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H18 Tramp = Tight Tight Tight - But WHY?
http://www.hobie.com/au/en/forums/viewtopic.php?f=13&t=11481		 Page 1 of 1
Author:  RobPatt [ Wed Dec 31, 2008 9:25 am ]
Post subject:  H18 Tramp = Tight Tight Tight - But WHY?
Hi,
The H18 tuning guide says make the tramp tight, tight, tight.

Why?

I understand the need for this on 14s and 16s since it directly influences overall boat stiffness via the pylons, etc... but on the H18 w/the crossbeams bolted into the hulls I don't understand how tightness affects stiffness or performance ?

Thanks!
Rob.
Author:  srm [ Wed Dec 31, 2008 11:31 am ]
Post subject: 
I'm sure others have their own opinions on this, but having a tight tramp on an 18 is probably 90% psychological. In any case, I always prefer to sail on a boat with a tight tramp. It's more comfortable (no sitting in a puddle) and from a racing stand point, even if it only makes the boat minutely stiffer, any advantage is worth taking.

sm
Author:  Tom Machette [ Wed Dec 31, 2008 12:00 pm ]
Post subject: 
Having a tight tramp on a Hobie 18 causes less independent twist between the two hulls. Unlike the 16 or 14 where if you tighten the tramp all you do is cause bend in the siderails, the 18 has the tramp attached directly to the hull and to the cross bars making a triangle to create stiffness. The tightness of the tramp will make the boat stronger by attaching the two hulls together over a 6 foot area, instead of just 8 bolts.
Author:  ncmbm [ Wed Dec 31, 2008 7:05 pm ]
Post subject: 
^^What he said^^
Author:  MUST5429 [ Thu Jan 01, 2009 8:42 am ]
Post subject: 
Tom explained it very well.

To expand a bit on his explanation, using a more technical term, a tight tramp provides "torsional rigidity"

In layman's terms, a tight tramp very effectively ties the hulls together and prevents them from independently "walking" thru the water.

If the hulls do not move together, in unison, as the boat goes up and over the waves, the energy of the wind is absorbed by the independent movement of the hulls, and the boat does not move as fast.

Always remember, there is nothing as good as a "Tight Tramp" :P :lol:

Stephen
Author:  MUST5429 [ Thu Jan 01, 2009 9:01 am ]
Post subject: 
Anticipating the next question, which logically would be what is the best way to get the most effectively tightened trampoline on the Hobie 18, here is the way I tighten mine.

If you don't have two people, there is a pretty cool tramp tightening tool in the Hobie Catalogue that uses a couple of "stoppers and a tool to twist the line tight.

Once the tramp is slid into all the tracks, The first thing I tighten is the tramp in the side tracks as much as possible.

Then lace up the center as tight as possible, this is easiest done with two people, from one side and someone on the other side with a pair of pliers to hold the line and keep it from slipping back as you move to the next grommet and pull again. Do your best not to lean on the tramp as you are doing this.

Now that the tramp was tightened in the side tracks, and is locked in place by the center being laced up tight, you can begin tightening up the lacing across the back using the same technique you used to tighten up the center.

This will result in a very rigid boat with hulls that move in unison in all but the most extreme conditions.

Stephen
Author:  kindofblue [ Thu Jan 01, 2009 6:04 pm ]
Post subject: 
Hi Stephen,
I'm curious as to why you tighten the center lacing first. I would think that you would want to tighten the fore and aft first to take all slack out of the fore and aft movement of the center lacing grommets, then tighten the center lacing. If you tighten the center lacing first though wouldn't that make it harder to reduce/eliminate the fore and aft movement of each tramp?

That said it's been 20 years since I've done this as we're just getting back into Hobies having bought an 86 18M a couple weeks ago.

MUST5429 wrote:
Anticipating the next question, which logically would be what is the best way to get the most effectively tightened trampoline on the Hobie 18, here is the way I tighten mine.

If you don't have two people, there is a pretty cool tramp tightening tool in the Hobie Catalogue that uses a couple of "stoppers and a tool to twist the line tight.

Once the tramp is slid into all the tracks, The first thing I tighten is the tramp in the side tracks as much as possible.

Then lace up the center as tight as possible, this is easiest done with two people, from one side and someone on the other side with a pair of pliers to hold the line and keep it from slipping back as you move to the next grommet and pull again. Do your best not to lean on the tramp as you are doing this.

Now that the tramp was tightened in the side tracks, and is locked in place by the center being laced up tight, you can begin tightening up the lacing across the back using the same technique you used to tighten up the center.

This will result in a very rigid boat with hulls that move in unison in all but the most extreme conditions.

Stephen
Author:  RobPatt [ Thu Jan 01, 2009 6:59 pm ]
Post subject:  Thanks for the replies.... I DO understand....
....having sailed many special olympics hobie 16s that flex like they're trying to sail in two different directions.... ( no ONLY due to loose tramps, however.. ) I get the torsional rigidity, no independent flex....

.... was just under the impression that w/the crossbeams bolted to the hulls this didn't matter too much.... obviously wrong, but that's cool ... that's what the community is all about.

On my H14T I get a racheting cargo strap and put it around both sidebars and get some prebend into them.... THEN tighten the tramp as much as humanly possible... THEN remove the cargo strap.... You can bounce a quarter off the tramp then, and that's without using bungee ropes, just regular tramp rope.

Cheers all, thanks much, HAPPY NEW YEAR.

HAPPY AND LOTS OF SAILING IN 2009!!
Author:  MUST5429 [ Thu Jan 01, 2009 9:39 pm ]
Post subject: 
kindofblue wrote:
Hi Stephen,
I'm curious as to why you tighten the center lacing first. I would think that you would want to tighten the fore and aft first to take all slack out of the fore and aft movement of the center lacing grommets, then tighten the center lacing. If you tighten the center lacing first though wouldn't that make it harder to reduce/eliminate the fore and aft movement of each tramp?


I've done it both ways, and logic dictates that the method you describe would work better. I used to do it that way all the time. That having been said, I seem to get a better result using the method I described. It could be a figment of my imagination, but it is what seems to work best for me.
Author:  kindofblue [ Fri Jan 02, 2009 8:00 am ]
Post subject:  data vs. speculation
MUST5429 wrote:
kindofblue wrote:
Hi Stephen,
I'm curious as to why you tighten the center lacing first. I would think that you would want to tighten the fore and aft first to take all slack out of the fore and aft movement of the center lacing grommets, then tighten the center lacing. If you tighten the center lacing first though wouldn't that make it harder to reduce/eliminate the fore and aft movement of each tramp?


I've done it both ways, and logic dictates that the method you describe would work better. I used to do it that way all the time. That having been said, I seem to get a better result using the method I described. It could be a figment of my imagination, but it is what seems to work best for me.


Thanks for the reply and the proof is in the pudding. Clinical researchers have a saying "In God we trust. Everyone else has gotta show their data." And data, even single case data, trumps rationalization or speculation every time. :D
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