Looking at the Force 4 Chandlery catalogue on page 59, there are a range of antenna mounts that can be mounted onto a flat surface where they can then be secured in place with bolts, self tapping screws, or with pop rivets, but have you thought of using an aerial splitter? With a splitter you can use your existing mast head mounted VHF aerial for both VHF and AIS use. Depending on whether your AIS is just a receiver or whether it transmits as well will determine how much you need to pay for the splitter. If your AIS only receives and does not transmit, then one of the lower cost splitters also advertised on the same page will probably suffice and most likely would cost no more than going down the route of a separate AIS antenna. It would also save the trouble of having to run an aerial cable up the mast as well as trying to find a suitable method of fixing your antenna to the spreader where it is likely to be damaged by your Genoa as well being a possible source of damage to the Genoa. If your AIS also transmits, then you will need a splitter costing around £200 such as, for example, the Raymarine AIS Splitter 100 which I have and which has worked extremely well, and completely seamlessly since it was installed over a year ago.
