Hi all, my first post on this site so a big hello to everyone! As the title says i’m about to start building a europa, a two seater composite light aircraft. I have no previous experience with composites but have got to learn. I will be vacuum bagging certain parts of the plane as they cure to ensure no voids or de-laminations. I have a couple of questions that id like the more knowledgeable to enlighten me. First the parts have a form core which i will put fibreglass on top of and wet out, will the layers then go in order of : peel ply, perforated sheet, bleeder then bag OR perforated sheet, bleeder then bag?
and second, once i do my lay up and wet it out do i leave any overhang of cut the fibreglass exactly to size? Thanks in advance
You can do either method, use peel ply to get a surface suitable for secondary bonding, painting or even just a better finish, or use just the perferated film to control your resin bleed and release your breather/bleeder. Generally you always leave your material bigger than you need and trim to size after cure. I dont exactly what you are doing so its hard to say. Regardless I hope you make many test panels before touching your plane. There are many variables such as fabrics, resin viscosity, temperature, perforation size, breather/bleeder wait, vacuum level, vacuum integrity…many more… Anyways good luck!
Do the construction specs specify that the laminate should be vacuum bagged? It’s a misnomer that a vacuum bagged layup schedule performs better. A vacuum bagged layup schedule will be thinner (and lighter) than the same schedule that is not vacuum bagged. This can effect the performance of the laminate depending on the application. In some applications this thinner laminate, due to its increased propensity to buckle under compression, will create a weaker structure.
Example: A 60 ounce/yard E-glass layup with just a hand layup is around .090" thick (Vf 35%). It could be thicker if you are inexperienced or are using bulky fabrics. If you vacuum bag it you could squeeze this layup down to .063" (Vf 50%). That’s a 30% reduction in thickness. Depending on the perf-ply, resin viscosity, and gel-time you could end up even thinner.
I would only vacuum bag an application if the design specifies that it should be done. I would think that they would also specify the target Vf% that they used when they designed it. You could generate test panels to determine if your bagging processes are getting you close to the design target.
Vacuum bagging is a great tool but the user needs to understand the structure and effects that the vacuum bag will produce.
If a Vf is not specified, perhaps a laminate thickness, or a laminate weight or resin usage is specified. These could all be worked back to a Vf, and a contruction method.
First post. Welcome.
Building a plane. Cool.
Never worked with composites before. Parachute.
hahahah ^^^ so funny!!! Indeed if it’s your first time working with composites it may not be wise enough to built a plane…no offense but I would begin with sth that rolls on land!