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As Mark said, a lot of plywood in hobby sizes seems to be warped. I bought some to replace my Unicorn keel - first from Micromark which was really warped (to their credit, they refunded me my purchase cost) and then a packet of five pieces from a second retailer and most of those pieces were warped as well.

 

When I re-start my Lyme as a scratch build, I'm going to think about MDF.  I don't think it suffers any warp issues, and is incredibly solid.  MDF was used in my Pegasus kit, and it was great.  The only thing I would mention about MDF is that it is very hard to sand yet at the same time can flake if you try to chisel it.

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I get mine in the local Michaels craft store and none of the pieces I looked thru were warped. The had them down to 1/8 thickness.  Saw a couple pieces of 1/16 "airplane" plywood but wasn't too impressed with it. Most of the sheets were 8 x 8 or 12 x 12 with some 4 x 8 (all inches not feet).

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My problem is that I live on a isolated Alaska Island.  I am currently using a piece of standard 3/16th  3 ply plywood scrap from the lumber yard. What any person would call a junk piece of plywood.  It's all I have. I was wondering what I might order for the next time. I saw Birch on a online hobby store. I am just not sure what to use. Plus, any piece of any wood measuring 12 x 24 inches will cost me $19 to have shipped UPS !!!  USPS ships cheaper, but so far all the stores will ship UPS only. The price I pay for living in paradise. 

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Old Man, of the kits I've started so far, for the keel and bulkheads, Caldercraft and Corel used plywood, Amati used MDF, and Model Shipways used basswood for the keel and I think plywood for the bulkheads.  Use whatever is flat and will provide a good solid skeleton for your build.  I don't think you can go wrong with plywood or MDF.  Just make sure that it's pretty solid without any flex.  The Corel bulkheads, for example, I found had too much flex, particularly at the tops of the bulkhead extensions.

 

Even if whatever material you use has more flex than you would prefer, there are steps you can take to minimize any twisting of the hull - filler blocks, braces between bulkheads, etc. help a lot.  I used braces on my Corel Unicorn and the bulkheads and hull were very solid.  The bulkhead extensions, however, still had quite a bit of flex though.

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MDF is hard, I used a sawblade that I wax down with beeswax every 10 or 15 strokes.  Also, the dust is toxic so cut outside, or wear a mask and run a vacuum while cutting.    A scroll saw works well but it does eat the blades, even waxed if you're cutting a lot.  As I recall, I went through 2 blades on my build board.  The problem isn't the wood fibers but the glue binding the fibers together.

 

If you can, check the store where you get your wood and see if they have a small piece of scrap you test with.  

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There are different grades of birch plywood available. I use always aircraft grade plywood which is normally 5 to 10 plys, depending of thickness. Very good flat material, easy to saw, sand, etc, and keeps it's dimensions perfectly. Normally lumber yards sell worse quality board which warps, is not homogenous, etc.

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I'm using boxwood and built in different section. Sometimes pear. But I've noticed that building a keel in one section has a tendency of hogging and then the whole ship is ruined. I think (especially in a humid atmosphere - island Alaska) that the humidity is something to think about. Especially over time.

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I'm using boxwood and built in different section. Sometimes pear. But I've noticed that building a keel in one section has a tendency of hogging and then the whole ship is ruined. I think (especially in a humid atmosphere - island Alaska) that the humidity is something to think about. Especially over time.

I stored some Basswood for about 6 months. Our summer humidity 70-90% ruined it. 

 

 

There are different grades of birch plywood available. I use always aircraft grade plywood which is normally 5 to 10 plys, depending of thickness. Very good flat material, easy to saw, sand, etc, and keeps it's dimensions perfectly. Normally lumber yards sell worse quality board which warps, is not homogenous, etc.

I am looking at aircraft quality Birch Plywood for my next project.

 

My current build I used standard 3 ply lumber yard.  I noticed that when I sanded, I reached the discoloration of the plywood glue. A pink color. Which then required paint.

post-22508-0-15424200-1453225152_thumb.jpg

Edited by The Old Man
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Hello "The Old Man",

 

Birch plywood is fine for bulkheads and strong back. Just get stuff that's flat as others have said. Aircraft grade is nicer to work with, but in the end, what you're using should be just as good. 

 

I'd suggest using something nicer for the actual visible keel, stem and sternpost though. I like to use boxwood for those, even with kits. I've cut off the existing stem and keel of those "all in one" keel/strong back pieces and replace them with boxwood (or pear wood) pieces, built up as with the real ships and nobody can tell the inside is just plywood.

 

Using nice wood for those visible areas will avoid bad looking edges and the wood discoloration you're getting, and would allow you to leave the visible wood natural if you like.

 

Clare

Edited by catopower
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