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Bending Resin Coated Plywood
How about this ...IF the resin does crack, consider that noticing it (likely
in a hidden spot) and fixing it later will be a bigger pain later than the original crawling around and coating/painting during the build, when the boat's in it's final shape. I'm not sure I'd personally want to wonder if there was a water-absorbing crack through the epoxy somewhere where I couldn't see it after building. That may be OK with you, for example, if your boat is not kept in the water and always has dry storage ...an occasional trailer sailor for example. That said, many people will fiberglass the wood ahead of time. Wood that remains unbent can be glassed any time and is often glassed ahead of time, e.g. framing or gussets etcetera. Glassing the outside of wood that will be bent, the side of the wood on the outside of a bend, is generally not recommended because it stiffens up the wood and makes it much harder to bend. But glassing the interior face, the inside radius, is just fine. I did this on all the side panels for my current project and it is MUCH easier than glassing after the fact. I do final epoxy coating after the boat is assembled however. It's not that hard to do the crawling around and coating. ...Just part of the job. Have fun! Brian D "Andrew Butchart" wrote in message . .. For my current project - a Stevenson's Weekender - I'm very close to being able to put on the sides. To avoid crawling around inside the boat coating and painting, I'm wondering about doing that before I put the sides on. I'll mask off where the glue joints will be during a trial fit. The sides will be 1/4" luan coated with polyester resin (no fiberglass on the inside). I'll fiberglass the outside after assembly. My concern is whether the resin will be able to take the bending after it sets up, or will it crack? Has anyone else tried to do things this way? I don't really want to crawl around inside the cabin breathing in fumes trying to do the coating. -- Andrew Butchart |
Bending Resin Coated Plywood
Andy,
My personal preference is to use EPOXY, rather then the poly. While it does cost more {actually not so bad when you buy in quantity . . . and not at your local 'marine store'. 3-gallon 'kits' of RAKA cost about $100, with shipping}, your concern becomes a 'non-issue'. From your description, this will be a 'one-time' build and you have a lot of intentions for the boat. Most builders & designers say that the actual hull ply is the smallest portion of the total cost, and one shouldn't skimp on it. You have already decided to save money with your choice of 'substrate', now think of balancing the equation. The sheathing & resin is the actual INTERFACE between you and the 'deep blue'. I do have experience with Lauan as a substrate . . . and the customer's hull was still solid as rock after a rough 7-years. {exterior sheathed, interior only painted} While I don't detect any odor from cured epoxy, there is only a mild one when it is being mixed. For ease of application, in the beginning as well as later assembly stages, I 'paint' the entire sheet with an initial coat of epoxy. I may even thin it a bit for increased absorption. Then parts are lofted, or laid out from templates, and the sheets cut. After trimming to final size, the edges are sealed with epoxy. I happen to like a 'hot' 5-to-1 formulation hardener. What I like about the RAKA Brand is that the 'kits' are based on 'quart volumes' . . . I can order 2 gallons of Resin and 4 quarts of Hardener - a couple of the 'fast' 5-to-1, one of the 'slow' 2-to 1, and one of the others available. This allows me to 'custom mix' a batch depending on the particular project, what I expect the material to do, and the environmental conditions. I find POLY to be 'brittle'. The 5-1 epoxy formulations are 'hard' compared to the 2-1 and 3-1 mixes. THOSE tend to be more 'flexible - which would directly apply to your concern {although as I stated, to me it is a non-issue}. Do some research, then do what ever YOU are most comfortable with. Just make sure you have PHYSICAL ACCESS to every compartment. Screw lids, tops, sides, etc., on but don't glue them shut. That way they can be occasionally inspected, ventilated, and repaired or repainted. Regards & Good Luck, Ron Magen Backyard Boatshop "Andrew Butchart" wrote in message . .. SNIP - a Stevenson's Weekender - SNIP - The sides will be 1/4" luan coated with polyester resin (no fiberglass on the inside). I'll fiberglass the outside after assembly. My concern is whether the resin will be able to take the bending after it sets up, or will it crack? SNIP - -- Andrew Butchart |
Bending Resin Coated Plywood
If you're using lauan and polyester resin, you haven't been listening.
I see bowling in your future. "Andrew Butchart" wrote in message . .. For my current project - a Stevenson's Weekender - I'm very close to being able to put on the sides. To avoid crawling around inside the boat coating and painting, I'm wondering about doing that before I put the sides on. I'll mask off where the glue joints will be during a trial fit. The sides will be 1/4" luan coated with polyester resin (no fiberglass on the inside). I'll fiberglass the outside after assembly. My concern is whether the resin will be able to take the bending after it sets up, or will it crack? Has anyone else tried to do things this way? I don't really want to crawl around inside the cabin breathing in fumes trying to do the coating. -- Andrew Butchart |
Bending Resin Coated Plywood
Jim Conlin wrote:
If you're using lauan and polyester resin, you haven't been listening. I see bowling in your future. That's right! You should be using aluminum and a MIG setup. What!?! You can't afford that?!? Well, I guess you have no business building boats, then! You're only permitted to build a boat if you have the wherewithal to use nothing but the finest and most expensive of materials. That's why we all drive European luxury cars and never THINK of buying a box of store brand cereal. LOOK. We all know that okume/epoxy (or whatever) is a better choice than luan/poly. There's ALWAYS a better option than the way you're doing it. It's about what you yourself are satisfied with, along with what you can afford. I drive a 23-year-old toyota, I buy food with the same name as the store I buy it in, and I build small boats out of whatever's cheapest. Also, I do not bowl. I'm too busy messing about in my (apparently) non-waterworthy vessels. Which have yet to fall apart, leak, sink, or rot. YMMV, Chuck |
Bending Resin Coated Plywood
Unlike boats, when a car fails, you can usually get out and walk.
"Chalatso" wrote in message ... Jim Conlin wrote: If you're using lauan and polyester resin, you haven't been listening. I see bowling in your future. That's right! You should be using aluminum and a MIG setup. What!?! You can't afford that?!? Well, I guess you have no business building boats, then! You're only permitted to build a boat if you have the wherewithal to use nothing but the finest and most expensive of materials. That's why we all drive European luxury cars and never THINK of buying a box of store brand cereal. LOOK. We all know that okume/epoxy (or whatever) is a better choice than luan/poly. There's ALWAYS a better option than the way you're doing it. It's about what you yourself are satisfied with, along with what you can afford. I drive a 23-year-old toyota, I buy food with the same name as the store I buy it in, and I build small boats out of whatever's cheapest. Also, I do not bowl. I'm too busy messing about in my (apparently) non-waterworthy vessels. Which have yet to fall apart, leak, sink, or rot. YMMV, Chuck |
Bending Resin Coated Plywood
Jim Conlin wrote:
Unlike boats, when a car fails, you can usually get out and walk. Sufficient and properly distributed floatation goes a long way toward easing my mind. That, and several years as a lifeguard, should save me if my canoe sinks out from under me in the three-foot-deep backwater where I fish for bass. Yes, if I were building boats for use in more difficult/dangerous waters than the Ohio River and its tributaries, I would definitely invest in better materials. I can completely understand and appreciate the point you're making, and it is a valid one. Chuck |
Bending Resin Coated Plywood
"Andrew Butchart" wrote in message
. .. For my current project - a Stevenson's Weekender - I'm very close to being able to put on the sides. To avoid crawling around inside the boat coating and painting, I'm wondering about doing that before I put the sides on. I'll mask off where the glue joints will be during a trial fit. The sides will be 1/4" luan coated with polyester resin (no fiberglass on the inside). I'll fiberglass the outside after assembly. My concern is whether the resin will be able to take the bending after it sets up, or will it crack? Has anyone else tried to do things this way? I don't really want to crawl around inside the cabin breathing in fumes trying to do the coating. DON'T!!! Polyster will fall off. It does not stick to wood well, the slightest stress will separate it from the wood. Use epoxy. I once made a mistake to join two pieces of wood with poly/glass. It dit not hold, I could peel it off clean. You will NEVER be able to peel off epoxy/glass without tearing wood fibres. Meindert |
Bending Resin Coated Plywood
Meindert Sprang wrote: DON'T!!! Polyster will fall off. It does not stick to wood well, the slightest stress will separate it from the wood. Use epoxy. I once made a mistake to join two pieces of wood with poly/glass. It dit not hold, I could peel it off clean. You will NEVER be able to peel off epoxy/glass without tearing wood fibres. Meindert Thank you everyone for your input. I will probably ignore the advise to throw away my remaining resin and spend 3 times as much for epoxy and run the chances of developing an alergic reaction. PLEASE - the whole polyester vs epoxy controversy has been done to death. I know - I've been part of it on this forum for years. I had hoped that this thread wouldn't re-ignite it but it seems that it has. I went into the project fully aware of the impact of my materials choices. I will however plan on putting the panels in place before coating them - reducing the chances of resin failure. Andrew Butchart |
Bending Resin Coated Plywood
Andy,
I'm sorry if 'we' wasted your time. Especially if you already knew the answer !! The entire discourse could have either been avoided, or taken a different tack, if you had mentioned this fact . . . up front. As an engineer {and a C.P.A. - 'Certified Pain in the Ass' per my wife} my first thought, when someone ASKS ME a question, is that they want an accurate & correct answer. It has taken me YEARS to realize that they actually DON'T. Therefore I have adopted the 'policy' of . . . 'If you don't like the answer . . . DON'T ASK the question !!' Regards & Good Luck, Ron Magen Backyard Boatshop wrote in message Thank you everyone for your input. I will probably ignore the advise . . .. SNIP I went into the project fully aware of the impact of my materials choices. SNIP Andrew Butchart |
Bending Resin Coated Plywood
Ron Magen wrote: Andy, I'm sorry if 'we' wasted your time. Especially if you already knew the answer !! The entire discourse could have either been avoided, or taken a different tack, if you had mentioned this fact . . . up front. snip Sorry about the confusion. I had thought that my question was about whether a coated 1/4" panel could be safely curved around the hull or whether it would be too stiff or brittle. I didn't think that my choice of resin was part of the question although I did mention it because it was pertinent. I did sort of get an answer in that with the poorer adhesive qualities and higher brittleness of polyester that there was a risk of it cracking. Andrew Butchart |
Bending Resin Coated Plywood
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Bending Resin Coated Plywood
Andrew Butchart wrote: [SNIP] My concern is whether the resin will be able to take the bending after it sets up, or will it crack? Has anyone else tried to do things this way? [SNIP] Dear Andrew, Whether the resin will crack depends on how thick of a coat you decide to apply, and how much you're bending the panels. If I were you, I'd coat the inside of each panel before putting it on during the "tacky" phase of curing. If it does crack, you'll have to seal those cracks while crawling inside the boat. Hey, at least you won't be doing the whole job from the inside. Mind you, if you're building a boat that'll spend most of its time out of the water, I wouldn't bother coating the inside with poly. I've seen many interior poly coatings (especially the thicker ones) unstick from the plywood, yet stay in place, retaining dampness between it and the wood. If I were you, I'd just bed my frames properly with either a plastic adhesive sealant (like 5200) or something else that'll prevent moisture from finding its way between frames and hull skin. Exterior house paint would be fine for the interior coating, and you can just slap on another coat when you've scratched the inside. I've seen you on the group for a few years, so I assume you know how to build a "cadillac" boat. The above is how I'd do things if I were building a dinghy on a tight budget. I wouldn't listen to the doomsday prophets, either. Your little boat ain't gonna disintegrate or spontaneously explode into a cloud of wood chips and sawdust, while you're out a-fishing, just because you didn't use top-quality materials. Regards, -Max |
Bending Resin Coated Plywood
wrote in message
ps.com... Thank you everyone for your input. I will probably ignore the advise to throw away my remaining resin and spend 3 times as much for epoxy And what percentage is that compared to the entire boat? and run the chances of developing an alergic reaction. Mmm.... allergic vs whatever you get from inhaling styrene (carcinogenic) fumes..... PLEASE - the whole polyester vs epoxy controversy has been done to death. I know - It is then all the more surprising to see you went for poly..... :-) Meindert |
Bending Resin Coated Plywood
May I call to your attention an earlier post, from the original poster?
I had hoped that this thread wouldn't re-ignite it but it seems that it has. I went into the project fully aware of the impact of my materials choices. Those of us who choose to build with poly do so knowing full well the potential consequences of our actions. We have heard the arguments, perhaps more of them than we care to hear, and will proceed on our decided course, regardless. You are welcome to sit back and smugly think, "Those a$$(#*$* are going to get themselves killed, and I'll be right there to say I told you so", but quit trying to convince us otherwise. FWIW, I use epoxy and poly both, depending on what I'm building. Chuck |
Bending Resin Coated Plywood
I'd advise against applying a resin coating before bending.
1. It might reduce the bending radius for the plywood which might not then bend to the curvature of the hull. It will increase the effort in bending, how much I do not know. 2. Bending will put many tiny cracks in the resin letting in water. I've seen a nice wooden kayak with a thin interior coat of epoxy which was left out all winter. Water worked it's way into the wood under the epoxy. That's extreme. I don't see any problem painting or oiling the inside surfaces. I don't think bending would crack latex paint or linseed oil. I use linseed oil on the intror of my small boats but white paint would lighten up the interior of a Weekender's cabin. Waterproofing might not be much of an issue. It's doubtfull the interior of the boat would be immersed for any length of time. Maybe water lying in the bilges. It would be pretty easy to maintin a finish on the inside bottom of the boat. I don't see any problem with polyester resin. The plywood needs to be clean, and lauan (RONA sells a nice meranti underlayment now instead of the wormy lauan they used to have) is porous and tends to soak up resin nicely. Adhesion should not be a problem. I use polyester to seal the chines on my underlayment lauan and virola (now there's a *really* crappy plywood) boats. Andrew Butchart wrote: For my current project - a Stevenson's Weekender - I'm very close to being able to put on the sides. To avoid crawling around inside the boat coating and painting, I'm wondering about doing that before I put the sides on. I'll mask off where the glue joints will be during a trial fit. The sides will be 1/4" luan coated with polyester resin (no fiberglass on the inside). I'll fiberglass the outside after assembly. My concern is whether the resin will be able to take the bending after it sets up, or will it crack? Has anyone else tried to do things this way? I don't really want to crawl around inside the cabin breathing in fumes trying to do the coating. -- Andrew Butchart |
Bending Resin Coated Plywood
Wm Watt wrote: I don't see any problem with polyester resin. The plywood needs to be clean, and lauan (RONA sells a nice meranti underlayment now instead of the wormy lauan they used to have) is porous and tends to soak up resin nicely. Adhesion should not be a problem. I use polyester to seal the chines on my underlayment lauan and virola (now there's a *really* crappy plywood) boats. I should clarify. I think polyester coatings on plywood are most likely to succeed under three condtions 1. new (clean, dry, etc.) 2. porous 3. rigid I forgot to mention "rigid" in my previous post. I think if the plywood flexes the polyester is more likely to become detached from the hull. |
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