I've had my hobie cat 16 for a long time and I never got around to maintaining the hull bottoms. Now after beaching it all the time and whatnot, they have worn down and one of them is leaking. I've read alot about different methods of repairing the hull bottoms but I'm not sure which one applies to my situation. I'm including a picture of one of the leaking spots on the hull that leaks with this post, then the next will be the other leaking spot, and the third will be a picture of the other hull, which is not leaking but still worn down.

here's the second leak spot. it's not quite as bad as teh first.

this is the bottom hull. it doens't leak yet, it looks like the previous owners put something on it.

Definately needs some work. There are a number of posts on bottom jobs; do a search to get some ideas and then we'd be happy to answer specific questions.

so with the boat over on it's side I couldn't really get to anything so I went ahead and took down the mast and flipped it all the way upside down. Since no matter what I do the are where i'm gonna be applying stuff is gonna have to be sanded, i went ahead and did that. On the damaged hul while I was sanding I hit a few weak spots and one crack. The crack is pretty thin but some of the material around it it damaged as well. I have read about sticking a hacksaw into the crack and using it to cut away the damaged material, but I'm reluctant to make the thing any bigger. Also, there is alot of controversy about using epoxy vs marine tex vs polyester resin and whatnot. I think i'm pretty sure for this one I wanna actually add some chopped fiber material though. In all the posts I have read people usually talk about mixing chopped fiber with something else (like polyester resin) but when I went to west marine to look around the only thing I could find with chopped fiber material was already in some kind of liquid. Anyway, I basically want to repair it with something that will hold up structurally, but will also be waterproof (some of the fiberglass structural fillers were not waterproof). What exactly should I use for this?

Aaronhoy,

Look a few posts down for "Hull Condition". I posted a detailed step-by-step on how to fix this very problem. As for the chopped glass,yes find some and mix it into the resin to fill some of the voids. However, this should not be your first step, nor should you neglect to use some fiberglass cloth in your repair. As for the resin controversy, go with epoxy for sure. This will (by far) adhere the best to the damaged area. For this job, polyester resin is simply a poor choice. See the post as I suggested. If you have any other questions email me at dpcarey@golden.net and I will help you out. In the mean-time,dry those hulls out and keep the rain off of them until the repair is done.

Dave

wait, so the stuff I found that was some chemical with fiber in it is what your talking about when you say chopped fiber? or will this be literally JUST chopped fiber material?

There are some products available with glass fibers already mixed in. However, I have always prefered buying the chopped (usually called "milled", not "chopped") fiberglass separately and mixing it with the resin of my choice. That way you can completely control the viscosity of your mixed product. This is important for different applications at different temperatures. Also, and perhaps most important, the pre-mixed stuff that I have seen has been mixed with polyester or vinylester resin. And although I generally like the vinylester resins, I do not like polyester for structural repairs. For structural repair, epoxy is the best way to go. Vinylester is nice for smaller stuff (chips, dents, dings and scratches) especially if you are on a tight budget. Also, the chopped (milled) glass, when mixed thick with resin, can be a little difficult to work with and doesn`t always settle out smoothly. You would find it easier to use fumed silica or microballoons as your additive to the resin for filling voids. Then use straight resin and glass cloth to build up your repair.

Dave

ok, i need all of your guys' expert advice here... i just bought my boat and soon found out that i have a leaky hull, i first used marine tex on the bottom of the hulls (they'd seen better days...) and it still leaked, then i redid the silicone on the gudgeons and drain plug... and it still leaks... where could water possibly be getting in??? and how can i fix it?

I dont know that much about fixing the bottoms of the hulls, thats why I posted this thread. (although I think i finally figured out everything I need to do, thanks a lot guys) But anyway, as far as other leaks, as has been mentioned in other threads one good way is to cover the hull in soapy water and run air in through the drainplug. I actually took an old drainplug and attatched a valve to it so I can hook it up to an air source. If the hull leaks then you shuoldn't run a danger of putting too much pressure in it, but keep an eye on the pressure anyway just to be safe. The places where the soapy water bubbles are the leaks. Suspected places are the bottoms of the hulls, the drainplug seals, the rudder assembly attatchments, the deck/hull joint, and the points where the 4 posts that support the frame go into the hulls. Supposedly once you get everything sealed right the hull will actually hold a little bit of pressure and you will hear a pressure gradient equalizing everytime you take out the drainplugs after sailing. My hulls have never been that well sealed though, so maybe you should get more advice from some of the mose experienced people here.

I would definitely not use any pressure beyond what a vacuum cleaner can generate. Besides the hulls are vented in the pylons and there should never be any pressure build up. If you pressurize with a vacuum cleaner like a shop vac in blow mode you should have enough volume of air flow to generate a pressure enough to find bubbles in your soap solution. Whatever you do, don't connect any compressed air to that valve you installed in a plug. Assuming a hull is 16' long and averages 1.5' high, a 1 psi pressure would cause a force trying to pull the hull apart of over 26,000 lbs. A vacuum cleaner generates pressure in inches of water, maybe 3 or 4" where 1 psi is equal to over 2' of water column.

will a hair drier work well?

thanks for the concern but I already thought about that. I wouldn't want to make even MORE leaks :P. Anywya about your fix, you mean this guy had resin and stuff with him at the beach and put it on immedately? That sounds kinda odd. I'm being carefull with mine, I have the mast off and the boat upside down so I cant sand it properly and everything.

Fellas,

Careful with pressure. I agree with a vacuum cleaner blower approach. However, it is my understanding the the H16 hull is not a true "air-seal" and pressure is supposed to equalize through the foam plug in the pylons. Therefore, you should not be hearing a swoosh of air when the drain plug is released. Perhaps someone else can chime in on this.

Also, if you can`t find the leaks, look very closely at the sanded ridge where the hull bottoms mate with the hull caps. ie. this is the relatively flat and sharp ridge you get your fingers under when lifting a hull. You will find many defects along this ridge. They resemble little pits and holes. Some of these are air-bubbles formed in construction and are unpreventable for the most part. Water can leak through some of these. I was able to pass fluid out from the hulls through some of them by rolling the hulls (slowly) across the saw-horses I had placed them on during restoration. I found that I was unable to fully discern ALL of pits which leaked from those that did not. As a result, I used a small amount of polyester resin mixed with a small portion of microballoons (to prevent running) and plugged all the pits I could find. It took me about 20 minutes to do this with the hulls positioned upside down. It would be much trickier with the boat assembled but certainly possible. I imagine there are several other approaches and sealing methods to this problem as well.


Dave

To answer the question about a hair dryer, it would not generate enough pressure or volume to do anything. The vents in the pylons would probably flow all the air the hair dryer would produce.

I agree that there should not be any pressure differential noticed when you remove a drain plug. If the hulls weren't vented you could not drain water out of the hulls under normal conditions.

About the repair on the beach that I described in the private message, the fellow who fixed my hull had a business of several Hobies that took people out for rides. He maintained his boats and had all the materials he needed to fix mine.

Howard

yeah, i've never had my hulls make the air release noise either, that's just what i've heard other people say. In theory yes in order for water to drain out of the plug most efficiently there needs to be air comming in from somewhere else. However if seems like if your hull was so well sealed that pressure was equalizing then it would never take on enough water for this to be an issue and the little bit of water if you ever took any on would still drain out in a fairly short time. With this taken into consideration, do you think it's a bad idea to try to seal above the pylons?

Aaronhoy,

I am a little uncertain regarding this part of your question:

"if your hull was so well sealed that pressure was equalizing then it would never take on enough water for this to be an issue".

But, since I have the time today, I will try and cover all the obvious angles on this.

With regard to a perfectly sealed hull being unable to take on any water, I would have to say you are perfectly correct. However, as ambient temperatures rise and fall and the internal temperature of your hulls change, you can expect significant changes with the internal pressures of the hulls as well. These could be greatly enhanced or inhibited by the effects of cool water or the radiant effects hot sunshine. Those experiencing the aforementioned "swoosh" are subject to this situation. Although I cannot comment on the particular strength of the H16, I can say this could be very bad. It certainly could accelerate a delamination process (especially in a cored layup construction) and possibly even crack open a hull. The concern over a "perfectly sealed" hull then becomes an issue of damage from pressure as opposed to water.

I believe the Hobie techs could address this much better than I can, but it seems pretty straight forward to me. If the architechs and builders of the hull wanted it truly air-tight, they could have done it in the factory with relative ease. The real trick appears to be how does one significantly minimize water accumulation while maintaining good pressure equalization...again, not a tough thing to do. This is even easier than creating an air-tight hull. But, sealing the pylons (vents) would not be a good idea at all - in my opinion. If you are trying to find some special point where the hulls just barely leak air (equalize) yet somehow completely inhibit water intrusion, I would have to say it is not a realistic goal. The best you can hope for is to plug all leak points on the fiberglass hull itself and be sure that the foam plugs in the pylon are in good firm condition so that they cannot simply act as funnels for water to enter the hulls.


Dave

I recently found some small air leaks by presurising the hull. All it took were 5 or so large breaths blown into the bung holes. This also allows one to hear the fine pitched sound of air leaking as you build up the pressure. It's probably easier too...

Clint,

Nice low tech approach! Always worth a try! However, I am surprised by some of the difficulties people are experienceing here. The leak points should be relatively easy to find if you know where to look.

As I have been thinking about it, I have a suspicion some of these mystery leaks MAY be occurring below the waterline at the sites of previous repairs. If sailors are not using the proper process or materials in their patch work, then leaks may still occur. This is why I have repeatedly posted that simply slapping on some type of filler, or cloth and resin, may not do the trick (at least not for very long) on anything but the smallest repairs. I also think some might be omitting a proper cleaning process and/or an initial sealer application of thin resin (without fillers). Only after these steps can resin fillers and/or lamination be applied with any confidence.

If one does not follow these steps, it almost guarantees eventual seepage through previous repairs - especially along an edge like the bottom of the Hobie hull.

People who work with fiberglass understand these particular issues well - it goes with the territory. For everyone else, it is a matter of finding (and trusting) good information.


Dave

yeah, that's what i'm planning on doing, I was gonna apply a thin coat of resin over the entire damaged area to let it seep in anywhere that might leak water and then start applying sheets of woven fibgerglass. Shouldn't this ensure a good seal?