marwen1

My Feedback: (6)

What is the difference as far as "performance" is concerned?

I recently bought some 1/8" ply with a MIDWAY sticker on it. It also stated on the label. NOT FOR AIRCRAFT USE.

If I go to the LHS and buy some plywood, it is usually a so-so birch-ply.

This stuff from MIDWAY is only a FIR or maybe even a SPRUCE ply.

GRANTED, one is a hardwood (needle-bearing) & the other is a deciduous wood (leaf -bearing) (SOFT)

Using balsa for a ROOT rib is not the greatest idea in the world, but I have made it a habit of my own to make load bearing ribs from a ply.

I have to wonder, Is there THAT much difference?

If push comes to shove, I'll cover the soft ply with a light covering of glass.

That will probably OVER compensate, especially if I use a normal epoxy instead of a finishing epoxy.

ANY thoughts?

marwen

BMatthews

What wood is the Midway stuff made from?

Aircraft plywood is made from birch for sure and possibly beech or maple. But the big difference is that aircraft ply is certified to have no voids in it. Voids in the layers from knot holes or mismatched joints create a stress riser that could lead to the part failing in flight. For man powered stuff that is not permissable. For our models we can get away with a small void here and there since we generally overbuild them in the first place.

If it's lumber yard 1/8 then I'm guessing that it's a light poplar plywood commonly known as bending plywood. Either that or it's plywood intended as more or less a paneling or veneer for use over some other base structure. If that is the case then one side will look lovely but the other may well have lots of knots or other blemishes in it. But as you say it'll be fine for what you're using it for.

jetpack

My Feedback: (1)

There is also the number of plys to be concerned about. LHS is all three ply. Aircraft grade is usually five ply. I haven't been able to find anything under 1/8" thicknesses in plywood at the lumber yards. Aircraft grade can go all the way down to 1/64" three ply.

There is a product called Lite Ply which is Poplar or Aspen, a soft wood. Birch is more common though...its more stringy and stronger. There is Maple and Oak also that I know of but considered a veneer I believe and only available in a narrow range of size.

I am still studying up on plys since I'll be choosing my own wood this time on a 3.5 powerboat hull. I'm finding it hard to come up with the thin stuff that has any choice in final veneer for the outside, like mahogany for example.

Bob Laine

My Feedback: (91)

When you read a sticker that say's "not for aircraft," the sticker is really referring to "Full Scale Aircraft". (not RC aircraft) I use Luann, (interior door skins) 3 ply all the time for my scratch building. A little heavier, but works just as well as the so called "Lite Ply," sold in hobby shops. And a whole lot cheaper. I always use mo normal building techniques when using this material, and I've never had a problem that could be contributed to the plywood.

Walt Thyng

My Feedback: (9)

The alternative plys (luan, lite, etc) work well for almost everything, but landing gear supports and motor mounts (firewalls). I use a lot of craft store lite ply by Mid-west as I got it on a 60% off sale at Hobby Lobbby (the craft store) and basically bought out their entire supply. It wasn't supposed to be on sale, but the clerk insisted it was. Got a lot of balsa, too.(-:
Walt

marwen1

My Feedback: (6)

Yahoo! Good stuff there Walt. Ya gotta luv it when they insist on giving you the kitchen sink!

Yea! That MIDWEST display is only a fir ply so "just-in-case" , I think I'll make that rib install with some epoxy.

BRUCE: Oh how right you were when you asked me about that AIRHOPPER and retaining my interest in it for SO -o - o - o long.

I got it to the point where I have only the left half of the wing extention to build then I found that my alignment for the full flying stab was out by about a 1/16" It all went together really nice. and I got a LOT of up/down travel but what I really don't want is my maiden flight to be rolling all the time.

For now, I'll just sit it on the back burner. I didn't get any flying in last season 'cause I was doing all of that building.

Too, my arthritis was really bitin' me pretty hard. I finally went back to my specialst and he made a couple of changes in my meds. HOLY COW! I havn't had ONE day of arthritic pain now in over 4 months.

So,,, I'll do a fairly quick build on Laddie Micalowski's ARROW (I think I spelled his name wrong)

I've done enough DELTA wings in the past few years. HIs current plan is for a 44.5" WS. He calls for a .40 engine. I don't think that's enough power for that, is it? Most of his stuff is PUSHER PROP but this is a TRACTOR. I'm not even sure if that is an issue for power! ?

I was thinking of maybe a .60 or even a .90 range. What do you think?



marwen1

Dr1Driver

You can find MidWEST plywood displays in both LHSs and craft stores. It's the same wood. The wood is labeled "not for aircraft use" to prevent someone from using it to build a man-carrying airplane. Special wood must be used for that purpose.

Not all LHS wood is 3-ply. Thicknesses of 3/16 or more are usually 5-ply. "Lite-ply" is 3-ply but you usually don't see it in the thicker sizes, i.e. 1/4" and up.

For our purposes, the type of wood used isn't that critical, since as stated, we overbuild.

Doorskin can be used in place of Lite-ply. Since they are heavier, there's no gain, unless you use a LOT of that size. Then you save $$.

Dr.1

mrgman57

My Feedback: (2)

for building planes ive been useing baltic birch it can be found at cabinet supply stores in 5ft by 5 ft sheets 1/8 sheets sell for under 11.00 a sheet & are as good as most kits ply im in pittsburgh if anyone needs any

marwen1

My Feedback: (6)

YOWSA! That's right. As an old cabinetmaker, I should have known that>

If I recall, I used to buy 1/2" x 48" square and I made my drawers out of it. I just never thought that it was available in 1/8" thicknesses.

marwen1

CoosBayLumber

My Feedback: (1)

We have a standard plywood (only) place near here, and the clerk was knowledgible as to various grades of plywood. Last year asked him to supply me with some aircraft quality 1/16", 3/32" and 1/8" sheets.

No can supply anymore.
For it is not made in the U.S.A. anymore.

It is all imported, mainly from Finland, and is now in metric equavalent thicknesses. The three ply, or lite ply is made in U.S.A. and in fractional sizes. The imported metric plywood will come with a F.A.A. certification paper if bought in quantities greater than 50 sheets. If less than, it comes with Finish plant sticker usually in red. I have been finding the Finish made plywood to be marked for fractional and metric on occasion, but when you measure with a calipers, it is metric and a bit thin too.

This plywood place has same vendor who supplies to Aircraft Spruce of Corona Calif. and a few of the model wood suppliers. Apparently there is not a big market for the sheets, thus only a couple of wholesalers and importers out there, and all the retailers go to the same few. So they all know one another.


Wm.

mmattockx

Is this a 3 ply equivalent to lite ply? Or to the higher strength 5 ply "aircraft ply"? I like the price depending on what it weighs and it's strength level. Pittsburgh is a bit far for me to drive...


Mark

marwen1

My Feedback: (6)

Hi Mark

The overall quality of the baltic circh , etc. is really good,

Back in my cabinet making days in COW TOWN, I would buy it in 1/2" thickness for drawer sides. I think I's just use a luan or something for the bottoms.

The finish on it is also very good.

marwen1

Balsa Shavings

[font="Verdana"]I use that 1/8" ply from the local craft stores all the time in my airplanes, it works great. I even laminate it to make firewalls, in up to .60 power planes, never had one fail yet.[/font]

BWooster

Marwen,

Look at www.windsorplywood.com . As much Baltic birch plywood as you need. Look at page 35 of the catalogue. There are three stores in Winterpeg.

marwen1

My Feedback: (6)

Oh yea! There is one about 3 km from me. They are HUGE in that dept. I never realized though that they sold a true AIRCRAFT PLYWOOD.

THANKS

marwen1

jetpack

My Feedback: (1)

A harder task is finding thin (1/32 - 1/16 inch) plywood with one or two sides finished with exotic veneer like mahogany.

I build boat kits which already have one side as mahogany, but starting to build my own now and would like more choices of wood to finish the decking with other than fir or birch.

So far my results only turned up veneer suppliers, where its a single small sheet of wood used mainly for inlay work I imagine, or finding it in larger sheets but then becoming too thick to use as another "ply" if I were to use it as a skin.

Any suggestions on this topic would be appreciated also.