Fin Division of CBC , next generation

[U2U2U2]

Thanks for your interest. Has anyone performed a scientific study on windsurf fins that have a wing installed at a position other than the tip, no, not that I know of.

I have never felt that fins, have a direct relationship with wings, oh they both do provide lift and offer stability, surely some of the forces are similar.

By placing my wing not on the tip, to me is similar to different aircraft tail designs, some have the horizontal stabilizer at the top of the tail, some split the tail, some lower even.

My hypothesis , initially was I had a spare piece of fin, it looked like a wing
And I installed it. Different people looked at it and all had opinions if it would improve anything, including , it will work fine till you turn.

So from a AIRCRAFT POV, winglets capture some of the vortex energy and turn it into thrust by redirecting the spanwise flow rearward, this increase in gross thrust for the wingtip works out to be a degrease in net drag.
To further:
Winglets that point down as well, capture the vortex while going around the tip, and are installed with toe in.

When aircraft started getting longer wings, they found...duh...they no longer fit into the gate area, they overlapped into the next gate, winglets allowed or-developed then to increase wingspan area without length.

[konajoe]

Basic drawing: http://westessex.proboards.com/thread/45/wingtips-good-tutorial

You'll have trouble beating laws of hydro and aero dynamics. The tip vortex deal is well documented. That's why you'll always see the winglets at the tips. So the reason that you haven't seen a winglet mid-foil is that it has already been shown not to work. (The tail rudder on an airplane isn't there to generate lift.)

Since you have some fin surface below the wing, it sets up high and low pressure zones. So, you still have a tip vortex. You end up with extra drag from the wing and winglets without any benefits, because you'll still have tip drag.

I think you're talking NET thrust, or thrust minus drag. Wings and foils don't produce thrust. Just lift and drag. So if an engine or sail generates a certain amount of 'thrust', and you reduce the drag by putting winglets on the very end of a wing or fin, then you increase the available thrust. I guess that's a different way of putting it.

[U2U2U2]

The tail rudder is a moveable part within the tail.

Some aircraft , Beachcraft Starship,for one don't have a tail , so can't even have a rudder.

More than one way to bake a cake

You can't make a racehorse from a pig
But
You can make a fast pig

[grantmac017]

Assuming this isn't entirely a joke:

What you've got there is a trim tab or a wing fence depending on how you look at it. The trim tab could in fact be assisting with tail lift so as to promote earlier planing however you have gained a significant amount of intersection drag as a result which will increase dramatically with speed.
A wing fence prevents spanwise flow which assists with lift at higher angles of attack. Not really a regime that a board fin spends much time in.

A winglet will be at the end of the wing and reduces drag but doesn't really add lift. However if set at an angle like #1 may perform the trim tab function with a lot less drag due to no intersection and also reduction of tip vortices.

Is the goal more attached flow at high AOA, reduced drag or increased tail lift?

[U2U2U2]

Much like the poster mentioned before using rudder, a trim tab is a moveable section,rather than use the horizontal flap in its entirety it's a section , so trim can be fine tuned. Rather a mini flap.

A wing fence is placed along the wing , size varies, number as well, they are not a form of winglet. They are not normally designed into the wing at conception, they have drag.

GOAL: to increase the fin area , without making the fin longer. We could discuss how winglets help reduce drag the drag associated with lift, and the higher angle of attack creates greater lift..

Of course the parasitic drag is part of the equation as well.

[konajoe]

[U2U2U2]

[U2U2U2]

it's something like 8 yo, from Calif, a surf company.

Pocket Wave 85.
Leading edge is similar to a whale fin, the surface is not smooth , it's rough like a sharks skin. Going from memory it's 22cm long , but has a broad base.
A fin company from Quebec, is selling a fin, it's similar but has groves along both sides where the bumps indentations are.

[grantmac017]

A trim tab can be fixed or movable. In this case (assuming it's effect isn't psychological) the most I could see it doing to slightly lifting the tail of the board which might reduce drag in a near-planing condition.

Winglets do not increase thrust, they can reduce drag though. They likewise cannot increase lift unless they allow the wing to fly at a greater angle of attack without greatly increasing drag.

The wingtips I have on my plane are of the "Horner" design which reduces drag at higher angles of attack by preventing vortices formation and directing the vortices downward. You'd think they would allow the plane to fly slower (they do, just not much), but in fact they allow faster cruise and better glide at higher weights.

I've often looked at fins and thought about how inefficient their tips are compared to even a flat plate. I'd love to see some drag data on that.

[U2U2U2]

Wing tips on commerical of large general aviation jets are expensive.
The return is better climb rate, reduced drag, translate into fuel cost savings.

They capture the wingtip vortices and increase lift, the reference to increase thrust I would have read somewhere, the plane itself would require less thrust to perform the same.

To me in smaller aircraft the benefit is a shorter takeoff, it would increase cruising speed some, should be better fuel economy.

Going to my fin, the wing I'm sure increases lift, the same way I know if a 22cm length fin, needs to be larger, I can feel it.

Does it create a higher speed, even with a GPS, to duplicate conditions is near impossible, so I can't say, could it induce more drag, yes it could, since I can tell if a weed is on a fin, I could probably tell if it's slowing me down.
If the wing on my fin create enough vortices to gain any benefit from the wing tips , would need to be tested with and without, this is probably so small to be imperceptible. Some difference on the fin itself might show better results.
On a wind sup, a more raked race weed fin , could produce better results, esp since faster turns aren't so possible anyway, meaning mine ain't that fast .

This is a project I made in a shed, it was neat to do.

The board below with the tunnels between the fin clusters is my creation.
People who saw this prior to riding, said it would create all Nasty manner of flow, disrupt the fin intention, cause cavitation, loud noise, make the board awkward to ride, abrupt turns, everything but cause cavities in teeth.

My mates and I decided that should any bad character appear , I would tape over the tunnels, and ride it again. Tape was not needed. It is one of the most wonderful boards I have been on, it doesn't feel like a quad, no drag . It's turning is hampered some but the rail shape is Freeride .
This started live as a Naish 109l 1999 Titan, shortened at both ends, totally morphed in a 2017 board.