HMS K9. Prop & ShaftsMoving on from the Coffer (not coffin), the next fiddly bits are the prop shafts. These are designed for dog-bone couplings and imperial size shafts. Of necessity space is very tight due to having to fit the dive module as far aft as possible, and also results in the shafts being slightly angled to the motor couplings.
The outer shafts go through the hull, aimed to line up with the motor couplings then shortened to around 120 mm. “A” frames to be fitted at the rear. Rather than use a 1/8” dia shaft I am using 3 mm (for M3 shafts) with a thin coat of paint on the inside of the 1/8 coupling. Only 0,2 mm difference, but . . .
I was so impressed by Albion’s sliding telescopic square-tube shafts with internal springs, and am trying to replicate these. Dog-bones cut in half, the ends fitted with screws into the outermost square tubes. The slightly larger sliding tubes have stainless springs that maintain compression on the dog-bones, whilst allowing latitude for dive module removal. The entire shaft system is in the flooded part of the hull so will need to be cleaned and lubed regularly.
Getting suitable props took some time. After almost a week of calls and emails to Prop Shop I still had no response. The nearest non-custom I could find were Raboesch 4 bladed type “D”. Unfortunately Dean’s were out of stock, but I was able to order them from Cornwall Model Boats. … but a week lost !
While the props are on their way I thought I should start work on the hull perforations. Plenty around the keel, plus a series of rectangular ones along the hull. Not much visible on top apart from superstructure, so I need to ensure that there are enough elsewhere to prevent air being trapped especially at the bow and stern.