Mending leaky hatch- what sealant?

[phanakapan]

I have removed the perspex from the deck hatch, the original sealant looks like black rubbery stuff- it also had some clear stuff on top which looked like a bodged attempt to fix the leak. Should I remove all original sealant (how?) and start afresh- and with what; or leave the original black stuff and 'top it up'- again wit h what product. I seem to remember a thread that said silicone based sealant would not stick to Sikaflex- but I'm not ure what the original stuff is, exactly.

 

[Tidewaiter2]

Best to strip it all off and scrape residue off with old chisel then clean v. carefully with acetone. We had small leaks round windows- used Cap'n Collis leak stuff, stopped it for a while(dries clear- prob what's on your hatch) but in the end, we bit the bullet and had all our windows redone by Northshore- windows are mix of acrylic/ perspex and toughened glass, I think.
They used Sikaflex 291UV internally and externally- windows are set into Sikaflex with no metal rims etc, so paid the yard money to keep insurers happy if one pinged out mid Channel!

Technix in Soton do self adhesive hatch seals of various profiles and car door type seals too by the metre for round the hatch rim- used it successfully on our previous boats to ensure good w/t seal.

Good Luck- spent a cold three weeks in Jan 08 @ Itchenor getting them done- did all my other annual maintainence, mind, so there was an upside.

 

[VicS]

Sikaflex 295 UV is the Sika product to use but i guess you will have to get rid of all the silicone.

The marine handbook is HERE


A MS (Modified silicone) polymer sealant may be a solution. Such as the one mentioned in This recent thread

 

[eastcoastbernie]

Just done my windows so I am now an expert!

Scrape of old silicone with a knife, scraper, whatever will move it. Then go down to B&Q and buy some silicon cleaner. (Used by DIYers to remove silicon from around baths I think) It is the consistency of jam. Spread it jam-like over silicon residue and go off and do something else for 2-3 hours. Yes, 2-3 hours!

Come back and clean off remaining goo.

To put windows back, you could use Sikaflex. My marine window specialist people recommended Marine Flex which they say is the same sort of stuff but not as expensive.

 

[Tidewaiter2]

Vic, I think you are right re 295 UV rather than 291UV-
I was sure it was 291UV but they left me the remains of a tube -I'll dig it out to be sure, if it's still there.

Our windows and hull need to flex under sail a bit-thats why they leaked again; could that be why 291 rather than 295?

 

[misterg]

[ QUOTE ]
... clean v. carefully with acetone...

[/ QUOTE ]

I'm sure someone will correct me, but I thought that acetone was a big no-no with acrylic, as it causes crazing.

Vic??

Andy

 

[VicS]

Mending leaky hatch- what sealant? [Re: Several of you]

Captain Tolly's Creeping Crack Cure I think.

Silicone not silicon. Silicon is hard non metallic element used in alloys and micro electronics. No good as a sealant or for your breast implants /forums/images/graemlins/grin.gif

Sikaflex 291 is the general purpose adhesive sealant. Sikaflex 292 is an elastic adhesive for structural bonding. Sikaflex 295 UV is a UV resistant adhesive specifically for plastic glazing (Acrylic and polycarbonate)
In addition to the Sikaflex marine Handbook mentioned above there is a Users Guide

You must be very careful with any solvents on acrylic and, I understand, even more so on polycarbonate. I was surprised to learn from a recent post of the effects of isopropyl alcohol, even in the short term, on acrylic.

 

[Tidewaiter2]

Re: Mending leaky hatch- what sealant? [Re: Several of you]

Vic,
Thanks, yep, Cap'n Tolley's- I think I was thinking of the old patent medicine- same effect? /forums/images/graemlins/grin.gif

From your info, 295UV it must have been.
The solvents were only used on the bits that really would not shift- everything that could be was painstakingly chiselled out by hand- hence the cost in manhours /forums/images/graemlins/frown.gif

If there is a next time in our ownership, I'll get our boys to do it! /forums/images/graemlins/grin.gif