CONTINUOUSWAVE

Hi All. I am new to this forum. I am currently restoring a 1987 SUPER SPORT 15. I have removed the cockpit, the engine, and the railing. I am planning on refilling some stripped rail [mounting holes] and possibly cockpit holes as per an article in the archives here, i.e., drill out one-half inch, inject epoxy flush with hull. and so on.

As the boat is quite old, am I better off re-drilling all holes?

Some are stripped, others not so much, but have spider cracks emanating from screw holes in gelcoat.

Also, I have a few screws on rail where screw rusted through to the point where the head came off leaving the shank in the hole. Any suggestions on least invasive removal method ?

Thanks for any ideas, love the website and forum. I have been reading it since I bought the boat back in the day.

I do not recommend using the method you mention--drilling out all fastener holes to 0.5-inch diameter and filling with epoxy resin and filler--as a universal method of repairing loose threaded fastener holes. I believe you must be making reference to a suggestion for repairing the mounting holes for the base of a rail support that is mentioned in the FAQ. The rail support bases will completely cover their fastener holes, and that will obscure from view the 0.5-inch new hole. For holes for other fasteners where the hole will not be obscured by the attached item, I would limit the diameter of the newly drilled hole to be less than the head of the fastener screw or at least no wider than the device to be attached.

When using epoxy as a hole filler, you should always use a filler. There are two concerns; pure resin will tend to heat up during curing and may get too hot, causing more problems than it solves; pure resin will cure to a very hard state, and self-tapping screws may have difficulty cutting threads in pure resin.

Wood is often used as a reinforcement for fasteners, and in some instances wood can be used to restore a loose fastener hole. A soft pine dowel can be used, although carpenters will suggest using a hole cutter plug and cutting a bung from a suitable piece of lumber, suggesting that the grain orientation of a dowel rod may be incorrect. In my own experience, I have used soft pine dowel rods to act as a wood filler to restore a fastener hole, but I generally am using only dowels of perhaps 0.25-inch maximum. I use epoxy resin to seal the wood and as an adhesive to hold it in place in the laminate. I have also used just epoxy and filler to fill a fastener hole.

Radial cracks in the gel coat surrounding a fastener hole are a result of trying to force a self-taping threaded screw through the gel coat layer. Gel coat resin, particularly older resin, is very brittle and tends to crack when the pressure of a thread is trying to cut through. For this reason, you MUST relieve the hole diameter in the gel coat layer (and only the gel coat layer) to be larger than the screw shank and to just barely catch the largest thread, if at all. That method avoids cracking the gel coat.

When refitting new screw fasteners into repaired holes, I take care to drill a proper pilot hole, and then relieve the gel coat layer to a larger diameter. I typically use one new screw as a tap, threading it into all the new holes, very carefully and slowly, to cut the new threads. Then I removed that tapping screw and fit a new screw into the hole. The tapping screw head usually gets a bit worn in this process, and by re-fitting a fresh screw after the hole has been tapped, the new screw head is undamaged. The tapping screw tends to get rather hot in this process, and indication of how much thread cutting is going on. Also I don't pre-thread the hole to the ultimate depth; I leave a turn or so for the final screw to cut.

To remove the shaft of threaded fasteners that have broken away from the fastener head, there are not many options. Probably the most reliable is to enlarge the hole so you can get access to the broken fastener with vice-grip-type pliers, and attempt to back out the fastener. As last resort, I suppose a small hole saw could be used to cut out the fastener entirely, if nothing else will give movement of the stuck threads.

If you attempt to drill out a stainless steel fastener stuck in a stainless steel railing, be certain to purchase a special grade drill suitable for stainless steel. A standard carbon steel drill will not be able to cut into stainless steel. You can find these special drill bits at a hardware store for about $4 or so.

Jim--thanks for the detailed reply, that is great info.

I bought TAP plastics epoxy. Can I mix a West system or other type filler with it ?

You can mix any filler you like, even wood chips or sawdust.

Thanks Jim,

I like the solution and the cost even better!

For stripped screw holes I prefer a pure epoxy mixture without any cabosil or filler. The idea is to have the material viscous enough to impregnate the surrounding material so that it will hold. The problem when you introduce fillers is the epoxy becomes too viscous to inject and the material cannot "wick" into a wood core which is the main reason for filling in the first place. On many projects I found pure epoxy injected and drilled to the proper fastener size the better method. Epoxy does create an exothermic reaction so it does generate heat during the cure process. On a screw hole this is not a concern since the amount of epoxy used is small and the reaction does not generate much heat. The concern Jim mentioned is on large amounts of epoxy when the heat generate can be excessive, but filling screw holes is not an problem at all.

Over drilling and inserting a dowel or "other" wood material is an option and when this is used, a pure epoxy mixture is a must.

I've been using this process for 30 years and if there's any question, I'd be happy to post pics of the process and results as a tutorial.

D-

Just to explain further, I usually initially mix just pure epoxy, then introduce that to wet the holes on the first pass. Then, just a moment later and before the resin has begun to cure, I mix in some filler to thicken the resin, and add that to fill the hole.

The cure time for epoxy will vary with the temperature. If working in direct sunlight on a 95-degree day, epoxy will start to cure rather quickly. Working in the shade on a cool morning will give a longer cure time.

By the way, I usually work with WEST System epoxy from their Repair Kit packages. The epoxy comes in small pre-measured foil packages--like catsup or mustard from a take out restaurant. One set of resin and hardener packages makes enough resin to fill plenty of holes. A Repair Kit has five or six sets of foil packages. The shelf life is great.

Cure time on West varies greatly, as pointed out by Jim, but also depends if you are using the fast or slow hardener. I'm not sure what the foil packs contain, and I've always used the fast hardener since it still takes hours to sure. Cure time does come down with increased temp.

Here's an example of West curing and providing a little heat. This is the hottest this pour reached and inside it was a large cavity that was filled.

Pic is of the bow eye hole on a 15 Whaler SuperSport


Several things occured in that pic - 1. Warm garage temp (70F), 2. A large volume of epoxy was used without filler to allow if to flow into the areas where there was foam missing, 3. The epoxy seemed to react with the foam and expanded pushing material out of the pour hole.

D-

I am guessing the WEST System repair packets have the faster cure resin-hardener. It kicks off in about 15-minutes. I have seen the leftover resin in the mixing container get very hot. Also, it cures so fast it gets hard as a rock.

Re reaction of epoxy with foam: perhaps there was some water in the foam, and the heat from the curing epoxy caused it to expand or flow more easily. Epoxy is supposed to not react chemically with foam. By the way, there is a lot of good information about WEST System epoxy in a recorded interview I made years ago for WHALER RADIO. See

WHALER RADIO
http://continuouswave.com/whaler/radio/
WEST System Part 1
http://continuouswave.com/whaler/radio/media/westPart1.mp3
West System Part 2
http://continuouswave.com/whaler/radio/media/westPart2.mp3

I recorded those interviews 18-years ago in c.2000, long before the iPod was invented, but today you'd call them Podcasts. The irony: at the time I published those audio recordings, many people did not have a browser or audio application to listen to them.