Re: Biaxial-traxial vs 7715 Fiberglass #epoxy


One Sky Dog
 

Hi,

I worked as an advanced polymer composites manufacturing engineer for over 40 years. I would advise that meticulous following of the layup plans and removing excess epoxy with the squeegeeing per instructions will yield good results.

Vacuum bags introduce literally tons of forces, many times acting in unknown directions. Your critical airfoil surface may move into something else.

The tri-axial was supposed to be the cats meow. In practice when rolled for shipping and unrolled on the layup the 0 degree fiber bundles buckled and made the surface much rougher than cloth layers. I used it once that was enough.

Regards,

Charlie

On Oct 17, 2020, at 3:20 AM, Rob de Bie <robdebie@...> wrote:

Regarding vacuum bagging, I would be very careful with that too. Full vacuum will compress your foam core, which could lead to a smaller core and wrinkles in your layup. Maybe a partial vacuum will work though.

Rob

At 05:51 17 10 2020, you wrote:
Use the layup schedule that is shown in the plans. It was carefully engineered. and is proven.
From the questions you are asking it is clear that you are not familiar with the purpose of different weaves. You can read up on this in the composite education section of the plans, but even this does not qualify you to redesign anything, so I recommend you not try to change anything.
A roller will tend to wrinkle your fibers which is not good. if you are looking for a way to build it lighter without compromising strength, I suggest you vacuum bag your layups. there is plenty of material on the web to show you how to do this.
Cheers,
Jay
Sent from my Verizon Wireless 4G LTE DROID


Cody <cody.craig1985@...> wrote:

Which is actually of more benefit? 3 layers of unidirectional, or a sheet of woven triaxial? Or a sheet of biaxial with a sheet of uni? I was thinking the layup on my wings and canard could be better an lighter with the multilayer sheets instead of 3 individual plys. Sam Hoskins, I just watched your video on epoxy swipe method. I intend on incorporation of this method and another method of dabbing micro powder on a fresh layup to absorb excess epoxy and fill the gaps more efficiently. I also talked to one of the mechanics who work with me and he said the larger composite planes don't use squeegee much anymore. They use Teflon rollers. Has anyone here done that method as well? I'm looking to be efficient with my work and light in the end, mostly because I want a strong airframe. Could I also ask if anyone has an AUTOCAD file of the LS canard with the carbon spar, main wing and tail I could send to Mohr Composites for a final quote? I know at least one other person on here has expressed interest in getting some CNC hotwire work done. I'm hoping they'll help with a bulk discount or something. But if nothing else maybe just more motivation to cut some cores for us. Thanks in advance.







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