What Material, Aside From Epoxy, Can I Use to Close Out the Core?

[smj]

Chotu, do you ever get the feeling no one reads the entire thread before posting their fix? By the way, maybe you should try epoxy?🤣🤣🤣

[Chotu]

Originally Posted by Manateeman

Mark and his offgassing manatees

Ha ha ha ha!!!!

I’m dead over here.

Something about Mark and his off gassing manatees really struck me as funny.

Plexus is definitely on the list. Apparently it sticks to everything. It’s a direct substitute for epoxy In bonding situations and seems to come m all sorts of flavors with plenty of technical support.

[kmacdonald]

Originally Posted by Chotu

Ha ha ha ha!!!!

I’m dead over here.

Something about Mark and his off gassing manatees really struck me as funny.

Plexus is definitely on the list. Apparently it sticks to everything. It’s a direct substitute for epoxy In bonding situations and seems to come m all sorts of flavors with plenty of technical support.

If you like 5200 you'll love Plexus.

[Chotu]

Originally Posted by kmacdonald

If you like 5200 you'll love Plexus.

No 5200 as a gasket for deck hardware. It’s for bonding. Like plexus.

[Chotu]

Originally Posted by smj

Chotu, do you ever get the feeling no one reads the entire thread before posting their fix? By the way, maybe you should try epoxy?🤣🤣🤣

Right?

I think I’ll go with epoxy. Now who wants to get the boat in my will?

[lituya1617]

If you have ever put a finger to wet balsa dug out of a core, you will have a pretty good feel for how weak the stuff is, even if it is not rotten, which it usually is. When dry rotted, it becomes so fragile it is almost a powder. Not much compression strength there. The stiffness imparted by a core is real but every part of the deck and hull flex under load. Nothing can prevent that. If you must use a core, a closed cell 40+ psi polyurethane foam sheet works pretty well and doesn't hold water. It also adheres well to resin to prevent water-holding voids. Cleats are shock loaded and flex the deck quite a bit. The deck flexes enough to compress the core nearby and over time will weaken it and it will pull away from the deck and overhead layers if you do not put a compression sleeve between the deck and overhead layers. It is unwise to simply bolt on a cleat: it will leak, it will craze the gel coat, and it will rot out a balsa core. I have seen this happen dozens of times. I love 5200 but also know that it is a devil to remove once set. To me, that is a virtue. Do it right and you will never have to remove it!

[Chotu]

Originally Posted by lituya1617

If you have ever put a finger to wet balsa dug out of a core, you will have a pretty good feel for how weak the stuff is, even if it is not rotten, which it usually is. When dry rotted, it becomes so fragile it is almost a powder. Not much compression strength there. The stiffness imparted by a core is real but every part of the deck and hull flex under load. Nothing can prevent that. If you must use a core, a closed cell 40+ psi polyurethane foam sheet works pretty well and doesn't hold water. It also adheres well to resin to prevent water-holding voids. Cleats are shock loaded and flex the deck quite a bit. The deck flexes enough to compress the core nearby and over time will weaken it and it will pull away from the deck and overhead layers if you do not put a compression sleeve between the deck and overhead layers. It is unwise to simply bolt on a cleat: it will leak, it will craze the gel coat, and it will rot out a balsa core. I have seen this happen dozens of times. I love 5200 but also know that it is a devil to remove once set. To me, that is a virtue. Do it right and you will never have to remove it!

Really? Digging out wet balsa is your scientific analysis of its compression strength? How many psi did you come up with?

Why don’t you look up the actual values for Baltek 1” balsa and get back to me with the compression strength?
Ok, I’ll help you out. 3,184 PSI. That’s 3,184lbs on a square inch block of it to crush it. My backing plates are about 60 square inches. So what cleat do you have that puts out the 187,000 pounds of force it would take to crush my core by pulling the backing plate through it? That’s a hell of a line you must have attached to it.

Come on. Use numbers. Not “feelings”

So my deck cleats are going to bend my deck and leak, cracking the “gel coat “?

Really??

You’d better tell that to the cleats then since 2 of these cleats held a bridle.. connected to an 80lbs Manson Supreme.. that held this 50’ catamaran through a direct hit from a category 4 hurricane. The eye passed right over it. Better tell the balsa it has no compressive strength and tell the deck it’s floppy and the “gel coat “ (what boat with gel coat are you even taking about) that it’s going to crack.

Not a drip or a flex from a category 4.

YOUR deck may flex.. Mine doesn’t. YOUR boat May have a flexing polyester oil can hull with gel coat, mine is stiff as can be and made of epoxy and corecell mostly, with balsa in the spots where I needed the best compression strength.

Prior to becoming deathly allergic to epoxy, I drilled and filled my cleats with epoxy to keep water out.

This thread is about FINDING SUBSTITUTES FOR EPOXY SO I CAN MOUNT ADDITIONAL HARDWARE ON DECK.

The purpose of finding the substitute is to KEEP THE BALSA OR CORECELL CORE DRY.


It’s not just about cleats, it’s about closing out the core when cutting a hole for a hatch as well.

[Chotu]

Note: All my major deck cleats have already been installed for years. (No drips, no flexing deck, no water in the core) However, I may install some tiny ones to hold davit block and tackle lines. I also still have to install stancions for lifelines, some bolt on davits, etc. My winches and everything are planned to be on a sail control table indoors so none of them are on deck. And I have to install a million ports and hatches as well as chain plates.

[kmacdonald]

Originally Posted by Chotu

No 5200 as a gasket for deck hardware. It’s for bonding. Like plexus.

What do you use to seal hull and deck penetrations? Epoxy can seal the core but what seals the bolts from leaking into the cabin? If it doesn't leak into the cabin it won't leak to the core either.

[Chotu]

Originally Posted by kmacdonald

What do you use to seal hull and deck penetrations? Epoxy can seal the core but what seals the bolts from leaking into the cabin? If it doesn't leak into the cabin it won't leak to the core either.

Different materials for different situations. The manufacturer typically recommends something and using anything else voids the warranty. Say, in the case of Beckson ports for instance. It’s a silicone gasket you make out of silicone sealant or nothing. They expressly void the warranty if you don’t use silicone, which is surprising in a lot of ways.

Otherwise I’m partial to using butyl tape everywhere I can.

4200 is another go to.

You’re not trying to get adhesion up at deck level to keep the water out. You’re trying to make a gasket. So, you don’t need a bonding adhesive like 5200 up there. You need a mild adhesive (or none at all).

Your goal above the deck is to create a gasket. That’s why you don’t crank it down hard until after the sealant cures. Otherwise it crushes your gasket.

The cleats from my hurricane encounter have gaskets made from butyl tape actually. The one hatch I’ve installed has 4200.

These are definitely holding water out of the holes which holds out of the core, but I’m not inclined to trust those indefinitely.

Eventually, hatches need to be rebed. Before I notice a drip inside, the core is already toast, full of water. Not a risk I’m willing to take.

So, I typically drill (oversize hole) and fill with epoxy, then re-drill the holes so the core is sealed. Or in the case of cutting out a hatch, I de-core back 3/4-1” and take thickened epoxy and fill the whole edge.

However, I’m deathly allergic to epoxy now (from so many thousands of hours building boats) and need to find a substitute material that will stick to the existing epoxy skins and balsa or corecell core, sealing it off from any water that makes it through the 4200, butyl, etc.

That’s what the thread is about (for the millionth time).

[Chotu]

One more time here.

Any more thoughts on what can replace the “epoxy fill” in this picture to close out the core?

I need to be able to squirt it in as a liquid, have it seal tight to the upper and lower skins, forming a waterproof seal, and cure in a big lump without much air like in the picture.

[rslifkin]

Anything that cures solidly enough should work. Even polyester. If in doubt, just remove a slightly larger area of core to get a larger bond area. And if you like overkill, drill the hole larger, then remove core and back-fill, then bond in a sleeve to fit the bolt and take compression loads.


Personally, without epoxy, I'd probably use Vinylester for that job. Bonds better than polyester, but it's not epoxy.

[Scubaseas]

X2 on vinylester. Or use a structural adhesive urethane like
https://www.dupont.com/products/beta...tural-adhesive

[Chotu]

Originally Posted by rslifkin

Anything that cures solidly enough should work. Even polyester. If in doubt, just remove a slightly larger area of core to get a larger bond area. And if you like overkill, drill the hole larger, then remove core and back-fill, then bond in a sleeve to fit the bolt and take compression loads.


Personally, without epoxy, I'd probably use Vinylester for that job. Bonds better than polyester, but it's not epoxy.

This is exactly what I was hoping to hear. Ha ha.

Really, the main purpose of that filler is to close out the core and keep water away. There isn’t really a compression load on anything that I install. I don’t over torque it. I tighten it just the right amount.

Even the cleat in the picture. If you imagine pulling on that thing, in any direction, the washers and the Nylok nuts are what does the pulling on the laminate. But it pulls on the backing plate first. Which distributes the pressure along a very large area of the laminate. So the little bit by the bolts don’t really get much compression.

People had suggested plexus and things like that, but they are very hard to get. Especially right now with the pandemic.

[guyrj33]

Chotu;
I would let you work on my boat.
Many others who have replied without reading NO stay away.