I spend inordinate amounts of time discussing the pros and cons of acrylic and polycarbonate. In so much as I would like to bring some clarity to this issue. Please consider the following:
- All major hatch, portlight, and window manufacturers use Acrylic in offshore / bluewater marine products.
- Acrylic is more scratch resistant than standard (9034) polycarbonate.
- Acrylic is significantly more durable when exposed to Ultra Violet radiation (sunlight).
- Acrylic is less expensive than Polycarbonate.
Don’t misunderstand my preference for acrylic. I buy, use and sell a significant amount of both products and each has its application. In my humble opinion Acrylic is more durable, versatile and cost effective in the hands of a skilled craftsman than polycarbonate.
Additional considerations may include polycarbonate with UV and scratch resistant coatings. While these products are heavily promoted by several manufacturers and carry 5, 10 even 15 year warranties the following information has been reported in “real life” applications:
- Polycarbonate is impact resistant. When it’s new it is almost impossible to break.
- Small quantities (less than a 4 by 8) in gauges over 1/8th inch are difficult to find in the UV- scratch resistant grades.
- Colors are limited. Only two standards (gray and bronze). Try and find anything thicker than 1/4 in UV/ scratch resistant!
- Polycarbonate foreshortens when subject to static or dynamic loads. What this means is if you replace your hatch lens with polycarb, seal it and then step on it the ductile material will deflect (bow) in the center. One of two things may happen. 1st you will surely break the watertight seal, 2nd you may end up with a leg in your salon.
- As for the warranty: The original owner is warranted against failure subject to the material being submitted to the distributor for evaluation with the original invoice subject to actual replacement cost at the time of purchase. I guess this means they sell you a new square of material and apply the old payment to the new cost. How about the labor to fabricate the part, install it and sealant? Why take the chance?
Polycarbonate is a great material; The US Air force uses it for fighter canopies! I sell Polycarb to the USCG and US Navy. Remember they don’t mind using it because we are paying to replace it every three years.
Both Acrylic and Polycarbonate have specific uses and installation requirements.
Cast Acrylic (of a specific thickness) is in accordance with CE and ABYC guidelines, and installed on virtually all of the big blue- water sail boats produced on both sides of the pond. Polycarbonate is commonly used as a replacement due to its ease of fabrication and incredible initial strength. The USCG and USN require Polycarbonate on their vessels but they also have a preventative maintenance cycle of 36 to 42 months for change out. My Tax dollars at work…
Due to its ductility Polycarbonate it is more challenging to install. I have seen Sika Flex 295UV with primer and Dow 795 both mentioned. I use and recommend both. Dont go over 4 ft continuous length with a fixed portlight. Remember the coefficient of thermal expansion for Acrylic and Polycarbonate is in the neighborhood of .000039 per inch per degree F. That means an 8ft plastic port will expand and contract up to 1/2 of an inch from the coldest day in Feb to the hottest day in summer. WOW!! Compartmentalize the job. It will be easier to install and less prone to leaks.
Never ever bolt a plastic portlight in place. Screws are fine to hold a lens till the adhesive cures. Take them out asap and fill the holes with the aforementioned products. Both of these products are rated at 700 + percent elongation before tear. Strong flexible and UV resistant.
Been to a boat show lately? Seen any screws? Glass is good so long as your boat does not twist or torque. Show me a fiberglass boat that does not twist and I will show you a cocktail barge tied to the dock”.
This subject always cracks me up…
Listen guys……. crazing in acrylic is caused by either thermal or mechanical stresses imparted during production, transport, manufacture or in use.
Acid rain,Ultra – Violet degradation, Windex or the boat detailer’s magic deck cleaner (to name a few) accelerate the process.
Once something is crazed it is significantly weaker than the same part in factory OEM condition.
How do you stop it? Make Sunbrella covers (not vinyl backed Sunbrella!!). Use cleaners specifically designed for Acrylic.
How do you repair it? You don’t.
We have all seen the lotions and potions sold at boat shows to cure everything from warts to your crazed hatches. You still have the warts don’t you?
You can follow the military specification procedures from the USAF/USN and sand the lens until you are below the crazed line, sand again in successive grits and buff with 4 or 5 different compounds until clear again. Remember annealing? Yea…. you need to get the mechanical and thermal stress you just put in with the sanding and polishing out! Well at 170 degrees F for 12 hours (1/2 inch acrylic) and cool down at the same rate, oh and now you’ve found the seal puddled in the bottom of your wife’s oven and the parakeet is dead from the MMA vapor being out gassed during the process. New seal, new oven, new wife?
By the time you have completed this repair you could have purchased two hatches, thrown one overboard and had the most expensive yard in the States install the second with the gold plated rag-surcharge and be ahead of the game.
I repair thousands of hatches every year. I know replacing the lens is an option but repairing the crazing with potions or flames is not realistic.
Let me know if you want some pictures of really crazed hatches. I have seen every make and model you could imagine.
I would like to help. But even the Hatchmasters can’t make crazing disappear. (yet)
This is the solution you Catalina, Ericson and Beneteau owners have been looking for.
HatchMasters in working with the industry leaders in plastic and rubber extrusion technology is pleased to announce the introduction of the “new and improved” Lewmar Old Standard portlight seal. The availability of these seals coupled with HatchMasters lens and manufacturing capabilities have given us the tools we need to re-build even the most damaged Lewmar Old Standard fixed port.
The process is easy. Remove your old crazed and leaking portlights and send the entire frame to HatchMasters. Our master craftsmen will disassemble and clean your unit’s inside flange and lens sealing area. A new Lewmar approved marine grade acrylic lens and seal will be installed. The entire unit will be re-assembled, checked and shipped back to you.
It is advisable to clean or remove all silicon or bedding compound from all portlights sent in for repair. HatchMasters will add an additional charge to clean the sealing flange on your portlight.
This is not a typo… your unit repaired, sent back, as good as new. NO cutting into your boat or making do with another manufacturer’s model that almost fits……
We have been working on this solution for over five years. This is what you have been asking for.
The product development team at HatchMasters has been listening.
Give us a call at 203-866-3767 to discuss your unit.
I hear the question as to which sealant to use when bonding Acrylic or Polycarbonate to aluminum, stainless or FRP over and over and over…..
Well here goes… The only three adhesives I would consider using are Sika Flex 295 UV with the primer, GE SG-4000, and Dow 795. Using the correct adhesive is only 1/2 the battle. Do not apply the sealants below 50 degrees F. The temperature must maintain at least 50 degrees F during the entire 21 day cure cycle. Cut this corner and your finished before you start. Preparation of the bond area is also very, very important. DO NOT TOUCH THE BOND AREA WITH YOUR BARE HANDS! Contamination from the dirt and skin oils will make a solid cure impossible. You may clean the FRP and metal with acetone to prep the area but if you touch the Lexan or Plexiglas with harsh solvents you will ruin the portlight. A 50/50 mix of isopropal alcohol and distilled water will work well to clean the plastic if needed. Remember that clean enough is not clean enough.
Re-introducing the Lewmar Superhatch hinge repair kit.
This kit will eliminate the old style Superhatch from falling and whacking your hand.
Kit contains new followers, snubbers, hinge pins and washers.
Plenty in stock. We made a boatload. Call for more information or see the Lewmar section of the web site to place an order.
You asked and we listened. The HatchMasters Product development team strikes again. !
Year after year I get the same question….
“My hatch is fine, it just drips occasionally. I don’t want to go to the trouble of sending it in for a complete service. What other options do I have?”
You asked, and we listened…….
Select Plastics product development team proudly introduces “Lewmar Leak Stop Kits” .
We have put together the correct parts to eliminate water infiltration through handles and friction caps for Lewmar Hatches and Portlights manufactured since the 1980’s. These kits have the handle seals, friction seals and lubricant you need to stop those annoying drips. All materials are the same “marine” quality we use in the rebuilding process at the factory.
You may ask: What size kit do I need? NO PROBLEM…. If you are not sure send us a picture of your hatch and we will link you to the correct part.
These kits were introduced last year at the Newport and Annapolis boat shows to rave reviews. They are flying off the shelves. Don’t miss out; get a few sets for your spares / offshore kit now!
HatchMasters is making boating safer one hatch at a time.