Would you help a poor #$%^%glass sailor out?

[Peter Malcolm Jardine]

My Stepbrother has a tupperware sailboat, but a good one, a C&C 27, which he sails up on Lake Simcoe. He sold his C&C 30 when his second child was born, my nephew Mitchell, and bought this 27 knowing it was cheaper and older.

Anyway, He has a soft deck. C&C used balsa cores on their decks, sometimes ply.. but mostly balsa. In order to do a complete deck, its about 10k Canuckian, but is there any other repair less drastic that could be done? Knowing it was temporary,I was thinking maybe CPES in the balsa would work well, but... let me hear the horn of wooden plenty's opinion. He figures he can't use the boat without a significant repair, and I don't know if anything can displace the water that might be between decks

[Rocky]

I have a West flyer which describes cutting out and replacing a bad section. Why can't he do it himself?

[John Riopelle]

Hi Peter
A bout 6 years ago I lived in Windsor had a great liveaboard then anyway a 36 foot sailboat was docked beside me he had soft decks and no cash, over the years I've had a fair amount of glass experiance and a inexpensive fix for his boat was 1/4 mahog coated on sides and edges with fiberglass resin and attached to existing decks that was 6 years ago he sailed into port last summer to say hi same decks no problem.
john

[Mrleft8]

I hear having children will cause soft decks... My advice is to donate the boat to a charity for the tax write off, and find a nice woody....

[mmd]

Hi, Peter. The fix depends on where and what is the deck doing for the boat at that place. If it is a case of merely keeping the water out and a place to stand, John R's solution is fine. If, however, the rot has affected areas that are stressed, such as under sail tracks, winch mounts, mast partners, etc., then more extensive surgery is required.

Cored 'glass structures gain their strength from the seperation of the 'glass skins by the core material - the thicker the core, the greater the strength. Think of it in terms of a steel I-beam - the top and bottom of the I-beam are the strength members (FRP skins), and the web in the middle (the core material) merely holds them apart. The taller the web, the stronger the beam. Remove or weaken the web or disconnect it from the flanges (delamination of the core), and the flanges collapse upon themselves and the beam fails. With core construction FRP, weaken the core and you weaken the structure. If the core panel acts as a strength member to transfer loads from deck equipment to the hull and the strength of the stressed panel is compromised by damage to the core, the integrity of the whole structure is at risk.

If it is just the cockpit sole, for example, the only stress is the weight of the occupants, and even if it does fail, it won't doom the boat in most circumstances. Core failure under the primary winches could be a whole other matter.

Incidentally, the primary reason for balsa core failures is that when deck hardware is mounted with through bolts, quite often the installer does not seal the drilled holes, assuming that the hardware bedding will exclude water. Uh-Uh. Nope. No way. Water will get in, and once in contact with that bare balsa exposed in the drilled hole, it wicks through the structure with impunity, turning the once-rigid balsa into something that resembles wet cardboard. Even in solid wood construction, always seal drilled holes before mounting the hardware!!

[High C]

MMD, Thanks for the tip on sealing holes before putting fasteners through a deck. Would you tell me how to best go about doing that? Is it simply a matter of squirting some Gorilla glue in the hole to let the screw spread it around?

Thanks a bunch.

[mmd]

The same stuff you use to seal the end grain of the other structures of the boat. If you have built an epoxy-encapsulated boat (strip or cold mold), use epoxy. Painted boat? Use paint. The whole idea is to seal off the open grain of the freshly drilled hole.

[Mike Vogdes]

Iv'e done this repair a couple times in the past and will be doing it again this spring on my latest plastic project boat, a 1979 Watkins 27. Every couple years I buy a tired fiberglass boat to renovate, and use, while I do the work. It feeds my boating habit and I usually make a couple bucks in the end.

This Watkins has a soft fordeck on the starboard side about 6 sq ft and a weak cockpit sole. The detail you usually see in the WEST system book where you drill a number of holes in the soft spot and try to dry the affected area out doesn't work very well in real life, you can never seem to dry the area out properly, mainly because the balsa core is actually mush and all that drying isn't going to restore the integrity of the mush anyway, the best aproach is to identify the soft area and carefully cut the top laminate off and save it for rebonding after you dig out and replace the core. The key to success in this aproach is to overcut the soft area. Say your soft spot measures 18"x24" you want to make your cut say 22"x28", you then dig out the rotten material and clean and prepare the bottom laminate to recieve the new core. Balsa core is available, I think its called Baltec, but I like to use marine fir plywood to replace the rotten core, trying to do it in one piece if possible.

When its time to bond everything back in place you want to mask off the area really well then coat everything with unthickened epoxy then thicken with WEST 406 and bond all the pieces together including the outer laminate you carefully removed in the begining, I like to use sand bags to weigh the repaired area down, thats allways worked best for me, however I've seen a shop vac used from below thru a hole drilled in the bottom laminate with a piece of plastic duct taped over the outside laminate. You also want to do this job while the boat is on the hard and working off scafolding, you can't be walking on the deck while doing this job. My boat needs a paint job anyway so after fairing I'll paint the whole deck.

[JimConlin]

Repairing such a mess isn't the end of the world.
Basically, it's:
Remove deck hardware.
cut out top skin.
Excavate mushy core .
Bond in new core (foam and plywood)
Lay up new glass top skin.
Fair and paint.
install hardware, sealing the holes right this time.

I've left a lot of details out, but it's a do-able job.
I think that the Gougeons have published the definitive how-to.

[pjwalsh]

I think the best approach on this is to do it right - excavate the mush, replace the core and relaminate from above if possible.

I used to be the deck man at a production builder and the technique we used for fastening throughbolted winches and such in cored areas was to drill and oversized hole and insert a fiberglass tube with the desired ID. We used G10 epoxy/glass tubing (available in many diameters from mcmaster carr), and boded with thickened epoxy.

This guarantees good sealing and prevents crushing of the core when the hardware is loaded heavily or by overtightening of fasteners. All the hardware was bolted - no screws. I do not think merely coating the inside of a hole with epoxy is adequate - the coating is so thin it will likely crack and eventually admit water.

[mmd]

I agree with you completely, pjwalsh. Unfortunately, what you describe is somewhat labour-intensive, so many individuals/companies are reluctant to go to that level of detail. Definitely the quality way to go, though. If not done this way, a covering of epoxy or some other sealant is certainly better than nothing, and is pretty quick and easy to apply.

[swingking]

Most C&C's also have cored hulls. If it did, I would have this checked for rot before I invested alot in this boat.

It is best to recore.
This is the best site I've found on on recoring decks.
http://www.triton381.com/recore.html

Rotdoctor had some stuff about wet cores and CPES:
http://www.rotdoctor.com/L/BoatL/Bqa.html

I understand if the cores are not mush some will
dry core (This is the hard part), drill holes and
apply epoxy to connect top and bottom glass.

[pjwalsh]

mmd,

I agree with you too, certainly a coating with epoxy or paint is fine in a situation where the deck material is sturdy as in plywood and such. In end grain balsa though it is not hard to imagine crushing the core with an overtightened bolt or by the sheet load on a deck mounted winch.

It was certainly more labor intensive than not sealing at all, but I was able to mount all the major deck hardware on a 37' sailboat in about two days. Of course the decks were not attached to the boat yet - access was much easier, and I did not need to worry about dripping epoxy on the interior.

[JimConlin]

The other alternative in treating through fastenings for heavily loaded hardware in a cored deck is to drill large or excavate the core around the hole, cast solid epoxy plugs and re-drill. In any case, good bedding and backing plates are essential.

[WB content] The same applies to light wood sandwich construction.

[thechemist]

Excavating the mush is best, and that means removing the top skin. Drilling holes and using epoxy plugs to reconnect the top and bottom skins is a viable alternative, although you need MANY small connections.......think quarter-inch holes on one-inch centers, and since you drilled a hole in the top skin you need that epoxy plug flared-out on top to have some attachment area to the top skin.

Drying a damp balsa core is possible, using vacuum-blanket equipment to vacuum-dry it, having first drilled many holes. Since evaporating water freezes the remainder, you need an electric blanket inside the vacuum-blanket just to keep the core at ambient temperature so the vacuum pump can evaporate the water in a reasonable time [a few days as opposed to many weeks].

Vacuum-pumps that depend on oil for lubrication will be ruined in short order by the evaporated water that will condense in the oil, just as your car engine will be ruined when a coolant leak gets into the crankcase oil. A shop-vac does not generate enough of a vacuum to evaporate water in any reasonable time. There are rotary-vane pumps that have no oil, made by GAST and others, that pump to 25 inches [30 being full vacuum] and are adequate for this purpose. Grainger and other industrial distributors have them available.

[Buddy Sharpton]

Whoa for a minute. I own boats, with both balsa and ply cored decks. The balsa has some good news. As it is all end grain, water does not migrate from the area of the hardware mounting holes near as fast or far as ply. Where is the problem? Likely you've got soft decks on the foredeck forward of the house, back of the hatch, mid way from the toerails and the corner of the hatch along the logest unsupported span of the boat? Reinforce from beneath with nice pretty 2' x 1' mahogany or teak "beams" well secured to epoxy implants. Not a perfect repair, but usually perfectly adequate and a great return for the time invested, and cosmetically successful. Amateur ondeck repairs, while structurally sound, usually look like a patched up area.
This implant is how you should secure or resecure all hardware in a balsa or ply cored deck.
Drill that 1/4" hole about 3/*" Take an allen wrench with the long side chucked in your drill, and break away and vacuum out about a 1/1/2" circle. Tape the underside of the hole and use a caulking tube, or "pastry" pouch with an epoxy resin and chopped glass reinforced putty/mush. Then redrill the 1/4" hole. This biscuit implant won't compress or leak water into the core. Really first glass is to under drill the hole and tap for your fastener. Really compulsive is to epoxy the fastener in the threads. You can always heat the bolt head with a soldering gun to remove it.

I wouldn't jump to the conclusion of really heavy repairs. Are your chainplates alright? This is another problem area, but usually water damage here is to the wooden bulkheads. There you patch in new good wood if beyond the immediate area of the bolt holes.

[mmd]

As it (balsa - mm) is all end grain, water does not migrate from the area of the hardware mounting holes near as fast or far as ply. Agreed in principle, Buddy, but particularly in newer construction the balsa has been sliced almost through in either one direction or two to facilitate it's bending around curves in the structure. In all but the best controlled shops, these cuts are not filled with resin or bonding compound and form channels that the moisture can wick along. Also, in colder climates, as the moisture in the admittely small area saturated with water freezes, it expands and delaminates the core from the skin in the areas adjacent to the wet area, creating additional pathways for moisture to travel within the laminate structure as soon as it thaws.

It would be great if all cored FRP boat construction anticipated these types of problems and created proper substrates for the mounting of hardware, but that level of detailed design, tooling, and construction is very expensive and is commonly seen only in the very best of boats. Your suggestion of retro-fitting FRP "bisquits" is very elegant, but it must take a pretty strong hand to hold the drill in place when cutting ply. Nice results, though. I also agree with you that threading the insert is a bit too anal.

[Buddy Sharpton]

The allen wrench "tool" works best, actually quite easily in Contour Core foam or Aircell, pretty easily in balsa, especially wet balsa, or really rotted ply. I suppose fresh ply would need a series of gradually longer, sharpened tools.

[garland reese]

THE FIBERGLASS BOAT REPAIR MANUAL, by
Allan H. Vaitses (International Marine), has a pretty good section on this type of repair.

[JimConlin]

I haven't done this, so this is idle speculation.
For the major hardware fastenings(winches, clutches, mooring cleats) where you really want a good annulus of hard material in the core , how about casting the plug before laying up the top skin? Cutting the hole is easier and you'd get much better quality control on the plug.

So, the sequence would be something like this:
...
Bond core material to lower skin
mark locations of major hardware
bore 1"+ holes through core material with hole saw or spade bit.
Seal any hole in the lower skin with duct tape
Cast plugs of filled epoxy in the bores and render them flush with a belt sander
Lay up top skin
...