If you needed a "new" tow vehicle, what could you cobble together from the junkyard? Could you piece together a street legal toy hauler that would get 30 mpg at 70 mph? Any chance it would have a/c?

take an old beater pickup (the small one - like the old Nissan B2000 or Ford Ranger), yank off the truck bed, and mount racks for whatever you need to haul (or a drive on/off platform). You could even add AC.

Probably cobble it all together for less than $1500 USD if you can find a decent motor.

Hmm- IMO only way to get that kind of mileage and be able to tow is a diesel- ideally turbo diesel-
SO- options- get an old UPS/Fedex diesel truck- ditch current body/shell and add something more aerodynamic (or just "chop" it!!). Ideally the vehicle will be aerodynamic and essentially break the wind for your cat- also get a "narrow" cat- Taipan, Wave, "A" cat- a lightweight trailer with tall, narrow tires, mount the mast horizontally with mast stands made from old mast sections (at least up where they catch any wind- or slit some old mast sections and mount over what you have). Ensure you have a good highway rearend (ie tall gear ratio) and a manual transmission. Have a small passenger compartment (2 people) with added insulation in roof/floor/doors and use a small AC compressor.
Another option is an old Ford diesel Ranger pickup, Isuzu diesel or VW diesel pickup or old diesel Jetta wagon-

Kirt

Does anyone have any experience with the old Jetta diesel?

It seems to me the drag from the boat is a lot. Anyone ever try an aerodynamic covering?

Take the tramp off, remove everything off the mast with the exception of the diamond wires and you reduce the windage a good amount.
Keep your vehicle in tip top shape, ie good pressure in the tires, clean air intake filter, change the oil every 3K miles and keep your cooling system in check as well. Everynow and then clean the fuel system and all of a sudden your MPG will go up.

Try it, it works wonders.

I have seen some "A" cat "trailers" that actually fully encase the boat and they are angled in the front to reduce windage- You can also mount your mast on top of the vehicle with the front of the mast forward to reduce windage from the mast supports on the trailer and keep the mast low. Most aerodynamic rig I ever had was my old 18sq trailer- boat "knocked down" between races so hulls were put upside down on top of narrow, low storage box with bottom flush with trailer frame and filling the space (to keep drag low under trailer) and mast held parallel fairly low over vehicle- all of the boat/trailer except the mast (and mast supports were round tubing) were in the "slipstream" of my truck so little additional aerodynamic drag between my truck w/ cap on the back.
Another "advantage" of supporting your boat on the trailer by the beams is you can eliminate the trailer crossarms/rollers/cradles which typically are NOT in the vehicles slipstream so offer a lot of drag. Our hulls are pretty aerodynamic (although there is a large difference between the aerodynamics of an "A" hull vs a H16 for instance).

Kirt

I just towed an A cat from WA to MN behind my Honda del Sol Si, with the tramp on, mast clean and lowered to just clear the roof, trailer modified to keep the hulls parallel to the road. The car normally gets 35 mpg @ 75 to 80, which dropped to around 20 to 25 mpg with the boat at similar speeds.

Dave

Dave-
Glad to know I could tow my Flyer with my del Sol Si if I needed to! I normally use a 2003 Dodge 3500 diesel auto, which gets ~20mpg at 70 empty which drops to ~17-18mpg w/ Flyer behind at 70, of course when diesel was ~$5/gal. I towed at 60-65 which got me ~19. At regattas I sleep in the back of the truck so save myself room charges and hassle of a tent, figure that makes up for a little more fuel cost (and I can bring the kitchen sink if I want to!!) Hadn't thought of putting a hitch on the del Sol- I wish Honda would make them again, I'm about to roll over 100K on mine and would buy a new one if they made them!
IMO the "A" cats are about the ideal cat to tow due to their light weight, "slippery" hulls, and narrow beam which allow a trailer with no crossarms and light weight (ala the Trailex I have). I would love a 2 piece mast ala the old BIM "A" cats cause you could then put the 2 mast pieces down either under the tramp or just above and cut that air resistance as well!

Kirt