strong adhesive/epoxy
 

need a good strong but liquid adhesive/epoxy thanks Rob

These are what I use:
Two part epoxy-different set times and rigid
Gorilla Glue- caution of excess glue expanding when drying
Liquid nail-rigid wood connections
3m 5200- the marine standard

used 5200 on this before, but did not flow down far enough and failed after a while...so needs to be pretty liquid

There is a huge fiberglass place local to my in the Tampa Bay area, called Fiberglass Coatings. http://www.fgci.com/

They are super helpful and knowledgeable, i would just call them and explain application. I am sure they will sell whatever you need and maybe you can get it locally if you don't want to ship it.

If you are looking for a two part epoxy look at MAS Epoxies based in NJ.

what are you trying to bond? Remember epoxy requires a roughed up surface for proper mechanical bond. If you just trying to run down into a void the best you can hope for are the fill properties with little actual adheasion.