David:
I would go with the advice from West. I have had to do this in the past and did pretty much what the West advisors suggested to you with a couple of exceptions that you might want to consider:
I used wood screws rather than machine screws and inserted them when the epoxy had set but before it cured. At this stage the epoxy feels firm but you can still mark it with your fingernail. You can also tighten the screw down firmly but don't tighten it so much that you tear out the epoxy. If the wood core is solid and you have the depth, you can use screws that are longer than the hole so that the end grabs into the core material. I would be a bit concerned that without being able to fasten the bolt down and relying only on tape to hold it in place against the hydraulic pressure, the plate might not be held securely.
Depending on how hot it is the epoxy usually reaches the solid stage in a few hours. I would not go beyond 24 hours if you can avoid it. If you wait until the epoxy is cured it can be difficult to drill the pilot hole without the bit wandering into the softer core material. However, If you wait too long and need to drill into cured epoxy use a brad point bit to keep the bit aligned. There is no hydraulic pressure to contend with using this method. I don't think that there is any advantage to using machine screws rather than regular screws in this situation.
In any event, the worst that can happen is that you just drill it out and try again so I wouldn't worry about it.
Sometimes it can be very difficult to remove a screw once the epoxy has set and it is quite possible to break the screw or strip the head. The solution is to heat the screw with a soldering iron before backing it out.
Graham Stewart
Rhodes 76
On Thursday, August 31, 2023 2:25:33 PM (-04:00), DAVID BERG via
Rhodes22-list wrote:
> Rhodies,
>
>
>
> I recently liberated my mast step tabernacle from the deck while (not)
> raising the mast. At first I was perplexed that the machine screws
pulled
> right out. After further review I've learned that this is by design.
I've
> reviewed the post that I could find related to the repair, and called
West
> Systems for their take. I'm still left wondering which way to go. I'm
> wondering if anyone has anything to add.
>
>
>
> I was going to fill the cleaned and chamfered holes with thickened epoxy
> (System 105/205), with no toothpicks or wood shavings. Then drill and
tap
> the semi-cured epoxy for the 1"-20 machine screws. The questions I had
> regarding this method were:
>
>
>
> 1) Why do I need wood shavings or toothpicks? I don't plan to take the
> screws out for any reason.
>
> 2) If I let the epoxy set up (but not cure) would I be able to drill
> and tap it?
>
> 3) How long would I let it set up before drilling? It seems form my
> research that drilling and tapping fully-cured epoxy is very difficult.
>
> 4) If using the epoxy with shavings or toothpicks what is the order and
> timing of the re-assembly?
>
>
>
> After talking to West Systems, I think I'm leaning towards what they
said to
> do:
>
>
>
> 1) Clean out any old material
>
> 2) Oversize the holes to make room for the epoxy between the machine
> screws and the existing deck
>
> 3) Chamfer the top of the holes at the deck
>
> 4) Wet out the holes and screws with un-thickened epoxy
>
> 5) Thicken the epoxy with 406 or 410
>
> 6) Fill the holes with thickened epoxy
>
> 7) Set the tabernacle plate and insert the 1"-20 machine screws
>
> 8) Clean off the excess epoxy that is displaced from inserting the
> screws
>
> 9) Tape the screw heads down to prevent the screws lifting from
> hydraulic pressure.
>
> 10) Let it cure and go sailing
>
>
>
> With the solid (non-cored) deck, there should be no need to use any
butyl or
> sealant.
>
>
>
> Looking for any other advice or opinions anyone may have on the topic.
>
>
>
> David Berg
>
> Blue Loon, Rhodes 22 1996/2003
>
> Minneapolis
>
>
>
>
>
> From Graham Stewart July 2020
>
> Chris: If the gelcoat around the holes is mearly broken up a bit you
should
>
> be able to remove anything that is loose and fill it with the thickened
>
> epoxy when you fill the holes. Given that the holes are covered with the
>
> mast step anyway, you don't need to worry about the exposed epoxy. Epoxy
>
> exposed to sunlight degrades quickly. I really like the idea of using
>
> slivers of wood in the hole with the epoxy. I wish I had thought to do
that.
>
> I would not pack it hard with the wood slivers - maybe 50% wood and the
rest
>
> epoxy.
>
> If the screw is inserted into the epoxy I see no reason or benefit from
>
> removing the screws to inspect the holes. That might cause more problems
>
> than it solves. One thing you should note is that screws driven into
uncured
>
> epoxy can be very difficult to remove and it is quite easy to strip the
head
>
> or even break it off. The wood slivers should help but if the screw is
hard
>
> to remove put a soldering iron on the head for a while. That softens the
>
> epoxy and it will come out easily.
>
>
>
> If this event reoccurs it is likely that the screw will pull out the
epoxy
>
> plug since it is much tougher than the core material, Hopefully this
does
>
> not happen very often but if it does the fix remains the same.
>
>
>
> Graham Stewart
>
> Agile, Rodes 22, 1976
>
> Kingston Ontario
>
>
>
>
--
Graham Stewart
gstewart.gm at gmail.com
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