Trampoline Tightening on a Hobie 16
By David Hall 
If your lacings are rotten or worn anywhere, replace them. Some folks use bungee. I have before, but bungee lasts at most two seasons. If you lace it tight with good dacron or polyester line, it might last the life of the boat. NEVER use nylon or polypropolene (that floating ski rope stuff). Nylon will stretch to at least 10 times its original length within one season. Poly is just plain nasty and doesn't like to be bent around corners. I use fairly cheapo polyester rope from the hardware store. 50 feet is about $3.
To do this right, you'll need to take the boat off the trailer and put it on level concrete like in a garage. You need to align the hulls and you can't do that on a trailer.
I should mention that before you start to tighten your tramp, lubricate the side rails liberally with liquid dishwashing soap. Loosen the lacings completely and work the soap into the bolt rope until the tramp is loose in the rails. You might even pressure wash (garden hose with a nozzle is fine) along the rails to wash out anything that might have built a nest in there after you get the tramp loose. Then soap it again to make sure it's slippery. This is the only way to get the wrinkles out of the side and really get it all tight. When you're done, you should be tight everywhere including the area right behind the jib traveler track.
After you get that done, measure the cross diagonal lengths of the boat. Measure from port rudder pin to starboard bridle bolt and vice versa. The lengths should be within 1/8 inch. When you find the cross diagonal lengths are different by 3 inches, take your mainsheet and attach it to the the cross diagonal tramp pylons of the longest length. Sheet in until the cross diagonal length is exactly right, then tighten your lacings.
I have a really cool tool for tightening lacings. It slips over the line and you twist it to take out the loose line. Then there are two tapered belaying pins to poke into the holes where the line is tight behind the twister. You can get the tool from the Murray's catalog, but dang, you'd think it was made of gold$$. I guess supply and demand keeps the price up somehow. It REALLY works well, though.
Some folks have accomplished the same idea with a pair of pliers. Slip the open jaws over the rope and twist. Jam something into the grommet holes and that holds the rope tight until you go to the next lace. Tighten that one and move your tapered jam pin down one hole. Working very carefully, you should be able to tighten your tramp in 20 minutes the first time if you have the two tapered pins. This works so well you can lay on the tramp and lace up the center without having someone underneath. Without the pins folks resort to vice grips which skin your knuckles and cut the rope. When you're tight, the side rails should bend in about 1/4 to 1/2 inch in the middle. I've heard of someone breaking their rails with too much tension, but that could easily have been a hoax.
After you're tight and tied off, release your mainsheet and detach it from the pylons. You might hose your tramp to get the soap off it, too.
I have one line going all the way across the back each way and one line that goes aft and back in the middle. My boat is double grommetted up the center and across the back. I double lace to make an X pattern (XXXXXX) rather than a zig zag (/\/\/\/\/\/\). I've seen fancier laces with an X and an extra loop straight across (X|X|X|X|X|X), but can't get excited enough to change what I have. One reason to put more rope on is to make the holes smaller for anything to fall through the cracks.
David Hall
H-16, 80318, "Quick"
San Antonio, TX