Fiberglass Phenolic Amraam4

rvanstone · Mar 31, 2004

First time fiberglassing.

I in the mist's of building Public Misssile ARAAM4 and have the Phenolic tubing.
Thursday I fiberglass all 3 sections using 2 oz Fiber and the West Systems expoxy. The directions called for 1 for 1 mixure of resin to hardener.
So yesterday I start to sand down the airframes , sanding them was pretty easy.

The problem is when I went to open the fin slots on the aft section, I had to cut a piece out using a exacto knife , the use a hack saw blade to cut down the rest of the slot.
The air frame simple cracked and a section between the slot s just simply snap off.

What possible could have gone wrong ?
The temp was around 75 degress when I started this .

Puzzle

Ryan S. · Mar 31, 2004

how big was the peice? I have had small peices of phenolic crack on me. You may have been putting too much pressure on it, phenolic would crack, but I think that would take alot of pressure

rvanstone · Mar 31, 2004

Ryan,

The piece is 12 in long with 4 7 in slotted fins.
I had also talk with Public Missiles there specualtion is that I had applied to much epoxy and that the expoxy had seep into the fin slots and damage the Phenolic tube.

This was the case . because I had to used a hack blade to cut out the fins.
They stated that I should be able to cut the glass at the fin area with an exacto knife.

Ron

Missileman · Mar 31, 2004

My experience with West Systems epoxy is that it tends to really soak into body tubes.
Perhaps the epoxy soaked tube had not cured fully and left this area weak?
I have cracked phenolic myself when trying to pry out a center ring, but it did take a bit of pressure.
Not sure what to do about a repair, sounds like a sizeable chunk is broke if I read you right.

Missileman · Mar 31, 2004

I re-read your post and have to ask.
You said a 1 to 1 mix?
Are you using the metered mini pumps to measure?
They are calibrated so one full stroke of each is a proper mix.
The actual mix without using the pump system is 5:1.
Had to ask