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PostPosted: Sat Aug 15, 2009 6:19 pm 
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rokraider wrote:
I managed to get out today and was experimenting with the Mirage drive. I believe pedalling it make a substantial difference. It was quite gusty today with choppy water. I have invested in a Velocitek speed puck http://www.velocitek.com/products/speedpuck which has proven to be very useful. I was averaging around 6 knots today with a recorded max of 8 Knots. It was too rough to get any real speed up and kept burying the bow and Amas into waves that constantly knocked a lot of speed off. I found I could point probably 10 degrees higher if I peddled.
I experimented with the dagger board up and the Mirage blades down. I found it didn't point as well as the dagger board and also lost speed, presumably due to drag. As I see it, unless you have them both exactly in alignment, the front blade will cause turbulence that is then stirred up further by the rear blade. Also the blades do not sit flat so they will twist wherever they feel like going. They do offer lateral resistance but at the expense of speed. I found it faster with the blades separated and flat against the hull, although I am interested in trying them hanging down at 45 degrees or so and see if that makes any difference. I also tried the dagger board and the Mirage fins down whilst trying to point in quite strong winds, I believe it helped a bit with lateral slippage, but I still couldn't point anywhere near as high as a standard monohull. The rudder was constantly being overpowered in strong gusts whilst going upwind.
I believe we will see a few more down here next season, it is attracting a lot of attention.
My next move will be some tramps. I can't use the full width setup as I often need to quickly fend it off mudbanks with the paddle when the wind blows it sideways onto the mud when I am trying to take pictures of the seals I am helping to monitor. The channel isn't wide enough to anchor easily. I think Pirates design looks the best bet for what I need and the spray skirt at the front will also be very useful. Are you going to have any for sale Pirate?
Interesting idea-the Amercas Cup boats have those exra wings at the bottom of the keel pointing down around 45 degrees

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PostPosted: Sat Aug 15, 2009 6:39 pm 
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Location: Terrigal NSW, Australia
reconlon wrote:
Quote:
Does your experience show if the boat is assisted or hampered to windward if both the daggerboard and the mirage drive are in place at the same time Bob?...Pirate

Assisted

When going upwind in all but light wind, it will point better with both the daggerboard and the fins down.

Downwind, except for in heavy wind or larger waves, both out or up is best for speed.

So Bob, I'm trying to formulate some Dagger board rules. Do you have any modifications, additions to the following:

When sailing upwind:
- When the Mirage drive is in and being used, the Dagger board has little effect in light winds, but becomes more useful as the wind gets stronger
- When the Mirage drive is out, the Dagger board is needed to help the boat track at all wind speeds.
- At higher boat speeds, the Dagger board can be retracted/rotated backward to lessen weather helm.

When sailing downwind:
- The Dagger board is not necessary to aid tracking and slows the boat somewhat due to the extra drag.

When sailing perpendicular to the wind:
- The Dagger board may lessen the tendency of the boat to heel in stronger winds and so lessen the tendency of the leeward ama to become submerged.

At all points of sail:
-The Dagger board improves steering by providing a fulcrum for the boat and may be useful for this purpose in difficult conditions, such as strong wind or waves.

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PostPosted: Sat Aug 15, 2009 9:40 pm 
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My next move will be some tramps. I can't use the full width setup as I often need to quickly fend it off mudbanks with the paddle when the wind blows it sideways onto the mud when I am trying to take pictures of the seals I am helping to monitor. The channel isn't wide enough to anchor easily. I think Pirates design looks the best bet for what I need and the spray skirt at the front will also be very useful. Are you going to have any for sale Pirate?

I am not in the game Aledal but have been working on mine and now believe they are now real winners. When I have finished road testing them, my upholstery guy who put them together is happy to knock some out, so I will let you know when that happens. Unfortunately is just too gusty today to go sailing without expecting gear breakage. Here is the current conditions here. Warm winters day but strong northerlies with the expectation of a strong southerly change shortly.
16/02:00pm 22.7 15.6 10.8 47 6.6 NNW 39 61 21 33 998.0 - 0.0
16/01:57pm 22.5 15.2 10.3 46 6.7 NNW 39 61 21 33 998.1 - 0.0 .....Pirate

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PostPosted: Sun Aug 16, 2009 12:12 am 
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Location: Terrigal NSW, Australia
Pirate wrote:
I am not in the game Aledal but have been working on mine and now believe they are now real winners. When I have finished road testing them, my upholstery guy who put them together is happy to knock some out, so I will let you know when that happens.

Pirate, do you have fibreglass reinforcing rods like the Hobie tramps?

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PostPosted: Sun Aug 16, 2009 12:43 am 
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chrisj wrote:
Pirate wrote:
I am not in the game Aledal but have been working on mine and now believe they are now real winners. When I have finished road testing them, my upholstery guy who put them together is happy to knock some out, so I will let you know when that happens.

Pirate, do you have fibreglass reinforcing rods like the Hobie tramps?

Chris - where are the fibreglass reinforcing rods? Are they at the rear of the tramps where they clip onto the rear aka or somewhere else??

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PostPosted: Sun Aug 16, 2009 12:49 am 
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I assumed they were front and rear Mickey. I don't have a pair so I'm not sure. Perhaps someone who has them can answer that.

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PostPosted: Sun Aug 16, 2009 3:24 am 
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chrisj wrote:
I assumed they were front and rear Mickey. I don't have a pair so I'm not sure. Perhaps someone who has them can answer that.


They are along the rear of the tramps where the straps are. It's a single fibreglass rod spaning the width of the tramp.
The front is supported by looping over the forward aka.

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PostPosted: Sun Aug 16, 2009 4:09 am 
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Cowsgomoo wrote:
chrisj wrote:
I assumed they were front and rear Mickey. I don't have a pair so I'm not sure. Perhaps someone who has them can answer that.


They are along the rear of the tramps where the straps are. It's a single fibreglass rod spaning the width of the tramp.
The front is supported by looping over the forward aka.

Thanks for the info Cowsgomoo - that's what I thought.
Are they flexible at all or completely rigid?
I imagine they are sewn in to avoid loss :roll:

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PostPosted: Sun Aug 16, 2009 4:34 am 
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chrisj wrote:
Pirate wrote:
I am not in the game Aledal but have been working on mine and now believe they are now real winners. When I have finished road testing them, my upholstery guy who put them together is happy to knock some out, so I will let you know when that happens.

Pirate, do you have fibreglass reinforcing rods like the Hobie tramps?


Hi Chris, Our tramps have a semi flexible plastic tube completely sewn in just behind the front aka to prevent wrinkles at that end and an aluminium tube at the back that is semi sewn in. This tube is about 20 mm in diameter and gives the tramp both lateral rigidity and the purchase for the three straps to wrap around to pull it back to the rear aka. These straps are sewn to be back of the tramp sleeve to prevent slippage when they are being tightened. I am still tweaking the system but it is working out to be a good thing. I was going out again today to test the spray skirt part in some wind and wave after a nice but quiet attempt yesterday, but the wind gust were just too violent so I stayed at home and worked instead. I ended up chasing around after speed boat wakes yesterday to prove the skirts which seemed to be doing their job very well. I will keep you informed when I have more....Pirate :wink:

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PostPosted: Sun Aug 16, 2009 7:28 am 
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Thanks Pirate. A local sailmaker up here reckons he can knock a set up for a reasonable price. You've convinced me that half-width is the way to go, so I'm watching your progress with interest. Any info on problems you encounter, or things you wish you'd done with the wisdom of hindsight, would be much appreciated.

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PostPosted: Sun Aug 16, 2009 8:07 am 
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Pirate wrote:
My next move will be some tramps. I can't use the full width setup as I often need to quickly fend it off mudbanks with the paddle when the wind blows it sideways onto the mud when I am trying to take pictures of the seals I am helping to monitor. The channel isn't wide enough to anchor easily. I think Pirates design looks the best bet for what I need and the spray skirt at the front will also be very useful. Are you going to have any for sale Pirate?

I am not in the game Aledal but have been working on mine and now believe they are now real winners. When I have finished road testing them, my upholstery guy who put them together is happy to knock some out, so I will let you know when that happens. Unfortunately is just too gusty today to go sailing without expecting gear breakage. Here is the current conditions here. Warm winters day but strong northerlies with the expectation of a strong southerly change shortly.
16/02:00pm 22.7 15.6 10.8 47 6.6 NNW 39 61 21 33 998.0 - 0.0
16/01:57pm 22.5 15.2 10.3 46 6.7 NNW 39 61 21 33 998.1 - 0.0 .....Pirate
I didnt ask about selling the tramps I think rokraider did.I asked if you think "Island 2 is gaining on Island 1".The original post actually. (both boats have brass pins) :wink:


PS-I like your design more -simply for having access to the water...

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PostPosted: Sat Aug 22, 2009 6:13 am 
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chrisj wrote:
Bluemark, the Mirage drive can't direct the side force forward, because it is acting at 90º, but it does direct the resultant force forward and as the vector triangle shows, the greater the force (BA) from the drive, the more the resultant force (CA) approaches straight ahead.


I am aware that the result of peddling a mirage drive is a forward force 90º from the side force, but a mirage drive most definitely DOES convert a side force into a forward force - that is how they work - moving back and forth from side to side to move you forward 90º from the direction they are moving. Now where my 25 year old memory loss of dynamics fails me is in figuring out just what happens when a side force is applied to the laterally moving mirage fins.

The side side force (wind) makes the whole boat move sideways in the water, resulting in a vector force from the water directly opposite the wind. Keels and daggerboards are surfaces that allow that opposite vector from the water better oppose the side vector force from the wind. A moving mirage fin adds to that opposing force by moving into it, thus increasing the anti wind side force. The opposite fin is moving with the side force, so it has reduced opposing side force... Now those forces should even out to be same as a single stationary fin pointing straight down like a daggerboard - but it isn't, it also moving you forward. And darn it, it is simply fact that a moving mirage drive lets me sail much closer to the wind than having both fins pointing straight down like two extra dagger boards.

Something very cool is happening in the dynamics of moving mirage fins, side forces, and wind.


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PostPosted: Sat Aug 22, 2009 8:05 am 
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BlueMark wrote:
chrisj wrote:
Bluemark, the Mirage drive can't direct the side force forward, because it is acting at 90º, but it does direct the resultant force forward and as the vector triangle shows, the greater the force (BA) from the drive, the more the resultant force (CA) approaches straight ahead.


I am aware that the result of peddling a mirage drive is a forward force 90º from the side force, but a mirage drive most definitely DOES convert a side force into a forward force - that is how they work - moving back and forth from side to side to move you forward 90º from the direction they are moving. Now where my 25 year old memory loss of dynamics fails me is in figuring out just what happens when a side force is applied to the laterally moving mirage fins.

The side side force (wind) makes the whole boat move sideways in the water, resulting in a vector force from the water directly opposite the wind. Keels and daggerboards are surfaces that allow that opposite vector from the water better oppose the side vector force from the wind. A moving mirage fin adds to that opposing force by moving into it, thus increasing the anti wind side force. The opposite fin is moving with the side force, so it has reduced opposing side force... Now those forces should even out to be same as a single stationary fin pointing straight down like a daggerboard - but it isn't, it also moving you forward. And darn it, it is simply fact that a moving mirage drive lets me sail much closer to the wind than having both fins pointing straight down like two extra dagger boards.

Something very cool is happening in the dynamics of moving mirage fins, side forces, and wind.

Sorry Bluemark, I should have been more precise in my language. As you point out, the two fins should cancel each other out with respect to any sideways force generated by the drive. The effect is that the drive as a whole exerts only a net forward force on the boat and as such cannot redirect the side forces from the sails. As to the question of why the boat can point higher with a moving Mirage drive, do you think that you would get the same effect if it was a propeller pushing the boat forward? We need to ask what it means to point higher. Obviously, you can travel straight into the wind with the Mirage drive, so the real meaning of pointing higher is travelling closer to the wind without the sail luffing. What do you think of the hypothesis that it is the higher apparent windspeed generated by the Mirage drive that reduces the tendency of the sail to luff at any given angle to the wind?

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PostPosted: Sat Aug 22, 2009 8:07 pm 
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The movie "Wind" reminds me of this discussion.
The engineer confronts the sailor.They both disagree...
while trying to create a "new" boat design that would defeat Australias "Platapus".
But you two are both engineer & sailor.

The drive pulls the Island into the water then pushes it up while propelling it forward.
But at some speed it is rendered useless.

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Last edited by Aledal on Sun Aug 23, 2009 5:29 am, edited 1 time in total.

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PostPosted: Sat Aug 22, 2009 9:50 pm 
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:D All I know is this. When you`re out there on the wild water...you can throw logic out the window. All the engineering and intellectual discussions mean nothing compared to what nature can do.


Years ago after buying my first Outback I used to "hover" in one place several thousand feet offshore listening to music riding over the most beautiful swells hours at a time.
Several times I went out with "small craft" warnings in affect. The Outback handled glowingly.Without the inflatable amas.Low center of gravity. "Sit on top " design. Mirage drive.

Need I say more? :)

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