Replacing compound curve windows?

[catsketcher]

Originally Posted by Bowdrie

"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.

I don't necessarily agree - I have built a few boats and have put in a few windows - all of them were/are acrylic with 2-3cm overlap onto the cabin side. I reckon we are thinking different window styles - alloy frames and fitted windows would be a pain of a job - but hiding filler under a more generous fillet under the overlaps of an acrylic overlapped window is pretty easy once you know what goo to use - Fixtech 200.

If someone wanted to do this then they could use a high strength filler to flatten out the upper and lower surfaces. If the cabin is solid glass and thick then some shaving could be done. Shaving off about 2mm and adding epoxy could only be done up to about 6-7mm but that maybe enough for the OP. This would not be hard with a good epoxy and some silica. Then clear coat epoxy over it and then you don't even need to paint. Ensure you tape the cabinside to prevent glue from sticking where the fillet won't reach. If you do it well then you use Fixtech 200 and double sided tape to hold the windows on. 6-7mm of epoxy glue is very strong. If you are clever with the filler and the Fixtech all of the job could be under the black Fixtech used. I do this a bit when painting around windows. I paint right up to the fillet and then just extend the Fixtech fillet around the window later. It makes it look all factory finish. Otherwise you have to remove the windows when painting cabinsides.

I reckon if it was me I could fill upper and lower "eaves" of two say 800mm long windows in 4-8 hours over a weekend - with grinding, sanding, and filling and then sanding down again. The great thing is the Fixtech 200 and tape is excellent at dealing with imperfections and all the work is hidden under the black goo.

Then you have a simple curve window. Cut the shapes out of 6-8mm perspex, round the edges and then fasten with Fixtech and tape. Depending on the radius, you can get simple curves to work fine. It has worked well for me for decades on my boat/s. I have no skin in the game, but I reckon this would not be a deal breaker for me if the windows had low amounts of vertical bend. Fitting 4 metres of windows on both sides of my cat took about 5 hours last time I replaced the perspex. I paid only for the perspex, a box of Fixtech and a few rolls of tape - no one else was involved. The windows don't leak either. Mine are put on the way these guys did

https://www.mjsailing.com/installing...ss-deadlights/

I am seriously thinking of greatly reducing my hull side windows in my cat. I would like smaller windows to reduce solar gain and because I sometimes like to feel a little enclosed by the boat. It won't be too hard - but I did build the boat.

cheers

Phil

[JBP]

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.

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

That's what my thoughts were, does the window need to be one piece? Is there structural support where you could divide the window into sections? You could even add some support. My boat has separate windows but in later model years they switched to wrap around windows. The cabin structure was still the same, the wrap around was just for looks.

[Tupaia]

It can be done it takes a massive amount of time.

1. Template the inner surface of the existing window (3D)
2. Create a mould bigger than the window using the template (Frames with battens with a smooth covering)
3. Mark the edge of window on the mould.
4. Cut the material (cold cast acrylic) so that it exceeds the marks by minimum of 100mm on each side.
5. Heat the acrylic using a blow torch the sort used for putting bitumen on roofs. Keep the flame moving and constantly turn the material over to achieve an even heat. It can take 20-30mins to heat a 50cm x 75cm window. It will reach a point where it will go limp. Too much heat and you will get bubbles or distortion, too little and it will not drape. Practice makes perfect.
6. When the material is sufficiently pliable drape it over the mould and screw or clamp outside the window margin.
7. Leave to cool, overnight is best.
8. Mark the edges of the window on the material and the release it from the mould. (Masking tape works well and protects the edges).
9. With the material marked cut the excess material (diamond jig saw blade or correctly toothed blade, slow speed) Too fine and the acrylic will re-weld itself, too course and the material will chip.
10. You will now have a new window.

Sounds easy, it isn't. Took me 2 weeks working everyday to make 12 windows.

[Cloroxbottle]

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?


Answer: it cannot, easily or cheaply. Most fabricators will not be able to produce such a replacement. Having owned a monohull with a large windshield with similar characteristics I added the presence of this sort of acrylic as a reason not to buy a specific boat.

[Leadfree]

Glass it over and install a hatch instead