Re: Reasons To Be Grumpy thread

[Siz]

Yes, I see it now.
Not sure I understand the mechanics of the quoted functionality of the skeg.

I did just read a more detailed explanation of the stepped hull. Makes sense. But probably creates too much turbulence for use in dinghys where the hull needs to be efficient at every speed.

glen curtis invented a cutoff to the rear of his floatplane pontoons to reduce hydrodynamic drag. he found that he couldn't get the planes into the air. apparently the pilot tipps the plane back and planes on the rear, while lessening the overall contact to reduce hydrodynamic drag.

I think you have that backwards. The float lifts at speed to raise the aft section OUT of the water.

[Siz]

Sciz, would you be deeply offended if I told you I read all your posts in a Yorkshire accent?

ROFL. Would that voice also be female, by any chance...??? 

Anywhere between Daniel Craig and Ricky Gervais (depending on who I'm talking to) would be nearer the mark.

You're all George Peppard to me...

Female? No, but I can make adjustments.

How about we go the whole hog and say I've got a fine bosom, a peachy backside and pouty lips with your name on.
I'm whomever you want me to be, Yorkshire or no...

[Dark Lightning]

:backs slowly out of room:

[Magdalena]

^^^

[Icarus]

That is a definite bummer Siz. Why did you capsize that gorgeous boat?  Activity, not to say panic,  at the mark can sometimes be rather disconcerting, I am well aware. 

Here's hoping that your injury will heal rapidly and painlessly.

Hehe, it's not an unusual occurrence; as a racing dinghy, it's not built for stability. Though I'm quite adept at rightng it and carrying on quite quickly. Just this time my own personal mechanical failure put me out of the race for good.
it was definitely a panic moment. Second race of the day, having lost the first race to my main rival by the narrowest margin. Found myself ahead at the windward mark and got flustered as he pulled a neater tack and was closing fast. Got in a tangle while baring away and resetting and fell over.
There's a narrow window of wind in which I can be competitive. About 16-25kts. Too low and my boat just isn't as fast against others, too high and I just can't cope. This day was toward the 25kts end and I was in my element. Just lost focus and blew it.
Cheers Icarus.

Twenty five knots of breeze is at, or beyond, the upper limit for a fun day of sailing.   Glory be, I might have left my boat on the trailer and retired to the club bar for a few beers.  I have a very long history of competitive sailing and the older I get, I am less and less thrilled with the prospect of a wild planing ride.   Sure enough I can still get my jollies when the boat takes of at a  good speed. 

Your boat is definitely not disqualified from being competitive at lower wind velocities.  It is a beautiful piece of work.   At light to moderate wind strengths, familiarity with the boats ideosyncrasy is a necessity.  Some, actually most, boats need to be sailed heeled to make the best progress.  In fact most of them will have less wetted surface when heeled to some extent.  In  a five or six knot breeze the difference is significant. At low speeds the hull friction is a determineg factor.  Less wet surface = less friction resistence and better speed. .  At those low speeds the dynamic drag from wave making is less a factor.  As speed increases the wave drag becomes the dominant drag factor.   (read the resalt of intensive research of your fellow Brit C.J. Marchaj. His book: Sailing Theory and Practice is invaluable)

In a drifting match it is common practice to crawl onto the forward deck to further decrease the wetted surface.  All that schoolyard physics is useful but it does not compensate for experience.  In light or medium airs the overwhelming need is to be vigilantly aware of where the wind is.  It is not the same on any surface. There are wind streaks and lull streaks.  So learn to find the favored course. Be gentle with sail trim. Ease the vang (kicker), loosen the Cunningham, don't bend the mast with too much downhaul.  If you use woolies or sail ribbons, pay attention to them but not get so fixated that you miss a shift.  Some time back I recommended a book by another of your Brit wizards: Alan Waites.  Get the book, read and absorb his learned wisdom. Finishing second or worse sucks. 

Competitive sailing is the nearest thing to a waterborne chess match. Anticipating your opponents moves and being more aware of the pieces on the board, in this case the locations of better wind strengths,  is the key to superior finishes.

Get well soon and get back out there when the air is not so damned vicious.   

[Siz]

Yes, it's tricky close to 25kts, but that's the way I prefer it. I enjoy most of my sports just on the wrong side of control.

With regard to heeling, the current advice is that one must keep the boat flat. The reason is that heeling creates a turning force on the boat which you have to counter using the rudder. That is the biggest brake on the boat.

One of the exercises in the RYA courses for kids is sailing without a rudder. This is quite daunting at first but given a bit of practice you can sail pretty accurately (albeit with slow response times) by using your body weight to steer through tacks, jibes, everything - opposite direction to a skateboard. A great skill to have, not just to understand the hull dynamics, but an essential skill in emergencies.

My Blaze is known for its heavywind capabilities... and its low wind failings. Its Hull weight is quoted at 72kg. I'm regularly racing again RS Areos (modern Laser equivalent) whose hull weight is quoted at 30kg. Add my 85kg to my hull weight and I just can't compete in the light stuff against a decent youth sailor. Crawling on to the foredeck is a well-used tactic. In fact, I had to buy a telescopic tiller extension to be able to move further forward in light wind.

Thanks for your insightful input Iccy. I envy those people that seem to possess an innate sense of wind-on-sail. Telltales are a big part of my sailing and I have to rely on them heavily. That's also another reason I find it tough in the light - I just don't know where the wind is. I'm definitely gonna look out that book.

[billy rubin]

I think you have that backwards. The float lifts at speed to raise the aft section OUT of the water.

could be. i dont know how they work. what i have read is that at a certain speed the pilot "sets the plane on the step," which decreases tbe drag enough to build more speed. obviously its time to look up some videos.

interesting stuff about tbe telltalez. on a motorcycle i can t zee what the air is doing. one interesting observation from an old norton roadracer named peter williams was to pay attention to the slipstream over your back. turbulence slows the machine, and when you felt your back suddenly become cold in a certain pozition you had zucceszfully attached a laminar boundary layer to your shape, lowereing drag and increasing speed potential. ive felt the transition myzelf.

are there  friction-reducing coatings you can apply to the hull to make it more slippery? sometimez there iz better living through chemistry.

[Siz]

I think you have that backwards. The float lifts at speed to raise the aft section OUT of the water.

could be. i dont know how they work. what i have read is that at a certain speed the pilot "sets the plane on the step," which decreases tbe drag enough to build more speed. obviously its time to look up some videos.

interesting stuff about tbe telltalez. on a motorcycle i can t zee what the air is doing. one interesting observation from an old norton roadracer named peter williams was to pay attention to the slipstream over your back. turbulence slows the machine, and when you felt your back suddenly become cold in a certain pozition you had zucceszfully attached a laminar boundary layer to your shape, lowereing drag and increasing speed potential. ive felt the transition myzelf.

are there  friction-reducing coatings you can apply to the hull to make it more slippery? sometimez there iz better living through chemistry.

If you're concerned about a laminar boundary layer, or even wind direction whilst on your bike, that's when I get off, thanks. We all get our thrills somewhere, I suppose, but anything motorised isn't for me. My business partner has a Hayabusa and a ZX10R which he throws around the English countryside every weekend. I'm just waiting for the phone call to tell me I have to start doing the company accounts for myself. I'll be really pissed off...!

The hull coatings are typically gelcoat (epoxy polymers). This is the standard finish on race dinghys - hard, smooth, high-sheen when polished. There're people out there who try to improve on that with products (RipCut for example) but I think that's fractions of fractions of benefit. I don't think even pros bother with that.

[billy rubin]

i guesz it depends on how consiztent you have to be to win. in a sailboat tbere are so many vastly differeing variablez i dont know how you keep track, because everythi g changez everything elze. youve already mentioned some of them.

but speed throgh a fluid rezpondz the same way, whether its air or water.. all other things being equal, youre faster than otherwise if you can take advantage of it. i cant find i fo on rip cut, but one thi g that might be relevant is that airflow of a column ofgas confined againstt a rough surface is more efficient than against a glazs-zmooth one. engine gas flow specializtz leave the inside of ports rough rather than polizhing them like tbey used to. zometimez they zpecifically roughen the ports to increase flow.

might be a relevant nugget of knowledge in there. what is the surface finish on americas cup racers hulls?

[billy rubin]

i just found thiz

https://www.sciencedaily.com/releases/2014/01/140117153637.htm

[Siz]

 

Good. Won't be polishing my hull anytime soon, then!

It'll be interesting to see any changes in design/materials in the future. In the meantime, I don't think this will be the deciding factor in my progress, or not, up the club rankings...

Don't know about current Americas cup tech. If they thought they could achieve an advantage I'm sure they'd explore and exploit. And wouldn't tell anyone.

The 2021 Americas Cup AC75 class rules were released a couple of years ago. According to this the hull finish is 'open', and surface treatments 'unlimited'. We'll possibly never know what they use/d.

https://www.sailingscuttlebutt.com/wp-content/uploads/2018/03/AC75_Class_Rule.pdf

[billy rubin]

little advantagez like that are swamped by bigger issues. cutting tbrough air on my machine is more a function of body english than horsepower, for example. i climb into weird positions at speed trying to redirect airflow in useful wayz.

why are the dinghiez cut off square in the stern? wouldnt a taper be better? or is a square cut that much better for planing?

[Siz]

little advantagez like that are swamped by bigger issues. cutting tbrough air on my machine is more a function of body english than horsepower, for example. i climb into weird positions at speed trying to redirect airflow in useful wayz.

why are the dinghiez cut off square in the stern? wouldnt a taper be better? or is a square cut that much better for planing?

Yes, planing (think water skis). A point would just cut in as the bow rises, I assume. I never thought to question the designers. I'm by no stretch an expert - keen club sailor at best.

At the highest levels, all the small percentages add up to a significant advantage. I always consider Dave Brailsford of Team Sky and Team GB in cycling who started from the most basic premise and smallest discrete element of performance and said 'what is that component/mechanical characteristic/biological function/tactic/metric? How can I improve that?'. They turned the standard for cycling excellence on its head and spent years at the top... until everyone else were forced to follow suit and closed the gap. I believe Americas Cup teams, with their inhumanly vast financial resources, have been on that ticket for some time. And can't hope to compete unless they are so fastidious.

Do you wear those little aero humps on your back on the bike? Teardrop helmet? It makes me shudder to think about going so fast as to justify these things.

[billy rubin]

five one percent improvements add up to five percent. im trying to think of what you could mess with on your boat while staying legal and not spending a lot. where are the rules printed? you might think that your skill set is the biggest hurdle but everything helps.

for my stuff i cant use an aero hump or helmet because it puts me into the partial streamlining class along with all the people running fairings. im running totally naked, so the only aero aids i have are body positioning and just making the machine small. this is it next to my bicycle



whatever minimizes the wind shadow is what i do.

[Siz]

five one percent improvements add up to five percent. im trying to think of what you could mess with on your boat while staying legal and not spending a lot. where are the rules printed? you might think that your skill set is the biggest hurdle but everything helps.

It's called a one-design for a reason 😂. I've read the class rules - they're not long or complicated. I've done quite a few tweaks to the control line system (I've now finished my continuous kicker and cunningham set up with bungee take-up), but that's pretty much all you have to tinker with. That's more personal preference than a speed improver. Other than buying a new sail (£900) and tidying up the centreboard slot gasket (requiring missing a day's sailing and a load of faff) there's not much I can do. There're way more effective improvements to be made to the driver before having to find small percentages elsewhere.

for my stuff i cant use an aero hump or helmet because it puts me into the partial streamlining class along with all the people running fairings. im running totally naked, so the only aero aids i have are body positioning and just making the machine small. this is it next to my bicycle



whatever minimizes the wind shadow is what i do.

Damn, that's ugly. I love it!

So you ride that thing, fast? Those drop bars look lethal. And not too much clearance for speed-humps. Would love to see a video of it in all it's active glory.