Steel Boat Filler

[mikewilkes]

I got a couple of dents in my steel boat coming through the French Canals and when she comes out of the water later on this year I want to fill them. One of these is below waterline and covered in antifouling.
Question is do I need to go back to bare metal to fill this wee hole? Is there a product on the car market that has got to be considerably cheaper than the "Marine Filler" I saw in the chandler's? I looked at the price and felt quite faint.
I guess what I really looking for is a filler that will go on over abraided antifouling and gloss coat. Or is it that you can do a tie coat between the antifouling and filler as with putting antifouling on an unknown? None of the dents are structual.
Many thanks,
Mike

 

[chippie]

I dont think there is a filler manufacturer that would recommend you try to use their products over the top of antifoul etc. If you dont want to do it properly just live with it. If any steel is showing ,it would pay to sand back and re paint that area.
Fillers and paints should be thought of as systems which require all the neccessary parts to do their job.

 

[PaulJ]

I don't like the idea of putting filler onto antifouling.... the filler will only stick as well as the antifouling. If you want it to stay put you will have to grind down to bare metal and an angle grinder is the ideal tool because it leaves a rough surface to which the filler can "grip". I would only use epoxy filler, particularly below the waterline, if they are only small dents as you say, then it won't cost an arm and a leg. Thick filler tends to crack eventually so if the dents are larger, say over 1/2", I think I would build up first with chopped strand glass and epoxy resin (West System) before finishing off with epoxy filler.....

 

[AndrewB]

You are right that Interfill 400 is unbelievably expensive. But it has the advantages that (i) it is epoxy: impervious, flexible and unlike Polyfilla won't sog and crack off when the hull flexes (ii) can be built up in reasonably thick dobs, unlike conventional microfilled epoxy resin which tends to sag on vertical surfaces (ii) sands easily to a really smooth finish.

Filler should only be applied over an epoxy surface. Assuming the steel is epoxy primed there is no need to go back to bare metal, in fact it is not desirable to do so. Aim to sand off virtually all the antifouling or top polyurethane gloss back to the primer. Then put on at least one tie coat of new epoxy primer before the filler. Further coats of epoxy primer on top and then the topcoat.

Incidentally the most depth you should cover this way is about ½" - deeper dents need to be hammered out before filling.

 

[AlexHall]

Hi,

If the dents are not particularly deep and especially so below the water line, my opinion would be not to bother. But if the dents are fresh then any paint which protected the steel there is compromised. It has certainly lost some adhesion somewhere. if so there is no option other than to abrade the area well and recoat with primer, high build undercoats and then decide if you fill or not. BUT do not apply any filler directly on the steel or even worse on to paint which is not well bonded to the steel.

International have a product called Watertite, which is an epoxy based fine filler for above or below the WL. It is sold in small tobacco sized tins and not back breaking in cost. But because it is an epoxy can only be applied on epoxy or polyurethane substrates.

Check out your funds and why you want to fill the dings or dents and then act accordingly. In my honest opinion, if its below the WL and not unsightly just paint it well and call it a scar. if its bigger and nasty dont fill but try and hammer it or press it out first.

 

[ean_p]

Alex.....do you know this to be right for sure as we've just had an estimate from a local guy who is the Awlgrip recommended man in the area and he was adamant that succesful epoxy fairing had to be applied to the bare steel....is it a matter of individual choice or are there real pro's and cons to it...?

 

[Freebee]

I was told that the royal yacht Brittania had her hull faired with Isopon P38 regularly. That would be cheaper than any marine product.

 

[oldsaltoz]

G'day Mike,

If any filler is applied over your antifoul or other paint is will at some stage fail.

You need to get a good key that the bog / filler can onto, this IMHO means an epoxy coating over bare steel. followed by a wash and sanding then apply closed cell balloons and fair, finally apply more resin and follow up with antifoul.

Hope this helps

Avagoodweekend Old Salt Oz /forums/images/icons/cool.gif

 

[PuffTheMagicDragon]

If Brittania needed to have her hull faired all that regularly, it doesn't say much for the Royal Navy, now does it? ;>))

Wally

 

[Guest]

Try Polyfilla

Heard the following story many years ago from the former Harbour Master of Port Alfred, on the Saguenay River in Quebec (commercial port for bauxite and alumina in, aluminium, lumber and paper out). Harbour Master was a retired Scouse seacaptain. Britannia was coming into port on a royal visit (must have been about 1958/59). Harbour Master noted speed and direction was not ideal, issued a flood of invective at the bridge by VHF, and vessel escaped with a minor scratch to the topsides. Later during a reception he asked the Duke of E who the b****y h**l was on the helm, to which the handsome Greek answered "I was." Point of the story is that apparently Brittania's entire topsides were skimmed with plaster and painted, giving the "perfect" finish. The slightest damage appeared as a dreadful white scar, but could be repaired in minutes with Polyfilla and spray painted within the hour. Not sure if this helps - wouldn't work below the waterline!