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Vibration at low speeds

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haare
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Vibration at low speeds

Postby haare » Fri Jul 14, 2017 7:41 pm

Hi,

I bought used MHL lift carbon hydrofoil 2015 edition. It looks to be in pretty good condition.

When I foiled it for the first time it has this weird low herz vibration in low speeds. It is very noticeable when I make turns. Once I have some speed it goes away or I don't notice it anymore.

I think it is not normal but has someone else experienced similar. The foil is completely silent even in high speeds downwind. I checked the scews after the session and they were all tight.

Is it just that my foil has some flex that makes it to vibrate. Could trailing edge sanding help?

plummet
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Re: Vibration at low speeds

Postby plummet » Fri Jul 14, 2017 10:17 pm

Is everything tight?

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Peter_Frank
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Re: Vibration at low speeds

Postby Peter_Frank » Fri Jul 14, 2017 10:28 pm

Hi haare - this is very normal and not an error.

Just found the lift from 2015 and quite low AR.

Which means, at low speeds it will make a soft stall, giving you a warning as a vibration, which is really cool, as then you know you are on the verge to stalling, but havent stalled yet.

It is how low AR wings works, and great :thumb:

Higher AR wings (more span and less average chord) works just the opposite, they work well to a certain point, but then they stall without any warning....

Hope this explains - dont worry, your wing is spot on and works just as desired - be happy you got this warning you are on the verge of riding too slow :rollgrin:

8) PF

haare
Rare Poster
Posts: 39
Joined: Tue May 03, 2016 2:57 pm
Kiting since: 2015
Local Beach: Lahti, Finland
Favorite Beaches: Egypt - Marsa Alam
Style: snowskite, freestyle
Gear: Pansh A15 12m
FS Speed 3 15m
FS Speed 15m
FS Split L
Liquid force foil Fish
Brand Affiliation: None

Re: Vibration at low speeds

Postby haare » Sat Jul 15, 2017 4:54 am

Thanks Peter, My first foils have not vibrated that made me wonder. It works exactly like you said. When it vibrates it is close to stalling speed but I can still stay up. This is really not anything that would be annoying. I was just worried is something going to break if I take it to higher speeds.

About the foil. It is really weird. I can foil with this almost walking speed. Still high speed is about the same that it was with my previous medium aspect wing (RLboards freestyle).

I think it might be because the front wing has more surface area (more lift) but is thinner so less drag (able to go higher speed).

I definitely need to get used to almost +20cm more mast length (previous 90 now including front wing about 110):D. Makes turns little harder now (less responsive) but it is just something to get used to. But you can go upwind in crazy angels when gust hits.


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