I am considering building a plywood skiff(screw & glue), using a high quality ply such as Meranti. I have also been considering putting 2 or 3 coats of West System Epoxy on the completed hull. My thinking is that it will act as a moisture barrier which will lessen the need for painting every season and add some strenght/rigidity to the hull. Having never done either of these things before, I am thowing this out for some suggestions/opinions! (help)
Yes you should coat ALL wood surfaces with epoxy! 2-part marine epoxy (like West, System Three, etc) will break down over the long term if UV rays are allowed to hit them directly. A nice coat of paint will keep your boat looking good and your epoxy strong. Let us know which design you're going to build. Matt JEM Watercraft http://jem.e-boat.net
ReplyDeleteYou are on the right track. Epoxy is your friend. You can also glue it up with epoxy. Some believe the screws become redundent and remove them after the epoxy sets up. Others prefer to use both with the idea that the screws will hold it if the epoxy gives. I wouldnt say the UV breaks down the epoxy as much as it just becomes cloudy and less attractive. I use West System 207 Special Coating Hardner as a base coat under the bright work. Followed by several coats of a good varnish or poly with UV protection. Regular epoxy under paint. Greg Rossel says a boat that is both painted and varnished is much more handsome then one that is just painted or all varnish. Frankly, I agree with him. Let us know how we can help...
ReplyDeleteThanks for the reply! I intend to paint, and would entertain something permanent, possibly mixing something in the epoxy. (not crazy about painting)
ReplyDeleteI am considering Old Wharf Dory's Lumber yard Skiff either 16' or 20'
ReplyDeleteHow do you apply epoxy to an entire hull? I haven't started to build yet - still deciding on which to build. I plan to use plywood and was going to cover the exterior hull with fiberglass. If I can just coat both sides with epoxy, it might be a little cheaper. Could someone describe the process?
ReplyDeleteThanks!
I disagree.... I purchased a 1950 Chris Craft. One of the former owners had covered large sections of the cabin with epoxy and over laid it with fiberglass cloth. Every place I found this the wood under it was rotten. This stuff pealed off like plastic wrap. Except where the wood was rotten, no wood came off with the epoxy. There were no signs of the wood being rotten when the epoxy was applied. MOST epoxy is very thick and it sits on top of the wood. It clings like paint does. Until a year ago I was very turned off to epoxy, but then I ran across somthing new. A company called "Smith & Co." makes a water like epoxy that soakes into the wood. It wicks in just like water does. That means it's inside the wood not just sitting on top. They call the product "Clear Penerating Epoxy Solution" or "CPES". It is used to repair or stop rotting wood and it make paint and varnish stick better and stops the wood from soaking up water. The thick epoxy like "The West System" only prevents water from getting to the wood. I guess the main difference is CPES get into the wood and West sits on the wood. West system works well as a glue. If you need to stick things together or fix a broken part it's great, but I would never use it as a water barrier. CPES is not a glue, but it is a great water barrier. I have tried both and I will take the CPES every time.
ReplyDeleteYou can just coat all plywood with 2 coats of epoxy. But make sure you use thick enough plywood. Apply with brush, roller, squeegee, etc. I use a window washing squeegee to minimize waste and reduce sanding time. My rule of thumb is: 1/4" for only fiberglass taping seams, 3/16" if you're covering the outside of the hull with fiberglass, 1/8" if you're covering both sides with fiberglass cloth. 1/8" still may need further bracing in some areas. Depends on the design. Also, 2-part marine epoxy does not like direct UV rays. Mixing something into it will not provide the protection needed. You have to paint, clear coat, or varnish it. Matt http://jem.e-boat.net
ReplyDeleteI don't think there's any big need to seal the ply with epoxy from a maintenance point of view. You'll probably be taking the boat out of the water in the "Off" season anyway, and scuffing around piers and beaches or rocks will give you enough potentially skin-puncturing scratches that you'd want to do a seasonal touch-up anyway. I'd suggest doing the interior, bottom and next two inches with a sealing coat of epoxy, paying particular attention to the joints/corners. This will minimize damage from water penetration from the inside. On the outside, seal the bottom with a single coat of glass and two coats of epoxy, up to maybe three inches above the chine. Sand all this and paint with an opaque oil-based primer to protect against UV ratiation . Use the primer on all other surfaces, too as a reliable sealer and base for whatever color oil paint you want to use on the boat. If it's to sit in the water extensively, add anti-fouling paint to the bottom up to the waterline only. JR
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ReplyDeleteThree Steps, after finishing the surface: 1. Fill coat: epoxy is squeegeed or painted on to seal pores of the wood, prepare the surface for next skin of glass. Manufacturer will specify temperature, humidity and so on. 2. Glass layer: Within the time referenced by the epoxy manufacturer, lay on the glass and the next coat of epoxy, called "wetting in" the glass. Important to do this soon enough so that the under layer and the bonding layer chemically combine into a solid coat. Higher temperatures will accelerate the cure rates, so applying epoxy at night or otherwise at perfect temperatures is key to a good job. 3. Seal coats of epoxy: However many your plans call for (additional layers of glass, skin coat, etc) all done within the same time constraints of Step 2, for the same reasons. Why you want to avoid pre-finished panels or pre-epoxying your own panels: The plastic resin in epoxy is capable of bonding with itself only while the compounds are still "fresh," that is, haven't set up completely. If you are delayed for any reason, the epoxy will unreasonably continue to harden, and some brands exude a kind of waxy skin that won't bond with a fresh coat of epoxy. As a result, if the previous coat has hardened already, you will need to remove the wax (also known as an "amine coat or blush") with a solvent or with (preferably) soap and water. Then, because the new epoxy still won't bond chemically with the set-up stuff, you have to sand the surface to a foggy, satin sheen to give the new coat a lot of "tooth", so the new liquid coat has a lot of irregular cavities to fill, so it can bond PHYSICALLY , rather than chemically. Granted, sometimes you can't avoid the problem. And also granted, when you have properly sanded the undersurface, the new coat will fill all those sanded scratches invisibly so it will LOOK like a single coat. But it isn't. Most of us just start out early one summer day, and just keep on applying the stuff until we're done. Good idea to order up pizzas and have a cooler full.
ReplyDeleteOkay, I am a little confused. When you say you are putting epoxy on the boat, is this part if the fiberglass process or a seperate coating? I was thinking that you just painted the exterior with epoxy as a sealant. I was looking at the old boat plans on the svenson site (and a couple of others) and they just use paint to seal the wooden boats. I thought that sealing with epoxy would be a good idea, but wasn't sure if I wanted to fiberglass the whole thing.
ReplyDeleteLets clear up this confusion. Yes. You can just paint it and you will see many years of service. Yes. You could coat it with epoxy first then paint it and you will see many more years of service. Yes. You could cover the hull with fiberglass saturated in epoxy. And see even more years of service and some excelent abrasion resistance for the bottom. It's all up to you and how far you want to go with it. Painting? Start with a really good primer. Coating with epoxy? Wash the amine blush with soap and water followed by acetone wipe. Paint with really good primer. Top coat with really good paint. Preferably Marine grade. Yes you can build a boat with cheap plywood. Yes you can paint it with ordinary latex and yes you can get a good ten years service from it. If you coat, glue, and glass inside and out with epoxy, your greatgrandkids will be floating around in that boat. It all depends on the level as to which you decide to build. From: Dragonbane Sent: 5/6/2004 9:42 PM Okay, I am a little confused. When you say you are putting epoxy on the boat, is this part if the fiberglass process or a seperate coating? I was thinking that you just painted the exterior with epoxy as a sealant. I was looking at the old boat plans on the svenson site (and a couple of others) and they just use paint to seal the wooden boats. I thought that sealing with epoxy would be a good idea, but wasn't sure if I wanted to fiberglass the whole thing.
ReplyDeleteI belong to several boat design/building groups (for several years now), and have had discussions with many boatbuilders (probably 100 or more) who have used epoxy successfully in building their boats. Some of these are very experienced boat builders. I would suggest that whoever applied the epoxy to the mentioned Chris Craft applied it incorrectly. Epoxy does not make a hull waterproof it will need painting, so if the Chris Craft was not painted that might explain it. As has also been mentioned on this list, epoxy needs UV protection (paint, varnish, etc.). West System, System 3, Raca, etc. have been used successfully for many, many years in boat building.
ReplyDeleteFrank
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Tony, Hows that Old Wharf Dory Skiff? You ever get that finished?
ReplyDeleteI use epoxy on every boat I build and recomend it to anyone trying to extend the life of an old boat.The bigest drawback with epoxy and plywood is that no matter how thin it is it is only goin to soak in as far as the first glue line.This does not mean you shouldent use it, a plywood boat covered with epoxy is still far superior to a plywood boat without and far stronger.I dont build yaughts or play boats , I build work boats and they need to be strong.
ReplyDeleteA very good plan. There is no doubt that epoxy will aid the life of your boat. If you really want to add strength, you should really put a layer of cloth in the epoxy. The cost of fiberglass cloth is very minimal when you are already using epoxy. What will work very well is a layer of 8-10 oz. cloth applied to the out side of the hull. The method I used on JEZEBEL II was to apply a heavy coat of resin to the faired wood hull, while this coat of resin is still tacky, apply the cloth and another coat of resin. Use a squeagy to remove any bubbles and assure the cloth is tight to the wood and not floating in the resin. When the second coat of resin is curied to a tack free state, mix a third batch of resin with a silica filler to a thickness like heavy maple suripe and apply. Let cure completely and finish sand. Best of luck, CB
ReplyDeleteI agree 100% Canal, I have a habit of assuming because I know something that everybody does so I omited to mention the cloth.As a mater of fact I dont think I would bother going to all that work without using the cloth.The only time ive seen a guy have trouble with epoxy it was without cloth. A colosal mistake of biblical proportions.
ReplyDeleteFunny how these topics run in cycles--I just saw an extended discussion of this at Cedarstripcanoes@yahoogroups.com I strongly recommend the glass with the epoxy--because the glass + epoxy combination on your wooden boat will be stronger than either by itself. First, a Sealer Coat of epoxy should be squeegeed on, using those little plastic squeegees you can get at the auto repair stores for working body putty. This seals the wood, fills any cracks in the substrate, and helps to create a level surface. Sanding this coat within 12 hours will permit both a chemical and physical bond for the next coat. Second, spread your cloth (small boats can get by with 6-oz, but canoes do best with two layers of this weight, & larger boats should go up in weight) over the hull, and resolve any issues about whether it will lay flat or on odd surfaces BEFORE you add any more epoxy. When you're sure the glass is where you will want it, you can start to "wet out" the glass with epoxy. This means "filling the fibers" of the cloth with epoxy, so that it goes through the cloth to the surface below, and (usually) leaves just a hint of the fabric's texture at the surface. Too much epoxy will float the glass, and will lead to inconsistent coverage (stiff and weak spots, high and low areas, mixed glossiness, excess weight and waste). Use a squeegee to initially spread the epoxy and move the glass around the surface. Level out the coverage with a 1/4"-nap foam paint roller (I cut a standard 9" roller into thirds so the pieces fit the small roller handle I use). Third, (and once the wetting-out coat sets) apply the Filling Coat of epoxy, using either squeegee or roller. The object here is to "just barely" fill the texture of the fabric, so the surface is smooth. It will set up naturally glossy. If your cautious approach in this step results in a little of the fabric texture still showing (desirable inside a canoe or small boat hull), you can fill it with an additional coat of epoxy. Finally, finish with primer+paint or varnish over a sanded finish (I use 100-220-400 grits, the final one being wet-sanded). Varnish will fill any sanding scratches invisibly, making the surface glossy and transparent. Why is the combination better? Epoxy by itself forms a "skin" that cures harder over time. Flexing in the substrate (wood) can cause it to crack and allow water penetration Fiberglass, especially cloth, holds the epoxy resin in place in a pourous matrix that binds the sealer coat (in the wood itself) to the glass itself. Glass fiber is very strong in tension, but very floppy by itself; the epoxy stiffens the fiber in the matrix such that any stresses from without are spread through the surface the fabric covers. This stiffness also reinforces the epoxy resin, overcoming the brittleness and cracking. In a small (e.g., thin-skinned) small boat, fiberglass+epoxy on both surfaces (inside and out) separated by the hull, create a "monocoque" structure. The fiberglass is in effect separated by the wood into two layers, which form a continuous "box beam", capable of withstanding a great deal more stress than the wooden structure by itself.
ReplyDeleteI have been using west system epoxies for many years and absolutely love them. I have never had a probelm with delamination or wood rot. As far as the Chris Craft mentioned earlier, it sounds like those repairs were done with polyester resin instead of epoxy. Polyester resin and fiberglass do not bond to wood properly and will normally delaminate in a few years. This also depends on the type of boat and if the boat is left in the water. By type of boat I mean how the boat is used. I have talked to many people about the penetrating factors of epoxy resins. In my conclusions epoxy resins due penetrate the wood somewhat and will make the outside of a hull completely waterproof if applied correctly with fiberglass. However, epoxy resins number one enemy is the sun. You must have a sufficient paint job to ensure that all your hard work will last for years to come.
ReplyDeleteJust wondering if any of you guys are from South Carolina.
ReplyDeleteWe did a sound off thread a while back. Maybe it's time for a new one... JEM is from North Carolina. Greensboro I think...
ReplyDeleteDoes southern Ohio count
ReplyDeleteCB
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