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

[Chotu]

Originally Posted by GeneM

I heard that someone used original gorilla glue because its absorbs moisture. It seems to have worked well.

Any PU glues like this that foam a bit less? Could make an excellent plug actually.

[Jim Cate]

Chotu, the shipwright who built our cedar/epoxy boat became badly sensitized to the epoxy... not as badly as you, but enough that he has permanent lung scarring and can no longer use epoxies.

since then he's used vinylester resins in construction without issues... whole 45+foot hulls with some form of foam coring. They seem to be lasting just fine, and he hasn't had reactions to the resins. He is a LOT more careful about exposure than when he was young and immortal, but it has worked for him.

So, in your place I'd sure be looking at VE rather than PE. As shown in a post upthread its properties are much better, especially where secondary bonds are involved.

Jim

[rslifkin]

Originally Posted by Chotu

Sorry you had that problem. I think that has to do with a wet environment.

I used polyester to tab my wooden cabin soles to the epoxy hull and it’s all just fine. It is also used to completely seal off the wooden soles from the air and whatever humidity is in it.

It’s not the product. It’s the application.

Never use polyester below the waterline on wood.

All of the bulkhead and floor tabbing in my boat is roving and polyester. None of the floor or bulkhead tabbing shows any signs of failure after 34 years, so it's definitely possible for it to work. It probably just requires a larger surface area and more attention to how it goes together to ensure a good enough bond.

[Chotu]

Originally Posted by rslifkin

All of the bulkhead and floor tabbing in my boat is roving and polyester. None of the floor or bulkhead tabbing shows any signs of failure after 34 years, so it's definitely possible for it to work. It probably just requires a larger surface area and more attention to how it goes together to ensure a good enough bond.

That’s some good data.

I think the other guy was talking about below the waterline, exterior use. On his canoe.

And I think you’re right about the larger bond area. I used 12"biax tape to bond the floors to 5je hull the in mine. It's going nowhere.

I even did a test patch of thickened polyester on the epoxy interior wall to make for something I can actually sand without worrying about it. Can't pry it off with a screwdriver.

[Chotu]

Originally Posted by Jim Cate

Chotu, the shipwright who built our cedar/epoxy boat became badly sensitized to the epoxy... not as badly as you, but enough that he has permanent lung scarring and can no longer use epoxies.

since then he's used vinylester resins in construction without issues... whole 45+foot hulls with some form of foam coring. They seem to be lasting just fine, and he hasn't had reactions to the resins. He is a LOT more careful about exposure than when he was young and immortal, but it has worked for him.

So, in your place I'd sure be looking at VE rather than PE. As shown in a post upthread its properties are much better, especially where secondary bonds are involved.

Jim

Ok, Jim.

I guess there are a couple different kinds of polyester. It's the amine hardener I have to stay away from with epoxy.

Some VE has amine hardener, some seems to use MEKp. I need the latter.

[Mike Banks]

If you are placing deck hardware in a cored deck, the deck should not be cored in the way of these fittings.

Retro-fitting equipment in these areas requires a bit of time, effort and money. The core has to be removed, the area under stress from the fitting has to be defined, the core has to be removed entirely as does the interior laminate, which should be tapered back to zero on the remaining edges of the interior laminate. That gives a big shallow cone edge with at least a thirty degree taper cut around the edges of the area for placing your fitting.

Now, in place where the fitting is to be placed, place a layer of chopped strand mat, for EPOXY use. You have a messy job here in that it has to be done from below, and properly bonded to the underside of the existing deck skin, out over the entire fitting base area and down over the taper finishing just above the interior skin, leaving unsaturated the glass hanging down, which will be removed later after an initial set but before a final cure. The entire glassed area has to be properly consolidated.

There are two ways to proceed from here. I use the latter method, but I will mention both.

Method 1.: Continue to build out the layers of glass until you have completely filled the entire area, then saturate any ends previously trimmed, and cover the lot with peel ply and consolidate firmly the entire area.

Method 2": Cut laminates of hardwood ply, and accurately make them to fit into the spaces, each will be slightly larger than the previous piece, and as each piece is fitted into place using epoxy-and talc as a filler, secure it using a jack or prop to keep firm but not heavy pressure on it. When it has taken up a set, put in place a sheet of woven glass cloth, and saturate it, taking the edges of the cloth out to the extent of the walls of the taper and a little more. Then butter up your next piece of plywood with a thin layer of epoxy talc, and press it firmly into position. Cover it with a layer of saturated glass cloth. Continue until the entire cavity has been filled and the last of the ply covered in an epoxy glass layer of cloth.

From now on, both methods are the same.

Depending upon what sort of fitting is being placed on the deck, the underside has to be tied to the main strength members of the hull. There are several ways in which this can be done. The simplest of all being a sheet of heavy marine plywood cut to fit against bulkheads, deck shelves, ribs etc, which will transfer the loads from the fitting into the vessel generally.

The other method is to determine the directions from which such loading might be imparted to the cleat foundations, and to reinforce those foundations using extra scantlings glassed on to the existing hull interior and terminating on strong points within the vessel. Deck beams, deck shelves, bulkhead cross-members, etc.

So it is not a simple job.

For light fittings not used to moor a vessel or mount a halyard winch or something of that nature, replacing the core with laminated plywood and fitting a substantial backing plate and mounting base might do it.

If you are allergic to epoxy, you may have to get someone else to do it or wear breathing apparatus. There is no equivalent substitute for epoxy for retro-fitting hardware and fittings, but vinylester is as close as you will get. Some epoxy resins are more dangerous than others, and the safer they are the more expensive they are. If you are already sensitive, you could try using vinylester.

Once your deck filling it has initially cured and gained most of its strength, sand and paint it. The final cure will continue for months in colder areas.

The bolts for whatever fitting you intend to use are now able to be placed, through the fitting mounting holes, through the bedding or mounting timber, through the deck, and through the final backing plate. I drill all of the holes, then saturate the inside of the holes using epoxy resin. Where the mounting block for the cleat sits on the deck. I put an O-ring on each of the bolts. They are FIRMLY tightened. NOT fully tightened.

[Chotu]

I just found this:

https://www.3m.com/3M/en_US/company-...3193904&rt=rud

A non foaming polyurethane glue. This could be just the right thing.

[Chotu]

Mike, I appreciate the write up, but 25mm (1") Balsa core is as strong in compression (if not stronger) than marine ply. That's why it was used in the deck. Because I can mount the hardware anywhere it is.

I already mounted my cleats about 5 years ago. The boat was at anchor through a direct hit of a category 4 hurricane. The eye went right over the boat. 2 cleats were attached to the bridle. Nothing else. An 80lbs Manson Supreme on the other end in the sea bed. Result? They held fine. No leaks, no stress cracks, no flexing. A window on the bridgedeck was blown out by wind. That was the only damage.

Cleats were installed just like we're talking about here. Drill and fill through the 1" balsa core. Epoxy was used back then because I could still use it. Huge fender washers and a ply doubler with backing plate. Zero movement.

I'm just looking to find a good substitute for epoxy for drill and fill. Something that will bond to the Balsa and epoxy glass, as well as stand up as good as the balsa in compression.

The actual load of the deck gear isn't in the fasteners. It's coming from the backing plate, which is large and can't pull through the deck.

So there is no need to take out the complete core under deck fittings. The core was chosen to support any loading required of it.

[Uncle Bob]

Originally Posted by mikereed100

The problem with using polyester for plugs is that it can be very brittle (don't ask how I know this). If you go that route I would use milled fibers to thicken the resin.
Fillers
That should go a long way towards preventing cracking and will give you better compression strength. Vinylester, while a bit more expensive, would be my choice in this application as it is less prone to cracking, has better water resistance and bonds better to core materials.
https://www.thoughtco.com/vinyl-este...-resins-820376

+1. Especially the vinylester resin suggestion. I agree with the suggestion of increasing the plug size. Also the idea of countersinking the deck to allow the sealant to create an "o ring"works extremely well.

[Westcliffe01]

I think that for high stress/compression applications, G10 phenolic resin/glass rod or plate is the way to go. Used in aircraft structures for wing attachment and such like.


https://www.usplastic.com/catalog/it...x?itemid=40894

• G-10 is a light green, colored continuous woven glass fabric laminated with an epoxy resin
• G-11 is a green, glass epoxy with mechanical and operating temperatures that are superior to FR4

NOT the canvas stuff !!!!!!!!!!


Its not cheap, but good stuff rarely is.

[rslifkin]

Originally Posted by Westcliffe01

I think that for high stress/compression applications, G10 phenolic resin/glass rod or plate is the way to go. Used in aircraft structures for wing attachment and such like.


https://www.usplastic.com/catalog/it...x?itemid=40894

• G-10 is a light green, colored continuous woven glass fabric laminated with an epoxy resin
• G-11 is a green, glass epoxy with mechanical and operating temperatures that are superior to FR4

NOT the canvas stuff !!!!!!!!!!


Its not cheap, but good stuff rarely is.

He'd have to get someone to cut and drill it for him, but that stuff is great for backing plates. My bow pulpit, windlass, and samson post are all mounted through a reinforced piece of deck with a 2ft by 2ft sheet of G10/FR4 epoxied to the bottom as a backing plate. The impression I got from tightening the fasteners was that the whole assembly is rock solid and if I break it, I've probably torn a very large hole in the boat.

[Manateeman]

I never used anything but epoxy and stuff mixed in to it.
Plexus??
Never tested it before for this application.
Comments.
Manatee

[Westcliffe01]

A mini lathe is probably $500-600. Can turn out an awful ot of widgets with one of those as opposed to paying a shop $80-140/hr to do something for you...

Originally Posted by rslifkin

He'd have to get someone to cut and drill it for him, but that stuff is great for backing plates. My bow pulpit, windlass, and samson post are all mounted through a reinforced piece of deck with a 2ft by 2ft sheet of G10/FR4 epoxied to the bottom as a backing plate. The impression I got from tightening the fasteners was that the whole assembly is rock solid and if I break it, I've probably torn a very large hole in the boat.

[rslifkin]

Originally Posted by Westcliffe01

A mini lathe is probably $500-600. Can turn out an awful ot of widgets with one of those as opposed to paying a shop $80-140/hr to do something for you...

I wasn't thinking of a tool related issue in cutting or drilling G10. You can buy pre cut pieces, but it's made with epoxy, so drilling would be risky for him due to dust.

[Scubaseas]

Vinylester, last I read, was a lot more epoxy like in that is used an amine hardener.

MEKP is the catalyst for vinylester same as for polyesters. It's not an amine process