I recently pick up a nacra 5.2 which had of course a center beam above the tramp, I have notice others that have removed this potential knee banger without, I assume any adverse effects. Or are there? For those with and without please lend me you opinions, advise, pros and cons, what ever. Thanks

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Jeff O
N5.0
solcat 18(sold),
N5.2,
H16
Camarillo CA
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The center beam keeps the front and rear crossbars from twisting. You can remove the bar but you must rivet the beams straps to the crossbars. Put the ss or monel rivets in all of the straps to the crossbars at 2 o'clock and 10 o'clock and every thing will be fine. A lot of sailors like the center crossbar for a foot hold while sailing, just a matter of choice. Try sailing with it to see how you like it before removing.

The center beam maintains torsional rigidity. The entire boat is now rigid, unlike some designs which give you a clear deck but sacrifice rigidity. The result of no beam is that you lose wind transfer to speed. The chassis flex's and absorbs the wind energy without transferring it to speed. Like the drag cars of the 50's and 60's. Horsepower gets absorbed rather than transferred to the ground because of so much chassis flex. I left my bar in and use it as an excellent bar to push on when I'm one-hulling and pulling on the mainsheet. I like it. But it's not for Nancy-boys...

HULLFLYER

The center beam keeps the front and rear crossbars from twisting. You can remove the bar but you must rivet the beams straps to the crossbars. Put the ss or monel rivets in all of the straps to the crossbars at 2 o'clock and 10 o'clock and every thing will be fine. A lot of sailors like the center crossbar for a foot hold while sailing, just a matter of choice. Try sailing with it to see how you like it before removing.

Do you know anywhere online to get monel rivets?


--
Rob
OKC
Pile of Nacra parts..
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Murray's Marine (google it). You can also use stainless rivets or you can through bolt it with stainless bolts, nuts and washers.

--
Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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i have heard of nacra beam straps breaking more than any other beam issues.... ever.. so make sure you hate the center beam before you remove it...

I do not understand when you buy a used boat (nacra), say it is a 1985 the beam straps are almost 25 years old. They hold the boat together BUY NEW ONES, you would not sail with 25 year old standing rigging. Almost every beach catamaran last a very, very long time, but there is a thing called material fatique, and if you sail the boat hard you should consider looking at everything that either holds the boat together or the mast up. I saw a 1973 Hobie 14 the other day, still going, can you believe that it's 36+ years old, twice the age of the person sailing it.

andrewscott

i have heard of nacra beam straps breaking more than any other beam issues.... ever.. so make sure you hate the center beam before you remove it...

Do you know where they typically break? At the rivets or at the bolts I assume?

It is a bit sad that I've replaced any line that's slightly frayed and never even glanced at the condition of the straps..

--
Rob
OKC
Pile of Nacra parts..
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usually at the fold near the bolt hole, more often the rear strap than the front.

--
Philip
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mummp

usually at the fold near the bolt hole, more often the rear strap than the front.

agreed...

ohmsj, i just noticed your avatar. .. i think your pirate flag would greatly effect your airflow if it is positioned on the sail the way it looks in the picture.

You could not have air flow on your sail with a piece of cloth flapping around it... I would consider attaching it to your leach...



edited by: andrewscott, Jul 29, 2009 - 09:56 AM

mummp

usually at the fold near the bolt hole, more often the rear strap than the front.

Thanks.

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Rob
OKC
Pile of Nacra parts..
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thanks for the heads up on this

mine comes apart every winter so i will check the straps closely for cracks at the bends and maybe cut and bend up some spare scrap stainless as an emergency strap just in case. good to have something hanging on a nail in the garage in case one does go, and it's a bummer to waste a lot of our peak season waiting for overseas parts shipments

as far as the knee-knocker center beam is concerned i replaced the alloy pipe with part of a busted carbon windsurfer mast. with some new resin painted on to restore the shine it added some carbon bling to the boat

i found the center bar a useful footrest for hull flying the 1st year i had the boat, but once i got my windsurfer harness for the trapeze i found i never sat that far inboard anymore. our mountain lake is too gusty for mucking around that close to the tip over point. i want my butt hanging off the side so i can push out very quickly to damp things down in the BIG gusts

for soloing the bar has been NO problem at all

but when i have new crew they find it much harder to get cleanly across the tramp during tacks as they have to crawl over the bar while keeping back low enough to get under the boom

would be much easier for them to simply slide across an unrestricted tramp

also my tramp is probably 27 years old which means i'm in no hurry to remove the amount of support provided the center bar. same reason has stopped me from cutting 4 big slits in the tramp and attaching the jib wires below the tramp

the stitching on the tramp appears to need replacing every 10 years or so but the nylon mesh itself seems very UV tough

this winter i hope to sort a roller furling jib for 2010 sailing

and then a roller furling gennaker for 2011

maybe 2012 for a new tramp???



edited by: erice, Jul 29, 2009 - 07:00 PM

Okay, this strap-breaking business has me concerned. My boat's just over twenty years old but it sounds like the kind of thing I should inspect much more closely than I have. At five bucks a pop it's cheap insurance to have a couple extra. And I have the luxury of having the factory a half an hour up the road.

On the subject of the beam straps, I wanted to ask about the chips that the strap screws go through. Every time I read about these they are referred to as the "black chip." But mine aren't black. Was the black a coating that has worn off, or do I have some substandard item? Replacing all sixteen of them would get into some coin.

Bob,
There are different size straps, one for the front beam and one for the rear beam. One is longer than the other. As for the black chip it is anodized, hence the color, no big deal. It will be o.k. to use the old ones, even if they have some pitting. Remember to apply marine grease.

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Philip
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if the straps are only $5 each it wouldn't hurt to have a front and rear strap in your boat box

fortunately stainless is not like carbon-fiber, it won't just let go without any visual warning. probably a small crack will be visible starting from the edge, on the bend for months before it grows right across and fails

at the end of the season last year i noticed that i hadn't tightened the straps enough and that the beams had slipped out of the straps a few mm so that the bump-stops on the beam were no longer touching the metal plates on the hulls

so now when i set the boat up i quickly check that the bump stops are touching

won't be hard to occasionally also check for tiny cracks on the bends

Make sure when you replace the straps, that you put the black chip back on properly. You will notice that one side is more rounded than the other. Place the more rounded side towards the beam and facing down. When you look at the chip you will understand. The other side is a bit sharper and can work on the strap and weaken it over time.

All good advice. Thanks guys.