mastic/silicone

[JudoChamion1994]

could anyone tell me what mastic/silicone is used to bond two halves of a grp overcab together ,mine seems to be leaking. i intend to take out the old and replace with new

[mike 202]

I would suggest that you remove the lining and join the 2 halves together with a strip of fibreglass matting and resin, on the inside of course. Look up on the internet about building fibreglass (Grp) canoes and you will see how the top and bottom halves are joined. This will be a permanent resolution to your problem. Good luck.

Mike

[JudoChamion1994]

remove the lining is not an option as this would mean dismataling almost half of the motorhome.hence the reason for only replacing the mastic/silicone, which brand/type/make ect

[Brian Kirby]

It will depend whether you want a quick bodge, because you intend selling the van, or a more permanent repair, also possibly because you intend selling the van.  :-)

Ideally, you will need to contact the van maker, to find out what kinds of sealant were used on your van, either actual brand and type, or at least the generic type.

The reason is that sealant technology has changed over the years, and some types are incompatible with others.  Mix the wrong ones, and there will be no adhesion between the remains of the old, and the new (so a new leak at the interface/s), and even possibly a reaction between constituents that will begin breaking down one, or other.

If you cannot find out what was used, I think your best approach for a permanent repair will be to remove all traces of the original sealant - which may be quite a job - for the full length of the joint, so that there will be no junction between old, and new, sealants.

Whatever was used, it is unlikely to be a silicone, which in any case comes in a variety of formulations, and is not a "one-size-fits-all" product.

There are a number of products made by Sika, mainly under the Sikaflex brand, and by Henkel Loctite, under the Teroson brand.  If starting from scratch, I think you are looking for a silane-modified polyether sealant, such as Terostat MS 939, or the Sika equivalent modified polyurethane sealant (probably Sikaflex 521).  These are highly durable one part synthetic rubber adhesive fillers, that cure using atmospheric moisture.  They set to a tough, highly elastic, compound, that sticks like the proverbial - so don't get any in yer hair (or anywhere else for that matter)! 

It would be wise to contact the technical department of either company, tell them what you are intending to seal, and ask for their recommendations, plus the product datasheet, COSHH sheet, and stockists.

[lennyhb]

Even if it means a lot of work if you have a leak you really do need to remove any internal panelling as there is a high likelihood of damp & rotten timers that will need to be dried out/repaired.

 

I've repaired caravans before and you would be amazed how water can penetrate & the damage it can do. If you know it is leaking it has probably been doing so for a long while.

 

 

 

[Rayjsj]

I agree with Brian, use a Sikaflex product, 521 or 221, i've used both and can't sing their praises enough, i think that 521 cures faster, being the main/only differance. A Fiamma roof vent spoiler that I fitted 4 years ago using ONLY sikaflex (as i didn't fancy drilling the roof) is still as solid as a rock. Don't use standard domestic stuff, no more nails etc., nowhere near as good, Good luck Ray :D

 

ps make sure you get a long 'sell by date' as it does 'go hard'. and it is available a bit cheaper on E-Bay.