Fiberglass Phenolic Amraam4

[rvanstone]

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.]

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]

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]

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]

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

 

[rvanstone]

Missleman

Yes I am using the pumps and did use a 1 to 1 mixure.
So you are saying to use a 5 pumps resin to 1 pump hardener ?

Ron

 

[Missileman]

No no 1 to 1
Without the pumps it is 5 to one