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| H18 Tuning Questions long..sorry http://www.hobie.com/au/en/forums/viewtopic.php?f=13&t=5835 |
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| Author: | cjacosta [ Fri Jan 12, 2007 9:42 pm ] |
| Post subject: | H18 Tuning Questions long..sorry |
I'm sure this is the first time this has come up, but I have some tuning questions. I am interested in setting up my 1987 H18 with comptip in the ballpark. I've read everything except the H18 Performance Manual because I can't find it and I am thoroughly confused. I know there are a lot of different answers for crew weight chop, wind speed, etc. But I need some help. Lets say crew weight of 400 pounds and windspeed of 10 knots, no chop. Also, right now, I am not interested in putting prebend in the mast with the diamond wires. Lastly, I know my skill will hinder me much more than my rig tension, this season, but not for long:) Here is some source of my confusion Hobie Alter says he runs his rig loose and doesn't rake back as far as most. What exactly does that translate to in terms of which holes on the forestay and shrouds? He runs loose diamond wires. Bob Mimlitch says he doesn't rake his mast back in Hobie U, he says start at the 3rd hole from the bottom on the shrouds and tightens the forestay. If I'm on the 3rd hole from the bottom on the shrouds, I'm at max rake, a couple of inches between the blocks on the main sheet. He also runs loose diamond wires. What is a good starting point for mast rake in terms of holes on the shrouds and forestay, or even inches from main halyard to rudder tips? Diamond wires, mine are floppy and I'm pretty sure they should have some tension. I can press one side to the mast at about 36" above the rotation arm (I haven't measured), and if I pull down on the diamond wire, I can make the barrell on the bottom sag in its holder. I've seen one recent post that says 400 pounds. I assume that is adding prebend. I have a Loos guage. |
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| Author: | MBounds [ Sat Jan 13, 2007 6:30 am ] |
| Post subject: | |
Disclaimer: I haven't raced an 18 for years, so some of this might not be correct - any 18 experts out there, please correct me if I'm wrong. Diamond Tension - the 18 mast/sail combination is not set up for pre-bend. From my fuzzy recollection, the diamonds should be loose enough to touch the mast 18" above the lower connection point. Matt Miller knows the right setting. I looked at photos from the 18 North Americans in 2006 and 2005 and I could not see any visible "looseness" in the weather diamond wire. Mast Rake - beacause of the variation in wire length, anything telling you what hole to put your shrouds in is going to be inaccurate. You have to measure your mast rake. On boats with internal halyards (like the 18 ), you use the trapeze wire - lead it forward to the bridle tang, mark it with your thumb, then take it back to the transom and see what it lines up with. (I don't know what the setting is on the 18; on the Tiger, it's the lower gudgeon; on the 16, you use the halyard and it's 10-16 inches below the transom edge.) In any event, if you've got any space between the blocks, you're not at max rake. Again, looking at photos from the North Americans, it sounds like you're in the ballpark. Most everybody has just a few inches left in their mainsheet system. In summary, it sounds like you need to tighten up your diamonds a bit and that you're in the ballpark with your mast rake. |
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| Author: | DougHobie17 [ Sat Jan 13, 2007 3:29 pm ] |
| Post subject: | |
There is a whole chapter in the Hobie 18 in "Catamran Racing for the 90's" . Think it is by one of the Hobie's, so it should be right on. Doug |
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| Author: | ncmbm [ Mon Jan 15, 2007 1:38 pm ] |
| Post subject: | |
Doug, he is quoting from Hobie Jrs writing. The 18 likes the mast pretty straight up for best downwind performance. Your diamonds are way loose. Phil Berman says put marks at 12", 18" and 24" from lower diamond bolt. I believe 18" is best for most conditions and crew weight. So you should just be able to touch the wire to the mast at 18" from the rotator. Mast rake will take some experimenting. Your helm will change as you move the rake so be aware of this. I run mine back and always have, it points better but moves slower downwind. I now run a Tiger main, jib and spin so I'm slowly forgetting how the original 18 should be set-up. The 18 performance guide gives a tremendous amount of info on sail shape etc, get one if you can find it. Later |
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| Author: | John Eaton [ Mon Jan 15, 2007 2:15 pm ] |
| Post subject: | |
Ditto on finding Phil Bermans book. We raced with the mast as straight up as possible or no rake(jam the forestay as deep in the furler as possible). We follow the general consensus that the 18 needs all the help it can get downwind. At your weight this should be especially true. Shroud tension is more of a function of rig tension. Hang on a trap wire (on the beach) to tighten up side stays as the wind increases. Windy/tight, light/loose. Suggest checking diamond tension (after all above settings are done) by sailing up wind and have crew check tension on the leeward diamond wire. You want to tighten both evenly until this leeward wire just becomes snug. 18" is probably ball park close, but check it on the water and then fine tune. |
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