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Matt, any comment on diving AI hulls?
http://www.hobie.com/forums/viewtopic.php?f=71&t=20589		 Page 6 of 13
Author:  ChaosDave [ Thu Feb 11, 2010 6:23 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
I wouldn't call that submarining and no you wouldn't need a wave deflector in those conditions.
Author:  Chekika [ Thu Feb 11, 2010 7:08 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
Nice video, Tom, but what you are showing has NOTHING, ABSOLUTELY NOTHING to do with my point in this thread. Travelling on a beam reach in 6” chop is NOT WHAT WE ARE TALKING ABOUT. To experience what we have been talking about you need to get out on the ocean in 2-3 foot chop (2-3 foot waves at high frequency), and run before a 15-20 mph wind. Then, you will understand some of the comments here.

Maybe we have a misunderstanding of terms. Here is a picture of my boat beginning a “dive” below a wave. I would not call that "piercing." My bow is going under that wave, not through the wave. Let me assure you, this behavior plays hell with boat speed. Fun, yeah, it can be, but not if you are on a 6- to 8-day trip, and something breaks. That is my concern, and that is why I think Hobie needs to attend to this problem. From Matt's comments, I think that will be the case.

BTW, this picture was taken about 40 miles (64 km) to the nearest marina and help.

Image

Please note that the sail is about 50% furled.

Keith
Author:  Tom Ray [ Thu Feb 11, 2010 8:10 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
Hee hee! I've been in that picture, Keith! :mrgreen:

We have some pretty ugly chop here from time to time, and I go through it all the time.

I just think that anything that creates enough lift to correct the situation in your picture is going to create a huge amount of drag in the process.

Up periscope, baby! :mrgreen:
Author:  Chekika [ Thu Feb 11, 2010 8:43 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
Tom, except for hull rocker, nothing mentioned here would slow your boat in the conditions shown in your video. A well-designed, add-on wave deflector would have no effect on your speed in your video--if people did not need it, they would not buy it. And, I think, the wave-deflector in difficult conditions would maintain a more even speed by keeping your boat from diving. You are NOT maintaining your speed if your boat is diving below a wave.

There are simple solutions to most of this problem. They should be made available without people having to do their own design and development--that is what we pay Hobie a premium price for.

Down the road, maybe Hobie might see a market for a more ocean-going hull/ama design.

Least, I get hammered for being ungrateful, let me express again, that this forum is incredibly useful (thanks to Hobie, Matt, and all the contributers), and Hobie has designed, with upgrades, an excellent boat in the AI. I, also, have no doubt that this forum, and its contributions, has helped Hobie further the AI design.

Keith
Author:  mmiller [ Thu Feb 11, 2010 9:18 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
Question...

How much weight in the boat on this trip all combined including you and your gear, food etc?

How much is in the forward hatch as compared to the aft cargo area?
Author:  Chekika [ Thu Feb 11, 2010 9:36 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
Hi Matt,

Probably on the order of 300-325# for me, 225-240# for my wife--and her boat was very dry inside. Bill, about the same as me, maybe 25# more.

I can only guess at how much was forward. Most of our 6-gal water goes in the tough to get at, wet places like the stern and underneath the cockpit area. Clothing, tent, food go in the bow. Our boats are pretty well balanced looking at the trim. Here is a picture of my wife's boat as we started the trip.

Image

Bill remarked he was putting more weight in the stern. I was trying to put more weight in the bow, because I think the stern TnS hatch is a source of water in the hull. We were all diving on the windy days.

Keith
Author:  mmiller [ Thu Feb 11, 2010 9:56 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
I would suggest investing in large dry bags to get more weight (especially water and heavy stuff) in the aft cargo areas when sailing downwind in these conditions. Once you start sailing and running in the swells... the bow is forced down. I think a hull trim with stern down might be better when you start out.
Author:  TIDALWAVE [ Thu Feb 11, 2010 10:18 am ]
Post subject:  Thanks, Chekika for the bow-under photo!
This is exactly how my AI acts many times (and I am out without any significant
additional weight). I weigh about 200lbs, and I wonder if being that much
heavier than the average may help the bow go under. As I mentioned before,
my lake, a flat-shallow pan, is about 50 km long (30 miles) but only 10 m (30+ ft) at the deepest. My landing is located on the downwind side of the lake. So even a moderate
freshening of the wind will generate an increase from about 1 ft to more than 5-6 ft
within just minutes, with nasty white caps. The wavelengths don't have time to
increase, so waves get 'very' steep very quickly. To get off the lake, I have to turn around
and go with the wind on a stern or a broad reach. I have gotten to the point that
I usually expect a considerable number of times that I am going to submerge the bow if the
wind comes up. The AI will start to surf and dig into the leading crest.

I appreciate Matt's (Hobie's) efforts to provide us with new products which enhance our
enjoyment of using Hobie boats! I hope that Hobie can find a wave deflector manufacturer as quickly as they did for the tramps.
Author:  Chekika [ Thu Feb 11, 2010 10:45 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
Good advice, Matt, but more weight in the aft areas would be tough to do. Here are pictures of Bill and my boats.

Image

Image

Bill estimates his cooler at 70#, mine is about 50#. Much of the 6-gal of water in each boat is also in the stern. In my and Nancy's boat there was nothing real heavy in the bow: clothes, tent, a couple food bags, and miscellaneous. The captain's seat is more in the stern than the bow, so his/her weight is more in the stern. If Bill or myself put much more weight in the stern, it would be under water much of the time.

Keith
Author:  mmiller [ Thu Feb 11, 2010 10:48 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
We know that the AI hull is long and low and presses down when powered up. It's a matter if water line vs wave height. At some point the length of a hull is longer that the wave and as the stern rises the bow drops into the trough.

Even huge ships have these issues. And these guys are not pressing hard with sail area up high. They are at a near standstill.

Love these videos! Check the first BIG one at about 0:20

[youtube]http://www.youtube.com/watch?v=tfEo6E6nElE&feature=player_embedded[/youtube]
Author:  Chekika [ Thu Feb 11, 2010 10:54 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
Exciting video! I'm not going out in that stuff either!!

Matt, please keep pushing for a bow wave deflector--that is bound to help. Thanks.

Keith
Author:  mmiller [ Thu Feb 11, 2010 10:56 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
And yes... you can pitchpole anything:

[youtube]http://www.youtube.com/watch?v=yqJ7YgN42Gg&feature=player_embedded[/youtube]
Author:  Chekika [ Thu Feb 11, 2010 11:24 am ]
Post subject:  Re: Matt, any comment on diving AI hulls?
That is amazing. How did those people stay w/ that boat?? They must have had a bit of practice at that. Whoa!

That was good, real good!

Keith
Author:  mmiller [ Thu Feb 11, 2010 12:15 pm ]
Post subject:  Re: Matt, any comment on diving AI hulls?
Yeah... those guys are the top cat sailors in the world sailing these 40 footers.

Tommy Hilfiger is skippered by Randy Smythe

Not as lucky on this one!

Image

Image

Image
Author:  skymax [ Thu Feb 11, 2010 12:36 pm ]
Post subject:  Re: Matt, any comment on diving AI hulls?
That wave-over-bow photo looks perfectly normal and is a sight I see often without any baggage anywhere, and not just downwind as any Sea-sailor will know.
My AI scoops out every time, that is what is important.

Look at the next photo of the red AI, see how the boat has a straight hull and little deck above the waterline, what else would you expect in swells or peaks?

The boat's fine, get over it or get another hobby.
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