Over drilling holes in hull

S

Stormydos

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C Dory Year
2000
C Dory Model
22 Cruiser
Vessel Name
Stormyuno
Hi all I'm reseating gas tank partician and looked at forums on oversize holes and filling with epoxy, but I can't seem to find how much to oversize. What would you recommend. Holes seem dry however 1 felt damp.
 
Along the same line of this question, for the aluminum fuel tank bracket screw holes in the sole of the 22 cruiser.

Can one simply undercut and then fill with thickened epoxy, then re-drill and re-screw into the dried thickened epoxy?
 
Generally 1/4 to 5/16" is enough for each of the screws holding a cleat or strap down. Same for an "L" bracket.

You undercut with a Dremel tool, , bent wire, or small allen wrench:

fillets_and_filler_027.jpg

For the cleat holing the tank in place there may be a better way. That is to overdrive and fill the hole where the screw was. Then use strips of glass to hold the cleat in position. If any screws are needed then the hole is drilled in the cleat. Cleat can even be mare of fiberglass.
 
Thanks, now you have me thinking do you think marine adhesive would hold for the Cleats?
 
mine are the 1989 era z type angles. 4 each hold each tank. the front ones need to be removable to remove the tank.

If the crew fastener hole is undercut and epoxied, can the screw be drilled and fastened into the cured epoxy fill?

are there any pics of the repairs? [/img]
 
A Fishin C":7wtu74tp said:
mine are the 1989 era z type angles. 4 each hold each tank. the front ones need to be removable to remove the tank.

If the crew fastener hole is undercut and epoxied, can the screw be drilled and fastened into the cured epoxy fill?

are there any pics of the repairs? [/img]
Click to expand...
Any time you put a screw into the cockpit floor, or any cored area, you should drill, undercut, fill with epoxy, then drill a new pilot hole and put the screw into the epoxy plug. This way, there is no conduit for water into the core.
 
ok, thanks Dr Bob,

just wanted to make sure I could drill and screw into epoxy (vs thru bolt)
 
You totally can drill/screw ("pointy screws") into epoxy, but it's not my favorite way. I just never get a really happy feeling drilling and then screwing in pointy screws, but as mentioned, it does work. Probably just a personal quirk.

Most of the time I tend to either through bolt or drill and tap the thickened epoxy (structural thickener). It depends on the situation.

Another option is to screw the (pointy) screw in when the epoxy is in the green stage (like cheese texture), or to cast it in place. The WEST System free manual talks about these methods and has great, easy-to-understand drawings. You can find it at the following link. Each "illustration" is a chapter you can click on (it's also available - or used to be - on paper and each one was a chapter in order in a booklet).

http://westsystem.com/ss/use-guides/
 
When I did my boat, I used thickened epoxy and screwed directly into it, but with some precautions. First, I used penetrating epoxy in all of the holes.

http://www.smithandcompany.org/CPES/

It is very thin, probably mostly carrier (something like MEK) and some of your penetrations will take a surprising amount. That is because the balsa core can have small passage ways in it. Smith's will seal them up and provide a layer of epoxy coating the hole before you put in the thickened epoxy. (Plus there is some evidence that the MEK fumes left in the balsa core kills dry rot spores).

Then I used glass micro-balloons as my thickening agent. It's not a strong as glass fibers, etc., but it is a more forgiving composite that is less likely to split when driving a screw into it. Just to make sure (the belt, suspenders, thumbtack approach), I put a drop of penetrating epoxy in the properly sized hole when driving the screw. That way, if there was a breach in the thickened epoxy, the penetrating epoxy would seal any split.

Mark
 
BTW, when I'm going to tap, I use either colloidal silica (WEST or other brand) or WEST 404 high density filler (or a combo of the two). Same for filling overdrilled holes if I'm going to just re-drill for a through fastener. Or sometimes I will now use WEST 610, although it is slightly less structural so again it depends (sure is tidy and handy though). On the 610, they say there is no need to first wet out with neat epoxy, but I still do it, especially for critical applications.
 
C-Brats All:

I have to say, this is one topic that gets brought up time and again, and isn't just a repeat of what has gone before.

The drilling of holes, filling of the enlarged cavity with matrix, and embedding of screws, tapping of threads, or placement of through bolts has become a "science" in itself.

Bob (Thataway) was the first I remember to make a detailed post on the topic, and the refinements just keep coming.

Add them all up, and you could certainly make them into a nice chapter of a book on fiberglass hull maintenance.

Good job, everyone! :wink :thup

Joe. :teeth :thup
 
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