Matt, any comment on diving AI hulls?

I would imagine that it is related to the angle of attack. If the bow stuffs enough to expose the broad surface area to the water flow... it could cause the bow to decelerate more quickly.

Fyi on ama volume... some of the limited volume (by design) is related to stress on the hull and rig. More volume and less ama dive adds to the stresses on crossbars, the mast and mast attachments to the hull. Added ama volumes will cause a ripple effect of other stress issues in the boat. Its not simple.

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Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

The bow plane/foil is slanted upward relative to the horizontal plane of the Adventure hull. As the hull dives below the wave, the oncoming pressure of the water against the bow plane forces the bow up.

Frankly, that is the reason I've had doubt that the spray shields (which appear to work wonderfully to reduce spray) would help to reduce diving. The spray shields might actually aggravate the situation. From the pictures I've seen, the plane of the shields may actually angle downward from the point of attachment on the bow. That is, the plane of the spray shields angles slightly downward, compared to the plane of the hull--this is just the opposite of the bow plane/foil. If that is true, then they might accellerate the diving once it has begun, just as the upward-angled bow plane/foil fights diving. And, unless they drained rapidly, they could hinder re-emergence of the buried bow. With a strong tailwind, one could be talking pitch poling now.

Keith

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2015 AI 2, 2014 Tandem

"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

"Less is more" Anon

Thanks Keith,
As I recall, Bob has a larger version of his sprayshields which he does not make available for fear they may cause a pitchpole in inexperienced hands. The version which he does make available, however, seems not to have that tendency. I've certainly never had such a problem.

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Polecat- Stop being a jackass and go enjoy your kayak. Yes, I said kayak, because that's what it is. Your complaining of hull design on the AI for sailing is like a Hobie 16 owner complaining about how poorly his boat handles when paddled.

Just another unhappy, entitled, everyone should do everything for me, American. Give it a rest.

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Mike K

Great answers Matt. Glad to see how this thread is developing.

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Polecat
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Hobie AI & WS Tempest 180 Pro
SW Gulf Coast: Sarasota to Keys

I'm not completely useless. I can always serve as a bad example.

Thanks for your response matt and i do appreciate your time. I don't not understand how rotomoulding a wave deflector would be costly when Finn and spirit both offer them for there yaks for what would be under $20 USD. Hobie seems to put a big mark up on all their accessories and i'm sure lots of people myself included would buy a good deflector for $50, which means hobie would still get more than 50% mark up.

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Whether you are into surfing, hunting, cycling or kayaking, you are never going to have the equipment that suits all conditions. But Hobie go pretty close with the AI in trying to cover as many bases as possible. And then, there is always someone that wants more ie: I'm sure there is some bloke is on a cycling forum complaining that his mountain bike should be redesigned so that it goes faster on the road. Quite frankly, I prefer to get wet and take a shorter distance through waves than stay dry and go up and over every wave. Personnal preferance I suppose.

Although this is an ad below, the AI hull is closer in design to the kayak on the left of screen. Have a look for yourself and decide which hull you prefer. Also, while you are watching, try to imagine how much movement a mast would have if it were attached to the kayak on the right.

http://www.youtube.com/watch?v=jWXXTAnNRoo

http://www.youtube.com/watch?v=9svtYPVm ... re=related

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Don't take life too seriously................it ain't permanent.

Slaughter,

That is what the first part of this thread was about. The AI hull is a low rocker hull. Low rocker hulls slice through waves. Low rockered kayak hulls, when loaded gear, supplies, and water, will tend to submarine. Boat designers employ large volume bows, wave deflectors/foils, and rockered hulls and outriggers to avoid the submarining while maintaining control in difficult situations.

The AI is a very versatile boat which meets a lot of needs. The suggestions made in this thread have been made in a constructive manner in hopes of improving on that design w/o diminishing its all-around usefulness. Your mountain biker has lots of options to alter the characteristics of his bike. Some suggestions made here would serve that purpose for the AI.

BTW, those videos were produced by Epic and show the Epic in a favorable light. You should read the comments after the videos for serious kayaker's impressions.

Personally, I would stay in camp before I would take on those waves in an AI. Those waves are capable of broaching and then flipping an AI.

Keith

_________________
2015 AI 2, 2014 Tandem

"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

"Less is more" Anon

Just got response from Spirit Paddle (Texas), who sells the wave deflector 'shufoy' bought for $20 AUS. The US price is $170 including shipping. Plus you will have to do a significant amount
of grinding, cutting and drilling to get it to fit.

wow, thats crazy just checked the finn website and theirs retail for $100 aud.

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Dave--there is money to be made here.

Keith

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2015 AI 2, 2014 Tandem

"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

"Less is more" Anon

Sorry if you thought I was hav'n a go mate. That wasn't my intention. I get what you mean with the hull design but I think, like others, that the best way to solve any submarining issues is to have an add-on rather than a hull reshape. For every advantage in a reshape, there is a trade off. An add-on deflector would have 1 extra advantage in that it is removable when not needed, but of course the disadvantage is attachement to the hull and remembering when you go to attach it that you left it back in the shed 500 miles away. I don't want the AI to loose the 'get wet' fun factor. Only when the hull takes submarining literally will I agree to a hull redesign.
Thanks for the thread Keith. I think we are all learning a bit from this one.

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Don't take life too seriously................it ain't permanent.

Where I sail my AI, a large inland shallow lake, the waves can quickly become pretty choppy.
I have had waves go from less than 1 ft high to over 5 ft, before I can sail a couple of
miles back to protected shore. The AI will quite often submarine. I would rather spend
a moderate amount of money to put an add-on wave deflector on the bow, than wait
and see if Hobie is going to re-design the AI hull. Two problems with that...I would
have to buy a whole new boat and wait for a new shaped hull, which may never be
produced.

If Hobie had a ready-made to fit add-on deflector, I don't see any need to remove it
when waves are small. Shufoy's deflector doesn't look that large or heavy, but did seem
to make a difference bringing the bow back up.

Since the Australians seem to be able to produce add-on wave deflectors for a small price...Hobie should be able to add it to their parts distribution if enough of us owners
express an interest. Look at the tramps...it didn't seem to take more than half a sailing
season for Hobie to start selling them. I think that when Hobie saw in the forum how many
of us began to make our own, they realized they were missing quite a few sales.

bEEN AWAY FOR A WEEK SO JUST READ THIS tHREAD, (bloody caps lock).

No design can be all things to all people, the "Diving" which could equally be called "Penetrating" is not a problem as the hull always scoops out even when I have been hit by tailwind mega-gusts.

If you expect to never have water over the bow or spray in your face you should not be Kayaking or Sailing.

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Fair Skies, Max.

Well said, Tidalwave. While I think modest reshaping of a amas would alleviate the problem, a bow foil properly designed would be of great help.

Skymax, if ANY of us were bothered by spray or water over the bow, we would not own an AI. My concern has been when you have an AI loaded to near max (360#) being driven before strong tailwinds, then, when that bow submarines I believe parts of your AI are under severe stress. There are others who like to go fast and race--I would think a submarining bow would be an undesirable trait. That is why some of us would like to see Hobie address the issue. There are solutions. You are welcome to sail your AI any way you wish.

Keith

_________________
2015 AI 2, 2014 Tandem

"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

"Less is more" Anon