fibreglassing advice?

[aquagee]

I am a novice, please advise. There are,as I mentioned, several thru hulls I need to glass over but one is puzzling me. It is where a depth sounder has been removed, The outer contour of the hull bulges out over a flat inner area of hull where the holes have been machined and this area seems to be at least a 1/4 inch thick, the outer hole has ragged edges. Does anyone know where and how would I begin grinding this to a 12:1 prior to glassing? Cheers

[sailingdog]

It would help if you posted photos. I would highly recommend you read the POST in my signature and go over to the Song Chain thread in the Off-topic forum and post 8 times there, so that you can upload your photos onto flickr.com or some other website and then link to them in your next post in this thread.