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#21
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Poplar plywood
Because of resistance to puncture, isotropic properties and stiffness.
Foam sandwich doesn't work for small boats. To get sufficient resistance to puncture, the skins must have a minimum thickness. For mechanical reasons, we should use tri or quadriaxial while with plywood only biaxial is needed. A sandwich panel made that way would be heavier than a plywood-epoxy-glass sandwich. Once you get around 27', foam sandwich becomes a valid choice. With vacuum-bagging and aramids, we could build smaller units, donw to 20' but the cost would be very high. PS: about poplar, there are no fasteners in our boats . . . -- Jacques http://www.bateau.com "Backyard Renegade" wrote in message Why not make the panels of foam and skins, like vacume bagging? Scotty |
#22
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Poplar plywood
"Jacques Mertens" wrote in message ...
Because of resistance to puncture, isotropic properties and stiffness. Foam sandwich doesn't work for small boats. To get sufficient resistance to puncture, the skins must have a minimum thickness. For mechanical reasons, we should use tri or quadriaxial while with plywood only biaxial is needed. A sandwich panel made that way would be heavier than a plywood-epoxy-glass sandwich. Once you get around 27', foam sandwich becomes a valid choice. With vacuum-bagging and aramids, we could build smaller units, donw to 20' but the cost would be very high. PS: about poplar, there are no fasteners in our boats . . . I know.. I am building one of your boats now... but of course, I will be using no poplar Scotty 8-) -- Jacques http://www.bateau.com "Backyard Renegade" wrote in message Why not make the panels of foam and skins, like vacume bagging? Scotty |
#23
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Poplar plywood
I dunno ...the one and only guy (Homer, AK) I've met that has a lot of vacuum bagging experience, as in "did it for a living down in Florida", said it was not so easy to get right. I only met him just the once, and haven't looked into it at all after that ...figured it might not be worth the effort. What do you think? Brian -- My boat project: http://www.advantagecomposites.com/tongass "Backyard Renegade" wrote in message om... "Brian D" wrote in message news:QWscb.568478$YN5.404597@sccrnsc01... And THAT is probably why I won't be able to find a lightweight plywood for the superstructure of my boat...the trade-offs aren't worth it. Denser is tougher, less dense is ...less dense, and all you get when you buy low density wood. Anyone know of a marine grade foam core hardwood-veneered product? Seems like I saw something like that somewhere. Note: Most of this is academic and just fun to look into. I'm sure I'll end up using standard marine ply of some kind in the end. Brian Why not make the panels of foam and skins, like vacume bagging? Scotty -- My boat project: http://www.advantagecomposites.com/tongass "Backyard Renegade" wrote in message om... "Jacques Mertens" wrote in message . .. We are talking about two different things. The plywood we are testing is not a buck a truckload, it is not plain cheap wood. Poplar is poplar is poplar. Maybe they put some expensive glue or coating on it to dress it up but poplar still has bad qualities, it soaks up water like a sponge and gets soft, it expands tremendiously and distorts, it discolors (turns black with moisture), and it rots easily, does not hold fasteners well, etc. However, it seems that you have long before asking us, made up your mind and used it... So I will leave it alone from here on... Scotty Anyway, I got at least one interesting response about a similar experiment (thanks Paolo) and since I am very stuborn, I will keep testing. What keeps me going is the memory of all the people who were laughing at my first boat designed for Airex. Foam for a boat hull? It will never work they said . . . -- Jacques http://www.bateau.com "Backyard Renegade" wrote in message om... "Jacques Mertens" wrote in message ... The poplar plywood I am testing is listed here as "marine" plywood: http://www.worldpanel.com/eurolite.htm I don't expect much distortion from a 5 ply 6mm ply with melamine glue, saturated with epoxy and fiberglassed. I am playing the devil's advocate here. I keep an open mind about it and I am not ready to endorse it for such applications. I may if my tests come out positive, I may not if I read about some bad experiences. Thanks for your opinions and I would like to read more. -- Jacques http://www.bateau.com Well, I still think it is a bad idea, if for no other reason than that the stuff is a buck a truckload up here in the NE and I have *never* heard of *anyone* using is locally for anything to do with boats... Scotty from SmallBoats.com |
#24
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Poplar plywood
JM, I was considering researching lightweight solutions for the superstructure, not for the hull or structural components. See my boat project web site below. Brian -- My boat project: http://www.advantagecomposites.com/tongass "Jacques Mertens" wrote in message .. . Because of resistance to puncture, isotropic properties and stiffness. Foam sandwich doesn't work for small boats. To get sufficient resistance to puncture, the skins must have a minimum thickness. For mechanical reasons, we should use tri or quadriaxial while with plywood only biaxial is needed. A sandwich panel made that way would be heavier than a plywood-epoxy-glass sandwich. Once you get around 27', foam sandwich becomes a valid choice. With vacuum-bagging and aramids, we could build smaller units, donw to 20' but the cost would be very high. PS: about poplar, there are no fasteners in our boats . . . -- Jacques http://www.bateau.com "Backyard Renegade" wrote in message Why not make the panels of foam and skins, like vacume bagging? Scotty |
#26
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Poplar plywood
You don't have to vacuum bag foam necessarily.
For some interior parts, your cabin and especially for the roof, you could use foam and fiberglass as if it was plywood. -- Jacques http://www.bateau.com "Brian D" wrote in message news:YVOcb.583066$o%2.266323@sccrnsc02... I dunno ...the one and only guy (Homer, AK) I've met that has a lot of vacuum bagging experience, as in "did it for a living down in Florida", said it was not so easy to get right. I only met him just the once, and haven't looked into it at all after that ...figured it might not be worth the effort. What do you think? Brian -- My boat project: http://www.advantagecomposites.com/tongass "Backyard Renegade" wrote in message om... "Brian D" wrote in message news:QWscb.568478$YN5.404597@sccrnsc01... And THAT is probably why I won't be able to find a lightweight plywood for the superstructure of my boat...the trade-offs aren't worth it. Denser is tougher, less dense is ...less dense, and all you get when you buy low density wood. Anyone know of a marine grade foam core hardwood-veneered product? Seems like I saw something like that somewhere. Note: Most of this is academic and just fun to look into. I'm sure I'll end up using standard marine ply of some kind in the end. Brian Why not make the panels of foam and skins, like vacume bagging? Scotty -- My boat project: http://www.advantagecomposites.com/tongass "Backyard Renegade" wrote in message om... "Jacques Mertens" wrote in message . .. We are talking about two different things. The plywood we are testing is not a buck a truckload, it is not plain cheap wood. Poplar is poplar is poplar. Maybe they put some expensive glue or coating on it to dress it up but poplar still has bad qualities, it soaks up water like a sponge and gets soft, it expands tremendiously and distorts, it discolors (turns black with moisture), and it rots easily, does not hold fasteners well, etc. However, it seems that you have long before asking us, made up your mind and used it... So I will leave it alone from here on... Scotty Anyway, I got at least one interesting response about a similar experiment (thanks Paolo) and since I am very stuborn, I will keep testing. What keeps me going is the memory of all the people who were laughing at my first boat designed for Airex. Foam for a boat hull? It will never work they said . . . -- Jacques http://www.bateau.com "Backyard Renegade" wrote in message om... "Jacques Mertens" wrote in message ... The poplar plywood I am testing is listed here as "marine" plywood: http://www.worldpanel.com/eurolite.htm I don't expect much distortion from a 5 ply 6mm ply with melamine glue, saturated with epoxy and fiberglassed. I am playing the devil's advocate here. I keep an open mind about it and I am not ready to endorse it for such applications. I may if my tests come out positive, I may not if I read about some bad experiences. Thanks for your opinions and I would like to read more. -- Jacques http://www.bateau.com Well, I still think it is a bad idea, if for no other reason than that the stuff is a buck a truckload up here in the NE and I have *never* heard of *anyone* using is locally for anything to do with boats... Scotty from SmallBoats.com |
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