Fixed window replacement - Dow 795 still the sealant of choice?

[GordMay]

Originally Posted by s/v Jedi

If there is one thing, only one thing to learn from this thread then it is to use VHB tape instead of screws...

Which specific 3M VSB Tape?
There's LOTS of choices, in the VHB "family".

[s/v Jedi]

Originally Posted by GordMay

Which specific 3M VSB Tape?
There's LOTS of choices, in the VHB "family".

You need one that is rated for replacing mechanical fasteners and you want a thick one that can handle the thermal expansion.

I used type 3991 but it seems to have been replaced by 4991.

It’s best to contact 3M because it’s mostly dictated by the window type and size.

https://www.3m.com/3M/en_US/p/d/b40072036/

[altruistica]

I am about to fit eight new portholes. There are Vetus pm 161 portholes. There will be fixed to a fiberglassed cat hull. They use the clamping inner frame and suggest a sealant to ensure the seal. Would a butyl tape mastic suffice or should I stick to the Dow cornings sealant?

[s/v Jedi]

Originally Posted by altruistica

I am about to fit eight new portholes. There are Vetus pm 161 portholes. There will be fixed to a fiberglassed cat hull. They use the clamping inner frame and suggest a sealant to ensure the seal. Would a butyl tape mastic suffice or should I stick to the Dow cornings sealant?

That is a mechanically fastened porthole so you need a bedding compound. It is above waterline so the best one is https://bed-it.com/

[altruistica]

Thanks for the reply and link.Much appreciated.

[Mickeyrouse]

I have recently been repairing port leaks. I have passed on using sealant of any kind. Instead I bought a set of 1/8” neoprene sheets from a local industrial gasket supply and cut gaskets individually for each port. Yes it took more time. The sheet neoprene for four 9x25 ports and seven 6 x11 ports was about $60 dollars. I traced the ports onto the neoprene then cut with a utility knife (an Xacto will work). I then sandwiched the neoprene between two pieces of plywood and used the port as a drill template for the fasteners. Like any other task involving seals, I cleaned the port surfaces as well as I could before re-installation.
Everything fits up pretty well and seals great. Future removal for whatever reason can be done without risk of breaking the glass. I’ve used sealants in the past, and it seems no matter how much I would use, it didn’t always stop the drips. Buying a sheet of neoprene and just using the outer rim is about an 85% waste factor. I save the cut-out. There will always be another project that needs sealing. Neoprene lasts a long time. And I don’t have half-empty tubes of sealant slowly going bad, deceiving me about its freshness.

[Bowdrie]

Originally Posted by Mickeyrouse

I then sandwiched the neoprene between two pieces of plywood and used the port as a drill template for the fasteners.

Yes, neoprene is a good and handy product to have around.
I just generally mark for the holes and use a leather punch.
A set of them is inexpensive and it saves a lot of fussing with the drill press and plywood.
Although there are hollow drill bits that work well especially if the neoprene is thick enough to not want to "ball-up" when drilling.
I've found that Dolfinite applied to both surfaces of the neoprene makes a very good gasket while still remaining easy to remove.

[s/v Jedi]

Originally Posted by Bowdrie

Yes, neoprene is a good and handy product to have around.
I just generally mark for the holes and use a leather punch.
A set of them is inexpensive and it saves a lot of fussing with the drill press and plywood.
Although there are hollow drill bits that work well especially if the neoprene is thick enough to not want to "ball-up" when drilling.
I've found that Dolfinite applied to both surfaces of the neoprene makes a very good gasket while still remaining easy to remove.

Agreed, I also use a hole punch with neoprene and I also use a liquid gasket helper if I have it, or some polysulfide otherwise, to deal with irregularities in the surface. I found this even works on non skid when I couldn’t bring myself to sand it smooth

[GordMay]

Originally Posted by Bowdrie

...
I've found that Dolfinite applied to both surfaces of the neoprene makes a very good gasket while still remaining easy to remove.

Pettit ‘Dolfinite’ is a Bedding Compound [but not adhesive], recommended for bedding [applied by brush or trowel] mechanically joined parts.
I'm not certain how it would improve a good mechanical gasket, like neoprene - but it might.
I'd be inclined to just use one, or, the other.

➥ https://www.pettitpaint.com/media/52...g-compound.pdf

➥ https://www.pettitpaint.com/media/50...an-english.pdf

[Bowdrie]

Originally Posted by GordMay

Pettit ‘Dolfinite’ is a Bedding Compound [but not adhesive], recommended for bedding [applied by brush or trowel] mechanically joined parts.
I'm not certain how it would improve a good mechanical gasket, like neoprene - but it might.
I'd be inclined to just use one, or, the other.

➥ https://www.pettitpaint.com/media/52...g-compound.pdf

➥ https://www.pettitpaint.com/media/50...an-english.pdf

Gord May, the first link is the "ad copy overview", as it were.
The second link is 11 pages of "safety" data, and at the heading of each page it says; "Trade name: Dolfiinite Bedding Compound".
You don't need to be inclined to use "just one", both links are the same product.
Why have I used it on Neoprene?
Not all the time, but most mechanically fastened joints are not like the cylinder head on your engine, with flat/rigid/machined surfaces.
On things like portlights and aluminum hatch rings you have surfaces that are easily distorted when fasteners are tightened, a thin coat of Dolfinite helps seal between where the fasteners are trying to distort the frame/compress the rubber.
As an aside, one of my pet peeves in doing work on other people boats has been the tendency of too many owners to approach fastening jobs like they were torquing up the lug nuts on a 10-wheeler dump truck.

[GordMay]

Double gasketing is not a generally recommended practice.

When you put Pettit "Dolfinite" on duPont "Neoprene" [chloroprene], you are, essentially, “double gasketing”, using materials of [very likely] differing compressibility/stiffness & recovery values, and doubling the potential leak paths [from 2 to 4].

Using multiple gaskets does not, necessarily, improve the sealing performance. In fact, it can exacerbate the problem, by introducing more potential failure points, and leak paths.
When you stack multiple gaskets, it becomes difficult to achieve uniform compression [differing resilience of different materials], across the gasketed joint. This uneven compression can result in gaps, or inconsistencies, in the seal, leading to potential leaks.

Instead of double gasketing, I’d recommend identifying, and addressing, the root cause of any sealing issues.
This may involve:
1. Choosing the Right Gasket: Selecting the appropriate gasket material and design, based on the application requirements, such as temperature, pressure, and surface condition.
2. Surface Preparation: Ensuring that the mating surfaces are clean, flat, and free from irregularities or damage, to ensure proper sealing.
3. Proper Torque Application: Using the correct torque values, when tightening the fasteners, to achieve the recommended gasket compression.

I remain, so far, unconvinced - but willing to be persuaded.

[s/v Jedi]

Originally Posted by GordMay

Double gasketing is not a generally recommended practice.

When you put Pettit "Dolfinite" on duPont "Neoprene" [chloroprene], you are, essentially, “double gasketing”, using materials of [very likely] differing compressibility/stiffness & recovery values, and doubling the potential leak paths [from 2 to 4].

Using multiple gaskets does not, necessarily, improve the sealing performance. In fact, it can exacerbate the problem, by introducing more potential failure points, and leak paths.
When you stack multiple gaskets, it becomes difficult to achieve uniform compression [differing resilience of different materials], across the gasketed joint. This uneven compression can result in gaps, or inconsistencies, in the seal, leading to potential leaks.

Instead of double gasketing, I’d recommend identifying, and addressing, the root cause of any sealing issues.
This may involve:
1. Choosing the Right Gasket: Selecting the appropriate gasket material and design, based on the application requirements, such as temperature, pressure, and surface condition.
2. Surface Preparation: Ensuring that the mating surfaces are clean, flat, and free from irregularities or damage, to ensure proper sealing.
3. Proper Torque Application: Using the correct torque values, when tightening the fasteners, to achieve the recommended gasket compression.

I remain, so far, unconvinced - but willing to be persuaded.

But you ignore Bowdrie’s comments that this isn’t a head gasket but somewhat flexible surfaces that aren’t 100% flat and smooth and also distort when tightening fasteners.

I have the exact same experience with this as Bowdrie and found using a gasket helper (helper indicates it isn’t an extra gasket) was 100% effective.

On the same note, some oil or grease on a rubber O-ring or the rubber ring of an oil filter is also bad and double gasketing? Try it without…

[GordMay]

Originally Posted by s/v Jedi

...
On the same note, some oil or grease on a rubber O-ring or the rubber ring of an oil filter is also bad and double gasketing? Try it without…

That's not an analogous application.

The oil film, applied to the rubber O-Ring gasket, of an oil filter, allows the gasket to slide, when first contact is made, and prevents creeping & distortion of the gasket, when it is [screw] tightened fully. Creeping & distortion can cause uneven seating of the gasket, and could result in leakage.
Otherwise a dry rubber O-Ring can grab on initial contact, when screwing it in place.
The oil, itself, is not a gap filling gasket [stacked gasketing]- it's just a lubricant.

[s/v Jedi]

Originally Posted by GordMay

That's not an analogous application.

The oil film, applied to the rubber O-Ring gasket, of an oil filter, allows the gasket to slide, when first contact is made, and prevents creeping & distortion of the gasket, when it is [screw] tightened fully. Creeping & distortion can cause uneven seating of the gasket, and could result in leakage.
Otherwise a dry rubber O-Ring can grab on initial contact, when screwing it in place.
The oil, itself, is not a gap filling gasket [stacked gasketing]- it's just a lubricant.

Okay, so my gasket helper is a lubricant as well

[GordMay]

If your gasket material needs a "helper"; you may have chosen the wrong gasket material, for the application.

FWIW: Vaseline is my Choice of lube, during sex.
I smear it on the door knob, so she can't escape.