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Old 28th April 2010, 05:08 PM   #11
agrelon
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Originally Posted by Farlo View Post
Excellent... but check your mast compatibility anyway. RDM have different bend curves than SDM, much more in the bottom I think. You will keep your sail longer, and get more from it, with the proper mast (not necessarily a North). Your loft should be able to advise you.

Feeling sluggish and slow to plane is not uncommon in strong winds. Sometimes you can hardly sheet in and your board seems stuck upwind. Additionally, low speed suggests that your sail was maybe too flat (too much outhaul). I don't think it has anything to do with your boom. Raising it may help in moderate wind but many sailors would lower it in high wind anyway.
You mentioned not being able to sheet in when sailing overpowered. I use to get that a lot on raf sails but with the blocked profile of a cambered sail this isn't a problem at all.

I have a theory also that lowering the boom helps in overpowered conditions not just because of a lower body position and easier mast foot pressure, but also because with a lower boom there is more of the mast above the boom clamp (which is a pivot point) and therefore the mast can more easily bend off and exhaust gusts as the sail creates greater leverage over the pivot point.

I got a couple of photos of my overpowered session and my mast is definitely bending nicely.

http://www.seabreeze.com.au/Media/Vi...?m=3&p=agrelon
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Old 28th April 2010, 07:28 PM   #12
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Well, your boom is rather low in the window but this is frequent with North Sails, made for big guys. I have a pretty similar position whatever the wind speed. It's difficult to see from a few pictures whether the mast bends properly of not (the last one looks strange actually). Anyway small differences in bend curves may hardly be noticeable but translate in significant overstress. If you want to keep your RAM F8, my advice would be to get the closest compatible mast you can find. 60 to 75% carbon should be OK in this size.
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Old 28th April 2010, 07:49 PM   #13
agrelon
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Originally Posted by Farlo View Post
Well, your boom is rather low in the window but this is frequent with North Sails, made for big guys. I have a pretty similar position whatever the wind speed. It's difficult to see from a few pictures whether the mast bends properly of not (the last one looks strange actually). Anyway small differences in bend curves may hardly be noticeable but translate in significant overstress. If you want to keep your RAM F8, my advice would be to get the closest compatible mast you can find. 60 to 75% carbon should be OK in this size.
I think that last picture is taken as the mast is bouncing back, as the leech is floppy. Either way, for the moment I'm going to be using a 5.6m HSM Psyclone (5 batten super light freestyle sail) which is about 2-3kgs lighter than my RAM. I think it should work better with my fin, which felt small for my more powerful, and bigger, RAM. If I can clock good speeds on the GPS and my all round sailing improves (easier waterstarts, less tiring, easier jibes, easier jumps) a lot due to the lighter weight of the sail I might consider changing back to RAF sails... We'll see what happens.
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Old 28th April 2010, 11:17 PM   #14
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IMHO you can't really compare a race machine like the RAM and a freestyle sail, however good it is. This been said, the advantages of cams in such small sizes may be marginal, although competitors will always prefer the fastest sail. Also I presume that you can use smaller fins with cam sails. Would anybody confirm?
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Old 28th April 2010, 11:40 PM   #15
agrelon
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Originally Posted by Farlo View Post
IMHO you can't really compare a race machine like the RAM and a freestyle sail, however good it is. This been said, the advantages of cams in such small sizes may be marginal, although competitors will always prefer the fastest sail. Also I presume that you can use smaller fins with cam sails. Would anybody confirm?
I'm thinking they might need bigger fins as they are more powerful and heavier and therefore need more lift and lateral resistance. At least that's the feeling I'm getting with a smaller than recommended 30cm fin...
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Old 29th April 2010, 03:43 PM   #16
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Well I think that a cam sail has much less drag, possibly also less lift but better lift/drag ratio, than the equivalent no-cam. Although more powerful, it generates less sideways force. Of course it's difficult to prove because cam and no-cam sails often come in different designs. However there are a few exceptions and I wonder if a mag ever did this kind of test. But it has nothing to do with NS warranty anymore. Let's open another thread if you're interested.
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Old 19th May 2010, 12:57 AM   #17
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I like the feel of a boom set somewhere between the shoulders and chin.

I've had old school guys claim that forehead height was once the rule of thumb.

Any discipline that's concerned with power, formula, freestyle, slalom, goes with a high boom.

Maximum height should give the best power transfer, as it's closer to the sail's center of effort. Less power is wasted in the form of mast flexing. When your sail is on the max downhaul settings, and the COE is low and backhanded, a raised boom can enhance your leverage over the sail.

I disagree with the opinion that most speed sailors set their boom low. Looking at a few videos the boom is typically shoulder height and above. On a narrow speed board, that would seem higher than normal.

If your boom is slipping from chop bounces, you might want to spend some extra time making sure the clamp is set well.
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Old 24th May 2010, 10:54 PM   #18
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BD uses a low boom and he's done O.K. Photos of people sailing are deceptive as far as boom height is concerned, since their body position may make the boom appear higher than it actually is. If you're comfortable, whatever the boom height (within reason), then you're probably faster.
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