How to dismantle when stuck with Sikaflex

[nmccubbin]

The inspection hatch on our aluminum water tank is bedded in Sikaflex, and held down by 1/4" bolts
Getting the bolts off is no problem, but so far I cannot break the Sikaflex bond.
The cover is 1/4" aluminum, and the tank top 1/8" thick.
Clearly, we do not want to distort the tank top, so brutal force is not acceptable.

I am told that heat weakens the bond. How hot? I visualise a typical heat gun, not flame

Ideas please

[fourlyons]

Do you have a Fein Multimaster tool or equivalent? They also have a blade that has a sharp knife-like edge rather than saw teeth. I use this to cut polyurethane bonds just like this, works very well.

Sent from my Z5157V using Cruisers Sailing Forum mobile app

[Chotu]

Heat gun, yes. Also, heating a scraper red hot and sticking it into the bond.

The “hot knife through butter” technique.

Lots of ways to release these things.

[SVTatia]

What fourlyons said but any multitool will do it with that blade, doesn't need to be a Fein.
Now, WTF, why would someone in their own right mind gasket a tank with Sikaflex???

[nmccubbin]

Because the gasket did not work and we were off trans-Atlantic and the tank leaked when the boat heeled
One side is Vaseline coated, so that should help

[nmccubbin]

I will try a multi-tool, but for most of the periphery of the hatch there is no access without destroying a lot of woodwork

[tkeithlu]

Consider sharpening the edge of a thin metal spatula and taping it in with a mallet.

[JBP]

A thin guitar wire or a camping wire saw can sometimes help slice through it.

[Jammer]

You want to get it good and hot without starting a fire on your boat. 300 degrees, guessing. Have adequate ventilation, there will be toxic fumes.


I like to keep a wet bath towel close at hand to put out any fires I start doing this kind of work. And a hose.



A propane torch used with care will work as will a heat gun or an old clothes iron.


I like to use a paint scraper rather than a knife. Whatever you use you're going to make a mess of it, and the paint scraper won't cut your hand as badly. You may need something really sharp for the first 1/2" or so but after that it's just leverage. You can use a glass razor or utility knife blade for the first 1/2" if necessary.


A wirewound music string will sometimes work well and saw through the sealant, use a D string from a guitar or maybe a wound G string (smaller).

[deminimis]

I just went through this (separating a poorly done repair). Fresh flexible metal putty knives and a rubber mallet. Cuts through the crap. Then a multitool with scraper blade to remove the Sikaflex from the base material (in my case fiberglass). Pain in the arse. I had to do approx 100 lineal feet (and I tried most everything).

[nmccubbin]

Got it off
We drove a wood chisel under one edge
Moved about 1/32”
Drove a couple of maple wedges I left overnight and next day wedges went further in
3 more days driving in a bit each time and she is off