Stringer Material Order

[M Towsley]

A gentleman I know is getting an estimate from a company for wood stringer material. My understanding is it is not a common size so it must be custom made. If anyone is interested let me know as the price comes down the more people that are involved. He is waiting for a single order price at this time.

[Hank Jarrett]

Re: Stringer Material Order

I was planning to make mine for the 45 but if the price is right that is a LOT of setup and milling for one plane! What kind of wood and what profile is he going to make?

Hank

[Bigdog]

Re: Stringer Material Order

If it's the same profile for the L-2 then I'm in for 3 or 4 shipsets.

[M Towsley]

Re: Stringer Material Order

Hank, it is poplar and they have the profile.

Greg, someone with more knowledge, (like Mike Redpath), would have to answer that.

[Hank Jarrett]

Re: Stringer Material Order

Haven't worked with Poplar much. I have some in Spruce and they are not stiff enough. I considered making them from Doug Fir to get them stiffer. What is the word on Poplar? Any estimate on cost yet?

Hank

[M Towsley]

Re: Stringer Material Order

He is supposed to be contacted any day regarding the cost for one set. Multiple sets mean less money. Once I get a number of seriously interested owners I will let him know and he will check the price per set.

[Ragwing nut]

Re: Stringer Material Order

Hank, it is poplar and they have the profile.

Greg, someone with more knowledge, (like Mike Redpath), would have to answer that.

L-2 is a t-stringer, "B" is a flat stringer. Is it not just a 1/4" stock with a round over on the "B"? Any cabinet shop shop the able to make it, the issue is going to be shipping cost to get stock long enough and then have to double ship motor freight. I see this being expensive.

[astjp2]

Re: Stringer Material Order

I made my 41 "t" stringers out of doug fir, 5/16" thick and 1/2" wide at the top. They are not half round at the top, its just rounded corners. I used vertical grain, clear doug fir 2"x6"x14' and it took me several hours to find adequate wood in the pile that had 15 grains per inch with a slope of no more than 1 in 12". They were $156.00 for the two boards that met aircraft quality. Poplar is not strong enough in my opinion because the grain structure wont give you a clear board. Tim

[M Towsley]

Re: Stringer Material Order

Here is the cad drawing provided to me.

[Bigdog]

Re: Stringer Material Order

Here's the profile drawing used for the L-2's. I assume since the drawing number starts with a "B" its usage started with the B models. Note that the material is white pine. You're right, shipping could get spendy. I should be able to get it produced locally. So I guess I'm out.

[Hank Jarrett]

Re: Stringer Material Order

The L-2 drawings look a lot more like what I have from my 45. I wonder if they used left over L-2 parts on the first post was BC-12s?

Hank

[Mark Bowden]

Re: Stringer Material Order

Hi,

I might suggest that you specify a radius in the female 90 deg. corner where it is shown square. While the original drawing shows square, best practice says put as large as radius as can be accommodated on assembly. The tighter the corner, stress levels go way up and cracks will start here.

The tool will likely be 0.010 if you don't specify.

In terms of wood selection the Forest Service has long published their wood design handbook, predating the "aerospace" laminated composites use. Unfortunately metal airplanes made much of the industry forget this existed and it had to be expensively relearned.

you can down load it for free at this link: http://www.woodweb.com/Resources/woo...k_fpl_2010.pdf

Popular is heavy, and is a bit less stable/higher shrink numbers, no benefit for use.
As the L2 calls it out, tough to go wrong with White Pine. It just supports fabric shrink/light tailcone air-compression loads. And it's cheap, although digging through the pile of lumber to get good strips might be a pain these days.

Some property numbers for comparison from the handbook. Spruce is prized for consistent grain, low density and good compression and shear (prime composites design drivers). Its tough too.

[wmfife]

Re: Stringer Material Order

EAA Aircraft Building Techniques: WOOD, EAA How-To Series. Paul Poberezny, Comp. & Prepared, EAA Foundation, Pub 1994; Reprinted 1998. (See p. 9: "Characteristics, Sizes and Weights of Standard Plywoods.) Complete rundown on wood choices as aircraft building materials.

Refs. to Douglas Fir v Spruce are consistent with previous posts.

[astjp2]

Re: Stringer Material Order

I posted the actual documents for wood construction of aircraft assemblies in the references section...dry read though