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BC2316 08-22-2009 11:58 AM

Question re: Cal T-4 with rotted plywood under the deck
 
My Cal T-4 has wet and rotted plywood in the ceiling of the cabin. I cut an inspection hole through the thin fiberglass covering the bottom side of the ceiling and found the plywood comes out in shreds. I pulled enough away to expose the fiberglass of the top deck. Can the plywood be replaced from inside the cabin or does the top deck need to be removed? I'm pretty competent with home repairs but I'm new to boat repair. Any advice on the best way to proceed with this repair would be appreciated.

coldsteel 09-14-2009 02:55 PM

Have not done that repair
 
It is good to hear from a fellow T4 owner. I am repairing my 72 Cal T4 but my deck is in good shape. I did have to do some repair around the hatch where the plywood was coming away from the fiberglass deck but that only took some sealant and a few clamps. Where are you located? I am in Ewa Beach, HI with my boat at Rainbow Bay Marina Pearl Harbor.

Bonden 11-07-2009 11:40 AM

Quote:

Originally Posted by BC2316 (Post 515857)
My Cal T-4 has wet and rotted plywood in the ceiling of the cabin. I cut an inspection hole through the thin fiberglass covering the bottom side of the ceiling and found the plywood comes out in shreds. I pulled enough away to expose the fiberglass of the top deck. Can the plywood be replaced from inside the cabin or does the top deck need to be removed? I'm pretty competent with home repairs but I'm new to boat repair. Any advice on the best way to proceed with this repair would be appreciated.

On other boats I've repaired it seemed better to leave the outer deck FG laminations intact, especially if nonskid or other molded-in features are involved. This way the job is inside, from the weather, and any final roughness is covered by the headliner:

- remove the inner FG lamination with a knife and/or a knee grinder (4.5" or 5") with 36 grit sanding disk and/or whatever from any wet/rotted core - keep going until you uncover an inch or so of good core all around the patch area

- remove damaged core material, finally using grinder to lightly scuff the underside of the outer deck FG (careful not to reduce its thickness much, or just add a layer of 6 or 10 oz cloth if thinnning did occur of if needed in any case (like just for peace of mind), and use the sander/grinder to add a 5:1 scarph all around the edges of the existing core material

- then use the grinder, to scarf (5:1) the edges of the new ply core material until it fits (lots of grind and fit, grind and fit here),

- core patch is 'clamped' in place with numerous 'bent-in-place clamp legs' from the floor or whatever structure is under the patch, legs maybe about 1/2" x 1.5" in cross-section (depending on wood type and length needed), custom cut to length to be a 'bend-in-fit' (to apply upward pressue on the patched in core matrerial - be sure to dry-fit all this until its perfect prior to actually applying epoxy goop, and use drop cloths/masking material under the patch and clamp legs to catch the goop that squeezes out)

- measue a scrap of the old laminate or otherwise determine the total thickness of glass needed for inner laminate

- then scarf (15:1) in the new interior FG laminations using epoxy.


Ask more questions if you like - I've done several of these.

Waltthesalt 11-07-2009 04:50 PM

I've seen a number of published articles on doing this. They all did it from the top. Cuttiing out the fiberglass section, replacing the wood then fiberglassing the panel you removed back in. I'll look for the refreences. The issue with doing it from the inside is aparenty doing the glassing upside down. I think that the Gougeon handbook address this and the bevel needed to proplerly glass in the joint.

Waltthesalt 11-13-2009 07:04 PM

I found my copy of the technical reference on this job. It's in the the WEST System booklet 002-550 "Fiberglass Boat and Repair & Maintenence" . I think you'll find it in PDF on thier website. Good luck

Waltthesalt 11-14-2009 01:23 PM

One more refreence: Google EPOXYWORKS the Gougeon Brothers magazine. Number 19 (Spring 02) has a fairly detailed article on a balsa cored deck replacement. There may be others. The owner chose to geplace the upper skin with fiberglass mat and cloth. The more common approach I think is to carefully cut out the upper skin and glass it back in.

laHolland 02-28-2010 06:55 PM

Hi, Did you decide on a repair method for your wet deck issue? I am facing a similar problem with my Cal 27, though the plywood isn't rotted yet. I am loath to cut the outer deck surface, though everyone is saying it's much easier that way.

Bonden 03-02-2010 09:58 AM

Quote:

Originally Posted by laHolland (Post 575241)
...I am loath to cut the outer deck surface, though everyone is saying it's much easier that way.

Not everyone. Above I outlined the advantages I've personally experienced in doing it from the interior, although it does depend heavily on the location of the rot and ease of access from the interior. I've done them both ways (and both ways on the same boat) and unless its hard to get to the inside area, the interior approach has much to offer the "regular guy" working on his boat in the slip, without a travel lift, without an inside shop location and without a full selection of professional-grade tools and professional advice and experience at his disposal.

Even if the bad core extends to the very forepeak or over bulkheads and so on, I'd still approach the bigger, flat and easy-to-access areas from the interior, and then only have to tear up the molded exterior part from the exterior in smaller sections, minimizing the structural and fairing aspects that are so much more difficult in large sections for amateurs.

Getting a good, calculated scarph angle where the repair joins the original laminations is one main key to the structural glass aspect.

Either way, just starting on it is often the most difficult part, especially since you can get advice here. Doing a small "test area" from start to finish, say 6" or 8" square, in an easy-to-access portion of the job, will be good learning experience without big trouble if things go wrong, and will let you know what you are in for, help develop a proceedure list, tool and materials checklist, reveal other issues, and so on.

We had 10" of wind-driven tidal-flood saltwater in our house last November - putting the boat on the back burner, if not off the stove entirely - and I'm just finishing our home repairs and improvements. I'm looking forward to getting back to work on the boat...

Bonden 03-02-2010 03:16 PM

Just noticed this useful reference from West System when researching another topic, and see it’s the same one mentioned by Waltthesalt, above:

http://www.westsystem.com/ss/assets/...aintenance.pdf

As he said, it discusses the various procedures for core repair. Also, it goes into the advantages of repairing from the interior and exterior (middle of p33). Pretty much what I said earlier about not disturbing molded features like nonskid, if another method is reasonably feasible.

If you read this pdf, core repair and all related tasks should become very clear.


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