wobbly rudder leading edge stops stalling

[dylanwinter]

I sometimes stray across to Bob Perry's blog

is latest is about putting bumby wobbles onto the front edge of a ruddder to stop it stalling

just like the bobbly bits on the front of a whale fin

http://perryboat.sail2live.com/

now, I was thinking the other day that I need about another microknot out of the slug

I have a hammer and a hacksaw

how many do you reck9on I need on the slug

Dylan

 

[Seajet]

Dylan,

this sounds very like the trick in the aircraft flight testing trade known as 'vortex generators'...

On things like Hawks & Harriers, little miniature tailfins about 1/2 an inch tall were araldited to the upper wing surface, the idea being to keep the 'boundary layer' of airflow from separating - stalling.

My dad and I tried VG's on his Centaur rudder to get over the lack of feel to the tiller, but we couldn't overcome the skeg induced blanketting & subsequent stall.

A pic of development Sea Harrier FRS1 XZ440, vortex generators visible just aft of the leading edge of the wing; - the 2 items right at the leading edges are 'fences', to prevent airflow going laterally off the wingtip reducing useful lift.

 

[ianat182]

Fitting an end plate to the rudder tip,it doesn't have to be large,will do the same job.

You may as well opt for the full set of foils as per 'HYDROPTERE'or the International Moth dinghies these days but suspect your 'lift' speed will need to be in the 12 knot region!!

 

[Lady Campanula]

Dylan,

this sounds very like the trick in the aircraft flight testing trade known as 'vortex generators'...

A pic of development Sea Harrier FRS1 XZ440, vortex generators visible just aft of the leading edge of the wing; - the 2 items right at the leading edges are 'fences', to prevent airflow going laterally off the wingtip reducing useful lift.

I had the impression that the 'whole kit 'n caboodle' airframe was a vortex generator. As one of the primary effects of vortices is Induced Drag, and big hairyplanes produce big vortices, it could be said that 'in aerodynamic terms, small is beautiful'.

As for the development Seafix Harrier shown, surely those 'sticky-up' bits on top of the wing are the heads of the hexagonal bolts used to fasten on the curvy front edge? Or are they spare bits left over from the Buccaneer programme?

It is naval aviation after all - 'what's below the waterline doesn't show; what's above doesn't matter...'

 

[Lakesailor]

Have you had occasions when the slug stalls the rudder and rounds up?
I would have thought it was worth keeping it like that to maintain the frisson of uncertainty and thrill the occurrence gives.
I eliminated stalling on my Seahawk by fitting a tall vertical blade instead of the round, shovel-like thing that is standard fayre.
I can't help but think the bumps will slow you down. In fact they may lead to the slug sailing backwards.

 

[dylanwinter]

stalling slug

Have you had occasions when the slug stalls the rudder and rounds up?
I would have thought it was worth keeping it like that to maintain the frisson of uncertainty and thrill the occurrence gives.
I eliminated stalling on my Seahawk by fitting a tall vertical blade instead of the round, shovel-like thing that is standard fayre.
I can't help but think the bumps will slow you down. In fact they may lead to the slug sailing backwards.

slug has never stalled out on me

not sure it would

triple keel - bulbous bilges - not much sail area

sailing backwards

slug is often sailed backwards off the mud

great fun

Dylan

 

[Fire99]

I'm no expert but i'd guess it's a bit more complicated than just 'lobbing on some wobbley bits'

On something like the slug (and my boat) my priority would be for a very fine rudder with limited drag. Those keels are a bit 'heavyweight'

That said, my boat is out the water (due to a near submarine issue) so it's all theory with me for now

 

[Seajet]

End plates work like fences, keeping flow over the foil.

Lady C, no need to take the P out of the FAA, the Sea Harrier did rather well ( yes with some RAF pilots just to show them how it should be done ) !

I could mention a couple of sorties where the jet came back without stores - or pylons - but they were never through-bolted, that would be more likely on a whippet botherers product.

 

[electrosys]

I am beginning to have visions of Dylan hanging out over the weather rail on a trapeze - with one eye glued to the knot meter as the slug skims effortlessly across the water on it's gleaming new hydrofoils ....

 

[DownWest]

I am beginning to have visions of Dylan hanging out over the weather rail on a trapeze - with one eye glued to the knot meter as the slug skims effortlessly across the water on it's gleaming new hydrofoils ....

Do you get any other equally weird visions? Voices in the head?, or bumps? Better see a phrenologist................