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Delta & MUFins order

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Created by fangman > 9 months ago, 14 May 2014
fangman
WA, 1074 posts
14 May 2014 11:21AM
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Hi all; I am looking to send off another order to Maui Ultra Fins for both Delta and conventional fins. Because freight is a bit of a killer, the more fins I order in, the wider the cost is spread,that is,it's cheaper. The Maui Ultra Fins Delta also come in honeycomb lay up in the bigger sizes. They are much lighter than the G10 but I am not sure how they fare with wear into the honeycomb layer if you prang the fins into the dirt as often as I do. MUF are also bringing out Carbon versions of a number of their fins soon, including the Deltas, but same deal with wear issues as the honeycomb lay ups. Pricing is essentially what's on the website,(it's US dollars) but if I can get enough the freight is free. If anyone in Perth and surrounds is interested in jumping in as well please pm me on fangman. Cheers.

Windxtasy
WA, 3939 posts
14 May 2014 2:25PM
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fangman said..

Hi all; I am looking to send off another order to Maui Ultra Fins for both Delta and conventional fins. Because freight is a bit of a killer, the more fins I order in, the wider the cost is spread,that is,it's cheaper. The Maui Ultra Fins Delta also come in honeycomb lay up in the bigger sizes. They are much lighter than the G10 but I am not sure how they fare with wear into the honeycomb layer if you prang the fins into the dirt as often as I do. MUF are also bringing out Carbon versions of a number of their fins soon, including the Deltas, but same deal with wear issues as the honeycomb lay ups. Pricing is essentially what's on the website,(it's US dollars) but if I can get enough the freight is free. If anyone in Perth and surrounds is interested in jumping in as well please pm me on fangman. Cheers.


I'd like enough wind to try the one I already have...

sboardcrazy
NSW, 7511 posts
14 May 2014 5:32PM
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Windxtasy said..

fangman said..

Hi all; I am looking to send off another order to Maui Ultra Fins for both Delta and conventional fins. Because freight is a bit of a killer, the more fins I order in, the wider the cost is spread,that is,it's cheaper. The Maui Ultra Fins Delta also come in honeycomb lay up in the bigger sizes. They are much lighter than the G10 but I am not sure how they fare with wear into the honeycomb layer if you prang the fins into the dirt as often as I do. MUF are also bringing out Carbon versions of a number of their fins soon, including the Deltas, but same deal with wear issues as the honeycomb lay ups. Pricing is essentially what's on the website,(it's US dollars) but if I can get enough the freight is free. If anyone in Perth and surrounds is interested in jumping in as well please pm me on fangman. Cheers.


I'd like enough wind to try the one I already have...


Sounds like it's the same over your way as here....

tobyr
WA, 68 posts
14 May 2014 7:23PM
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Hey Fangman. What size and type of Deltas are you running down your way?
I have a 25cm Vector speed weed, would I get away with this at Fangdurah and Albany or should I bite the bullet and get a delta to run down there.

decrepit
WA, 11079 posts
14 May 2014 7:56PM
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Toby, a lot depends on the tide, and if you want to get into the really thick weed.
The Albany weedy is thick on the surface when it's still waist deep, it's where the isn't that you have to be careful, but the longer and more vertical the fin is the more weed drag there is. A 25 will get you in there, but you'll feel the drag.
Fangys at low tide, is best with sub 20cm fins. Today with winter water levels I was fine with a 29cm fin

This old brain works slowly now, but it's been long enough since our last conversation about weedys to have had a few thoughts.

The main difference between a good weedy, and I need to stress GOOD, (needs to be very stiff and not too thin.) Is even the best weedys won't produce any vertical lift, although horizontal lift can be similar for the same depth.
So if you've tuned your settings to include fin vertical lift, you'll need to change stuff. As the fin is behind the rider's center of gravity vertical fin lift, pushes the nose down and lifts the tail, so if that's no longer there, you could end up with the tail too low and nose too high, so you need to shift the center of gravity forward.
The other thing especially with longer fins is the center of horizontal lift is further back with a weedy, so the center of effort of the sail needs to move back to stay in balance.
With a delta style or shorter fin this effect probably won't be noticeable.

fangman
WA, 1074 posts
14 May 2014 11:28PM
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Hey Toby, Plus one on what he said, not that I understand much of Decrep says these days. Fangy's works best the shallower it is and heavier the outer weed bank is. This occurs Spring and early Summer on low tides. You need the delta or high rake fin to negotiate the outer weed bank with safety and then because the inside is shallow you are pretty much stuck with the high rake wide base style of fin in order to get enough surface area. In winter the tides are generally higher so your vector would be fine most of the time. So most of last season I was using a 21cm Delta ride. I crashed this into the real estate a lot! It's now 16 cms. And still works a treat. I purchased a 18cm Delta speed but I really haven't had the chance to try it out in the right conditions to see how much faster it is than the normal Delta foil shape. The vector will be great if you stay outside the weed bank which is still comparatively smooth, but if you want to get inside where the ripples are almost non existent you have to go for a Delta. Just remember the Deltas are great for this environment but that's all and adjust your style and expectations to suit the fin.

Windxtasy
WA, 3939 posts
15 May 2014 10:42AM
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Dare I ask? What is horizontal lift?

sausage
QLD, 4870 posts
15 May 2014 12:52PM
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Windxtasy said...
Dare I ask? What is horizontal lift?


Anita,
The sideways force your fin exhibits i.e. the force that's created to stop the board sliding out from under your feet. Don't quote me but horizontal lift is the dominant force a fin produces in comparison to vertical lift affecting the pitch of the board along its long axis (fin pushing the nose down).

A fin will spin out (cavitation is a completely different thing and usually happens at faster speeds) when the speed and therefore drive forward created through the mast track is reduced (think of going through a lull in the wind) and the fin's ability to produce enough horizontal (sideways) force is reduced thereby reaching a point were your body weight etc transferred through the board in the opposite direction to the lift is greater creating the fin to spin out.
Well that's my take on it in layman's terms.

I reckon Slowie could give you a much better explanation although you may need to set aside 3 hours and bring a slide rule

decrepit
WA, 11079 posts
15 May 2014 6:48PM
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Yep, Anita, Sausage has it down pat. The confusion arises from the technical meaning of "lift". I'm not sure of the exact definition, but basically it's the force created by flow (air or water for example) over a foil. In the case of aircraft wings, (where I guess the term originated) the force is vertical, but if you rotate the wing through 90deg (like a fin) the force is then horizontal. An upright fin with lots of flex will no longer be vertical over all it's length, this non vertical component, will produce a certain amount of vertical lift. In the case of raked back fins, this vertical lift is negative and just amounts to drag.

fangman
WA, 1074 posts
15 May 2014 7:31PM
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So Decrep is it a reasonable extrapolation to say that the low lift/ high drag inherent in the delta wing design is offset somewhat by the very little flexing causing turbulence and therefore drag? And second, slightly off topic, how shallow does it have to be before you start to noticeably ride on top off your own pressure wave- that is the pressure wave your board produces being reflected back off the sea/ estuary floor? And is this hydraulic ground effect a good or bad thing when you are going fast? I suppose I am wondering whether the negatives of Deltas are offset by a number of other less obvious positives(apart from the really smooth water in the shallows )?

sausage
QLD, 4870 posts
15 May 2014 9:39PM
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Fang,
There was a big discussion on here years ago relating to ground effect I.e. speed Kiters having an advantage over us due to the much shallower water they could kite in. I will try to find and post link.

fangman
WA, 1074 posts
15 May 2014 8:25PM
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Thanks Snags, it's good having all you really old blokes around so that young fellas like me can benefit from your experience and memories. Thanks mate :-)

decrepit
WA, 11079 posts
15 May 2014 8:44PM
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yep, ground effect is positive once you are planning, negative before you plane, as somebody once told me, "you can really feel the extra drag paddling a ski when you hit shallow water."
In the shallow water, your displacement has a restricted path so the bow wave is bigger, and climbing over the back of it is harder. But once planing you're surfing down the front of it.
I think the high drag of the deltas is offset by being in shallow water, it's a similar effect, the much closer bottom makes it harder for the flow from high to low pressure side of the fin. this reduced the tip vortex drag associated with a very low aspect ratio highly raked fin.
The absence of flexing is only an advantage over bad weedys, good weedys don't flex.

I certainly feel a speed boost sailing into dead flat water, but maybe that's just because I'm no good in chop.

Snags I remember that, from memory there's a formula that relates hull width and depth to the amount of extra boost.

decrepit
WA, 11079 posts
15 May 2014 8:56PM
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This is what wikipedia says about aircraft in ground effect.

Principle of ground effect

When an aircraft is flying at an altitude that is approximately at or below the same distance as the aircraft's wingspan or helicopter's rotor diameter, there is, depending on airfoil and aircraft design, an often noticeable ground effect. This is caused primarily by the ground interrupting the wingtip vortices and downwash behind the wing. When a wing is flown very close to the ground, wingtip vortices are unable to form effectively due to the obstruction of the ground. The result is lower induced drag, which increases the speed and lift of the aircraft.[3][4]


So that's saying it stops tip vortices's, not increasing up thrust due to pressure "bounce back" but I guess that's a bit different to a planning hull on water.

sausage
QLD, 4870 posts
15 May 2014 10:57PM
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fangman said...
Thanks Snags, it's good having all you really old blokes around so that young fellas like me can benefit from your experience and memories. Thanks mate :-)

I thought it was the young blokes who had the better memories to remind the old folks

Here's some links but I can't seem to find the 'BIG' discussion. Maybe it was on GPSSS??

www.seabreeze.com.au/forums/Windsurfing/Gps/Water-depth/
www.seabreeze.com.au/forums/Windsurfing/Gps/Three-elements-of-speed/
www.seabreeze.com.au/forums/Windsurfing/Gps/water-depth-rule/

fangman
WA, 1074 posts
15 May 2014 9:00PM
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Thank you guys. I have an evenings reading ahead of me now.:-)

keef
NSW, 1994 posts
16 May 2014 12:05AM
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tobyr
WA, 68 posts
15 May 2014 11:50PM
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Thanks Anita for asking was thinking the same thing.

This is all very interesting as I have never fully understood what is going on with the fin and how the gear set up impacts the performance of the fin be it pointer or weedy.
So sailing with a pointer,moving the mast back in the track allows the nose of the board to rise more and does this let the fins vertical lift become more apparent and the opposite true if you move it forward or is that effect created by the balance point(centre of gravity) of the board?

Mike, thanks for the reply, its got me thinking about the set up of my gear and hopefully I learn something from this.

Brian, had a chat with Chris the other day at the river he is a wealth of valuable info, am going to hit him up more often.

seanhogan
QLD, 3396 posts
16 May 2014 8:47AM
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why would someone red thumb Saucisse's post ?

I would've cause after reading it twice I still don't understand it !! really should've listened in school ..

sausage
QLD, 4870 posts
16 May 2014 10:16AM
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seanhogan said...
why would someone red thumb Saucisse's post ?

I would've cause after reading it twice I still don't understand it !! really should've listened in school ..


Sean,
That'll probably be my Seabreeze fan(s) That or my explanation is gobblygook.

A good analogy to explain fin lift is putting your hand out of a car window. At rest or very slow speeds you can rotate your hand perpendicular to direction of travel & there is very little resistance (or lift). Start speeding up and the angle (AOA - Angle of Attack) your hand needs to be at to produce the same amount of lift becomes more acute. So when pointing hard but slower up wind the fins AoA is greater to that when going broad but the lift (force) may be the same. The beauty about going broad though is the drag is significantly decreased affording greater speeds. I think that's why a badly designed fin / unsuitable fin spins out when quickly bearing off as the AoA is dramatically altered and the fin cannot cope with the quick change in direction and reduction in force (lift).

Someone please correct me if I have this completely wrong.

PS - Fang, apologies for hijacking this thread.

fangman
WA, 1074 posts
16 May 2014 11:46AM
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Hey no worries Snags, I am learning stuff here! I went and looked at the threads you posted last night and apart from all the politics, it gave rise to a few moments when what I had felt through my feet sailing in really shallow water matched with the theory. When I run over the patch that is less than say a foot deep the board feels 'harder' and seems to lift up and then change gears and really let go. I had put it down to the smoothness of the water(which I reckon is still the major part of it - e.g. Lilacs), but obviously there is more to it than that.I think it colours my thinking a little about what path I take across the flats here. So hijack away people, because for someone like me its not all old hat and more interesting than reading about the federal budget :-)

fangman
WA, 1074 posts
16 May 2014 12:22PM
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hey Toby just a couple of tempter photos. I took these at Fangy's at 15knots late afternoon, the weed bank is almost gone, but you can still see the distinctive glassy slicks. If you zoom in you might be able to pick out the crabbers- they are in below knee deep water out on the outer weed bank. Snags, Hijacking my own thread now!







sausage
QLD, 4870 posts
16 May 2014 2:40PM
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fangman said...
hey Toby just a couple of tempter photos. I took these at Fangy's at 15knots late afternoon, the weed bank is almost gone, but you can still see the distinctive glassy slicks. If you zoom in you might be able to pick out the crabbers- they are I'm below knee deep water out on the outer weed bank. Snags, Hijacking my own thread now!



Ooh Fangy's looks like a great place to sail although I don't think I own a fin that could be used there.

This thread has it all. Talking about hi-jacking what's your conspiracy theory on 9/11?

fangman
WA, 1074 posts
16 May 2014 1:56PM
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Snags I think when you hijack a 911 it's called a carjacking....
I think I might be going for a PB here on how far I get this thread off topic:-)

decrepit
WA, 11079 posts
16 May 2014 7:05PM
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seanhogan said...
why would someone red thumb Saucisse's post ?

>>>


There certainly are some very strange red thumbers on this forum, personally I think the site would be better off without the red thumbs. They are meaningless, if you disagree with something, state what and why, we all may learn something.

decrepit
WA, 11079 posts
16 May 2014 7:09PM
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sausage said...
>>> The beauty about going broad though is the drag is significantly decreased affording greater speeds. I think that's why a badly designed fin / unsuitable fin spins out when quickly bearing off as the AoA is dramatically altered and the fin cannot cope with the quick change in direction and reduction in force (lift).

Someone please correct me if I have this completely wrong.

>>>>>


Doesn't sound quite right snags, but I can't put my finger on why not.

fangman
WA, 1074 posts
16 May 2014 7:21PM
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decrepit said...

seanhogan said...
why would someone red thumb Saucisse's post ?

>>>



There certainly are some very strange red thumbers on this forum, personally I think the site would be better off without the red thumbs. They are meaningless, if you disagree with something, state what and why, we all may learn something.


+1 from me too!! Mind you I am such a colour blind noob that I didnt even notice the red/ green thumbs - they all look the same to me

sausage
QLD, 4870 posts
16 May 2014 9:39PM
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decrepit said...
seanhogan said...
why would someone red thumb Saucisse's post ?

>>>


There certainly are some very strange red thumbers on this forum, personally I think the site would be better off without the red thumbs. They are meaningless, if you disagree with something, state what and why, we all may learn something.

No worries decrepit. I know I'm pretty good at rubbing people up the wrong way. Hell just ask my wife

sausage
QLD, 4870 posts
16 May 2014 9:49PM
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decrepit said...
sausage said...
>>> The beauty about going broad though is the drag is significantly decreased affording greater speeds. I think that's why a badly designed fin / unsuitable fin spins out when quickly bearing off as the AoA is dramatically altered and the fin cannot cope with the quick change in direction and reduction in force (lift).

Someone please correct me if I have this completely wrong.

>>>>>


Doesn't sound quite right snags, but I can't put my finger on why not.


Mike,
Isn't a great fin able to handle the quick changes in pressure i.e. when loading it up and down in the chop or bearing off sharply. Sailing in the ocean I quickly find out if a fin is worth keeping as I never sail in a straight line but weave in and out loading the fin very hard at times it amazes me that they don't just snap off.

decrepit
WA, 11079 posts
16 May 2014 8:23PM
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Why a fin lets go when it's suddenly loaded up is fairly obvious. Why it lets go when unloaded is a bit of a mystery, it could be due to the leading edge being too fat.
I've had a similar thing with wave fins as I first take off and drop down the face. Absolutely no fin pressure, but you can just feel it let go. You know if you try to bottom turn, you'll just go sideways, but a slight upwind turn reestablishes the flow and you can get back into the wave, (if it hasn't got too far ahead). I solved this problem by sanding off the blunt leading edge making it sharper.

I think what I'm not sure about is the reduction in lift being the fin's problem. I think it's more the change in angle of attack itself, a blunt leading edge can handle a large angle of attack, (that's why I had originally shaped my wave fins that way), but flow coming from directly ahead has to separate rapidly in both directions, I think this can produce a large separation bubble just back from the leading edge, but that's all theory as far as I'm concerned. Next time you get a fin letting go when you rapidly bear off, try thinning the leading edge a bit and see what happens.

decrepit
WA, 11079 posts
17 May 2014 8:26PM
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Had a rethink about weedys and vertical lift.
What I should have said, is weedys don't produce vertical lift when the board is trimmed flat. If you raise the windward rail, then an element of vertical lift is produced by both the fin and wind under the board.



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"Delta & MUFins order" started by fangman