I got her out to start prepping. I checked the torque on all the strap bolts. The front beam, starboard hull, inside aft bolt (confusing?) is snug but will not tighten to spec. The others are all fine.

Here's what I need to know. Do those bolts each have individual nuts inside, or is it more of a plate for bolt pairs. I noticed one or two bolts have bigger heads. Maybe they were replaced earlier with larger diameter bolts??


Also, assuming I need to go inside, can I put a port in the deck? It would be halfway between the front beam and the shroud on each side. This would allow access to the beam nuts and shroud tangs should those ever need attention. Alternatively, I do have one experience removing and replacing Nacra decks. It's not awful, but in this case I think I could actually put a slice crossways in the deck and only need to remove about 6-8 inches. Thoughts?

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Tim
Collierville (Memphis), TN
Supercat 15--sold :(
Hobie monocat--given
Vanguard 15--traded for...
Nacra 4.5--sold
Nacra 5.7
Hobie 14–sold to make room for...
Supercat 17–sold
--

Update: no major repair needed!

I discovered the nut is stripped. Now I have the choice of heli-coil or drill and tap to net larger size. Input please.

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Tim
Collierville (Memphis), TN
Supercat 15--sold :(
Hobie monocat--given
Vanguard 15--traded for...
Nacra 4.5--sold
Nacra 5.7
Hobie 14–sold to make room for...
Supercat 17–sold
--

Helicoil works fine. Also you can put a port where you said. Mine has one in each hull. Just don't put one in front of the front beam. That's a high stress area.

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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Thanks Wolfman, apparently everyone was out sailing today while I was working on my boat!

If anyone is interested, here's what I did.

I opted to drill and tap for these reasons. I know the previous owner installed 2 oversize bolts so I thought I'd follow suit. Also, I was not completely certain that the helicoil would not cause some kind of galvanic corrosion. Drilling and tapping is probably just a touch easier and there's no chance of dissimilar metals. I got 3/8-16 ( I think) drill, tap, and stainless bolt. (Original size is 5/16-something). Drilled, tapped, installed. Hardest part was drilling the strap and washer to fir new bolt.

And DONE! Tightened up very nicely to specified torque. Very happy for no need to cut fiberglass.

--
Tim
Collierville (Memphis), TN
Supercat 15--sold :(
Hobie monocat--given
Vanguard 15--traded for...
Nacra 4.5--sold
Nacra 5.7
Hobie 14–sold to make room for...
Supercat 17–sold
--

IIRC the "nuts", actually small plates, inside the hull are brass.
Put some grease on each bolts threads, & only torque to 18 ft lb, that's not very much.
After a couple days sail, re-torque them, they will be a bit loose. After that you're good for the year.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

The earlier glass bedded plates were brass, later factory went to aluminum. What causes the failure is the galvanic corrosion over time. When you go to try to unscrew the bolt that hasn't moved in decades, the corrosion breaks free stripping the plate.

Definitely grease the bolt . . . and as John S. likes to say, you should routinely "exercise your nuts"

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Philip
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Quote

Just don't put one in front of the front beam. That's a high stress area.

I agree the area directly in front of the beam is high stress, but the deck plate is not really sharing very much of that load in my opinion. I just put a new port about 12" in front of the beam so that I could inspect the front side of the bulkhead for cracking. Hopefully I haven't sunk my ship, literally. I guess I have seen many NACRA's with this additional port. Has anyone failed a hull through one of these forward ports?

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dg
NACRA 5.2 #400
This End Up
Original owner since 1975
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If it's at least 12 inches in front you are probably OK. I know that many older nacras and especially 5.2s have failed at or just in front of he the front beam. Mostly attributed to the bulkhead under the front beam failing or delaminating from the hull. The whole bow section tends to see a lot of stress from being pulled on by the bridle/forestay connection and the rigid front beam. It tries to bend and twist all over. So the more strength the better. If you don't see any cracks or crazing best just to keep an eye on it and monitor. Trying to patch the port area will just lose your inspections hole and may not change the strength situation much. Especially keep an eye on the front bulkhead inside and near the beam bolts and bridle tang. A little gelcoat crazing is normal at the beam bolts but if you start to see real penetrating cracking start to think about reinforcing and repairing before you end up with a huge problem. With a little luck nothing will develop and no worries.

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

With the age of my boat I thought it was important to see both sides of that critical bulkhead and the underside of the beam bolts, hence the new ports. It is also good to now be able to see the forward areas of the hull. When I really got into the rebuild it struck me as strange that there isn't a similar bulkhead under the rear beam. The racking of the boat could have been further reduced with a bulkhead there.



Edited by dmgbear55 on Aug 02, 2016 - 10:56 PM.

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dg
NACRA 5.2 #400
This End Up
Original owner since 1975
--

Quote

but the deck plate is not really sharing very much of that load in my opinion.

The deck plate is essential. Essentially, the entire hull is a box beam. If you remove a substantial portion of any side, you greatly weaken the structure.
A rough analogy is a cardboard box. Close the top flaps & tape them shut, the box is pretty strong in all directions. Leave the top open,(remove the deck), & your strong box becomes a very flimsy structure.

Quote

strange that there isn't a similar bulkhead under the rear beam.

The 5.7 has a full bulkhead, it is in front of the rear beam. This makes sense. The hull is larger as you move forward from the beam, giving a larger bulkhead, which gives a stiffer hull. Also, dividing the hull into 1/3rds is stronger than having the bulkhead back near the stern.
As you know, the skeg hulls need to be tipped quite a ways to drain. I tried to install a tube that would end at the deepest part of the hull, but couldn't get it past the rear bulkhead, as there is only a small opening at the bottom for drainage. I didn't want the hassle of removing decks, so I installed small ports, & use a float pump, (for pumping out floats of small seaplanes).

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

What Kinda Grease does everyone use?
I am impressed with Tef-Gel.

I think i still have some on my hand from 3 years ago,

Yes what Chris said. That also seems to be an issue when people use sealant to glue their decks back on instead of thickened epoxy. I've heard of the decks popping off under pressure while sailing because the glue was flexible. I'm still of a mind to leave what you have alone and monitor to see if things start to crack before attempting a patch. There is a certain amount of risk involved in removing the decks, which you will likely have to do to get the strength you need from a patch. I've now heard of a few people wrecking their decks when removing them (although i didn't have a problem). 40 year old boats can be a bit fragile for those types of things.

I use standard black high pressure grease and haven't had an issue.

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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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I think I will start a new thread on these decks.
dg

--
dg
NACRA 5.2 #400
This End Up
Original owner since 1975
--

Quote

What Kinda Grease does everyone use?

Nacra originally used a regular,(cheap) utility grease. The parts are not under extreme load, & the threads are not exposed, so the grease stays there, for years.
I have disassembled the 5.0, 5.7, and H18 by just turning a wrench, but these were all freshwater boats.
I use trailer bearing grease, just because I have a tub.
Remember, many of these bolts that freeze up were probably never exercised in 3 decades of saltwater use. Grease them every 5 years & I doubt you will have a problem.
Tef Gel is good stuff, but I think it's way overpriced. Ask a truck shop what they use. I can't recall the name of a product I was given years ago, but it was dirt cheap, & they use tons of it.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

I just used automotive anti seize. If it's good for spark plugs and cylinder heads it should be ok on a beam bolt

--
Tim
Collierville (Memphis), TN
Supercat 15--sold :(
Hobie monocat--given
Vanguard 15--traded for...
Nacra 4.5--sold
Nacra 5.7
Hobie 14–sold to make room for...
Supercat 17–sold
--

Yes, I'm sure the Permatex copper,(hi heat), or Silver, (lo heat) would work fine, BUT... You have to stir it up as it separates over time, & every time I dip into my bottle of Copper. I invariably get some where I don't want it, & it is a major PITA.
It smears, stains, etc, much worse than plain grease.
For that reason I leave the Permatex for engine work.
I keep a small makeup container of grease for the Cat. Just dip the bolt & install.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

I just use the squeeze tube

--
Tim
Collierville (Memphis), TN
Supercat 15--sold :(
Hobie monocat--given
Vanguard 15--traded for...
Nacra 4.5--sold
Nacra 5.7
Hobie 14–sold to make room for...
Supercat 17–sold
--