The transitional hydrofoil surfboard of 1997

During 1997 we decided to try and make a paddle in hydrofoil surfboard. At the time we were living without electricity or telephone, and had no idea that Laird Hamilton was also working on hydrofoil surfboards.We used two straight wings at least ten inches across and three inches deep fore and aft. One wing was back on the main fin, one was on a smaller fin ( really just a foiled supporting strut ) 25 % forward, so on a ten footer approximately 2'6" forward. The front foil is approximately 2 inches from the bottom of the board, the rear foil is in line with the front one at a lower angle of lift which puts it about 4 inches up off the bottom depending on the rocker.Foils were mounted on upright 'spitfire' fins, fins and foils were marine ply sheathed in kevlar/epoxy and graphite coated, foiled and sanded to perfection.Lift wise the front wing is set up parallel to the bottom and the rear one is at a slight angle of lift ( it works out at about 4 degrees or so).The key to the whole deal is not to try and lift the entire board way out of the water. Without foot straps it is impossible to control a board which is raised completely out of the water because without the surfboard buoyancy acting to bring the surfboard back to an even keel, or leverage from strapped in feet the board will just fall over.With straps the feet can be used to lift the rail up, without straps it's impossible as feet can only apply downwards pressure. Because the axis of rotation of the board is down below the bottom, any rail to rail heeling soon places the centre of gravity way over to one side of the axis of rotation. . .. this means that downwards pressure on the upwards rail becomes ineffective. Straps are needed in this kind of situation. . . or buoyancy from the rail.So, by keeping the foils close to the bottom and keeping the lift angle very low we allow the foils to do most of the lifting work while keeping the hull just touching the water lightly. The effect is remarkable as the board still behaves like a surfboard but is using mostly foil based lift. By lifting the nose the board will lift above the surface, but only slightly so that the rails will still make contact during turns. It feels amazing and is brilliant for riding unbroken swells and the sort of lines that the tow in keel boards like. .. . . . there's a definite reduction in drag and the same smoothness and foil based feeling that fully airborne boards have, it's like a magic carpet without any noise from chop or spray making, and yet the board looks like a normal board surfing, almost !As far as paddling goes it's not noticeably different because the foils aren't struggling to lift the board up thus causing high drag. Most foil based boards have lots of lift angle dialled in so they have a lot of drag followed by a sudden transition to 'foiling' when the hull breaks free. What we did is to keep the lift angle pretty much the same as the bottom of the board, that way the lift of board and foil is combined, and at low speeds the foils are still well behaved. . .. . . there's a long smooth transition to 'foiling' and no drag 'bump' to overcome.The only drawback is that it isn't spectacular to the observer. . . less spray, less wake and no remarkable hoisting of the board way above the water. It's all in the feeling.Also, riding in the pocket in steep waves is difficult or impossible due to the high centre of gravity.We had a ot of fun with it, unfortunately we have no pictures as we had no camera at all at the time . . . spare money was all going on board building materials. What I did was make a set of drawings, unfortunately in my enthusiasm I sent the originals to surfer magazine so have no copies. I can reproduce them if anyone is interested.The only way a fully airborne paddle in board could be done IMO would be to put the feet in straps on takeoffBy the way I say 'we did it' regarding paddle in hydrofoil boards because the board was able to produce all the required lift to support board and rider at times . . . a kind of 'transitional foiling hull' .We just found one of the original pictures:.