ByLoudDesign

I am trying to find out ther various weights and strengths of the plywood we use for model building and designing. The plywoods I am interested in are Lite-ply, A/C ply and Birch ply in thickness of 1/4" or less. Also would like input about the issue of the burned edges! One cutter will tell you it "really burns" and another will tell you "proper speed and wattage only causes exceptable burning". Then there are the modellers that say you have to sand all the edges. If it was like scale from a plasma torch I can see it, only if it effect the bond you need. Any help will GREATLY be appreciated!

Charlie

Adibac

Dont really know the exact figures on the weight, but here goes my 2 cents....

Lite-ply is usually made from poplar, and will be the lightest, but you sacrifice strenght.. for small non aerobatic aircraft, it will work ok as will as for non stress areas...
AC ply and Birch are both made from Birch laminations, the difference is the quality of wood and number of plys in them. AC ply will have the highest number of laminated plys and only use top grade birch...
weight is about the same, unless you compare a 3 ply lamination against a 5 ply lamination in which the 5 lamination will be a tad heavier, 5 laminations will be of superior strenght also.... AC ply is to be used in extreme stress areas of large planes, for the rest you can use normal birch ply.... I hope this made sense......

the ammount of burning a laser creates depends on the power, to cut 1/4 ply you need at least an 80 watt laser cutting pretty slow, this does not mean you cant cut with a less powerfull laser, the only thing here is that you will need multiple passes, and here is where the real bad burning originates...

On a good laser cut part, i would recommend only a light pass with sandpaper....

hope this helps

rgunder

Hi Charlie,

Adibac did a great job of explaining some of the differences between the different play options. From a laser cutting point of view I will add only one thing to round out his explanation - and that is glue type. Aircraft grade ply uses an "exterior-grade" glue, whereas birch ply tends toward "interior-grade" glues (although there are some varieties of birch ply with exterior glue). The reason why this is important for laser cutting has to do with the way that the laser interacts with the glue. Exterior grade glues require far more power to cut through than interior grade glues. Because of the heat generated cutting through exterior grade glues, aircraft grade ply tends to have more edge burning than an standard interior grade birch ply of the same thickness.

Hope that helps.

Cheers!

Rich Gunderson

rgunder

Oh, and I forgot to address the sand vs no-sand issue. On aircraft grade ply, if the edge will be part of a joint, then I think it is not a bad idea to lightly sand the edge before bonding. For balsa, lite ply, and birch ply, I generally do not bother to sand the edge before gluing.

Rich

ByLoudDesign

Thanks, Adibac and Rich. I guess in the end the trick then is to find a cutter that know what he is doing!

Campy

My Feedback: (1)

As for light weight ply - in NON -STRESS locations make your own balsa ply.

I make up 12"x36" sheets of 1/8" "balsa ply" using 2 1/32" pieces of balsa with a 1/16" balsa sandwiched between them. I use wood glue (Titebond) then weight everything down for a couple of days.

I use this for fuselage formers and in other NON-STRESS areas that call for light ply. It is more expensive to do this then to buy light ply, however, my balsa ply is NEVER warped and is lighter in weight than light ply. For stress areas I use aircraft ply (firewall, wing joiners, etc).

flipstart

Amen on what Campy says-I was tired of the crummy lite ply that is available-so on my last scratch build of a 1/6 scale TA-152, I laminated balsa to use as formers, works well and I was pleasantly surprised how much weight was saved. Doesn't sound like much but as they say-watch the grams and pounds will take care of themselves. (16 formers with 3 being a/c ply).

WhiteRook

My Feedback: (38)

ID like to chime in and say that aircraft grade ply is a bear to work with , its so tough.
poplar ply is like balsa compaired to it, but the A grade is stronger.its only as strong as what its glued too , and its so dense you have to rough it up to get the glue to penetrate it. I use it
only in high strength areas , id go with the pop in other places.

ByLoudDesign

Thanks all, even got a call from Pat at lasercutusa.com, we had agreat discussion. Now I know enough to be dangerous! LOL
Charlie

marwen1

My Feedback: (6)

One thing that CAMPY forgot to mention in the making of his own ply was that with each sheet, the adjacent sheet should be applied with the grain in a 90Ëš direction. This is where youe strength comes from.

Up here in Canada, we have a 3 ply BALTIC BIRCH that is only available in certain wood distribulers. A 5' x 5' sheet of .125" runs $18.99. A .25" sheet of the same size runs about $29.99. Absolutely ZERO holes in the ply.

Now, if I go out to a LHS, that would cost me a small fortune. If, for any reason that I want increase its strength, I simply apply a light coat of fiberglassing on each side.

marwen1

ByLoudDesign

I was very formiluar with A/C and marine plywood, both useing waterproof(Politically correct ~ water resistant). But the plywood made for the model indrustry was a different story! Thank all!
Charlie

marwen1

My Feedback: (6)

As I recall, the retailer up here in CANADA claims that their 3 ply BALTIC BIRCH is manufactured in FINLAND.

marwen1

rgunder

All,

I have been wanting to start a blog on my website for some time now, and this seems like plywood makes a good first subject. I wrote up an article on plywood and posted it there last night. Granted, the site is still very rough and does not link well to the parent site, but it is a start. Please see the article at [link=http://www.gundersonaerodesign.com/blog]www.gundersonaerodesign.com/blog[/link].

I hope you find it useful, and there will be many more articles, not to mention site improvements, to come.

Cheers,

Rich

karolh

That made very interesting reading ... good article.

Karol

ByLoudDesign

Rich
Thanks for taking the time to do that it fills some of the voids in my understanding of plywood!
Charlie

rgunder

Karol and Charlie,

Thanks for the kind words - I am happy to do it. In fact, I am currently looking for some other good topics to write on, so if you have any good ideas, please feel free to suggest any.

Cheers,

Rich

ByLoudDesign

Rich
I have been collecting data to put together a hardware size and thread shart, but do not have it all yet. Missing the drill sizes for the metric sizes Have the Englist, and hope to start a RC Builders Data Certer on my web site!. How about bearing the facts about the digital / anolog servo world!
Charlie.

rgunder

Sounds like a useful set of data Charlie! I might have a metric drill size chart lying around that I can send a scanned copy of, no promises but I will look around.

I like the idea of an analog/digital servo article. I will put some thought into that tonight and see what I can come up with.

Cheers,

Rich

ByLoudDesign

Great! Thanks Rich