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How much difference will longer fin make?
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jwallace



Joined: 09 May 1998
Posts: 124
Location: SF Bay Area

PostPosted: Tue Aug 07, 2012 7:09 pm    Post subject: How much difference will longer fin make? Reply with quote

Currently sail on a older Bic Veloce. 278 cm / 101 ltr. Still sailing on the stock fin (32 cm). Looking for something that will help with planing in lighter wind. I am 185 pounds and mostly sail Berkeley. However, I find that when the wind isn't solid 23+, it is hit and miss planing. Someone suggested a longer fin (e.g.,42 cm). Wondering how much difference that will make. I know getting a 110/115 ltr board would really help... but don't have the budget for that.

Thx!
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nw30



Joined: 21 Dec 2008
Posts: 1807
Location: The eye of the universe, Cen. Cal. coast

PostPosted: Tue Aug 07, 2012 8:56 pm    Post subject: Reply with quote

A bigger sail will help you more than a bigger fin, but a longer fin (pointer type, a straight blade) will help you go upwind more better.
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sailingjoe



Joined: 06 Aug 2008
Posts: 1087

PostPosted: Wed Aug 08, 2012 5:15 am    Post subject: Reply with quote

A longer fin might help incrementally, but what you really need to plane up in marginal conditions would be a fin with a wider chord. Most weed fins will do the job better than anything else. However, a low aspect upright or curved fin might be for you. Chord is the width of the fin. Span is the length. Be careful about people who say that you need a longer fin without talking span. The ratio of chord to span makes up your aspect.
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PeconicPuffin



Joined: 07 Jun 2004
Posts: 1221

PostPosted: Wed Aug 08, 2012 6:26 am    Post subject: Re: How much difference will longer fin make? Reply with quote

jwallace wrote:
Currently sail on a older Bic Veloce. 278 cm / 101 ltr. Still sailing on the stock fin (32 cm). Looking for something that will help with planing in lighter wind. I am 185 pounds and mostly sail Berkeley. However, I find that when the wind isn't solid 23+, it is hit and miss planing. Someone suggested a longer fin (e.g.,42 cm). Wondering how much difference that will make. I know getting a 110/115 ltr board would really help... but don't have the budget for that.

Thx!


Adding 10cm of fin is quite a leap. Also, is this a trimbox board? If it is, the investment in a larger fin (if you can find one) is a bit of a dead end...you won't be able to use it on any powerbox boards you may own in your future (one of the beauties of fins is that they last a very long time if you take care of them.) If you have access to one, I'd try something around 36 cm.

Two btw's:
1. It's not the liters that get you planing. A modern 100 liter board would almost surely plane much earlier for you.
2. What sails are you using in these conditions?

_________________
Michael
http://www.peconicpuffin.com
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cgoudie1



Joined: 10 Apr 2006
Posts: 1279
Location: Killer Sturgeon Cove

PostPosted: Wed Aug 08, 2012 9:48 am    Post subject: Re: How much difference will longer fin make? Reply with quote

A fin with more surface area will plane you up more often if, you're close
to the planing threshold. A higher aspect (longer) fin will be more
efficent (faster and lower drag). A longer fin that is the same surface area
as your current fin will buy you a tiny bit of earlier planing because of the
efficiency, but you really want more surface area.

-Craig

jwallace wrote:
Currently sail on a older Bic Veloce. 278 cm / 101 ltr. Still sailing on the stock fin (32 cm). Looking for something that will help with planing in lighter wind. I am 185 pounds and mostly sail Berkeley. However, I find that when the wind isn't solid 23+, it is hit and miss planing. Someone suggested a longer fin (e.g.,42 cm). Wondering how much difference that will make. I know getting a 110/115 ltr board would really help... but don't have the budget for that.

Thx!
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steve1



Joined: 30 Apr 1998
Posts: 236
Location: Alameda, CA

PostPosted: Wed Aug 08, 2012 10:57 am    Post subject: Reply with quote

Yes a bigger (longer and/or more surface area) will help you plane earlier by converting side-slip into forward motion. However, even with ultra efficient high end fins, there will be some additional drag, so you will need enough sail power to overcome it.

I also sail Berkeley and used to be 185lb before I lost 20lb. I have a 117l and a 104l board and use fins which are +10-20% over the recommended sizes. I use 6.3m2 and 7.5m2 sails with them.

In lighter winds I reduce the downhaul and/or outhaul to give me a deeper draft and more power in the sail.

The biggest factor at Berkeley is to sail where the wind is - which is typically outside of the line between the restaurant and Emeryville. If you are launching from the boat dock and carpets, you will need a good fin to get you there.

This combination gets me from the rigging area up to the restaurant and beyond in one gybe or tack and I am often one of the few non-formula guys that's up and planing in lighter wind days.

I'd be happy to chat. I usually rig on the carpet and drive a Honda Odessy. I have a blue and white 6.3m and a green and white North Spectra 7.5m2.

Steve
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sailingjoe



Joined: 06 Aug 2008
Posts: 1087

PostPosted: Wed Aug 08, 2012 12:57 pm    Post subject: Reply with quote

This past week I have been going over my notes on the question of early planing. I have also had some hard core experiences to verify the claims. First of all, you have to separate early planing and planing in marginal winds. Early planing assumes that you are going to plane in the conditions you have, planing in marginal winds would not make that assumption. In addition you have to consider ease of "getting in the straps", and the fact that your planing can improve once in the straps. A weedfin with a wide chord will be stabler at slow speeds than other fins. That makes it easier to get in the straps. Now, from what I have read primarily on the internet, I have concluded that a larger fin planes up earlier than a smaller one and that fins with less rake angle plane up earlier than those with a more pronounced rake angle. I have found my large weedfins useful to me. I assumed that they were planing up in marginal conditions while an upright would not. Recently, I tested the hypothesis. I used a Tectonics Mirage course racing fin in marginal conditions. When I switched to a Hydrotech weedfin of comparable size but a wider chord, lower aspect, and more area, I was planing with ease. Here is a photo of the two fins.


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Last edited by sailingjoe on Thu Aug 09, 2012 7:07 am; edited 1 time in total
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jwallace



Joined: 09 May 1998
Posts: 124
Location: SF Bay Area

PostPosted: Wed Aug 08, 2012 1:36 pm    Post subject: Reply with quote

Thx everyone for your replies. Most helpful. A few comments / replies:

- On a 25 mph day, I'll be happily on my 5.4 (planing, jibing, straps, bump/jump, etc.). I recently purchased a new 6.3 and tried it out last Thurs (Aug 2) at 5:30pm. I just missed a pretty large push of wind that ended as soon as I got in the water. It was hit and miss planing for an hour (18 mph, gusts up to 23, lull down to 15). The 6.3 was to replace an older 5.7 which I didn't think was a big enough jump from the 5.4. Surprised that the 6.3 didn't give me the range I though it would. I had thought that the 6.3 would give me consistent planning with winds 18+.

- As with most regulars at Berkeley, I am familiar with how the sensor can be off -- sometimes significantly. Typically, I don't even bother with Berkeley unless I see a pretty regular blow of 23. But since life choices don't afford me the opportunity to frequently go to my other locations I used to sail (Delta, Stick, Crissy), I am trying to make the most of Berkeley and Pt. Isabel (which seems even more iffy these days).

@PeconicPuffin: A couple years ago (~2009/10) I demoed a 100 ltr freestyle board. I did notice the planning was muuuuch quicker. However, I found the board to be way more squirrely and unstable. I was not sure if this was because of a shorter board and/or lighter weight.

@steve1: Thx, Steve. I'll look for you next time I'm out. If the docks are sailable, I'll deal with slogging out to the heavier wind just so I get a better rigging space. I've sailed many times out of the restaurant, but I tend to launch from there if it looks like it will take forever to get out there. Restaurant is nearly as gross as the Stick.


Last edited by jwallace on Wed Aug 08, 2012 3:43 pm; edited 1 time in total
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dhmark



Joined: 04 Sep 2007
Posts: 216

PostPosted: Wed Aug 08, 2012 2:23 pm    Post subject: Reply with quote

If it is old BIC, trim box fins are sometimes hard to come by; on the other hand, good deals often to be had on EBay for this now obsolete box. Definitely give it a try with the bigger fin. As I recall, 6.3 to 7.0 was the most common sail to use at Berkeley, a lot of sailing to be done at those windspeeds. dhmark (learned to sail Berkeley 20+ yrs ago).
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cgoudie1



Joined: 10 Apr 2006
Posts: 1279
Location: Killer Sturgeon Cove

PostPosted: Wed Aug 08, 2012 2:53 pm    Post subject: Reply with quote

Hmmm, at 185 lbs, if the real wind is 15-23 averaging 18, I can plane up
my 95 ltr 9'1" RRD with a 6.7, very consistently, and a 5.5 most of
the time. I think the skeg on that thing is about a 40 cm sweeper, so
pretty verticle. If you're not bumping up the skeg to match your sail
you're probably not getting full potential, but that 6.3 rig should work
pretty well in 15 to 23. You might try moving the mast track around
a little (I'd try forward 1st, but it depends on where your wide point is).

-Craig



jwallace wrote:
- On a 25 mph day, I'll be happily on my 5.4 (planing, jibing, straps, bump/jump, etc.). I recently purchased a new 6.3 and tried it out last Thurs (Aug 2) at 5:30pm. I just missed a pretty large push of wind that ended as soon as I got in the water. It was hit and miss planing for an hour (18 mph, gusts up to 23, lull down to 15). The 6.3 was to replace an older 5.7 which I didn't think was a big enough jump from the 5.4. Surprised that the 6.3 didn't give me the range I though it would. I had thought that the 6.3 would give me consistent planning with winds 18+.

.
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