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PostPosted: Wed Mar 27, 2013 4:30 am 
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Tom, your comment & picture just goes to show, one person's "fun" is another person's annoyance or worse. If you are in the WaterTribe EC2013, I'm sure bow diving is the last thing you want--you are already wet and cold, and trying to reach a destination as quickly as possible. Bow diving and the stress it puts on a boat--I don't need that to have fun.

There are solutions for all of us. See, http://www.hobiecat.com/forums/viewtopic.php?f=71&t=46987

Keith

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PostPosted: Wed Mar 27, 2013 6:27 am 
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Hah! Yeah, it's only fun when the water is warm. For non-Floridians, "warm" means at or above 80 degrees. ;)


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PostPosted: Wed Mar 27, 2013 5:43 pm 
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I guess it is my time to get in on this...

I agree with the purists that the AI and TI are pretty good designs. Like Nohuhu said, shift your weight and trim your sails. I probably have more AI/TI miles and time in adverse conditions then most on this forum. I have pushed these boats to the limit in some extreme conditions.

The bow was designed as a Wave Piercing hull. If the water is continuously coming past the front hatch you have too much load and pushing the boat past the sea conditions. Reef and shift weight aft. You might find out that your overall average picks up.

On this years EC there were large following waves and high winds predicted. I shifted all my water load to the aft part of the boat and reefed down when the nose started diving. You do not want to travel faster than the wave. Surfing might be fun for a while but sitting on the edge of a four foot curling wave looking down into the trough in front of you can be dangerous.

I played with wave deflectors for a while. They are nice in limited conditions to provide some lift. Inside of a wave they are a huge negative, preventing the bow to pop back up.

One thing that has helped bow recovery are flow disruptors on the deck, just forward of the hatch. This was a pure accident. I mounted a thick foam strip just forward of the hatch to keep water off the hatch and reduce leaking. When a bow dives the water pressure and forward motion of the boat press the bow deeper preventing buoyancy to lift the bow back up. The water barrier on the bow disrupts the water flow creating turbulence and air pockets. Buoyancy recovers much faster. V-shape of the disruptor also sheds water faster.

When you spend a lot of time on the boat you can't help to notice small detail like watching the water as it flows along the hull.

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PostPosted: Wed Mar 27, 2013 6:25 pm 
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One thing I've noticed since I began to use hakas, my bow dives less. The reason, in my case, is that I have moved upwards of 20# of camping gear out of the bow onto the hakas. Most recently, I've also cut down on the weight in the stern by ditching my large Coleman 36 qt Xtreme cooler (although I am still using a 16-qt normal cooler.)

The distribution of weight is significantly different--less in the bow. In addition, the absence of my large cooler w/ ice may be saving me 20-30# in weight in the stern. Therefore, the hull is holding 40-50# less weight, and diving is reduced. When the bow does dive, it is less deep.

All very logical, you say. Well, yes it is, but it was my 22# hakas which made me (1) very weight conscious, and (2) aware that much of my bow load could be distributed to the hakas.

Keith

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"Any intelligent fool can make things bigger and more complex ... It takes a touch of genius and a lot of courage to move in the opposite direction." A. Einstein


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PostPosted: Wed Mar 27, 2013 7:37 pm 
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DogsLife wrote:
I guess it is my time to get in on this...

I played with wave deflectors for a while. They are nice in limited conditions to provide some lift. Inside of a wave they are a huge negative, preventing the bow to pop back up.

One thing that has helped bow recovery are flow disruptors on the deck, just forward of the hatch. This was a pure accident. I mounted a thick foam strip just forward of the hatch to keep water off the hatch and reduce leaking. When a bow dives the water pressure and forward motion of the boat press the bow deeper preventing buoyancy to lift the bow back up. The water barrier on the bow disrupts the water flow creating turbulence and air pockets. Buoyancy recovers much faster. V-shape of the disruptor also sheds water faster.

It's like having a secondary bow, and it's a time tested idea.

Image

No reason these could not be added on or molded into our hulls.

And using Hakas now allows us to trim our 150lb boats with 200lb of movable ballast. That's huge, if you learn how to use it.

I think if you EC buffs had a chance to experience the TI Amas on an AI, (Batboat style) you would be closer to the ultimate challenge boat. Though the nightmare would be harder.

I think what we need now is more length, buoyancy and planing capability in our Amas. That, with a couple anti-spray, anti-dive attachments to the bow will net a more civilized ride, while allowing for a larger sail plan.


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PostPosted: Thu Mar 28, 2013 2:01 am 
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This might sound dumb, but think about it for a minute. A seat on rails (as like a car seat) that you can slide forward and aft to move yourself aft the change the centre of gravity to lessen (quite significantly) the nose diving too deep.
My seat if about 6 to 8 inches aft of the standard moulded seat well (or bum bath) and I was much relieved at how much better behaved the AI was in the sort of steep short (scary) following sea Dogslife mentioned.

Cheers, Vintagereplica

If it works ok...modify it anyway!


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PostPosted: Thu Mar 28, 2013 4:57 am 
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NOHUHU wrote:
I think what we need now is more length, buoyancy and planing capability in our Amas. That, with a couple anti-spray, anti-dive attachments to the bow will net a more civilized ride, while allowing for a larger sail plan.


Maybe flat bottom amas like are now on Sizzor?

Image

I knew there was some reason that I bungee my life jacket to the fwd hatch! ;)


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PostPosted: Thu Mar 28, 2013 5:20 am 
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Vintagereplica wrote:
This might sound dumb, but think about it for a minute. A seat on rails (as like a car seat) that you can slide forward and aft to move yourself aft the change the centre of gravity to lessen (quite significantly) the nose diving too deep.
My seat if about 6 to 8 inches aft of the standard moulded seat well (or bum bath) and I was much relieved at how much better behaved the AI was in the sort of steep short (scary) following sea Dogslife mentioned.

Cheers, Vintagereplica

If it works ok...modify it anyway!

Absolutely. I've been shouting this out for years now, but everyone keeps carrying on about modifying the bow - IF YOU MOVE YOUR WEIGHT AFT, THE BOW DOESN'T BURY.

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PostPosted: Thu Mar 28, 2013 5:37 am 
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Good picture, Tom. I thought the flat bottom ama was interesting and smart. These boats sail faster when sailed flat; therefore, in keeping with that idea, why not have a flat bottom ama. Here is another picture of Sizzor's ama:

Image


Also,

Image


The Sizzor ama is low volume in the front and slightly tapered to the rear. Interestingly, it has an air intake near the front and an exhaust in the back. Both intake and exhaust are fairly high on the ama. I don't understand that.

Sizzor is clearly designed to sail flat. This is achieved in part by allowing the captain to easily move from port to starboard to level the boat.

Last year, Randy Smyth had his original Sizzor boat destroyed near the finish off Key Largo (it capsized and then was run over by a power boater who came to help.) This year's Sizzor 2013 is a total re-build. As with many prototypes (many of the boats in the WT EC2013), things break. I believe, but don't know for sure, that Randy's Sizzor suffered a race-ending break in the area of the ama/aka attachment on the first day of the race.

Finally, amas and hull have some rocker to keep them from spearing waves too much and to keep them on top,

Keith

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"Any intelligent fool can make things bigger and more complex ... It takes a touch of genius and a lot of courage to move in the opposite direction." A. Einstein


Last edited by Chekika on Thu Mar 28, 2013 7:33 am, edited 1 time in total.

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PostPosted: Thu Mar 28, 2013 6:16 am 
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Im not sold on the flat bottom idea - a lifting hull with directional stability seems more in line with what we need ...

... luckily we don't have to reinvent the ... umm ... Ama as there's already been a bunch of slide-rule work done on this by our fly-boy friends

Image

Image

designing in the "right" amount of lift may also solve the diving hull problem

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PostPosted: Thu Mar 28, 2013 6:34 am 
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Tom Ray wrote:
NOHUHU wrote:
I think what we need now is more length, buoyancy and planing capability in our Amas. That, with a couple anti-spray, anti-dive attachments to the bow will net a more civilized ride, while allowing for a larger sail plan.


Maybe flat bottom amas like are now on Sizzor?

I definitely agree with the flat bottom amas Tom. The latest 'A CLASS' cats here in Australia have flat bottom hulls and go like all stink!
Cheers Ian
If it works ok...modify it anyway


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PostPosted: Thu Mar 28, 2013 6:51 am 
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I just read this ... found it interesting

Quote:
The Tristar 18 had Amas that had a flat bottom, and with the rocker, at speed they were like water skis lifting the leeward ama to the surface

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PostPosted: Thu Mar 28, 2013 12:38 pm 
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chrisj wrote:
Vintagereplica wrote:
This might sound dumb, but think about it for a minute. A seat on rails (as like a car seat) that you can slide forward and aft to move yourself aft the change the centre of gravity to lessen (quite significantly) the nose diving too deep.
My seat if about 6 to 8 inches aft of the standard moulded seat well (or bum bath) and I was much relieved at how much better behaved the AI was in the sort of steep short (scary) following sea Dogslife mentioned.

Cheers, Vintagereplica

If it works ok...modify it anyway!

Absolutely. I've been shouting this out for years now, but everyone keeps carrying on about modifying the bow - IF YOU MOVE YOUR WEIGHT AFT, THE BOW DOESN'T BURY.


What Chris and VR said!
The 'diving hulls' issue is solved by adding haka (or a quarter deck) and shifting your weight to suit the conditions. The haka has changed the way the boat handles... but you have to get out on them to get the real benefit.
Another plus with them is that you are no longer sitting in a puddle of water or getting hit in the face by buckets of water when sailing at speed.


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PostPosted: Thu Mar 28, 2013 2:39 pm 
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Tom Ray wrote:
I knew there was some reason that I bungee my life jacket to the fwd hatch! ;)
Now there's an anti dive attachment we should have thought of in the Batcave!! :lol: Beats gluing water-weenies to the bow.

Truly great picts Keith. I understand sizzor is designed to fold its Akas? Similar to the AI?


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PostPosted: Thu Mar 28, 2013 4:26 pm 
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The holes on Sizzors are not for buoyancy while sailing. They are for righting the boat is it capsizes. Last year SOS used a similar design on his Ultimate Florida Tri. When the boat flips the ama floods loosing buoyancy and preventing a full turtle...

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