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PostPosted: Wed Feb 20, 2013 2:48 am 
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tonystott wrote:
Sorry, but I really think you are unrealistic in your expectations, for several reasons
1. The rotomolding process is by its nature, imprecise. Alignment of parts simply cannot be guaranteed to be perfect.
2. These vessels can travel through the water at relatively high speeds (20-30kmh), which increases the dynamic pressure of water against any of the seals.
3. Due to the very low freeboard, and the high probability of fire-hose strength airborne spray from the aka knuckles, the whole hull can be in an extremely wet environment for a lot of the time.
4. The necessity for 4 holes through the hull for rudder lines introduces the classic balancing act between watertightness and lack of friction - pick one.

While it is of course worthwhile to ensure that the seal of the front hatch is as effective as possible, especially due to the wave-piercing design of the bow, I believe that expecting the interior of the hull to remain bone-dry is a futile hope. I accept the need for some dry bags if I want to ensure anything I store in the hull remains dry, and I suspect you will increase enjoyment of your Island if you lower your expectations just a touch.


First, I love my AI and really don't need to increase enjoyment sailing it.

This video (from 3:19 to 3:44) gives a good picture of what to expect.

http://www.youtube.com/watch?v=ti1n_Ygz6cw

I don't think the front hatch design meet up to these conditions. As you say:

tonystott wrote:
2. These vessels can travel through the water at relatively high speeds (20-30kmh), which increases the dynamic pressure of water against any of the seals.
3. Due to the very low freeboard, and the high probability of fire-hose strength airborne spray from the aka knuckles, the whole hull can be in an extremely wet environment for a lot of the time.


You are right! And I think the front hatch should be designed to meet your statements.

About rudderlines, maybe a better solution is to let ALL that stuff be mounted OUTSIDE hull. You can still use tubes lowered in a deck ditch. But that is minor problem and could be free to owners creativity to fix.

br thomas


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PostPosted: Wed Feb 20, 2013 5:42 am 
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This is a very interesting thread. Thank you NOHUHU for sharing your testing methods and results. The problem seems quite evident and I'm wondering if something could be fabricated to lay on top of the front hatch to significantly reduce the water flow over the hatch. It would still be wet around the hatch but not as much flowing water. Although submarine mode throws that all out the window.

There's an aluminum V frame on the bow of my AI which gives me something to attach this "membrane" to so I may consider giving it a shot. I'm going on a 7 day AI cruse heavily loaded in 10 days and would like to minimize the amount of time spent pumping water out the hull.

I need to think about this more before heading out on the water today.

Something like this which is secured on the leading edge by packing tape:
Image

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PostPosted: Wed Feb 20, 2013 12:11 pm 
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I made up my own spray skirts. I designed them as a single piece of cloth which spans from one aka to the other. I used fiberglas rods as stiffeners along the bow sides, which prevents the cloth from moving up from the hatch. Water does not noticeably slide under the skirt.
Even slamming through fairly tall chop I have never had a noticeable amount of water in the bow. However the design does not allow access to the hatch while sailing.


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PostPosted: Thu Feb 21, 2013 5:31 pm 
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If I really get frustrated, I'll whip out my secret weapon.
Image

But first, I'm gonna replace the seal(s) with the new model and try a couple tricks that have been suggested by others.

For the record - I have the older style (glued) seal seen on the left here. About 1 yr old.

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PostPosted: Thu Feb 21, 2013 5:46 pm 
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Designer Duct tape. Cha Cha Cherry :lol: The supermodels will love that.

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Last edited by CaptnChaos on Sat Feb 23, 2013 3:37 am, edited 1 time in total.

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PostPosted: Fri Feb 22, 2013 5:01 pm 
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I was out in rough seas today and came to the conclusion that the cover over the front hatch was not a keeper for two reasons. Maybe it was my imagination but it seemed like when the water was washing over the deck, when it hit the blue foam, it picked up speed and really nailed me. And the second reason ... when I got back to the beach there was a half gallon of water in the boat.

Oh well, it was worth a try.

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PostPosted: Sat Feb 23, 2013 2:12 am 
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NOHUHU, this is an excellent thread on a very important subject. Thanks for the pressure test instruction.

For those who say you can't expect a dry hull in a pressure molded design, I say, you can expect to have a minimum of water egress, say a quart/liter, maybe 1.5 quart/liter max on a very difficult day sailing. What is a "difficult day sailing?" It is pretty simple. If you are out for 3-5 hrs and during that time bury the hull (waves flow over the front hatch cover) frequently, that can be called a dds (difficult day sailing.) If your boat is taking on 1-3 gal on a dds, you have a serious leak. An unacceptable leak.

As has been suggested here, a serious leak can probably, say 9 times out of 10, be traced to the front hatch. I suggested a simple, DIY, front hatch seal made from pipe insulation. http://www.hobiecat.com/forums/viewtopic.php?f=69&t=46308&start=0

While I did not doubt that my DIY pipe insulation would seal the hatch, there was reasonable doubt about durability. Well, I have just completed my first serious test--a 6-day, heavily loaded AI, Everglades camping trip. 3 days were very dds. The bottom line: (1) no water, zero, leaked through the front hatch, and (2) after 6 days out plus leaving the hatch bungeed the night before and the night after the trip, the DIY seal looks like new.

It cost 7 US$ and a few minutes installation to give this seal a try. Those of you with front hatch leak problems should consider it.

Keith

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I sail: Biscayne Bay, Everglades to Cape Romano, Ft Desoto, Cedar Key

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PostPosted: Sat Feb 23, 2013 2:49 am 
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+1. Thanks Keith. Good advice. Nice of you to stress test a solution for us. :lol:

Serious water requires a serious hatch seal. And a pump.

I'm gonna noodle with a different approach to see how it works out. But there's plenty of room here for anyone to post their leak test results and cures.

I hoping to find another fix that will be as dead simple, cheap and effective as yours.


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PostPosted: Sat Feb 23, 2013 3:59 am 
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Hi Keith, I was thinking about you yesterday and wondering how you did on your trip as well as how that seal worked out for you. We had a serious front come through this area last week so I thought you might be in for a couple "dds" 's : .

Sounds like your seal turned out to quite durable.

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PostPosted: Sat Feb 23, 2013 5:04 am 
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Keith, thanks for testing that seal. My point about it being unreasonable to expect a dry boat, was made on the premise that even with a good front hatch seal, the odd water is going to find itself inside, and with no "bilge" for the water to "hide", even a cup full is going to wet things stored inside.

I know that every time I open one of my twist and seal hatches, half an eggcup of water sitting in the handle area goes inside.

I seriously doubt any of you would ever expect to be able to leave something like a toilet roll inside the hull and expect it not to become a soggy mess, unless you put it is a drybag first.

I agree with Keith - it only becomes a worry when the volume of water starts to exceed a pint or two from a dds...

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PostPosted: Sat Feb 23, 2013 6:36 am 
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tonystott wrote:
I agree with Keith - it only becomes a worry when the volume of water starts to exceed a pint or two from a dds...


Maybe I have some kind of record...

viewtopic.php?f=75&t=44782

...leaking about 10 gallons in 5 hours :( :( :(

br thomas


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PostPosted: Sat Feb 23, 2013 10:11 am 
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Guys:
I have the latest seal design on my new TI with two of the new type gaskets. On a DD's day I will get a small amount of water into the hull, at the most a half a cup, I typically lay a beach towel in the bottom of the hull, and it soaks up the stray water, and keeps my gear from rattling around.

Kal-P-Dal's problem, which was unique ( a defective hull), should have been addressed by Hobie as a separate kind of unrelated not typical issue.

The new gasket seal system is a huge improvement over any of the older designs. I am assuming if you have an older AI/TI or Hobie kayak you can go to your dealer and get the new improved gasket material, and the boat can be retrofitted. Anyone having leakage (more than a very small amount), that should be your first step.

I agree that it would be expecting too much to expect the hull not to leak at all (too many points of entry), especially in open sea conditions.

For those of you who have already upgraded to the newest Hobie gaskets that need extra protection, or are planning a long expedition ( like Jim) read on.

I looked at the design on my TI again today to see if I can improve the gasket even more (with a side seal vs a compression seal (as I mentioned earlier in this thread)), and yes indeed there might be a simple fix ( without needing duct tape LOL).
I took about a 3 ft piece of 5/16 dia soft PVC (vinyl) hose and connected to itself in a loop, I then placed it over the outside rim of the hatch opening (on the hull). Because the walls are angled it sits not on the very bottom, but clings just below the bead of the seal. You need to cut it a little short so is stretches slightly. Now when you put the hatch cover on it slides past the bead in the lid (pushing the outside bead out of the way as they pass each other). The lid then snaps down, and you can put the bungy's on. You can see the outer seal is pushed out slightly when down so I am assuming the tubing is pinched on the sides, hopefully giving us the side seal that we are trying to achieve. If the outside seal does not go all the way to the bottom surface, this means the diameter of your tubing is too large go to the next size small tubing (this happened to be on the first attempt). The tubing is very inexpensive (about $2-$3 bucks for 6 ft at Home Depot)
I put the boat in the pool, jumped on the front and did a few alligator rolls with no apparent leakage ( by now all my neighbors expect this type of crazy stuff from me, so it's no shock to them).
Right now I'm in the process of designing and fabricating all new sails for my TI (again), so I can't test out in real conditions till I get my boat back together hopefully next month.
It is also very important to keep the twist and stow hatch seals clean and lubricated to insure a good seal ( I use armorall on mine).

The steering line tubes (on the inside of the hull) need to be up as high as possible against the underside of the hull (inside the hull), this creates a bubble of air above the waterline that prevents water from coming inside the hull through the tubes. I know on my TI's when it was really loaded down at max weight with the motor, scuba tanks, two passengers, etc if those tubes inside the hull are not above the waterline, water can pour into the boat. I noticed this on one of my older TI's which had been converted from the old twist and stow rudder system (installed as per their video). I had to go back in an redo the conversion to get the tubes higher because of water intrusion.

My opinion is a small bilge pump should be stored in any SOT kayak whenever you go out. Once on our TI we were running rapids (in kayak mode) on the Huron river (Ann Arbor MI), my wife had the hatch open (getting her camera) as we hit a rock lost control and tipped over. our hull filled with water (very quickly), as did the sit inside kayak that her sister was driving (we ran into each other). We had no pump (duh), and it took quite a while to get all that water out of both boats. Still had a lot of fun though.

Hope this helps
Bob


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PostPosted: Sat Feb 23, 2013 11:06 am 
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Kal-P-Dal wrote:
tonystott wrote:
I agree with Keith - it only becomes a worry when the volume of water starts to exceed a pint or two from a dds...


Maybe I have some kind of record...

viewtopic.php?f=75&t=44782

...leaking about 10 gallons in 5 hours :( :( :(

br thomas

Thomas, surely Hobie has now sorted out your problem under warranty? I think everyone agreed that the problem you have/had with your hull was extremely abnormal, confirmed by Hobie's decision to correct it under warranty.

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2012 Tandem Island "SIC EM"
www.scenefromabove.com.au


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PostPosted: Sat Feb 23, 2013 11:59 am 
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Bob, could you please post a picture of your new seal and how it's installed.

I bought a piece of 4' of 5/16" ID vinyl tubing from Lowes. My AI has the new Hobie seal that goes on the hatch. However, I've been reluctant to replace the hatch seal that sits on the hull as the new replacement seal just doesn't look right for it and I don't want to shake things up too much right now.

Thanks,

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PostPosted: Sat Feb 23, 2013 12:15 pm 
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Here is a picture of my DIY seal after 6-day camp trip--4 hrs or more on the water w/ fully loaded AI every day.
Image

If you check the original pictures when the seal was installed on Jan 20, you will see that the seal is effectively unchanged and still working fine. http://www.hobiecat.com/forums/viewtopic.php?f=69&t=46308&start=0

Remember, this DIY seal fits right over the Hobie original seal--easy.

Keith

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I sail: Biscayne Bay, Everglades to Cape Romano, Ft Desoto, Cedar Key

"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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