Neil pryde mast humming

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Created by

Youngbreezy > 9 months ago, 24 Sep 2020

Youngbreezy

1221 posts

24 Sep 2020 8:30pm

I have a bit of an annoying and loud zing on my neil pryde glide setup.

I have had the foil setup for a while and it has always had a bit of a zing but it only used to kick in at quite high speed. I had to replace my mast after I got caught inside on a solid day and bent the mast and base plate. The old mast was an 80cm chopped to 75cm and the new mast is the same but is a newer model and has some subtle differences.

With the new mast the zing kicks in at a fair bit lower speed and has become particularly annoying when I am kite foiling. I am sure it's the mast as the wings haven't changed.

I have seen Colas's posts about the Donaldson trailing edge and it was quite interesting, thanks Colas.

I am wondering if the Donaldson trailing edge would be effective on the mast as it is supposed to be used on the underside of a wing/foil whereas the mast is just a normal curved shape.
Which side would I sand the Donaldson trailing edge curve into? Would that give the mast an uneven feel with an asymmetric trailing edge?

Interested to hear your thoughts.

Bertie

NSW

1351 posts

25 Sep 2020 10:50am

In franks book it makes it clear how to attack this.
www.amazon.com/High-Performance-Sailing-Frank-Bethwaite/dp/0070057990

easiest way is to just sand the trailing edge to a sharp square up to 2mm thick. if it still humms then sand a 45 on one of the trailing edge corners. never round the trailing edge. its the vortex shedding that creates the humm.

you wont notice such a small asymmetrical change on performance except the handbrake will come off when the humm is prevented.

colas

5370 posts

25 Sep 2020 1:29pm

Just sand asymmetrically the mast, just as I do on center fins.

If you looked at my post, you can see in the video Mario Legenstein sanding the mast asymmetrically at 6:55

Making the trailing edge into a sharp square is not a reliable solution, as for it to work the edge width must be the exact size of the vortexes to anchor them, and it depends on the water speed. You are creating two anchoring points for the vortexes, exactly what you want to avoid!

Youngbreezy

1221 posts

25 Sep 2020 2:24pm

Ok cool I think I will just try sanding one side, being sure not to create too sharp of a blade.

Thanks for the help guys

Piros

QLD

7251 posts

25 Sep 2020 7:50pm

Np have a really good anodising if you heavily sand that trailing edge you'll expose the the Ali , just painting won't work to re seal . Maybe try 600 grit wet n dry first . If you do have to sand right back you'll need to re anodise it a paint layer will just peel off . It's an extruded alloy and doubt it has a fault . Unless you can see a physical deformation on the mast , I'd look at your trailing edges on the wings first before you attack the mast . IMHO .

hilly

7979 posts

25 Sep 2020 6:53pm

Select to expand quote

Piros said.. I'd look at your trailing edges on the wings first before you attack the mast . IMHO .

+1 or stab

colas

5370 posts

25 Sep 2020 9:04pm

Select to expand quote

Piros said..
Np have a really good anodising if you heavily sand that trailing edge you'll expose the the Ali , just painting won't work to re seal

You do not need to protect aluminum. It oxidizes so fast that it instantly covers itself with an aluminum oxide layer, which is waterproof, and stops instantly the oxidation. It is actually impossible to expose it.

www.cabuk1.co.uk/FAQ%207%20Oxidation%20of%20aluminium.pdf :

Select to expand quote

Oxidation of aluminium

Aluminium oxidises very readily but this is advantageous as the aluminium oxide is tougher than the aluminium metal as so the oxide protects the metal. The aluminium oxide is also less dense than the metal and so takes up more space than the metal and so as the metal is oxidised it puts the aluminium oxide in compression and this helps provide the surface with a good barrier layer that reduces the rate of any further oxidation.

Thus the first monolayer of oxidation is virtually instantaneous dependent only on the arrival rate of oxygen. Beyond this the oxidation rate is dependent upon both the oxygen arrival rate and the rate of diffusion through the existing oxide layer. Typically the oxide could be expected to be 1.5nm - 2nm almost immediately and 2nm - 4.5nm in anywhere from 1 month to 1 year dependent upon conditions.

In most metallizers the residual gas within the vacuum system, even where the system can reach a good base pressure, means that the rate of arrival of oxygen to any surface is faster than 1 monolayer per second. Hence there is always plenty of oxygen available to oxidise the aluminium surface even in a vacuum system. It is also worth bearing in mind that even at the high aluminium deposition rates available in modern aluminium metallizers it is still common for there to be 1% - 2% oxygen contained within the coatings.

Where oxygen is not available as a gas the aluminium is happy to strip the oxygen out of water molecules and as water is the dominant background gas of all vacuum systems there is no shortage of oxygen for oxidation to occur.

Piros

QLD

7251 posts

26 Sep 2020 9:18am

Well talking from first hand experience from so many chop shop on Ali fuselages and mast , the bare aluminium will pit from corrosion after one of two sessions if left unprotected or at least polished after every use. Any pitting or corrosion on the trailing edge will be far worst than what you have now .

Youngbreezy

1221 posts

26 Sep 2020 9:43am

Yeah I was concerned about hacking into the anodizing and increasing the corrosion.

I will definitely have a good look at the trailing edges on the wings as they are far from new and could do with some smoothing out. It was just that when I put the new mast on I noticed the significant increase in the zinging.

I had also been wondering about repainting the Ali as I have some corrosion on the fuse from leaving the wings attached too long. I had googled it and the process I had come up with was to sand the Ali then coat it with something called "self etching primer" which I think bonds into all the tiny grooves created by sanding. You can then paint over it and the paint bonds to the primer not the Ali.

Does anyone have any ideas about this?

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