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-   -   Deck Hardware Questions backing plate, etc (https://www.sailnet.com/forums/gear-maintenance/59434-deck-hardware-questions-backing-plate-etc.html)

Waltthesalt 11-01-2009 09:02 PM

I was thinking of the the dissimilar metals corrosion, like the issue of SS screws in an aluminum mast. But having said while I've seen the Al go to white dust on occasion I really haven't seen it to be much of an issue except after perhaps a long time.

nereussailor 11-01-2009 09:25 PM

mitiempo has the right idea about building up the area around the base to level it. The good thing about that is that water won't sit around the base so there's less of a chance of water intrusion.
I would use a stainless backing plate not aluminum. That way there's no chance of corrosion from dissimilar metals.
Another thing I would do is to drill out the holes about a 1/4 inch larger and fill with epoxy and microfibers. That way, if there is any water that leaks in, it won't get into the core.

Dave

mitiempo 11-01-2009 09:36 PM

There is a better way than drilling a larger hole to fill with epoxy. See Maine Sail's how-to link:Sealing Deck Penetrations to Prevent Core Rot Photo Gallery by Compass Marine at pbase.com
Brian

Deadeye 11-02-2009 01:18 AM

Quick question for you guys that are having dissimilar-metals issues with SS and aluminum: are you running the fasteners in dry ?

I've built a bunch of aluminum workboats over the years and haven't had a problem.I use Alu-Cut on self tapping screws and TefGel on threaded fasteners to prevent galling. I guess there's enough of a dielectric residue t prevent corrosion.

Lightly countersinking the paint or anodizing will prevent any corrosion from getting underneath and blistering it. The same thing goes for preventing a screw's thread from lifting gelcoat (and eventually spidercracking it), but I assume everyone knows that one.

jephotog 11-02-2009 12:05 PM

Thanks for all the suggestions.

I kind of made a mess this weekend of my boat. I was going to use maine sails technique on setting this hardware. I overdrilled each hole in preparation. Turns out nothing is cored in this area, so it was a waist of time. By the time I got all the holes cleaned and backed with tape, it was later in the day, but I continued anyways. After pouring in thickened epoxy into the holes I figured that was a good time to check on the working temperature for the RAKA epoxy I was using. It turns out to be 60 degrees or higher which is the warmest it may get during a good day this time of year. So I grab my heat gun and apply heat to all the holes. This liquifies the epoxy, which in turn attacks the duck tape below, which begins to pull away. I notice something is up when the epoxy starts shrinking in the holes. I then had to climb into the boat and clean up the mess starting to form down there.

I have talked to the RAKA owner and will be putting a heater in the boat to warm it from below, then a light bulb from above. He said otherwise, as long as I keep it dry it will still setup fine in spring when it warms.

I will try to find a local metal worker and see what I can do. I am going to go with Stainless, as it is simply what I have on hand. I work in transportation, and am away from my house 5 days a week. Whatever needs done on the boat has to happen on the weekends. Nothing is open on the weekends in Utah. I will see if I can get the pieces cut to rough size here in Idaho, then finish it at home on the weekend. I do have a jig saw and grinder.

In terms of packing out the base, let me make sure i got it right.
Tape up the bottom of the stantion with packing tape.
Fill in the underside with thickened epoxy.

Should I put painters tape around the outside of the stantion to pull up and make a clean line?
Do I let the epoxy dry with the stantion in place or do I separate it once it has started to harden?

Deadeye 11-02-2009 04:10 PM

Leave the stanchion in place until you can't dent the epoxy with your fingernail anymore. The tape will prevent a bond with the steel.

If you want to use masking tape to make a line, there's no problem. A popsicle stick/tongue depressor cut off at a 45 makes quick work of cleaning up excess and any shaping duties while the mud is still wet. A careful wipe with acetone or lacquer thinner will clean any residue off the gel, but you'll want to sand & paint it after you're done so you can sand 'er all smooth at that time instead.

jephotog 11-03-2009 11:34 AM

Okay I will pick up some west systems epoxy this weekend, to extend my temperature range. Then get this done. In the situation of building up the area under the stantion, what about the bolts. It seems like I would want the bolts in place when I am backfilling epoxy under the stantion.

Should I coat the bolts with something to prevent adhesion to the epoxy?

When do I take the bolts out?

mitiempo 11-03-2009 12:32 PM

jephotog
You don't really want to "backfill" the area under the stanchion base. After you have prepared the area by sanding the gel where the base will sit and cleaned with acetone mix the epoxy and thicken with whatever you're using (colloidal silica) until it is a thick peanut butter consistency and won't run. The bolts can be waxed so they won't stick. The bottom of the stanchion base should also be waxed or covered with thin plastic to prevent sticking. Place more than enough thickened epoxy on the deck where the base will go. Place the stanchion base on top with the bolts in their holes. Snug down just enough to put the base in the right place vertically. Clean up the excess epoxy which should have squeezed out on all sides. I use a protective glove and run my finger around the piece of hardware to create a nice fillet. Clean up any excess with acetone. Go away for 24 hours. When you come back the epoxy will have set hard and you can remove the bolts and stanchion base. Clean the base off if you waxed it. Paint the edges of the epoxy to protect from uv after washing it with water and a scotchbrite pad to remove the amine blush. After the paint is dry permanrntly attach the stanchion base to the deck using Sikaflex 291 or 3M 4200 as a sealant tightening the bolts as normal. Clean off excess sealant and you're done. I also countersink the bolt holes slightly to create a ring of sealant around the bolts.
Brian


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