I just got a pre-1984 Nacra 5.2 in fairly good condition with (seemingly) one exception: the foredecks just ahead of the front beam are softer than the rest of the decking (all of which oil cans a bit, but seems acceptable to my novice eyes) in an area about 8 inches square.

There is a lot of good information about the importance of the structural integrity of this area of the foredeck in terms of forces applied by the pulling of the sail, pushing of the waves, etc, and to look for it when looking to purchase. I have some more basic questions, however:

1) What is the deck, really? I can find some pictures of 5.2 hulls without the decks, but not the decks themselves. They just look like rubber, but seem to have some structural importance. Are they fiberglass underneath? Why not just make the whole hull fiberglass and glue a bit of rubber to the top? There's something here I'm not groking.

2) Does anyone know if there is there a stringer underneath this area? I used my iphone to take a video of the inside of the hulls via the inspection ports, and all the stringers behind the bulkhead look good, at least not falling apart/off like I've seen some pics of, so maybe this would bode well for any stringers in front of the bulkhead.

3) How much does it actually matter? I'm not (yet) ready to hit big winds & waves, so I don't plan on really stressing the boat in the short term. How much concern should I show?

4) Finally, regardless of what was there, it seems like some people have success with taking the decks off and adding stringers for structural integrity. Also, it seems like some people put inspection ports 10-15 inches in front of the front beam and add some fiberglass to the inside of this area. It's not foam core, otherwise I could use epoxy injection; is there something simple like this available to the pure glass construction?

Thanks for any help! These forums and the people on them seem to be the only information about the older Nacras available (my closest dealer is in canada!)

I have a 1977 and 1981 5.2. The decks are a couple layers of fiberglass, not rubber. Maybe someone has done what I plan to do, which is to shoot a layer of colored bed liner material on top and then over the edge instead of gluing on the rubber strips over the edge or putting grip tape.

The 1977 seems to have support under the rivet in the forward deck on the 1977 and the deck is quite stiff there. I'll check this spot on the 81 later today. Otherwise there are no stringers or other support that I could find on the deck plate. There are stringers in the forward hull, just like you see through the inspection ports in the aft. The deck does oil can slightly on either side of the forward rivet in the forward deck, but it is not spongy and does take pressure.

It does seem to me that the 1977 hull is a more rigid hull than the 81. Maybe more fiberglass layup in early hulls. It also seemed just a bit heavier when I stripped the hulls off yesterday to get started on the sanding and new gel coat. The decks on the 77 also seemed to oil can less. The 81 isn't too bad at all, but my 84 5.7 decks really oil can, but don't have any of the soft spots most associate with a foam sandwich layup. It might be due to the long wide area that doesn't have support like the daggerboard hulls.

I did access the forward hulls on my 81 by drilling a 5" access hole with a hole saw. The made up a foam sandwich rectangle with 1/8" high density foam from Aircraft Spruce, and two layers of bi-directional glass on either side. After it cured I heated it a bit in the oven so that I could add a slight contour, but that could have probably been done by putting plastic sheet over the top of the deck and putting the layup on top of the deck so that it set with the curve. Then I inserted into the hole, put thickened epoxy on the top and put screws through the deck to pull it up tight until it cured. Then I put the piece removed by the hole saw back in position with epoxy.

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Craig
Windrider Rave Hydrofoil
Nacra 5.2 Restored and heavily modified
Nacra 5.2 (one under restoration)
Nacra 5.7
Nacra 5.8NA
SoCal
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The foam sandwich rectangle seems like a good idea.

* About how long did you make it?
* About where did you make the access hole? I've heard of people doing it on the inside of the hull near where they want to repair, is this correct (and maybe obvious :)
* What did you do with the holes from the deck screws? Seems like the rubber decks would be impossible to repair, and after thinking about it they would be epoxied in place... so this strategy results in some permanent deck screws? Better than a torn hull!
* Are you happy with the results?

Also, if the decks are a couple layers of fiberglass, how are they attached to the hull? It looks like people can successfully chisel them off the hull, so is it a piece of fiberglass glued to the rest of the fiberglass body? Or, is the body a single piece of fiberglass, and the goal is to chisel through just underneath the edge of the deck and glue back on?

I made the foam sandwich about 10" long, enough to go about 2.5" on either side (front/back) across the hole. You obviously have to make it just slightly narrower than the hole width so you can slide it in. I put a screw in the middle to use as a handle while working with it in the hull.

I made my access hole through the top of the deck about 6 - 8 inches forward. This was close enough to the area where the stringer and the hull wall had separated a bit so that I could easily reach inside and lay up some fiberglass tape and epoxy.

I'm curious about your rubber deck. Do you have pic's? The typical deck is fiberglass with a knurl or diamond pattern in it for non-skid. A rubber deck sounds like someone put something on to possibly hide a repair or simply to add better non-skid and foot comfort. It may just be held down with contact cement. You may be able to lift an edge and add some heat (be careful) to soften the cement so you can peel it back a bit easier.

The hulls have a flange about an inch wide joggled down slightly that the deck piece is then epoxied to. You should have a small recess or gutter between the deck piece and the hull. Paste this link in your browser and you can see the blue deck pieces on the 5.2 hulls.

http://www.slosailandcanvas.com/servlet/the-880/Nacra-5.2-Catamaran-Trampoline/Detail

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Craig
Windrider Rave Hydrofoil
Nacra 5.2 Restored and heavily modified
Nacra 5.2 (one under restoration)
Nacra 5.7
Nacra 5.8NA
SoCal
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Is it the deck lid?

On the 5.2 the deck lids can pop off and you can put new ones on, that is if the factory or Murray's Marine still have them.. There is a lip and with a hammer, chisel, and patients you can get them off in one piece.

I wouldn't worry too much about the deck lids being spongy... My 5.8 had this issue but this was just in front of the rear beam from my sitting on it, standing on, it, etc.... got motivated one day and replaced them even thought it didn't have anything to do with the integrity of the hulls

Regarding your 77 5.2 Had coffee with Tom Rolland one day before the Ti-Point Ocean Race in Ventura. Tom designed the 5.2; and you should consider bringing your 5.8 for the race in August... Anyway as he lamented about the older fiberglass 5.2 "you can take a sledgehammer to that boat and it will still sail.."



Edited by JohnES on Jun 09, 2013 - 03:12 PM.

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John Schwartz
Ventura, CA
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Pre 84 nacra's (before foam sandwich construction) tend to oil can quite a bit on the sides. They can do it on the deck lids a bit but if it is excessive its a bit concerning. If you are hearing a snap crackle pop when it displaces, some of the epoxy is likely cracking away from the fabric. This does happen with glass-only boats quite a bit and can get progressively worse over time, normally a very long time. If it is really soft then it might be getting close to failure. Best thing to do then is to pop off the lid (work around the seam with a chisel a bit at a time to pry it off) and lay a layer or two of fresh glass and epoxy on this inside. Then re-attach with thickened epoxy. If you aren't hearing any crackling then it either it is just the natural give or it isn't attached at the seam to the hull properly. Previous owner might have used a flexible marine sealant to glue the deck lid back on instead of a rigid epoxy. If you can live with the displacement it probably isn't an urgent thing, you never really sit or stand in front of the beam which would be your main concern about the deck lids. Sail it and fix at the end of the season, or early next year.

Answering your questions directly.

1. Deck lids are fiberglass same as the hull. They are just textured, maybe painted maybe rubberized on top. They are glued to the hull with west system epoxy and colloidal silica (thickened epoxy). They play a role in the stiffness of the boat preventing the hulls from twisting mostly.

2. There are two stringers in each hull immediately below each beam. These play a large role in strength an torsion and there have been some problems with them breaking away from the hulls on the sides. A good thing to check because 5.2s tend to break right at the front beam. It's not a difficult fix, but time consuming to take the deck lids off and glass inside.

3. Soft deck lids on an all glass boat probably aren't a huge deal unless you are out double trapping it in big wind. I would keep an eye on it for the season then consider fixing in the off season. Again not a hard repair but time consuming and you have to take the rig apart to do it.

4. The 5.2 is generally a solid boat and well built, no need for extra stringers if the existing ones are in good shape. You also don't want the extra weight and frustration of building the stringers. That is a much more difficult job than reinforcing the existing stringers or the deck lids. Installing an inspection port in front of the beam is a bad idea due to the torsional stresses there. Epoxy injection doesn't work on a glass only boat. You don't get a lot of softness in the hulls but when it happens adding a layer of glass inside it normally the best solution to the problem. Fiberglass is pretty resilient.

D.

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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Hey, thanks for the answers!

Took it out for the first time, and as I'm sure you are all aware, the 5.2 is awesome to sail. Waaay easier to tack than my previous hobie or prindle. Looking forward to putting more miles and mods on it!

@nacraflyer, the deck pieces look pretty much like the link you sent, but grey. Maybe 'rubberized' is the right word; they have a cross pattern and don't feel like fiberglass, but look exactly like the link you sent.

@JohnES, yes, deck lid might be the more precise name. All my deck lids except the far forward lids are spongy where there isn't something otherwise supporting it like the daggerboards or a stringer, but there's no cracking and you don't notice it until you're standing on it and moving around. Since none of these are structural, I'm not going to do anything about it. Same with the hulls. In fact, you can sort of see the stringers from the outside if you know what you're looking at.

@Wolfman, it pops a teeeeny bit on the left pontoon (a few inches in front of the beam), little enough where you might think you were just hearing things. You said "There are two stringers in each hull immediately below each beam"; are these fore or aft of the bulkhead? I checked the ones aft of the bulkhead, and they look good for the most part. There's a weird discolored spot in the corder of one I want to take a better picture of, but again, not falling apart like some pics.


I hear of people trap'ing out in big winds and breaking their boats in the spot mine is soft, and want to make sure that's not me. I like this one!


Thanks again for the feedback!



Edited by woahdae on Jun 09, 2013 - 09:09 PM.

They are the bulkhead, both refer to the fiberglass piece that goes across the hull. There are two in each hull, one below each beam. There are also 2 stiffeners that run along the length of each hull on the sides, just a raised bump that runs the length of the hull. Discoloration at the bottom is normal because there is a drainage hole there. It sounds like you may be worrying too much about it. Someone probably used that area to step on and off the boat quite a bit and it got soft. As long as the decks are well attached and you aren't seeing any damage on the surface gel coat and the bulkheads are intact you should be fine. Sail the crap out of her.

The 5.2 originally was a single trap boat. The replacement rigging normally comes with a double trap. I would probably avoid double trapping on the rig at all. Although I've heard some have good success with double trapping you have to remember that the boat is over 30 years old.

My 5.2 has a big hole in one of the front bulkheads that the previous owner cut to make a repair (that I am going to tackle later this year), I had a huge flat top sail custom made for it and I've spent a some serious time single trapped on it without the boat ever complaining. So they are pretty resilient. The boat actually seriously quiets down when you go fast and its under tension. It's still a darn fast boat 30 years later.

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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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