Re: 1971 Flatback in Boca

[gran398]

For my rebuild, have been researching/obtaining opinions from various re-builders (Tampa area and Carolina)  regarding the sole adhesive/bedding material.  Epoxy and 5200 are not in discussion. Hold off as yet, will post their thoughts when gather all.

[gran398]

Here is what two of four advise so far:

http://www.itwplexus.com/industries/marine_app.cfm

[gran398]

There's some misinterpretation being thrown around about not sealing the wood completely regarding one of my past posts- what I was told by several wood boat builders - that leave their boats in the water most of the year - was to coat the wood completely with thinned resin, then coat the sides & bottom of the decking with regular non-thinned resin, lay the deck out & screw down then glass over the top.  I used this method on my 23' boat in 1995 & it's still solid.  The boat stays outside year round, but I do keep the hatches open to let it breathe.  I'd never leave just raw wood on the boat anywhere.   Heres a pic of the wood from around 2004 when I cut out a hatch opening, 5/8" BC plywood, not even marine ply.


The previous owner had completely encapsulated the wood deck with glass, then screwed it down.  The screws were not sealed well, water definitely got to the wood, his deck lasted about 5 years or less I'm guessing when I got hold of the boat, by then the deck was mush.  The extra layer of 24oz roven he used on the bottom side didn't help much strength wise, sealing up all the screw holes is key.
I do think that if water had never gotten to the wood it would've been fine wether it's glassed on both sides or just the top.

The wood by itself is plenty strong, the glass is only there to protect it, you really don't need to glass both sides for strength.  Foam core then yes both sides but thats a completely different scenario.  3/4" marine ply is overkill for the deck, 5/8" is enough unless you've got some huge unsupported areas in which case you should build some kind of reinforcement grids to the deck.  The factory 19' boats came with 3/8" ply.

No misinterpretation. Light resin (sealer) underneath  (no glass underneath). Glass on top for protection/water turn.  Looks great. And, its sixteen years old...natural crown...and not marine ply...wow.  Something to think about....those old boys...

 

[John Jones]

...natural crown...

One more point from my old dusty knowledge base.  Glassing one side of plywood will dang sure give you a natural crown, but on the wrong side.  Old bass boat restore years ago I had me a nice replacement deckr cutout.  The fit was great.  I put a couple of coats of resin on both sides, at least ten coats on the edges, then glass mat on the top side.  I had to go out of town a couple of weeks and when I got back the plywood had about a 4" reverse crown it.  I ended up having to flip the glassed side down and glass the other side and use that side for the top.  This also happens in woodworking when applying a veneer.  The info is out there on the web and in books but I was my hard-headed self and read the books afterward, not before starting the project.  I would suggest getting it attached quickly if you are only glassing one side.

Good luck and keep us updated.

[dbiscayne]

You're so right about the crown effect!  My first attempt at building a hatch ended up with a pretty good bow to it.  Fortunately the deck was screwed down to the stringers then glassed & glassed to the sides, still sits nice & flat.  I'm pretty sure I didn't put any kind of glue on the deck to stringer connection, just a big screw about every 2 feet, maybe more at the corners.  If I ever have to do it again I'd probably use thickened resin & a less screws.

On the type of wood issue, I've been told, & think I've read the specs somewhere, that BC grade exterior ply uses similar water proof glue to marine ply, & that the biggest difference is the finish (marine ply being much nicer), the marine ply has more plys per thickness thus being stronger (7 vs. 5 in a 5/8" thick piece), and the marine doesn't have any interior voids.  For my use on a deck that isn't spanning large gaps it seems the BC is working just fine, now if building an entire boat out of wood that'd be a different story.  I have used marine ply in the past, the prep work is less & you don't have to pick through the pile at the local hardware store to find a nice flat piece.

[seabob4]

A little "OEM" info here on how floors are installed.

If, for instance, the floor (sole) is part of the deck mold, Arjay polyester bonding putty is the bonding method of choice.  Plexus is only used for glassing in stringer grids (if that's the design).  The main reason is that most builders these days offer at least a 10 year warranty on the deck and hull.  Should a hull replacement issue come up, the deck and hull CAN be separated (albeit with a bit of force!) to the extent that the deck can be saved and re-installed on the new hull.  This type of warranty repair is done more often than the average person might think.  If Plexus were used as the bonding agent, well, the only way to separate the hull and deck would be in pieces.  On top of that, Plexus is prohibitively expensive in comparison to polyester putty, especially in the quantities that are required to deck a boat...

Now, if it is simply a floor that is being installed, well, this is the way Proline does their Pro-Lite series, which are built with out a deck.  The floors and foredecks are fabbed from Coosa Bluewater 20.  The panels are chopped on both sides, allowed to kick-off, scuffed with a grinder, them put down with the same poly putty.  Once the putty kicks off, the edges, or seams where the hull meets the floor, are filled with more putty, smoothed and faired in, then the entire interior gets splatter-coated.  Plexus would be way out of the cost picture due to the fact that PL wanted to keep costs as minimal as possible.  That was also the reason the 20 was speced in as opposed to the Bluewater 26, which is used on the "normal" Prolines...

All that being said, there is no doubt that Plexus is a superior adhesive to polyester putty.  However, when I have had to un-deck boats, I usually end up with gaping holes cut into the hullsides to access the interior stringers, used a sawsall to cut through as much of the putty as I could reach, then gotten a 6' pry bar with a helper on the 20 lb. sledge to get the two parts to separate.  Short of running the boat into a seawall at 30 MPH, the 2 parts joined with polyester putty are not going to come apart...at least not with a lot of help!

[gran398]

Hey, great advice...am forwarding this to my rebuilder. Thanks, S

[fitz73222]

I`m not trying to re-direct the dialog by any means just one question. When I recore the front hatches on the 22-2, how do I keep the hatches from bowing while the resin and glass cures? Wax paper, cinder blocks and prayer? Thanks!

[seabob4]

I`m not trying to re-direct the dialog by any means just one question. When I recore the front hatches on the 22-2, how do I keep the hatches from bowing while the resin and glass cures? Wax paper, cinder blocks and prayer? Thanks!

Fitz,
The problem with hatches is kind of two-fold.  One, you have a small area, and the curing effects (heat, shrinkage, etc.) have a much more pronounced effect as they have less mass to exert their forces on.  Second, because of the inexact science of the lam schedule, the mixing of the catlyist and resin, and the slight disparities in glass ratios from one side to the other, you can have a side of the hatch which has more thermodynamic forces than the other, and the result is the uneven aspect of the finished product, the "bow".  Almost all hatches have a slight, almost imperceptable bow to them.  What we used to do with the ones that had an "exagerated" bow was to place them on a good solid pedestal that supported the center of the hatch, then place lead at each end, out in the FL sunshine.  Place a support under each end you want to "bend" so that the hatch will only flex so far.  Over the course of a day, they'd usually straighten out.

Since no one but boat builders have lead ingots sitting around, cement blocks work fine.

[John Jones]

I'm no pro but I helped my buddy re-do his two gas tank covers on his Grady-White.  They would sag and pop when stepped on.  They had a poorly sealed plywood backing.  All we did was cut 1/2 plywood as large as would fit but not interfere with the covers going back in place.  We sealed the ply with resin while grinding down the under side of the hatches.  We put the hatches upside down on his garage floor and used thickened resin to attach the plywood to the hatch.  We piled everything we could find on top of the plywood.  Blocks, anvil, anything that had weight.  Take a rag with acetone and clean up the squeeze out to save grinding later.  His came out fine and those covers are larger than most hatches.  It's been three years and still holding.

[gran398]

JJ, did the same type of repair on my old hydra, worked fine, but instead of poly used West.  One of the reasons I keep old batteries around is to use them for weights.

[John Jones]

I usually use West Systems Epoxy but he is even cheaper than me.  I have a helluva time getting polyester resin mixed correctly because I never measure.  Poly usually kicks off before I'm done or never.  Ah, a couple more drops won't hurt.      I did finally learn to use shallow containers instead of deep ones.  Pot life is much longer because the heat doesn't build up as fast.  Epoxy is more work and money to paint over but if you use the right primer it's no big deal.  I have never used vinylester resin and I think there is a new one out now.

[LilRichard]

All we did was cut 1/2 plywood as large as would fit but not interfere with the covers going back in place.  We sealed the ply with resin while grinding down the under side of the hatches.  We put the hatches upside down on his garage floor and used thickened resin to attach the plywood to the hatch.  We piled everything we could find on top of the plywood.  Blocks, anvil, anything that had weight.  Take a rag with acetone and clean up the squeeze out to save grinding later.  His came out fine and those covers are larger than most hatches.  It's been three years and still holding.

Agreed - one other thing that helps is to drill a few small holes in the core before bedding, helps alleviate air bubbles.  I also did the "pile everything in the garage on top method", but have recently been vacuum bagging small parts and would do that next time for hatches (assuming I would ever rebuild another boat, lol).

[RickK]

One of the reasons I keep old batteries around is to use them for weights.

That's what I keep telling the wife too  

[John Jones]

one other thing that helps is to drill a few small holes in the core before bedding, helps alleviate air bubbles.

Great tip.  I never thought of that.