Fitting guttering to your cabin will benefit twofold :
So, you now have good reasons to install guttering to your cabin - please see our article here on fitting guttering to your log cabin.
In order for the water to run directly from the roof into the guttering, plan for this when fitting the felt shingles. When fitting the first row of starter / ridge tiles, over hang the eave (Roof board position 39b) by approximately 40mm (1.5") this will result in the tile edge dispelling the water straight into the gutter.