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

Welcome to the forum Tom, my first two cats were Stingrays a great boat! The rear beam would have started straight, the holes in the rear beam could have been to lighten it or might be access holes to nuts inside the beam can you see the bolts for the traveller track through the holes? You really need a new main beam and new strap for the dolphin striker there is no short cut your up for a length of pipe for the front and rear beam, Nacra will have the parts or specs for everything you need. The bad news is you are up for a few dollars but the good news is you'll have a great boat for not much

gp to TheBeachcats.com and look in the classified section under boat parts. I bet someone has some beams for a couple hundred bucks each. Do a little research, I bet the beams cross over to some of the other nacras, like the 5.2. Pete

I believe the 5.5 has a beam of 8 feet 6 inches, if so it would take a nacra 6.0 beam. The 5.2 or 5.8 will not work

I believe the 5.5 has a beam of 8 feet 6 inches, if so it would take a nacre 5.5 or 6.0 beam. The 5.2 or 5.8 will not work

I'd first check for used beams. thebeachcats.com is a good place to start as mentioned above.

If that doesn't work out, I would either try an internal or external sleeve or source out a blank tube. There is nothing special about "marine aluminum". It is typically 6061-t6 alloy and anodized. Pretty standard stuff. Check out onlinemetals.com.

sm

You can make your own beam pretty easy and cheap. You need 4" tubing, no need IMO to pay extra for marine anything. I made new front and rear beams for a super cat in a few hours.

Hi Jeff, that's amazing you sailed Stingrays too.

I'm disappointed to hear that the rear beam shouldn't have the curve that it does. I wonder if it would affect anything? Theoretically it would bring the hulls slightly closer together in the rear, but it's probably barely measurable. At least now it is something I could make myself from (non bowed) aluminum tube.

I wondered if the holes were to lighten the beam - but unlikely given that much aluminum couldn't possibly weigh more than an ounce or three. You may be right that they are for the traveler. I'll take a closer look.

I am also wondering if I can make a new dolphin striker strap by ordering that dimension in aluminum or even stainless from this place and carefully bending it myself. It seems like a pretty simple hunk of metal. The strap I Have would also be a pretty good/cheap candidate for welding strengthening layer at the centre hole and a few inches up each side.

Money money money! I know I got a great free boat, but my budget is extremely tight, and I need to be as creative as I can be while fixing it properly. I don't have plans to race the boat, so I have some flexibility with all this.

Thanks again Jeff for your input, much appreciated!

Good idea Pete, I'll duck over there and put up a note and see what's around. It seems second hand beams could be almost as expensive as making my own new ones from blank tube. At least the latter would be new, and not come with it's own history and wear and tear.

Good to know, thanks!

I just spent some time browsing http://www.onlinemetals.com/ , what a great site! Man, I can use them for all sorts of projects I have in mind coming up (wood fired pizza oven on a trailer anyone?). I cant believe how expensive blank aluminum tubing is! I'd be looking at US$160 per beam for 4" OD, although I thought I measured it at 4.5" the other day, which jumps up to US$195 each. I doub't I will ever take this boat to salt water, so should I even worry about the anodizing aspect?

I'm leaning towards this blank tubing idea though, or a second hand beam, rather than trying to fix the old one. The damage is pretty bad.

Good to know it can be done.

Your local metal supplier should be able to get you better prices than you can find online.

IF you should used beams locally, they would probably be about the same price as new tube.

If you beam the boat up with a new beam front beam and the old rear beam, the front will bolt up square and the rear will bolt up splayed outwards so there will be twist in the load on the hulls. If anodising will break your budget don't worry about it but make sure you use duralac or similar on all rivets and bolts to impede corrosion. A cheap place to look for this type of pipe is a Centre Pivot manufacturer or similar for agriculture, you would just buy a length and cut it up

The rear beam doesn't carry much load if you need to save money you could weld patches on the front beam and use it as the rear beam, you could even use the existing tramp arrangement and lace to the new front beam

Awesome, I was wondering about this. It seems like all the corrosion problems on the existing beams are galvanic, wherever there was/is a stainless rivet. I'll be sure to grab some of this stuff.

Great idea!

Did you reach out to Pete Beagle who is up in Big Bear? I seem to remember him having some 5.5 or maybe 18 Square beams laying around....

With all the holes in the rear beam it's load carrying abilities may be not sufficient.

How do I get in touch with him? I tried searching his name with no luck.