Each spline has to be designed for the intended use location. So you have to figure your thickness, width and length for every joint where you want to use a spline.
Once you have a list of lengths you can add them up to make one long piece. For example if you needed four 2' splines then buy one 8' piece of lumber.
Now you could use straight grain dry oak, dry wood is stronger.
So lets say you need some 6" wide splines that are 1 1/2" thick and 2' long.
You'd go to a local hardwood store or lumber yard and get some dry lumber in the rough, that is not planed. And plane them yourself. If you don't have a planer, then take the rough stock to a mill-work shop and have it planed. You can plane it down to 1 1/2" thick and then just hand plane the edges to insure that they are nearly 6" wide.
If you need to find a source for dry hardwood lumber in your area there are several ways on the internet to do that.
One is
Woodfinder.com , this is a search engine site where you enter the type of wood and your location and it will list all the wood dealers in your area that sell the type of wood you want to buy.
If there isn't any in your area, widen your search and find one that will ship to you.
There is also
WoodPlanet.com . This is also a site where you can find people who sell wood.
Also, you can look at
WoodWeb.com . There are lots of forums at this site and you could find someone there who can help you.
Another site is
ForestryForum.com . You can post your request for help on the "general" forum and someone there will help you find a dealer in your area.
On the home page of the Forestry Forum is a search engine called "Find a sawyer" and it will list all sawyers in your area who are users of the Forestry Forum and most of them can be contacted by email and of course it lists their phone numbers and you can call them up and see if they sell "kiln dried" wood.
You probably could use "air dried" wood as well, but dry wood, is stronger.
Good luck with your search, and your project.
Jim Rogers
