Ahh, Indeed Senor Dennis.

I was more so refering to the thicker piece of plastic in the second part of the video. Where you only weld one side of it. (idk is this where the epoxy comes into play? the painted side?) either way, if you leave any part of the crack unmelted there will still be a crack underneath your freshly remelted fairing. the crack will be a weak spot.

 

The video was posted to show the process, but I admit that the one repair really isn't totally correct. If you v-groove the crack from the back then melt and add new plastic rod it would be better for sure. In order to not cause to much damage on the finished side it's best not to penetrate all the way through the crack. I try to stay just below the surface but it takes practice and timing to not damage the finished surface. If it is damaged it can be repaired. JB weld can be applied to the finished side to strengthen and fill the crack. Most of the repairs that I have done, just a good sanding and a little spot putty or body filler is all that is needed to finish the crack for priming.

 

ive used this process on BOTH sides of cracks before (f3 tail fairings) Filled the v grooves with jb weld on both sides, and then smoothed out with fiberglass bondo. It WILL re-crack if it is a stressed area. total waste of time

 

Which process are your talking about? If you filled v grooves with JB Weld only, then filled, that will not produce a strong enough weld to the crack. Prep is important also. surfaces needs to be clean of paint and oil and roughed before welding. Virgin plastic without contaminants. Adding more new ABS plastic into the joint is also important. With the right temperature and technique melding the plastic with heat will produce a very strong joint even on stress points and mounting holes.

 

the process in the video that you posted..spot welding the crack, grooving it, backfilling with the plastic from the grooves, adding jb weld into whats left of the groove (plus more), layering fiberglass bondo and sanding smooth..broke within months. this was done on both sides of an f3's tail fairings.. where the fairing bends back to the tail is a weak point and almost all f3 tails break there..