Replacing compound curve windows?

[massnspace]

Thinking about buying an older cat that will need at least one of the windows replaced. Haven’t seen it yet, going to look soon…..

Question: It appears to me that the broken window has a compound curve (not just a bend in one axis). If that turns out to be the case, how in the world can that be fixed?

I have worked with plexiglass in my life quite a bit, but cannot understand how it could be bent into such a shape, without some very expensive tool built, and some type of way to heat it and conform it to the tool???

Boat make and model is not relevant to my question, but I will say that the manufacturer is long out of business, so not an option to “just call them.”

Ideas?

[skipperpete]

There’s an older cat berthed near me with large compound curve windows that have failed, the owner has them covered with some sort of plastic film (like the stuff used for car wraps) covering them completely while trying to arrange new ones from the manufacturer….. apparently very expensive. So far it’s been more than 6 months.

[leecea]

I remember a few years ago the YouTube couple "Gone with the Wynns" had to replace compound curve windows on their cat. They shipped the old windows to a place that had the capability to duplicate them. Unfortunately the first attempt failed because the new windows didn't fit, but they eventually got them fixed. The whole process was difficult and expensive.

[Wotname]

.......

I have worked with plexiglass in my life quite a bit, but cannot understand how it could be bent into such a shape, without some very expensive tool built, and some type of way to heat it and conform it to the tool???
.......[/QUOTE]
One method is to make a pressure tight mould to the required shape, heat the plexiglass, place in mould and use compressed air to 'push' the plexiglass into shape against the mould. The trick is to get the temperature and air pressure 'just right'.

[SV Confianza]

Would be best to list the make and model to get experience from other owners (if it’s not a custom cat anyway). The brand forums and Facebook groups have tons of active cat owners.

[skipperpete]

I know a guy who made the dome windscreens for crashed Robinson helicopters and he started by re inventing the process. The oven was custom made and because he’s a (famous in OZ) surfboard maker, the molds were works of art. The idea was to heat the sheet of either Lexan or acrylic in the giant pizza oven then drape the floppy sheet over the female mold and suck the sheet down with a vacuum cleaner. The shape was easy, no problem there….. but the domes were optically imperfect and this was a huge problem for a helicopter…..not so much for a boat. He tried different linings for the molds, pool table felt, various mold releases , male molds, heated molds, various oven temps, even correcting the imperfections with a gentle hydrogen flame ( which actually worked pretty well) but it was an expensive adventure. Far more rewarding was the surfboard side of the business.

[Tin Tin]

Just an idea. Make a fiberglass mold of the window. Then drape mold acrylic sheet or UV inhibited lexan (lower temp required) Will need a big oven The thermo forming part not really a DIY project. An alternative would be to make a fiber glass panel off the mold, then cut out the flat areas for dark tint flat windows or hatches. Paint the whole thing black.

[sailrjim]

For continuous multiple production, a mated core and cavity can be used with edge gated injection molding.

From earlier work in my career, one off and low small quantity/prototypes, three ways most commonly used to form thermoplastic sheet stocks are pressure forming as described above, vacuum forming as in liners for residential refrigerators, and two part mated tooling.

Pressure forming is good when sharp detail stands above the base surface; think words or logo. A two part mold, cavity and cover plate, is required and must have good edge seal between the two halves. This process is more dangerous than vacuum forming and a relief valve must be used.

Two part mated tools use a core and cavity arrangement. Both must be rigid. The core forces the softened material into the cavity and holds it there until cooled.

Vacuum forming needs a single sided mold and a clamp for the perimeter. Usually, fine detail is not practical.


As you can imagine, each method and which to use will depend on material thickness, thermal characteristics, and surface area of the part.


The need for optically clear surfaces complicates the tool design. Some of the cost will be in waste as some practice is required in the learning curve. Personal experience suggests that if the surface area is too large to be heated in your kitchen oven, then this is not a DIY job. I would seek a shop with previous success.

[Bowdrie]

Originally Posted by massnspace

Thinking about buying an older cat
Ideas?

You might think about NOT buying that cat.
How long will it be before one of the other windows need replacing?
There're untold thousands of boats for sale, don't get yourself locked into something that will guaranty unobtainable repair parts without spending a fortune on custom moldings.
If you can't let it go, then contact the organizations that restore WWII aircraft.
They make custom plexiglass parts all the time.

[Jim Cate]

You might think about NOT buying that cat.
How long will it be before one of the other windows need replacing?

You just saved me from having to type those very words! There would have to be some really strong reason to deliberately get stuck into such a difficult and expensive issue, one that would likely repeat before long.

Sad but true!

Jim

[Iron E]

Originally Posted by massnspace

Boat make and model is not relevant to my question, but I will say that the manufacturer is long out of business, so not an option to “just call them.”

Maybe it's just me, but it seems like the most relevant part of your question.

Originally Posted by Wotname

.......


One method is to make a pressure tight mould to the required shape, heat the plexiglass, place in mould and use compressed air to 'push' the plexiglass into shape against the mould. The trick is to get the temperature and air pressure 'just right'.

And use "Cast" Acrylic.

I've also made molds and just used multiple heat strips to achieve the results I needed.

[SailingHarmonie]

This is a mistake so many boat builders make. Those curved windows look awesome at the boat show, and invariably impress the non-sailing partner in the venture. But acrylic has a finite life in the outdoors, 10 years if you are lucky and shorter if in the tropics. We get about 7 or 8 years out of ours before visibility declines to the point we need them to be replaced. But these are helm station windows, and are all flat panels, so we change them at the first sign of deterioration, and it's not a terribly complex job.

Just a terrible case of the marketing department running the show to the detriment of the owners. They can be replaced from scratch, but the amount of custom work needed is HUGE, very specialized, and very expensive. It becomes even MORE so if the window is broken and can not be used to make a good mold. Hopefully the boatbuilder is still in business, AND the contractor who did the windows in the first place, AND they saved the original moulds, AND can ship them to you AND you can afford it.

Good luck.

[thinwater]

Originally Posted by massnspace

Thinking about buying an older cat that will need at least one of the windows replaced. Haven’t seen it yet, going to look soon…..

Question: It appears to me that the broken window has a compound curve (not just a bend in one axis). If that turns out to be the case, how in the world can that be fixed?

I have worked with plexiglass in my life quite a bit, but cannot understand how it could be bent into such a shape, without some very expensive tool built, and some type of way to heat it and conform it to the tool???

Boat make and model is not relevant to my question, but I will say that the manufacturer is long out of business, so not an option to “just call them.”

Ideas?

Post a picture. Otherwise just guesswork. It may not be compound. Or it could be like Stiletto cat, in which case they need to be vacuum formed. But we don't know.

[catsketcher]

It might be easier to replace both of the windows - port and starboard and make them single curved.
This would involve filling and sanding to make the edges line up straight with the top and bottom.

As stated above - you will need to replace acrylic so it may be okay to make the windows simpler. As said above if we knew the boat then we could check the amount of compound and work out if you can do it simpler.

But if it is a good boat and it suits then it could be good to stick at it. For me, there are only a few boats I could ever buy - I love multis with their shoal draft and performance, yet don't like many cats with their hard to see over cabins and inability to take the hard because of saildrives and non kickup rudders, so getting a boat that ticks these boxes is hard (but I already have the pretty perfect boat for me). So if I found one in a thousand I would see if I could make it work.

cheers

Phil

[Bowdrie]

Originally Posted by catsketcher

It might be easier to replace both of the windows - port and starboard and make them single curved.
This would involve filling and sanding to make the edges line up straight with the top and bottom.

"Filling and sanding"?
You're making it sound like a simple weekend job.
Changing the structural areas around the windows, building and glassing in new shaped sections, (that may require a fiberglass lay-up over a male mold or a female mold taken off of a male plug,) and then dealing with new window frames, or the rebated mounting surfaces, not to mention the finish work of gelcoat/paint is a big job for even a highly skilled tech.
And you want to do two of them?
That will require two sets of molds/fabrications that are mirror imaged.
The OP will need money, lots of it,,,and more.
And try to find someone who can make it look like it's a factory job.
And then you still have to get special shaped windows.
How many thousands is the finished job worth, 5? 10? 15? more?
Re-tooling parts of a fiberglass exterior is one of the hardest/most intricate jobs that techs do.