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Fin Size?
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bmergen



Joined: 13 Jun 2000
Posts: 16

PostPosted: Wed Jul 19, 2000 8:00 am    Post subject: Fin Size? Reply with quote

How do I tell if my fin is to large for the sail I am using? What does it feel like? Im new to the sport, still getting comfortable with hooking in and being in the straps. Any advice is appreciated.

Ben
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spyder



Joined: 24 Sep 1996
Posts: 2790
Location: oahu

PostPosted: Thu Jul 20, 2000 12:07 pm    Post subject: RE: Fin Size? Reply with quote

Fin selection is based on a number of things, such as: sail size, board type & size, water condition (chop, wave, f lat), and you!

Generally speaking, the fin size is proportional to the sail/board size, for 2 reasons - you need more force to get the board planing, and to prevent the board from spinning out. But is
still affected by other parameters, like your weight, style of sailing, and direction of water current.

For the water conditions, you usually would use a blade for flat water, a convertible for bump and jump, and a wave fin for wave condiitons. However, depending on the style of sailing you want to do - such as racing or tricks, you might decide to use a different fin. For example, you might use a wave fin in bump and jump, because you want a more reactive or slashy feel. The fin is also suited to the board selected, if you are sailing in flat water, you are taking a board with a flat rocker, and most likely a blade fin (but a convertible will work too). If it is choppy/wavey then you will pick a board with more rocker and fin that is suited for choppy /wave conditions. Also if there are a lot of weeds in the water, you might consider a weed fin. This helps get you going, and the weeds pass the fin easier.

For example, I would sail my 6.0/6.5 with a 34cm convertible (or blade) fin on a fairly flat board (94 Axxis 278). If I went to a 7.0/7.5, and my AHD 289 Free, I probably would pick my next bigger fin, 38cm. If the fin starts to ride out of the water when really cranked fin walking, then I might go down in fin size.

The fin should allow you to get on a plane quickly in the conditions, and provide enough lift to keep the board planing. If it is too much, the board will rise out of the water when going fast.

Confused? well, I think the best thing is to see what people are using where you sail, and consider the differences in what you are sailing, and your weight.


hope this helps.
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bmergen



Joined: 13 Jun 2000
Posts: 16

PostPosted: Thu Jul 20, 2000 2:16 pm    Post subject: RE: Fin Size? Reply with quote

That does help. I am new to the sport. I have one board, Hifly 275FX(102L) and one sail, NP 4.5. The fin I have is 34cm, which I have determined is way to big. I only weigh 150lb but am fairly strong. When Im powered up, hooked in, and in the straps, I feel like I have just barely enough strength to drive the tail of the board with my back foot to stay up wind. This is especially true during gusts, even with a lot of downhaul(is that the correct term?) to give the sail good twist off. I often get worked quite a bit and feel out of control. I havent really experienced the fin walking you talked about though. Ive been looking at fins in the 24-29cm range. I hope to find a cheap one in that size range and give it a shot. By the way, all of my sailing has been in the gorge.
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spyder



Joined: 24 Sep 1996
Posts: 2790
Location: oahu

PostPosted: Thu Jul 20, 2000 7:15 pm    Post subject: RE: Fin Size? Reply with quote

Ben -

I dont know what type of fin you are using, but definitely 34cm fin is too big for a 4.5.

I would get something more like 25 cm, a convertible or wave fin ( swell & chop conditions).
I also would try and get the best fin possible (maybe a good used one). I think there are a lot of good fins out there, FinWorks, TrueAmes, Maui Fin Co.

Also if you are new to hooking in and the footstraps, make sure you are sheeting in all the way. If you are sheeting out, that will cause a lot of control problems.

Check your mast base position in the mast track and the location of the harness lines. When in the footstraps, the Center of Effort of the Sail should be balanced, and you will feel comfortable when hooked in and in the footstraps.

As for the sail rigging, a lot has to do with the conditions. Try to make sure you set the boom and luff to the correct settings marked on the sail. Then the downhaul should be enough give good sail response, but not so much the sail looses its performance. Remember if its too windy, the 4.5 may be just too much sail, and you need a 4.0 or even 3.5. The fin will need to decrease in size as well
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bmergen



Joined: 13 Jun 2000
Posts: 16

PostPosted: Fri Jul 21, 2000 11:04 am    Post subject: RE: Fin Size? Reply with quote

I just got a no-name fin at 2nd Wind because it was cheap. There were three or four Made in China stickers on it. Its 9.75, ~25cm. It doesnt have quite as much sweep to it as a real wave fin, but a lot more than my 34cm. I was out at the hook (bad idea) on wednesday. There wasnt quite enough wind to be fully powered, but during the gusts it felt pretty good. I figured I would experiment with a cheap one to get a feel for the affect of changing fins, then go for a good one. The spots Ive been sailing mostly, HR Marina, Bingen Marina, The Hook, have shallow spots that can be hard on the fin anyway. Also, in your previous message, you mentioned mast base position in the mast track and the location of the harness lines. Is there a way to determine a good starting point for these on dry land to have a good point to work from? Any rules of thunb for these so when fully powered and sheeted in everything is in the right place and balanced?

Thanks a lot for your input.
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spyder



Joined: 24 Sep 1996
Posts: 2790
Location: oahu

PostPosted: Fri Jul 21, 2000 1:27 pm    Post subject: RE: Fin Size? Reply with quote

I check the harness lines on land by trying to hold the sail with one hand (with wind pressure on the sail), and that determines about where the COE of the sail is . Then I center my harness lines around that position.

Then when positioning the mast base on the board, this has to do with sailing position, with respect to the type of sailing. For slalom, you will be totally sheeted in with the foot of the sail nearly touching the board (when fully planing), you want the harness lines to be pulling equally and centered on the COE of the sail. (youre in the foot straps) If they pull from the front or back, you need to move them accordingly.
It should feel comfortable and easy to sheet the sail in.

With wave sailing, the sail foot is not near the board, but you are sheeted in. In that position, the harness lines should be centered on the COE, when you are in the foot straps. Again, pulling front or back, you need to adjust.

Then there is the setting of the harness line length. At first you want to keep them long enough to easily get in and out (but not too long), then depending on what type of sailing you do and the type of harness, you want to set them so you can sheet completely in when in the planing stance. Generally quite short for slalom sailing, and somewhat longer for bmumpnjump / wave sailing (cuz you need to get out easily.

A lot of this will be a personal preference as you get more experience. Try experimenting, you will get the best performance when it is tuned to you. But at first try to set it with the guidelines, and go from there.
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hamblett



Joined: 29 Jun 2000
Posts: 40

PostPosted: Mon Jul 31, 2000 12:55 pm    Post subject: RE: Fin Size? Reply with quote

You mention that you use your 94 Axxis 278 with your 6.0/6.5 and an AHD 289 with 7.0/7.5.

I have a 96 Screamer II CGI (278, 103l) that I try and use with my 1999 7.0 North as much as possible. Unfortunately I feel under-finned most of the time when Im trying to sail in 12-15mph. When the winds hit 15-20 Im fine. The fin that I was using is a 35cm slalom blade. I dont think its enough area for the lighter stuff.

Im thinking of upgrading to a True Ames 44 or 46 Blade but am uncertain as to whether or not this is a good decision.

Any recommendations?

Also, with this size sail, Im having problems finding the sweet spot for the mast track position. Ive tried all the way back (definately not it!), all the way forward (better but still not quite balanced. I Couldnt go upwind). Next time out, Im going to try a few cm back from the front and see if Im getting closer.

Specs say that this board should handle a 7.0. Am I pushing it? I weigh 165-170 and usually put my boom at shoulder height or a little above. Harness lines were 22 but I have recently made them shorter and adjustable. I had Too much load in my arms and couldnt plane very easy.

Good thread so far! Very informative.
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spyder



Joined: 24 Sep 1996
Posts: 2790
Location: oahu

PostPosted: Mon Jul 31, 2000 4:29 pm    Post subject: RE: Fin Size? Reply with quote

IMHO, a 7.0 on your screamer is probably pushing it. However it will work, but barely. You will probably feel like you need a position farther back...indicating the board is too small (but first move the mast base to the front).

Your idea of the bigger fin is good, I think the smaller one (44 cm) is better. Ive had very good luck with True Ames, so another good idea. But the 35cm fin is too small for a 7.0.

I would shorten the harness lines as much as you can tolerate, and move the mast base forward (as you said). Thats about as much as you can do. Of course assuming the sail is correctly rigged and harness lines are balanced.

I like my boom pretty high when sailing a large slalom, and harness lines short. This give me the best stance when fully sheeted in.
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hamblett



Joined: 29 Jun 2000
Posts: 40

PostPosted: Mon Jul 31, 2000 9:18 pm    Post subject: RE: Fin Size? Reply with quote

What do you mean by your first paragraph? Ive never heard that before. Too large a sail makes board feel like the mast track needs to be set back?

Ive been attempting to minimize my equiment investment, hence the one board, but I figured a 7.0 was borderline. Hopefully the wind will be up within the next few days so I can continue testing. Well see though.

If I do go out, I am going to sail my 14 Fox Weed fin. Its the boggest fin I have at the moment. I could use the stock Mistral fin but its pretty much a trashy fin. I dont like it at all.

I agree with shorter harness lines. Right now theyre set to be about 17 with adjustment to about 22 or so. I havent tried this short a line with this sail so I hope this works out.

Thanks for the info!

Adam
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spyder



Joined: 24 Sep 1996
Posts: 2790
Location: oahu

PostPosted: Tue Aug 01, 2000 12:45 am    Post subject: RE: Fin Size? Reply with quote

sorry if I wasnt not clear. What I meant was you feel like you want to position your feet farther back with the bigger sail, if the board is too small. Thats simple because you are fighting the COE of the sail (Center of Effort), if its not at a comfortable position.

As for the mast base, you would want to move that forward to get COE of the sail in the correct position with respect to your stance when sheeted in/footstraps.
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