Working on old structures is not necessarily to be thought of in fundamental "new build" design terms but maybe thought more in terms of design evolution where some factors are fixed or constrained as in nature. All greenheart timbers leaving Guyana today are shipped inside 40 foot sea containers and it is this factor that now determines the basic raw building block dimensions for this mill. The new arms are to be made up as per the orginals at 68 feet long and this will be achieved by using two 40 foot timbers for each arm with one 40 foot clear span timber used in the central portion of the arm and the other 40 ft timber halved to provide 2 off x 20 foot timbers that will be then be scarved to either end of the central 40 footer.
If we do some simple arithmetic we can arive at the maximum scarf length possible i.e. 40 + (20 - 6) x 2 = 68.
It gets worse ! Piggy backed onto each side of the 68 foot arms are 41 ft whips which form the spines for the sails and these bring the fully assembled diameter of the sails up to 84 feet all of which is supported at one central point on the 2 foot diameter windshaft.
Some time back on this forum I asked if anyone could provide references to books that contained examples of metal reinforced scarf joints and both Gabel & Will T came up trumps in this respect and the knowledge contained within the pages of those reference books has been put to good use.
The method employed for scarfing is currently under development and so I am somewhat reluctant to discuss this here in an open forum. I am working with a millwright who has over 40 years experience in rebuilding windmills and the combination of experience, brain & computing power will doubtless arrive at an optimal solution given the current constraints. As with natural evolution adopting this design development step solution methodology will either work and the mill live on to crush another day or alternatively if it fails then this type of windpowered sugar cane crushing mill will become extinct.
This site can and does provide a potential powerhouse of knowledge.
