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-   -   Deck Core replacement (http://www.sailnet.com/forums/gear-maintenance/50299-deck-core-replacement.html)

zz4gta 01-07-2009 12:16 PM

Deck Core replacement
 
I plan to start this task next month on my boat. I'll be using balsa core and wanted to get some opinions on bedding hardware and using a liner as outlined in another post here on sailnet. I just want to make sure that a skim layer of FG is not required on the inside for strength. I plan to do the re-core from the inside leaving the outter decks untouched. (I know, I know).

I'll keep updating this post with pictures and progress. Hopefully I can have the repair done with 100sq ft of balsa, and minimal down time.

Here are the steps I have outlined
1. drop the mast and remove hardware
2. strip insides of anything important, vests, gear, etc.
3. start from the companionway and cut sections of deck out working my up to the bow.
4. plug all hardware holes to keep out rainwater, and allow a week to dry.
5. begin cutting and expoxying new balsa in place, same order as it was removed.
6. epoxy over all exposed balsa to seal it. Let it cure.
7. drill new holes and install hardware.
8. cut and install liner.
9. put the stick up.

WAAAY easier said than done. I'm not looking forward to this.

chucklesR 01-07-2009 01:08 PM

Cored decks, like cored doors get their stiffness from the outside laminate layers, not layer.
You'll want to put at least one layer of FG over the core.

Imagine a door to your home with just the outer face and some cardboard waffles on the back. Imagine how fast it would warp out of true.

Another point, check your epoxy's curing temp's for min/max. Gooey don't work.

jbondy 01-07-2009 01:26 PM

How do you intend to hold the balsa in place from underneath while the epoxy cures? I experienced sagging. Some sort of bracing is necessary. As chucklesR said, you absolutely do need the inside layer of fiberglass. You can save the inside skin, grind away any rotten balsa stuck to it and glue it back in place. Then you'd only need to glass the seams. But holding the layers in place will be your biggest challenge. As steated in the earlier threads, the one lesson, main lesson, I painfully learned was: do it from the top. I know, you know. Once the epoxy was applied, I didn't want to stop and grind it all away after I figured out how to brace, so I ended up putting screws from the top into my core to hold it in place after the sagging couldn't be stopped due to insufficient bracing from below. That left me with holes to fill from above anyway. Think it through. Folks have been successful doing this from below, but not me.

Good luck.

Maine Sail 01-07-2009 01:30 PM

Quote:

Originally Posted by zz4gta (Post 428370)
I plan to start this task next month on my boat. I'll be using balsa core and wanted to get some opinions on bedding hardware and using a liner as outlined in another post here on sailnet. I just want to make sure that a skim layer of FG is not required on the inside for strength. I plan to do the re-core from the inside leaving the outter decks untouched. (I know, I know).

I'll keep updating this post with pictures and progress. Hopefully I can have the repair done with 100sq ft of balsa, and minimal down time.

Here are the steps I have outlined
1. drop the mast and remove hardware
2. strip insides of anything important, vests, gear, etc.
3. start from the companionway and cut sections of deck out working my up to the bow.
4. plug all hardware holes to keep out rainwater, and allow a week to dry.
5. begin cutting and expoxying new balsa in place, same order as it was removed.
6. epoxy over all exposed balsa to seal it. Let it cure.
7. drill new holes and install hardware.
8. cut and install liner.
9. put the stick up.

WAAAY easier said than done. I'm not looking forward to this.

You're forgetting a very important part of repair from the bottom GRAVITY! Use vacuum bagging!!! What ever the interior skin was made of lamination wise I should be put back with the same schedule.

I can assure you that without vacuum bagging this job will be harder, and come out with more gravity voids than doing it from above and repainting the decks. You make it sound so easy and I wish you luck!!

US27inKS 01-07-2009 01:33 PM

I agree with Chuck. The balsa core causes the deck to have structure much like an I-beam. Without the interior fiberglass, you've got nothing.

What has been done with success, but more work initially, is to save the interior fiberglass as a panel. Carefully cut around the area you wish to cut out, and very carefully remove the fiberglass by cutting the core out. Then you can grind off any remaining core material from your panel. Then you can replace the core. To reinstall the panel, wet out the balsa core, the apply thickened epoxy to the panel. Prop the panel in place making sure it has good adhesion all the way across. Then fix the cut lines and you're done.

Or you can do what I did. Hold a 50 x 60 inch piece of dripping wet 18-2 biax over your head for about an hour.

Maine Sail 01-07-2009 01:33 PM

Quote:

Originally Posted by jbondy (Post 428401)
Folks have been successful doing this from below, but not me.

Good luck.

I believe folks "think" they have been successful. I have had the opportunity on a number of occasions to either dig into this work myself from above or have seen it in the shop and can assure you they were not nearly as successful as they thought they were..

US27inKS 01-07-2009 01:36 PM

Quote:

Originally Posted by Maine Sail (Post 428403)
You're forgetting a very important part of repair from the bottom GRAVITY! Use vacuum bagging!!! What ever the interior skin was made of lamination wise I should be put back with the same schedule.

I can assure you that without vacuum bagging this job will be harder, and come out with more gravity voids than doing it from above and repainting the decks. You make it sound so easy and I wish you luck!!

I tried vacuum bagging mine, with no luck. I couldn't get a good seal on the stupid thing. So I used a piece of light plywood (3/16 if I remember) and braced it in multiple places. Yes it sucked.

NOLAsailing 01-07-2009 01:37 PM

How large an area are you talking about? You mention in the post going from the companionway forward. I can't fathom doing that much core work from underneath.

zz4gta 01-07-2009 01:55 PM

Quote:

Originally Posted by NOLAsailing (Post 428410)
How large an area are you talking about? You mention in the post going from the companionway forward. I can't fathom doing that much core work from underneath.

All of it. :D

There is no paint on the deck now, just gelcoat and I'd like to keep it that way, the outter shell is in good condition and I really don't want to hack it up if I can avoid it. The inside liner is cracking severly and coming apart, mildewed and rotting.

I guess my other question (which I've asked on a Merit site) was the thickness of the core. It looks to me like 3/8" plywood, I'm assuming I could use 3/8" end grain balsa to replace this correct?

jbondy, I plan to use adjustable "hood props" that some mechanics use. Basically a telescoping pole that can be locked into place. If those don't turn out to be cost effective, then wooden dowels cut to length will have to do.

tommays 01-07-2009 02:00 PM

I can see you getting the core in place somewhat BUT i am not seeing the glass work as being that easy :eek:


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