester in a retail boating magazine. Epoxy is the way to go if bonding wood is involved, otherwise VE is a great product. VE is what underground fuel storage tanks are made with.

[Jim Cate]

Originally Posted by minaret

Vinylester is a superior water barrier to epoxy. Epoxy guys just spend way more on advertising.

That's pretty interesting, Minaret! If so, and I am not doubting your knowledge, is there a barrier coat product utilizing VE similar to the Interprotect epoxy that many (including you, IIRC) often recommend?

Jim

[minaret]

Originally Posted by Jim Cate

That's pretty interesting, Minaret! If so, and I am not doubting your knowledge, is there a barrier coat product utilizing VE similar to the Interprotect epoxy that many (including you, IIRC) often recommend?

Jim

There is indeed. Duratec. I do, however, prefer 2000e. Which is a modified epoxy.



http://duratec1.com/duratec/?p=710

[jsbraga]

How about Turkish built trawlers?