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Benefits of retrofitting lifting strakes or "spray rails" to multihull


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Is there any research on benefits of retrofitting "lifting strakes", like those found on motorized pontoons, to sailing multihulls in order to prevent pitch-poling, and giving extra lift when in strong winds on the leeward hull?

 

 

2020-05-11 10_21_08-lifting strakes - Google Search.png

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6 hours ago, martin 'hoff said:

That flap will pretty much guarantee a pitchpole, once it "bites". Look at the inverted bows of modern fast foiling cats and F18s and such. 

Certainly a flap with such a large leading edge. Inverted bows are used to maximise reserve buoyancy low down whilst minimising weight pitching and windage above. It is a calculated performance risk.

if the highlighted rail was faired into the stem piece, and was solid filled and faired to deck level, with maybe a rounded top edge to help shed water, then you would have dynamic lift as well as additional bow buoyancy to maximise lift and minimise burying.

If you bury the deck, either way, you are headed for trouble.

Apologies for the crude mark up.

E9FDBE99-C31E-45E8-BA2E-1D09EB70EF21.jpeg

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13 hours ago, Will22 said:

Is there any research on benefits of retrofitting "lifting strakes", like those found on motorized pontoons, to sailing multihulls in order to prevent pitch-poling, and giving extra lift when in strong winds on the leeward hull?

Some say yes (recommend turning down the volume).

Some of the same people later say no.

Then again needle-nosed, highly-rockered H16s can be tough NOT to pitchpole in sport conditions.

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14 hours ago, Will22 said:

Is there any research on benefits of retrofitting "lifting strakes", like those found on motorized pontoons, to sailing multihulls in order to prevent pitch-poling, and giving extra lift when in strong winds on the leeward hull?

 

Yes there can be benefits with spray rails they can give a tiny bit of extra lift forward along with reducing spray making the ride drier for the crew. I doubt it would prevent nose diving which is really the rig accelerating faster than the hull.

Raw To The Core had small spray rails forward, I wouldn't do it on anything small but could be worthwhile for larger boats.

 

 

raw to core.jpg

rtc 2.jpg

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I'd say small ones as spray rails won't hurt and will keep the boat drier.

But as anti-pitch pole devices, nope. Better to have fuller bows (reasonable hull flare) or a bow that sheds water when immersed if you're going to immerse it (reverse bows)

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18 hours ago, Mohammed Bin Lyin said:

Yes there can be benefits with spray rails they can give a tiny bit of extra lift forward along with reducing spray making the ride drier for the crew. I doubt it would prevent nose diving which is really the rig accelerating faster than the hull.

Raw To The Core had small spray rails forward, I wouldn't do it on anything small but could be worthwhile for larger boats.

 

 

raw to core.jpg

rtc 2.jpg

I think " Raw to the Cores" were more of a spray deflector to make life a little more bearable for the crew ?

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8 hours ago, basildog said:

G'day Sidecar,

Any chance of more pctures of that very cool looking Proa?

 

If you go to my profile page, there are some photos and basic details on the boat in the “About Me” section. If you want anything else specific, Please PM me.

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When I look at the " lifting strakes " you envision, as previously mentioned, after a certain amount of bow-down I am reminded of the commands in a submarine  " Dive, Dive- Dive " Maybe just don't push the boat so hard. The boat will tell you when enough is enough. Just listen. Happy Sailing!

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Fun to watch: at around 2.20 you can see the shape of the hulls, long narrow and deep for directional stability, (buoyant) spray rails for lift and extended aft foils for trim.....

 

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