Sharpen up your babe with

[ebb]

A finer entry.
Anybody ever consider what a sharper entry at the waterline might do for the A/C?

Wouldn't be too hard to add it on.
Add about an inch or more to the waterline.
Depending on how fine you wanted it.
Would taper off to the normal rounded bow above and below
- with maybe 6" above and 6" below the WL coming to a sharper edge.
???

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(this guy is a frikkin trouble maker)

[bill@ariel231]

ebb

I expect you might see a better ROI on your labor with high tech sails (mylar/carbon), a smooth bottom and a well faired depth sounder (assuming its a through-hull type).

cheers,
bill@ariel231

[ebb]

Hole' Makerale!
Carbon Sails?? On an Ariel? They laughed all the way to the bank.

Still, I'd have an extra edge with a couple more inches WL :D

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Personally favor the soft entry, but wonder if a sharp one would help in pointing the ship further up into the wind???
ROI = return on investment(?)

I've placed 338's sonar on the stem, where I have been thinking of adding some fairing in front and behind.
The estate here experienced extensive flooding when a stream partially breached it's bank. Water left its signature in various ways, most noticable was where streaming water went over a projection the down side was deeply goughed out by tumbling action. Same with any projection on a boat bottom, I would think. Even a mushroom thru-hull(s) would slow a boat down, it might be significant.

Likewise the waterstream as it exits at the rudder - or as is pointed out, the hull is parting stationary molecules as it pushes through - making the rudder another area of slow-down.

[bill@ariel231]

The PHRF folks I occasionally race against frown on hull mods and levy a heavy handicap for anything other than a clean bottom and fairing of through hulls.

Periwinkle's mylar 130 was the biggest speed boost this year (better shape than my old sail and optimized for local conditions mid summer in narragansett bay)

Theoretically, hull speed is a function of waterline length. US sailing's formula is Hull Speed (kts) = 1.34 * sqrt( LWL (in feet))

http://www.sailingusa.info/cal__hull_speed.htm

if you sharpen the hull and fair in roughly 3 inches in a boat with an 18.66' waterline you'll end up at 18.91' LWL.

original hull speed = 5.79kts
lengthed LWL = 5.83kts

4/100th of a knot faster? my vote is a clean bottom given the likely phrf penalty

[ebb]

Dang, these mathematicians
get in the way of improvements :p

Most of the time I prefer a dry bottom.

No, I wasn't looking at it from a cheat point of view,
just wondering if 'techwise' it would change the HANDLING of the Ariel.
For the better. Or not all all.

Sharper entry, part water better, point higher. (?)

EG, a wood version of the Ariel might have a finer entry.
Modern frps have a finer entry....
(Modern freighters, tho, have a bulbous projection.)

I know one racer that wouldn't frown at a few extra knot points.
But not by increasing WL, of course! He does make us sit on the rail!!

[bill@ariel231]

fairing of projections forward of the mast where laminar flow might be at least possible are the biggest payoff. I've faired the depth sounder and made no other changes below the waterline beyond the annual bottompaint polishing. I'll post a picture of the sounder tonight....

[mbd]

...beyond the annual bottompaint polishing. I'll post a picture of the sounder tonight....
A quick question Bill: not to detract from Ebb's thread here...

Do you use "hard" bottom paint, the non-ablative stuff?

OK, two. That 130 headsail you're talking about: its' on a roller furling?

[bill@ariel231]

I'm using single season ablative these days, although it gets a good bit o' fine sanding before getting tossed in for the season.

ps. the mylar 130 is on a furler (see the first pix in the gallery thread for A-231). The sail is by crusing-direct (aka. north sails online).

[bill@ariel231]

here are two views of the depth sounder as faired in (stbd side vee berth). By contrast, the original electro mechanical 'ducer was about the side of a lunch box bolted to the hull...

cheers,
bill

[ebb]

Fairing projections has its problems too.
Fairing would not follow the fore and aft center line of the boat but would take into account the laminar flow of water over the hull which isat some angle off centerline - ie not parallel to the keel.

Generally, as I understand it from a practical perspective, you are better off placing projections 'aft of the mast' where the waterflow is beginning to breakaway from the hull. With exception of the sonar.

Wonder if anybody has placed telltails over the underwater body of a keelboat in a test tank and photgraphed the flow patterns?

We can assume that the flow pattern is at some angle up from the keel as the hull goes forward thru the water. And because the hull is an ever changing volume shape, the flow is at ever changing angles on the hull.

Also wonder if the relatively slow movement of a keelboat hull has other things happening that are not seen at max speed testing. Would think that the laminar flow. the layered stickiness, would continue further aft on an A/C - and maybe not break apart significantly until it reaches the rudder. (???)

[ebb]

Have attempted to post a blueline site in the Technical section here under the title: Safe bottom paint time.

Typing the above title onto google produces a bunch of info on the subject I do not have time to filter thru rightr now.