Can anyone tell me if it is normal/OK to see curvature on the sidebars of a H16 with the trampoline tightened up ?
How much would be acceptable ?

I would say as much as posible.

When I tightend the tramp on my H16, I would rig the mainsheet around the sidebars, pull it tight, the curve would bend inwards anywhere from two to three inches. I would lace the line as tight as posible, then release the mainsheet. Boy that tramp was TIGHT!!! I wouldnt even call it a tramp, more like the floor It was pretty tight. So if you see a nice curve you are fine!

The visuals to Robi's post -

Rigging the mainsheet:


Pre-Tension:


Post-Tension:

Don't go too crazy with the tension, I've heard of trampolines splitting if too much tension is placed on the laces, even new ones. For me, 1-2 inches on each side bar is OK and gives a tight enough tramp and frame.

My GOSH that thing looks bent!

If it works, I won't critisize sucess, BUT that looks like asking for trouble!

I only hand tighten. I retighten after a few sails, as the lacing rope seems to stretch over time. Even with hand tightening, my brass grommets have cracked over the years.

...Matt Miller: Is there an OFFICIAL Hobe opinion?

Matt Miller was the one who turned me on to this technique. It's how they put together 65 boats at the worlds without shredding their hands.

Note that 1) My trampoline is relatively new ('98). It's also heat welded mesh (no stiching to tear out) and 2) the second picture was taken before the tramp was tightened and the mainsheet released. The sidebars do spring back some. They're not as bent as you might think - the perspective of the photo exaggerates the bend.

I would like to see a picture after release of the mainsheet.
Even 1 inch seems a lot to me.

The tension technique shown is much better than just yanking on the line each grommet, one-at-a-time. That causes each grommet to get strained well over what is needed. When you ease off the mainsheet, the grommets will get fairly equal loads. We used to use vise grips and pull as hard as physically possible on each one!

I think the bow in the side bar shown is not nearly excessive. There is no "Official" Hobie tension, but I prefer a TIGHT tramp that will also reduce the overall wear on the boat by keeping the frame tight and square.

So here's a question...Do you need to square up the hulls every time you tighten the tramp? I am putting on a new mesh tramp on my 84 redline. The boat was supposedly squared when it was epoxied for stiffness (I helped on the project), but I am not sure what will happen when I take the old tramp off. I like this technique, I guess I could always rig a second set of blocks. One to ensure the hulls stay square, the other to pre-tension the side bars.

Thoughts?

I would measure each time you re-tension the trampoline. Even with the corners epoxied, I would bet that an improperly tensioned tramp could pull it out of alignment.

The measurements are port bow to starboard rudder pin and opposite. Compare then pull the longer measurement closer with a line setup. Then tension the tramp with the line setup in place. Sometimes you will see a "spring back" effect and you will have to over tension the line setup, tension the tramp then release the line and as the frame settles in, it will end up more square.

Thanks, Matt.

One quick question



Which setup were you suggesting might have to be overtensioned? The blocks squaring the hulls or the rig on the sidebars? I am guessing you meant the hulls, just allowing for some drift in them after you release the blocks.

Andrej

...and of course, this winter I had finally bought a tramp tensioner

Over-tension the line system used to square the boat frame (bow to opposite stern)... past square, then tension the tramp lacings. When you release the bow to stern line you will likely see the boat settle closer to square.