Shame they don't come in smaller sizes. Need <20cm for many of the fast spots here in NSW.
I think I recall BP fins lengths are quoted along the length rather than perpendicular - but I'm not 100% sure on that.
Gareth can best confirm that.
Select to expand quoteN1GEL said..
Shame they don't come in smaller sizes. Need <20cm for many of the fast spots here in NSW.
The smallest 25 is actually 20cm deep.
Select to expand quotelegless said..
N1GEL said..
Shame they don't come in smaller sizes. Need <20cm for many of the fast spots here in NSW.
The smallest 25 is actually 20cm deep.
20 deep is sweet. Wouldn't mind trying one out. Would it have a bit less lift than a MUF Delta of the same size?
Select to expand quote
DavMen said..
I think I recall BP fins lengths are quoted along the length rather than perpendicular - but I'm not 100% sure on that.
Gareth can best confirm that.
BP fin size is a number they have come up with which they feel is the equivalent size to a upright fin....it is a bit confusing
Here are the Weed Speed 50 sizes
Select to expand quoteN1GEL said..legless said..N1GEL said..
Shame they don't come in smaller sizes. Need <20cm for many of the fast spots here in NSW.
The smallest 25 is actually 20cm deep.
20 deep is sweet. Is it okay to ask how much they are?
It is all going to depend on the value of the AUS$ to the US $ but they will be well over $200 a fin
Select to expand quotelegless said..N1GEL said..legless said..N1GEL said..
Shame they don't come in smaller sizes. Need <20cm for many of the fast spots here in NSW.
The smallest 25 is actually 20cm deep.
20 deep is sweet. Is it okay to ask how much they are?
It is all going to depend on the value of the AUS$ to the US $ but they will be well over $200 a fin
It's only going to get worse when the US Fed raises rates 
Select to expand quotelegless said..
BP fin size is a number they have come up with which they feel is the equivalent size to a upright fin....it is a bit confusing
Here are the Weed Speed 50 sizes
BP are saying that a 20cm 50deg-rake fin, is like a 25cm upright fin?
Anyone that has sailed a raked fin will always tell you it needs to be bigger wrt an upright.
Select to expand quotemathew said..
BP are saying that a 20cm 50deg-rake fin, is like a 25cm upright fin?
Anyone that has sailed a raked fin will always tell you it needs to be bigger wrt an upright.
That's not correct I think you are getting mixed up with surface area and depth a raked weed fin will have a greater surface area than an upright fin of the same depth. The rake of the fin and shape of the fin it a FWD design will determine how it will perform compared to a upright fin.
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Soon as i get some demo fins will bring down to budgy to try in the weed , Hopefully soon
Select to expand quoteaussieboats said..
Soon as i get some demo fins will bring down to budgy to try in the weed , Hopefully soon
That'd be great. Cheers!
Nice plan shape.
I am still puzzled why board manufactures put the fin boxes so far back. With an upright fin with a root chord of 10-9cm there would still be plenty of support with the fin in the back of the base if the box was 4-5cm further forward.
Then with the box further forward you could give a bit of support to the leading edge/quarter chord load point of a weedy.
ie something like this for the smaller versions...
Select to expand quoteyoyo said..
Nice plan shape.
I am still puzzled why board manufactures put the fin boxes so far back. With an upright fin with a root chord of 10-9cm there would still be plenty of support with the fin in the back of the base if the box was 4-5cm further forward.
Then with the box further forward you could give a bit of support to the leading edge/quarter chord load point of a weedy.
Why did the trim box fall out of favour? They'd be just the thing for speed boards where shallow weedy water is now the rule rather than the exception.
Why did Netscape and Myspace die and IE and Facebook thrive? Chance/rub of the green? I think with the original trim box it was used mainly in plastic (ABS?) boards which had an Aluminium extrusion for the base. The company making the extrusion went out of business in France and Tiga and Bic decided the easiest option was to join the others and go Tuttle rather than continue doing their own thing. (well that was my understanding.)
Have had trimbox fins on slalom gear (oops, age showing), and I am happy they were replaced by tuttle box.
Basic design is better, more stable, once your fin fits well of course.
But IMO the problem of production tolerances is not related to the design principle.
Reason to put the box far back is performance. You get the same problem with slalom or speed fins, you now have with weedfins in center position - the board does not run free and trim feels off.
Weed is a problem is small proportion of spots. And normally not a problem at the locations where actual racing is organized. IMO moving the finbox forward would make board trim worse for > 80% of sailing locations.
I can imagine it's a problem for recreational use of slalom gear for speedsurfing, in shallow weedy spots. This can be solved with weedfins like the ones in this thread.
All true, but not really 'Solved' with these type of fins. The forward projection is always a problem to prevent strands of weed catching, and one strand destroys speed!
It also puts the Boards skin at risk when fitting and removing..... Be careful folks!
Also, with actual dedicated speed boards (under 45cm wide) the fins are usually small enough that mounting the fin right forward in the base is fine with at least 40 degree raked fins. IMHO, a lot of the GPSTC challenge sailors go too large in the fin department for best top speeds when conditions are really good. I can understand why, especially with 50 degree plus rake which can really negatively impact lift efficiency. Larger fins can give more confidence, make upwind and starting a lot easier. But when 30-40 degree rake is all you need, smaller is usually faster.
I'm also glad we have Tuttle boxes now. I used to hate trying to get the wobble out of trim box fins.
ok, now to embarass myself with an ignorant question 
the " trim" issue with a weed fin is the centre of fin lift is further back and flattens the board out too much?
if so, will moving the mast base back and boom up help to counteract that and generally get more board out of the water, so faster If windy enough?
i really don't understand the science that well, so happy to be educated....
Stretchy, in my understanding it's more about getting the centre of sail lift over the centre of fin lift, in a manner that's optimum for rider's weight to trim the board efficiently.
Thanks Mike. So bringing the sail centre back would surely be faster than bringing the fin centre forward, if one is only focussed on speed? Obviously there would be compromises elsewhere.
Raking the fin back actually moves the centre of resistance BACK. All else being equal, this will trim the nose HIGHER.
The qualification 'all else bing equal' is important, because if you move the centre of resistance back but leave the footsteps and mast base where they were for the vertical fin, it may counteract the fins CofR movement effect and keep the board flatter.
So, your guess is correct. Your stance (combination of both front and back straps) needs to come back slightly and mast track as well. Get these right and the board can actually ride more nose up which is great for top speeds on flattish water! 
Select to expand quoteStretchy said..
Thanks Mike. So bringing the sail centre back would surely be faster than bringing the fin centre forward, if one is only focussed on speed? Obviously there would be compromises elsewhere.
Bringing the sail centre back also involves the rider's weight moving back, so this could cause the tail to sink too much.
True at low to moderate speeds. Usually not an issue at 35-40 knots +. The less board in the water the better at those speeds
Select to expand quotesailquik said..
Raking the fin back actually moves the centre of resistance BACK. All else being equal, this will trim the nose HIGHER.
The qualification 'all else bing equal' is important, because if you move the centre of resistance back but leave the footsteps and mast base where they were for the vertical fin, it may counteract the fins CofR movement effect and keep the board flatter.
So, your guess is correct. Your stance (combination of both front and back straps) needs to come back slightly and mast track as well. Get these right and the board can actually ride more nose up which is great for top speeds on flattish water!
I agree Daffy, at Lake George this year when using BP 40 deg speed weeds and Tribal speed weeds, I set my mast track towards the back of the track but left my foostraps in the same position. I found that when the wind was strong enough, you could fly the tail, with a nose up. When really going only the last 400mm of the board was in the water
Select to expand quotelegless said..mathew said..
BP are saying that a 20cm 50deg-rake fin, is like a 25cm upright fin?
Anyone that has sailed a raked fin will always tell you it needs to be bigger wrt an upright.
That's not correct I think you are getting mixed up with surface area and depth a raked weed fin will have a greater surface area than an upright fin of the same depth. The rake of the fin and shape of the fin it a FWD design will determine how it will perform compared to a upright fin.
... and Physics disagrees with you. It it the "vertical length seen by the water" that is the dominant element in the lift calculations.
so "all things being equal" [ as Daffy put it ], larger surface area does work out higher lift if that is what you are aiming for.
Obviously there are other reasons to rake a fin - we know from experience (and the math supports this) that as speed increases, the AoA of the board/water gets bigger, so you need more rake in your fin. Similarly the CoF of the total package "moves back" - so having a raked fin helps as your waterline is reduced.
But that isn't what is presented in the chart -> it says a 20cm Black-magic fin is like a 25cm vertical fin.
testing is done , i think first stock of fins around xmas , but all reports are excellent fins
OK. Premature release?
What options are out there available now for 45 and 50 degree, smaller weedies? (<20cm deep)
30-40 degree weedies I have well covered.
