Recommendation for a GRP->GRP surface sealant which is not strongly adhesive, can be removed after some years and resistant to diesel spills.

[aidancoughlan]

Hi Folks,

I've removed our cockpit floor (pig of a job), and I'm now trying to find a sealant to re-bed it.
It needs to be able to come up again, needs to seal in a relatively tight vertical surface/surface slot (where the floor sits down into a recess.
... and it needs to be able to resist diesel spills (the diesel filler is right on the floor, beside the joint).

I ruled out Silicone sealants without too much research due to previous prejudice against them (but maybe I am wrong?).
I don't want to use a strongly adhesive Polyurethane sealant (like Sikaflex, PU40 etc.) since I want to be able to remove it again.
I considered Butyl tape, but I suspect the vertical the slot is probably too narrow (a gunky sealant is probably best), and Butyl is affected by diesel.

From what I can gather, Marine Polysulphides are suitable for bedding applications, are less aggressive than Polyurethanes, and the often-recommended BoatLife brand suggests that it is resistant to diesel - but they seem to have gone out of fashion - I can't find any Irish or UK supplier. Unfortunately "Boat Life" seems available in the USA only.

The Adshead Ratcliffe people responded
"...Our Arbomast BR is often used in various forms of boat construction; it wets to surfaces rather than chemically bonding so no actual asdhesion. But it forms a good seal with moderate UV resistant. Diesel resistance is low; so would need to be replaced every so often."..."
"....Re Arbokol 1000, I'm aware of it being used in boats but have no direct experience of it here. Diesel resistance of (fully cured) material is better than Arbomast BR. And you may be able to create a gasket seal with it. However, '1000' seals joints by bonding to them; and its adhesion to GRP is generally very poor. The issue may be that it doesn't bond at all to the GRP and because it doesn't wet in the same way as 'BR', you may not have any seal at all. So would be relying on the tightness of the fit / gasket effect.... So personally, I would lean towards Arbomast BR; but it has its limitations re Diesel. "

Any thoughts / recommendations /suppliers ?

 

[Rappey]

A silicon sealant sounds perfect for this . The key word being sealant and not adhesive.
A thin paint scraper can be used to seperate

 

[aidancoughlan]

Hmm, OK.. thanks for that. Maybe I do need to look into Silicone sealants then - I was once told never to let Silicone sealant anywhere near a boat. I always had the impression it was more suitable for bathroom mirrors etc. I think the prejudice was actually more to do with the difficulty of getting anything else to stick afterwards - if I recall correctly, its apparently very difficult to remove traces of it, and prevents other stuff sticking, painting etc.

 

[pvb]

On my last boat, there was a GRP access panel in the cockpit floor, to allow the engine to be lifted out. It was screwed down on to a recessed flange, and the slot around it was filled with silicone sealant. Worked fine.

 

[Rappey]

Ooh. The initial post has changed a little from when I first read it?
Another option could be a single sided neoprene strip, or rubber .

 

[Javelin]

Easy one, Arbokol 1000.

 

[aidancoughlan]

+2 for Silicone then ... I honestly hadn't considered it.
I also hadn't thought of the possibility of a neoprene gasket either.

@Rappey - Yes, sorry... I've attached photos - and text - to the original post - I hit post by accident after typing little more than the title, and was editing away....
@pvb - Actually, there is a recessed flange like you describe. Maybe there is a possibility of hedging my bets by using Neoprene on the horizontal flange surface (which is around 100mm wide all round), and a gunk-style sealant in the vertical slot.
@Javelin - hi there Mike ... do you recognise the boat .... you did a great job on our chainplates a couple of years ago (Holly, one of your articles in PBO).
I thought of Arbokol 1000, but the Adshead Ratcliffe people said it doesn't "wet" that well against GRP (I take this to mean it doesn't "cling" to the edges), so it would be relying on the pressure/gasket effect. Maybe that wouldn't matter in this application, but it would be nice to avoid the possibility of water ingress via hairline cracks at the edges.

I actually had a thought this morning about using a fairly thin bead of Sikaflex on along the top of the vertical join around the edges (after using one of the others above first) - to provide resistance to diesel spills... and that would remove that constraint, making the choice of the main sealant much easier. What would you think of using Arbomast BR (Butyl based) if the diesel was taken out of the equation in that way ?. Or maybe Arbokol 1000 works better with GRP surfaces than the guy I got info from thought.

 

[Javelin]

Arbokol works really well with grp in my experiance.
We use it pretty much for anything that does not need the adhesive.
i.e. deck cleats, fairleads, hatches and widows if they have enough fixings.
On my boat there are very few fittings that don't use arbokol.

 

[MikeCC]

Is there an exposed core round the edges of panel and floor? Be sure to seal that with epoxy first.