⛵️ Thermoforming giant acrylic windows - we finally did it! Ep 679

Added: 2026-05-19

[00:00:12]Hi guys, welcome back aboard good old Spiffy, our 44 ft hurricane damage DIY catamaran project boat. Over the last couple of months, I've been working on and off on being able to DIY these massive bent acrylic windows. It started by me building the largest aluminum box I've ever built and turning that into a 6,000 W electric oven. After that followed lots of experimentation to get acrylic to thermopform without even any imperfections and without having it spring back as it cools down. Since then, I've used the cabin tub of the catamaran as a plug to pull a female mold. And then last week, I made the male version of that mold. It's been a long journey, much longer than expected.

[00:00:56]But I do think if we can pull this off, it is going to be worth it because a full set of these windows is about $20,000 and there's only material for about $2,000.

[00:01:08]If I'm able to pull off making these windows, not only will I get new windows for less than I could have bought them for, I'll also potentially be able to offer a costfriendly alternative to the Antar's community. As these boats get older and older, I think more and more are going to end up in the hands of DIYers that don't necessarily want to pay over $3,000 per window. This week, I am hoping we'll be able to form the first full-size window using this mold and a new out of the oven thermofformming process. But before we can do that, there's a little bit more work we need to do to the mold. We need to get a hinge on the back of it and cover it in some felt. And then we should probably do a little small scale test before we potentially waste a big piece of acrylic. The form is in two halves to make sure that the acrylic fully forms, but also to make sure both sides cool at a similar rate to prevent warping.

[00:02:06]Speed is going to be of the essence. So to make the form easy to use, I wanted to attach some hinges to the form. For that, I glued in place a couple of small pieces of 2x4. To get the two halves perfectly aligned, I started with the bottom, let that thickened epoxy gel to hold the 2x4 in place, and then moved on to adding the second piece of 2x4.

[00:02:30]While waiting for the epoxy to cure, I 3D printed myself little shelf brackets so I could move my muchbeloved epoxy mixing pump to a better spot.

[00:02:40]The only negative thing I can say about the pump is that as the temperature kind of fluctuates, sometimes a tiny drop of either resin or hardener will drip out.

[00:02:50]Rather than keeping a plastic cup under it, I decided to print some little caps with an interference fit.

[00:02:58]One of the reasons Ava and I brought Spiffy up here to North Carolina is because Marine Craft here is the North American hub for Antaris, which means this is where a bunch of repairs and upgrades get done, including replacing the very expensive acrylic windows. This right here is one of those acrylic windows. This is over $3,000 worth of acrylic window. Dave is replacing a couple of windows on an antaries out at the end of the dock sometime next week, I think. And I'm probably going to be allowed to help him out so that I can get some practice for when it comes time to replace ours.

[00:03:38]But I borrowed this one to check our molds. This fiberglass mold is the one we pulled directly off of Spiffy's cabin top. So this is a exact replica of the curvature on the cabin top. Or at least I hope it still is because if we look over here, what the heck is up with this gap here? There is about 3/4 of an inch almost 2 cm worth of a gap here. That seems weird.

[00:04:09]I've also tried comparing this to our male mold. And uh yeah, the gap is now here in the middle. And well, I can almost get my pinky in there. Dave, the owner of the marina, stopped by while I was filming this, and he told me that he has seen these windows deform before, especially if they're stored flat before installation, which was the case for this one. My background is as a software developer, right? So, I like it when things either fit or they don't. But according to Dave, the deformation, it doesn't really cause a big issue during installation or afterwards. So perhaps I just need to get over the fact that this is the real world and not software and things can be kind of a fit and still be okay. I would definitely have felt better if we had dropped this window here onto our molds and it had been a nice snug fit because that way we would know that our mold is accurate, but clearly that's not the world we live in. I knew that building the oven and learning how to thermopform acrylic was going to be a little bit difficult and take some time, but I vastly underestimated how difficult it would be to build the freaking molds.

[00:05:25]Yeah, let's uh bring this one back to Spiffy just to make absolutely sure it's still a perfect snug fit and then we can move on. We get almost all of our deliveries dropped off here at the CNC workshop. For instance, this is all of the epoxy and fairing compound for the upcoming cockpit rebuild project. But we're not here all the time. And when we're not here, it'd be great to be able to keep an eye out for any deliveries.

[00:05:52]We'll do that using the brand new all-in-one solar flood light cam from Riolink, the sponsor of this week's video. The RioLink Solar Flood Light is an all-in-one solar powered flood light security camera designed to both provide a,000 lumens of light and reliable surveillance with its 2K camera.

[00:06:11]Installation is super easy because the camera is 100% powered by its solar panel and communicates using Wi-Fi, so there is no need to run any cables.

[00:06:20]Installation is hassle-free and with no cables, you can mount it almost anywhere. The solar panel is permanently attached to the top of the camera, but in case you need to install the camera somewhere with no sunlight, you can also connect a separate solar panel. The camera has a built-in battery that can power the camera during the night and during gloomy days, extending its runtime up to 3 months. The flood light is just what we've been missing here at the workshop. The shipping container is located way out in the sticks where there isn't really much light pollution.

[00:06:53]So, it gets really dark at night and we didn't have any exterior lighting. So, whenever I left the workshop late at night, it would feel a little bit like stumbling out into a black void. The Real Link Solar Flood Light Camera has fixed that issue for us. A really cool feature is that the flood light has adjustable brightness and color temperature, making it easy to dial in not only the amount of light, but also the temperature, so it matches your other outdoor lights. The solar flood light cam also has two-way talk and a super light siren in case you need to deter the hamburger's off-brand cousin, the beef thief, from snooping around.

[00:07:28]For us living out here in the middle of peaceful nothingness, security is not that much of a concern. But I love that I now get a notification on my phone whenever we get a delivery and also that at the same time now have a super bright powerful exterior light for the workshop. If you're looking for an outdoor security camera that is easy to install, reliable, and works straight out of the box, you should check out the Real Link Solar Floodlight Cam. There's a link down in the description. Thank you so much to Real Link for sponsoring this week's video. A quick little check of the mold or form showed that it was still 100% accurate compared to the actual cabin top of the boat. So, that's good. Unfortunately, today it's going to be raining all day. I'd hoped we'd be able to do the first small scale test with the new forms today, but uh yeah, that is just the reality of working outdoors. You are very much at the mercy of the weather. And that's one of the main reasons why we've been trying so hard to find a property so we can get a roof over the catamaran. What I can do today despite the unfortunate weather is to finish our forms here. So I can get a hinge to join the two halves and we can cover both of the surfaces with felt.

[00:08:38]From what I've heard and read, there are two approaches when it comes to a form for forming acrylic. It is either having a perfect mirror finish surface or you cover the surface with some kind of fabric or felt. This is 1/8 of an inch thick or about 2 mm. It is referred to as grade F1 felt. I got this stuff from McMaster. And uh yeah, it feels really nice and consistent and also there's not a lot of squishiness to it, which I think is exactly what you want. If you guys recall from my previous experiments, we used slump forming inside of the oven using these plaster molds. We used plaster because once the molds go inside of the oven, they have to be able to handle the temperature in there. And in our case, it's about 350° F or 175 C. Our new polyester and fiberglass molds or forms here are not going to be able to withstand that temperature. They're going to start drooping and be inaccurate. There are a few reasons why I've decided to try and switch to outside of the mold forming rather than inside of the mold. For one, these plaster molds, they're really easy to work with. It's an easy material to work with, but they are pretty freaking heavy and also they're fragile. For smaller windows, I think they're perfect choice. But for bigger windows, they get really, really heavy and they're fragile at the same time. I think that's a dangerous combination. When it comes to thermopforming acrylic, there seems to be many, many ways to get to the goal line. Both in terms of actually heating the acrylic. You can use infrared heaters over a suspended sheet of acrylic. You can use a giant oven like I'm doing. That oven can be powered by electricity or propane. And also in terms of actually forming the material, like you can do it in oven like I've done. You can do it outside of the oven.

[00:10:35]There's also a bunch of different materials you can use for your forms. So yeah, I think there's no one best way of working with acrylic. One of my sayings has always been if somebody's trying to tell you that there is only one way of doing something and that is the one only true way for everybody and the way that everybody should be doing it, they're usually wrong. And uh I do feel like that's true for the acrylic thermopforming stuff too. I feel like I can say that about thermopforming even though I haven't formed our first full size successful window yet because I've talked to a bunch of different people that have very different approaches to thermopforming acrylic. And these are all for thicker acrylics like the stuff I've got here and and even thicker. So example number one is Stain from Denmark who's been working with thermopforming acrylic his whole life and he makes uh the windows for the Dragonfly multihole boats which are really cool boats. He does it using a process that's very similar to what I want to try here now.

[00:11:35]And in fact, he is the inspiration for that method where it is outside of the mold forming. He uses plywood for his forms covered in felt or carpet just like I'm trying to do. And then on the other hand, we have Nick and his son that have successfully modeled their whole deck in CAD based on some really cool technology. And they've then used that CAD model to CNC a form out of CUSA board that they're going to use for inmold forming of the massive bent acrylic windows for their catamaran. So those are two very different approaches and that variety has been part of what's made it fun to dive down this acrylic forming rabbit hole. Anywh who, let's uh get these forms finished and uh start crossing our fingers. I had a couple of imperfections where I extended the mold, so I got those sanded out. Now, for adhering the felt to the mold or form surface, I'll use some of this high temperature resistant contact adhesive I used for the headliner aboard Athena.

[00:12:41]Then there was just the small matter of adhering the felt to the form. Or so I thought. Welcome to Crease City Population 1.

[00:12:54]for fenny Hel.

[00:12:58]If you're somebody that ships out fabric or anything that can crease, ship it rolled, not fold. That's always been a pet peeve of mine. It is so freaking frustrating to get stuff with creases in it. Like for instance, with this stuff, once I get that contact adhesive stuff on here and I get the two surfaces smudged together, that ain't coming apart again. So, if I end up with a crease, that's going to be a nightmare.

[00:13:24]If I had an iron or some kind of steamy thing, maybe I could get the creases out. I do not own any of those things.

[00:13:30]And also, I don't feel like that's really my job. They should have shipped it, rolled, not folded.

[00:13:36]My master's going to send out new felt.

[00:13:38]Should get here tomorrow, but that means I'm out of luck for today.

[00:13:44]24 hours later, I had a lovely piece of rolled felt courtesy of McMaster. There were no wrinkles or imperfections. It was perfect.

[00:13:55]This contact cement is specifically meant for spraying. So that is what I did. I applied adhesive to both the mold and the felt and then smooshed the two together. It was surprisingly easy to get the felt to be nice and smooth.

[00:14:12]With both of the halves covered in felt, I place some small spacers on the bottom half to get the right spacing between the two halves. For hinges, I used these things. These have a removable pin, so if I ever need to separate the two halves, that should be a little bit easier. And these also have bearings for a nice tight action without much wiggling.

[00:14:35]Taa, one finished form. This thing is uh getting pretty heavy, almost too heavy to comfortably lift as just one person.

[00:14:44]Hopefully, this thing works in the real world. To figure that out, let's start with a small scale test. When I uncovered the oven, unfortunately, I found out that the tarp has been leaking. I am not a big fan of working on projects like this outdoors. Anywh who, for the full-size window, we'll need a piece of acrylic that's roughly 80 cm high. Unfortunately, I did not design the oven for hanging acrylic like stain does. So, we're a little bit short on height. Rather than rebuilding the oven or modifying it, let's see if we can use the top heat and a clean sheet of aluminum without getting any imperfections in the acrylic. The crucial aspects here are going to be temperature and time. From previous experiments, we know that in slump forming, the acrylic starts to do its thing at roughly 125° C. Now, this is still a little bit too stiff, but I waited a little bit longer and here we are at 120 and it feels a fair bit more pliable. Now, it's probably still a little bit too cold, but let's give it a go.

[00:15:54]This test did end up warping back a little bit. Based on previous experiences, I know that happens when the acrylic doesn't get hot enough. But as you can see here, we still picked up the overall shape and there were no imperfections in the acrylic.

[00:16:09]We ran out of time for testing yesterday, but that's okay. I'm feeling almost certain that this will work. So, I've cut the first full size blank. This is slightly bigger than the final window. So, we'll form this and then afterwards, we'll trim it to the exact size. I really hope we can pull this off because I would much prefer to be able to hang the acrylic like stain does because that way you're basically guaranteed not to get any imperfections.

[00:16:37]You're also heating both sides equally.

[00:16:40]But I would prefer not to modify the oven too much. So yeah, let's cross our fingers this will work. I'll need a second pair of hands to lift the acrylic once it comes up to temperature. That was the perfect excuse to hang out with my friend Noah. While I got busy connecting the oven and cleaning it in hopes of not getting any surface imperfections on the acrylic, Noah did the surface prep on the sheet of aluminum. We're going to put the acrylic on. If we are to have any chance of pulling this off, it is crucial that the aluminum surface is 100% smooth and free of any contaminants.

[00:17:19]While carefully peeling back the protective film on the acrylic, we saw grains of dust and plant debris getting pulled up onto the acrylic from the static charge. But with great patience, we got every little speck of dust removed and loaded the acrylic into the clean oven. For this run, I'm only using the top heat in the oven, so it's going to take a fair amount of time to get the acrylic up to 145°.

[00:17:44]That was the perfect excuse to sit around and do some high quality gammering. After a couple of hours, we were around 149° C, which is the lower end of the acceptable range for thermofforming acrylic. And this very hot, floppy piece of plastic is why two pairs of hands is a good idea.

[00:18:06]While we were waiting for the acrylic to slowly cool, Ava brought all of us sandwiches. # bestwife ever. To trim the acrylic to size, I'll use a plywood template and a flush cutting bit on my trim router. Having cut the template with my jigsaw, I then used a little bit of 80 grit on a Dura block to smooth out the slight wobble in the jigsaw cut. I'm happy to report that the acrylic formed perfectly. There was no spring back and no surface imperfections. I used a little bit of double-sided tape to secure my plywood template to the acrylic and then set to work trimming the acrylic. All that was left now was a rocky style run up the steps to do a quick little check to see if the window was both successfully formed and trimmed.

[00:18:55]Woohoo.

[00:18:57]It's been a lot of work. It's been a lot of trial and error. It's been a lot of learning new stuff. But we have finally arrived at the first successfully formed and successfully trimmed full scale window. Heating the acrylic in the oven on that sheet of aluminum. It worked and we didn't have a single blemish or imperfection. So it definitely worked, but I can certainly see why it would be better to do what stain does and that is to hang the acrylic so you are completely immune to any kind of imperfections and stuff like that.

[00:19:32]But for this one, it worked. I think seeing that we have a successful window, before I tackle, especially the big curved ones, it might be nice to just build a little top hat thing for the oven so that we can actually hang the acrylic in there. But yeah, this was a great big success. I've been toying with a new solution for making the molds, which I think is going to be way faster, and that is to build it out of thin plywood with 12 mm plywood ribs to stiffen the thing. I think that is going to be a much quicker and potentially also better approach to the mold making because that way we can make the molds a little bit bigger. If I had one thing I want to change about what we did today, it was to make the mold just a little bit bigger so that we get a little bit more acrylic in there because the edge does seem to just have like some slight wrinkles in them, stuff like that. I know that's very common from what Stain has told me. So yeah, in the future we'll make the moles just a little bit bigger. I am overjoyed and relieved. And uh for the people that called me insane and said I would never be able to do this, there's this thing down below where you can leave a comment. You can like maybe type I was wrong. Something like that.

[00:21:02]>> Now the next step of course is to install the blessed window. And I want to make absolutely sure you do that the correct way. Fortunately, Dave, the owner of the marina, is replacing, I think, something like three windows on Antar's next week. And um he's offered me to tag along so I can learn how he does it. He's done a bunch of them. So, definitely I could learn some some good tips and tricks there. So, if the weather cooperates, that is what we'll be doing next week. The reason why I'm so focused on wanting to install this window correctly is because the old one we had there cracked. It was installed by the previous owner and I think it cracked because he heated it with like a heat gun or something to to create the shape which I think will introduce a lot of tension in it. But no doubt actually using the right sealant, the right primer and enough of it is also very very important. So yeah, this window will kind of be my benchmark test. I hope we don't see this cracked in a year or two, but uh yeah, I'm sure we can learn a lot of good tips from Dave next week. And on that cheerful note, I will end this week's video here. Hope to see all you guys back here in the yard next week for yet more DIY. As always, feel free to leave a comment down below. And don't forget, if you've enjoyed this video, >> please remember to leave a like.

[00:22:18]>> See you.

[00:22:20]>> Who was it who doubted them? Okay, no more Miss Ava.

[00:22:25]I'm ready to throw down.

[00:22:27]>> Okay. Okay, calm down.

[00:22:30]>> Hold me back. Hold me back.