Plywood choices

[patmat2350]

Every now and then I see a reference to "door skins" (1/8", NOT 1/4", luan plywood) which are supposedly available at Home Depot. I've looked around and NEVER seen these there (except on finished doors), and the lumber guys look at me like I'm crazy when I ask. Anyone know any better?

And after that, anyone know how to get birch aircraft ply that isn't curled up like a Pringles potato chip? Why do they bother making it if they can't make it flat, anyway?

And what about Lite-Ply? Lighter and cheaper than birch ply, but anyone unhappy using it for boat frames?

[Kmot]

I have never seen a door skin at Lowes either.

[patmat2350]

I just noticed that Pat Tritle said that MACK's Lyman kit uses Lite-Ply frames... hmmm...

[Umi_Ryuzuki]

I built my Romani Class light cruiser using the 1/8" door skin.
However, it came from Copeland Lumber supply, and they have since
gone out of business.

[Shaun Hendricks]

I've seen thin skin ply at Home Depot. I'd love to have a Lowes in the area but we don't... :(

Look in their 'countertops' area and underneath their mouldings sections. I sometimes find that they move the laminates around.

The thin skin plys usually don't have the glue on them. I guess they expect you to use contact cement.

[green-boat]

Builders Square when they were around used to sell it. They sold it in 4'X8' sheets. As to who has it now ??????? I haven't seen it at Lowes or Depot, maybe Menards has it. Luan (Phillipean Mahogany) is an open grain wood requiring a lot of filling to get it smooth. I would spend the extra money on Birch plywood, seal it, sand it, done.

I get my Birch plywood from Wicks Aircraft Supply http://www.wicksaircraft.com/
For me they are local (within 50 miles) and I go thru their scrap pile. :D You just can't beat a deal like a $1 a square foot for any thickness.

As for that Lite-Ply, Birch over a Poplar core. I stay away from it, it tends to warp too much. If I was building something where weight was critical, then maybe.

[patmat2350]

Wicks- wow, they have basswood plywood! That must be nice stuff... the shipping would be a killer though...

[green-boat]

If you drive down for the Regatta in September, they are on the way.

[JCJ]

Lowes has it in some locations,
1/8" 4X8 IMPORT HARDWOOD PLYWOOD Item # 95321
and 1/8" 4X8 OAK Item # 95288 .



I'm not sure how to go about getting it if the local store doesn't carry it but I would think they might be able to get it on request.

[Kmot]

Oh my gosh! Thanks JCJ! My local Lowes does not have it but the one across town does!

[toesup]

And after that, anyone know how to get birch aircraft ply that isn't curled up like a Pringles potato chip? Why do they bother making it if they can't make it flat, anyway?

And what about Lite-Ply? Lighter and cheaper than birch ply, but anyone unhappy using it for boat frames?



My experiences with ply..

Home Despot and Lowes grade of ply is 'construction grade' and unless you are building in ply and concrete... or want to build an 'out house' :p then steer clear of these types of ply.

Aircraft quality ply is usually of a lighter grade of timber with less 'plys' than the non-aircraft ply. The only place i have discovered that has the non-aircraft grade of ply, with 5 plys of timber is Michaels... although you have to be selective as some of the sheets they have is warped as its been in stock a while.

I have recently discovered that the LHS carries Sig ply, which is the highest quality i have found so far... highly recommended.. if you can find some.

[green-boat]

Here is something interesting that I found out about plywood. I pulled it off an aircraft construction site. It gets into the different grades of plywood.


Well, my Falco project has begun! I would appreciate some advice on plywood. I ordered (and received) aircraft grade Birch ply from Demel Aircraft up here in Canada. When they delivered it, it had Mahogany OY printed on the sheets as well as Birch plywood. My immediate response was one of concern as you state that Mahogany ply is not to be used on the Falco. I have since learned that the company is called Mahogany OY in Finland, and the ply is aircraft grade birch. My concern is that there is Birch on both surfaces but the centre sandwich is unspecified, and is a dark brown colour. Could this be a Mahogany centre, and if so, is that a concern?

Roger Wright

As the president of your company, I'm sure you can understand the difficulty of being asked to comment on something you've never seen or that someone has not bought from your company! But I'll try.

First, there is no such thing as 'aircraft grade' birch plywood. Instead, there is a specification of the grade, which for plywood made in Finland typically is GL I, GL II or GL III. That stands for Germanisch Lloyd, and it's the split-off from Lloyd's of London during the unpleasantness of WW 1 and WW 2. The specification is for a grade of plywood suitable for marine construction, and it was required by the insurance companies before they would insure a boat or ship made of the stuff. As it happens, aircraft use the same plywood.

Generally, what you want is GL II or "GL 2". The three grades are all made at the same time and in the same process, but it's simply a matter of grading the finished product, with GL I allowing for fewer imperfections in the wood that GL II or GL III. GL II is by far the most common grade and it's all we use. Only occasionally over the past thirty years or so have I heard of someone who had some GL I, and I always had the impression is was more a matter of snobbery than any real understanding of the quality of the wood.

All of our GL II plywood is made by Mahogany OY, and there is a red stamp in the corner of most of the sheets, with handwriting for the GL specification, the thickness of the plywood and the number of plies. I think you will find the Roman numeral "II" to the left and the millimeter thickness and number of plies to the right.

The plywood is always made with alternating plies at ninety degrees to each other, so you will see a different color for each layer, but if you turn the sheet and look at the other sides, you will see that the light-dark-light pattern will change to dark-light-dark.

I once saw the specification for GL II plywood, and I don't remember much of what it said. I don't know for sure if it specifies that all layers are made of birch, but I think that's true. In any event, when you buy plywood from Finland, you can be very, very sure that they are making the plywood of their native birch and not importing mahogany from South America! Even when mahogany is used in plywood, it is typically only used on the outer plies, because it is so expensive.

Mahogany or birch plywood made in the US is typically made with the inner plies of poplar. But since we only use GL II birch, I haven't spent a lot of time weighing the merits of the various grades.

[ooby]

Door skins are availably locally at a Ma and Pa type lumberyard. I forget the width but think they come in 7ft lengths. They make great bulkhead material, and I've also used them on the EC-12 sail box.

[Tugboat Andy]

Door skins are availably locally at a Ma and Pa type lumberyard. I forget the width but think they come in 7ft lengths. They make great bulkhead material, and I've also used them on the EC-12 sail box.

Typically, a door skin is 3 x 7 feet. Available locally here in the PNW. I built a kayak out of doorskins year ago and it kept me safe of a few outings. ;)

[herrmill]

In China they use 3mm ply like we use 1/2" CDX for their mainstay building panels, so its easy to find anywhere in many different veneers for interior & exterior use. Cheap too at 30rmb/M2 ($0.40/sf). :D

I found this birch panel laying on our office balcony the other morning as a gift from one of the workers above us. It must have blown off their balcony in the storm we had over the weekend & will make a nice deck & casement for Tennessee, & maybe even enough for Canonicus' raft. :)

Chuck

[Aerominded]

Well, my Falco project has begun!

WHOA!!! Big project and a Neat plane! :)

T-88 will be your friend! I have done some wood work on antique planes and always thought a Fly Baby would be a fun project!

Best wishes for your Falco! :)

[seaphoto]

Hi Pat,

Most larger cities will have specialty lumber suppliers who can get all sorts of things you won't fnd at the local big box home store. If you can find a company that deals strickly in plywood that would be ideal, but you can often find quality plywood at hardwood dealers too. Sure the stuff is pricey, but when look at as a proportion of your project, it's not too bad. You can never go wrong buying quality materials.

Kurt

[Brooks]

Green boat, thanks for the informative post of plywood information, very helpful!

To find door skins: a) ask a non-chain lumber/builders supply store. b) look in the Yellowpages under "Doors". I'd say the biggest modeling problem with door skins is that the ones I have seen only have 3 plys. Modeler's plywood of the same 1/8" thickness has 5-7 plys, so I'd expect it to be more dimensionally stable. Door skins are meant to be fully supported by the underlying door core. Model bulkheads are meant to be free standing, so I'd be wary of using 3 ply for that task. But...I am sure that good craftsmanship and good waterproofing of the bulkheads will solve that potential problem.

re lite ply - a professional RC plane builder writes on his website that lite ply is much weaker than regular model ply, so he does not recommend it.

Plywood source - I was pleased by my order of thin plywood from these guys, who were recommended in another thread on this Forum:
http://www.nationalbalsa.com/hardwood-ply.htm

Just as professional-grade pool cues will warp if not stored properly, plywood will also warp if not stored properly. I lay my plywood flat (on the floor under the pool table, but I'm no professional, alas :-). Vertical storage (per cues) would be good if you had a way to keep the plywood bin full, or had adjustable bin sides to take up the free space.

[patmat2350]

Lite ply- Yes, I read what the airplane guy said, but I'm not convinced. Truth is, we don't need super-strength in our bulkheads, once the hull is built, because the hull shell itself is where the strength is. We just need the frames to stay flat during the build.
Example- just look at all the big Sterling CC's, Missouris, American Scouts- all built with plain balsa frames! I'd choose (flat) lite ply over balsa simply because it's not so likely to split or crush when being assembled.
But a design hint- Sterling always made interlocking frames and chine/sheer boards, so it was about impossible for the frames to move out of plane.

[Brooks]

Good point, Pat. I stand (straight) or lie (flat) corrected.