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PostPosted: Mon Feb 18, 2013 11:36 pm 
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Location: Kailua 96734
Has your Hobie been drinking too much water lately? Getting a gallon or more after a hard sail? An easy sail?

Here's an easy/useful approach to checking your hull and all its fittings for signs of water penetration. It clearly showed the weak points in my particular AI hull, and I think the results are typical of all Adventures and Tandems.

Start by putting the hull up on sawhorses (keel down). Locate the smallest vacuum you can find, provided it can still be used in reverse mode to blow air. (Leaf blowers are not recommended!) :o

A low pressure/high volume model works best, such as the ones designed to blow up air mattresses, kites, etc.

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Or a battery operated one like I use for all my wilderness camping gear.

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This time, I used a small handheld "shark" vacuum and collected the exhaust output into a flex hose with a tapered reducer:

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This fits snugly into the AI's side drain.

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Whatever you use, you'll need it to fit into the bung hole on your particular ride. The TI as I recall has only a redunculously tiny drain in the keel... :roll:

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Whereas, the AI has both small bottom and larger side ports.
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Our friend Batman recommends an adapted crevice tool to feed the drain port. He even uses a footswitch to operate his shop vac, cuz "it's more efficient" (and it gives him the illusion of being "in control").

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(Yes, you can check the Amas for leaks too. But keep the pressure LOW, or use a perforated hose or tubing).

Begin by closing all the hatches. Fill a spray bottle with warm water and a couple shots of dishwashing liquid. Shake it well and start applying the soapy water to the hull and fittings. Slowly work from one end of her to the other. Don't be shy. She likes it that way...

I started at the stern and forced some soap into rudder line tubes. I got immediate results.

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There was definitely water penetrating from my rear lines, possibly quite a bit as the water rushes by there all day, building pressure and looking for a place to go.

On to the rear hatch... I let the soapy liquid build up around the hatches. They were cleaned first for this test, with no sand or lube present. RESULTS: Both were perfectly airtight.

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The foam you see here is from mixing, not from any leaks. Those tend to produce larger bubbles that build on each other or blow liquid away from the crevice…

I cracked the round hatches open and filled them with soap and resealed them. They did not leak at all! Not the hatch O-rings nor the flanges that hold them in place. Nice to know. (If you do find a problem, your first hint of it might be unusual sounds. You can locate some serious leaks by a hissing or whistling sound).

Moving along, I checked all the scuppers, seat attachments, blocks, cleats, Aka mounts, padeye fittings, side handles, tiller etc. All were fine.

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I spent extra time inspecting the Mirage drive well and its clamps. No problems there, (exhale).

(You can install the Mdrives and have someone pedal them if you want, but without the drives loaded with water pressure, I'm not sure you'll find any lurking cracks. But try rocking them, at least).

The bow hatch, however, was a hole different matter! :roll: The seal there could best be described as pathetic.

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I noted that a large volume of air was escaping there from multiple points between the hatch seals, (and even from around the hard plastic moldings that attach the upper and lower seals to the kayak).

Some of the worst areas are obvious in these pictures.

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I am most concerned now about the lower side wells where water is supposed to drain away from the hatch, but the sucking seems to be greatest.

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Here's a short video showing the areas of concern:



CONCLUSIONS
Most of all the front hatch seal of my 2011 hull was VERY leaky. I suspect it's the source of most of my 1-3 gallons of hull water after a juicy sail, and it's going to require attention. I'm already exploring a couple of the crafty ideas discussed in recent threads by the brain trust here at our forum.

In comparison, the round 8" hatches were VERY impressive. I will never again worry about this area being constantly underwater as I sail.

So my hull is probably leaking 75% from the bow hatch and 25% from the rudder lines and other sundry points. (A few good sails with some dry towels at each end can help test this conclusion).

You can keep all this in mind for reference as you conduct your own tests, on and off the water.

Cheers! Or as we like to say here, "Suck um up, Brah!"

NOHUHU


Last edited by NOHUHU on Tue Oct 29, 2013 2:50 pm, edited 1 time in total.

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PostPosted: Tue Feb 19, 2013 1:38 am 
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Very interesting! Thanks for the post.

No leaks at the rudder up/down line openings?

BTW, I have read before that it is very hard to use this method to detect leaks at the front hatch. It is too big and the air pressure is lifting the hatch cover. But I agree with your conclusion. Front hatch is certainly leaking.

br
thomas


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PostPosted: Tue Feb 19, 2013 8:52 am 
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Location: Palm City, Florida
NOHUHU,

Excellent instructional post and video. So simple and easy to do. Given the recent reported problems concerning leaks and finding them, this ought to be a standard practice for us and Hobie.

From: viewtopic.php?f=75&t=46521
mmiller wrote:
I know they do visual and soapy water tests, all before assembly. Makes the most sense, so post-assembly issues are harder to find. You can't take a brand new boat and spray soap all over the finished accessories.
Why not Matt?

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2014 Tandem Island


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 Post subject: LEAK TESTING HATCH SEAL
PostPosted: Tue Feb 19, 2013 9:00 am 
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Location: CLEARWATER, MN
Using positive interior air pressure to test the foreward hatch may not work correctly depending on the seal design. A seal with ->/ may effectively stop water leakage but if the air pressure is /<- the air may move by the seal. Since the hatch is designed to stop fluids from leaking into the hull...you may wish to create a vacuum in the hull and see if the soap solution is being sucked into the hull.


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PostPosted: Tue Feb 19, 2013 10:04 am 
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Location: Maui, Hawaii
Yep, the front hatch is a problem fully testing this way, but it still can give some idea of possible problems to further check.

It also shows one of the problems with a well sealed flexible hull. When in waves, especially at sailing speed, the hull flexes in, letting a little air out on each wave, but then it 'breaths back in' possibly sucking water into the hull. This can happen on every wave, acting like a small but steady pump! We've often talked of where we could add a snorkel above deck to let the hull breath without sucking in water.

When we sail as a group, we often compare how much water we get in each hull, both as an indicator of a problem to look for in a specific hull (much more water) or as a general 'fun' index of what we just went through! (everybody with similar amounts of water) :lol: The Islands (especially the AI) ARE wet rides! 8)

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PostPosted: Tue Feb 19, 2013 10:06 am 
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I'm fairly new to the Islands. Is that amount of leaking normal for the rudder exit tubes? If not, does anybody have any suggestions on remediation short of replacing the tubes?


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PostPosted: Tue Feb 19, 2013 10:55 am 
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I agree with Kayakingbob's view... being a wet ride, I expect to find more water inside my 2012 TI after an exciting ride, but I usually empty out under a cup full after a 4-6 hours of flattish water sailing.

And Gary, I would never worry about the amount of water which could enter through the rudder exit tubes, the volume is going to be insignificant

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www.scenefromabove.com.au


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PostPosted: Tue Feb 19, 2013 11:50 am 
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tonystott wrote:
I agree with Kayakingbob's view... being a wet ride, I expect to find more water inside my 2012 TI after an exciting ride, but I usually empty out under a cup full after a 4-6 hours of flattish water sailing.

Eh? No, "being a wet ride", I expect to get myself wet , not my gear inside the hull.

tonystott wrote:
And Gary, I would never worry about the amount of water which could enter through the rudder exit tubes, the volume is going to be insignificant

No again! Well if you have very leaking front hatch, ok, then you should not worry about the rudder exit tubes. You have other things to get worried about. But you will get enough water thru these tubes to get your gear wet inside hull if you don't do anything about them. Which, in fact, is possible.

br thomas


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PostPosted: Tue Feb 19, 2013 12:00 pm 
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Interesting post and good info to know.
I've water tested my AI with a hose on low pressure - particularly around the front hatch and couldn't make it leak. Like everyone else I drain a litre or 2 after a 6 hour sail, not bad I guess.

Thanks Nohuhu


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PostPosted: Tue Feb 19, 2013 3:05 pm 
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Location: Kailua 96734
Thanks for the responses guys.

As they say, "your drainage my vary". This thread is not an indictment of Hobies hatch design or factory practices, but a search for obvious points of seal weakness on my boat. (The main reason was to rule out any unknown cracks or holes below the waterline). Everyone should try it.

Wave and KBob, yes this is a "reverse pressure" test and the only realistic one we have. Anyone that wants to take the boat through a brushless carwash while jumping up and down on the hull can be my guest. Please bring along the gopro!

I would point out that these hatches are not 1-way valves. There is an extra lip for water to travel across, but the area beneath it is basically a channel that's always full of water.

I'm in agreement with Bob; that under sail, these boats are like giant syringes. They constantly inhale and exhale through any crevice they can find. Maintaining slight positive pressure would be ideal. (Batman actually installed a Eustachian tube in the stern of his bat boat to retard this action - I'll get a pict if I can).

Note that I test with the bungees on and the seals compressed, as designed. There are always more pounds of pressure exerted on top of the hatch than a vacuum can ever overcome. (You would blow the seal first, so I advise folks to be careful here or you'll just create new problems with the vacuum).

So when the boat is at rest, and I see major gaps expectorating water/suds from my bow's 2 overlapping seals, I'm confident that water can be pushed or sucked through those gaps as well. Whether it's from a constant casual "sipping" effect or from guzzling while burying the nose a downwind submarine chase, I do not yet know. The video shows the potential points of entry clearly.

As far as penetration from the AI rudder lines, I may well be underestimating this. Sitting high on the Hakas allows me to monitor my rudder and wake, in all kinds of conditions. (I've begun to check it just as much as I do the telltails - and I adjust my hiking position to please the rudder). In my playground, you can't keep that area dry (although the TI is a bit dryer) but I try to prevent it from being inundated all the time.

Gary, I'm not ready to call this area insignificant, in terms of leaks. Besides the pinholes, the steering and up/down lines actually provide a path for the water to travel. Water loves to do that. The good news is, it far more practical to test this area with a full submerge or high-pressure spray test.

Looking forward to your future leak test results, and carwash videos. :lol:


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PostPosted: Tue Feb 19, 2013 9:09 pm 
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I have an observation about front hatch leakage on the ti. As everyone knows I have extra sails on my TI and this puts a little more strain on things. Especially the bow. Just sailing in regular conditions if you stare at the bow, you can see it flexes up and down, and also back and forth. Mostly caused by the weakness created by the giant hatch opening. Why mention all this.... Well the hatch seals are compression seals ( held down by the buggy straps). As the boat moves through the waves gaps in the gasket open up and allow water in. If someone were to design a side sealing gasket for the hatch ( vs compression) I have a feeling the water seal on the hatch would be as good as the round twist and stow hatches (which are side seal).
I have an aluminum bow sprit on my TI which braces the entire bow, and prevents the bow from moving around. Since installing the bow sprit I have very little water in the hull, even after pretty ruff sailing. That's what got me thinking about how to possibly improve the hatch seal design ( Unfortunately I'm an engineer and think about this kind of crap)
For what It's worth.
Bob


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PostPosted: Tue Feb 19, 2013 9:35 pm 
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If you watch closely, you may see the TI bow bending slightly, side to side (twisting) in big wind/waves. You don't notice any fore/aft deflection so much, from the cockpit.

That TI sail is a hell of a thing.

At the same time, the removable hatch top does not bend, but goes through heating and cooling cycles.


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PostPosted: Tue Feb 19, 2013 11:59 pm 
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Kal-P-Dal wrote:
Eh? No, "being a wet ride", I expect to get myself wet , not my gear inside the hull.

tonystott wrote:
And Gary, I would never worry about the amount of water which could enter through the rudder exit tubes, the volume is going to be insignificant

No again! Well if you have very leaking front hatch, ok, then you should not worry about the rudder exit tubes. You have other things to get worried about. But you will get enough water thru these tubes to get your gear wet inside hull if you don't do anything about them. Which, in fact, is possible.

br thomas

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.

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www.scenefromabove.com.au


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PostPosted: Wed Feb 20, 2013 2:18 am 
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Typical day on the TI, and this is just the front! (B4 adding KBobs skirts).

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PostPosted: Wed Feb 20, 2013 2:20 am 
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REALLY good day on the TI. See the difference? :lol:

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