Epoxy Bedding

K

kennharriet

Member
I purchased new fuel tanks and want to properly bed the tank hold down screws with epoxy. At the same time I intend to take care of the bilge pump screws and cabin cabinet screws. With a search of the forums I did not find any information on the type of epoxy or depth of the balsa core that should be over drilled. Thanks in advice for any advice. Thanks, Ken
 
My suggestion is to fill any screw holes, with epoxy thickened with Cabosil (fumed silica). Then make PVC or wooded cleats, which will go on the inboard side of the tanks, epoxy these in place, and put screws into the cleats, instead of the hull bottom. This is the way my 2006 22 had the tanks secured.

For the cabinets, In one of my boats, I just removed each L steal L bracket, drilled out the top of the holes, filled the holes with the thickened epoxy, and then made tabs of glass cloth, load in place with epoxy. This is stronger than the "L" brackets and will be a cleaner, and rust free application.

If you want to drill the holes, I would make them 1/4 to 5/16 inch in diameter, and drill about 1/2" deep. Don't apply much pressure. coat the inside of hole with unthickend epoxy (just the the mixed epoxy, and then thicken it. I use cotton swabs to apply the thin epoxy. All of the holes can be done in a few minutes.

Below is a photo of some 1708 glass fabric, I had which replaced an "L" bracket on a 25. The photo is looking down--the glass is epoxied into the floor, and up the side of the Decaboard. I put some white pigment into the epoxy. You could use a couple of pieces of 6 oz cloth or tape. Each "tab" would be 1 1/2" wide and 3" long. 1 1/2" on the floor, and 1 1/2" on the side of the cabinet. Do half the brackets the first time, and then the other half the second time. That way the cabinets will remain stable.

2007_05_25_004.sized.jpg

As for the pump--many of the boats have a sump, with some core under it, and others have solid glass. Again thickened epoxy, as above. Put the screw into the thickened epoxy. However, in each boat, I have filled the screws, and then set the lower part of the pump into G flex epoxy. That way no screws into the hull.

If I am putting screws into the plug, I will use half Cabosil and half medium density filler to do the thickening to peanut butter consistency.
 
Thanks Bob. That makes good sense to attach cleats, then screw into cleats. I don’t have much experience with epoxy. Can you recommend a particular product? Is it available at the local Napa?
 
Thanks Bob. That makes good sense to attach cleats, then screw into cleats. I don’t have much experience with epoxy. Can you recommend a particular product? Is it available at the local Napa?
 
I am not sure if your local NAPA will have epoxy resin. If not Amazon does, I have been very happy with West System epoxy, buy a can of epoxy resin and a smaller matching can of hardner, the slow version in summer, then get a set of hand pumps that will measure the mix proportions for you. Check out their line of fillers, the silica thickens, the high density adds a bit of strength, and the fiber has the most strength but is not as smooth to work with. I always use silica and then add one or both of the others. Low density is for easy sanding/surfacing and not to be used below the waterline. Wear gloves epoxy is more prone to allergic reactions than polyester resin. Scuff up the glass and clean with acetone first. You can saturate short lengths of glass tape on some cardboard and then put them in place with a "chip" hair paintbrush dab out the air in between layers of glass. I think you will find this very easy to do once you get started.
Good luck!
 
I did this last year with my fuel tanks. When drilling into the cockpit sole you'll easily feel the drill bit penetrate the top glass layer, go into the balsa and then hit the bottom layer. I don't know the actual depth but it was around a ½ inch, maybe a little more. I filled with epoxy and then screwed into the epoxy plug. For me it was easier this way than building a 'tab'. I was worried I wouldn't be able to get a 'clean' look to it. Plus I wanted to be able to undo it if necessary. The way my forward partition was set-up for future removal it was easier to just screw it back down, then bedded everything in 4,200. I haven't done the cabinet hardware yet. Wasn't to worried about it as that area rarely sees water.

I used West System Epoxy resin. I don't know if anyone else has thoughts but I've also bought polyester resin from Home Depot before when I need a small amount for a job. There are some differences between the two but I think either may work. I would do a little research though, and get some thoughts from others who have more experience than I.

Here's a link to the thread.

http://www.c-brats.com/viewtopic.php?t= ... c&start=15

Brandon
 
Polyester resin does not form the best bond with well cured fiberglass, definitely not recommended!
( I love polyester for new laminating because you can use chopped strand mat for build up between cloth, but epoxy doesn't dissolve the matt binders, I have hand laminated at least a dozen 55 gallon drums of polyester resin)
 
There are mats which are specifically designed for epoxy resins. However, it he mat is not necessary if putting a few layers together of cloth or composite like the 1708 (which does have one layer of epoxy comparable mat).

I use West Systems, just because I have been using them for years. Back when were were building boats, we bought the Shell Epoxy resin wholesale in 5 gallon buckets, and a one to one ration. There are places where epoxy is better.

I agree that the secondary chemical bond is far better with epoxy than polyester. An in-between is vinyl ester resin. But that is not applicable for the types of repairs we are considering here.

One material to avoid is Bondo. In my opinion, it has no place on a boat--even the one with fiberglass fibers in it....I have seen too many instances where it was used for fairing, there was some water intrusion, and it cracked or popped of. Cars --it is fine...
 
West epoxy is so easy, no reason to use anything less on our small projects.
( just the opinion of another ex fiberglass boat builder that has hand laid up a lot of boats between 32' & 50' and was the head pattern maker for the largest composites manufacturer in Australia)
 
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