Hello and sealant questions

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IJL

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I have been lurking for a while but now I have bought a boat I have many questions

I have taken the handrails off to strip and oil, they were bedded with a mystery clear sealant which looks like bathroom silicon, what's best to use when replacing them. I also have a few unrequired deck fittings to remove can the same stuff be used to fill the holes?

Thanks
Ian
 
Welcome to the forum.
I've just recently use polyurethane sealant for a job rebonding a lewmar hatch and was very happy with the result.
No doubt sikaflex is the best and most expensive stuff but I found a cheaper alternative http://www.transtools.co.uk/store/p...polyurethane-pu18-adhesive-sealant-black.html
Also available on Ebay
Polyurethane has better bonding strength than silicone so I would go for that It's also not as messy.
mask off the areas you don't want to get any sealant on, apply the sealant and refit the rails, do not fully tighten them up oryou will just squeeze out all the sealant. Once the sealant has set then tighten the fittings further to make a compression seal.
You probably would get away with silicone as it is not continually wet but but I would go for a high modulus neutral (moisture) cure rather than acetoxy cure as it bonds better.

You could use it for filling a few small holes in the deck but I would rather use an epoxy. For small holes you could use something like araldite but you may need to thicken it with talcum to stop it running.
 
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Hello. The experts (a broad church round here :)) will be along but I'll start it off.

The sealant for the grab rails is just to stop water getting under and into the fixing holes - it doesn't need to add any fixing strength so silicone would do the job.

If you remove deck fittings then you will have holes that need permanently filling. At the least I'd use some two part gelcoat filler like Plastic Padding Gelcoat Repair. If the holes are large (say pencil thickness or above) then a proper job with resin and micro-balloons would be advisable. I know nothing about how to do that but someone will....

Good luck and happy sailing. Tell us what boat.
 
I am currently doing up a small and badly bodged motor sailer whose decks are peppered with redundant holes. Some are the result of removed stanchion bases, with holes filled with silicone, some are holes drilled through by accident from below and never filled at all, and in the past few days we found four unsealed bolts drilled through from above the deck to hold the headlining up! We have spent much of the winter trying to find the source of leaks, in the rain. Consequently we needed something that could be applied wet but would make a permanent repair.

With the benefit of good previous experience we have used Milliput, a two-pack epoxy putty that is reasonably priced, easy to use and will set underwater. I have been countersinking the various holes, then plugging from above while my glamorous assistant pushes up from below. This has been very successful and we are now almost watertight.

My personal belief is that silicone's only place is in the bathroom. I never use it aboard as it has poor strength and inhibits the curing of many products, including polyesters, epoxys and many paints. On my little boat I ensure that all trace of it is removed by abrading the deck and drilling out any holes containing it before applying the epoxy. I use polyurethane for all bedding, above and below the water, previously Sikaflex 291 at around £10 per tube, but now Toolstation's PU equivalent at £4, which appears to be identical.
 
Or use CT-1 It is very good for sealing is also vey strong if bonding things in fact that could be a problem if you need to de-bond it. It comes in various colours including clear and can be used underwater (we use it for repairing swimming pools) it can also be painted over.

j
 
sounds like you're doing what I've just finished :)

I used butyl tape to rebed the grabrails (after countersinking and cleaning the holes) as per this excellent guide http://www.sailnet.com/forums/gear-maintenance/63554-bedding-deck-hardware-butyl-tape.html

For filling the holes in the coachroof left by removed fittings I used glass fibre filler topped with P38 car filler for the large holes (probably highly irregular and no doubt someone will say it shouldn't be done), countersunk all the redundant bolt holes before using P38 and then repainted the lot with International Interdeck.

I also tried Gel coat filler on a few holes but gave it up as a bad job when I found out how bl**dy hard it is!!
 
vyv_cox said:
... I use polyurethane for all bedding, above and below the water, previously Sikaflex 291 at around £10 per tube, but now Toolstation's PU equivalent at £4, which appears to be identical.
Click to expand...

Vyv - this is interesting, especially as Sikaflex has got so expensive and I keep having a problem with it's short shelf life meaning brand new tubes have "gone off".
I see on the Toolstation website they have a PU40 polyurethane sealant and a Polysulphide sealant: "Designed to seal joints subject to movement where a tough, flexible, watertight seal is required. Paintable with alkydresin paints"

Any thoughts on which sealant for what jobs, and whether the second polysulphide sealant has any marine role?

P
 
pierscovill said:
Vyv - this is interesting, especially as Sikaflex has got so expensive and I keep having a problem with it's short shelf life meaning brand new tubes have "gone off".
I see on the Toolstation website they have a PU40 polyurethane sealant and a Polysulphide sealant: "Designed to seal joints subject to movement where a tough, flexible, watertight seal is required. Paintable with alkydresin paints"

Any thoughts on which sealant for what jobs, and whether the second polysulphide sealant has any marine role?

P
Click to expand...

Details here. PU18 is made by Bond-it

http://www.bond-it.co.uk/index.php?option=com_virtuemart&page=shop.browse&category_id=88&Itemid=3

Data sheet here
http://www.bond-it.co.uk/index.php?...:pu18-tds&id=59:prem-specialist-seal&Itemid=4

Cant see anything called PU40, maybe another company.
 
SEALANT

joha said:
Or use CT-1 It is very good for sealing is also vey strong if bonding things in fact that could be a problem if you need to de-bond it. It comes in various colours including clear and can be used underwater (we use it for repairing swimming pools) it can also be painted over.

j
Click to expand...

I gave up using silicone years ago. CT1 does the lot and can be applied to wet surfaces.
 
PU 18

I see that PU 18 is headlined as "Sealant" but in the more detaled spec it refers to it being "adhesive". My experience with adhesive is that once bonded it is there to stay and if you need to remove the fitting ever you're in trouble. I had to remove a bow roller that had been "sealed" with an adhesive, it was so well bonded that I pulled the gelcoat off the deck when forcing it off. Be careful what you use.
 
Filling deck holes

Small holes can easily be filled with runny epoxy, such as Araldite if you have access to both sides.

Source some foil adhesive tape. Clean around the holes and degrease.

Put a piece of adhesive foil on the bottom. Fill the hole. Put another piece of Foil on the top to get a good finish!

You can buy two part epoxy which mixes in the nozzle. These are great if you have a lot to do and it makes application really easy.

Tony.
 
another vote for CT-1. Amazing stuff, can be applied on wet surfaces, expels water as it cures, cures underwater and can be painted.
 
pierscovill said:
Vyv - this is interesting, especially as Sikaflex has got so expensive and I keep having a problem with it's short shelf life meaning brand new tubes have "gone off".
I see on the Toolstation website they have a PU40 polyurethane sealant and a Polysulphide sealant: "Designed to seal joints subject to movement where a tough, flexible, watertight seal is required. Paintable with alkydresin paints"

Any thoughts on which sealant for what jobs, and whether the second polysulphide sealant has any marine role?

P
Click to expand...

Polysulphide is recommended by several forumites for underwater duties. I have used it in the past and found it perfectly OK but I could only buy the Boatlife version in 'toothpaste tubes' at extortionate cost, so I used Sikaflex 291 cylinders instead. I use it for every sealing job, above or below the water.

I have only used the PU40 from Toolstation, and only on above-water jobs up to now. Its apperarance is indistinguishable from Sikaflex.

Edit: just read Salty John's blog on sealants and don't entirely agree with him about the permanency of Sikaflex joints. They can always be separated, it takes a gradual peeling action to get the adhesive to unstick. I have used it on my aluminium window frames, which have been removed several times. Despite their fragile construction they remain straight and whole.
 
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vyv_cox said:
Edit: just read Salty John's blog on sealants and don't entirely agree with him about the permanency of Sikaflex joints. They can always be separated, it takes a gradual peeling action to get the adhesive to unstick. I have used it on my aluminium window frames, which have been removed several times. Despite their fragile construction they remain straight and whole.
Click to expand...

I'm guilty of exaggerating and generalising on this issue. I don't have experience with the full range of Sikaflex products. I have considerable experience with 3M5200 and can say for sure it is extremely difficult to remove. The point is, these products require mechanical removal which in the case of the tougher ones means sharp knives and chisels and considerable effort.
 
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