Soggy Core Blues

[BobT]

Re-bed your deck hardware, don't put it off. Beg or borrow a moisture meter.This is a view of the cabin ceiling where the halyard winch and rope clutches were mounted. After cutting out the inner skin, of course. And then one of what the winch mount looked like from above, i.e. not much of a bedding job. Even the hatch track screws were leaking.

So, how 'bout opinions on new core material to be patched in. Balsa as before and properly potting the fasteners? Any point is using foam core? I'm set up for West System.

Thanks

 

[sailingdog]

BobT—

I generally recommend fixing a core repair like this from above, rather than below. Gravity is working against you when you try doing the repair from below. Also, clean up is much more difficult, as is getting the core and inner skin properly bonded to the existing skin.

But, since you're committed to doing it from the bottom... I'd recommend using the same core material as the rest of the deck, unless you're re-doing the entire cabintop. If you can vacuum bag the area to be repaired, it will help prevent voids from occurring, and help ensure the area laminates properly.

I would recommend using a heavy layup of solid glass in the areas where deck hardware will be attached, which will prevent any future recurrence of the core delamination.

 

[Manny]

Ditto what Sailingdog posted but another option would be to use aluminum plates at the deck hardware locations. You can drill and tap in the hardware.

Manny

 

[Ross]

Been there and have done that. I am overwhelmingly commited to Corecell foam or Airex core. Bed it in corebond. Use vinylester resin and chopped strand mat for the first ply over the core then woven cloth and csm alternately for the schedule you want. Roll the glass fabric onto a cardboard tube wet the area very thoroughly with resin slowly unroll the fabric and with a paint roller full of resin press it into place. When it is completely filled and in place roll out the bubbles with a grooved roller and apply the next ply. I worked alone but if you have a helper you will be better off. When you have everything repaired and you are ready to mount your hardware, drill the bolt holes and from the underside with a hole saw remove a plug and replace it with solid durable wood or glass filled resin. This will take the compression loads from the bolts. You will still need substantial backing plates.

 

[sailingdog]

One problem with glassing in aluminum is the possibility of water intrusion and how that would allow the stainless steel fasteners to attack the aluminum. If you're going to use aluminum, do so as backing plates, not sealed within the deck laminate.

I would also recommend you read Maine Sail's article on bedding deck hardware and sealing the core properly.

 

[sailingdog]

I wouldn't use vinylester resin for a structural repair of this magnitude. This type of repair relies on the secondary bonding (adhesive) characteristics of the resin, and epoxy resins have much higher secondary bonding strength.

Been there and have done that. I am overwhelmingly commited to Corecell foam or Airex core. Bed it in corebond. Use vinylester resin and chopped strand mat for the first ply over the core then woven cloth and csm alternately for the schedule you want. Roll the glass fabric onto a cardboard tube wet the area very thoroughly with resin slowly unroll the fabric and with a paint roller full of resin press it into place. When it is completely filled and in place roll out the bubbles with a grooved roller and apply the next ply. I worked alone but if you have a helper you will be better off. When you have everything repaired and you are ready to mount your hardware, drill the bolt holes and from the underside with a hole saw remove a plug and replace it with solid durable wood or glass filled resin. This will take the compression loads from the bolts. You will still need substantial backing plates.

 

[BobT]

Thanks folks. I believe I will be able to vacuum bag the repair area(s). The spots that worry me most are the jib winch locations on the coaming. They meter very soggy as well. Getting to the back side of them will be very tight. I'd really rather not saw up my topsides, but it would be easier... I have a bunch of other gelcoat chips to repair and already got a quart kit from minicraft...hmmm have to think about that...

 

[sailingdog]

BTW, repairing the core from the topsides also goes much faster than trying to repair it from below. The time savings alone could compensate for the fact that you have to re-finish the deck where the repair was done.

 

[Ross]

If you have never worked over head with wallpaper or fiberglass I advise great caution. Working on the inside of a boat, overhead, with fiberglass and resin is much more demanding than wallpapering the ceiling in a small bathroom. I think with vacuum bagging the catalized resin is drawn into the glass fabric by the vacuum. If that is correct then it won't be terribly messy but it won't be a picnic either. Holding all of those dry layers in place would be easy on a table but not so on the ceiling.

 

[sailingdog]

A great analogy, and in the case of fiberglassing, the stuff is sticky on both sides...not just the back.

If you have never worked over head with wallpaper or fiberglass I advise great caution. Working on the inside of a boat, overhead, with fiberglass and resin is much more demanding than wallpapering the ceiling in a small bathroom. I think with vacuum bagging the catalized resin is drawn into the glass fabric by the vacuum. If that is correct then it won't be terribly messy but it won't be a picnic either. Holding all of those dry layers in place would be easy on a table but not so on the ceiling.

 

[Ross]

A great analogy, and in the case of fiberglassing, the stuff is sticky on both sides...not just the back.

If you are working with Chopped strand mat and ester resin and the mat gets away from you, it stretches and pulls and comes apart and all you can do is get clear and clean up the mess.

 

[sailingdog]

Been there... done that... if you're gonna do this, you need to wear the tyvek bunny suite with the hood, and a full face respirator mask....

If you are working with Chopped strand mat and ester resin and the mat gets away from you, it stretches and pulls and comes apart and all you can do is get clear and clean up the mess.

 

[BobT]

All this forethought is good prep! I was able to get the inner skin off in a few large sections. I plan on putting the piece up again as the top (or in this case, bottom layer) to avoid the sagging fabric syndrome. I'll still use a saturated layer behind the old skin.

I'll do a few small gel coat repairs to see how it handles before I rip up the coamings. If there is any reasonable access under them, I can be a little less cosmetic with a core repair there. There are spiderweb gelcoat cracks I wouldn't mind losing, but that's a lot of worrywork.

 

[Ross]

A saturated layer of what? First you must bond the core to the underside of the deck and then you must bond the old inside skin to the new core then you must maintain the contact and position until the resins cure.

 

[sailingdog]

I hope he's planning on putting new glass on the underside and using the old skins as a outer layer, to help the new layers of glass bond to the core, while providing a non-sticky surface to put braces against.

A saturated layer of what? First you must bond the core to the underside of the deck and then you must bond the old inside skin to the new core then you must maintain the contact and position until the resins cure.

 

[Ross]

I hope he's planning on putting new glass on the underside and using the old skins as a outer layer, to help the new layers of glass bond to the core, while providing a non-sticky surface to put braces against.

I have never applied new glass to an old surface. I always grind the existing surface clean and wipe it with acetone before I do anything else. From the pictures posted there is much prep to be done before anything can go back. The first tool that I bought when I started my rebuild was a 4 1/2 inch right angle grinder with a sanding disk kit. I think I must have used a thousand 24 grit disks before I was finished. I had a case of tyvek suits and bought disposable respirators by the carton. Safety googles by the dozen(they get scratched). A shop vac is essential.

 

[sailingdog]

I generally recommend cleaning the surface before grinding, so you don't accidentally grind contaminants into the surface when grinding.

BTW, I highly recommend using a full-face respirator, rather than disposable masks and goggles. This is for several reasons. First, disposable masks can let as much as 25% or so unfiltered air by, which I think is a really bad idea. Second, a full face mask respirator will be more comfortable in most conditions and far less likely to fog up. BTW, the full-face respirators have disposable face visor protectors, so the visor doesn't get all scratched up.

Also, I think that Interlux Fiberglass Prep Wash is far better than plain acetone at cleaning the surface.

I have never applied new glass to an old surface. I always grind the existing surface clean and wipe it with acetone before I do anything else. From the pictures posted there is much prep to be done before anything can go back. The first tool that I bought when I started my rebuild was a 4 1/2 inch right angle grinder with a sanding disk kit. I think I must have used a thousand 24 grit disks before I was finished. I had a case of tyvek suits and bought disposable respirators by the carton. Safety googles by the dozen(they get scratched). A shop vac is essential.

 

[BobT]

Agreed on all points:

Remove old core, sand to fresh surface, clean with solvent.
Epoxy new core material to the underside, a new woven layer behind the core, and the old skin up against it all.

Access is such that it could be held up with spring sticks and a plastic wrapped piece of 1/4" plywood. I'll consider vacuum bagging it, but that's a pain upside down and getting a good seal on the surrounding glass will be a job for butyl tape since it's laid up woven glass with no gelcoat. Mr. Gravity is not working with me here.
The epoxy can be thickened to control dripping out of the layup. That's one thing I'm not sure can be done with the normal resins used on glass.

I've got some smaller spots around the chainplates to work out the procedure and hardener speed.
Thanks for the collective wisdom. I'll report...
I'm thinking that this is still less annoying than doing new gelcoat and nonskid on the topside!

 

[Ross]

There is one rule that may be depended on in boat repairs; each situation will present a new and different set of problems and requirements. There is no way to wash away old rotten core residue and no way to effectively grind away silicone residue. Each must be handled in the best manner known.

 

[dvideohd]

Ross and Sailingdog really have some good points... Assuming you get a handle on the "particular situation" you are in - then the MAIN question is how you handle safety and cleanup. Even if you do a PERFECT job - and you leave toxic materials about - or breath some in - then it WAS NOT WORTH DOING in the first place...

So the plan gets really split into three parts...
1 - how to do it.. (as said, each situation is different....)
2 - do you have a GOOD safety plan - for you and the process...
3 - are you handling the materials/residue effectively and safely for long term cleanup?

I would not want a pile of fiberglass shavings & dust on my boat or in my yard. So the vacuum is a MAJOR part of the thinking..

It's a tough job you are attempting....

--jerry

***************