vyv_cox
Well-Known Member
Having used both PU sealants quite extensively, I cannot tell them apart. Some of my PU40 must be 6 or 7 years old by now and seems to be holding up well.
I have used OB1 quite a lot at home and find it to be excellent
CT1 anyone?
- Thread starter wombat88
- Start date
I have used OB1 quite a lot at home and find it to be excellent
dankilb
Well-Known Member
Agreed. What’s also great about all of the options discussed above is how nice they are to apply/work/tool (I’ll be straight onto @Malabarista ’s cup of water trick!).
In contrast, one of the next jobs on our list is bedding/bonding large acrylic windows with Dow 895 (pure silicone I believe). My research suggests a very uncompromising tooling time (we’re aiming for 20 mins between bonding and removing masking tape!).
vyv_cox
Well-Known Member
After many attempts at sealing my boat's windows (which turned out to be largely due to the fact that the glass was too small for the frames) I finally had them done by a firm in Athens (with new glass). They used a cured silicone, which made me a little apprehensive but they have proven to be superb. About 8 years now, totally leak free.
Plum
Well-Known Member
6 years ago I replaced the acrylic in my Lewmar hatches, bedded onto 3M™ VHB™ double sided adhesive foam tape then with with Dow Corning 791 (as recommended by Dow when I e-mailed them for advice) for sealing the gap between the acrylic edge and the aluminium frame. Still perfect.
www.solocoastalsailing.co.uk
Keith 66
Well-Known Member
Restoration mans comment about CT1 formulation changing & not sticking to alloy as well is timely.
I have a major reseal job on my hands with the windows on our Sabre. Bought new 11 years ago, glass was assembled to the frames with black butyl rubber, it started to crack up at about 7 years & has now failed completely, its cracked into short sections that have let go from the glass & alloy frame, in places you can pull sections out.
Last year as a temorary fix i raked the joint out & sealed it with polysulphide
Strange thing is i used Hodgsons butyl sealant for the frame to cabin side joint & it did rather better
Im not keen on using butyl again to reseal the glass looking at the short lifespan.
I have a major reseal job on my hands with the windows on our Sabre. Bought new 11 years ago, glass was assembled to the frames with black butyl rubber, it started to crack up at about 7 years & has now failed completely, its cracked into short sections that have let go from the glass & alloy frame, in places you can pull sections out.
Last year as a temorary fix i raked the joint out & sealed it with polysulphide
Strange thing is i used Hodgsons butyl sealant for the frame to cabin side joint & it did rather better
Im not keen on using butyl again to reseal the glass looking at the short lifespan.
dankilb
Well-Known Member
Just finished bonding the second window with Dow 895. We used a structural glazing spacer tape, as the frames/rebates needed lots of remedial glasswork and I wasn’t up/confident in meeting the requirement of ‘VHB’ tapes to have a very flat substrate (-1mm from memory). I can see the VHB tape would work well on, say, flat/factory gelcoat.
This is of course major and potentially misleading thread drift as 1) Dow 895 is pure silicone and 2) polyurethane/hybrids may not be suitable or bond to acrylic (without correct priming/specialist products).
One relevant point was the it also worked/tooled beautifully, as with CT1/OB1. It really feels like these modern branded sealant/adhesives are nicely user friendly and consistent in application. I couldn’t have done it as neatly without the soapy water trick, especially for keeping my spatula clean and working the final fillet neatly. Interestingly the TDS said not to use water, so I didn’t spray it and ensured the fillet was worked initially with a dry finder, before wet tooling. The first one done 24hrs ago cured up nicely.
This is of course major and potentially misleading thread drift as 1) Dow 895 is pure silicone and 2) polyurethane/hybrids may not be suitable or bond to acrylic (without correct priming/specialist products).
One relevant point was the it also worked/tooled beautifully, as with CT1/OB1. It really feels like these modern branded sealant/adhesives are nicely user friendly and consistent in application. I couldn’t have done it as neatly without the soapy water trick, especially for keeping my spatula clean and working the final fillet neatly. Interestingly the TDS said not to use water, so I didn’t spray it and ensured the fillet was worked initially with a dry finder, before wet tooling. The first one done 24hrs ago cured up nicely.
Daydream believer
Well-Known Member
Cleaning/priming surfaces of any filler is always of prime importance
If, as I have had, you have a few hundred metres of it to apply then one will find that ones finger will soon wear out. Sticks with rounded ends tend to push excess to the sides & spread it around. \If course the trick is not to apply too much to the work in the first place & to apply a consistent bead.
To form the fillet I have a selection of putty knives. I have the point ground to a suitable radius. Then by dragging the knife along the work the flat side of the knife will collect the excess from one side first, whilst leaving a small round ( radius depending on the round ground on the point). The turn the knife through 90 degrees & repeat the process & clean the excess from the opposite face.
In some instances the excess on the blade can be worked into further fillet & be re used, but it depends on the work. If for instance it is the lands in a clinker boat one can collect the excess & work it into the lands as one moves along, thus wasting little material. If it is to, say a tiled fillet round a bath,then this would not be possible
