Which cheap sealant for filling deck holes?

MissFitz

MissFitz

Well-Known Member
Joined
18 Apr 2008
Messages
688
Location
Brighton
Visit site
I’m going to move a couple of clutches on my deck this weekend & will need to fill the resulting holes (as well as putting something in the new ones I make). I’ve been generally advised not to spend cash on specialist marine products but to ‘get a cheap bathroom sealant from Screwfix’. However, when I go into Screwfix sealants seem to come in a lot of different varieties. Which ones would be ok for my purposes? Also, if anyone feels the advice I’ve been given is misguided, please do say!
 
Yes, it is misguided! The holes will be probably 8mm diameter and need filling with a solid filler. The usual is an epoxy filler which you can buy from a chandlers and if you want it to be almost invisible then fill just below the surface and then use a gelcoat filler to blend in with the surrounding area. Assume the holes go right through the coachroof so it will help to mask over the hole inside while the filler sets.

Your adviser presumably comes from the group known collectively as bodgers.
 
Epoxy putty is good for this. You cut a bit off, knead it until it's an even colour then stuff it in the hole. As said above, tape on the inside helps, and leave a depression in the top for the gelcoat filler, which comes in two tubes. Follow the instructions that come with it.
 
Ok, great, thanks, I will get epoxy for the holes that need filling. What the new holes though (ie the ones for the new clutches)? Should I put sealant in those, & if so what would anyone recommend?
 
Yes, bed on sealant. Which you use depends on your clutches. If they are Spinlock then they specify silicone sealant but others may specify other types such as butyl or polyurethane.

Check if your deck has a foam or balsa core as you will need to reinforce and seal the bore of your new holes to avoid crushing the core or letting water in.
 
MissFitz said:
What the new holes though (ie the ones for the new clutches)? Should I put sealant in those, & if so what would anyone recommend?
Click to expand...

You don't generally put stuff in the holes. Deck fittings should be bedded-down on a suitable medium in such a way that it will also extrude around the fasteners.

You'll no doubt get recommendations for proprietary sealants such as Sikaflex 291, which certainly will do the job. Avoid silicone sealants: horrible stuff, beloved by bodgers.

My own preference is for butyl tape, which does not set, accommodates movement and reliably gives an excellent seal. It's particularly suited to applying small 'cones' under the head of countersunk fasteners, which gives them a perfect seal, too. Available, cheaply, from places such as this: http://www.caravan-components.co.uk...?ObjectPath=/Shops/BT2955/Products/SBS311067R

Butyl's excellent for bedding down windows, too, and compatible with both acrylic (Perspex, etc) and polycarbonate. Handy stuff to have on board. Because it never goes off, it doesn't congeal to a useless lump like many sealants.
 
Last edited:
macd said:
Avoid silicone sealants: horrible stuff, beloved by bodgers.
Click to expand...

Except that Spinlock specifically state that silicone should be used to bed their clutches - I now have a tiny expensive tube minus the little squirt to bed one clutch to the mast!
 
Tranona said:
Except that Spinlock specifically state that silicone should be used to bed their clutches!
Click to expand...

Thanks. Didn't know that. It may account for a strange staining of the existing clutches when we bought our present boat. No idea what goo was originally used, but definitely not silicone. Ironically, the previous owner threw silicone about elsewhere on an industrial scale. Clutches have since been re-bedded on butyl, which is harmless to almost anything.
 
You will need to investigate whether or not your deck is solid GRP or is of sandwich construction, which is fairly common now. The former is uncomplicated, as long as you bed the fitting properly in a sealing medium. In the case of the latter you will have to remove some of the internal timber material and replace it with something a bit more solid. The following link is to an article about how to do this:
sailingmagazine.net/article-permalink-1703.html
Here is some more info:
https://www.google.ie/search?q=seal...hVkBMAKHXZIC_YQ9QEIKzAA#imgrc=DZofCuJJUm6jtM:
And here are some previous threads on the subject:
http://www.ybw.com/forums/archive/index.php/t-379643.html
http://www.ybw.com/forums/archive/index.php/t-372213.htm
http://www.ybw.com/forums/archive/index.php/t-289560.html
http://www.ybw.com/forums/archive/index.php/t-396024.html
 
I'll email you a powerpoint show on how to bolt down deck hardware if you'like. It's from a City and Guilds boatbuilding program I ran up until last year. I'd not use silicone on a boat if I could avoid it, many better products out there. Personally I like CT-1, but many butyls, polysulfides and polyurathanes will do the job. SABA is another excellent sealant.
Countersink the old holes and fill with thickened epoxy, tape behind to stop dribble!
 
Tranona said:
Yes, it is misguided! The holes will be probably 8mm diameter and need filling with a solid filler. The usual is an epoxy filler which you can buy from a chandlers and if you want it to be almost invisible then fill just below the surface and then use a gelcoat filler to blend in with the surrounding area. Assume the holes go right through the coachroof so it will help to mask over the hole inside while the filler sets.

Your adviser presumably comes from the group known collectively as bodgers.
Click to expand...

Agreed. Epoxy is good for sealing old holes, and the type that comes as two bars of stuff that you knead together works well. Epoxy itself is not particularly UV resistant so its best to set it a little below the top surface and use gelcoat filler to finish for practical as well as aesthetic reasons.
 
I agree with Spirit(of Glenans) that we need to know what sort of deck the clutch was bolted to. Was it solid glass or glass with a timber backing pad? If it was solid glass I'd sand back the deck (around the hole) cover the hole with CSM and then paint it with anti-skid deck paint (if appropriate). If the deck is glass with a timber backing pad I'd fill it with epoxy and the finish it of the way the rest of the deck has been done.
 
Lots of sound advice above. Me, I like CT1 and butyl tape. A tip picked up here a while ago....

Once you have drilled your holes for the new fasteners, countersink the tops. The sealant you choose to use - CT1, butyl tape ) will be squeezed into this space and a better seal against water ingress is achieved. Also prevents tiny cracks in the brittle gelcoat from propagating. Just takes a minute....

And, here's something from a recent issue of Practical Boat Owner which may prove helpful. It IS copyright, but this IS Practical Boat Owner after a fashion, and I'm sure both Rob Melotti and Dick Everitt will be pleased someone is referencing them for a change.


41060591082_ff0408acac_z.jpg
 
You must log in or register to reply here.

Share this page

Top