It's a Hallucination

are you using a select fin?

some of these are notorious for screaming like a banshee

Could also be whistling from the holes in the boom extension

is your boom a single pin, because one of our booms with a single pin whilstes but only in strong winds. and when your really hard up wind or going down wind

Usually get a whistle when gybing on the inside but it's from the girls on the beach, but seriously, my old pride extension used to whistle as the apparent wind changes direction.

I've had whistling from my mast extension, and a friend has one of those F2 boards with the air holes in the deck, which I think were whistling once when he passed me like a rocket...

Don't worry about it; it makes you sound faster!

Wet Willy said...

I've had whistling from my mast extension, and a friend has one of those F2 boards with the air holes in the deck, which I think were whistling once when he passed me like a rocket...

Don't worry about it; it makes you sound faster!

yup willy i thought i was going like finian and thru the liquid barrier but sadly not on this one only as you said ' makes you sound faster'

Select fins hey elmo,
I just changed from a drake 40 to select 38 and you can hear me coming a mile away, I thought I must of been rigging something different but its probably the the fin like you say, how can a whistle come from a fin anyway its underwater????

wormy said...

how can a whistle come from a fin anyway its underwater????

It's to do with vibration in the fin due to unbalanced loading, and usually turbulence of some kind - the fin gets loaded up one way, then the modulus of elasticity in the fin overcomes the load, and flicks it back the other way, where it loads up and flicks back again.. all very very small deflections, very fast. This causes a high frequency vibration, some of which is transmitted through the fin box and into the board which then acts somewhat like a guitar body. If you're (un)lucky you can find the harmonic frequency of your board.

We get a similar effect with composite glider wings - shortly after they start really screaming, they explode!

So, technically, the whistle you hear comes via the board, but it's usually caused by the fin!

I'm guessing it's the rig in this case though, as sheeting in to windward tends to load up the fin, and assuming you still have some speed on, should make any fin hum worse, not better (unless it's moved outside the frequency range that your board is able to sing!).

My HPL boom has some closed cell foam in the extension arms, so that the 'spare' holes aren't really open - you could try that.

I also had a Pryde sail that would whistle on a particular point of sail- it turned out to be the luff sleeve vibrating behind the cut out as the air hit it straight on. Like using a piece of grass to whistle..

Crash , Thats actually the opposite of what you want to do to stop a fin whistling . It whistles if the trailing edge is too fat . What you need to do is get some 400-600 wet and dry sand paper on a block . Run it down the trailing edge at about a 45 deg angle . Bring it almost to a point ( but no need to make it razor sharp , bad for feet when water starting)
This should solve any whistling .

I'm not concerned about the whistling... its the sonic booms!

wormy said...

Select fins hey elmo,
I just changed from a drake 40 to select 38 and you can hear me coming a mile away, I thought I must of been rigging something different but its probably the the fin like you say, how can a whistle come from a fin anyway its underwater????

It's not all of them Mainly the pointers I believe and you can hear them from quite a distance away.

I suppose it has the benifit of saving your voice from shouting "get outa my way"

i'd like to believe that filthy but when at speed and all that noise the board skimming and wind and all the whistle blows just like it was a foot away..oh i'd let it be if it whistles then cool. here's another what i noticed it only whistles on starboard tack and why not the other sidehere we go again

hey nebs longtime no hear good results your side ey! okay i'll accept that it sure is loud and as i said from a foot away but for your explanation that is simply amazing..i'll try to chamfer but honestly what do you mean by thatoh by the way this fin is a 34 northshore maui and erect for upwind performance..regards

nebbian said...

It's the fin.

My select 37 does this, it goes up in distinct steps, G# means 28 knots, A means 29 knots, Bb means 30 knots, C means 31.5 knots...

Play us a tune then, Nebs!

Can you do "Smoke on the Water"??

Hmmmm... might be able to do "Mary had a little lamb"... would have to be the right conditions though, and getting the sound to stop then start at the one pitch would be tricky. Chop hopping does work, I've done it before, the sound seems to gets louder just as the fin starts to leave the water for some reason then stops when in the air.

Where's my waterproof sound recorder gone?