I meant to add- Sitka is probably near impossible to find in Spain. Douglas fir can be substituted but inspect your stock VERY CAREFULLY for...
Robert miller is correct- mostly. "Any length" is not the way to go- use the longest lengths you can find. Use equal lengths throughout. Land all...
Voids in exterior grade plywood will speed rot and worse- delamination. The investment you will make(time and money) in a boat of the size you...