Hey Charlie Jones ... (or anyone!)

[Frank Hagan]

Question has come up on the Trailer Sailor West Wight Potter forum regarding use of thickened epoxy in balsa cored decks. The practice of drilling out an oversized hole, then drilling the right sized hole to mount hardware is being discussed. Some people have heard you need to chip away some of the balsa between the skin of glass and resin to prevent the plug from pulling out, and others have said they brush the sides of the hole with thinned or unthickened epoxy so the thickened epoxy will adhere.

I've never had a problem getting thickened epoxy to adhere to wood, and I suspect brushing the sides with thinned or unthickened epoxy has little practical use. I also suspect the "skin" of glass and resin on each side of the hole probably provides enough strength so that the plug would not come out anyway. But since epoxy is so forgiving of us amatures, it could be that my experience has been one of luck rather than expertise. So I thought I'd ask an expert!

(Actually, I'm in the "drill the darn hole the right size, use bedding compound and a nice washer underneath" camp rather than going to all this oversized hole trouble ... but then I'm a KISS kind of guy).

[Greg Luckett]

Frank,

On the Laguna I am restoring there is rot in the coring almost everywhere a hole was, such as stanchions, or wire, or the mast tabernacle, for example. When installed at the factory it was just drilled and not sealed around the hole in cross section. To repair I am oversizing the holes, removing coring, then filling with thickened epoxy, and then redrilling the correct size hole. I did this on tillers and rudders before and it worked great and should be the cure to the core rot problems.

Greg.

[Jim Stumpf]

As I understand it, it is considered good practice to brush unthickened epoxy on porus surfaces whenever you use epoxy to keep the wood from wicking the epoxy out of your thickened putty causing a glue starved bond or joint.

Jim

[Greg Luckett]

Using just the epoxy should penetrate unsealed wood better than the thickened epoxy does. I forgot to mention doing that, which I also do, except when the area is very small, say under the size of a quarter and hard to get into. The thickened epoxy is a barrier to water when the hole is oversized, then the actual through hole is drilled only through the hardened epoxy.

Greg.

[Charlie Jones]

Jim has it exactly correct. Coating with straight epoxy first allows any wood or coring to soak up some epoxy, thus preventing a starved joint. You should do this anytime you are gluing or filling. I always precoat, wait a bit, recoat any dry spots, wait a bit, then add the thickened epoxy for glue.

Filling cavities or voids needs the same precoat. Of course the fiberglass won't absorb any resin, but it will fill the tiny scratches and give you a better mechanical bond. Also in filling the voids where coring has been removed, the straight epoxy will flow into the corners and give you a more complete bond. Some times you may not be able to pack the thickened stuff in there into all the corners, but it will bond with the unthickened stuff already there.

By the way- a piece of tape on the underside while the filling is going on keeps the stuff in the hole and saves a huge mess down below

Using a bent nail in a drill to remove the core, then back filling with the thickened epoxy gives you a non-crush "hard point" for the backing plate (or large washer) to bear against so the remainder of the core doesn't get crushed from the bolting pressure. In addition it gives you an epoxy surface inside the hole so should the caulking fail , only that epoxy gets wet. The correct routine is drill, remove the core, brush the straight epoxy inside, filll with thickened, redrill and install the fitting.

Of course if you are working on an uncored fiberglass only area, there's no need for the epoxy- just a good caulking.

[Craig]

I really like the ability to cast thickened epoxy. Mix it thicks but not enough that it will not pour and flow. When working with deep holes of smaller diameter, such as a keel bolthole, I like to block the bottom of the hole and fill the entire cavity with unthickened epoxy. I allow it a five minutes or so to soak in and then pull the tape and allow the cavity to drain. If this is a larger cavity I use the drained epoxy to make a thickened batch and pour it back in and let it cure for later drilling. So far no failures with this method, however, it may not be worth the effort if you can brush the entire interior of the cavity.

[Bud_Wilson]

Frank. Get that other Jones boy to post on this hole drilling. He blocks out a patch on the bottom so he will have a apoxy patch on the outer skin. It makes a nice job. OK Ed post you cant keep all your secretes, you know I will rat you out. Y'ALL COME Cap'N Bud. :wink:

[Barry Pyeatt]

Excellent link thru this forum on Mounting Deck Hardware.

http://www.bosunsupplies.com/Mounting.cfm

Also a great discussion on selection and use of adhesives, sealants and bedding compounds.

http://www.bosunsupplies.com/Sealants.cfm

A great "Thank You" to Frank for putting this Links tab on the forum. Good sources and good informtion.

[Greg Luckett]

Nice links, Barry. Thanks.

[Guest]

http://www.classicmako.com/forum/topic.asp?TOPIC_ID=2523&whichpage=1

FWIW department, Check out this link. There are some pointers to your exact questions with photos to illustrate the ease of doing this job. Quite informative and a joy to read!!!!

There are two pages, so don't miss the second page with a lot of detailed shots.

[Frank Hagan]

Thanks, guys! Looks like I'll have to change my prior ways when I'm working on my Potter 19. I have to admit that I did re-do the bedding under most of the fittings already due to it being old and flaking out. I didn't find any rot yet ... we don't get much rain here, and its pretty dry, so that may help. I had not even thought of what would happen with a damp core that then freezes ... I can see how that would cause delamination.

[Tom Lathrop]

The practice of undercutting the balsa in a deck to either clear out rotted wood or provide a strong base for fittings or stanchions is a good one. I don't follow Don Casey's fear of damaging the surrounding wood with a bent nail. I've used bent nails in drills to do this successfully many times. If the hole is completely filled with epoxy, any damage will be sealed anyway.

However, there is one more thing that needs to be done in order to prevent future leaks. The usual practice of drilling a hole through the epoxy and then bolting the fitting on with a sealer underneath will usually leak at a later date. The problem is that tightening the bolts or screws squeezes the sealer into a very thin film and any future movement can break this film and allow leakage. One soultion I use is to countersink the hole so that a doughnut of sealant is formed about the fastener. The elasticity of this thicker seal will provide much greater resistance to leakage.

This same technique of drilling a hole through an oversized epoxy plug is good to use any time an exposed hole is needed in plywood. This is especially true for drain holes and outboard mounting holes which are the cause of much rot in transoms.

[Frank Hagan]

On a P 19' date=' other than the bow pulpit and stern rails and cleats there isn't a whole lot more that has fittings that pierce balasa core.

Maybe the backing plates for the daggerboard lifting pulleys. If these are not receeding into the gelcoat any, than likely these are sound too.

[/quote']

Everything looks OK, but it is the cam cleats for the main halyard and the mast raising system, and the daggerboard lifting pulleys that could be candidates. The bow light was loose, but its in an area where the deck is solid. The hand rails and handholds will be removed and re-varnished soon, so I'll check the core around those.

[warthog5]

The link above that Oyster posted is my boat. I alway's follow this imfo, no matter if it's plywood cored or PVC Foam cored. I don't want water intrusion int any type of core and as said above. It's to keep from the core compressing in Balsa or PVC.

http://bertram31.com/proj/tips/sleeving.htm