I have recently finished up a TON of fiberglass work in my 1980 P18 including repairing a 6-ft crack/separation at the aft interior hull deck seam on my port hull, installing a new glove/storage box in the opening I had to cut for interior access for the hull repair, a quick bottom job on both hulls, and sanding and polishing to remove about 31 years of oxidation from outside storage. Boat is now structurally sound, smooth as silk, and decent looking, some spots of fiberglass resin are visible through the sanded gelcoat but either a full paint job or spraying new gelcoat are on the agenda for this winter.
My question is what do I need to use to bed/seal the various fittings back to the hull. I can't find anything in the owners manual that has any relevant info so I must defer to the experts (you guys). I must get the boat together this week in order to let things set/cure before my trip the following weekend so ordering exotic items is out. My primary choices for sealant/adhesive are clear silicone or 3M 5200 both of which I have on hand. Which product would you use for each fitting or would you use no product at all.
The following list are the items I need to reattach to the hulls:
Drain plug housings (Stainless Steel)
Gudgeons (Stainless Steel)
Standing rigging load spreaders (Stainless steel bars under the hull lip (exterior) with a hole to the rigging point)
Cross Beams (Aluminum)
Cross beam access plugs (Plastic)
Hull ports (Plastic)
Glove box (Plastic)
I tried to take pics for a tutorial/album but I did most of the work alone so the pictures fell victim to the pot life of my resin most of the time. I will try to post what I have in the next few weeks along with a materials list and a blow by blow account of the repairs so maybe someone can use the info in the future.
Thanks in advance for the advice.
Bedding hull fittings and cross beams - Sealant/adhesive selection
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Posted: Jun 13, 2011 - 08:11 AM
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Posted: Jun 13, 2011 - 11:30 AM
Go to this forum and read this thread.
http://forums.sbo.sailboatowners.com/showthread.php?t=117172
Butyl Tape is the only way to go. It will seal and you will be able to remove it later. It is not an adhesive. That's what the nuts, bolts and screw are for. I have restored a 32' mono-slug and this is the way to go.
Do NOT use 5200. That sh*t is evil.
If you use silly-cone. Never plan on painting the boat again.
There is something to be learned from go-slow boats.
The Butyl tape is cheap and can be bought at RV shops. Standard material to seal windows and hatchs on RV's and Trailers/campers for years.
Good luck.
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Posted: Jun 13, 2011 - 12:29 PM
Thanks for the input. I read the link and everything they were doing was deck or above the water line. I wonder how it would translate to below the waterline. -
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Posted: Jun 13, 2011 - 01:20 PM
That is a good question. I can tell you the yard that replaced the seacocks on my Mono did use 5200. Just about the only place on the boat where I would do that.
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Posted: Jun 13, 2011 - 02:19 PM
I have used adhesive/sealant all over my boat to bed eye straps and to seal rivets in addition to through bolting and screwing. I don't know about the butyl tape but that sound like a good option to seal those areas. I second the vote, Don't use 5200! It it evil in every way. It likes to let go when you don't want it to and won't come off when you want it to. I swear by Sikaflex 281, but like was mentioned above, make sure you have your gelcoat and painting completed before you apply it and clean up around it with acetone while it is still wet. You won't get paint to stick to it. And excess left on the paint will discolor noticeably leaving a stain on your nice new coating and no possibility of getting it off without sanding..
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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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Posted: Jun 13, 2011 - 06:23 PM
You can use 5200 on things that need adhesive. For anything that requires sealing and is a item that may flex you want to use a bedding compound. Bedding compound will flex with the item and anf the sael is self healing. 5200 and standard silicone at times will flex and break away. Once this happens the joint will leak and enter the fiberglass and then can delaminate. You can find bedding compounds at any good boat yard. -
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Posted: Jun 13, 2011 - 06:26 PM
I didn't know there was a special marine version of the stuff, I thought butyl was butyl. I have several rolls of it left over from changing a bunch of windows. When the seals went on some units we went to argon filled, reflective units. A window company built the new glass units for very reasonable cost, & told me to use butyl tape around the perimeter, maneuver the sealed units into place using suction cup hand grips, press around the edges, then replace the trim.
He claimed the tape was enough adhesion to hold against wind pressure, they would never leak even in hurricane conditions, & if you ever have to replace the sealed unit again due to breakage, the stuff comes off with a putty knife.
I think I'll test some of it on some fittings on my Invitation. The stuff from the window company was only about $10/roll.
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Posted: Jun 13, 2011 - 10:09 PM
Take a look at what you have. There is a butyl window caulking. But it will dry out and crack when it flexes. It sells at Home Depot for about that price. Not the same as the butyl tape in m link. It goes by the name of martec or some thing like that. it comes in a ribbon with 5 strips together. I ahve some in the garage. I'll see if I can find it. Not as good as the RV stuff.
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Posted: Jun 14, 2011 - 05:56 AM
The sealants used in insulated glass, and in glazing windows is similar, but not under the waterline.
In insulated glass, the semipermiable membranes are allowing the migration of watervapor into and out of the unit, depending on the pressure and osmosis. Submerging the sealant would allow the water vapor to move from outside the hull, an area of greater concentration, to inside the hull, an area of lesser concentration. Over time, sealed insulated glass will accumulate watervapor. When the accumulation exceeds the unit's dessicant's saturation point, the glass fogs. There is no dessicant inside your hull, but there is a drain plug. I would reccomend Dow Corning 797 for sealing above the waterline, and the Dow Corning Marine Silicone for anything below the waterline.
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Todd Elozory
H18
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Hobie Mirage Tandem Island
Catalina 22
Thonotosassa, Florida
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Posted: Jun 14, 2011 - 12:34 PM
I thought the whole point of sealed units was to prevent any movement of moisture? In cooler climates, as soon as the temp drops at night, any moisture would fog the glass. We have units that are 20 years old with no issues. As soon as the seal comes undone, even in one little spot, the window fogs. It would also let the argon leak-out very quickly.
The sealer used to bond the panes together is not the same as the glazing tape. The stuff holding the panes is very tenacious, it is nearly impossible to separate panes without breakage, & you need a razor scraper to remove the black stuff.
The glazing tape is very mild adhesion by comparison, & is only used on the outside of the outermost pane, to provide a water/wind proof seal between that pane & the outer window frame. The interior trim holds the unit against the frame.
In reading through that fellows threads, I noticed he actually called it "glazing tape". The rolls I have were purchased about 5 years ago, they are still soft, & a bit can be stretched over a foot before breaking, & look exactly the same. I'll have to check the manufacturer, a few calls to their techie departments can often yield much information..
It certainly was an informative article, & I just rebedded the vent plugs in my Nacra hulls with marine silicone!
Edited by Edchris177 on Jun 14, 2011 - 06:46 PM.
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Posted: Jun 14, 2011 - 01:31 PM
Do you have any experience the 3M line of VHB tapes and how well they seal? I know they are damn near permanent as an adhesive, but do they seal as well?
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Posted: Jun 14, 2011 - 06:56 PM
I know the caulking tubes are not the same stuff as the glazing tape.
I'm going to do a few experiments in the next few days, sealing some corks in bottles, then submerging them off the dock for the season, then leaving them under the ice for the winter.
I won't now til next spring how they hold up.
One other factor that the sailing thread factored in was how much the fitting moved. If it never moves,(think your drain plug mounts) most sealants will work.
He was concerned with things like cleats, & stanchions. Stanchions especially have long lever arms, & are subject to quite a bit of movement, any sealant that hardens, or can't take deformation will leak.
I have not used the 3M product, & had not thought of using the glazing tape. It does make sense. When I worked as a bush pilot in the Arctic, all seam in the floats were sealed with a tape before being riveted. They were subject to horendous vibrations & flexing loads. The name of the stuff escapes me just now. It was 2" wide, medium drab green,(same color as the aluminum primer) & had a peculiar smell.
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Posted: Jun 15, 2011 - 05:00 AM
Ed sealed insulated units are designed to increase the insulated value of the glass component of the wall. There are dual seal unit, where the primary sealant, usually butyl tape, seals the space between the glass and the aluminum sirspace; the secondary sealant adds a structural bond to the unit, either silicone, polysulfide, polyurethane, etc. The water vapor transfer rates for each sealant are different, butyl has the lowest, hence it's use as a primary sealant. There are also single seal units available, The dual seal units are used primarily in commercial applications. There were a lot of construction projects that incorporated two sided butt glazing, only two of the units edges were captured by framing, and there were some projects that used 4 sided butt glazing. Those buildings have the appearance of all glass, no aluminum. The structural components were added to keep the outboard lite of glass on the buildings.
The glazing tapes are used to seal the unit into the frame. They would not be recommended for marine application. The back bedding tapes are generally foam with double face adhesive. The glass stop applies enough pressure to compress the tape sufficiently to keep the outside air out.
The use of gas filling is only widely used in colder climates. Argon and Krypton are both colorless and oderless. How do you know there is any gas inside the unit? If the sealants are semipermeable, why does the insulating gas stay in the unit? In the sunbelt, the units are filled with ambient atmosphere. There is a dessicant, a molecular seive filled into the aluminum airspace. The purpose of the dessicant is to absorb any moisture or water vapor that enters the unit. When the dessicant reaches it's saturation point, the unit will fog. Once there is sufficient watervapor inside the unit, the organic seals deteriorate. Generally along the bottom edge, because that is where the condensation settles. If you catch the failure soon enough, you can cut the unit apart and reseal it. Most of the time, it is far less expensive to just buy a whole new unit. The glass units in my house are made with a reflective azure blue glass, so when I see the unit starting to go, I pull it our, cut it apart and reseal it with butyl.
The biggest cause of seal failure is exposre to excessive amounts of water. The window, and glazing systems are designed to channel the intruding water away from the glass through the use of weep systems and setting blocks. Water seeks the path of least resistance. Once inside the glazing pocket, it will attack the sealant, if the unit's edge is resting on the sill. The stting blocks elevate the edge to allow the water to weep out. Other cause include chemical reactions with other sealants; an acetoxy cure silicone would be a poor choice for a toe bead with insulated glass. Before a glazier installs a large scale project, he should check for sealant compatability. Another common cause is using setting blocks of the wrong durometer. The setting blocks are made of rubber or lead or plastic. If they are not placed correctly, they can cuase the unit to shear, or apply too much pressure to the sealant and push the airspace into the vision area.
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Todd Elozory
H18
H21SE
Hobie Mirage Tandem Island
Catalina 22
Thonotosassa, Florida
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Posted: Jun 15, 2011 - 08:02 AM
Thanks for the info, seems there is lots more to windows than just sticking glass in a hole!
I'm in a cold climate, we use double or even triple glaze by code, argon is an option. I had doubts as I had heard that the argon all leaked out within 2 years. The manufacturer told me nowadays it's good for 10+.
You're right, how would a person ever tell if there was any in there or not. Maybe they just charged me a bunch of money & put plain old "air" in! The newb gets fleeced, again.
We use the heat reflection on the inside, to keep heat in, as we heat more degree days than we cool. This take advantage of passive solar heating. Houses are also designed to have no, or very small north facing windows, the opposite of what a hot climate would want.
The thread made me do some reading, I'm now better informed on what to use where, especially with regards to 5200.
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Posted: Jun 15, 2011 - 03:02 PM
Wow this topic has meandered a bit...
The general consensus however appears to be as follows
DO NOT USE 3M 5200 if I EVER plan to remove these fittings.
Use butyl tape for above the water line fittings which beach cats really don't have many/any of.
Use silicone sealant on below the water line fittings. -
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Posted: Aug 03, 2011 - 08:28 AM
Sorry to dredge up a dead topic but I wanted to provide a quick link to a current related thread for those who may find this is the future. DO NOT USE 5200 to bed cross beams or you may have serious trouble as described in http://www.thebeachcats.c…c/12813/start/0#pid30353
Thanks for all the advice guys. Had you not advised me otherwise I would have duplicated FA1321's problems. -
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Posted: Aug 05, 2011 - 11:47 PM
Sorry, I'm not trying to high jack your thread, but wanted to ask, what's so bad about an adhesive that adheres to stuff? I'm in the process of putting my Sol Cat back together this weekend and was planning on using 5200 on all of the fittings. It would seem that there is plenty of experience on the forum that say it would be a bad idea, but i don't understand how a product is supposed to seal your fittings properly if it doesn't stick like heck. I'm a total noob here, so just trying to understand what the ideal bedding compound is supposed to do... BTW I just painted the hulls and spent 40+ HRS removing all of the silicone the previous owner thought would be a brilliant idea to use all over the damn hulls. So silicone is not in the cards.
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Jeremy Hales
1974 SOLCAT 18
Salem, OR
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Posted: Aug 05, 2011 - 11:56 PM
All the good marine adhesives "stick like heck" but it's a difference between being really difficult to remove and virtually impossible. No matter how much you think something will never have to be taken apart again, it probably will.
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Damon Linkous
1992 Hobie 18
Memphis, TN
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Posted: Aug 06, 2011 - 12:39 AM
Gotcha. So a good adhesive is one that will stick well but let loose when you need it to and not be destructive to your boat. Looks like I'm in search of some different bedding compound for my cross bars tomorrow. Thanks for the reply.
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Jeremy Hales
1974 SOLCAT 18
Salem, OR
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Posted: Aug 06, 2011 - 09:34 PM
I was intending to use 5200 as well until advised otherwise. Wound up using marine silicone. I have no intentions to paint but I do intend to respray gelcoat at some point. I know using silicone has added a ton of prep work to get ready for gelcoat but I didn't trust any of the other options availiable at the time.
Damon- What are your fittings bedded/sealed with?
