does it have to? I want to sail in a huge tidal bay with sandbars. 2 hours on either side of the high tide would be sailable easily but stretching past that point would be a risk IMO. Is it possible with a Nacra to sail without the boards all the way down (or even without them all together a la a hobie cat)? Just curious.
You don't have to use the boards at all, they are only helpful in stopping leeway, lifting a hull, and pointing higher when going to windward. With the boards up, or left out, the nacra should only draw a couple of inches. Sailing in shallow water can be a blast, but if your rudders kick up completely you can lose control and wipe out. hitting bottom or obstructions at speed if you misjudge depth on sandbars can be both painful & expensive structurally. Being tossed off at speed in shallow water can also hurt. There's nothing like gravel rash to bring the point home. Having rudders partially or fully in the water at all times helps ensure you remain in control. I sailed at speed in a foot of water with the rudders only just under the surface, but it was tiring because of the huge effort needed to steer.
grinding away your rudders on the bottom is a no-no unless you are into rebuilding gelcoat and glass layers.
Enjoy!
Thanks! I was beginning to think it was too stupid a question for anyone to answer!!!
Where in Queensland are you? My mother was born and raised in Toowong just outside Brisbane and my cousins still live all around there. Jindalee, Mt. Ommaney and Forest Lake.
We spent quite alot of time down the Gold Coast and Surfers Paradise a while back (Gosh, it was 1984 now that I think of it.). Went throught the Glass House Mountains and over to Red Bank. It's a bonza place! No worries.
Greg
Greg,
Completely raising your boards will make tacking very difficult.
The standard Nacra rudder system allows you to set them at a shallow draft but, as Qb2 said, it puts a lot of stress on the hardware and the skipper.
You could break a casting $$$$
The previous owner of one of my old boats, a Nacra 5.2, had made a set of shoal draft rudders.
They drew 10"-12", were very wide and had alot of undercut.
He made them out of plywood with an epoxy coating.
I never used them so I don't know how well they worked.
When you say, "a la Hobie Cat", I assume you are refering to he 14 & 16 because the Hobie 17, 18, 20, 21, Fx/one, Tiger and Fox all have boards.
The 14 and 16 have asynetrical hulls with alot of rocker(banana boat).
The flat side of the hull gives the leeway and the rocker helps in tacking.
FYI I just had to buy a Nacra 6.0 casting... $200 US. They aint cheap.
Both of the prior posts are correct.
I would add that if you are sailing in an area with a big tidal range and a lot of sandbars, you have to do the same thing all the boats in that area do, both powerboats and sailboats:
Coordinate your boating activities with the tides.
Have charts and local knowledge to tell you where the sandbars are (because they move).
Learn to "read" the water so you know when you are coming up on a shallow area and can either change course or pull up your boards and rudders before you get there (so you don't break anything).
Plan your sailing for the day so you won't have to be sailing upwind back to your home destination if it is going to be across very shallow water, because, as Sam said, it is very hard to tack with your boards and rudders up.
Rick and I once sailed our Hobie 18 for 40 miles across the backcountry of Florida Bay from Key Largo to Flamingo. A lot of the way we had to sail around or across mud flats and a lot of the way we were in mere inches of water, with our boards pulled all the way up and our rudders floating out behind.
Luckily, it was a reach for us in both directions. If it had been upwind either way, we would have been in trouble --even if we had had a Hobie 16 -- because the water was so shallow.
My advice is to take water and a picnic lunch in case you get stranded on a sand bar and have to wait for high tide.
You will get familiar with the area real quick, so I don't think it will be a problem. On any kind of beach cat, boards or no, you will be able to go across water depth measured in inches rather than feet.
And if you are in shallow water and still floating and can't tack, heck, you can just get out of the boat and turn it manually to the new direction. 
Bullswan I live at Yandina, on the Sunshine Coast. The whole of SE Queensland has changed dramatically since you were here, Its millionaires row for anyone with a house on the beach, the population is tipped to double to about 4m by 2015. The Gold Coast is wall to wall high rise, tourists and traffic. Brisbane is gridlocked and we are not far behind but resisting like mad. There is still plenty of exotic scenery here, pineapples, sugarcane, strawberry farms, rainforest and laid back living, but suburbia is slowly enroaching. Nambour where I work went from 4 sets of traffic lights to 9.
I know the cost of sailing in shallow water. One of the last times I sailed my QB2, before it got a terminal case of rot, I landed nose first on the bow when we hit a concrete block with a centreboard sailing under the Maroochy River bridge. I was more intent on making it under the highest part of the span and didn't keep an eye on water depth. Tore a chuck out of the board and I got off with a bloody nose. On one other occasion a mate and I were sailing my maricat off Townsville in 30plus knots and were hurtling back downwind towards the beach in 4 foot waves. I scoured half an inch off both rudders tying them down to hold them in the water and we hit bottom just before i was going to turn into the wind. There was an almighty thump and we got tossed off and landed in a heap. My local fibreglasser said I had completely smashed a 3 foot square section of hull and left it like tissue paper. Luckily he was teaching students and needed boats to work on so I paid only the cost of materials. The blow to my ego was sitting on the beach for the next two weeks of glorious weather watching everyone else out sailing.