Re-fixing a stanchion base. Don't ask.
4 screw-head bolts. Outboard pair have the nuts glassed in.

1. How do I clean the existing sealant off the gelcoat
2. What kind of Sikaflex do I want to seal it down again? Do I even want to use Sikaflex?

Thanks in advance

1. Someone smarter than me will answer this
2. No, don't use Sikaflex, use butyl tape.

I have a history of making a mess with sealants, I like the idea of butyl.

All my deck penetrations are sealed with butyl. The only leak was due to my poor workmanship.

Hi Jon.
Countersink the holes going through the deck.
Push the hold down bolts through the stanchion base plate.
Wrap butyl (liberally) around the hold down bolts (like an O-ring) where they exit the underside of the base plates.
Tighten down. Flat washers on the upper-side of the base plate will allow the bolts to turn without binding on the plate.

You want to seal the through deck holes there is no value in placing butyl between the base plate and the deck.
The butyl as o-ring seals these holes.

gary

I have no doubt Gary's method works, but I do mine differently.

I make a small o-ring which I put on the countersink bevel face of the screw. Then I place a larger o-ring on the underside of the fitting, surrounding the hole. I make the diameter of this large enough so that it does not spread into the threads, which makes disassembly much easier. The butyl in the countersink provides plenty of resistance to allow tightening of the nut from below. I do something similar with bolts and washers above deck. It's important to not let the screw or bolt rotate as you tighten the nuts.
All good for 10 years and counting.

Cheers, Graeme

Consider using Simpsons adhesive sealant, the white stays white, is uv stable,it is as strong as and as Garry has said, countersink the deck so that you form an "o ring" but I would stick the entire base down ensuring that no water can get under the thing. Also it is easy to clean up while still wet.

I did my entire genoa track, 15 or 20 bolts all had to be inserted at the same time, wasn't easy given the track is mounted with curve to match the deck.
The deck is west system construction using solid cedar/kauri however there is 12mm teak glued with epoxy over the top and water was getting between the deck and the teak and leaking through some of the bolts
I used the above method but rather then a large oring underneath the fitting I covered 50% of the thread in butyl to ensure it sealed the teak and also the deck beneath, which I cannot access to countersink.
Great result nearly 2 years in not a drop has come through any of the track bolts. I have done other fittings as well but the track was by far the most challenging.
butyl is my go to, I keep a roll of white and black onboard. Doesn't go off like Sika either so using once and storing the left over is no problem.

Countersink the hole and use black mastic. Best if you do not use sealant under the flat washer or plate underneath. If the water does leak past the thread it needs somewhere to go. It's better to have the water drip clear than be trapped in the deck structure.

Have become a real fan of fixtech fix15 after numerous similar uses of the cartridge variant over the last year. It doesn't go off in the nozzle after small volume use - just leave a bit out of the end and next use extract that solid end out and the semi-solid part inside the tip breaks off and you are good to use again...............

www.theboatwarehouse.com.au/clearance/fixtech-fix15-multi-purpose-adhesive-sealant-white/?sku=FIX-FIX15WHL03&gad_source=1&gclid=EAIaIQobChMIuPipofKAiQMVKNUWBR3eWxvDEAQYASABEgIfxPD_BwE

www.fixtech.com/en-US/products/fix15-multipurpose-adhesive-sealant

I agree with r13 fixtec is as good as goo gets, at least so far. Butyl gets a wrap & it doesn't go of in the tube, like goo.mounting cleats on a timber deck I threaded the bolts up from the bottom & kept a puddle of epoxy on top of the thread as it was worked up into position, if you have a cored deck it might be worth the upside downness to ensure waterproofing the entire penetration

And if your holes look a bit tired or a bit naff (not the glassed in nuts ones) just tape them up from underneath, fill them with epoxy and redrill them.

Can I suggest this solution.
Every boat i have has this and has for decades.
Spend the time and make small teak blocks for every deck fitting.
Especially under load fittings and stanchions which suffer uneven loads.
Works particularly well where you have two hard surfaces. Ie. Stainless stanchion base and GRP deck.
It reduces movement at the deck interface of the bolts and also the timber can swell if wet.
Even 6mm thickness is fine.
Same goes for headsail tracks which again have uneven loads.
Besides it looks like you care.

I will post some pics.

Select to expand quote

r13 said..
Have become a real fan of fixtech fix15 after numerous similar uses of the cartridge variant over the last year. It doesn't go off in the nozzle after small volume use - just leave a bit out of the end and next use extract that solid end out and the semi-solid part inside the tip breaks off and you are good to use again...............

www.theboatwarehouse.com.au/clearance/fixtech-fix15-multi-purpose-adhesive-sealant-white/?sku=FIX-FIX15WHL03&gad_source=1&gclid=EAIaIQobChMIuPipofKAiQMVKNUWBR3eWxvDEAQYASABEgIfxPD_BwE

www.fixtech.com/en-US/products/fix15-multipurpose-adhesive-sealant

And just on the longevity in the tube aspect I was told to keep Sika 291 in the freezer and that works well for that product. As for the stanchions I use butyl tape which I got from West marine mail order long ago and it's still good.

Butyl for the win. No mess no fuss.

thanks team Seabreeze.

Lydia, if I had access to the bit of teak and the workshop to make the bits I would be tempted. Actually having now had a good look up and down the gunwhales the most urgent need for some sort of middle-man between deck and the steel is the four points where the pulpit joins the foredeck.

Select to expand quote

JonE said..
Butyl for the win. No mess no fuss.

thanks team Seabreeze.

Lydia, if I had access to the bit of teak and the workshop to make the bits I would be tempted. Actually having now had a good look up and down the gunwhales the most urgent need for some sort of middle-man between deck and the steel is the four points where the pulpit joins the foredeck.

JohnE, you could go the non-sexy route and get an online mob to 3D print some blocks for you. You can get solid UV proof 3D printing nowadays from a range of mobs, just google 3D printing service.
It's not like they are complex to draw up, if you have the pulpit base measurements it'd be a pretty painless process.
This took me a couple of minutes to whip up, this is a 90mm x 56mm 4 post stanchion base.
Just an idea if you don't have your own workshop/tools/time?
Cheers,
SB

Select to expand quote

JonE said..
Butyl for the win. No mess no fuss.

thanks team Seabreeze.

Lydia, if I had access to the bit of teak and the workshop to make the bits I would be tempted. Actually having now had a good look up and down the gunwhales the most urgent need for some sort of middle-man between deck and the steel is the four points where the pulpit joins the foredeck.

Teak is nice but 19mm thick dark brown chopping board plastic will last longer, easier to work.

I usually just use a good jigsaw and a sawhorse as a bench and i just use a wood rasp and sand the bevel edge (no router or anything flash)

Not high tech at all.