Deck Delamination / Core Problems

[ElBeethoven]

If you have recored a deck in your life, and that boat did not subsequently sink, I would like to know what products you used and if you were happy with how it was still doing X, Y and Z years later.

Mike, I know that you place the new core on a thickened epoxy layer on the lower skin. My suggestion about thinned epoxy was to coat the cut and shaped plywood for the core BEFORE placing it in the deck thereby sealing it so it wouldn't rot, and I won't have to do this again for another 42+ years. Has anyone ever heard of anyone doing this? Or anything LIKE it?

I agree that closed cell and its inherent rot-proof, inorganic nature make it a mighy fine core material, but it's cost prohibitive to me. Simple as that. And let's not forget that a properly executed and sealed balsa deck lasts a long, LONG time and costs far less than the exotics.

By way of explanation, before college I lived and cruised on a Paceship 26 for about five years making most of the mistakes that I now intend to avoid. I'm aiming for "seaworthy." Not perfect. Not restored. Not museum quality. There might be dings in the gelcoat. OK. The brightwork might be faded. Fine. There will also be completely new standing rigging with 1/4" - 316SS and Sta-Lok terminals, 200' of 1/4" chain, three slightly oversized anchors, all new electrical wiring and, so it appears, a new deck if I purchase #120.

Beyond a sound hull and deck and killer ground tackle, the rest is detail work, detail work for which I know it is almost impossible to specify costs. Still, I can easily figure that 1/4" wire is $1.45/ft, and Sta-lok terminals are $38.50 each. I need around 161' of the former, and I need 16 of the latter. A 22-lb Bruce anchor is $122.99. Chain is $1.47/ft. See? (BTW, these are all real prices that I've found on the web. If you need to know where I've found them, please ask!) I'm not looking to balance to the penny. I'd just like to be able to say that a new deck will be around X dollars. It CAN'T be that hard. Civil procedure was hard. Cognitive neuropsychology was hard. My job.... let's not go there.

OK enough rambling. But now you can see where I'm going with this. So I'm still begging for suggestions.

I'll post some more pics later tonight. I need to Photoshop them down, or Bill might come after me.

All the best!

J.

For your amusement: "Wooden boats regularly die early deaths of natural causes; fiberglass boats must be assassinated." - Don Casey

[mrgnstrn]

Mr. El B.,
I can relate because, I too, am Nerdly.....and proud of it.
Maybe it is the Engineer in me.....OK....it is the engineer in me.
I have a great resource for this kind of stuff:
Oceana Limited in Annapolis.
www.oceanaltd.com
They have a crappy website, but awesome hardcopy catalog.
Their number is 1-800-523-8890.
They cater mostly to commercial-type boatbuilders, marinas, etc.

but...you asked about core material.
Here are some prices for 1/2" thick material (I think that is ~ the right size)
ATC Core-Cell, "A500 grade", Plain, no cross cuts: $167/(4'x8'sheet)
Baltek, "contourkore", "CK100" grade, $32.60/(2'x4'sheet)
ditto......ditto....."AL-600R" grade, $36.74/(2'x4'sheet)
Airex PVC closed cell foam, "contourable" $51.78/(24"x42"sheet)
ditto......ditto...."rigid" $115/(48"x58"sheet)

Then there are some composites that may not be suitable for core on decks, but maybe as a replacement for plywood (but really, I have no idea, but from looking and playing with the samples in their shop, it can be really really stiff):

Coosa Composites, composite panels, Highly rigid, with fiberglass strand and roving inside the panel:
$303 - $209 depending on density and strength, all for 4'x8' sheets.

like I said, these are all prices for 1/2" material, but they have others available, and also some other "styles", like material that has more cuts to make it more flexible.

For stories and experiences, the Triton guys have some good accounts on the web, both with balsa, and with composites.

For how much epoxy, not sure, but my experience with epoxy is that it gets used up ~twice as fast as I expect. Not sure why.

As for epoxy vs polyester, there are plenty of opinions on both, but again, there are some accounts on using epoxy and using regular polyester from the Triton guys. And for more opinions on E vs P, plenty in a few threads on this forum to digest before making that decision.

Hope this helps a little.

[Mike Goodwin]

Ebb,
I get my foam cores from the same place I was buying surfboard foam back in the 60's.
I comes in 2x4 , 4x4, 4x8 etc, sheets and in thicknesses from 1/4" to 2" and possibly thicker.
I like one called Wes-Core , looks like a slice of honeycomb , some is yellow and some green, works easy , bonds to epoxy or poly resin .
I don't like thickening epoxy with cabosil as a general thickener it is too hard and brittle , milled cotton fiber is good along with a dash of "Barney Dust" .
Fine hardwood sawdust (wood flour) from the bandsaw is far superior to cabosil
Even better is a pre-thickened epoxy out of Fla. and it is much cheaper than WEST, EAST or SYS-3 . 1:1 very forgiving mix, choice of fast medium or slow hardeners.

ElBee, Ply is probably the worst core material choice I have ever seen or repaired . Boats with ply core decks are generally valued lower in surveys than a balsa core boat.
Water travels through ply from one end to the other with ease . When you paint the ply with epoxy thinned or not , it wont penetrate past the glue lines if it gets that far. In other words it can still rot, seen a lot of it too!
Good ply will cost almost as much as good core and be harder to install .
You would be better off using balsa core , a lot faster , cleaner and cheaper. Use end grain Mahogany blocks where hardware will be mounted .
Use a non-blushing epoxy , because it will take many sessions to do the job.
Acetone is not epoxy thinner BTW.

BTW,
In the last year I mixed up over $20,000 worth of epoxy on one project .

[natalie e.]

Now that I am on the right page I am on to my next project of removing the two decks on each side of the cabin from the chain plates back almost to the winches. I have read the good old boat article attached to this forum and understand cutting away the top fiberglass skin to reuse then removing the old core. I did not understand cutting and laying in the new core in 3" strips, shouldn't the new core be layed in whole on top of the epoxy mesh. Also any idea of the thickness of core (marine plywood)? I am contemplateing removing the foredecks also, they are not as mushey but are giving way.
Thanks in advance for all your help. I will show pics of my motor city girl as I continue my dream.

[CapnK]

Hi Natalie -

Congrats on living your dream! I am too.

3" strips would make handling the core as you lay it in easier, I'd think., but you don't *have to* do it that way. If you made sure to get resin/glass between the strips as you laid them in, it would also significantly increase the strength of the deck (think lots of I-beams, 3" apart, under the top skin, if you did it that way).

Looking forward to seeing some pictures.

[Mike Goodwin]

Marine or any ply is almost the worst core you can choose . Use a closed cell foam and join the 21st century .

[natalie e.]

thanks for your replys. Do you know where to find this 21st century core and any idea of the thickness I would need??.

[Bill]

There is a thread on this. Please use the search button.

[tha3rdman]

I've sifted through this and the other thread that concerns recore. I had a lengthy discussion with a distributer, and he convinced me that replacing the balsa with balsa would be the best bet. He sites the compressive and sheer strengths of balsa vs the foams, and the need to go with a extremely high density to get the identical stiffness as the previous stiffness. It could be all smoke and mirrors, but for the cost comparision . . . I'm convinced that if one properly bedded the hardware in the first place the deck would not have gone soft. It's lasted nearly 40 years, and another 40 would be A-ok.

My question is about scarfing knowing a 12:1 or 10:1 is ideal, has anyone considered using a high grit (40 or 60) sanding disk to cut through the skin leaving the scarf and cut all in one swath. Versus circular sawing then having to sand the edges to obtain the scarf.

[ebb]

Don't know that you need to scarf anything, if you are using the word in its traditional way.

Suppose you could tilt the circular saw at 40/45 degrees to cut out the pieces so that if you are going to replace the original deck the pieces could be glued back like lids. However, the top skin of the deck is 1/8" maybe a little more if you're lucky. Any cut at any angle with a circular blade would cut more material away than the slant. IE the piece of deck/lid would be smaller than any hole you can cut. A grinder would be less accurate, unless you're thinking of using a dremel-tool.

I believe a straight 90 degree cut with a small circular saw and carbide blade set at a known depth would give you more control and accuracy. Use the grinder to vacate the tunafish - VERY careful not to grind thru the inner skin. Bedding the balsa in epoxy and epoxy gel (Epoxy, fumed silica, chopped strand*) will give you a strong deck without worrying about scarfing anything.

You may end up laminating your own deck skin back on top - rather than glueing the 'lids' back on. Conceivably it is stronger and more unified to laminate new deck back on top of the new core. Because you can marry it better to the remaing deck. However, it is conceivably easier to glue the deck pieces back on because you get an instant register with the remaining deck structure.

With the 'lid' method, after they're back on and the epoxy is set, you could grind a mild dip/depression around all the seams, three or four inches wide across the seam and fill it with strips of glass cloth and epoxy. Narrower strips in the bottom, with the next layer using wider strips. You'll only get maybe two/ three layers with the top one nearly grinded off for flush. This ought to graft the new work with the old pretty good.

With all new top laminate I would feather on to remaining deck by grinding a 'slope' on it.
This is what you meant by scrafing, I think.
It's not much, as the deck skin is so thin -just enuf for one or two layers of six or eight oz cloth to lap onto it. But with enuf buildup to grind the join down flush. Conceivably this is the stronger method. But I think it's a toss-up.

AND I always say this:
With work like this use only 100% solids laminating epoxy. Your supplier should tell you that it is NON-blushing and has so solvents or extenders in it. A great privilege of no-blush is that it will allow you to stop work and continue later without the penalty of washing and often without prep.
__________________________________________________ _____________________________________________
*because the deck is horizontal, you need to thicken the epoxy filler only a little, just enough to control it. It should still flow so that it fills all voids and fills the baltec as well. Butter all pieces on all sides. Prefered method is to wet down/soak all surfaces with straight epoxy first, then butter. To avoid voids: You may find that drilling (for neatness) some holes in the center of panels, or where you know you have a depression to fill, that when you press the panel in its place the extra glue has a path to squeeze out like a relief valve.

Balsa with epoxy, imco, is as good if not better than expensive pvc foam for our deck restoration. Like you say, if you isolate it from thru fastenings, etc it'll last. The above method would isolate the balsa extremely well. Epoxy is a good waterproofer - and if you urethane the deck, whatz gonna happen?? And each panel is isolated so any water migration could not be a problem in the future. Some boats like 338, knock on wood, still have good decks after all these decades. Done right, new balsa composit should last a half a century! You know, like THREE generations!!
Sorry. Hope some of this diffuse stuff is usefull.

[mbd]

Hey 3rdman,

FWIW, I'd go with MikeG's 40+ years experience and use a foam core. My side decks are plenty stiff with the Corecell.

Agreed: properly mounted hardware etc. will keep the core dry, BUT, it's hard, nigh impossible to keep all water out 100% of the time. No telling where it'll come in, mounted hardware, port light frames, a hastily drilled fastener... It's nice knowing that no matter how badly I mount/seal my hardware, the deck core will NEVER rot again.

As to scarfing, my 2 cents. Cutting the skins first is the way to go. A lot of mine were still adhered to the core, and it would have been impossible to separate them without breaking had they been pre-scarfed. Also, a clean cut line gives you a nice reference for doing the nasty grinding for the scarf joints after the skins have been glued back on.

Doh! Capt Ebb's reply just came in. Hope I don't contradict his wisdom...

PS. Then there's Craig's post above - I'd like to have seen pics and have more detailed info on his POs recore/repair. All sorts of opinions out there...

[tha3rdman]

Ebb & Mbd,

Thanks the balsa is in route, the price was too good to pass up, I'll make sure I designate a photographer for "in progress" pics, even if its the seven year old swabby. As for epoxy, I'm likely getting the epoxyproducts premium no blush.

I'll keep ya posted.

[mbd]

Just to revisit this thread, here is what a section of deck looks like with a Corecell core.