Tattoo 26 Production Suspended, factory relocating

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K9Kampers
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Re: Tattoo 26 Production Suspended, factory relocating

Post by K9Kampers » Wed Jul 29, 2015 11:53 am

BOAT wrote:Matt, if the hull speed is 7 knots why can't I hold that speed in a 12 knot wind? I can get there real fast but every 10 or 20 seconds it drops down to 6-1/2 and then shoots back up to 7 for a little bit and then just drops back down to 6-1/2.
Four variables in effect here...
The consistency of the wind acting on the sails.

The efficiency of the sails / sail trim.

The efficiency of the hull, dagger board, rudders in the water and their trim / drag.

The state of the water - flat, waves, etc.

All inconsistent variables.

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BOAT
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Re: Tattoo 26 Production Suspended, factory relocating

Post by BOAT » Wed Jul 29, 2015 12:16 pm

K9Kampers wrote:
BOAT wrote:Matt, if the hull speed is 7 knots why can't I hold that speed in a 12 knot wind? I can get there real fast but every 10 or 20 seconds it drops down to 6-1/2 and then shoots back up to 7 for a little bit and then just drops back down to 6-1/2.
Four variables in effect here...
The consistency of the wind acting on the sails.

The efficiency of the sails / sail trim.

The efficiency of the hull, dagger board, rudders in the water and their trim / drag.

The state of the water - flat, waves, etc.

All inconsistent variables.
Okay, I guess I'll just keep trying. HEY BEENE! You have one of those big kites, right? What kind of speed do you get down wind with that thing?

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grady
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Re: Tattoo 26 Production Suspended, factory relocating

Post by grady » Wed Jul 29, 2015 1:04 pm

K9Kampers wrote:
BOAT wrote:Matt, if the hull speed is 7 knots why can't I hold that speed in a 12 knot wind? I can get there real fast but every 10 or 20 seconds it drops down to 6-1/2 and then shoots back up to 7 for a little bit and then just drops back down to 6-1/2.
Four variables in effect here...
The consistency of the wind acting on the sails.

The efficiency of the sails / sail trim.

The efficiency of the hull, dagger board, rudders in the water and their trim / drag.

The state of the water - flat, waves, etc.

All inconsistent variables.
You can eliminate to first two with proper sail trim at all times. No really acevable single handing. You need an experienced person on the main sheet and head sail to do that. (also the skipper has to steer correctly).

Efficiency of hull, dagerboard rudders never change. In keeping sails trimed right should eliminated rudder trim drag.

State of the water is your variable that will keep you from maintaining a constant speed.

Generaly speaking when you are above hull speed down wind it is because of surfing down the swells.

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mastreb
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Re: Tattoo 26 Production Suspended, factory relocating

Post by mastreb » Wed Jul 29, 2015 1:09 pm

BOAT wrote:Matt, if the hull speed is 7 knots why can't I hold that speed in a 12 knot wind? I can get there real fast but every 10 or 20 seconds it drops down to 6-1/2 and then shoots back up to 7 for a little bit and then just drops back down to 6-1/2. It's driving me crazy! :| What the heck am I doing wrong?? It's obvious the boat will do 7 knots (if it could not do 7 it would not DO 7!!) so why can't I stay there?? :| :|
What you're describing is exactly hitting the hull speed, so it must actually be 6.5 knots, and my guess that it's closer to 7 is incorrect. Hull speed is defined as the point when the bow-wave reaches the mid-length of the boat, thus creating a "hill" the boat has to climb in order to make any further speed. You're pushing up that hill and slipping back. The wind simply doesn't have enough power in it to push you up onto a semi-plane.

So you're doing all the boat can do, and making 50% true windspeed efficiency which is the best I've ever been able to do as well. I think you're there, and there's nothing more that can be done.

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Tomfoolery
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Re: Tattoo 26 Production Suspended, factory relocating

Post by Tomfoolery » Wed Jul 29, 2015 1:33 pm

mastreb wrote:Hull speed is defined as the point when the bow-wave reaches the mid-length of the boat, thus creating a "hill" the boat has to climb in order to make any further speed. You're pushing up that hill and slipping back. The wind simply doesn't have enough power in it to push you up onto a semi-plane.
This is my favorite pic for illustrating that concept. This boat is at or near hull speed. It's sitting in a trough of its own making that it can't climb out of.

Image

I don't remember where I got this pic, or who's boat it is, but it's a great picture. 8)

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BOAT
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Re: Tattoo 26 Production Suspended, factory relocating

Post by BOAT » Wed Jul 29, 2015 1:44 pm

mastreb wrote:
BOAT wrote:Matt, if the hull speed is 7 knots why can't I hold that speed in a 12 knot wind? I can get there real fast but every 10 or 20 seconds it drops down to 6-1/2 and then shoots back up to 7 for a little bit and then just drops back down to 6-1/2. It's driving me crazy! :| What the heck am I doing wrong?? It's obvious the boat will do 7 knots (if it could not do 7 it would not DO 7!!) so why can't I stay there?? :| :|
What you're describing is exactly hitting the hull speed, so it must actually be 6.5 knots, and my guess that it's closer to 7 is incorrect. Hull speed is defined as the point when the bow-wave reaches the mid-length of the boat, thus creating a "hill" the boat has to climb in order to make any further speed. You're pushing up that hill and slipping back. The wind simply doesn't have enough power in it to push you up onto a semi-plane.

So you're doing all the boat can do, and making 50% true windspeed efficiency which is the best I've ever been able to do as well. I think you're there, and there's nothing more that can be done.
Okay, that makes sense to me now. I run really really light so I think that is the only reason I get such high accelerations in light wind and it seems like your description of pushing up a hill and slipping back is EXACTLY what it feels like to me when it's happening. I bet if i were to run a little heavier I would not be pushing up the hill so much. I guess it's time to install my fresh water tanks in the bow like Highlander and put in the pressure system for the faucet. I think a little extra weight in the bow might smooth out my rate of travel. Thanks Matt, (you too Tom). By the way Matt, I talked to Mike on the phone today. I will not discuss it here but maybe we should go get some beer and I will elaborate. You would not be in the market for a really fast and nice 1.5 million dollar 70 footer would you? (Sure would love to crew for you if you did).

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Highlander
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Re: Tattoo 26 Production Suspended, factory relocating

Post by Highlander » Wed Jul 29, 2015 6:28 pm

BOAT said
The number one thing I am always forgetting is that big motor on the back - I use it so seldom that I totally forget I can make up a full hours worth of sail travel in less than 15 minutes! (DUH!) :(

Yep ur fastest sail on ur boat is not ur Spinnaker it,s ur Iron Genny
https://youtu.be/I8JGckmN5n0

J :P

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mastreb
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Re: Tattoo 26 Production Suspended, factory relocating

Post by mastreb » Mon Aug 03, 2015 1:52 am

BOAT you have my digits, use them!

And correct: A light boat accelerates quickly and sails fast in very light air. However, once there's enough air (which for a Mac is 12 knots) weight no longer matter much at all, and they'll all do 6.5 knots. Actually because it is actually possible for a light MacGregor to plane under sail in a dead down-wind, bow-low configuration, you might get a bit more speed out of a light boat. But the serious advantage of a light boat is gone after 10 knots of true wind.

I won a Beneteau class race in light air in my big boat using MacGregor tricks like putting all my "rail meat" up on the bow and going dead down wind wing-on-wing when everyone else was gybing on a broad reach with their expensive asymmetricals. Was wishing I could pull up the rudders and the keel--would have smoked them. Doing 3 knots to the mark when everyone else is making 2.5VMG wins races as it turns out.

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dlandersson
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Re: Tattoo 26 Production Suspended, factory relocating

Post by dlandersson » Mon Aug 03, 2015 6:36 am

How about "they are potentially capable of reaching 6.5 knots?" My X has never reached 6 knots under sail and I'm not losing any sleep over this. I chalk it up to the skippers ability (or lack thereof) :)
mastreb wrote:BOAT you have my digits, use them!

And correct: A light boat accelerates quickly and sails fast in very light air. However, once there's enough air (which for a Mac is 12 knots) weight no longer matter much at all, and they'll all do 6.5 knots. Actually because it is actually possible for a light MacGregor to plane under sail in a dead down-wind, bow-low configuration, you might get a bit more speed out of a light boat. But the serious advantage of a light boat is gone after 10 knots of true wind.

I won a Beneteau class race in light air in my big boat using MacGregor tricks like putting all my "rail meat" up on the bow and going dead down wind wing-on-wing when everyone else was gybing on a broad reach with their expensive asymmetricals. Was wishing I could pull up the rudders and the keel--would have smoked them. Doing 3 knots to the mark when everyone else is making 2.5VMG wins races as it turns out.

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mastreb
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Re: Tattoo 26 Production Suspended, factory relocating

Post by mastreb » Mon Aug 03, 2015 12:04 pm

dlandersson wrote:How about "they are potentially capable of reaching 6.5 knots?" My X has never reached 6 knots under sail and I'm not losing any sleep over this. I chalk it up to the skippers ability (or lack thereof) :)
You just need more wind :D

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