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Old 8th June 2010, 12:21 AM   #1
mikecole
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Default Cavatation issues with quad 81

I have a quad 81 that I use in light air with a 5.8m or 5.3m sail. I am 70kg, this board has replaced an Evo 83. I am having issues with fin cavatation during jibes. I find its happening quite often so I need to solve it. In a normal jibe the board can carry a lot of speed. When one of the fins cavatates it feels like the board has collected a clump of seaweed on the fins. Curiously, I find this happening occasionally in a bottom turn as well but not as often. I suspect smaller fins may solve the problem but I thought I should ask other sailors about this issue before I attempt to solve it. Any ideas???

Mike
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Old 8th June 2010, 06:10 PM   #2
Ola_H
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Fins might make a difference, and I would if so try the 15cm Drake Quad fins in front as they are quite a lot softer and hence more forgiving than the 16cms on the Q81.

BUT, first you would encourage you to try a small technique tip: I would guess that if you pay just a tiny bit of extra attention at putting some mast foot/front rail pressure on the board just when you initiate the jibe (or bottom turn), then this will not happen very often. Essentially, just keep your elbows down and pull a bit downwards on the boom in the early part of the turn.

Tell me how it works out.
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Old 9th June 2010, 02:34 PM   #3
PG
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Doesn't this sound awfully similar to the Boardseeker experience with the Quad 76? Thwey had problems with unpredictable bottom turns. Then Starboard replied with

"Looking at the Starboard Quad's test results in other magazines, the Boardseeker test goes against the grain. We also know that the Boardseeker test team is very thorough, with excellent in-depth test reviews. As there have been some known issues with finbox misalignments and tail rocker problems, there is a high chance that the board in this test is defective"

Maybe you just have a lemon? It is much easier to screw up in production with 4 fins than with one (that easily enough can be seen if it is straight or not).
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Old 10th June 2010, 03:09 AM   #4
Ola_H
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Let's just say that I think that it the testers would have followed the advice I give above and had given it some time, I think the results would have been different. I know they have really good test sailors, but even so some light adaption of style is needed sometimes.
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Old 10th June 2010, 12:59 PM   #5
mikecole
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Thank you Ola. For sure I'll try and apply the advice you've provided. I am however left wondering why I would need to be so careful about a simple jibe when this is not the case with my high wind board (SOS RF68) nor was this the case with my previous Evo 83. I should also mention that I sailed the Q76 on maui in April for a day and never experienced this odd cavitation issue on a jibe.

Thanks and I'll report back as soon as I get a chance to get out sailing.

Mike
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Old 11th June 2010, 04:34 AM   #6
Ola_H
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If it works out like I hope, then after a short will it will not feel like being careful, more like a natural way to use the rail of the board. Of course, you could theoretically also have a faulty board or something, but lets hope not. I'm not 100% sure this trick will work since I personally think the Quads react very naturally to turning. But I spent some effort really trying to consciously provoke them, and my conclusion is that there is a certain type of back footed turn that can throw the board off its tracks if you push it hard enough. At least for me, with just a tad of more upright/front stance at the turn entry, I have not been able to provoke this even when I push it as hard as I can.

Let me know if it helps.
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Old 11th June 2010, 10:10 AM   #7
aa25
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After few sessions of struggling a bit with turns on the quad 71, I found had to adjust technique a little to get in the groove. Mainly relates to initiating bottom turn. Used to find if charge straight from planing flat onto rail too quickly, felt like fins not fully engaged and turn could go haywire, perhaps from air caught around fins. Slight adjustment I've found is using feet a bit more; I like to roll the foot a bit and push the toes right at the start of the turn just to feel the fins and rail engage. Then get this nice feeling of supergrip and can charge into bottom turn really hard. It's a tiny adjustment (little press of toeside rail) which happens in an instant at start of turn but provides confidence in rail gripping.
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Old 12th June 2010, 02:56 AM   #8
mikecole
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Thanks aa25 for your advice. I am feeling the same thing, like when you push air down onto the fin because you bounce in a turn... except I get this feeling on my Q81 without the bounce. I also get it more on a jibe than a bottom turn so perhaps my jibes are too much from the back foot as Ola points out whereas I am trying to drive the bottom turns from the front foot for sure. Problem is, where I sal trying to draw a jibe out is not easy due to the water state... We'll see and I will report back.

Mike
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Old 25th June 2010, 01:39 PM   #9
mikecole
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Finally a day to go sailing! We had only tiny little waves so I dedicated the day to trying different jibe techniques to see if I could solve the odd cavitation issues I'm having with my Q81. My findings are that the Q81 likes forward rail pressure as Ola pointed out. This is consistent with the lack of cavitation I find while bottom turning. I tried putting my back foot way forward for jibes (on the front pad) and this seemed to be an easy way to solve the problem. I'm still left wondering however why I can't snap that board around like I could with the Evo 83? I'm also left wondering if the smaller fins might be more to my taste. Has enyone tried the 13cm fronts in the 81?

Thanks! Mike
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Old 2nd July 2010, 05:13 PM   #10
Ola_H
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I tried them on the 76 the other day and it works great. I'm not sure it will help with the jibing issue though, but it's a nice way to soften up the ride a bit and at least for me upwind and planing is not affected much, at least not with sails around 5.0 and smaller.

But for the jibing: if you're committed you should be able to push the board hard with the back foot too. The problem area is then the entry is a bit "undecided". Then , if the board wobbles a bit it seems flow around the fins will get disturbed or something which will sometimes give a insecure feeling.

So for starters, either enter the turn with forward pressure like described before. You it is better to do this by rig downward pressure then by moving the front foot forward since with the rear foot still further back, you can shorten up the turn and finish it tighter if you like. Once the board is settled in the carve with the front pressure, it will not get upset if you finish the turn more back footed.

But you can also make a turn where you from the start push the board really hard with the back foot, almost whipping it around on the tail.

Once you're comfortable with both these turns on the board, I think you will notice that you can now suddenly turn it any way you like. Basically, any time you enter the turn hard and with confidence, the board will respond. It really likes to be pushed.

Please report back how things proceed.
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