Bulkhead repair suggestions Gemini 105M

[tharch]

Originally Posted by s/v Jedi

You need room for the epoxy glue. Take a couple of toothpicks and superglue them to the repair piece to be glued into the cavity. The thickness of the repair piece incl. The toothpick should be the depth of the cavity. Now you can use a notched spreader to apply epoxy glue to the cavity and press the repair piece in firmly. The toothpicks will act as spacers to make it completely flush while still leaving ample space for the epoxy. You need to add filler to the epoxy: first microfibers to syrup consistency, then add colloidal silica to peanut butter consistency. The nothes in the spreader twice as high as the toothpick diameter, but try it on the scrap piece… pull the repair piece off again and see if there was enough epoxy. Now you know how much to put in the cavity.

There should be a tiny bit of epoxy visible around the perimeter of the repair piece. 1/64” is plenty. It will become a dark line when finished.

I would use meranti plywood. I think you have jatoba, which is sometimes called exotic cherry. It’s darker than domestic cherry and like domestic it will darken with Uv exposure. You will never get it to match so make it contrasting instead. This works much better than hiding it.

Thanks Jedi. I am not too worried about matching it. I can happily paint all of it one color. I think i will go with a front and a back doubler plates fur peace of mind

[coopec43]

Well you have been warned!
Good luck.......

SailingHarmonie
Registered User


Join Date: Jan 2023
Posts: 1,576


Re: Difficulty of repairing side deck delamination and bulkhead decay
About that rot in the bulkhead… be scared. Very scared. I know it’s not your boat yet, and you can’t do even minimally destructive tests, but I bet if you stabbed that bulkhead with an ice pick it would slide in as if it was rice pudding.

This is not a boat worth the $ and sweat likely needed to fix this. As others have said, it will be worse than it looks.

[tharch]

Originally Posted by coopec43

Well you have been warned!
Good luck.......

SailingHarmonie
Registered User


Join Date: Jan 2023
Posts: 1,576


Re: Difficulty of repairing side deck delamination and bulkhead decay
About that rot in the bulkhead… be scared. Very scared. I know it’s not your boat yet, and you can’t do even minimally destructive tests, but I bet if you stabbed that bulkhead with an ice pick it would slide in as if it was rice pudding.

This is not a boat worth the $ and sweat likely needed to fix this. As others have said, it will be worse than it looks.

I know right!
However, the side i was worried about is solid and it is the other side that looked perfectly fine and sounded good that is decayed! The surveyor missed it too. He pointed out the same area that was discolored but is solid and missed the normal looking devayed area

[Sos]

I would also have a good look at the chainplate and try to see why it was leaking and then make sure it doesn't happen again and have a good look at all the others.

[tharch]

Originally Posted by Sos

I would also have a good look at the chainplate and try to see why it was leaking and then make sure it doesn't happen again and have a good look at all the others.

Yes sos. I saw where the water ingress was. I will take care of it once the new chainplates are installed

[Bowdrie]

Originally Posted by tharch

Yes sos. I saw where the water ingress was. I will take care of it once the new chainplates are installed

A very common mistake that is made when chainplates are inserted thru slots in the deck/housetop is having the slots just barely clearing the metal.
1, There must be sufficient clearance around the metal to allow a good thick amount of sealant, that's the only way to allow a reasonable amount of flexing without breaking the bond, this is especially important when the chainplate angles do not exactly match the rigging angle.
2, Use a pad of 3/8th G10 on the deck/housetop to give a raised surface to eliminate any possibility of standing water around the metal.
3, Use a Polysulfide, the Polyurethanes do not offer as much adhesion to the metal.

[coopec43]

This is the sort of repair I would have expected.

https://doctorsailboat.com/2019-06-rotten-bulkheads/

[smj]

Looks like a small area of rotten plywood, so I would cut it out, scarf in a new piece of plywood with a decent bevel using epoxy as a glue then ad a couple layers of glass on each side. With the added glass it should be stronger than original.

[coopec43]

Originally Posted by smj

Looks like a small area of rotten plywood, so I would cut it out, scarf in a new piece of plywood with a decent bevel using epoxy as a glue then ad a couple layers of glass on each side. With the added glass it should be stronger than original.

You'd be happy that would hold a 60kg mast (plus the weight of rigging) swaying about in choppy seas?

[smj]

Originally Posted by coopec43

You'd be happy that would hold a 60kg mast (plus the weight of rigging) swaying about in choppy seas?

Absolutely

[tharch]

Originally Posted by coopec43

This is the sort of repair I would have expected.

https://doctorsailboat.com/2019-06-rotten-bulkheads/

Coopec43

Thanks fir the link. I read through that. When considering similar areas of repair, they seem to be doing the save thing, cut out rotten part, put a new piece on and fiberglass it. Main difference appears to be that the glassing extends to the hull. Am I missing something?

Gemini bulkheads don't seem to have been designed that way. They appear to be designed with some give. I don't know enough about boat structures to alter a fundamental design criterion.

Thoughts?

[tharch]

Originally Posted by smj

Looks like a small area of rotten plywood, so I would cut it out, scarf in a new piece of plywood with a decent bevel using epoxy as a glue then ad a couple layers of glass on each side. With the added glass it should be stronger than original.

Thanks smj. It has two chain plates forward and one on the other side. I can put a scarf piece to replace the rotten part and also add a sister plate in the back that spans the new and old but solid part for extra strength

[tharch]

Originally Posted by Bowdrie

A very common mistake that is made when chainplates are inserted thru slots in the deck/housetop is having the slots just barely clearing the metal.
1, There must be sufficient clearance around the metal to allow a good thick amount of sealant, that's the only way to allow a reasonable amount of flexing without breaking the bond, this is especially important when the chainplate angles do not exactly match the rigging angle.
2, Use a pad of 3/8th G10 on the deck/housetop to give a raised surface to eliminate any possibility of standing water around the metal.
3, Use a Polysulfide, the Polyurethanes do not offer as much adhesion to the metal.

Thanks for that bowdrie. I will and in fact this allows me to put a string sister plate on the back and never the chainplates hole an inch further to accommodate

[s/v Jedi]

Repairs that reinforce the loaded part of the bulkhead are only needed when the failure was caused by a construction that was too weak. In this case the damage was caused by water ingress so matching original bulkhead strength is enough. Fiberglass is nice because it prevents the bolts pulling upwards creating slots where the holes are.

A scarf joint is the way when using only wood, but when you have fiberglass, you can also butt joint and put 4” wide glass over that joint. I believe it was Mads who did this on YouTube as equal strength. He routed a 4” wide channel of 1/8” or so deep to out the fiberglass tape in so that it would become flush.

[smj]

Originally Posted by s/v Jedi

Repairs that reinforce the loaded part of the bulkhead are only needed when the failure was caused by a construction that was too weak. In this case the damage was caused by water ingress so matching original bulkhead strength is enough. Fiberglass is nice because it prevents the bolts pulling upwards creating slots where the holes are.

A scarf joint is the way when using only wood, but when you have fiberglass, you can also butt joint and put 4” wide glass over that joint. I believe it was Mads who did this on YouTube as equal strength. He routed a 4” wide channel of 1/8” or so deep to out the fiberglass tape in so that it would become flush.

A well done scarf glued in with epoxy would probably be fine without the glass, reaching the same strength as original. Or a butt joint like you said but could grind out a taper on the joint and glass tab the taper would also work fine.
I see no reason for a huge part of the bulkhead to be removed as someone stated earlier for such a small piece of rotten wood, but everyone must repair in the manner in which they feel comfortable?