Hi Peeps. I need to buy a weed fin and I'm confused by size. Is it true I need to buy a weed fin that's several inches shorter than my standard slalom fin? I assume this is because of the rake measurement from tip to base?

My new 115ltr Tabou Rocket came with a 42" slalom fin. I'll be using sails from 5-7m on it and I weigh in at around 86 kegs hungry. What size weedy should I be looking at buying if I only buy one size (for the moment)?

Thanks in advance.

depends on where are you sailing, if its chop you need a longer fin , if its shallow water you need a shorter length but longer chord
ok for the guy that red thumbed me have a think about it here's a few sessions from mudskipper on old gear using a 17cm short based weed fin


www.gpsteamchallenge.com.au/sailor_session/show?date=2014-01-17&team=34
www.gpsteamchallenge.com.au/sailor_session/show?date=2014-01-05&team=34
ka360 on a keef 17cm good size chop
have a look at MT 40KNTS + 56CM wide board 20cm weed fin in descent chop , the best speed was on flat water but you have to sail through chop to get to it
the biggest fin I use is a 22cm wide base with a 7.2mt sail

Weed fins don't have the same lift as slalom or freeride, so you need a longer one, not shorter. The rule of thumb is to buy a fin that has the same depth as your slalom fin length .

Some brands are better upwind than others. Makani seem to be pretty wide at the base and I find they go upwind well.

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powersloshin said..

Weed fins don't have the same lift as slalom or freeride, so you need a longer one, not shorter. The rule of thumb is to buy a fin that has the same depth as your slalom fin length .

ill agree with powersloshin and get youself a 42cm weedy

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keef said..

powersloshin said..

Weed fins don't have the same lift as slalom or freeride, so you need a longer one, not shorter. The rule of thumb is to buy a fin that has the same depth as your slalom fin length .

ill agree with powersloshin and get youself a 42cm weedy

Thanks for the info guys!

Get a 36cm Flyong Objects or JP weed fin for that board.

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ka43 said..

Get a 36cm Flyong Objects or JP weed fin for that board.

What's the reasoning behind a smaller fin than the one supplied? Should I also consider getting something smaller as standard too?

Hi mate
I recently picked up 2014 115L Rocket and it's one of the best boards I've had. In terms of weedys I have 31 jp weed /slalom for powered up 5.5-6.5 range. Also a 36 jp weed / slalom for 6.0 - 7.8

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keef said...

powersloshin said..

Weed fins don't have the same lift as slalom or freeride, so you need a longer one, not shorter. The rule of thumb is to buy a fin that has the same depth as your slalom fin length .

ill agree with powersloshin and get youself a 42cm weedy

Not too sure about using a 42 weedy in the 115L that is 66 wide maybe in the 125L that is 69 wide

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ka43 said..

Get a 36cm Flyong Objects or JP weed fin for that board.

hey larko I believe you have custom weedy

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ka43 said..

Get a 36cm Flyong Objects or JP weed fin for that board.

JP Weed 36 works really well for me on 115L board.

I use to use a 40cm weedfin on an 80 cm wide slalom board with an 8 m sail, regular slalom fin was 48cm. 42 cm weed on a 115 L freeride board is going to be huge, and not work very well. I am using a 23 on a fsw 110 up to 6m and a 28 for 7-7.5 with inboard footstraps. The 28 i also used with a 7m slalom sail on a 105 rocket 61 wide. On the rocket you would need a some more fin. I think 32-36 would be good on the rocket from 6-7m, but definately not 42...

Just as a rough guide I use the following weedies:
Falcon 125 79 wide with 7.8 = 36cm
Falcon 112 69 wide with 7.0 to 7.8 = 32cm
Falcon 99 63 wide with 6.4 to 7.0 = 25cm Be aware thus combo is usually sailed in pretty flat water and shallow too.
Falcon 79 56 wide with 5.8 to 6.4 = 19cm Same as above.
Like a lot of guys these days I have cut down fins, made them have more rake and re-foiled etc.
You can get away with smaller fins, just ask Keef
There are heaps of brands out there, also look at Black Project, Maui Ultra, JP, Flying Objects.

go to www makanifins com/pages/windsurfing-fin-selector {NO more links allowed ?}
for 115 liter board with around 7 sq meter sail - 38 cm weed fin Hahalua
if i do selection based on width i come up with the same fin suggested

i use a 44 cm weed fin with sails where i would normally use a 48
the leading edge of the fin is much more and the chord on some weed fins is more
especially the Hahalua
i had issues making that fin fit my box - fellow windsurfer had same issue
have the shop fit it for your main board

here some people use weed fins when there are no weeds - je ne comprends pas
perhaps you can try one at the location or from local shop ??

Agree with aus1023, my 115 came with a 38cm fin and I've found a 35cm weedie works well with a 7.1m sail. I'd say a 42 might be a bit much.

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2035 said..

ka43 said..



Get a 36cm Flyong Objects or JP weed fin for that board.

What's the reasoning behind a smaller fin than the one supplied? Should I also consider getting something smaller as standard too?

Normally the size of a weed fin indicates it's depth, not length, so a 36 weed fin would be longer than 36, the longer the higher the rake. Also checked my weed fins and what I said before is wrong, you can use a weed fin with less depth than your slalom one...
One more thing no one has mentioned is that the first time it will feel hard to sail with a weed fin: harder to go upwind, more prone to spin out and uncomfortable stance.

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powersloshin said..

2035 said..

ka43 said..



Get a 36cm Flyong Objects or JP weed fin for that board.

What's the reasoning behind a smaller fin than the one supplied? Should I also consider getting something smaller as standard too?

Normally the size of a weed fin indicates it's depth, not length, so a 36 weed fin would be longer than 36, the longer the higher the rake. Also checked my weed fins and what I said before is wrong, you can use a weed fin with less depth than your slalom one...
One more thing no one has mentioned is that the first time it will feel hard to sail with a weed fin: harder to go upwind, more prone to spin out and uncomfortable stance.

How does the stance vary? My 115ltre 78cm? wide board came with a 38cms fin and I use that with 7.5m + 6.6 although in shallow water I've used a 30cms and only spun out occasionally when I forgot and used too much rear foot pressure.

on Patrik 115 (69 wide) i usually use a 42 slalom or will use a 36 weedy if in botany and a 24 Delta for lake illawarra.

On JP 59 wide slalom i use a 34 slalom for normal , 28 Flying object speed weed (lake george) and a 18 Delta for lake illawarra.

Depends on depth / amount of weed and chop you sailing in.

Used 7.0 TRX on all these combos.

Thanks for the advice and info. I purchased a 34cm Flying Objects weedy (and a 36cm C3 Venom at the same time)... based on the research Ive done and info from other forum members, I'm not sure why a 42" was recommended. Will post feedback on how the Flying Objects goes with the rocket. Hoping for a decent Southerly this weekend.

Check out our WeedSPEED size guide - http://www.blackprojectfins.com/products/windsurf-fins/weedspeed/ we actually name them with an equivalent size rather than the depth, this should help, the depth is also shown. Sizes 25/28/31/34/38/42

This is the fin which Brad Anderson used to set the one hour world speed record.

I think one of the unaddressed issues is BOARD SPEED.
I've never used a weedie, but with the same 7.7m sail I can use a 32cm fin or a 48cm fin.
The 32 'works' when I'm going 25kts plus, on a small 90L board, and the 48 is more suitable to a 120L board sub 25kts...

Good luck finding the right fin.

im not sure if you could call BP a weed fin at 38deg ,they mite get rid of the occasional floating weed but wont go through heavy weed , BP also measure from the bottom of the base so a 28cm is realistically a 24cm , maybe they have changed there method of measure