There are many types of wood that can be used in constructing a proper airframe, as per AC-43.13b.

I happen to like northern white pine, which has nearly the same strength-to-weight ratio as spruce -- and better than that of Douglas fir. NWP is about 15 percent lighter and about 15 percent less strong than spruce, so if your plans specify spruce you will want to increase the dimensions by about 15 percent.

Buying aircraft-certified spruce is certainly the easy route, but it is expensive. I think the savings of selecting good lumber from a lumber yard are well worth the effort. In my area, the Great Lakes region, there is lots of good clear white pine. I can go to any number of lumber yards in the area and select excellent boards that will make lovely longerons, ribs, etc.

For a single-seat Minimax-type airplane, I could probably buy all the wood I need (excluding plywood) for about $100. If you buy certified wood you will pay ten times as much, plus shipping. I don't think that's insignificant. For a two-seat airplane the total cost of lumber and plywood can easily exceed a couple of thousand dollars. Using alternative wood sources you can get started on building the airframe with a minimum layout up front -- if you find that building an airplane is not for you, you will not have paid a lot of money to learn that lesson.

Plywood is a similar story. I can buy excellent Lloyd's approved okoume ply at a marine supplier for a fraction of what I would pay for certified aricraft birch ply. In fact I have more faith in marine ply becasue there is a robust market for it worldwide. Aircrft ply is a nearly extinct market -- it is the lowest priority for the plywood manufacturers, so not much attention is paid to how good the product actually is.



What is really important is to learn as much as you can about wood and how to grade it, in order to properly select lumber from a pile (or plywood for that matter). There are a number of good sources of info, including chapter one of AC-43.13b. Ther are many more source of info, including a good littel book from the EAA.

Once you have selected your lumber it is important to know how to work it and glue it. You have to develop an understanding of grain and how best to orient it. End grain will soak up a lot of glue, for example; yet most of the joints on wood airframes are end-grain butted against face grain.



Also, since most of the lumber you will find at the lumberyard is flat-sawn, you will not be able to use such boards where the plans call for quarter-sawn, such as in solid-plank wing spars. However, you can laminate your spars from several pieces of 1x1 with the grain oriented the correct way. (If you cut a flat sawn 1x6 board into six pieces of 1x1s, you will have the same thing as quarter sawn wood and can use it for longerons, stringers, rib stock, etc.)

Scarfing is another issue that has its subleties.

So you see just buying aircraft-certified wood is no guarantee of a properly constructed wood airframe. It is simply assurance that the wood has been graded properly, which is something you can do yourself at a lumberyard if you learn how.

There is much skill in building with wood, as can be seen in wooden boat building. A good boatbuilder will build a lovely craft from a pile of floorboards salvaged from a an old farmhouse, while others will not do nearly as well even with the best materials money can buy.

When it comes to working with wood, there is no sbustitute for knowledge.

Regards,

Gordon Arnaut.





"Stewart Glenn" wrote in message om...
I'm looking to start a home built aircraft. Does anyone have any suggestions on which type of lumber to use that's a good alternative for sitka spruce?

Thanks