Hatch cover: acrylic or polycarbonate?

[N.A.]

Hello folks-

Leaking deck hatch covers, need to reseal, and if doing that figure I might as well replace the plastic.

--> Is polycarbonate (e.g. Lexan) or acrylic best to use? Out of curiosity, why?

--> Do you have a favorite type, e.g. "grey acrylic #2064"?

--> I see no gasket on these... does anyone know if that is normal or am I likely to only discover something after I get the old lens out?

(PS looks like these (Bowmar hatches) are ~3mm thick... is that standard? These have reinforcing bars below them, and do feel thin (definitely cannot eb 1/2", as Christans's Lewmars seem to be). I am trying to guess without popping the old plastic out, figuring maybe I can have the new plastic ready and do it all at once...)

Much appreciated as always!

PS: If anyone else goes looking, useful links are:

Does anyone have hatch cover DXFs (laser files) for E30+ 1984 hatch acrylic?

Welp, my hatches are crazed. Not a serious problem but it's going to bug the perfectionism in me. I've spent enough time using laser cutters to know just how cheap and easy it is to cut a replacement piece of acrylic. As in, $20. I'll do the DXFs myself if needed, it's easy for me with a tape...

ericsonyachts.org

E381 - Thelonious II -- Main Hatch Heat Forming, Vetus Cowls

There have been several good hatch lens replacement reports lately. Rick R. takes on Lewmar Rollstop hatches here. I found this video adds a bit to the critical procedure of finishing the visible seam where the acrylic joins the frame. My older...

ericsonyachts.org

Great installation video (by Christian):

Says:
Bedding: Dow 795
Hatch covers (Lewmar): half-inch grey acrylic #2064. Unclear if originals may have been 12mm

 

[Christian Williams]

If possible take the old hatch lens to a plastics shop for exact duplication. Every community has such businesses, they make display cases for retailers, artist vitrines, picture frames and so on and have the gear to cut and drill accurately.

Acrylic (Lucite, Plexiglass) is cheaper, doesn't yellow in sun, doesn't scratch easily. Poly is lighter, harder, stronger, scratches, turns yellow over time. Most hatches are acrylic.

 

[N.A.]

Many thanks! Have friend who can cut it. Hoping to make it, then pop out old, install new all in one go, so don't have to rig cover for missing hatch for days during what is still the rainy season. Likely result: one wrong cover, followed by getting it right, but... here goes

 

[N.A.]

I got new acrylic made, and am almost ready to go... but trying to decide if I should use butyl rubber sealant (seems like what folks use in manufacturing?) or the Dow 795 (which I think is silicone, i.e. bathtub caulk with some filler added, which is vapor-permeable and I would think might mildew over time (as it can in a shower).

Any optinions/tuips on butyl vs silicone / Dow appreciated.

 

[Christian Williams]

Dow 795. In my world butyl is for deck hardware, there are better options for almost every other application.

 

[haytor]

I got new acrylic made, and am almost ready to go... but trying to decide if I should use butyl rubber sealant (seems like what folks use in manufacturing?) or the Dow 795 (which I think is silicone, i.e. bathtub caulk with some filler added, which is vapor-permeable and I would think might mildew over time (as it can in a shower).

Any optinions/tuips on butyl vs silicone / Dow appreciated.

Anything I remove from the deck that was bedded in Butyl, is hard and dried out like window putty, or plumbers putty...
Anything that used original Dow Corning Silicone still good...
The correct Silicone used to be Sil Pruf...spelling may be wrong, this Silicone was formulated to attach windows, to most substrates, and it was a glue and a sealant...
The Sil Pruf has been superceded and I have forgotten the name, but I glued massive windows in my previous 40 Catamaran and after much flexing and 20 years no problems..

 

[bigd14]

Anything I remove from the deck that was bedded in Butyl, is hard and dried out like window putty, or plumbers putty..

There are lots of products advertised as butyl that are worthless. Before I knew better I bought some at an RV store which was absolute garbage. Bed It Tape, developed by Maine Sail is the real deal and works amazingly well.

Bed-It Tape - The Easiest, Most Secure Way To Bed Deck Hardware

Bed-IT: The highly acclaimed tape for bedding marine hardware is back and in stock for immediate shipment. Forget the cheap glass and RV tape, get the best. Over 100,000 sold!

bed-it.com

 

[Christian Williams]

I doubt Ericson bedded anything in butyl back in the day.

GE Silpruf is a strong adhesive, which may be desired for some applications. Ericson portlights, however, don't need a strong adhesive and marine caulk is probably better and allows for removal.

 

[Loren Beach]

Ericson portlights, however, don't need a strong adhesive and marine caulk is probably better and allows for removal.

Good comment. Our opening ports (1988) had all been installed with 5200. (Along with all other deck hardware.) It took some heat and a bunch of scrapers/putty knives to get 'em off. A less-intense sealant might have been preferable, way down the road. That said, the 5200 was 97% still keeping water out, decades later. In general, EY did a better than average job of constructing our boat.

 

[Christian Williams]

On the 1985 32-3 it was caulk turned to dust, and the ports pretty much fell out when urged. Made it easy .

But the '84 381 has original caulk, I think, and I can't find a reason to rebed. It could be 5200.

 

[haytor]

There are lots of products advertised as butyl that are worthless. Before I knew better I bought some at an RV store which was absolute garbage. Bed It Tape, developed by Maine Sail is the real deal and works amazingly well.

Bed-It Tape - The Easiest, Most Secure Way To Bed Deck Hardware

Bed-IT: The highly acclaimed tape for bedding marine hardware is back and in stock for immediate shipment. Forget the cheap glass and RV tape, get the best. Over 100,000 sold!

bed-it.com

Well I would want to see a comment where deck fitting or windows were removed after 8 years or more...my take away is its good for production builds and easy clean up...but long term I'll stick with good quality silicone, polyurethane and polysulfides....for sealant glues and gaskets, 55+ years has shown me what lasts...

 

[haytor]

Well I would want to see a comment where deck fitting or windows were removed after 8 years or more...my take away is its good for production builds and easy clean up...but long term I'll stick with good quality silicone, polyurethane and polysulfides....for sealant glues and gaskets, 55+ years has shown me what lasts...

This is the product best for bedding or installing any window hatch application...

SilPruf™ SCS2000 Sealant | Momentive Silicones for Building

Ensure resilient, long-lasting joint strength in new or remedial applications with SilPruf SCS2000 Sealant.

siliconeforbuilding.com

 

[N.A.]

SCS2000 looks great -- hurricane glazing applications it says! -- but given that this is DIY I might try the 795 or 5200 with the hope I can fix it if I mess it up the first time... I'll report back after trying.

Thanks very much for all the information/comments -- definitely appreciated.

 

[haytor]

SCS2000 looks great -- hurricane glazing applications it says! -- but given that this is DIY I might try the 795 or 5200 with the hope I can fix it if I mess it up the first time... I'll report back after trying.

Thanks very much for all the information/comments -- definitely appreciated.

It is designed to withstand a HURRICANE, in a commercial setting, but that is only quoted to show how well it works!
It is as easier to remove than 5200 which is more of an adhesive, I have had layers of FG come off when trying to remove fittings bedded in 5200....
Good Luck with your project!

 

[JSM]

I got new acrylic made, and am almost ready to go... but trying to decide if I should use butyl rubber sealant (seems like what folks use in manufacturing?) or the Dow 795 (which I think is silicone, i.e. bathtub caulk with some filler added, which is vapor-permeable and I would think might mildew over time (as it can in a shower).

Dow 795 is the way to go. Its made to hold plate glass in window frames. Did my hatches with it 7 years ago with no problems.

 

[peaman]

This is the product best for bedding or installing any window hatch application...

SilPruf™ SCS2000 Sealant | Momentive Silicones for Building

Ensure resilient, long-lasting joint strength in new or remedial applications with SilPruf SCS2000 Sealant.

siliconeforbuilding.com

I have seen many statements advising against silicone on fiberglass because once used, it cannot be completely removed, and nothing else will stick to it. I don't have personal experience with that, but it seems to be a concern among many sailors. It may be ideal for sealing clear plastic in hatch frames, but not for bedding hatches or other things on a gelcoat/fiberglass surface.

 

[gabriel]

Anything I remove from the deck that was bedded in Butyl, is hard and dried out like window putty, or plumbers putty...

I second that. all the butyl I’ve used is cracked and dried out in less than 4 years. no bueno.

 

[Christian Williams]

Re butyl tape: I think it's safe to say that in the discussion of butyl tape here the most frequent citation is R. C. Collins ("Maine Sail").

Collins, now disabled by a stroke, saturated the forum worlds with extraordinarily detailed, even obsessive, articles on yacht maintenance, conducted a lot of original research and never took anything on face value. His tape is not really "butyl," he says, but a hybrid elastomer. His testing suggests that off-the-shelf butyl fails fast, for which he blames the EPA. He also claims to have sold more that 100,000 units of his "Bed It" tape, which I take as proof of a sense of humor.

Bedding Deck Hardware With Bed-IT Tape - Marine How To

Originally published December 2003 *Moved & Edited September 2017 Bedding With Bed-It Tape 5/20/2022 IMPORTANT UPDATE BED-IT TAPE IS BACK PURCHASE BED-IT TAPE Countersunk/Beveled Hole Over the years,

marinehowto.com

 

[bigd14]

Well I would want to see a comment where deck fitting or windows were removed after 8 years or more.

How about 7 years? A month ago I removed an unused deck fill at the bow that I had bedded in Bed-It butyl in late 2016 and it came off easily with the butyl like new and still perfectly stretchy and most importantly everything completely dry underneath. I also rebedded every bit of deck hardware on an E27 back in 2011 and the boat has not had any leaks whatsoever (I keep in touch with the new owners). I share your frustration with the other “butyl” products that are a complete joke. But Bed-It really works.

 

[fixntheboat]

Check out Tap Plastics. online.They or you cut... I bought smoked plexi.. 1/2inch ... As per sealant Jamestown recommended the Sikaflex 295UV for plex to wood, and 5200 wood trim to deck.