Glassing around deck openings, hawsehole

[Klos2019]

I am in the process of replacing balsa core in a 3' x 4' section of my foredeck due to water intrusion rotting the core around a previous owner's poor windlass installation.

I've cut off the upper layer of deck, cleaned out bad core areas and will be putting in new balsa core and reusing the top skin, etc, etc.

I will be putting windlass hardware back in same orientation and using the same holes through the top and bottom layers of glass and am looking for suggestions or advise on epoxy application around these holes. My thought is to leave 1/2" to 1" gap in the core material around edge of these holes and fill these with thickened epoxy to ensure core is fully sealed off.

I'm wondering if using an epoxy mix with chopped glass might better than standard filler or in addition to it so that the edges of these holes have a bit more strength, and aren't too brittle being they are 2-3" diameter.

Any advise or ideas?

[Jim Cate]

I'll leave the f/g advice to the usual suspects, but would strongly advise using plywood or other denser material as coring in way of the windlass. The tiny weight increment is inconsequential and the additional crush strength is useful around this highly loaded area of deck.

Jim

[coopec43]

Originally Posted by Klos2019

terial around edge of these holes and fill these with thickened epoxy to ensure core is fully sealed off.

I'm wondering if using an epoxy mix with chopped glass might better than standard filler or in addition to it so that the edges of these holes have a bit more strength, and aren't too brittle being they are 2-3" diameter.

Any advise or ideas?

I like the idea of using epoxy with glass fiber but make sure the chopped glass is compatible with epoxy. (Normal Chopped Strand Matt (CSM) is not)

I've used marine ply under all my deck fixtures - hand rails, winches, rope clutches, deck organizers but apparently there is a better (synthetic) material available these days..

I think what you are doing is along the right lines but I'd use something like Sika 291 to seal right around the winch/deck join and I'd put Sika in the bolt holes to stop water seeping down the bolt holes into the core.

Here are a few acceptable ways of mounting hardware in a cored deck.

[Nicholson58]

I really like Materials from aUS Composites, 635 THIN resin and 3M micro balloons as filler instead of balsa, wood, foam. The mix is waterproof and has 3000 psi compressive strength. See my photos for rudder rebuild and recoring the deck from inside. Use glass build up where loads are high.

https://www.cruisersforum.com/galler...0&userid=49581

You will save money with this resin. It’s used for marine construction. If it has not reacted you can clean up with liquid soap. It has a very long working/reaction time and great wet-out.

Epoxy :Â*Epoxy Resins and Hardeners

[Fore and Aft]

Klos2019 chop strand is no good with epoxy but you could find find some double bias or Uni's to mix with the filler. But before you mix the glass strands in the filler you will need to wet them out first just because the filler will not wet them out if you mix them in dry. It's a pity you went back with Balsa on the bow deck as you could have used a high density foam and not worried about coring out the deck.
Thinking about it even a small bit of foam around the anchor winch area would work if the budget is tight.
Cheers

[Chotu]

No need to do anything else. Baltek balsa has a compressive strength over 3000 psi.

Just oversize the holes as you have decided to do and use glass fibers if you feel it’ll help (it’s not all that necessary).

The important thing is you spread the load with a nice, wide backing plate.

I did this exact setup for deck hardware and 2 cleats held my boat at anchor through a direct hit of the eye of a category 4 hurricane.

Not a bit of movement on my cleats no leaks dripping inside.

I also use butyl tape under the cleats to keep drips out of the interior. The drips cannot get into your core if you drill and fill as you are planning.

Go right ahead with your plans, but make sure you spread the load out with a nice, big backing plate.

[Chotu]

Originally Posted by Fore and Aft

Klos2019 chop strand is no good with epoxy but you could find find some double bias or Uni's to mix with the filler. But before you mix the glass strands in the filler you will need to wet them out first just because the filler will not wet them out if you mix them in dry. It's a pity you went back with Balsa on the bow deck as you could have used a high density foam and not worried about coring out the deck.
Thinking about it even a small bit of foam around the anchor winch area would work if the budget is tight.
Cheers

In my opinion he made the right choice. He’d have to use special high density foam in these highly loaded areas to get the compression strength of balsa.

And you still need to close out your core on a foam boat. Water ingress is detrimental to all cores. Hydraulic pressure inside foam cores leads to delamination.

[s/v Jedi]

Here’s the best way to do this: before gluing the top skin back, remove 1.5” diameter of core material at each fastener position. When the top has cured, close the bottom of the fastener holes with duct tape. Mix a tiny bit of epoxy with slow hardener and use a small brush to wet out the area of the cavity. Use epoxy with (extra) slow cure hardener and mix in microfibers to a consistency of thin syrup. Then add (West System) high density filler to make it a thick syrup consistency that still runs and pour it into the cavity. Use a toothpick to agitate and get the air bubbles out from under the top layer of glass. Keep an eye on it during cure as you probably have to add a little more.

The main reason for this is to seal the core so it can’t get wet but using the high density filler also prevents crushing the core. I’m told this high density filler is animal bones that are ground to a powder.

[Chotu]

Originally Posted by s/v Jedi

Here’s the best way to do this: before gluing the top skin back, remove 1.5” diameter of core material at each fastener position. When the top has cured, close the bottom of the fastener holes with duct tape. Mix a tiny bit of epoxy with slow hardener and use a small brush to wet out the area of the cavity. Use epoxy with (extra) slow cure hardener and mix in microfibers to a consistency of thin syrup. Then add (West System) high density filler to make it a thick syrup consistency that still runs and pour it into the cavity. Use a toothpick to agitate and get the air bubbles out from under the top layer of glass. Keep an eye on it during cure as you probably have to add a little more.

The main reason for this is to seal the core so it can’t get wet but using the high density filler also prevents crushing the core. I’m told this high density filler is animal bones that are ground to a powder.

Precisely!!

[jimbunyard]

Originally Posted by s/v Jedi

...I’m told this high density filler is animal bones that are ground to a powder.

As opposed to plant bones?

According to West's literature, 404 (high density filler) is 80-100% calcium metasilicate mineral, also known as wollastonite, 5-10% siloxanes, silicones, di-Me, reaction products with silica and .1 - 1.5% silicon dioxide (quartz, crystalline silica).

https://www.westsystem.com/wp-conten...ds/404-SDS.pdf

As for the original inquiry, pretty much any standard thickener will work, but for a 2 or 3 inch diameter hole I'd be more inclined to just use whatever glass you're using to do the repair, cut to the size you're filling (which will make it easier if you're using standard balsa core; rectangles are easier to cut that circles). About 13 layers of 1708 biaxial would equal about a 1/2" of balsa core...

[jharding]

if it were me I would not put any wood coring where the windlass mounts, I would get some GP03 fiberglass board from Mcmaster carr, it is available in many sizes and use that for coring, it is very strong and no need to worry about water getting in. I would also use a bigger plate of GP03 underneath as a backing plate it can be epoxied to the underside of decking.

[JBP]

If you still have the skin off, lay up some glass cloth or G10 instead of filling it afterwards.

[Cadence]

Don't use microspheres/balloons. Use commercial talc.

[Scubaseas]

You might consider Coosa Board instead of Balsa. It's typically used for power boat transoms. Perfect for a windlass mounting. Bluewater 26 would be my choice. Marine ply as a second choice but the Coosa is a structural panel by itself.

[Fore and Aft]

Coosa board was what I had in mind, jharding had the idea about solid glass board which would work. If you had a bit of old resin and cloth laying around and a large old tupperware container (Bigger than the winch base to be used as a mould) you could lay up your own inch thick fiberglass core. Thats a favourite way of mine to get rid of fibergass offcuts and old resin.
Cheers