We are looking to create fiberglass skins that are used on boat t tops for sun protection. The idea is to retrofit the skins onto existing tops to replace canvas, and to sell to t top builders as an up sell to customers. Essentially the skin will be an approximately 1/8" thick sheet of fiberglass. Glossy gelcoat on one side, and then a rolled on gelcoat “non skid” texture on top. We are planning to infuse the skins on a glass layup table. The table will be 96" x 96". The skins themselves, approximately 60"x84". What would be a cost effective and durable layup schedule to achieve such a part? Thanks in advance for reading my first post!
Theres quite a few options you could look at here, but I guess cost is your main concern here, so whatever you can get your hands on fibreglass wise will be a good starting point. At 1/8" there’s hardly any point using a core material if it needs to be quite durable for repeated impacts so likely go with a monolithic laminate of fibreglass. For 8ft x 8ft, you will likely want as much woven material in there as possible. What woven cloth have you got access to?
but with a core material you’d get excellent stiffness with little glass needed. For this sort of application you can get end grain balsa cores which are fairly economical. then you can use less glass/resin. Plus reduced layup times. If you price it out you might be better off with less glass/epoxy. It’d be worth a test panel or two. the core is for rigidity more than anything.
Thanks for your responses. I have access to 3/4 Oz Mat, 1.5 Oz mat, 1708, and a unidirectional weave of similar to 1708 but a little heavier. (buyout roll)
The parts we are making are simply for shelter on a boat “t top”. They are replacing canvas. The requirements are: glossy white on at least one of the sides, uniform thickness, bendablilty to curve with the t top, durability in high sun high heat environment. We are also open to recommendations of resin. Cost is a factor (as always). We are using this project to experiment with and as a basic part as a first infusion.
The biaxial stuff is good, but kinda harder to infuse. Same with the chop strand mat and the unidirectional. They’re generally more difficult to infuse, as there are no flow paths. Again a core would help with this. You can use something like soric or 3d core, that has build in flow channels, or use foam and score and perforate it. I think there are other interlaminar flow media available, none that I’ve tried.
again you should make some test panels. I’d probably make a thickness gauge first to so you can measure what the various materials will actually give you in a final part. Infuse each material separately. Do like a 15 ply stack and step each ply back 1.5. You’ll end up with a piece that is 1 ply thick on one end and 15 on the other. Then you can mic it and know what you’re dealing with. ALso give you a sense of how flexible or stiff the various materials will be. Plus you’ll get practice on the infusion and see how the flow is in the differnt thickness.
Infuse on the short end of the piece. The infusion alone will be a bit of practice if you’ve not done it yet. ALso you’ll probably want to test the resin as well.
I’d vote on epoxy resin for the resin, it’s generally the best. more expensive.
You can probably do polyester, vinylester for sure. The esters can off gas, which may not be a problem. ALso the the esters can have a lower tg and could probably use some longer term curing and maybe a post cure. But I guess boats are made out of it and they do fine in the sun. Plus with the esters you can use gelcoat, which can be sprayed on vs. troweling on a top coat.
again if cost is a factor, you need to do all of the calculation on the various materials to see which material setup will be cheaper. Then add for vacuum bag, lines, and all infusion stuff, plus wastage from the infusion. wet layup might be cheaper in some ways. I guess it depends on how many you’re making? If you’re doing a lot, you can also make a reusable vacuum bag to cut out expendables costs.
I never have trouble infusing multi-axial glasses, I infuse a fair bit of quadaxial and triaxial, and a bit of biaxial. Haven’t had an issue yet. Chopped strand also infuses ok, but it prints quite badly.
Also vinyl ester infusion resins are likely to have a slightly higher Tg than your average epoxies. Most will take around 100-105 C, whereas most ambient cure epoxies will be under 95 even with a post cure.