Hull Surfaces: A Scientific Approach

I work with scientists around the world getting their research published. Most of the work is in unrelated nano world. I did get a paper albeit somewhat simplistic on the replication of sharkskin using 3-D printers. It showed about a 8-9% reduction in drag.

Creating a film or surface such as this may be the ticket to faster skis without sacrificing stability.

While I am unable to share the paper I can give info if anybody wants.

Sounds fascinating.

Ha - I found an old thread from 2007 on this:

www.surfski.info/forum/15-tips/249-re-hull-treatments.html

Can you describe what the surface looks like and why it works?

Some articles:

www.usatoday.com/story/news/nation/2014/...om-sharks-/14173033/

www.research.ufl.edu/publications/explore/v10n1/extract6.html

The authors approach is much more complex then the Florida approach. It more resembles shark scales. I will make a drawing and post.

The ICF have banned any hull surface treatments.

There is an article written by Greg Barton re this issue that he tried many years ago with a special hull finish. It can be read on the Epic web site.

I've always wondered about this. Why some things have never been incorporated in surf-skis. I don't really care about race legal or not, simply for recreational purposes. Always more fun going faster.

-Golf ball type dimples on hull surface
-The bulbous underwater bow you see on huge ships
-Maybe a tunnel shape under the hull might make the ski plane if you get enough speed on a run

jagter wrote: -The bulbous underwater bow you see on huge ships

The swedish kayak designer Björn Thomasson has some thoughts on bulbous bows for kayaks here: www.thomassondesign.com/en/news/bulbous-bow-on-kayaks (in short: he doesn't belive in the idea)

-Maybe a tunnel shape under the hull might make the ski plane if you get enough speed on a run

I don't know about tunnels. But hydrofoil kayaks have been built: . I'm not sure how well that might work in waves.

Thanks, very interesting.

Surfski is probably the closest we get to an unlimited class when it comes to paddle sports. Far less rule restrictions on boat design than other disciplines. So I reckon there are still some improvements to come within the existing design restrictions.

Would be interesting to have a totally unlimited racing class though, where anything goes, including hull surface coatings, hydrofoils, etc. I bet some really fast designs would come out of there.

Hi darebet,

I thought about that a while ago an discussed it with local manufacturers. Could we get in direct contact to exchange more information?
Cheers, Ole

I don't know about tunnels. But hydrofoil kayaks have been built: . I'm not sure how well that might work in waves.

10 years ago International Moths could barely foil in a straight line without turning somersaults, but control systems have come a long way since then.
Did development of the flyak ever continue?

More practically perhaps, a number of dinghies use a single rudder hydrofoil successfully. And it also appears to work on boats that are slower than a ski much of the time.

Some new thinking on hull sections too - see the lower half of the text .

Of course whether any of this would work on narrow k1/ski hulls is another matter, but fun to speculate...

darebet wrote: .....

While I am unable to share the paper I can give info if anybody wants.

Hello darebet,

Is this the paper/topic: www.rsc.org/chemistryworld/2014/05/3d-pr...wimming-skin-secrets


Thanks,
Ole

No idea if the foiled kayak got developed further but foiled sailing sure did. These races were epic
Shame money & courtroom battles make the on water competition unfair

Yes, all of these areas incredibly fascinating. I have a strong sense our sport is poised on the edge of making some sort of breakthrough that radically redefines boat shapes and speeds. There has been silence in these areas for too long. Remember when wing paddles first came out? That marked a fairly significant change in the sport. Would LOVE to see some more development here!

Ok, Who's up first for turning their ski into a golf ball textured hull?

They did it to a cars body and it was faster with the same power.

Well I lost a ski on a downwind once and it spent hours being bashed around the rocks. When I recovered it, the gelcoat was comprehensively dimpled, but it sure didn't look as though it would go faster!

www.surfski.info/latest-news/story/1007/...sabotage-a-sale.html

Coast Steve wrote: Ok, Who's up first for turning their ski into a golf ball textured hull?

Yep, but cars and golfballs move through air at fast speeds. Water is incompressible, denser and more viscous...and ski's don't move at much more than running pace most of the time. Mr Reynolds would probably have something to say on the subject.

I have a strong sense our sport is poised on the edge of making some sort of breakthrough that radically redefines boat shapes and speeds.

I'm not so sure, my perception (maybe mistaken) is there is little in the way of real development in ski or flatwater racing, it's all very conservative. There's some incremental stuff - the ways skis appear to be becoming more stable vs their speed potential, but the only tinkering going on locally is a flatwater training boat, which sounds like it is going to be tippy and sink when capsized...not much of a development over present flatwater boats!

I think there's more of a tinkering culture in sailing, as it's less down to fitness and so the technical side looms larger. To a degree paddling will always be limited by the power available from the human body, though there are probably avenues to be explored.

We need to kidnap one of the designers of the older Americas cup hulls.

Actually here's something to ponder:

When I bought my V10 Elite, it had the weave feel on the hull.
They made them with no gelcoat so the boat's really light I guess.

Anyway, the carbon cloth was showing through and I'm only talking a tiny bit. for the most part it was pretty smooth.

I had the boat sanded and then sprayed with sikens car paint
(UV stuff included) then I wetsanded the boat for like one whole day till it was glass smooth.

A few days later I took it out to the lake I usually paddle on and what a difference!
It was noticeably faster but also a little more tippy.


I thought it was my imagination at first but no.

And this may sound weird but it now not only glides better but I think it's quieter in the water when running on the flats.

The biggest thing I noticed though is the boats new tippyness

So.. super flat smooth surface is what I now have.
It's matt looking, not a shinny finish.

I find this thread quite amazing!

Most of the so called developments you are mentioning have already been done and thrown in the skip bin. These failed attempts as you would expect are not published for obvious reasons.

There are many naval engineers that have tried and failed including Americas Cup yacht designers, believe it or not, with high powered software.

The few things that I am aware of which I would think would be a drop in the ocean are: hydroplane ski, bulbous nose hull, yacht plaining hull shape(have one in the shed)... and the list goes on.

As for surface finishes, a company like 3M has a bit of money behind it has made these textured surfaces around 20 years ago and were band for sprinting.

But then again if someone would hand over a few million dollars to a naval design company I am sure they would come up with something. Most people have zero idea of how long something like this takes to develop and test, then they are surprised that they have to pay for the finished product that goes into production. They would rather go and by the rip off design that cost zero to develop and then complain about the expensive skis and why they cost so much.

My two cents worth being involved in ski paddling and deign for the past 30 years.

Ranga, I'm sure you're right many ideas are dead ends, however I really doubt the design space of the present ski rules has been fully explored.

Ranga wrote: Most of the so called developments you are mentioning have already been done and thrown in the skip bin.

The trouble with skip bins, stuff has a habit of coming crawling out further down the line... Development is never a straight road.

It took 20 years for rudder foils to 'work' in National 12s. The first go was in the early '90s where they were intended to stop nosediving downwind and endplate the bottom of the rudder. They proved better at collecting weed and quickly went back in the bin.

Then in the early 2000s a guy developed a rudder with a 'flapped' hydrofoil to create lift. He was ingenious but not a good sailor and his design was a bit crude. So, he didn't go fast and neither did the few top guys he lent it to for the odd race. It was dismissed again, it 'obviously didn't work'.

Enter Jo Richards, 1978 national champion, olympic sailor, Americas Cup designer. He made a return to the 12 class after a 30 year break with a boat he designed and built himself. It had a winged rudder and quite a few other novel ideas. He utterly annihilated the rest of the championship fleet. Now every boat at the front of the fleet has wings...

Those skip bins, they need a lid...

To really know whether an innovation works you need the stars to align: A good idea, finessed over significant time, tested in real-world conditions by people high level skills (and acceptance that new skills may need to be developed to get it to work) and a good slice of luck.

I don't think those conditions exist in ski and flatwater. The guys who came up with the flyak wouldn't have had anywhere to race it as ICF K1 rules preclude that and no 'open' classes exist. Manufacturers are trying to make money so they're going to be risk averse and as competitive kayaking is almost all 'off the shelf', development will unsurprisingly be minimal.

Ranga wrote: These failed attempts as you would expect are not published for obvious reasons.

Why? The high profile failures are well discussed in sailing - reasons for failure often give clues as to how to improve.

Ranga wrote: There are many naval engineers that have tried and failed including Americas Cup yacht designers, believe it or not, with high powered software.

Software is not a panacea. Many of the failures of high profile projects have been down to over-reliance on software and tank-testing. In the America's Cup the real-world measurements being fed back into the software are still key in getting reliable results.

robin.mousley wrote: Well I lost a ski on a downwind once and it spent hours being bashed around the rocks. When I recovered it, the gelcoat was comprehensively dimpled, but it sure didn't look as though it would go faster!

www.surfski.info/latest-news/story/1007/...sabotage-a-sale.html

Many thanks for this! A sad story told well!