Replacing rotted deck balsa core

[boatbum]

Some may have followed on other places a project I have going. I know, shame on me I did not start here.
It is an owner thread and there were many threads on the topic so I was sorta roped in.

ANYWAY-

I have been tearing down the foredeck from the inside and replacing the core with coosa board and thickened epoxy. I have not removed the bow pulpit since I was afraid of being able to maintain the foredeck shape thus preventing re-installation of the pulpit.

We found out we had to do this when I examined the windlass and saw it had turned into a rust ball. I found that because a drip occurred in the vberth.

And so it goes.

The windlass 1400 bucks to replace the cases otherwise fine and waiting to go back in;

So here are some photos of the work in progress. First we have the bow area minus the windlass, and chain pipe to left with the two foot switches also removed;

The anchor locker had to be cleaned and painted except for the ceiling to make it habitable.

A platform was added over the chain/line divider so I could lay on my back to work on this.
But if you look at this one you can get an appreciation for how far balsa core will deteriorate.

The area under the windlass is clean and prepped for the coosa installation with thickened West System. Using the silica to thicken it.

The collapsible frame that I use to squeeze the coosa into place with over night.

The current progress of removal which will come all the way back to the line made with the multi tool.

So that's where it is at this point. I have to find a way to mix up some thickened epoxy and get it into a throw away caulk tube so I can jam some of this goo up into the void I cannot fill with coosa.
Today I experienced a good exotherm session with epoxy and it never made it out of the caulk gun.

 

[jtybt15]

The best thing about epoxy is that you can get the slow cure type. Fast cure, or any epoxy that cure fast, becomes more brittle after it fully cures. Adding thickner hastens cure time just as mixing/storing in large quantities. This stuff you probably already learned but it's info for beginners.

Most times when epoxying something, I'll spread unthickned epoxy on the contact surfaces and give it a while to soak in. Slow cure epoxy allows for this. Remove as much surface epoxy before adding the thickened epoxy so it won't dilute it.

A technique I've used using plywood is using 3 3/8" layers of plywood, fitted in like a jigsaw puzzle, making sure each layers seams don't line up with the next layer. That way you should be able to get full coverage with the coosa.

Another technique when using plywood, Drill or use existing holes in the top or outside skin of fiberglqass. Using short screws you'll be able to pull the plywood evenly up against to outer skin. The next lower layer, drill larger diameter holes and slightly longer screws (drilled thru the first layer of plywood) to pull the next layer of plywood up. 3 layers of 3/8" gives you the 3/4" necessary for strength.

This may not work with coosa.

 

[boatbum]

Hey Charlie thanks. The frame I have is working really well so far. I get a reasonably controlled squish that does not press out all of the epoxy. Yes, I am using the slow cure. I think if the S.O. works with me on the clean up side I can get this into a tube etc. to push it into the pinch point around the perimeter. Once that is done the coosa will slide in and mate up good with a little around the edge.
I am going to give the caulk tubes one more try. If they do not work out I will work small batches and push in double layers of 3/8 to fill up the lip I left. I left the lip around the perimeter so that I had something convenient to glass over when the coosa is up. I am replacing 3/4 balsa with two layers of 3/8 blue water 26.

The notion here is to avoid disturbing the deck surface as much as possible. When the pulpit comes off I may delve into finish and paint but I really want to avoid it up to that point.

When it comes to the layer of glass after all the coosa is up I may use a slightly thickened brew to skim the coosa and then roll fully wet glass over it from a tube I roll it up onto after wetting.

 

[jtybt15]

Yeah, tuff working with anything upside down.

 

[boatbum]

I can pretty much guarantee that if they tried this from the top down without adding a layer of glass on the bottom, that a full scale debacle would have ensued.
The lower laminate is maybe a 12oz with mat over the balsa and by itself cannot support much weight.

 

[boatbum]

This project has been eye opening. MONTHS ago, I sealed up all of the water entry points on the deck. The weather has been relatively dry as well. Today I pulled down the last of the rotten core on the port side. I sank the multi tool into the core and water was dripping out with every slice. Amazing that it was still that wet after all of that time.
Eventually I found good solid balsa to key into with the coosa so things are looking good as far as the permanent fix goes. Once I have the two layers of coosa up I'll get into rolling out wet glass. I have 12 oz biaxial with a mat sewn into it. A couple of layers of that should stiffen things up good.
The deck is already many times stronger than it was before starting.

 

[boatbum]

So now I have two layers of 3/8 coosa up and I am installing another layer four feet wide centered. Next up will be a layer of 12 oz biaxial with mat.

I need to install some sort of material to flatten up the surface the windlass will mate to. Any ideas?

 

[jtybt15]

Will everything be on the inside so no texturing is needed??

About the stiffest wood, used as a backing plate, would be Oriented Strand Board(OSB). Then using a thin non stick material like HDPE and then a smear of silicone grease which wouldn't interfere with setting up of any 2 part resin/hardener, and ensure non stick.

Probably the hardest thing would be trying to keep from trapping bubbles. One way is to add more in the center so it squishes out evenly as things are brought together.

Now, if we're not on the same wavelength, my explanation might get an X rating

 

[boatbum]

Charlie that is pretty much what I was thinking. I still have to work out how much of a spacer between the windlass and deck I will need. Once installed I'd redrill the mounting holes. Originally there was a 1/2 or 5/8 plywood ring in between the deck and windlass. When the windlass came down it crumbled.
One person has recommended using this approach but on the top side. Then remove the manufactured plate and sand/fill as appropriate before installing it. However, if you look at the second photo that is not an option given the pulpit is still in place.
I could take the top side base plate of the windlass, line it with wax paper/saran wrap as well as the deck above and squish it into place. Once hardened I could take it down and fil/fair/sand until it fits well.
Alternatively I was thinking progressively wider strips of overlapping glass running down the center line followed by sanding. I'd use a small square to check the flatness. I'd still like to have some other material in between the windlass and deck to act as a cushion.

 

[pdecat]

Looks like very good work in a difficult position. But what is coosa??

 

[boatbum]

Bruce that would be Blue Water 26 Coosa Board. It's darn easy to work with. Just make sure you wear a mask when cutting or sanding it into shape.

http://www.coosacomposites.com/bluewater.htm