Yes, you can add inspection ports, I just wouldn't put one forward of the main beam.

My 1984 nacra 5.0 has no inspection ports, pretty sure it is solid glass based on the thud the hull gives and if I push the side the hull will flex a little. I looked at a 1984 5.7 with inspection ports which was solid fiberglass with stringers. An inspection port would be nice, but I think I would only put one in if I really needed it. Just go look at it and look closely where all fittings are attached to the hulls.

so yalls take is that if the hulls look fine, and have a slight flex, it should be ok?

That's good advice. Just look for any cracking gel coat (some will be normal - a lot will indicate a structural problem). If the hulls are not full of obvious sags and dents, then the boat is probably pretty solid.

are these stringers?
http://www.flickr.com/photos/teamseacats/440875302/in/set-72057594056084945/

hmm ok jake, anything else to look at?
And how ironic! I was googling around, and posted the link above, then I just noticed your sig is for the site, I take it that's your site.
Very nice boat jake, you obviously know how to do alot of work on it <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Austin... you can contact Jim Casto, he's a NACRA guy in Austin.

Look around on the TX catamaran sites:
www.texascitydike.com (houston)
http://catamaran.ws/home.asp (TX general)

hah...no. No stringers in there (You usually don't see stringers with foam core construction - just an occasional sub-deck...but that's another topic). That is a leaky and loose shroud plate shown from the inside of a Nacra 20 hull. The barely visible vertical part on the right is the leading edge of the daggerboard well and the tube is a through-hull tube for the trapeze bunji. The bolts you see are bolts holding the spinnaker sheet block to the deck through a reinforcement plate in the deck. I detailed the repair I did on that last weekend on the teamseacats website and it involved pressurizing a cup of epoxy and forcing it into the hull.

ya Jake, I read about the repair, didn't quite understand it though.
Just curious, how many cats do you have? Whats your favorite?

Finally, is the entire f-18 hull made out of fiberglass? I don't understand why nacras etc (where the tramp is not raised and goes directly to the hulls), why can they take so much more force than the h 16 hulls? For example, NEVER let anyone stand on your h16 hulls, that has very very dire consequences <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />

I own one - the Nacra F18. The Blue Nacra 20 is owned by my Team Seacats teammate, Frank Moore, but I keep it at my house and do the maintenance on it.

I wouldn't say that you can't stand an H16 hull - it's just that over the years, some of them have become soft. That can be caused by a lot of things other than standing on the hulls and nearly all catamarans can suffer the same fate if not maintained properly.

Hobie has several designs on which the trampoline connects to the hull in a similar manner - the Hobie 18 for instance. It's just all about what the boat is designed to do.

My favorite boat? Anything with two hulls. I've owned a Nacra 5.2, a Nacra 6.0, a Hobie 18, and Nacra F18. I've sailed extensively on Nacra 20s, Hobie Tigers, and a little on the new AHPC Capricorns and the new Nacra Infusion. If forced to choose one out of those, I suppose I would probably choose a Nacra 20 but it would be a narrow margin.

What maintenance can specifically be done to stop a hull from becoming soft? I always tought it had less to do with the maintenance than what cyclic loads the laminate see, how the laminate is done, eventual delamination between core and laminate and finally, how you treat the boat when using it. E.g, what loads do you put on it when sailing, do you walk on your knees on the decks etc. With maintenance I think more of polishing the hulls, checking and replacing worn equipment etc.
Chopped strand mat is know to be worse than woven cloth with regards to osmosis, so drying out your boat is an especially good move if it is buildt with CSM (it's a good move anyway), so that can be put under the maintenance label. But what other maintenance can be done to stop a glass/laminate hull from becoming soft, and why?

I would say keeping it dry would be the top of the list. Freeze and thaw cycles on wet fiberglass has to be hard on it. Polyester (and vinyl-ester) resins are not "waterproof" and if left submerged, will eventually allow water to permeate - so a wet freeze can be a big deal. Even just leaving a little bit of water inside the hull dramatically increases the humidity inside the hull leading to constant moisture exposure from the inside. Keep 'em dry and fix any soft spots immediately (because they'll migrate and quickly deteriorate).

Here is a link to a photo showing the stringers in a N5.2 (third set of pictures down the page).
Stringers

Best regards,
Mike

old thread but for anyone searching have attached a good pic of inside a 1982 solid glass nacra 5.2 hull

most of the pic is the forward bulkhead, scrubed clean to check for cracks
to the left is the side of the hull, you can see 2 stringers,
with your fingers try to see if they move at all. movement is BAD
the 2 screws at the top are main beam hold down screws
the rectangular angled section at the top is actually the 1/4 curve that supports the alloy tramp beam
at the very top is the inside of the inspection port, you can see the rivets holding it on to the top of the deck
the worn white cloth edge is my shirtsleeve and above that is my hairy wrist ;-)

eric e

erice
Your picture shows the basic weakness of the boat. The builder used chopped strand mat to fabricate the 1/2 tube stringers… and as a portion of the tabbing for the bulkheads installation. These areas should have been glassed with cloth, ideally oriented +45 degrees -45 degrees. Chopped strand mat is cheaper, easier to work with in tight curved areas, builds up stiffness quickly, but is known to facture and delaminate in this type of application… and it holds a considerably greater amount of resin (weight) without a comparable increase in strength when compared to cloth.

So when those that keep harping on the fact that a heavier boat is better (stronger) that definitely is not always the case. Here is a perfect example of the misuse of materials in the design and construction of a catamaran. I fully admit that the boat probably outlasted its designed life as it was built, and it is easy to criticize 1970 boat building techniques with the luxury of 2007 design information. It might make some of those that are contemplating rebuilding an old glass cat…by any manufacture, think twice before diving into such a project.…especially in light of what happened to “airborne”, who obviously invested a great deal of time and money to restore his 5.2 to absolutely gorgeous condition, only to see it self destruct.

Best Regards,
Bob