Welcome aboard matey !
I built the same model a couple of years ago and found it an interesting build.
First sailing trials and I sank her
However, I managed to recover her intact, dried out the electrics and tried again the following week. She survived this time and my analysis of what went wrong the first time was quite simple - 1. I had the battery sitting too high in the hull (did this for ease of access) which made her a bit top heavy. 2. I had the sail fully rigged and the breeze put her over on her beam ends. This allowed water to enter the hull via the cut-out for the tiller rod and through the main hatch. Also, because the battery wasn't secure, it shifted and contributed to her inability to come upright.
Simple answer - shift the battery as low down in the hull as possible and secured and lower the sail so the wind doesn't push her over.
Sorry I don't have any photo's of the build, nor any of her completed. I will endeavour to get some photo's next Sunday and post them on here if I can.