Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
Search
Gelcoat, epoxy & glassing over a thru hull
|
Hello, I know just enough to be dangerous! I removed an old depth sounder and have a nickel sized hole in the bottom of my boat below the waterline now. All I need to do now is glass over the hole. I am familiar with the basics of the 12-to-1 bevel, building up the layers, etc.? But.. the devil is in the details. I have an early model T27, Hull #154, 1965. My understanding is that these boats are polyester resin. It is generally safe to put epoxy on polyester, but not the other way around. And, apparently, gelcoat is a type of polyester resin. So.. now I have questions. Did my boat originally have gelcoat under the bottom paint? The top-layer of bottom paint is an ablative paint - micron extra. But I don't really know what is underneath. Maybe I don't care? Maybe I just use epoxy and glass over hole. And then use whatever primer and other treatment interlux says to use before applying micro extra to the patch? My concern is that if someone later tried to reapply gelcoat to the bottom, there would be a place where it wouldn't work right? Or maybe my boat never had gelcoat below the waterline? Or perhaps it is absurd to think anyone is ever going to try to reapply gelcoat to the bottom? Also, I noticed that after the fiberglass is epoxied in place, people usually apply a layer of fairing compound over the epoxy to smooth things out. Perhaps the gelcoat would be able to adhere to the fairing compound masking the epoxy<->polyester incompatibility issue? It seems, at the very least, that if I use epoxy for the patch, that I won't be using any gelcoat on top of the patch regardless of what is on the rest of the bottom. I guess that is not an issue? What if I was patching above the waterline and wanted the best matching finish? Would I want to use polyester resin instead of epoxy so that I could have matching gelcoat applied? Does my boat even have gelcoat? My hull is a standard blue color, As noted, I know enough to know there could be an issue, but not enough to know if there is an issue. Thanks, - jeremy |
|
RegJust use epoxy and glass. Probably thicken it with fumed silica, it makes it easier to build layers, you can fair the thickened epoxy somewhat. Then a final two coats of epoxy to seal everything. You can run a bit of epoxy over the lip onto the original bottom to seal everything.? Just sand it enough to give it tooth. You need to see what is above the waterline and determine if it's been painted over gelcoat. If you're going to paint anyway I would just use epoxy mixed with fumed silica and microballoons for filler, then a final couple coats of epoxy. Obviously you would need to sand and prep first. If you want to stay with gelcoat you probably should get someone to look at it first. It probably won't match but that's just a quick opinion. All of this is just one man's opinion obviously.? Your boat will likely never have gelcoat reapplied to the bottom. There isnt an epoxy polyester incompatibility issue as long as its epoxy over polyester.? Epoxy sticks well. Really well. Just sand first. If you use a ready mix fairing compound,? make sure you can use it below the waterline. Really no need if hole is small, just use fumed silica to thicken and fair it well before it sets up. If you must use a fairing compound then topcoat it with epoxy.Regards, Rob. (Early T27 I haven't seen yet because I'm still filling holes in my Allied.)
|
|
Hi Jeremy,
My understanding is that these boats are polyester resin. It is generallyMore or less. Polyester bonds to polyester better than it bonds to epoxy, but epoxy bonds well to both. So.. now I have questions. Did my boat originally have gelcoat under theProbably? General process was to spray mould release in to the mould, spray gelcoat onto that, let it kick, then start doing layup. That's an old technology. Glossy durable marine paints are relatively new. Maybe I don't care? Maybe I just use epoxy and glass over hole. And thenThis is all second hand so grain of salt, but with polyester resin, when done badly, it was prone to forming blisters, and some of the barrier coats (which are epoxy) became popular in response to that. For one small bit of paint on a patch of epoxy, I wouldn't go buy big jugs of barriers and primers and stuff. Just slap some paint on. Then next time you have the bottom painted, that'll be sanded with the rest and done up the same. My concern is that if someone later tried to reapply gelcoat to the just says "apply over clean, dry surfaces. Remove all grease, wax, or oil... All surfaces must be sanded". No mention of epoxy or polyester. So, shouldn't be a problem. Since gelcoat bonding isn't an essential part of the structure, it may just matter less. But realistically, no one is going to gelcoat their bottomsides. It's done in the factory because it's easy to do so and is attractive, but redoing a surface with gelcoat is a lot of work so you probably aren't going to do that somewhere where you can't see it. I noticed that after the fiberglass is epoxied in place, people usuallyDon't think of epoxy and polyester as completely incompatible. If you're repairing a hole in the hull as you are now, you want the best bond possible. Epoxy stickers to polyester better than polyester sticks to polyester, but people repaired fiberglass boats with polyester for ages. It's just a matter of using the best reasonable thing available. Also, catalyzing epoxy is a lot easier and more foolproof than polyester. What if I was patching above the waterline and wanted the best matchingNo, use epoxy. Does my boat even have gelcoat?Not any more, not unless you stored her indoors for all of these years. Maybe some hints of it under the paint somewhere. If surfaces are dry and chaulky and porus, that could be very old gelcoat but most likely, your boat has been painted over and over again. And I'd love to have new gelcoat on the topsides... I think. How long have you had this boat? There's an instinct to address cosmetics first, but there's often a whole bunch other work that needs to be done. Generally when people fix up a classic car, the paint is the last thing that happens. If you haven't already, I'd look at mast step, chainplates, keel bolts (are you post switch to fully encapsulated keel? one of the docs on the Yahoo site will tell you), centerboard pivot pin and uphaul, thru-hulls, and deck hardware bedding (should be securely glued down even if you take all of the bolts off, to prevent water intrusion in to wooden cores) first. There should be no rust on any of the stainless steel rigging too. And make sure all of the tubing including the centerboard uphaul are well bedded to their fittings and double hose clamped. If your chainplates are encrusted in fiberglass (on the inside of the boat, below the deck), they need to be cut open and redone. Since it sounds like you're out of the water right now, now is a really good time to look at centerboard stuff, and thru-hulls and how hoses are attached to them. We were just talking about Dynema line for the uphaul since it doesn't rust and give out, and centerboards suddenly swinging free is bad news. Often centerboards and pivot pins have problems when inexpected. And also have a qualified marine person inspect your rudder if possible. At this age, the stainless starts to corrode, and water gets in to the fiberglass body, and all heck breaks loose. I wound up on the rocks after my rudderstock collapsed (also 1965 but one of the rare west coast built Tartans) and some of the local club's similarly aged Pearsons have had various rudder failures. One rudder, the fiberglass broke free on one side and the internal metal skeleton came out. Water inundation corroded the metal skeleton and the attachment broke. I know it's annoying amount of fussy stuff to deal with... and that's just the critical stuff =| Cheers, -scott |
|
Oh, and one other thought... they make gelcoat repair kits that
toggle quoted message
Show quoted text
are just small amounts of polyester/styrene and its catalyst, and pigments, and a few odds and ends to go with. If you wanted to play with it and test it, the whole kit goes for about $50. Slap some on epoxy yourself and see how you feel about how strong it sticks. I haven't done that myself but I'm curious to. -scott On 0, "Scott Walters scott@... [T27Owners]" <T27Owners@...> wrote:
|
|
Hi Jeremy, If you don't want to do all this fiberglass work; A simple solution is to put a thru hull fitting in and cap it off.? My 2 cents. Dave T27 #427?
On Thursday, August 15, 2019, 08:34:32 PM PDT, Jeremy Shaw jeremy@... [T27Owners] wrote:
?
Hello,
I know just enough to be dangerous! I removed an old depth sounder and have a nickel sized hole in the bottom of my boat below the waterline now. All I need to do now is glass over the hole. I am familiar with the basics of the 12-to-1 bevel, building up the layers, etc.? But.. the devil is in the details. I have an early model T27, Hull #154, 1965. My understanding is that these boats are polyester resin. It is generally safe to put epoxy on polyester, but not the other way around. And, apparently, gelcoat is a type of polyester resin. So.. now I have questions. Did my boat originally have gelcoat under the bottom paint? The top-layer of bottom paint is an ablative paint - micron extra. But I don't really know what is underneath.. Maybe I don't care? Maybe I just use epoxy and glass over hole. And then use whatever primer and other treatment interlux says to use before applying micro extra to the patch? My concern is that if someone later tried to reapply gelcoat to the bottom, there would be a place where it wouldn't work right? Or maybe my boat never had gelcoat below the waterline? Or perhaps it is absurd to think anyone is ever going to try to reapply gelcoat to the bottom? Also, I noticed that after the fiberglass is epoxied in place, people usually apply a layer of fairing compound over the epoxy to smooth things out. Perhaps the gelcoat would be able to adhere to the fairing compound masking the epoxy<->polyester incompatibility issue? It seems, at the very least, that if I use epoxy for the patch, that I won't be using any gelcoat on top of the patch regardless of what is on the rest of the bottom. I guess that is not an issue? What if I was patching above the waterline and wanted the best matching finish? Would I want to use polyester resin instead of epoxy so that I could have matching gelcoat applied? Does my boat even have gelcoat? My hull is a standard blue color, As noted, I know enough to know there could be an issue, but not enough to know if there is an issue. Thanks, - jeremy |
A little under two years. ?
These are on my todo list. In addition to being on the hard, my mast is also unstepped. Though, I am not quite sure how to do some of these things yet. I know that the wood under the mast step can rot -- but how do I see what is going on? The metal plate that the mast sits on doesn't want to budge, though I also didn't force it. I definitely have an external ballast with keel bolts. But.. what I am supposed to be seeing? I can see the top of the bolts in the bilge, but I am not sure that tells me much. Do I need to inspect and reapply a sealant on the outside where the lead meets the fiberglass? Do I need to actually take the keel off so I can see the entire length of the bolts? ?
The boat normally lives on a cradle where I don't have access to the centerboard, but since I am not at my home port right now, I had them set me up high on jackstands so that I can take off and inspect the centerboard. When I put the caps back on in the bilge, do I need to use any sort of sealant to avoid leaks?? ?
Mine were supposedly redone a decade ago -- but they are also still encrusted in fiberglass. I do plan to pull them out and inspect them before I restep the mast. But, I am not sure I am willing to redo them properly them until I am done doing America's Great Loop. I've already been on the hard too long. ?
This is one of my biggest concerns, but I am also not sure how it could even be inspected. I believe that my rudder post is bronze. The inside of the rudder seems to be filled with some sort of cement like substance. - jeremy |
These are on my todo list. In addition to being on the hard, my mast isIf you hadn't posted to here before, welcome! I know that the wood under the mast step can rot -- but how do I see whatThe Tartan 27 Handbook available in the files area of the Yahoo group has some discussion and sometimes illustrations about each of those things. If you've seen that already and I'm repeating stuff you know, I apologize. p.60 has discussion and p.61 has diagrams. It looks like you'd have to pull up flooring to look but I can't confirm. The W.D.Schlock west-coast built Tartans have fiberglass pan in the head and main galley (with a long wooden flooring over the bilge in the main galley), and the pan in the head has an access hatch. The T27Handbook does suggest drilling a drain hole through the mast step so if nothing else, perhaps a fairly large hole would allow you to feel the state of the plywood under the plate. But that doesn't help with the wood the step sits on. Hopefully other people can comment here. Good that you're at least aware of that. Wish so many boats so old without some bits of maintence, I hope you'll forgive me for double checking. I definitely have an external ballast with keel bolts. But.. what I amMain problem with keelbolts is if they start to rust through from water having sat in the bilge. Take the nuts off one at a time so the lead keel is still attached -- but this is also 2nd hand (talking out of my backside). The West Coast build switched to fully encapsulated earlier. Re-assemble with heavy grease or non-permenant threadlock or something else to help keep water out of the threads. Looking at one or two should be adequate. Don't know about the bedding between the keel and the boat. I guess Catalina keels will start to pull free and this isn't a major problem and that seems awfully odd to me. The boat normally lives on a cradle where I don't have access to theI'm being useless again. Had the yard do this for me and didn't ask what they did. They should be NPT threaded which is a plumbing thing designed to be water tight, but maybe ask at the plumbing department of the local hardware store if something should be in there? New caps couldn't hurt either assuming compatible alloys. Putting the centerboard back in is a two person job so don't pull it if you can't bribe help. And if you don't want to mess with the pin, you should still be able to service the uphaul. People sometimes lose their centerboards then are left trying to replace it but otherwise that's less critical than other things. Mine were supposedly redone a decade ago -- but they are also stillInspection is a great idea. I think consensus is that the fiberglass isn't helpful and is counterproductive or cutting them out and checking them is exactly what you want to do. This is one of my biggest concerns, but I am also not sure how it could - jeremyThat design may have saved my bacon. What would be inspected would just be fiberglass pulling away from the metal where the stock goes in to the rudder, and possibily using a moisture meter or drilling an inspection hole to figure out if it is waterlogged. But eyeballing the metal and fiberglass at the top may give a clue on the state of things. If a small flat feeler gauge can be pushed in, that would indicate problems. Awesome to hear that you're out voyaging! All of the best on your trip. Cheers, -scott |
to navigate to use esc to dismiss