Deck recoring

[Scott Won]

I am currently recoring and deck from the bottom for a client.

The deck on this particular boat was entirely wet (balsa). At almost 40 years old some areas did not even have rotten core left.

There are several issues that I would like to speak to for those of you that have cored boats. Particularly if you are thinking of repairing yourself.

First, All boats need to have there fittings sealed. I have seen several boats that I am positive leaked from the first day the deck got wet. My advise would to make it a chore to every year rebed your fittings that pass through the core. I would suggest that when doing so the core be treated with S1 epoxy this is a very thin penetrating epoxy that will help to seal the balsa. Then use your favorite sealer for the bedding and threads.

Second, there is nothing wrong with balsa it has a great compressive resitance and if kept dry will stay strong and dry. If you are replacing a section of core use the same material otherwise you will have inconsistant stresses in the deck that can focus stress to that area.

Third, If you are going to go ahead and recore a section I would avoid the cut and replace method. The strength in FRP is in the glass. if the glass is cut the strength in the skin is lost. Glassing the deck back on is relying on the shear strength of the adhesive. Moreover, the new core material will not be the same texture and the old and the skin. Your deck will have voids. With hand layed hulls there are voids and channels in the core material that allow moisture to travel. Sometime quite a long way.

Fourth, If you have a removeable headliner or no headliner coring from the bottom will alow you to keep your deck in good repair and you will be cutting out the (usually) thinner skin.

Finally, my most important comment is that if you are going to do a repair on a deck the best way is to vaccum bag regardless of from the top or bottom. This is the bones of your boat. The process is extreemly prep heavy and frustrating. If your going to aim for good enough you won't even get close. If you think you can blast through it, you will be starting over.

[mitiempo]

Originally Posted by Scott Won

I am currently recoring and deck from the bottom for a client.

First, All boats need to have there fittings sealed. I have seen several boats that I am positive leaked from the first day the deck got wet. My advise would to make it a chore to every year rebed your fittings that pass through the core. I would suggest that when doing so the core be treated with S1 epoxy this is a very thin penetrating epoxy that will help to seal the balsa. Then use your favorite sealer for the bedding and threads.

Every year? Why not just do it right. The core around my original deck fittings is still dry after 34 years. This link shows how to re-bed fittings properly with butyl, the same bedding used on my boat and all other CS boats. Re-Bedding Deck Hardware Photo Gallery by Compass Marine at pbase.com

On a major recore I don't think doing it from below works - at least for any but an expert. Top access makes the whole job easier and no mess below. Vacuum bagging isn't necessary as you can weight the core down until it cures. I agree the core should be the same as the original and balsa is the best core to use. Epoxy should be the resin of choice.

[mitiempo]

Clock here and see how a master recores a deck. Northern Yacht Restoration |

[Scott Won]

My appologies about the rebedding i ment a few a year till the boat is done. Not everyone can do all of the fittings there is the issue of sailing as well. But a couple at a time can fit in nicely every once and a while

Weighting from the top does not allow for the evacuation of the air from the sandwich. Vaccum bagging with an infusion system does. Regardless of top or bottom method. When infusing the fabric is put up dry the bag is sealed, the resin is infused, drawn by the a vaccum. The air is evacuated and replaced by the resin. If there are gaps in the core material from bending around the shape of the hull they are as well filled. Bagging additionally helps to get the resin/glass ratio closer to optimum. Hand layups can have significantly more resin than desireable.
You correct with respect to bagging from the bottom it is more difficult and requires special equipment. I've repaired several decks now and the reason for posting this thread was to inform others of the nessecity for preventative maintainence of their decks. Cored boats have been around for 50 years ish which means that there are a lot of boats that have issues with regard to the core. Although many boat fittings are bedded properly after 20 years one can expect leaks to occur simply from time and use.

Thanks for adding the leak with the butyl I like this method as well.

[tommays]

Squeege works to

It would be interesting to see pictures of how you get all the cloth in place get a good vacuum and a realize and infusion of resin in the confines of a fordeck you can just reach into ?

[Scott Won]

Getting into the foredeck to work is awfull. There is a lot of cursing and brusing.
When we cut out the glass we left a few inches of the bottom glass to glass over and dug the core out. this also left us the room needed to attach the bag to the deck. When the glass goes up you can use SS staples to hang the fabric in place on the core material.

The photo with the section is there a bottom layer of glass and resin? If so looks great. Was that hand layed?

One of the advantages of infusion is that were able to lay up sections that are 12' long multi layer in one go.

I'll get some photo's up later. There still on the camera.

[tommays]

All hand layed with the glass wetted out in 24" sections in a paint roller tray and then placed and Squeege out the air and excess resin

Biggest issue i see upside down in a bad place is being assured of good resin flow on a one off repiar with every boat being a bit different

On the other hand it seems to be the way to go when i see people doing it outside the boat on keel sump repiars were you can insure the resin flow and see what is going on

[Scott Won]

Gravity has little effect on the flow of resin as the negative pressure of the environment inside the bag pulls evenly throughout the area. When the resin is introduced into the bag it is at the lowest pressure. The pressure is still negative during the infusion stage. once all the resin is infused a gate is closed and the vaccum is held till the resin cures at 20 inchHG. We are laying up 50" wide triaxial stichmat 2 layers and 0-90 biax all in one shot. The set up is like yours core first then glass.

[kpgraci]

I am curious how to recore a rounded area, like on a cabin top. I have a soft spot just to the side of the mast step and it extends down the cruve on the side and front...so there are really 2 different curves to deal with. I think cutting kerfs in the bulsa, and I assume these voids need filled with resin. Sounds like it could be a mess.

[Scott Won]

It's A mess. Wear old cloths tyvek suit and hat.
the balsa has a scrim on one side to allow it to open and take curves you can cut it into smaller pieces to take a convex or concave surface. When placing in a convave face fill between the blocks with thickened resin to take up the space. convex face you can do after the core is stuck. Cover everything with something.