Hi all, hoping I can draw from your collective experience. I'm stoked to join the forum.

I was recently given a Nacra 5.5 Uni by a kind neighbour. I used to sail a similar sized cat in Australia as a teenager, called a Stingray,. It's been a long time though, and I've never had anything to do with a Nacra.

The Nacra was given to me disassembled. The story I got was that a local guy had his 5.5 crushed in the snowpack one year, so he acquired two new hulls. We think everything else other than the bare hulls came from his old boat. My neighbor was given it all, he stored it in a barn for 6 years, and now he gave it to me. Hopefully the beams and everything else fit the replacement hulls without a catch. *Hopefully*.




Everything was really dirty - mostly heavy dust. Once I gave everything a scrub, it turns out the hulls are in excellent condition. The sail is also in excellent condition, along with the mast and all its components. The rudder blades (x4) and daggerboards (x3) are also in exceptional condition. The tramp is questionable but might hold up, we shall see. The only items that need attention are main/front beam and dolphin striker - which have had some serious damage - and possibly the rear beam is showing its age. I will have many questions eventually regarding the subtleties of setting up the boat properly and the various NACRA tricks and mod's, but first I wanted to get advice on the main beam issue (since this is the essence of the boat really) and get the hulls back together.

The main beam has a deep depression and jagged, torn hole on the underside where the dolphin striker rod passes through it.




From studying the damage, and doing some research on various forums, I have hypothesised: the holes through the centre of the main beam for the dolphin striker rod have corroded; the compression fitting inside the beam has ripped through the beam with the weight of the mast - possibly aided by the support rod jumping out of V-bar (or the pad was missing). The mast probably fell down, further denting the beam and also cosmetically denting the sidewall of the mast a few inches up from the base. It seems that some other folk have also suffered beam damage through some of the mechanics I just mentioned, like here and also here. I don't understand why the torn hole is dented inwards around it, from the underside of the beam, but something bad happened that's for sure. Maybe the beam had a severe downward load (eg. snowpack) that forced it down on the rod enough the force the washer on the rod through the corroded hole of the beam?

The dolphin striker rod is pretty badly bent.



The nylon ball that the mast rotates on is missing. The dolphin striker casting/support pad between the dolphin striker rod and the V-bar is missing. The aluminum V-bar appears undamaged, but has some corrosion around the centre hole. I'm not sure if it's enough to be concerned about - but I want the boat to be safe.

Corrosion on V-bar strap at dolphin striker rod hole
[img]http://s25.postimg.org/kvoonm1r3/IMG_5528.jpg[/img]

[img]http://s25.postimg.org/pyalw50f3/IMG_5529.jpg[/img]

So my key questions are:

Main beam - repair, replace, or make another one from blank tube? Welding some sort of curved patch around the torn hole (after stop-drilling the rips) seems possible, such as they planned to do here but I have many questions regarding the alloy of the patch material, the affect of the heat from the welds on the undamaged areas of beam, the extra height of the patch affecting the mast/rigging, and the cost of the welding. A replacement beam could be very difficult to find, and likely outrageously expensive. Did I mention my budget for this project is almost nothing? I understand they didn't make all that many of these boats. Finally, I've begun researching blank tubular marine aluminum , but this also seems very expensive and I would need 4.5" tubing from memory. The main beam looks to be a very simple thing, so maybe I could buy 8.5ft of blank and swap all the hardware across.

Rear beam - Is it meant to have a slight downward curve along the length of it? It is very symmetrical and seems deliberate, not just the consequence of prior overstressing. Can anyone confirm this is part of the design? I wouldn't be able to replicate this curve in a blank tubular section.

What's with the enormous number of holes in the underside of the rear beam?
[img]http://s25.postimg.org/4fpevd7bz/IMG_5461.jpg[/img]

The rear beam is intact otherwise, but some of the tramp eyelets are missing where the rivets have dissolved and pulled out of fairly badly corroded holes. Some others are loose. I could probably drill all these rivets out, and also drill out the holes larger to clean up the corosion, and redo them with bigger rivets? I don't think the corrosion is bad enough the warrant replacing anyway, since it's not as load bearing as the front beam.

Thanks for taking the time to read this, if you've gotten this far. I really appreciate any advice so I can work on this over the winter!

Cheers,
Tom