Vinyl Ester resin ok?

[wingtime]

Bob you hit the nail on the head with the word "laminating".  Poly is an excellent resin to use for new hull construction since all the bonds are primary bonds.  Each layer of lamination is applied on top of a wet or still curing layer of poly below it.  So the molecules of the poly resin are able to cross-link to each other curing into one solid part.   Like you said boats constructed of quality poly resins last years and years.  

Years later when you make a repair to the boat you are basically "gluing" on additional layers.  This is a secondary bond.  Secondary bonds are never as strong as a primary bond since the new layers of resin cannot interact with the old resin and bond at the molecular level.  In fact all repairs are secondary bonds since you are relying on the adhesion strength of the resin you choose.

[seabob4]

Bruce, I saw you posted just before me.  Regarding "secondary" bonding, that is done all the time at the OEM level.  Stringer alterations (notches for engine clearence, cutouts for hose routing, etc.), b/head tie-ins to hullsides and overheads, you would be surprised at the amount of additional laminating that is done once the initial layup has reached full cure.

Once again, the key to strength, adhesion, and durability is proper surface prep.  Cae in point, I had a 1984 Hydra-Sports WA here a few years ago.  I had to access the areas behind the helm and port side close-out b/heads (just like on your Explorer), there were structural b/heads glassed to both the upper portion of the wings, the hullsides, and the outboard stringers.  All secondary bonding.  And since I doubt VE was even invented in '84, let alone in use by a mid-tier builder like H-S, all done with polyester resin.

There wasn't one single thing amiss with those b/heads.  And I would imagine, due to the fact that they tied in 2 very large pieces of glass to one another, there was a significant amount of flex and stress placed on the b/heads and the bond joints.

I'm sure shear tests, torsional rigidity tests, and testing methods of that nature show VE and epoxy to be superior in strength and other physical properties.  But in real world applications, where the stresses applied to materials don't even come remotely close to the testing parameters, polyester resin, COMBINED WITH THE PROPER SURFACE PREP AND PROPER MATERIALS HANDLING AND PREPERATION, will perform more than adequately...

A little anecdote.  When I was at Lockheed-Martin, all of our lifting devices had to be certified annually.  I had a small boom crane over my work area, 1500 lbs. capacity.  The most I ever lifted with it was about 250 lbs.  The cert called for 2 1/2 times it's rated capacity...in other words, come cert time, the metrology guys would lift 3750 lbs with my little crane!!  The first time I saw them do it, I bet my eyes got as big as saucers, as the boom actually deflects about 3"...and this is an 8' boom, a 1/2" thick, 4" X 8" steel I-beam!!  No way in hell, in regular service, was that crane going to see anything close to the loads placed on it during cert...but that was the deal.

[seabob4]

Bruce, at a molecular level, no, there will be no interaction.  Definitely agree on that point.  But the strength of the bond, in relation to one surface to another?  Polyester works, provided it is applied correctly...

[RickK]

There are a bazillion articles to read about "bonding strength of epoxy vs vinylelster vs polyester" on the web.
  Here is a link to one:
http://www.amtcomposites.co.za/sites/de ... yester.pdf

I was a diehard poly guy and wanted to do my rebuild in 100% poly - all for the rationale you hear above.  After talking to some people, researching and being run off some epoxy focused rebuild sites I decided that if I was going to be doing structural stuff, I mean stuff that would become part of the "whole" like the stringers becoming part of the hull, the bulkheads becoming part of the stringers and the hull, like the sole becoming part of the stringers, bulkheads and hull - all of which would become a whole, then I was going to spend the extra $$ and go epoxy.
Anything that is not going to be structural I will use poly. Gelcoat is poly.
My $0.02 and I'm living it right now. I know my hull is strong and stout and it's not because it looks pretty or has decent craftsmanship - at the point I am at in the rebuild it is because of the epoxy. I have nothing to worry about on the rebuild up to now.

[JTown Aquasport]

If do not use all of the vinyl ester within six months it goes bad good for new parts that were gel coated but for a secondary bond epoxy is your best bet.