Nacra 5.0 U-straps?

The crossbeams on my NACRA 5.7 are held in place with beam straps (8), black chips (16), 5/16" 18 pitch x 2" Bolts (16) and Washers (16).  The stainless straps that fit over the 4" diameter beams are 8-3/4" x 3/4", so you might be able to recreate the required straps. They are held in place by black anodized "chips that have a hole drilled for the hold-down bolt.  The manual specifies lubricating the chips and bolts before attaching to the threaded holes. There is a threaded metal chip embedded in the fiberglass that holds everything in place.  I have seen threads on this forum where members describe repairing that threaded embedded nut, but I don't know where those photos and write-ups exist on the new board.  On the N-5.7 I also have an internal metal casting hold-down that fits inside the crossbar and butts against the tramp groove, and is secured with a 2" x 5/16" bolt to prevent rotation of the beam.  I hope you find the details or manual you need for your N 5.0 that shows the original assembly. 

The manuals linked below seem to confirm your assembly is similar, if not the same as mine.  I would not want to rely on a crossbar assembly that departs significantly from what was designed to be used.  I'm sure another member with a 5.0 can verify what parts are used, and maybe you can even buy parts from a salvaged Nacra boat.  It appears this same hardware was universal for the 5.0, 5.2, 5.5, 5.7, 5.8 boats.  Someone else can correct me if I'm wrong on that.

Here is a link to the Nacra Vintage Assembly Manual that has some images of what I described above Nacra Vintage Assembly Manual

Here is a link to a 1985 Assembly Manual with mostly the same information 1985 Assembly Manual

Here is a link to a Nacra 5.0 Assembly Manual Nacra 5.0 manual

Although expensive, the front beam straps are available from Murrays Murrays Front Beam Strap

Just remember, the front straps and rear straps are different sizes.  The bolts are anchored into aluminum plates that are glassed into the hulls.  The biggest headache would be galvanic corrosion compromising the aluminum plates.  If that happens, the easy solution is step up one size with the SS bolts and drill out the straps some to accommodate the larger bolt.  The whole system is no good without the 16 black chips that Tom mentions. The chips are what tension the straps.  The internal beam casting is also an important part of the front beam assembly.

Reading an old manual, it said that on the boardless boats (5.0) they had the same size clamps. I have a used set of clamps and chips coming from another 5.0. I am asking if I can drill and tap my boat for the clamps? Does my 1983 have the aluminum beded in the fiberglass to tap into? Thanks, Tom

I think the clamps on my 5.7 are also the same size, but I was tempted to check based on Philip's post. Congrats on getting the set of clamps and chips. I don't know why your boat lacks the hole leading to the tapped slug inside.  If it has been repaired or painted in that area it might be worth scraping back the top finish to see if you can locate the original (filled) holes.  As I said the original bolts were 5/16-18, and if you can expose the original threads that would be best, even if you have to re-tap.  If you can locate a modern metal detector capable of detecting aluminum or stainless steel, you can verify if the threaded slug is buried in the laminate.  The 1983 5.0 should have been attached as shown in the manuals, and I'm sure it's just been finished over.

I do not see any indication of holes for the strap bolts. I do have 'spider cracks' in the gelcoat on the inside of the rear crossbar, that will have to be repaired, maybe even 'beef up' with additional fiberglass? I was thinking that was why the u-straps were added? I question weather there is an aluminum backer within the fiberglass, I just might have to drill into there and see? Thanks for the replies, Tom

I ground away the gelcoat over the 'spider cracks', they extend thru the fiberglass. I will have to decide how far I want to go in to repair this? The cracks go to the inside 5/16" bolt coming up thru the crossbar. I really don't want to go into the saddle area with my new fiberglass? I do have a 'bore camera' I could insert and see what the inside looks like? Others thoughts? Tom

@16newbie I have similar radial gel coat cracks in one bow of my boat surrounding the bolt hole for the bridle bracket. I haven't confirmed if they are present in the layup under the gel coat. I did speak with a technical rep at hobie and he confirmed that I could do what you did to see whether the underlying fiberglass is similarly cracked. He said the fiberglass can definitely be repaired, but I got the impression that part of the hull is pretty solidly made. I don't lose sleep over it, but I can understand wanting to know for sure. 

16Newbie, I have of course never dealt with filled holes. At some point you're going to have to approximate where the clamp hold-down nuts should be embedded and drill to see if they are there or not. The worst case is that you drill through that thick portion of the hull and may have to use a large washer and bolt on the inside.  Do you have a deck port where you can reach under the crossbar?  If so, there may also be a bulkhead there that will make reaching the forward bolt difficult. The bolt hole under the crossbeam should be the hold down for the casting that secures the beam to the hull and prevents twisting. Do you have the casting?  I would not worry about superficial crazing in that area as it is common with all the boats.  I sanded that out of mine when I refinished the hulls, faired and refinished.

Thanks for replying Tom! I don't have a hatch behind the crossbar yet. I read a bunch of old threads last night and am considering pulling the antislip panels off the top to expose the inside of the hulls. Then I would install the U-clamps and bolt thru the hulls with a common aluminum plate on the underside. It also gives me access to other potential concerns. The cracks on the inside of the rear crossbar are all the way thru the fiberglass. I am afraid if I don't make a major repair I will have a major failure. Tom

Over the years, I have used the port to access inside the hulls many times to repair, maintain and store things.   The convex port lids are hard to come by now.  I have had several reglassing and reinforcement jobs inside the hull. For example this damge:

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After considerable reading today I pulled the rear fiberglass top deck off my 5.0. Taking them off is not for the faint of heart, as I had expected. It does give me access to both undersides of the rear crossbar area and the rearward side of the front crossbar area. There is a bulkhead under the front crossbar, I plan to use the smallest holesaw I can get my arm thru to reach the front side of the u- clamps. I can epoxy a patch over the hole if needed? It will be some extra work, but at least I have a solution to the underside of the u-clamps. Last Saturday a friend repaired my mainsail where the shrouds and diamond wires rubbed.

Posted by: @16newbie

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After considerable reading today I pulled the rear fiberglass top deck off my 5.0. Taking them off is not for the faint of heart, as I had expected

Good on ya' tackling a daunting job, git r dun!