I am building a slide in kayak rack for a utility trailer (converted boat trailer). Trailer bed is 48" x 84" with 15" tall side rail (still has the long tongue). My thoughts are a 'A' frame that I can put my yak in the lower middle, one on each side and then add a second layer for 2 yaks and a box for paddles. I think I will have room for a 15"x36"x72" storage box on the bottom. Thinking that I would set the storage box up with the door on the end with a pull out drawer for gear. Any thought or suggestions on any of this ?

Rack would be built out of top rail for chain link fence (1" steel tubing) and would be welded. What is a good safe length for the outside supports 28" 32" 36" ?? (connect the dots for rough diagram)
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This might answer your questions http://www.texaskayakfisherman.com/forum/viewtopic.php?f=53&t=121567

I rigged up a great kayak setup for my 5 x 8 utility trailer. Thule makes a product called Top Tracks. The tracks are 5' rails that are actually designed to mount onto a camper shell roof. They happened to fit perfectly on the side rails of my trailer. Now I can haul anything I want in the trailer or can snap on my Tule crossbars & Thule 460 foot packs and have a kayak hauler. It's the best of both worlds.

Mariner Sails has the Top Tracks, 460 Feet, and crossbars of various sizes in stock for your inspection. There is also another version of Top Tracks that are made to mount on bare roofs via small shallow Moly bolt type fittings that go inside your headliner.

Thanks for the response and especially the pictures. Gives me some very good ideas on how to set up the trailer.

CAUTION: zinc fumes are poisonous. do not breath the fumes while welding galvanized.
maybe christian will chime in on what he does.

might check these out in the mean time...

Hauling Kayaks - Trailers ... Plus link to over 20 pages of yak trailers

better to go longer than shorter IMO. you can always cut off if too long later