This is a common misunderstanding. While it's true that "All Macs are white below the waterline", the blue hull is slowed not by its drag through the water, but by heat surface effects warming the boundary layer air around the hull. The coefficient of solar photonic absorption (vs. reflection) of the blue hull is dramatically higher than that of the white hull. This creates an increased surface temperature at the hull-air boundary, which reacts with the surrounding air to cause thermal blanketing of the hull. You see a similar thermal blanket coming off of a desert highway, for example, to a much greater degree.
The thermal blanket created around the blue hull is higher pressure than the surrounding cool air flowing past it, so it pushes away from the hull as it heats, thus creating turbulence and drag around the entire hull as air flows past it. The ultimate effect is that the coefficient of drag (Cd) of the blue hull through the air is higher than that of the white hull. The effect is most pronounced under direct sun. In a building (for example, a wind tunnel where Cd might be testable) the effect is so small as to be virtually undetectable, so you won't find scientific test results that can refute this.
mastreb wrote:This is a common misunderstanding. While it's true that "All Macs are white below the waterline", the blue hull is slowed not by its drag through the water, but by heat surface effects warming the boundary layer air around the hull. The coefficient of solar photonic absorption (vs. reflection) of the blue hull is dramatically higher than that of the white hull. This creates an increased surface temperature at the hull-air boundary, which reacts with the surrounding air to cause thermal blanketing of the hull. You see a similar thermal blanket coming off of a desert highway, for example, to a much greater degree.
The thermal blanket created around the blue hull is higher pressure than the surrounding cool air flowing past it, so it pushes away from the hull as it heats, thus creating turbulence and drag around the entire hull as air flows past it. The ultimate effect is that the coefficient of drag (Cd) of the blue hull through the air is higher than that of the white hull. The effect is most pronounced under direct sun. In a building (for example, a wind tunnel where Cd might be testable) the effect is so small as to be virtually undetectable, so you won't find scientific test results that can refute this.
mastreb wrote:This is a common misunderstanding. While it's true that "All Macs are white below the waterline", the blue hull is slowed not by its drag through the water, but by heat surface effects warming the boundary layer air around the hull. The coefficient of solar photonic absorption (vs. reflection) of the blue hull is dramatically higher than that of the white hull. This creates an increased surface temperature at the hull-air boundary, which reacts with the surrounding air to cause thermal blanketing of the hull. You see a similar thermal blanket coming off of a desert highway, for example, to a much greater degree.
The thermal blanket created around the blue hull is higher pressure than the surrounding cool air flowing past it, so it pushes away from the hull as it heats, thus creating turbulence and drag around the entire hull as air flows past it. The ultimate effect is that the coefficient of drag (Cd) of the blue hull through the air is higher than that of the white hull. The effect is most pronounced under direct sun. In a building (for example, a wind tunnel where Cd might be testable) the effect is so small as to be virtually undetectable, so you won't find scientific test results that can refute this.
Now you gone and given away the secret how the Blue Hulls levitate over water and therefore are not bound by Hull speed making it the faster .
c130king wrote:You can keep Doug and Phil company at the back of the pack in their blue hulls.
ROFL
Fxwg80hd wrote:The thermal blanket created around the blue hull is higher pressure than the surrounding cool air flowing past it, so it pushes away from the hull as it heats, thus creating turbulence and drag around the entire hull as air flows past it. The ultimate effect is that the coefficient of drag (Cd) of the blue hull through the air is higher than that of the white hull. The effect is most pronounced under direct sun. In a building (for example, a wind tunnel where Cd might be testable) the effect is so small as to be virtually undetectable, so you won't find scientific test results that can refute this.
Seven days from now I'll be on the beach with my toes in the sand and a beer in my hand. There will be brats on the grill and music in the air. I'll get the chance to hang out with some old friends and meet some new ones. Together we will relax, kick back and enjoy a sunset over the Fort George inlet as the sky explodes with color. Rumor has it there might even be a canon for a proper sunset salute. The tide will recede and Untethered will be resting on a soft bed of white beach sand (hopefully not as high as last year).
The next morning we will motor south on the ICW, turn left and hit the ocean. 13 Macs, all under sail, will enter St. Augustine harbor later that day.
There's still a week to plan, a week to pack and a week to stop coming up with excuses.
You still going to the Jag's game on Thursday? I have tickets for me and DJ (aka Gilligan).
Checked out the 10-day forecast...Saturday is calling for 86 degrees, 0% chance of rain, 10 knots from ENE...perfect for sailing to St. Augustine...but who can trust a 10-day forecast...
König is mast up in my driveway for some final projects, cleaning and then loading...but Irene is heading our way...will have to go put the mast down this evening. And Irene may wash out our plans for Journey/Foreigner/Night Ranger concert on Sunday...
Hitting the road Wednesday afternoon. See you soon.
As it stands right now I will be in Jax on Monday. I plan on attending the game but that is subject to change. My crew will be arriving that evening and I will have to get him settled in. A buddy of mine is out of town and has season tix but last year I scalped a set of two for 10 bucks, I just had to wait until after kick off. Either way, I will be at Downtown Thursday night.
Have you made reservations for the city marina yet? Game days are the only times reservation or docking fees are required.
I'll keep my fingers crossed that you get to the show on Sunday. That sounds like a great way to start the week.
Speaking of masts in the driveway, guess what just showed up in mine. My replacement mast has finally arrived! It appears to have made the 2,500 mile trip without any damage. So it looks like the weekend will be spent transferring all the hardware from the old mast to the new. Hopefully it won't be too difficult. Think I'll take this opportunity to install an anchor light and maybe run my main halyard aft.
I'm stoked that I'll actally be able to sail from Jacksonville to St Augustine. I was planning on motoring the whole way. Can't wait for next weekend!
Yes, I have City Marina reservations for Thursday/Game Day. Got tickets from Stub Hub for $25 ($88 face value). We are in Section P (Middle Deck around the 20 yard line).
Joel,
Great news! Hopefully you can get everything complete. I don't have any knowledge about fiberglass repair or installing a plate (sounds like a good idea).
We'll be provisioning and re-provisioning our Mac this weekend along with finishing up a couple projects. I have some meetings at work that I cannot escape until Tuesday afternoon. We'll be Florida bound by this Tuesday evening!
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