Funny fact about early Hunters

[DianaOfBurlington]

I just posted this to my boat's blog about an impressive discovery. This ought to end a few arguments-- at least I hope so-- and prove a point I have long tried to make: that sometimes 'good enough' really is good enough; though you have to let the yacht designers, yacht engineers and boatbuilders make that decision (and not the staff at Home Depot).

See if you can spot the funny fact in this photo--

Or read the full story--

http://dianaofburlington.blogspot.com/2012/03/argument-ender-and-joyous-surprise.html

 

[Jackdaw]

I'm sorry. What does this actually prove?

 

[Jim Legere]

I'm sorry. What does this actually prove?

To me, it proves that the appropriate material can be selected on sound engineering priciples rather than following some gospel that one reads on the internet, etc., etc.

Hunter, sometimes dissed on quality of build, elected NOT to use marine ply in this application (horrors!) and, lo and behold, the material is in perfect condition 35+ years hence.

For those in the know, often the only difference between 'Marine' and 'Exterior' grade plywood is the % of voids or spaces in the plys. The waterproof glue is exactly the same in both products. Exotic veneers are available on both types. So JC II's choice of ply for interior cabinetry works for me. I would probably buy Marine grade for building a hull however...

 

[Maine Sail]

I don't see what the big deal is? This is NOT uncommon practice for non-furniture or non-hull pieces.. Both marine and exterior grade SHOULD be using top grade WBP glue. Marine grade should always be a phenolic glue though some exterior rated ply does not use a phenolic..

With marine ply the cheapest grade is usually "B" grade which means that there will be no large voids on the facing or interior plies. Voids can cause poor adhesion and leave spaces for moisture ingress through channeling. Marine grade should have excellent adhesion throughout the lamination and may also often have more plies for an overall stiffer panel. "A" grade marine will have no voids but can get very expensive especially when exotic veneers are applied.

Marine grade can also be worked without exposing a voids on a cut and exposed edge because all voids should have been "plugged"..

Marine is normally used for structural and exotic laminates so voids do not absorb moisture which can show through the veneer.

For non furniture & critical structural stuff a good exterior grade ply is more than adequate provided it uses a #1 grade phenolic glue, which is exactly what a marine grade panel does......

I use a good exterior grade quite often for building battery boxes and such. Normally though I use an exterior "top grade" double sided MDO ply. MDO has a heat applied phenolic backing which gives both sides a nice paintable finish that both paint or epoxy stick well to. A good grade of MDO should be void free and costs a LOT less than marine ply but often has less "lamination's" making it less stiff.

Nothing wrong with a good exterior grade product for the right application. MANY builders use it..

 

[DianaOfBurlington]

I posted this because of some halfhearted flak I was getting for not using 'marine plywood' in this restoration. People had claimed that I was using wood of a lesser grade than what it had been built with. I had stated to these people (some here and some in my boat's neighborhood) that it doesn't matter, that most boatbuilders decide on a formula of cost savings versus quality and usually come down on the cost savings side. And, still, we are all still sailing about in 30-plus-year-old boats that were not built strictly to ideal standards.

I was impressed that though the mantra of 'marine plywood only for boats' was conspicuously disregarded in this case, the 'inferior' grade lasted 37 years in conditions that, at least in theory, should have rendered it goopy wet glop in about half that time. My own ethic of treating all raw wood with epoxy if it is either out of sight or bonded to the hull will probably ensure another 35-odd years or more of life for this boat (tremble at the thought!).

 

[DianaOfBurlington]

Maine Sail-- you mentioned MDO, which I have always believed was pretty good stuff. Apparently quality has slipped in the 15-year hiatus I took from the boatbuiliding industry. I managed to swipe a scrap from the Cherubini shop to use as a very low, short bulkhead on which the ladder was to stand and the cabin sole was to terminate and relied upon its being 'marine-grade' for a crucial structural application.

This was, in fact, the first piece of my restoration project to rot. Rainwater came in from the not-yet-repaired cockpit-seat scuppers and wet the back of it. Of course the whole thing had been well-treated in epoxy and bedded in liberal amounts of 5200 against the hull. None of this was done wrong. But the MDO became soft on the backside of it and before long I was able to dent the back (MDO side, not white laminate side) with finger pressure. The whole thing was rotten from the inside. I suspect that the epoxy did not want to penetrate the very solid 9-ply core and, though it appeared well painted-over in it, the water found some miniscule speck that was inadequately treated. This happened over just 3 or 4 years.

The fix was the same as what I do with cored decks, but messier and probably not as conclusive. I drilled into it-- right through the nice mahogany cap on top of it, which was bonded down by then-- and flooded it edgewise with epoxy from a syringe. It took several applications over the course of a few weeks till it stopped oozing out through the bottom of the piece. It really was that rotten to the core. Now it is essentially an MDO-epoxy sandwich.

I will not rely on such wood again. I have no doubt that I had I used a decent piece of mahogany plywood the epoxy would have taken to it much better and penetrated much more deeply. Also I was using MAS (from the shop) for that, which I do not like as much as WEST. MDO (which is 'marine grade' may be fine in a laminating (planar) application such as decking, but stood vertically in the bilge it shows itself to be just as susceptible or even more so than anything else.

I confess I used it only because I needed 3/4" and the scale of this boat precluded my buying even half a sheet of 3/4" for any other part of it.

 

[Maine Sail]

Maine Sail-- you mentioned MDO, which I have always believed was pretty good stuff. Apparently quality has slipped in the 15-year hiatus I took from the boatbuiliding industry. I managed to swipe a scrap from the Cherubini shop to use as a very low, short bulkhead on which the ladder was to stand and the cabin sole was to terminate and relied upon its being 'marine-grade' for a crucial structural application.

This was, in fact, the first piece of my restoration project to rot. Rainwater came in from the not-yet-repaired cockpit-seat scuppers and wet the back of it. Of course the whole thing had been well-treated in epoxy and bedded in liberal amounts of 5200 against the hull. None of this was done wrong. But the MDO became soft on the backside of it and before long I was able to dent the back (MDO side, not white laminate side) with finger pressure. The whole thing was rotten from the inside. I suspect that the epoxy did not want to penetrate the very solid 9-ply core and, though it appeared well painted-over in it, the water found some miniscule speck that was inadequately treated. This happened over just 3 or 4 years.

The fix was the same as what I do with cored decks, but messier and probably not as conclusive. I drilled into it-- right through the nice mahogany cap on top of it, which was bonded down by then-- and flooded it edgewise with epoxy from a syringe. It took several applications over the course of a few weeks till it stopped oozing out through the bottom of the piece. It really was that rotten to the core. Now it is essentially an MDO-epoxy sandwich.

I will not rely on such wood again. I have no doubt that I had I used a decent piece of mahogany plywood the epoxy would have taken to it much better and penetrated much more deeply. Also I was using MAS (from the shop) for that, which I do not like as much as WEST. MDO (which is 'marine grade' may be fine in a laminating (planar) application such as decking, but stood vertically in the bilge it shows itself to be just as susceptible or even more so than anything else.

I confess I used it only because I needed 3/4" and the scale of this boat precluded my buying even half a sheet of 3/4" for any other part of it.

Sounds like you got a sub standard piece of MDO? Like anything there are different grades & quality levels. The stuff I use is sold to sign makers and is outdoors 24/7/365. My supplier hears about it if the stuff fails and he's had some bad batches when his main supplier has been out of stock. It can be good stuff and the voids are filled like with marine ply when you get a quality MDO. Yours clearly had voids and was possibly a lesser grade, perhaps an MDO for interior use?.... Even marine ply is still wood and wood can rot if wet...