Posted: Tue Mar 25, 2014 5:16 pm
Hey Fellas,
It's been awhile since I've been on here, but after hitting another issue during wet layup, I figured I'd share my issues with the experts to troubleshoot. The issue is the top sheet/fiber layer de-laminated when I tried to remove from mold. The epoxy seemed brittle and the fiber didn't look completely wet out even though I used *what i calculated* the correct amount of epoxy (~24 fl oz).
Basic info:
-Construction: top sheet (UHMW), 19 oz triaxial, shaped poplar core w/ attached sidewalls with tip/tail spacers (UHMW), 19 oz triaxial, base layer (UHMW) with attached edges
-Epoxy: ECA0043, and ECA-408 hardener (4:1 ratio)
-Process: Vacuum bag (mdf female mold)
-Total qty of epoxy = 24 fl oz (does this jive with other people's calc's?)
-Layup cured w/ vacuum on for ~14 hrs, then I allowed to sit at for another day in the mold without removing
-I used carpet tape on the base layer to prevent movement during curing
-Room temperature cured (this I think is where the epoxy and I had a falling out)
Good news-
1. The overall process/assembly went pretty well, other than alignment of core to base layer. I used the method of super gluing 2 inserts on the base layer prior to layup, then during layup using an exacto on the first fiber sheet to cut out around those inserts for clearance. This sounded way easier than it turned out...anyone have any advice as to how to keep the fiber from fraying during this (or is that even an issue?)
2. MDF mold held up well, vacuum pulled almost 1 atm; I used peel ply, breather cloth, bag with mastik (spelling?) tape
Not so good news-
1. when I went to pull the assembly out of the mold, the top sheet and first layer of glass pulled up off of the poplar core without much resistance....no bueno! I have a few theories, and before I put together a formal design of experiments, I wanted to get some feedback first to make sure it's not something totally stupid I overlooked:
a. Ratio of resin/hardener was off: I measured by weight (~19.2 oz resin/ 4.8 oz hardener = 24 oz total).
b. Chosen harder/epoxy was not a good choice for room temp. curing.
c. I didn't allow enough time before trying to remove from the mold (epoxies are thermosets which rely on cross-linking...temperature and/or time are variables)
I will try to post some pictures of the process at a later time, but any insight/feedback is much appreciated.
Thanks!
Merritt
It's been awhile since I've been on here, but after hitting another issue during wet layup, I figured I'd share my issues with the experts to troubleshoot. The issue is the top sheet/fiber layer de-laminated when I tried to remove from mold. The epoxy seemed brittle and the fiber didn't look completely wet out even though I used *what i calculated* the correct amount of epoxy (~24 fl oz).
Basic info:
-Construction: top sheet (UHMW), 19 oz triaxial, shaped poplar core w/ attached sidewalls with tip/tail spacers (UHMW), 19 oz triaxial, base layer (UHMW) with attached edges
-Epoxy: ECA0043, and ECA-408 hardener (4:1 ratio)
-Process: Vacuum bag (mdf female mold)
-Total qty of epoxy = 24 fl oz (does this jive with other people's calc's?)
-Layup cured w/ vacuum on for ~14 hrs, then I allowed to sit at for another day in the mold without removing
-I used carpet tape on the base layer to prevent movement during curing
-Room temperature cured (this I think is where the epoxy and I had a falling out)
Good news-
1. The overall process/assembly went pretty well, other than alignment of core to base layer. I used the method of super gluing 2 inserts on the base layer prior to layup, then during layup using an exacto on the first fiber sheet to cut out around those inserts for clearance. This sounded way easier than it turned out...anyone have any advice as to how to keep the fiber from fraying during this (or is that even an issue?)
2. MDF mold held up well, vacuum pulled almost 1 atm; I used peel ply, breather cloth, bag with mastik (spelling?) tape
Not so good news-
1. when I went to pull the assembly out of the mold, the top sheet and first layer of glass pulled up off of the poplar core without much resistance....no bueno! I have a few theories, and before I put together a formal design of experiments, I wanted to get some feedback first to make sure it's not something totally stupid I overlooked:
a. Ratio of resin/hardener was off: I measured by weight (~19.2 oz resin/ 4.8 oz hardener = 24 oz total).
b. Chosen harder/epoxy was not a good choice for room temp. curing.
c. I didn't allow enough time before trying to remove from the mold (epoxies are thermosets which rely on cross-linking...temperature and/or time are variables)
I will try to post some pictures of the process at a later time, but any insight/feedback is much appreciated.
Thanks!
Merritt