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Old 25th November 2006, 04:50 PM   #1
pretentious_indifference
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Default narrow boom?

Hello all,

I have a couple of quick questions regarding rigging. I am considering buying a new 2005 HPL (150-210cm) carbon boom which I tried and it seems pretty nice. However, there is a peculiar problem with it I did not experience before. Its arch is unusually narrow with the widest point of only 18'(46cm) and the mid point is 14'(36cm). So I tried it today and apparently when I sailed the sail kept touching the leeward side of the boom.

I did not want to apply any extra outhaul (to already at that point reasonably well outhaulled sail) since I was quite underpowered. So I had to release the downhaul to the point of having like 4-5 cm below the manufacturer recommended lenght (5.9 RAF Neil Pryde). As at the same time I left the outhaul fixed it a little bit stretched the sail vertically. But even after that when I came back on the water I could see the boom beeing touched by monofilm. I know that my rigging was wrong but it was the only idea that came to my mind about how to fix the touching problem.

I have never had this experience before as I owned a number of freeride boom which were pretty wide. Now my question: should I discard the boom or may be I am doing something wrong? Is it a compatibility issue of boom vs. sail? Does touching actually influence the dynamic of the sail with any adverse effect? And if does with how much touching can you get away?

I included the link to a picture with the boom. The read lines are where the sail touches the boom, the green outline is the profile of a regular freeride boom.




Your help will be greatly appreciated,
Thanks a lot,
Al
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Old 25th November 2006, 11:28 PM   #2
steveC
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Default RE: narrow boom?

Hi Al,

I was wondering about your outhaul length for the 5.9 sail. Were you achieving the specification requirements of the sail, or is it your preference for some negative influence? Also, are you on the large or heavy side, as your harness line position tends to suggest you might be?

From the photo, it appears that you have a wave boom where the curve of the arms is reduced to permit the sailor to get closer to the rig to enhance maneuverability. Personally, I've never had an issue where the sail comes into contact with the boom, but I tend to rig my sail on the flatter side. If I'm correct in assuming that you prefer negative outhaul tension, you probably have two choices. Given the fact that most booms in the size range you're considering here will tend to be narrower than a somewhat larger slalom boom, the easiest solution would be to rig a larger sail to ensure that you have adequate power and enough positive outhaul to avoid contact with the boom. The other choice would be to purchase a wider slalom or freeride style boom instead.

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Old 25th November 2006, 11:28 PM   #3
steveC
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Default RE: narrow boom?

Hi Al,

I was wondering about your outhaul length for the 5.9 sail. Were you achieving the specification requirements of the sail, or is it your preference for some negative influence? Also, are you on the large or heavy side, as your harness line position tends to suggest you might be?

From the photo, it appears that you have a wave boom where the curve of the arms is reduced to permit the sailor to get closer to the rig to enhance maneuverability. Personally, I've never had an issue where the sail comes into contact with the boom, but I tend to rig my sail on the flatter side. If I'm correct in assuming that you prefer negative outhaul tension, you probably have two choices. Given the fact that most booms in the size range you're considering here will tend to be narrower than a somewhat larger slalom boom, the easiest solution would be to rig a larger sail to ensure that you have adequate power and enough positive outhaul to avoid contact with the boom. The other choice would be to purchase a wider slalom or freeride style boom instead.

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Old 26th November 2006, 04:42 AM   #4
Ola_H
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Default RE: narrow boom?

The short HPL carbon booms are among the narrowest around. That said, if you don't use a particularly deep drafted sail, you should not run into problems with the sail touching the boom. Ive run lost of different wve and freestyle sails from 3.5 to 6.3 on my HPL without the sail toucing the boom, but my 6.6 speed sail (which like s a fair bit of neg outhaul) and my 7.0 freerider/wave sailo doers touch the boom.

As SteveC says, the reason for the narrow width is better handling in manouvers. If you're more into freeride and straighl line blasting, a slightly wider boom might work better, but even so, I'm also surprised a sail as small as 5.9 will touch the boom. It makes me suspect the sail is either under outhauled or that the boom is longer than neccesary for the actual outhaul applied.
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