It's simple, the cracks are because the plastic areas that endure the stress is too thin. Sending it back will do 3 things.
1. Get you a new shell.
2. Trim several weeks of the warranty of your phantom and remove it from your hands eliminating time you can fly.
3. Provide you with a new shell and the opportunity to repeat steps 1 & 2
Solution for $20.00 and the satisfaction of DIY.
Plast-Aid -
Plast-aid® multi-purpose repair plastic for your repair solutions.
I have applied it to all motor mount areas before I ever powered it up, Ok so I have voided my warranty, No biggie. All the parts needed for a repair or replacement of parts are available in the US anyway.
Reinforce the Mount areas with what I have found is just short of a Miracle product.
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There is no need to fear, the solution is here.
I just wanted to share with everyone the once and for all solution for $20.00
There is a fantastic product called Plast-Aid available from the manufacturer or on Amazon
This produce is a 2 part mix, it is not epoxy or glue. It is Plastic that is as strong as steel.
In fact it is so strong a piece 1/4 inch thick 2 inches long can not be broken by bare hands...
The components are a powder and a liquid. Pour powder in a supplied cup, pour in enough liquid for it to be saturated...
Stir it to mix well and pour it while it is still thin into the area of the motor mount so that it is up to the level of the mount base area.
Vibrate it by hand a little so the liquid plastic levels itself and flows into all the areas around the mounts.
You will have about 2 minutes before it starts to become thick so do it quickly.
Once it begins to become thick use a tooth pick to scoop up some and place it behind the body mount hole
to provide more bracing and strength. wait about 8 minutes and it will be like puddy where you can then press it into shape to refine the application as needed.
After about 10 minutes leave it alone and it will begin to get hot and start bonding to the shell material.
After about 15 minutes it will cool down and become hard as steel and totally bonded to your shell. It will at this point be part of the shell, not just
adheared like glue but actually part of the shell.
Over 100 flights and not one hint of a crack at all, not even the slightest.