My hulls are worn from dragging the boat over sand, rock, etc and so I'm considering restoring the hulls on my solid fiberglass, pre-foam core (1985) Nacra 5.2. I've googled around to get an idea of what I'd be getting into if I start this project. I'll probably just epoxy along the bottom and gel coat, however, while I'm at it, I'm weighing the pros/cons of removing the deck plates to stiffen up the hull which tends to oil-can a bit.
(On Nacras 5.2's and probably the 5.7,5.8,6.0's, the matted surfaces on the top of each hull are actually glued on fiberglass "deck plates" which can be popped off with a knife).
So a couple questions related to this undertaking:
1. Hull bottom repair: Adding fiberglass 2 to 4" wide tape, filling/feathering, then gel coating seems like a robust way to build up the hull bottom. Has anyone been satisfied with just heavy epoxy and gel coating (it'd be easier). I take on some water during a 2 hr race, maybe a quart.
2. I assume removing the existing deck plates will damage them, is there anyone that continues to sell these?
3. I don't know how concerned to be about hull oil-canning of the hulls, thus the consideration of getting access to the inside of the hulls and adding fiberglass to stiff things up. I've had the boat for 3 years and I can push the hull in roughly 1/2" in just about every mid-span location on the boat. When out on the wire, I keep my feet on the edge of the hulls, but I'm a little concerned that one day I might put my foot thru if I miss-step. The oil-canning is definately more pronounced than other Nacras I've seen, but they've all been Nacra 5.7 or 5.8's that are probably post '85 and foam-core construction.
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Pairajacks
1985 Nacra 5.2
Corvallis Oregon
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Nacra 5.2 - Hull bottom repair, and where to buy Hull Deck plates
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Posted: Sep 12, 2015 - 04:14 PM
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Posted: Sep 12, 2015 - 04:56 PM
If your keek is still solid and not worn through anywhere adding a wear strip of marinetex will work fine. If you are wearing into the glass significantly you are probably want to add some layers of glass. Honestly I did some major work on my hulls this year and if you have the boat apart and the hills flipped it isn't that much more work to add a few layers of mat and then thickened epoxy. Just as long as you have a decent random orbit sander a grinder and you mask things off its pretty easy. I'm not sure I would even bother gel coating the keel, just put a layer of white marinetex and sand it smooth. Nobody is really going to see it.
You can stiffen the hulls but that is going to be a lot of work. As long as they aren't crackling to much when they oil an it's probably not worth it. The prefoam core boats are pretty flexy. If anything put a few access ports in so you can keep an eye on things.
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Sep 12, 2015 - 05:18 PM
I'm pretty sure no one sells these.
My '84 oil cans quite a bit. I find if the ball of my foot is on the top edge, it places my heel low enough to rest on an internal stringer. Between those lines, I can see it move.
If it were my boat, I wouldn't bother trying to stiffen it up. In order to do the entire hulls, you would add some weight.
I have not removed decks personally, but I've seen it done. Some come off easy others not so. The deck I watched come off a 5.2 was quite usable, but since it doesn't come off in a smooth finish, you need to use thickened epoxy to re-bed it.
The easiest fix is to flip the hulls, lightly sand, then wipe with acetone. Buy a roll of 2" or 3" tape,(Johnstown Supply sp?). Run a line of masking tape just below where the fibreglass tape will end up.
Thicken up your epoxy somewhat, paint a thin layer on, then lay the cloth...the tape will lay VERY easy. Then gently paint more epoxy into the cloth to get full saturation. As soon as you are done you can start another layer on the first hull.
It will cure with a few tiny stickups, where fibres in the glass didn't lay flat. Just give it a couple swipes with 220 grit.
I did the 20' Mystere in an hour,(not counting prep) 3 layers. IIRC I used a 4" base layer, followed by two layers of 2" tape..
If you use the West sytem & "clear" hardener, it is almost invisible from a few feet away. I used microfibres, because I had them. They are not as resistant to wear as colloidal silica, but it sands any drips way easier, & the microfibre imparts a whiteness tot he mix...if your hulls are now white.
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Posted: Sep 12, 2015 - 09:45 PM
Are the deck plates simply laminated glass/resin with the anit-slip texture cast in and what material are they glued on with by the OEM? What do you use to glue them back on if you remove them?
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Hobie 16 (3 formerly)
MacGregor 25 (formerly)
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High Point, NC
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Posted: Sep 12, 2015 - 10:01 PM
Yes they are just fibreglass. They you just sand the mating areas clean and they are glued with thickened epoxy (epoxy with enough silica added to make it a toothpaste consistency). I took one of mine off last year and it came off fairly easy working a sharp putty knife around the perimeter a few times.
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Sep 13, 2015 - 08:46 PM
Oil canning the hull? I'm not a NACRA sailor, but that doesn't sound too good to me. If it's doing this in the bow area, I'd be concerned about catastrophic hull failure.
I'm in the process of reinforcing the bows on an older Hobie 18. I cut a couple access holes in the forward deck and am laminating in reinforcement stringers inside the hull. You can do a search for "Prisma Composite Preforms". They make prefabricated fiberglass/foam stringers that you can epoxy into the hull. They come in various sizes. I'm using the 4.5" wide x 1" high planks. They're sold in 4' lengths and each one will add about 2 lbs, so there is a bit of a weight penalty, but my hulls are rock solid where I've added these.
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Posted: Sep 13, 2015 - 11:51 PM
Non foam sandwich hulls are not nearly as stiff as ones with foam sandwich. They are also relatively thin, however they are resilient. Oilcanning on the sides is nothing to worry about. Cracking and delamination are structural issues that have to be addressed. 5.2s can break at the front beam if the stringer right under the beam becomes detached so its a good idea to have an inspection port just behind the front beam on each hull so you can look at them from time to time. Reinforcing them with extra stringers could cause more problems and unintentional high stress areas. Not only that but it simply isn't worth the effort for a 1975 Nacra 5.2, fix it when it shows signs of damage or pick up a parts boat for a new hull for a few hundred bucks.
My 1981 5.2 oil cans pretty badly and I sailed it hard and fast for years. The only reason it isn't out this year is that one of the front stringers is broken and I need to find the time to fix it.
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Sep 14, 2015 - 12:58 AM
Thanks so much for all your inputs! This is a wonderful forum and a necessity for these 30 year old boats that are still going strong. I'll revisit this page this winter when I start work on the hulls. Based on the discussion here, I don't plan to remove the deck plates; I'll just keep an eye out for cracks.
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Pairajacks
1985 Nacra 5.2
Corvallis Oregon
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Posted: Mar 30, 2016 - 01:24 AM
Wolfman,
You mentioned that you took the deck plates off of your 5.2 recently by working a putty knife around a couple times. I'm about half way thru removing the main deck plate and starting to have regrets. (There's two long cracks running lengthwise, so I thought I could make some repairs from the inside).
Two questions:
1. The inward side of the deck plate is hard to get to because of the extrusion for the tramp (I suppose you have to drill the rivets out and remove the tramp extrusion, right?).
2. How is the dagger board tube attached/detached?
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Pairajacks
1985 Nacra 5.2
Corvallis Oregon
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Posted: Mar 30, 2016 - 01:09 PM
I don't think anyone mentioned this above, but you said you were going to use epoxy to repair the hull bottoms and then gelcoat. That is generally considered a no-no. Gelcoat is likely to give you issues if it's applied over epoxy. You're better off using polyester or vinylester resin if you plan to gelcoat. Also, since the hull bottom is subject to a lot of wear/abuse, you're better off using the less expensive polyester resin there anyway.
For re-bonding your deck plates to the hull, epoxy is the way to go since it has superior adhesion and bonding properties when compared to polyester.
Regarding the oil canning, my understanding is that the older NACRAs (non-foam core) used internal stringers to stiffen up the hull sidewalls. If your hulls are flexing a lot, I would suspect that the stringers have either cracked or detached from the hull.
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Posted: Mar 30, 2016 - 07:05 PM
I'm sorry to hear that!
Yes I did, unfortunately it was the front decks and not around the daggerboards. You can see a good set of photos of what is underneath those here http://www.thebeachcats.com/pictures?g2_itemId=119934
However looking at the various pictures you should be able to work around the tramp track with a flexible knife. Once you get it started at one end it becomes a lot easer since you can pry it long the seam.
The daggerboard trunks will be a bit trickier the seam is just below the lip of the trunk. you can see a picture here about half way down http://www.thebeachcats.com/forums/viewtopic/topic/15792
I would say worry about that last. Likely if you work one end open and follow under the seam towards the trunk it should come free without you haveing to dig too much.
Patience will be key, if you work carefully you should be able to get them off without damaging too much. Even if you do though they are fixable, just more ffiberglass repair.
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Mar 30, 2016 - 08:49 PM
Here is a different take on the daggerboard trunks that may work for you. Sounds like they cut around them with a dremel. I'd rather try prying them off first myself though. http://www.catsailor.com/forums/ubbthreads.php?ubb=showflat&Number=121822
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Apr 05, 2016 - 12:13 AM
I usually use west system epoxy and with a filler when I do the bottoms. Adds a little wear resistance if you use the right filler.
Just 2 more cents.
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Cesar (Cez) S.
Hobie 16 (had a few)
Nacra 5.2 "Hull Yeah"
Vectorworks XJ - A class (not named yet)
West Michigan (Grand Rapids/Holland Area)
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Posted: Apr 05, 2016 - 12:14 AM
delete - posted twice for some reason
Edited by cezo823 on Apr 05, 2016 - 01:16 AM.
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Cesar (Cez) S.
Hobie 16 (had a few)
Nacra 5.2 "Hull Yeah"
Vectorworks XJ - A class (not named yet)
West Michigan (Grand Rapids/Holland Area)
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Posted: Apr 05, 2016 - 11:17 AM
Polyester over epoxy works quite well based on this research:
http://www.westsystem.com/ss/polyester-over-epoxy/
I've done it many times with excellent results.
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Hobie 16 (3 formerly)
MacGregor 25 (formerly)
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Posted: Apr 05, 2016 - 01:11 PM
Original hull construction is polyester. Gelcoat is polyester. This is neither a structural repair nor a bonding application - this is a bottom job. There is no reason to use epoxy here. Polyester is cheaper, has faster cure time, and better material compatibility. Yes, you could use epoxy, but you risk having issues with the outcome of the gelcoat with no real benefit to the end repair.
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