I saw all those threads about broken hulls and decided to check if everything is ok with my boat and that is what I found. See attached photo. Nacra 6.0 hulls have dividers or supports walls in the hulls. The photo shows the support that is located in the area of the front beam in port hull.

How dangerous is the damage?

Anything that I can do to fix it?

I have port deck in that area but it is very hard to get to that spot.
Thanks
Kris

Ummmm...wow. Was there some major event that led to that damage? That looks pretty serious to me. That bulkhead is responsible for distributing the load from the main beam evenly to the hull which then carries the load to/from the shrouds and bow chain plates. It can experience both compression and tension depending on what the boat is doing. I'm no expert however. The question would be what kind of ultimate failure scenario would result and my guess would be that the hull would collapse with a potential for taking on water and/or dropping the mast.

It deffinately needs attention. However, since most the the structure is physically still there, I think that you may be able to get away with a patch. If you can get too both sides of that even better. Start out by mixing micro-bubbles, or silica powder to resin to make a thick filler compound, add your hardener, (or if epoxy even better, but mixing will have to be done quickly) If your using polyester, make it just a little hot as there is no daylight in there to help the catalyst. Then start with thin strips of clothover just the crack, and add layers getting progressivly bigger, untill you cover that whole biulkhead. Your going ot get messy doing this as I bet it'll be hard to manuver cloth down in there. Like I said if you can do this on both side much the better. Check it often for the resurgence of cracks, as this should happen before any failure.(Something that makes for a catastrophic instant failure after this procedure would likely do the same thing on a perfect hull) Hopefully you patche, combined with the large amount of bulkhead wich appears to still be intact will be able to dissapate and withstand the forces for quite some time. Another option might be to do the same thing with carbon fiber, it would be a lighter repair, but its possible that you want some flex here, I'm not that type of engineer so I'm not sure about that point.

Good luck, but do get some attention to that area.

I have no idea how this happened. The boat is 1997 and I got it about 2 months ago. Never hit anything.

Is there any way to separate the top portion of the hull from the rest of it ? The amount of space through deck port is not enough to stick my whole hand in it.

hmmmm, perhaps enlist the help of a small child or midget? My dad always used to say that that sort of thing (along with the kitchen dishes) was the reason that he had kids.

You may have to move up to a larger port. The other option is to cut open a large portion of the deck and glass it back in afterwards.

As far as deck ports are concerned, I've installed 6" portw between my main beam and dagger well. This was to thru bolt my jib car tracks that were pulling out of the hull.

As Jamie Diamond and others pinted out on another thread, it makes for great storage in dixtance races, etc.

You'd also have enough room to do an adequate repair.

My suggestion is that you enlarge to 6" ports first.

Yep it is serious. You need to fix this prior to going out again. It's better to do both sides but I would probably do one side very strong.

1. Cut a hole for a 6 inch port. Do not install the port until after the fix.
2. Sand the area to be fixed with 100 grit paper. About 6 inches on either side of the crack. Sand good so that your repair sticks. If the repair fails it most likely will fail because the repair doesn't bond to the material in the hull properly because it was not sanded enough or not clean enough (dust).
3. Clean the entire area of dust with Acetone or MEK.
4. Buy some West System Epoxy and carbon fiber. Cut into strips starting with about 3 inches wide then about 4 inches then 5 inches to cover the entire crack and extend past the crack a good 6 inches in all directions.
5. Mix the epoxy according to directions. Make sure you are doing this on a day that is neither too hot or too cold. Make sure the epoxy is not hot from sitting in a car or something. Perfect is about 70-80 degrees.
6. Use a disposable foam brush. Brush the area on the boat to be laid up. Put the the first layer of 3 inch strips down. Brush again. Put next layer down. Brush gain. .... Put last layer down. Brush again.

7. Let it sit for 24 hours. Check to make sure the epoxy is hard and has gone off.
8. Install the new deck port.

You can substitute A good weave glass and polyester resin. I would be very temped to do this. However I would use a few more layers to be sure it is strong. You definitely only need to do one side if you do the repair strong.

Mike Hill
Tiger #1520

Mike said whta I was trying to say, only much more clear. I would still recommend making some of that filler compound that I mentioned and filling in that crack before you start his precedure. The reason being that by filling in the crack, and effectively glueing with the filler, you elliminate the possibilty of the crack compressing and relaxing underneath your patch. This will prevent cracks in the patch, as well as help prevent the area where the patch adhere to the original bulkhead from failing.

I'm still waiting to here if anyone has some experience with carbon fiber in this sort of repiar, you' couldn't get pre-preg to workin there, but i think you could use tot cloth with epoxy resin. I just started learning to work with carbon cloth a little, and I'm stoked on the idea of using it for everyting I can. A freind built an RC pod glider out of it, and after watching him dive the plane into rocks without incuring any damage to the pod, I'm totally sold on using this stuff. Also, the supply off the stuff that was given to me by an ME proffessor has nearly run out, adn I want to try a larger project, anyonme know where to get some more cloth??

So, I'm not the only person to have the jib track pull out of the hull! Looked like the rivets were too short. I put the 6" port in behind the dagger trunk to thru-bolt the track. It's a great feeling to sail a new-to-you boat once and have to cut a hole in the deck!

Now I feel like I need to get a view forward to see the bulkhead. Anybody have any idea how the bulkhead crack could have developed?

http://www.aircraftspruce.com

The crack in the bulkhead looks serious, but it would help if we could see photographs of the ends of the crack. From the photograph there dosen't seem to be any loose fibers around the edges of the crack. The lack on loose fibers may mean it is a new crack, just happend, or its an old crack, but the bulkhead is not flexing. Also from the photograph, we cannot see how far the crack extends toward the hull. The bulkheads strength is in the outer 3" to 4" next to the hull. If the crack extends into this area, 3" to 4" next to the hull, and is showing loose fibers, the hull is flexing and needs repairing. It is quote common to see large holes in the center of bulkheads, these holes are there to reduce the bulkheads weight.
If the ends of the crack are showing rough fibers, the area is flexing under load and needs reparing, but if the ends are clean, it is most likly and old crack.

S Beach

As catamaran builders (and repairers) we have seen this type of damage many times. The usual cause is from the boat sitting on the beach and everyone and their dog thinking "what a great seat it is" and having 3, 4 or more people sitting on the hull at the smae time. with that sort of weight on the deck the hull is depressed the bottom of the hull can't go any where and the deck moves down ( it has to go some where to support the load) the result is that the bulk head is split as the walls of the hull around it move sideaways away from each other. The laminate of the bulkhead was never "loaded" to take forces in that direction (their load sailing is basically only compression) so it will split.
It is not a majour concern as by glassing it only on the visible side will satisfactorily support its "normal" sailing loads and even without anything being done to it, it will still take the normal sailing loads as they (the loads) are tending to "push" the bulkhead back into its normal shape. We have seen boats with this sort of damage that have sailed for years with it unaware of the damage with no majour problems. It has only been when they have seen it that they start to get "worried".

Is that damage on the inboard side of the hull?
If so, it could be from someone too heavy standing on it to right the boat after a capsize.
The damage seems to be the size and shape of a footprint.

Thank you for all your replies and helpful advices. I will ask my younger brother for help – his hand is much smaller.

Also, I found few internet sources that talked about similar damage and some of them suggested that it also might be caused by improper tension in shroud wires and forestay wire. How do you measure the tension in those? What is appropriate tension? My are vinyl coated so I can not use any gauge.

I found one more photo that shows that damage.

Thanks

Kris

The more I look at that, the more I think it was some sort of torsion on the hull resisted by the beam and (possibly loose) beam bolts that caused that. We can't see the deck in that picture, but that crack looks like it runs up inside of the outer beam strap bolts. It could be that at some time, a large and unusual sideways force was applied to the bottom of the hull, was countered by the beam attachment points, and lead to a high shear load in that bulkhead along which that crack developed. I doubt it's related to rig tension because you can tighten your rig all day long but the leeward shroud is going to flop around in a stiff breeze regardless (i.e. you're not going to apply more tension that sailing in heavy air would).

It probably doesn't have anything to do with this but do you have cradles or rollers on your trailer?