I would reccomend you not cut a hatch in the top side as you will lost a lot of strength from cutting thos five stringers in that curved top.

If you want instead do a bottomside hatch I would suggest it be done like this airplane. In this case it is a Kaydet Senorita. Cut an inset hole not all the way accross from side to side only in the flat sheeting of the bottom and not accross any bulkheads, Only the bottom sheeting. This can be made quite large without loosing any strength, Important when using a somewhat larger and heavier engine. By the way a ninety fourstroke or a sixty two stroke in any Senior are just about ideal combinations.

After the cutout is made carefully with a razor saw simple edge sticks are glued along the edge and just inside of the cutout and provide a place for the hatch cover to lay and screw to when it is reinstalled.


John

I cut the top hatch with a knife and saw with little dammage to covering and as i was the one that built it from sticks 17 years ago and replaced the tank about 8 years ago it still flys well // the top formers are Balsa and when you put it back togather put a strip of balsa shetting as a backing on inside to screw or CA the hatch in place i used a Du-Bro 16oz tank and i CAed the hatch in place and put the plane thru the ringer with no trouble i feel the strengh is in the sides // this whole proscess takes less than 2hrs start to finish //good luck