Ortho vs. Vinylester

[We're Here]

I'm in the spec'g stage of an under 30' lobsterboat build. The builder estimates that he'll use 65-gallons of resin in the hull layup. He recommends a "barrier coat" of vinylester but I'm wondering if the superior strength of vinylester (in comparison to conventional ortho layup resin) warrants having the entire hull layup done in vinylester?

[gonzo]

Unless you re-engineer the laminate for a resin with better elongation and adhesion properties, it is a waste of money.

[Herman]

wtf is ortho resin doing in a boat? OK, it is cheap, but it is prone to blistering and water ingress. I would either specify a DCPD or a ISO-NPG, unless cost is the driving factor. But most DCPD is same price or even lower than ortho now anyhow. Just mind the secondary bonding, although that is seldomly a problem with DCPD (or better: DCPD blends) anymore.

I would definately invite a supplier over to tell you more about the different resins, or at least read some spec sheets.

[daiquiri]

Originally Posted by Herman

wtf is ortho resin doing in a boat? OK, it is cheap, but it is prone to blistering and water ingress.

I agree with this observation, but there are brands approved by Lloyd's for shipbuilding use (example: http://www.cfsnet.co.uk/acatalog/Llo..._Nors_6343.pdf) hence (I guess) the designer's cost-oriented choice and the prescription of vinylester as just a moisture barrier.
Cheers

[Herman]

Lloyds has little to do with what is best or at least in the direction of what is optimal. There are better performing resins than ortho ones on the list approved by Lloyds.

[Ilan Voyager]

I do agree with Herman: Lloyds is not a good guideline for composite boats. And for polyester and yachts Lloyds is obsolete.
Herman is right ortho has nothing to do on a boat. DCPD is a good choice and a lot of brands have a good balance price/strength/"workability"/durability.
For a small lobster boat vinylester is overkill and does not justify its price. 65 gallons is just over a barrel, what's the size of the boat? 65 gallons is very grossly 255 kg of resin, a very rough calculation gives a hull around 400 kg for a classic hand layed mat/roving polyester.