Hatch and lens restoration with wood

[trevoratlarge]

Hi folks. I bought my boat in April and the previous owner was in the early stages of refurbishing the hatches. I'm trying to finish the job myself.

I'd love any and all advice about materials and how to source them and best practices to make good strong hatches I can depend on in rough conditions and which will last.

Hear are some pictures of what I have right now:

Among my questions are:

What material for the lens? The former owner said polycarbonate but the internet seems to think cast acrylic is best?

Where's the best place to buy it?

How do I seal the lens to the wood frame? (i see some people use screws as well?)

How do I attach hardware to the lens? Do i need reinforcement?

How do I repair the screw holes in the deck fiberglass?

I posted a pic of the hardware I have, do a need clasps too?

What should I use to make hatch gaskets and what glue do I use for them?

Seems like I should probably just replace the wood? What kind of place should I get teak from?

I think I have the tools, will, and time to do this job, just not the expertise. I'd appreciate any help avoiding the pitfalls.

Any advice or diy explainers or whatnot are what I'm looking for.

Thanks in advance!

 

[PaulK]

Wooden hatches are tricky because wood warps when it gets wet. People try to use teak because it warps less. Howard Chapelle (Amazon.com : boat building howard chapelle) suggests arranging the pieces you use so that the growth rings in adjacent pieces cancel each other out. One board has the rings forming a dome, the next has them forming a cup.

 

[dLj]

The Internet is ripe with opinions - I'll give you one more - use as you wish. It will become clear I prefer polycarbonate...

Polycarbonate vs cast acrylic: years ago polycarbonate would degrade with UV quote quickly. Hence the preference to use cast acrylic. Modern formulations of polycarbonate are significantly better w.r.t. UV resistance so that old argument doesn't hold.

Polycarbonate has a higher coefficient of thermal expansion so in large applications that has to be taken into account - you don't have a large application. Your lens will not be 10 feet across (just a ballpark number to indicate large size).

The strength difference polycarbonate has over cast acrylic is huge (I'd have to go look it up, but orders of magnitude I believe).

Cast acrylic has a natural UV resistance so if buying polycarbonate you want a formulation that states UV and scratch resistant.

Cast acrylic is notably less expensive than UV resistant, scratch resistant polycarbonate.

I sail in the ocean. I use modern UV and scratch resistant polycarbonate. I changed all my hatch lenses to polycarbonate about 3 years ago, spent close to a year in the tropics since then and my lenses are still as pristine as the day they were installed. I did the same installation on a previous boat and those lenses have been perfectly clear now for about a decade.

I buy UV and scratch resistant polycarbonate from McMaster-Carr. I'm sure there may be less expensive sources but I don't know them.

dj

 

[BAD ORCA]

Search for 'acrylic fabrication' in your area or on the web. You will get better prices generally for large pieces from the folks that custom fabricate with it. Often they will sell it cut to size as well, or will cut it for you to a specific shape if you give them the original lens or send them a pattern.

I used cast acrylic for my hatches and Dow 795 to seal them in my aluminum hatches. Sika 295UV work very well also. Should work just as well on wood. It helps to mask off and sand the area of the acrylic or polycarbonate that will be bonded to the wood or metal with #220 sandpaper for a better mechanical bond.

I prefer acrylic, easier to work with, but either will do well in UV long term. Drill holes slightly oversize and mount hardware with machine screws through bolted. Small washers to reinforce on the backside and flat head screws with a countersink on the plastic do well and are easy to seal with a bit of sealant or butyl rubber. You can easily drill and tap plexi or poycarb also with standard taps if through bolting is not an option. Just be careful if you do, and absolutely do not use any thread locker on the screws into plastic.

Drill and fill holes in fiberglass with thickened epoxy. 'Marine How To' has an article i believe on this.

McMaster had EDPM gasket material in many profiles. Some have adhesive backing. Rubber cement work well if you get one that does not.

 

[Captain Larry-DH]

Acrylic is my recommendation. The only time I’d use polycarbonate is for a curved lens. In my experience polycarbonate sheets with “UV-resistant” coatings are still no more than half as resistant as acrylic. The only way to keep them clear long term is to use Sunbrella covers for them when the boat isn’t underway. They are also less scratch resistant than acrylic. I’ve had both more than 20 years (Acrylic more than 40).
One caution - NEVER use a window cleaner that contains ammonia on plastic. It causes crazing. Only use soapy water or cleaners that are specially made for plastic windows.

 

[dLj]

Acrylic is my recommendation. The only time I’d use polycarbonate is for a curved lens. In my experience polycarbonate sheets with “UV-resistant” coatings are still no more than half as resistant as acrylic. The only way to keep them clear long term is to use Sunbrella covers for them when the boat isn’t underway. They are also less scratch resistant than acrylic. I’ve had both more than 20 years (Acrylic more than 40).
One caution - NEVER use a window cleaner on plastic that contains ammonia. It causes crazing. Only use soapy water or cleaners that are specially made for plastic windows.

My current boat had cast acrylic lenses. At 40 years old they were totally crazed and cracked. One lens was cracked through to the point it was weeping rain water through it. With all due respect, cast acrylic does not last 40 or 40+ years clear and clean. In fact mine were structurally unsound at that point.

dj