Re: Tuna on the fly
Vans that sounds like you have all the makings of a great trip-- sounds like your father has it pretty wired as far as his experience both in terms of off shore boating and going after tuna specifically. The ocean is a pretty big place so knowing where to look for them is a big part of of it, as is advance planning and a bit of up to the minute researching of sea surface temp maps to get a sense of where to find clean water and 60 degree temp breaks.
Having good friends aboard will just add to the fun as they all participate in this adventure--
And having a few other boats along is always a good idea from a safety standpoint, but also can help everyone zero in on fish if you work together to cover more water.
How does your father usually fish for them? Does he troll using outriggers to find them? Then toss live bait to hold a school? Jig deep over structure?
Knowing how your father fishes for them can help develop a plan for catching them with a fly rod--
For example if your dad usually trolls and doesn't have room for a large live bait well on his boat, you might want to just use the starboard side outrigger (assuming you cast right handed), that way when you cast from port side corner of the stern you'll have some room for your back cast. If you think that you may just be be getting quick shots at fish, I would strip some fly line into a 5 gal bucket to keep it from flying all over the place-- that way you can pick up your rod and cast right away after you hook a fish on the troll and the school follows its hooked buddy back to the boat.
If your dad usually jigs deep over structure, then you'll probably want some fast sinking of fly line like a Teeny TS-450 or heavier.
This sounds really exciting-- please keep us posted and best of luck.